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Pisha sandstone is a soft bedrock composed of sandstone, sand shale and mudstone, with very low diagenesis and erosion resistance. The sources of coarse sediment and the processes of sediment production and transportation in Pisha sandstone areas are currently little understood. Understanding these processes will help us to comprehend the characteristics of sediment particle size distribution on slopes and gullies under the effects of vegetation and complex erosion. This will provide a scientific basis for the control of coarse sediments of the Yellow River and ecological restoration of the Pisha sandstone area. In this study, the process of sediment selectivity and transportation in the slope–gully system was analyzed through soil sampling in different seasons in the Erlaohugou small watershed, China. There is a clear selectivity phenomenon in the process of transporting sediment particles from the slope to the gully, and the coarse sediment particles are transported preferentially from the slope to the gully. There is a good response relationship between the distribution characteristics of sediment particles and the multi‐dynamic interaction. The complex erosion type in different seasons has a significant impact on sediment production and transportation, and most particles were transported under hydraulic power. [ABSTRACT FROM AUTHOR]

Background: Studying plant–soil feedback (PSF) is of great significance to understanding plant community dynamics. Aims: We aimed to determine the temporal variation in PSF at different stages of grassland community succession and the influencing factors. Methods: We conducted a 3‐year experiment to examine how PSF changes during different successional stages (early‐, mid‐ and late‐). Setaria viridis, Stipa bungeana and Bothriochloa ischaemum were selected as representative and dominant early‐, mid‐ and late‐species, respectively, in the semiarid grassland of the Loess Plateau, China. Results: The temporal variation in the PSF pattern was found to be species‐specific. Negative and neutral PSF patterns in early‐ and mid‐species, respectively, were found within the 3‐year growth periods. A positive PSF pattern for late‐species was found in the second growth period, and a negative PSF pattern was found in the third growth period. The shoot biomass of early‐species was overall positively correlated with soil nutrients and enzyme activity in the soil of the three species. However, the shoot biomass of late‐species was overall negatively correlated with soil nutrients and enzyme activity in early‐species soil. Conclusions: We suggest that the negative PSF of early‐species over the growing period explains why the advantage of these early colonizers is temporary. In contrast, the positive PSF of late‐species likely contributes to their successful colonization and the entire community succession process. Our results indicated that PSF plays an important role in the progression of plant community succession. [ABSTRACT FROM AUTHOR]

Purpose: A general understanding of the influence of different plant species on soil quality improvement under drought stress is vital for planning the restoration of degraded land resources, especially in the context of global warming. Methods: In this pot study, we planted Setaria viridis, Stipa bungeana, and Bothriochloa ischaemum, which are typical grass species on abandoned farmland, succeeded by grassland, in the Loess Plateau of China, under optimal soil water conditions and under water deficit (i.e., 80% and 60% of soil field capacity, respectively). Rhizosphere soil samples of the three grass species were collected after 76 days of growth, and 21 soil properties were determined as potential indicators of soil quality. Four rhizosphere soil quality indices (SQI) were computed using linear/nonlinear scoring functions and additive/weighted additive methods by the selected minimum dataset (MDS). Results: L-leucine aminopeptidase, cellobiohydrolase, phenol oxidase, total phosphorus, available phosphorus, nitrate nitrogen, water-soluble nitrate nitrogen, and water-soluble ammonium nitrogen constituted the MDS for SQI calculation. The nonlinear weighted additive index best discriminated the effects of grass species under drought stress. Rhizosphere SQI did not significantly differ among the three grass species under optimal water conditions, but drought stress exerted a positive effect on rhizosphere SQI, which was significant for S. viridis. Conclusion: Short-term drought stress increased rhizosphere SQI, especially at the preliminary succession stages. Furthermore, the relatively stable rhizosphere SQI of plant species at the later-successional stages suggests that the later-successional plant species resisted drought stress better; this aspect warrants further investigation. [ABSTRACT FROM AUTHOR]

Microbes play an essential role in soil biogeochemical processes and maintenance of soil nutrients, but not all microbial taxa contribute equally, and their functions in soil nutrient cycling and microbial network stability are unclear in arid fertigation agricultural ecosystems.In this study, a 4‐year field experiment was conducted in an irrigation district in China using three levels of irrigation [high (400 mm), medium (300 mm) and low (200 mm)] and two levels of fertilization [high (600 kg/ha P2O5 + 300 kg/ha urea) and low (300 kg/ha P2O5 + 150 kg/ha urea)] to reveal the ecological roles of core and noncore taxa in maintaining soil nutrient cycling and their associations with microbial network stability.Our results showed that combining medium irrigation with low fertilization resulted in higher levels of soil organic C, inorganic N, available P, multinutrient cycling and noncore bacterial diversity compared with the other treatments. Soils supporting a higher diversity of noncore bacterial taxa had a high soil multinutrient cycling index, while soils harbouring highly diverse core taxa exhibited a more stable bacterial network. The soil multinutrient cycling index was also significantly positively related to the subnetwork modularity of noncore taxa. Moreover, noncore taxa could serve as diverse pools that turn into core taxa in response to changes in the external environment. Acinetobacter, Flavobacterium, Gemmatimonas and Salinimicrobium, which belong to the noncore taxa, were involved in soil C and N cycling in the arid agricultural ecosystem.Synthesis and applications. Our results suggest that soil microbiota contribute differently to ecosystem functions. Changes in soil nutrient cycling were more closely related to variations in noncore taxa, while bacterial network stability was more associated with core taxa. Our study emphasized the role of noncore microbiota, which has been neglected in previous studies. Furthermore, our findings suggested that combining medium irrigation with low fertilization is effective for enhancing soil nutrients and bacterial diversity, providing guidance for managing arid agricultural ecosystems. [ABSTRACT FROM AUTHOR]

Venlafaxine (VEN), a first‐line antidepressant, and Zuojin Pill (ZJP), a common herbal medicine consisting of Rhizoma Coptidis and Fructus Evodiae, are high likely co‐administered in China. ZJP could significantly inhibit VEN pharmacokinetics in vitro and in rats through suppression of CYP2D6 activity. To date, however, no clinical study has demonstrated the clinical relevance. Here, the VEN pharmacokinetics at a single dose of VEN with or without co‐administration of ZJP was compared. ZJP had a weak herb–drug interactions (HDI) on the pharmacokinetics of VEN. The geometric means of Cmax and AUC0‐∞ of VEN increased by 36.7% and 34.6%, respectively, and the corresponding 90% confidence intervals (CIs) of geometric mean ratios (GMRs) exceed outside bioequivalent range of 0.80–1.25. However, the corresponding 90% CIs of GMRs of these parameters for ODV were within the range. Since ODV exposure (AUC), approximately 3.4‐fold higher than that of VEN, hardly changed, the systemic exposure of VEN active moiety (VEN + ODV) with ZJP increased slightly (≤8.5%) compared with that of VEN alone. In addition, the incidence of VEN‐related side effects, especially gastrointestinal relevance, was significantly reduced with ZJP. Therefore, rational concomitant use of VEN and ZJP might have low risk of HDI and be promising in clinical practice. [ABSTRACT FROM AUTHOR]

Aims: Nitrogen (N) fertilizer is applied to the soil to increase the nutrient level and plant productivity, but the effects of N addition on the soil microbial community diversity and functions are unclear. This study aimed to determine how changes in soil N influence soil microbial community diversity and potential functions. Methods: We evaluated plant characteristics, soil chemical properties, microbial composition, and potential functions (N-fixation and functional fungal guild) after 3 years of urea fertilization at four different levels (0, 25, 50, and 100 kg N ha−1 year−1) in a semiarid grassland in China. Compositions of bacterial and fungal communities were determined by high-throughput sequencing, and their potential functions were predicted by comparing their data with those in the Tax4Fun and FUNGuild databases, respectively. Results: Compared with the grassland without N input (N0), N fertilization significantly reduced soil bacterial diversity, possibly by reducing plant diversity. Fungal diversity increased with N fertilization and peaked in the N50 treatment, while the aboveground biomass showed a parallel increase and peak. A lower abundance of nif genes was found in the N100 than in the N0 treatment because the enhanced NO3− and NH4+ content alleviated the dependence of plants on biological N-fixation and reduced the N-fixation potential. N fertilization increased the relative abundance of saprotrophs (wood, plant, and dung saprotrophs) and pathogens (plant and animal pathogens). However, this promotion could be weakened when the excessive N fertilization was applied due to the lower abundance in the N100 than in the N50 treatment, and these changes could be attributed to the variation in aboveground biomass and soil organic C. Changes in the abundance of arbuscular mycorrhizal fungi were related to their host plants, exhibiting a transient increase in the N25 compared to the N0 treatment and then sharply decreasing. Conclusions: Our results show that N-induced environmental changes have considerable influence on the composition and potential functions of soil bacterial and fungal communities, which are likely to be dependent on interactions between plants and soil. [ABSTRACT FROM AUTHOR]

Irrigation and fertilization practices can improve crop productivity in agroecosystems; however, the role of soil biodiversity in regulating crop production is not well understood. This restricts our ability to understand how changes in soil biodiversity impact soil function and crop productivity. To address this, a 4-year field experiment was conducted in China using three levels of irrigation [high (400 mm), medium (300 mm), and low (200 mm)] and two levels of fertilization [high (600 kg/ha P2O5 + 300 kg/ha urea) and low (300 kg/ha P2O5 + 150 kg/ha urea)] in arid farmland, to investigate maize production, soil properties, bacterial and fungal communities (diversity, compositions, N-cycling potentials, and co-occurrence networks), and their associations. The results showed that irrigation and fertilization had significant effects on bacterial and fungal community diversity, N-cycling potentials, and co-occurrence network patterns during maize growth. The combined treatment of medium irrigation and low fertilization resulted in higher maize yields, bacterial diversity, nitrification, ammoxidation, N-fixation potentials, and network modularity, compared with the other treatments. Strong and positive associations were observed between the soil N-cycling potentials, maize yields, and bacterial diversity; soils supporting a large number of bacterial taxa with co-occurrence network modularity had high soil nutrient levels (organic C and inorganic N) and maize yields. Structural equation modeling demonstrated that bacteria exhibited higher contribution to soil fertility and maize yields than fungi, and irrigation and fertilization indirectly affected microbial functions by altering bacterial diversity and network modularization, which also affected soil fertility and maize yields. These results highlight the importance of microbial diversity and their co-occurrence networks for maintaining soil fertility and crop production and will improve future irrigation and fertilization practices in arid agroecosystems and provide guidance for sustainable crop production. [ABSTRACT FROM AUTHOR]

As the largest conservation program and payments for ecosystem services in China, the grain-for-green program (GGP) has substantially changed land use and cover, and reduced soil erosion in participating areas. However, whether the GGP enhances participants' livelihoods still lacks robust evidence. Based on the sustainable livelihood framework, the objectives of this work is to understand how livelihood capitals of participants changed and to examine which factors influenced participants' livelihood activities and land use choices and to what extent before and after implementing the program. We found that despite a significant reduction in arable land area per capita, the GGP dose indeed do no harm to participants' lives. In contrast, through key forces such as savings and debt, income diversity, education and health, transportation, and off-farm job opportunities, participants in the program have switched livelihood activities dominated by subsistence farming into off-farm activities such as migrant labor and rural business or high market-oriented horticulture/orchard farming. Transportation, education, health and off-farm work opportunities, income are key factors affecting livelihood activities. Besides, sustained and sound subsidies would contribute to improving participants' livelihoods. [ABSTRACT FROM AUTHOR]

Background and aims: Afforestation is considered one important means of mitigating climate change. However, it is still controversial whether mixed-species plantations (MP) were more conducive to the soil organic carbon (SOC) stocks than monoculture plantations (PP). Methods: We conducted a meta-analysis based on 21 publications to assess the effects of different afforestation modes as well as controlling factors of SOC stocks on the Loess Plateau of China. Results: Compared with monoculture plantations, mixed-species plantations could significantly increase the response size of SOC stocks by 28%. For different species combinations, tree-shrub mixtures were more conducive to increasing the SOC stocks. In climate-limited regions (MAT <8 °C, MAP <500 mm), the response size of SOC stocks of mixed-species plantations was 34% higher than that of monoculture plantations. Furthermore, significant differences were found in the response size of SOC stocks at young (< 10 yr) and mature stages (> 20 yr). Compared with abandoned land, afforestation on cropland, especially mixed-species plantations, could increase the SOC stocks by 10%. Additionally, compared with monoculture plantations, a stronger coupling relationship was observed between the soil total nitrogen (STN) and SOC stocks in mixed-species plantations. Conclusion: Our results suggest that for the Loess Plateau of China, planting mixed-species plantations containing nitrogen-fixing plants is a more effective approach to enhancing the SOC stocks than monoculture plantations. [ABSTRACT FROM AUTHOR]

Soil ecoenzymatic stoichiometry reflects the nutrient flow of ecosystems. While knowledge exists on how the secondary succession of plants affects soil physicochemical properties and soil ecoenzymatic activity, less is known about how soil ecoenzymatics change during this process. We investigated five typical stages of the entire succession process of vegetation on the Loess Plateau, China. These stages included: (1) farmland stage (0 years), (2) grassland stage (30 years), (3) shrub land stage (60 years), (4) the pioneer forest stage (100 years), (5) the climax community stage (160 years). Soil ecoenzymatic activity, microbial biomass, and soil physicochemical properties were measured. Our research showed secondary succession significantly changed soil enzyme activity, and the metabolic activity of soil microorganisms significantly declines as secondary succession progresses. N limitation in the soil microbial community was weak initially and then gained strength. P nutrient limitation was strong initially, and then weakened. Soil ecoenzymatic C : N : P acquisition ratios deviated from 1 : 1 : 1. Thus, secondary succession on the Loess Plateau is nutrient dependent, but not homeostatic. Soil physicochemical properties and plants were important factors for soil enzyme activities. In addition, soil available nutrients were better than soil total nutrients to reveal changes in soil ecoenzymatic activities and stoichiometry. This study demonstrated the regularity of soil nutrient cycling during the secondary succession of vegetation, providing new insights on the mechanisms of nutrient flow. [ABSTRACT FROM AUTHOR]

Slope aspect is an important topographic factor for a micro-ecosystem environment that may affect macro- and micronutrients in plants and soil. The south-, northwest-, and north-facing slopes were selected to investigate the influence of slope aspect on the concentrations, storage, and allocation of macro- and micronutrients in Artemisia sacrorum on the Loess Plateau in China. The concentrations of available manganese (Mn) in both rhizosphere and non-rhizosphere soils reached their maximum on the north-facing slope. The concentrations of available iron (Fe) in rhizosphere soil and available copper (Cu) in non-rhizosphere soil reached their maximum on the south-facing slope. Slope aspect significantly affected the total concentrations of potassium (K), calcium (Ca), magnesium (Mg), Cu, and Mn in rhizosphere and non-rhizosphere soils, and all of these elements reached their maximum on the northwest-facing slope. Slope aspect significantly influenced the concentrations of aboveground K, Ca, and Mg, sodium (Na), Mn, and belowground K in A. sacrorum, and the concentrations of aboveground K, Ca, Mg, and Na and belowground Mn, Na, Fe, Ca, and Mg in weed. Most elements in A. sacrorum and the weeds reached their maximum on the south-facing slope. Slope aspect significantly changed the aboveground-to-belowground concentration ratios of K, Ca, and Na in A. sacrorum and weed. Slope aspect significantly affected the storage of macro- and micronutrients in A. sacrorum and weed but not the storage in the plants of the entire plot. Slope aspect predominantly affected the storage allocation of macro- and micronutrients in A. sacrorum but not those in weed. Slope aspect is an important topographic factor that affects the macro- and micronutrients in plants and soil in micro-ecosystem environments. [ABSTRACT FROM AUTHOR]

Determining changes in grassland ecosystem carbon (C) storage and soil C stability after cropland abandonment is important for estimating the regional C budget and global C cycle. However, the understanding of ecosystem C storage and allocation and soil C stability along the grassland restoration chronosequence is insufficient. Thus, grasslands with different recovery years (0, 2, 5, 8, 11, 15, 18, 26, and 30 years) were chosen to monitor the dynamics of grassland ecosystem C storage, vegetation biomass C storage, soil C storage, and soil C stability in different soil depths, as well as a natural grassland (NG) reference. The results showed that aboveground biomass (AGB), belowground biomass (BGB), soil C storage, ecosystem C storage, the very labile fraction of oxidizable C (C1) (0–0.3 m layers), the labile fraction of oxidizable C (C2) (0–0.3 m layers), and the C management index increased with the recovery years. The vegetation species richness (R), vegetation species evenness (E), and vegetation species diversity (H′) initially increased, peaking at 18a and then decreasing with recovery years, but the soil C stability index (SI) at 0–0.3 m decreased over time. Additionally, the AGB, BGB, litter biomass (LB), R, H′, ecosystem C storage, and SI (0–0.3 m and 0.5–1.0 m layers) of 30‐year grassland (GL30) showed no significant differences relative to those found in the NG. Furthermore, the soil C sequestration rate decreased with decreasing soil depth, while the soil C stability increased. These results suggest an optimistic outlook for the recovery of ecosystem C, but the soil C under these conditions is unstable, posing a risk to soil C sequestration in abandoned cropland on the Loess Plateau without appropriate management. [ABSTRACT FROM AUTHOR]

Vegetation restoration is widely recognized as a way to improve soil organic carbon (SOC) stock. However, whether these recovered carbons are stable is yet largely uncertain. Thus, we determined the sequestration and stability of SOC in soils with three different types (Caragana korshinskii (CA) aged for 10, 20, 36, and 47 years, Hippophae rhamnoides (HR) aged for 5, 10, 20, and 30 years, and Robinia pseudoacacia (RP) aged for 5, 10, 20, 37, and 56 years) to compare their SOC sequestration and stability in different depths in this study. The SOC content, SOC stock, very labile fraction of oxidizable carbon (C1), labile fraction of oxidizable carbon (C2), and carbon management index (CMI) in 0–30 cm depths of the three types increased over the chronosequence. The SOC stocks increased by 1.40–3.19 Mg ha−1 in CA during the 47‐year restoration, by 5.76–10.01 Mg ha−1 in HR during the 30‐year restoration and by 1.88–8.93 Mg ha−1 in RP during the 56‐year restoration, respectively, in 0–30 cm depths. The carbon stability index (SI) in 0–10 cm depth of CA, 0–30 cm depths of HR, and 0–50 cm depths of RP decreased with recovery time. Over the recovery time, SOC content, SOC stock, CMI, and SI were lower than those of nature forest (NF aged more than 100 years) in all restored sites at the later stage of recovery. SOC sequestration decreased, but its stability increased, with the soil depths. Overall, HR had a higher SOC sequestration rate and lower SI (0–30 cm) than CA and RP. Our results revealed that although the SOC sequestration appears enhanced over the restoration, but the SOC stability becomes lower, so that the recovery of these site to the level of NF may meet difficulties in this semiarid Loess Hilly Region. [ABSTRACT FROM AUTHOR]

Valuation of environmental goods and services are frequently spatially heterogeneous, the significance of this heterogeneity for policy analysis is gradually recognized. For the valuation of environmental goods and services in the context of attaining a better environmental status across Heihe River basin (HRB), Northwest of China by 2020, a survey was conducted employing choice experiment approach across the entire river basin. In this research we estimate the impact of distance from inland rivers' origin (spatial attribute) on the inhabitants' willingness to pay for restoration of ecological attributes. A total of 11 ecological attributes were selected including 6 land related attributes and 5 water related attributes. The present study displays the outcomes of the research planned to examine differences in willingness to pay across different locations/distances. A total of five cities and 33 surround villages/townships were included to examine for location effect, while four ad hoc base distances split samples were recognized for distance effect i.e. ≤100 km, ≤200 km, ≤300 and > 300 km from rivers' origin. The results of mixed logit model recognized that people living at different locations value the attributes differently. For instance the people of Zhangye region are willing to pay RMB 95.66 annually for improvements in biodiversity while in Gaotai the individuals' willingness to pay (WTP) for the same attributes was RMB 45.68. Similarly, the respondents' living nearer to the origin of river were willing to pay relatively higher amount for the upgradation in the degraded ecosystem services than the remainders. The results of willingness to pay obtained by Krinsky Robb method confirmed that the attributes quality of agricultural products and water quality were the most preferred attributes with the willingness to pay RMB 91.09 and 122.89 respectively. The significant results of willingness to pay may serve as a reference for sustainable improvements and uplifting of the degraded ecological attributes. [ABSTRACT FROM AUTHOR]

In this study, changes in plant diversity and aboveground biomass, soil chemical properties, microbial biomass and respiration, microbial composition, and microbial N-cycling potential (represented by the abundance of genes involved in N reaction) were studied after 3 years of urea fertilization (0, 25, 50, and 100 kg N ha−1 year−1) in a semiarid grassland in China. The microbial composition and N-cycling genes were determined using metagenome sequencing. Urea fertilization significantly decreased soil bacterial diversity, possibly through its negative effect on plant diversity, whereas it increased fungal diversity, and microbial biomass and respiration through enhancing aboveground biomass production with increases in the C input into the soil. However, above the threshold N rate of 50 kg N ha−1 year−1, microbial biomass and respiration decreased probably because of a strong N inhibitory effect on aboveground biomass. Further, urea fertilization increased the gene abundances of narH, nrfA, nirB, and napA, which are involved in dissimilatory nitrate reduction, and those of nifH and nifD, involved in N2 fixation, gdh, involved in organic N decomposition, and glnA, involved in glutamine synthesis and ureC. These findings suggested that urea addition has a positive effect on N-turnover potential. Burkholderiales and Rhizobiales play an important role in soil N cycling. Changes in plant community (diversity and biomass) were responsible for the shift in microbial diversity, biomass, and respiration, whereas alterations in inorganic N levels (exchangeable NH4+ and NO3−) potentially affected microbial N cycling. Our results show that N-mediated environmental stresses can play an important role in microbial diversity and functions, which appear to be mediated largely by plant-soil interactions. [ABSTRACT FROM AUTHOR]

Purpose: The main objective of the present study was to investigate the effects of cropland abandonment on soil erodibility as measured by soil resistance to concentrated flow and sediment yield. Materials and methods: Through the method of space-for-time substitution, undisturbed soil samples were collected at depths of 0-15 and 15-30 cm in the fields of different abandonment stages (including cropland for control, about 10 years for juvenile abandonment stage, 20 years for intermediate abandonment stage and 30 years for mature abandonment stage). Laboratory experiments simulating concentrated flow were conducted with a flume (200 cm long, 10 cm wide and 5 cm deep) to investigate soil resistance to concentrated flow and sediment yield. Soil physical properties (bulk density, porosity, aggregation, mean weight diameter, shear strength and disintegration rate) were measured. After each scouring test, roots were collected and root characteristics were measured. Results and discussion: Compared with control, soil resistance to concentrated flow increased following cropland abandonment. For the upper (0 to 15 cm) soil layers, the increments of soil resistance to concentrated flow ranged from 5.0 times in the juvenile stage to 9.9 times in the intermediate stage, and it dropped to 2.5 times in the mature stage. For the lower (15 to 30 cm) soil layers, it increased from 1.3 times in the juvenile stage to 2.1 times in the intermediate stage, and it reached up to 4.1 times in the mature stage. In comparison with the total sediment yields of control, 66.0 and 49.3% reductions were averagely observed in the upper and lower soil layers of the abandoned soils, respectively. The increasing soil resistance to concentrated flow indicated the decreasing sediment available for scouring and this observation may largely be attributed to the ameliorated aggregation, shear strength, disintegration rate and the extended dense root network following cropland abandonment. Conclusions: Laboratory experiments simulating concentrated flow showed that, within 33 years of cropland abandonment, sediment yields greatly reduced and soil resistance to concentrated flow increased constantly and significantly. Soil aggregate, shear strength, soil disintegration rate and root surface area density were determined to be the key factors in the strengthening of soil resistance to concentrated flow on the abandoned cropland in the hilly Loess Plateau. [ABSTRACT FROM AUTHOR]

• Secondary vegetation succession changed AM fungi and nifH -expressing bacteria communities. • Opposite trends in diversity were observed between taxa across successional stages. • AMF community changed significantly during the later succession, while the nifH bacteria tended to be stable. • Interactions are initially cooperative, switching to competitive during succession. Arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria (expressing the nifH gene) play an important role in maintaining plant growth and soil function, and the reconstruction and restoration of vegetation and degraded ecosystems should focus on these communities and the links between them. However, little is known about changes in these taxa and their interactions during the natural recovery of abandoned land. Here, we investigated the changes in and interactions between AMF and nifH gene-expressing bacteria in farmland (S1), grassland (S2), shrubland (S3), pioneer forests (S4), and climax forests (S5) as five typical stages of vegetation succession on the Loess Plateau, China. We found that vegetation succession significantly influenced the diversity of AMF and nifH communities. With the progression of secondary succession, the diversity of AMF increased from farmland to pioneer forest communities, and decreased in the climax vegetation, while the diversity of the nifH community first decreased and then gradually increased. The community structures of the AMF and nifH communities differed significantly between the five vegetation types. Specifically, the AMF community structure changed significantly during the later stages of succession, while the N-fixing bacteria community tended to be stable during late succession. The interactions between AMF and nifH bacteria gradually increased from the farmland to shrub stages but tended to weaken from the shrub to climax forest stages. Therefore, the relationships between microbial communities during the early and middle stages of vegetation succession following land abandonment on the Loess Plateau are mainly cooperative and mutually beneficial, while competition likely intensifies during later successional stages. Furthermore, we found that soil microbial biomass, enzyme activity, and total phosphorus content were the main drivers of microbial community changes. Overall, this study complements current understanding of the changes and interrelationships of AMF and N-fixing bacteria during vegetation succession in areas prone to soil erosion, and provides new insights into the natural recovery of degraded ecosystems as driven by soil microbial communities. [ABSTRACT FROM AUTHOR]

The effects of reforestation on carbon (C) sequestration in China's Loess Plateau ecosystem have attracted much research attention in recent years. Black locust trees ( Robinia pseudoacacia L.) are valued for their important use in reforestation and water and soil conservation efforts. This forest type is widespread across the Loess Plateau, and must be an essential component of any planning for C sequestration efforts in this fragile ecological region. The long-term effects of stand age on C accumulation and allocation after reforestation remains uncertain. We examined an age-sequence of black locust forest (5, 9, 20, 30, 38, and 56 yr since planting) on the Loess Plateau to evaluate C accumulation and allocation in plants (trees, shrubs, herbages, and leaf litter) and soil (0-100 cm). Allometric equations were developed for estimating the biomass of tree components (leaf, branch, stem without bark, bark and root) with a destructive sampling method. Our results demonstrated that black locust forest ecosystem accumulated C constantly, from 31.42 Mg C/ ha (1 Mg = 10 g) at 5 yr to 79.44 Mg C/ha at 38 yr. At the 'old forest' stage (38 to 56 yr), the amount of C in plant biomass significantly decreased (from 45.32 to 34.52 Mg C/ha) due to the high mortality of trees. However, old forest was able to accumulate C continuously in soil (from 33.66 to 41.00 Mg C/ha). The C in shrub biomass increased with stand age, while the C stock in the herbage layer and leaf litter was age-independent. Reforestation resulted in C re-allocation in the forest soil. The topsoil (0-20 cm) C stock increased constantly with stand age. However, C storage in sub-top soil, in the 20-30, 30-50, 50-100, and 20-100 cm layers, was age-independent. These results suggest that succession, as a temporal factor, plays a key role in C accumulation and re-allocation in black locust forests and also in regional C dynamics in vegetation. [ABSTRACT FROM AUTHOR]

Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L. (alfalfa) grassland biomass carbon and soil organic carbon density (SOCD) in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period (viz. 0-10 year). Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m and 12.578 ± 0.863 kg/m. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m. Moreover, the ecosystem carbon density for abandoned grassland became 12.62 ± 0.50 kg/m at 30 years. The carbon density of the grassland undisturbed for 10 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general. [ABSTRACT FROM AUTHOR]

Comprehensively understanding water consumption behavior is necessary to design efficient and effective water use strategies. Despite global efforts to identify the factors that affect domestic water consumption, those related to domestic water use in rural regions have not been sufficiently studied, particularly in villages that have gained access to improved water supply. To address this gap, we investigated 247 households in eight villages in the Wei River Basin where three types of improved water supply systems are implemented. Results show that domestic water consumption in liters per capita per day was significantly correlated with water supply pattern and vegetable garden area, and significantly negatively correlated with family size and age of household head. Traditional hygiene habits, use of water appliances, and preference for vegetable gardening remain dominant behaviors in the villages with access to improved water supply. Future studies on rural domestic water consumption should pay more attention to user lifestyles (water appliance usage habits, outdoor water use) and cultural backgrounds (age, education). [ABSTRACT FROM AUTHOR]

Highlights: [•] We identify current water uses, conservation practices, motivations, and barriers to water conservation. [•] A total of 20 conservation practices were reported by of which 11 were adopted by the majority of residents. [•] Low consumption groups were likely to conserve water due to economic concerns, whereas high consumption groups were driven by environmental concerns. [•] Additional time and physical energy required, unwillingness to change their lifestyle, and lacks of social support were the barriers for respondents to conserve water. [ABSTRACT FROM AUTHOR]

Biological soil crusts (BSCs) perform essential ecosystem functions in arid and semi-arid ecosystems worldwide. The formation, development, and distribution of BSCs are influenced by changes in multiple environmental factors, including changes in the vascular plant community. The influence of changes in vegetation factors on BSC cover in 8-, 12-, and 16-year-old rehabilitated grasslands were studied in the hilly area of the Chinese Loess Plateau. The rate of degradation of BSCs underneath litter ( P < 0.01) and the degradation cover of BSCs ( P < 0.05) differed significantly between the 8- and 16-year-old successions. Stepwise multiple linear regression analysis showed that the main vegetation factors influencing the dynamics of BSC cover differed among the 8-, 12-, and 16-year-old rehabilitated grasslands. Basal cover, phytomass, and litter cover were the main vegetation factors influencing the dynamics of BSC cover on 8-year-old rehabilitated grassland. Phytomass, litter thickness, and litter cover were the main factors influencing the dynamics of BSC cover on 12-year-old rehabilitated grassland. On 16-year-old rehabilitated grassland, Pielou evenness index, litter thickness, and litter biomass were the main vegetation factors influencing degradation of BSC cover underneath litter, whereas basal cover, litter thickness, and litter biomass were the main vegetation factors influencing the degradation cover of BSCs. At particular stages of herbaceous succession, vegetation factors can have a large influence on changes in the community's basal cover and litter, which are key factors influencing changes in BSC cover. The degradation of BSCs underneath litter may be a result of complicated eco-physiological processes. [ABSTRACT FROM AUTHOR]

Abstract: Soil organic carbon (SOC) is an important component of agricultural soil. Understanding the storage of carbon (C) and nitrogen (N) helps us understand how ecosystems would respond to natural and anthropogenic disturbances under different management strategies. Although the quantity of SOC stocks in the Loess Plateau has been previously investigated, the distribution and storage of C in its deep soil layers has been poorly studied to date. The present study was conducted in the Zhifanggou Watershed on the Loess Plateau to evaluate the effect of the types of land use on the distribution and storage of SOC and total nitrogen (TN) at different soil depths. Ten types of land use were investigated: woodland (Robinia pseudoacacia), shrubland (Caragana korshinskii; Hippophae rhamnoides), natural grassland, artificial grassland (Medicago sativa), orchard, check-dam cropland, terraced cropland (Setaria italica; Zea mays), and sloped cropland. The results show that land use significantly affects the SOC and TN content. The reconversion of sloped croplands into forestlands and grasslands improve their SOC and TN content. Natural grassland, terraced cropland with Z. mays, and the artificial grassland had the highest SOC content within 0–60 cm, 60–100 cm, and 150–500 cm layers, respectively. The SOC and TN content in the top layer were higher than those in the deep layer. Natural grassland had the highest SOC and TN storage within 0–40 cm layer, followed by shrubland I (C. korshinskii), check-dam cropland, woodland, and shrubland II (H. rhamnoides), orchard and artificial grassland, whereas the sloped cropland, and the terraced cropland with S. italica had the lowest values. The SOC and TN storage between the top (0–20 cm) and deep layers (0–100 cm, 0–300 cm, and 0–500 cm) can be modeled using linear function (y = ax + b). The results suggest that natural grasslands may be the optimal choice for SOC and TN sequestration in the Zhifanggou Watershed. Shrublands, woodland, artificial grasslands, orchards, terrace cropland with Z. mays and check-dam croplands are also recommended for their great contribution to SOC and TN storage in the area. [Copyright &y& Elsevier]

Evaluating the sustainability of a target region for an ecological restoration programme is challenging because it involves different aspects of human society and environment as well as multiple disciplines. Carrying capacity provides a useful measure of the sustainability of a given region where an ecological restoration programme is implemented. In this article, the Yangou catchment, a geomorphic unit, was used as a case study in the Loess Hilly Region of China, where emergy synthesis was used to measure the environmental resources base. The specific standard of living in terms of emergy was employed to calculate carrying capacity over the period 1998–2005 and to assess the sustainability of the Yangou catchment where an ecological restoration programme was carried out. The results of the evaluation indicated that after implementing the ecological restoration programme, there was some improvement in the environmental aspects of the Yangou catchment during the study period, suggesting that the ecological restoration programme alleviated ecological degradation. However, several emergy-based indices and the support areas also illustrated that the ecological restoration programme was not successful enough in terms of preservation and utilisation of environmental resources to enhance sustainability. This indicates that further actions are necessary on conserving environmental resources, improving the emergy input structure for agricultural production and in lifestyle changes for the local people in living in the Yangou catchment. [ABSTRACT FROM AUTHOR]

Abstract: Rhizosphere is a microbiosphere with chemical, physical, and biological properties different from those of bulk soils. Knowledge of the changes in the microbial properties of plant rhizospheres is important in understanding the interactions between soil and plant communities. The present study aims to investigate the effect of bulk and rhizosphere soils on the microbial properties of eight croplands abandoned for 1, 3, 5, 10, 13, 15, 20, and 30 years and to evaluate the change in the rhizosphere soil microbial properties with time in the Loess Plateau, China. The results show that during the succession on the abandoned croplands, the pioneer species, Artemisia capillaries Thunb, was an important species in the 1- to 13-year sites, whereas the late species, Artemisia sacrorum Ledeb, emerged into the community after 13 years and became the dominant community species in 30 years. The species richness of the community exhibited an increasing trend during the first 15 years, and rapidly decreased thereafter. The organic carbon, total nitrogen, microbial biomass carbon, and microbial biomass nitrogen contents in the rhizosphere soil increased compared with those in bulk soil. Basal respiration and saccharase, alkaline phosphatase, catalase, and peroxidase activities were also enhanced, and the pH value decreased. Compared with the companion species, the dominant species showed higher organic carbon, total nitrogen, microbial biomass carbon, and microbial biomass nitrogen contents as well as enhanced respiration, but no significant difference in urease, catalase, alkaline phosphatase, and peroxidase activities was observed. As the succession proceeded, both A. capillaries and A. sacrorum showed increased microbial biomass carbon and microbial biomass nitrogen, and a decreased metabolic quotient. The soil enzymes of these two species behaved differently. Coverage and aboveground biomass of A. capillaries and A. sacrorum exhibited different relationships with microbial biomass and enzymes. In conclusion, the soil microbial activity in the rhizosphere is affected by plants, the soil condition, and the successional stage. Plant root exudates play an important role in the change in rhizosphere microbial properties. [Copyright &y& Elsevier]

Black locust ( Robinia pseudoacacia) has been widely planted in the Chinese Loess Plateau for soil and water conservation as an important forest species. This study examined variations in topsoil organic C (OC), total N and P (TN and TP), available N, P and K (AN, AP and AK), and soil microbial biomass C, N and P (SMBC, SMBN and SMBP) contents and the activity of urease (URE), α-amylase (ALA), alkaline phosphatase (ALP), catalase (CAT), saccharase (SAC), polyphenol oxidase (PPO) and cellulase (CEL) in loessial soil of black locust with an age sequence of 5, 10 15, 20, 25, 30, 40 and 50 years in Zhifanggou watershed (8.27 km), Shaanxi Province, Northwest China. Also cultivated fields and 80-year Chinese arborvitae ( Platycladus orientalis) were selected for the comparison. The results showed that soil chemical properties, microbial biomasses and soil enzyme activities varied with the restoration age. After 50-year growth of black locust, OC, TN, AN, TP, AK, SMBC, SMBN, SMBP, URE, ALP, SAC and CEL in soil increased by 262, 193, 345, 22, 36, 210, 136, 85, 90, 108, 288 and 36%, respectively, while PPO decreased by 31%. Soil chemical properties of TN and soil microbial biomass of SMBC were linearly correlated with soil enzymes of URE, ALP and SAC. Moreover, nitrogen fixation of black locusts was not evident before it became mature, but more evident after it reached maturity. The results confirmed that black locusts have long-term benefits on the improvement of soil properties as exotic species on the Loess Plateau for the soil properties under black locusts were greatly improved compared to cultivated fields. [ABSTRACT FROM AUTHOR]

De-farming slope farmland has been an effective measure in recent years to improve environment and prevent soil and water loss on the Loess Plateau. There are different views about the defarming method, and also various de-farming patterns have been put into practice. This paper takes the Yangou Watershed in Shaanxi Province of China as a case for studying the comprehensive benefits of transforming slope farmland to terraces. Based on the day-by-day meteorological data of the Yan'an station in 2005 and the data of terrain features, soil and land use data of the Yangou Watershed, the impact of transforming slope farmland on terraces were simulated and analyzed in aspects of yield increase and water-soil conservation under different topographic conditions with the aid of software WINYIELD. Furthermore, an empirical analysis was applied to study the effects of transforming slope farmland to terraces in the Yangou Watershed. The results show that: (1) The bigger the topographic gradient is, the more remarkable benefits it has in yield increase and water-soil conservation. (2) Farmland with slope below 5° could be retained, but farmland with slope above 15° should be converted to forest or grassland as soon as possible. (3) Transforming slope farmland to terraces has the same remarkable effects as the current policy of 'Relieving and de-farming' in improving agricultural production conditions, safeguarding food security, raising permanent vegetation coverage rate, and preventing soil and water loss. Besides, it is more cost-effective than the policy of 'Relieving and de-farming'. It's strongly suggested that the policy of transforming slope farmland to terraces be carried out on the Loess Plateau without delay. [ABSTRACT FROM AUTHOR]

Abstract: Severe soil and water loss has led to widespread land degradation of the Loess Plateau, China. During the past two decades, significant efforts have been made to revegetate degraded soil in the region. However, a better understanding of the ability of plants to promote soil microbial processes is important for successful revegetation. The current study was conducted at the Dunshan watershed on the Loess Plateau, with the aim of evaluating the effect of different vegetation types on the microbial properties of rhizosphere soil. Six vegetation types were evaluated: two natural grassland (Artemisia capillaries and Heteropappus altaicus), two artificial (i.e. planted by humans) grassland (Astragalus adsurgens and Panicum virgatum) and two artificial shrubland (Caragana korshinskii and Hippophae rhamnoides) species; an area without vegetation cover was used as a control. The results indicated that the highest values of soil organic C, total nitrogen (TN), microbial biomass carbon (MBC), MBN, saccharase, urease, catalase and peroxidase were recorded for H. altaicus and A. capillaries; of basal respiration (BR), the MBN: TN ratio, alkaline phosphatase and polyphenol oxidase for A. adsurgens; and of the BR: MBC ratio for P. virgatum. A rhizosphere soil microbial index (RSMI) was obtained using principal component analysis, and metabolic quotient (BR/MBC), BR, urease, water-soluble C and cellulase were found to be most important for assessing rhizosphere soil quality. All revegetated soil showed higher RSMI compared with control soil, with soil under natural grassland species (H. altaicus and A. capillaries) recording the highest value. It was concluded that plant species under arid climatic conditions have different effects on the microbial properties of rhizosphere soil owing to their different root exudates and plant debris. In addition, natural grasslands are most effective for revegetation of the Loess Plateau. [Copyright &y& Elsevier]

Soil surface characteristics are closely related to soil surface depressional storage, infiltration, runoff generation and soil erosion, especially in highly erodible loess soil. Soil surface random roughness, soil cohesion and aggregate stability are necessary parameters in the Limburg Soil Erosion Model (LISEM) and helpful in developing alternative land-use and conservation strategies. Over a period of 2 years, soil surface characteristics were measured continuously in Danangou, a small catchment in the hilly, gullied loess area in China, with the support of the Erochina project. The results show that soil surface random roughness, soil cohesion and aggregate stability differed significantly between land-use types. Ranking the types on soil roughness during the monitoring period yielded the sequence cropland>orchard and wasteland and fallow land>shrubland>woodland. The corresponding sequence for aggregate stability was approximately wasteland and woodland>cropland and orchard>shrubland>fallow land. Cohesion in the different land-use types in the catchment was smallest for cropland and largest for wasteland. There were no significant differences between croplands with different topographical characteristics. All of these soil surface characteristics showed significant temporal variation over the monitoring period. Temporal variations in roughness for shrubland and woodland over the 2-year period were significantly greater than those for other land-use types. There were also considerable variations in cohesion for shrubland, woodland and wasteland. In 1998, the weighted average values of roughness, aggregate stability and cohesion for the entire catchment were 1.113 cm, 13.6 drops and 0.131 kg/cm2, respectively, with C.V. values of 9.6%, 32.05% and 21.11%. The corresponding values for 1999 were 1.616 cm, 11.52 drops and 0.100 kg/cm2, with C.V. values of 16.0%, 15.41% and 33.33%. The temporal and spatial variations in soil surface characteristics in the catchment should be carefully taken into account in LISEM calibration and validation. [Copyright &y& Elsevier]

• Platycladus orientalis is one of the major ecological and medicinal plants. • Adventitious roots originated in multiple locations. • Tissue-specific accumulation of auxin promoted de novo root regeneration. • It is revealed developmental homeostasis of hormones during roots formation. De novo root regeneration in stem cutting is essential for massive propagation of Platycladus orientalis (L.) Franco, which is one of the major ecological and economic tree species in China. However, the details of adventitious root (AR) formation and how it is controlled by inherent hormones are still ambiguous. In this study, histological analysis, immunohistochemical localization combined with quantitative hormonal analysis were conducted to investigate how cutting induces the AR formation of P. orientalis. It was explicitly seen that AR emerged from either calli- or non-calli- covered barks. The anatomical structure showed that cutting initiated the inducible formation of AR primordia in multiple sites, including xylem, phloem, medullary ray, and annulus randomly. The tissue-specific accumulations of indole-3-acetic acid (IAA) surged in cambia-derived calli, basal boundaries of AR primordia, and AR, supporting the idea that the mode action of auxin was key to diverse types of root organogenesis. Meanwhile, the data showed that similar to that of IAA, the contents of abscisic acid (ABA) and zeatin (ZT) peaked at early stages of AR formation and deceased gradually in both phloem and xylem across the later stages, suggesting their indispensable roles in AR initiation. On contrary, jasmonic acid (JA) roughly maintained at extremely high levels in phloem comparing with the xylem tissues thoroughly, indicating its presence was involved in phloem-specific reorganization during AR formation. Collectively, the results provide a time-course histological dissection of AR formation, revealing developmental homeostasis of four main endogenous hormones, and providing theoretically a potential way to improve performance of stem-cutting in P. orientalis through regulating hormone actions in the future. [ABSTRACT FROM AUTHOR]

• The understory plant diversity of mixed-species plantations was significantly higher than that of monocultures in China. • Tree-shrub mixtures were more beneficial to increase understory plant diversity. • The improvement of understory plant diversity enhanced with the increasing stand age. • The response ratio of understory plant diversity did not change significantly with the mean annual temperature and precipitation. Understory plants are one of the important components of forest biological diversity and play important roles in forest function. Although convincing evidence exists that mixed-species plantations are more conducive to increase the productivity and stability of forest ecosystems than monocultures, the effect of mixed-species plantations on the understory plant diversity (UPD) remains uncertain. This study conducted a meta -analysis based on 205 paired observations of plant species mixtures and corresponding monocultures from 76 peer-reviewed studies to assess the impact of tree mixtures on the UPD in China. The results showed that the UPD was on average 18.2 % higher in mixed-species plantations than in monocultures. This positive mixture effect increased over time, but it would take at least ten years for the effect size of UPD to change from negative to positive. In terms of different mixed forest types, tree-shrub mixtures were more beneficial to maintain the UPD than tree-tree mixtures, and this positive effect was more significant over time. In addition, the response ratio of UPD decreased with mean annual temperature (MAT) and precipitation (MAP), but this relationship was not significant. Therefore, our results suggested that planting mixed-species plantations was a more effective approach to enhance the UPD than monocultures in China. This study revealed the characteristics of UPD under different afforestation modes and could provide a scientific basis for forest management. [ABSTRACT FROM AUTHOR]

• C:N:P stoichiometry in plants, soils, and enzymes varied with succession time. • Plant species showed a relatively strong homeostasis during secondary succession. • Rhizosphere stoichiometry differed among plant species and succession stages. • Enzyme is crucial than soil nutrients in determining plant tissue stoichiometries. Ecological stoichiometry is the study of the interaction and balance of multiple chemical elements in ecological processes. However, how ecological stoichiometric interactions among plants, soils, and enzymes in the rhizosphere affect secondary plant succession is largely unknown. In this study, we collected the dominant and main companion species Artemisia capillaris , A. sacrorum , and Stipa bungeana , along a secondary succession chronosequence (7, 12, 17, 22, and 32-year) following a cropland abandonment in the Loess Plateau, China. We measured the carbon (C), nitrogen (N) and phosphorus (P) concentrations of plant shoots and roots, as well as the concentrations of C, N, P, available N (aN), available P (aP), and the activity of one C-acquiring enzyme (β-glucosidase (BG)), two N-acquiring enzymes (N-acetylglucosaminidase (NAG), leucineaminopeptidase (LAP)), and one P-acquiring enzyme (alkaline phosphatase (AP)) found in the rhizospheric soil to explore the C:N:P stoichiometry that drives secondary plant succession. The C:P and N:P ratios in the shoots of dominant plant species significantly decreased to a minimum value at the 22-year site and then increased with plant secondary succession. Compared with the 7-year site, the rhizosphere soil C:P and N:P ratios, and enzyme N:P ratios (ln(NAG + LAP):ln(AP)) increased 103.6%, 72.0%, and 221.3%, respectively, but enzyme C:N ratios (ln(BG):ln(NAG + LAP)) decreased 48.2% in the dominant plant species at the 32-year site. Principal component analysis indicated that the stoichiometry characteristics of the plant-soil-enzyme continuum differed for each plant species and succession stage. Stoichiometric homeostasis indices for the plant species indicated a relatively strong homeostasis, while redundancy analysis revealed that the variations in soil BG, NAG, and AP activity and enzyme C:N ratio had significant effects on the stoichiometries and nutrient concentrations of the plant tissues. The results indicated that rhizosphere stoichiometry is a powerful tool for evaluating plant-soil interactions in terrestrial ecosystems and that the variation in rhizospheric soil enzyme activity driving the secondary succession of plants. [ABSTRACT FROM AUTHOR]

• Mixed plantations showed 19.3% higher STN stocks than monocultures. • Tree-shrub mixed plantations presented the greatest STN stocks benefits. • Changes in STN stocks were also influenced by climate, topography, and plantation age. • Soil pH did not significantly affect the response ratio of STN stocks. Nitrogen (N) is one of the primary limiting elements in terrestrial ecosystems, and vegetation restoration has been regarded as an effective way to increase soil total nitrogen (STN) stocks. Despite compelling evidence indicating that mixed plantations can demonstrate higher vegetation productivity and carbon (C) sequestration capacity than monocultures, the effects of mixed plantations on STN stocks remain unclear. Therefore, we conducted a meta-analysis of 128 observations from 49 peer-reviewed articles across the Loess Plateau of China to evaluate the impact of different afforestation models (i.e., mixed plantations and monocultures) on the dynamics of STN stocks in mineral soil (0–30 cm). The results showed that, compared with monocultures, mixed plantations significantly increased STN stocks by 19.3%. For different mixed types, tree-shrub mixed plantations increased more STN stocks than tree-tree mixed plantations. However, the positive effect of mixed plantations on STN stocks was significant > 20 years after stand establishment. Moreover, for areas with steeper slope (>25°), lower elevation (<1200 m), and climate restricted (MAT < 8℃, MAP < 500 mm), mixed plantations had more advantages in increasing STN stocks than monocultures. Additionally, the response ratio of STN stocks was negatively correlated with the initial STN stocks, response ratios of soil pH, and bulk density (BD) but positively correlated with the response ratio of soil organic carbon (SOC) stocks. Our results demonstrate that increasing tree species richness is an important strategy to increase STN stocks. [ABSTRACT FROM AUTHOR]

• Specific enzyme activities increased and then decreased along secondary succession. • Soil enzyme temperature sensitivities (Q 10) changed along succession in rhizosphere. • Q 10 at different temperature ranges differed in bulk soil, but not in rhizosphere. • Rhizosphere effects of enzyme activities changed to negative value with succession. The influence of plant secondary succession on soil enzyme activities has been increasingly recognized recently. However, the characteristics of specific enzyme activities and temperature sensitivity (Q 10) in the rhizosphere remain elusive. We collected rhizosphere and bulk soil samples from a secondary successional series (0, 7, 12, 17, 22, and 32 years after farmland abandonment, and a natural grassland reference) in a typical semi-arid ecosystems on the Loess Plateau of China. The potential activity of soil enzymes, including β-1,4-glucosidase (BG), β-1,4-N-acetylglucosaminidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (AP), was assayed at 37, 20 and 4 °C and expressed as activity per unit of soil organic carbon (specific enzyme activity). Q 10 values were calculated at 20–37 °C and 4–20 °C, respectively. The specific enzyme activities of BG, NAG, LAP and AP in bulk soil increased to a maximum at the 17-year site and then significantly decreased in older grasslands. In the rhizosphere, specific enzyme activities increased and then decreased along the successional gradient with significantly higher value at the 7-year site and the 17-year site. The Q 10 values of BG activity in bulk soil and the four enzyme's activities in rhizosphere soil were changed significantly along the successional gradients. In general, the Q 10 values at the two temperature ranges differed in bulk soil, but not in the rhizosphere soil. Along the plant successional gradient, the rhizosphere effects of specific enzyme activities gradually changed to negative values in the oldest sites. Our results indicate that plant secondary succession had different impacts on the enzyme activity and characteristics in the rhizosphere and bulk soil, and highlights the importance of temperature sensitivity and rhizosphere effects of enzyme activity along plant secondary successional gradients. [ABSTRACT FROM AUTHOR]

• Thinning significantly increased SOC stocks in planted forests in China. • Moderate thinning increased SOC stocks more than other levels of thinning intensity. • Thinning in areas with lower humidity showed higher SOC stocks. • Thinning was found to increase SOC stocks significantly after five years of recovery. • Thinning increased the sensitivity of SOC stocks and TN stocks. Thinning is a common forest management practice. However, its impact on soil organic carbon (SOC) stocks is still unknown. Therefore, we conducted a meta-analysis of 270 measurements from 77 articles to evaluate the effect of forest thinning on SOC stocks in mineral soil (0–30 cm) across planted forests in China. The results showed that, compared to reference (non-thinned) plantations, thinning significantly increased SOC stocks in planted forests by 7.2%. Among different thinning intensities, moderate thinning (35–55% of thinning intensity) increased SOC stocks in planted forests (+16.1%) more than other levels of thinning intensity. However, the positive effect of thinning on SOC stock was significant > 5 years after harvesting. In the humidity-restricted areas (humidity index (HI) < 30), the increase in SOC stocks after thinning was significantly higher than that of other areas. In addition, thinning increased the sensitivity (i.e. slope value) of soil total nitrogen (TN) stocks changes to SOC stocks. Therefore, we conclude that forest thinning strategy is potentially a viable silvicultural measure to increase SOC fixation in planted forests. Our results provide a reference for the formulation and implementation of future forest management strategies. [ABSTRACT FROM AUTHOR]

• Microbial processes during secondary succession were studied on the Loess Plateau. • Microbial communities showed stoichiometric homeostasis during plant secondary succession. • Microbial metabolisms were co-limited by C and P during plant secondary succession. • Microbial activities were strongly affected by soil nutrient status. Soil microbial metabolism is vital for nutrient cycling and ecosystem stability. To quantify microbial metabolism and nutrient limitation during plant secondary succession, we measured soil physicochemical properties, microbial biomass, and four enzyme activities (β-1,4-glucosidase (BG), β-1,4- N -acetylglucosaminidase (NAG), L -leucine aminopeptidase (LAP), and alkaline phosphatase (AP)) and identified the changes of soil ecoenzymatic stoichiometry and microbial nutrient limitation along a secondary succession series in typical arid and semi-arid ecosystems on the Loess Plateau, China. Soil enzyme activities increased in the first 17a succession and then decreased with plant secondary succession. The ln(BG):ln(NAG + LAP) ratio and ln(BG):ln(AP) ratio showed a decreasing trend in the first 22a succession and then increased. Most soil nutrient contents and nutrient stoichiometry were significantly correlated with enzyme activities and enzymatic stoichiometry. Moreover, vector analysis of soil enzymes indicated that microbial community were co-limited by C and P during secondary succession. Linear regression of C:N and C:P between the soil nutrient and microbial community showed that soil microbial community maintained stoichiometry homeostasis during plant secondary succession. The threshold elemental ratio revealed that the microbial nutrient metabolisms were co-limited by N and P, particularly P during plant secondary succession. Therefore, microbial communities were co-limited by C, N, and P, particularly C and P during plant secondary succession, and the limitation was mainly associated with soil nutrient status. [ABSTRACT FROM AUTHOR]

Research Highlights: Soil enzymes have a significant impact on the production of glomalin-related soil protein (GRSP), directly and indirectly affecting the nutrient metabolism balance, but there is little available information on ecological stoichiometry in soil aggregates. Background and Objectives: Vegetation restoration changes community structure and species composition in ecosystems, thus changing the physicochemical properties of soil. Soil aggregate is the most basic physical structure of the soil. Therefore, in order to understand dynamic changes in soil aggregate nutrients as vegetation restoration progresses, we set out to investigate the nutrient distribution and utilization in aggregates, and how enzymes respond to the nutrient changes in achieving a nutritional balance along successive stages of vegetation restoration. Materials and Methods: We collected and analyzed soil from plots representing six different stages of a vegetation restoration chronosequence (0, 30, 60, 100, 130, and 160 years) after farmland abandonment on the Loess Plateau, China. We investigated soil nutrient stoichiometry, GRSP, and enzyme stoichiometry in the different successional stages. Results: The results revealed that soil organic carbon, total nitrogen, enzyme activity, and GRSP increased with vegetation recovery age, but not total phosphorus, and not all enzymes reached their maximum in the climax forest community. The easily extractable GRSP/total GRSP ratio was the largest at the shrub community stage, indicating that glomalin degradation was the lowest at this stage. Ecological stoichiometry revealed N-limitation decreased and P-limitation increased with increasing vegetation restoration age. Soil enzymes had a significant impact on the GRSP production, directly and indirectly affecting nutrient metabolism balance. Conclusions: Further study of arbuscular mycorrhizal fungi to identify changes in their category and composition is needed for a better understanding of how soil enzymes affect their release of GRSP, in order to maintain a nutrient balance along successive stages of vegetation restoration. [ABSTRACT FROM AUTHOR]

Plant–plant interactions are dynamic and complicated processes that strongly influence soil nutrient cycling in ecosystems. Climate warming-induced drought stress and the duration of plant interactions may reshape or complicate this ecological process. However, little is known about how plant–plant interaction time (co-growth duration) combined with drought stress affect soil chemical properties and enzyme activities. In this study, Stipa bungeana and Bothriochloa ischaemum , which were the main plant species during the later stages of secondary succession in an abandoned cropland on the Loess Plateau of China, were planted as a single plant or in combination, in a plastic pot with two water regimes (ample water, 80 % of field capacity (FC); drought stress, 60 % of FC) for two consecutive years. The rhizosphere soil was collected each year to determine the nutrient contents and enzyme activities, and the microbial metabolic limitations were calculated. We found that plant–plant interactions, drought stress, and sampling year had a significant influence on most rhizosphere soil nutrient contents and enzyme activities. Redundancy analysis showed that soil pH, available phosphorus (aP), and total phosphorus had significant effects on soil enzyme activities in the first year, and soil total nitrogen and aP had significant effects on soil enzyme activities in the second year. Vector analysis indicated that drought stress increased microbial carbon (C) and phosphorus (P) limitation under each planting pattern, and these metabolic limitations showed a decreasing trend in the second year. An structural equation model demonstrated that plant–plant interactions on microbial C and P limitation were larger than drought stress in the first year. Conversely, in the second year, the plant–plant interactions on microbial C and P limitation were lower than that of drought stress. Our findings highlighted that the duration of plant–plant interactions had a significant influence on C flows and nutrient cycling in plant–soil systems, and improved the understanding of plant–plant interactions and drought stress on soil nutrient cycling and microbial metabolic limitations in vegetation restoration ecosystems. • Plant interaction and drought influence rhizosphere nutrient and enzyme activities. • Soil pH, nitrogen, and phosphorus had significant effects on enzyme activities. • Drought stress significantly increased microbial C and P limitation. • Plant interaction duration regulates soil microbial metabolic limitation. [ABSTRACT FROM AUTHOR]

• Mixed forests show a higher soil erosion control benefit than monocultures. • Tree-shrub mixtures reduce runoff and sediment more than tree-tree mixtures. • Mixed forests have the strongest positive impact on soil erosion control in dry areas. • Mixed forests are found to affect soil erosion most efficiently after 20 years of tree growth. • Mixed forests have the highest impact on soil erosion control on slopes of 16–20°. Soil erosion poses a major threat to the sustainability and stability of global terrestrial ecosystems. Mixed forests have more advantages in restoring degraded land and enhancing soil fertility than monocultures, but their influence on soil erosion remains uncertain. Therefore, we presented a meta -analysis consisting of 261 paired observations of mixed forests and the corresponding monocultures from 65 studies to evaluate the effect of tree diversity on soil erosion in China. The results showed that compared with monocultures, mixed forests significantly reduced the annual runoff and sediment yield by 17.4% and 23.6%, respectively. Tree-shrub mixtures showed more efficiency in reducing runoff (24.2%) and sediment yield (32.1%) than tree-tree mixtures. However, the positive effect of mixed forests on soil erosion control was significant > 20 years after stand establishment. Mixed forests showed the highest capacity to control soil erosion at slope angles of 16°-25° (runoff: 27.7%; sediment yield: 37.7%). In terms of soil textures, mixed forests performed better with respect to soil erosion control on sandy soils (runoff: 21.4%; sediment yield: 30.1%), whereas significant differences were not observed between different stand types on clayey soils. In addition, in the dry areas (humidity index (HI) < 30), mixed forests conferred the greatest benefits in reducing runoff and sediment yield (25.8% and 33.0%, respectively). Our results indicate that increasing tree species richness is a suitable approach to controlling soil erosion in China. This research provides a scientific basis for the management and sustainable development of forest ecosystems in the future. [ABSTRACT FROM AUTHOR]

• Planted forest (PF) allocated larger proportion of biomass carbon (C) to belowground than natural forest (NF). • Turning points existed in biomass C allocation along climatic gradient for both PF and NF. • Soil properties had stronger effects on biomass C allocation in PF than NF. Establishing planted forests (PF) by afforestation and naturally regenerating forests (NF) are important measures of enhance carbon (C) sequestration in terrestrial ecosystems. However, the difference of biomass C stocks and allocation between NF and PF and their determinants in water-limited areas remain unclear. To address this gap, we conducted a synthesis of above-ground biomass C (AGBC), below-ground biomass C (BGBC) stocks and root to shoot ratios (R:S) of PF and NF in the Chinese Loess Plateau. The changes in biomass C stock and R:S along a climate gradient were investigated, and the relationships between R:S and soil properties were also quantified. We found that PF exhibited lower AGBC and BGBC stocks compared to NF, but the average R:S in PF was significantly higher than that of NF (0.48 ± 0.27 vs. 0.30 ± 0.11, p < 0.05). Turning points existed in biomass C allocation along climatic gradient for both PF and NF. More biomass C was allocated to AGBC in PF and NF when mean annual precipitation exceeded 494 mm and 588 mm, respectively. Higher mean annual temperature promoted larger C allocations to BGBC in PF compared to NF. Soil properties had a stronger effect on the biomass C allocation patterns after afforestation, but to a lesser extent on NF. This study indicates that afforestation promotes a larger allocation of biomass C into the below-ground compared to naturally regenerated forests, and using the default R:S estimates may result in a severe underestimation of below-ground C stocks in water-limited areas. The biomass C stocks and allocation are collectively determined by climate conditions and soil properties, and accumulated below-ground biomass C stock induced by dryland afforestation may be an important C sink at a broad geographic scale. [ABSTRACT FROM AUTHOR]

The Pisha sandstone area on the Ordos Plateau of China is the primary source of coarse sediment (with a particle size d > 0.05 mm) of the Yellow River. Sediment size distribution and selectivity greatly affect sediment transport and deposition. Hence, sediment transport processes and size selectivity by overland flow on Pisha sandstone slopes were investigated in this study. Experiments were run with Pisha sandstone soil (bulk density of 1.35 g cm−3) under rainfall intensities of 87 and 133 mm h−1 with a 25° slope gradient, and the duration of simulated rainfall was 1 h. Sediment and runoff were sampled at 2-min intervals to examine the size distribution change of the eroded sediment. The particle composition, enrichment rate, fractal dimension, and time distribution characteristics of median grain size (d 50) of eroded sediment were comprehensively analyzed. Statistical analyses showed that Pisha sandstone slope generated a large amount of coarse sediment during the erosion. >40% of eroded sediment particles were coarse sediment, which will become the main sediment in the lower reaches of the Yellow River bed. The particle size of eroded sediment tended to gradually decrease with the continuous rainfall but remained larger than the initial value of Pisha sandstone soil after refinement. The fractal dimension was positively correlated with the slope flow velocity, while the d 50 was negatively correlated with the slope flow velocity. Overall, these findings indicates that the selectivity and transportation of sediment particles on the Pisha sandstone slopes is mainly influenced by the hydrodynamic parameters of overland flow. The reason for the large amount of coarse sediment generated during the erosion in Pisha sandstone area is not only related to the large porosity and a small cohesive force of sand, but also related to the hydraulic conditions of the Pisha sandstone slopes. In the Pisha sandstone area, we should control soil erosion mainly by reducing the initial erosion dynamics, such as reducing splash erosion, increasing soil infiltration and surface resistance. This study provides a methodology and data references for studying the particle selectivity characteristics of eroded sediment and provides a scientific basis for revealing the mechanism of erosion and sediment yield in the Pisha sandstone area of China. Changes in the proportions of sediment particles over time. Unlabelled Image • Transport processes of soil particles under simulated rainfall were investigated. • >40% of eroded particles are sand with a particle size d > 0.05 mm. • Size distribution tends to be closer to that of the original soil. • Selectivity and transportation of sediment particles was related to hydrodynamic parameters. [ABSTRACT FROM AUTHOR]

• Planted forest (PF) invests more carbon (C) to below-ground biomass and deep soil layer than natural forest (NF). • NF stored more than twice as much C as did PF in both biomass and soil, but exhibited much lower C sequestration rates than PF. • Afforestation promotes C accumulation without causing soil water deficit under precipitation higher than 505 mm. • Warming improves the C accumulation in PF but accelerated the soil C loss in NF. Large-scale afforestation has been widely implemented for restoring the degraded lands and mitigating climate change while naturally regenerated forests should be protected to preserve carbon (C) in land ecosystems. However, a critically needed comparison on the effectiveness of C sequestration between planted forest (PF) and natural forest (NF) in water-limited areas has rarely been conducted at a regional scale. This study synthesized 275 publications to examine the changes of C stock in above-ground biomass (AGB), below-ground biomass (BGB) and deep soils (0-200 cm) between PF and NF in the China's Loess Plateau, a typical water-limited region with extensive afforestation. We found that, NF stored more than twice as much C as did PF in both biomass and soil. But PF allocated relatively higher proportion of C stock to BGB and deep soil layer (> 100 cm) than NF. Moreover, the C sequestration rates in biomass and soil for PF were 1.42 and 1.72 Mg C ha−1 yr−1, respectively, much higher than that of NF (0.13 and -1.38 Mg C ha−1 yr−1). In addition, afforestation in areas with the mean annual precipitation (MAP) greater than 505 mm may promote both biomass and soil C accumulation without causing severe soil water deficit. Moreover, the increase in mean annual temperature (MAT) could significantly promote the C accumulation in both biomass and soil of PF but accelerated the soil C loss of NF. Overall, our results indicate that afforestation in water-limited areas may exhibit higher potential to sequester C than naturally regeneration, and afforestation is worth promoting with careful consideration of planting density and rainfall zones to avoid causing excessive water depletion. This study has important implications for the forest management in water-limited areas particularly under global climate change. [ABSTRACT FROM AUTHOR]

China has launched multiple afforestation programs since 1978, including the ‘Three North’ Shelterbelt Development Program (TNSDP), the Beijing–Tianjin Sand Source Control Program (BSSCP), the Nature Forest Conservation Program (NFCP), and the Grain to Green Program (GTGP). These programs focus on local environment restoration by planting trees in semi-arid and arid regions and by protecting natural forests. However, the effectiveness of these programs has been questioned by several previous studies. Here, we report an increasing trend of greenness in this region using the satellite-retrieved normalized difference vegetation index (NDVI) from GIMMS, GIMMS-3g and MODIS datasets in the past 32 years. The NDVI increase for the ‘Three North’ region was 0.28%–0.38% yr −1 in 1982–2000 and 0.86%–1.12% yr −1 in 2000–2013, which is much higher than the country's means of 0.060%–0.063% yr −1 and 0.27%–0.30% yr −1 , respectively. Most of the increase occurred in low and sparsely vegetated areas; and enlarged the moderate vegetated area (growing season mean NDVI above 0.5) from 16.5% to 25.7% for the two time periods, respectively. We also analyzed changes in the length of the growing season and the climate conditions including temperature, precipitation and two drought indices. However, these environmental factors cannot completely explain the changes in vegetation activity. Our study suggests these multiple afforestation programs contributed to the accelerated greening trend in the ‘Three North’ region and highlight the importance of human intervention in regional vegetation growth under climate change condition. [ABSTRACT FROM AUTHOR]

This article elucidates the health-related quality of life (HRQOL) the recognition of desertification among people living in the semi-arthree-dimensionalid Loess Plateau of China. HRQOL was assessed with a three-dimensional survey of general health perception, vitality, and general mental health based on a 36-item short-form health survey (SF-36). Scores for general health perception were approximately the same in the city and the village communities. Vitality and mental health scores were significantly lower for women in the village communities than for other groups. In the village communities, HRQOL was significantly and positively correlated with income. The inhabitants of the village communities were more satisfied with their life situation than those in the city, in spite of the economic gap between them. Levels of recognition of desertification were lower in the village communities than in the city. [ABSTRACT FROM AUTHOR]

On the Loess Plateau in China, soil erosion amounts to between 10 000 and 25 000 tons/km2/year. In 1998, the EROCHINA project was started, with the major objective of developing alternative land-use and soil and water conservation strategies for the Loess Plateau, using the LISEM soil erosion model. In order to provide the model with accurate input on soil hydraulic properties of the catchment, this study tried to quantify these properties for major land-use units and to examine the effects of the statistically identified in-field heterogeneity on model outcome. The study area (Danangou catchment) is located in the middle part of the Loess Plateau in the northern part of Shaanxi Province. The catchment is about 3.5 km2 in size. To determine the hydraulic properties of the soil, a sampling scheme was implemented to measure unsaturated conductivity and water retention characteristics. The saturated conductivity measurements were performed on land-use clusters, based on treatment and plant and soil differences. A 100×100 m sampling grid was set out on 12 fields, with 1×1 m grid squares. On each field, 10 sampling spots were randomly selected, using Simple Random Sampling. The sensitivity of the LISEM model to the measured heterogeneity of saturated conductivity was analysed by using the geometric mean and standard deviation (S.D.) of the Ks-optimized of the various land-use units to calculate discharge and soil loss during a single rain event. This proved that, using the standard deviation of the saturated conductivity, which was 30–50%, the calculated discharge and total sediment losses varied by a factor 2. Using the standard deviation had a minor effect on the calculated sediment concentration. As regards the on-site effects, the use of the geometric mean of Ks minus the S.D. resulted in an increase in the level of erosion, while the use of geometric mean of Ks plus the S.D. value resulted in a significant decrease in erosion level relative to that obtained using the geometric mean of Ks itself. Using randomly selected sampling spots and a calibration procedure as was done in the present study make detailed information on Ks available, which can be used to compare alternative land-use options for their effectiveness in reducing discharge and sediment losses. [Copyright &y& Elsevier]

• Warming significantly lowered soil nematode diversity. • Warming indirectly and directly affected vegetation to lead to soil nematodes diversity being changed. • Warming and litter removal significantly reduced external resource inputs to the food web. • Warming and litter removal lead to soil food web degradation. Both climate warming and litter removal alter soil nematode communities and the structure, stability, and function of soil food webs. The soil nematode metabolic carbon footprint, based on nematode biomass and respiration, can be used to indicate ecosystem function and the response of nematodes to nutrient enrichment in the ecosystem. However, it is unclear whether or how climate warming and litter removal affect the metabolic carbon footprint of soil nematodes and soil food webs. In this study, we investigated four warming and litter removal treatments in the Qinghai-Tibet Plateau, China, to determine the effects of climate warming and litter removal on soil microbial food webs. The treatments included: (1) control (CK), (2) warming, (3) litter removal, (4) warming + litter removal. We found that warming and litter removal had significant negative effects on the diversity and richness of soil nematodes. In addition, our results showed warming indirectly and directly affected vegetation diversity, thereby altering soil nematode diversity. Vegetation played an important role in the maintenance of soil nematode community diversity. The enrichment and structural footprints reflected nematodes that could respond most rapidly to resource enrichment and those with higher trophic levels in soil food webs, respectively. Overall, warming and litter removal significantly negatively affect the enrichment metabolic footprint, indicating they could significantly reduce the external resource inputs into the food web. Both warming and litter removal reduced the structural metabolic footprint of the soil food web, although the changes were not significant, indicating that the metabolic activity of nematodes of high nutrient levels decreased and the ability to regulate the food web from top-bottom effects was weakened under warming and litter removal. The nematode functional metabolic footprints indicated that litter removal could aggravate the effect of warming on the soil food web and result in more severe degradation. The combination of warming and litter removal significantly inhibited the connectance of the bacterial channel, but had no significant effect on the fungal channel. These results suggest that the soil food web enhanced resistance to the environment by increasing the proportion of the fungal channel. It is critical to understand the responses of soil food webs to climate warming and litter removal to better predict how ecosystem functions will change in the future. [ABSTRACT FROM AUTHOR]

• Soil nematode diversity and abundance increase with vegetation restoration time. • Vegetation restoration time enhances metabolic activity of omnivorous carnivores. • Longer restoration time promotes carbon flow and stabilizes the soil food network. • During land restoration bacteria were more important than fungi in the carbon flow. • Abandoning agriculture can help to avoid soil degradation in the Loess Plateau. Soil nematode communities play a significant role in soil ecosystems. Indeed, soil nematode metabolic carbon footprint, based on nematode biomass, is used to evaluate ecosystem functioning and assess nematode response to ecosystem nutrient enrichment. However, it is unclear whether vegetation restoration affects the metabolic carbon footprint of soil nematodes and soil food webs. We selected five periods for this study including: (1) farmland (0 years), (2) grassland (30 years), (3) shrubland (60 years), (4) pioneer forest (100 years), and (5) climax forest (160 years). Community composition, diversity, and metabolic footprint of soil nematodes, and carbon flow changes through the food web were investigated. The Shannon diversity (H′) index of the soil nematode community increased in the process of restoration, and the Pielou index (J′) appeared to be lower at 30 years after vegetation restoration than at 60, 100, and 160 years. The connectance of the soil nematode food web values increased continuously, from 30 years to 160 years, reaching the highest value at 100 and 160 years, which indicated that the food web had the strongest carbon flow at 100 years after vegetation restoration on the Loess Plateau, indirectly reflecting the stability of the soil food web. Bacteria were more important than fungi in the carbon flow in the food web during vegetation restoration. The study demonstrated that vegetation restoration promoted the input of the availability of external resources, enhanced the metabolic activity of omnivorous carnivores and the soil carbon flow, and stabilized the soil food web. However, the increase in vegetation restoration time not only changed the species composition but also changed the carbon input, due to the lack of interference by agriculture. Therefore, the intrinsic mechanism needs to be studied further. [ABSTRACT FROM AUTHOR]

• DOM biodegradability and its temperature sensitivity were simultaneously evaluated. • Natural vegetation restoration significantly increased recalcitrant humic substrates in DOM. • Increased temperature significantly promoted biodegradation of recalcitrant humic substrates in DOM. • DOM biodegradability and its temperature sensitivity were regulated by DOM substrate quality and microbial properties. Biodegradation of dissolved organic matter (DOM) plays a key role in regulating both production of greenhouse gases and accumulation and stabilisation of soil organic matter (SOM). However, the mechanisms by which natural vegetation restoration affects the extent, rate, and temperature sensitivity of DOM biodegradation are poorly understood. Elucidating these mechanisms is important for SOM management, especially in light of future climate warming scenarios. In this study, a laboratory DOM solution incubation experiment was conducted to comprehensively investigate the effects of temperature and natural vegetation restoration spanning a period of 160 y on DOM biodegradation in the Loess Plateau, China. The results indicated that dissolved organic C (DOC) biodegradation significantly decreased with vegetation restoration after an incubation period of 60 d. Further, biodegradation of dissolved organic N (DON) and dissolved organic P (DOP) significantly decreased after farmland abandonment. Specifically, the lowest values were observed in pioneer (Populus davidiana) and mingled (Populus davidiana and Quercus liaotungensis) forests. Generally, an increase in temperature significantly promoted the biodegradation of DOC, DON, and DOP by enhancing the microbial utilisation efficiencies of recalcitrant humic substrates (i.e., low-molecular-weight humic materials). Our results suggest that DOM biodegradability and its temperature sensitivity were regulated by DOM substrate quality (i.e, recalcitrant humic materials), and microbial properties (i.e., gram-negative bacterial and fungal PLFA, enzyme activities). Additionally, our results suggest that climax forest communities (Quercus liaotungensis) played a vital role in reducing DOC and DOP losses. This could be attributed to the low Q10 of the DOC and DOP biodegradation rates. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Recovery years increased soil enzyme activity in the steppe and forest-steppe zone. • Recovery years decreased SOC stability in the steppe and forest-steppe zone. • The forest zone might have the most stable soil enzyme activity and SOC stability. • Key factors regulating these changes are different among the three vegetation zones. The effects of cropland abandonment on soil enzyme activity and soil organic carbon (SOC) stability, along with the driving factors, are poorly understood. Here, we aimed to systematically and comprehensively evaluate soil enzyme activity, SOC stability, and the associated driving factors in different vegetation zones after cropland abandonment on the Loess Plateau, China. We selected grasslands with different recovery times along a rainfall gradient encompassing the steppe zone (SZ), forest-steppe zone (FSZ), and forest zone (FZ). We measured and compared the changes in soil enzyme activity (saccharase, polyphenol oxidase, urease, phosphatase, and catalase) and SOC stability as a function of recovery time; we also evaluated the relationships between these two parameters. In SZ and FSZ, soil enzyme activity, fractions of oxidizable carbon (including very labile [C1], labile [C2], and less labile [C3]), and the carbon management index (CMI) increased with recovery time, whereas the SOC stability index (SI) decreased. Conversely, in FZ, polyphenol oxidase activity increased linearly, urease and catalase activities decreased linearly, and the change in saccharase activity was represented by a cubic equation regression. SI showed no obvious changes with recovery time, whereas C1, C2, and C3 initially decreased and then increased. Redundancy analysis showed that, in FSZ and FZ, soil enzyme activity, C1, C2, C3, and SI were influenced by vegetation diversity, coverage, and soil nutrient levels. In comparison, in SZ, these parameters were mainly influenced by soil nutrient levels. Soil enzyme activity was strongly correlated with C1 and C3 in SZ and FSZ, but not in FZ. Overall, in SZ and FSZ, soil enzyme activity increased with recovery time, whereas SOC stability decreased. In contrast, both parameters were relatively stable in FZ, which had higher mean annual precipitation and mean annual temperature. [ABSTRACT FROM AUTHOR]

• Recovery years increased soil microbial activity in the surface layer (0–10 cm) • Recovery years enhanced stratification ratios of rhizosphere soil microbial (SRR 1) • SRR 1 became positive with increased soil microbial activity. Studying soil microbial activity is important for evaluating soil microbial conditions and soil nutrient cycling. This study examined how the conversion of cropland to forest affects soil microbial activity and stratification ratios of the rhizosphere soil microbial index (RSMI), as well as to clarify the relationship between the stratification ratios of RSMI and soil microbial activity. Soils beneath two typical vegetation types of shrubland (Caragana korshinskii and Hippophae rhamnoides) and forestland (Robinia pseudoacacia) in the Loess Hilly region of China that had recovered for up to 47 and 56 years, respectively, were evaluated at four soil depths (0–10, 10–20, 20–30, and 30–50 cm). Our findings showed that the conversion of cropland to forest mainly affected soil microbial activity in the surface layer (0–10 cm), in which microbial biomass, enzyme activity (saccharase, urease, and phosphatase), and RSMI increased over time, whereas the microbial metabolic quotient decreased. After the conversion from cropland, recovery time (years) caused an increase in the SRR 1 (the RSMI ratio in 0–10 cm versus 10–20 cm layer) of shrubland (by 40.56–108.14%, compared to 0 year) and forestland (by 18.48–79.71%, compared to 0 year). Overall, SRR 1 was positively correlated with RSMI in both conversion types. In conclusion, the stratification ratios of the rhizosphere soil microbial index of SRR 1 provided good indicators of soil microbial activity and were significantly enhanced by the process of the conversion from cropland to forest. [ABSTRACT FROM AUTHOR]