Search

The Grain for Green Project (GGP) is a major national initiative aimed at ecological improvement and vegetation restoration in China, achieving substantial ecological and socio-economic benefits. Nevertheless, research on vegetation cover trends and the long-term restoration efficacy of the GGP in the Loess Plateau remains limited. This study examines the temporal–spatial evolution and sustainability of vegetation cover in this region, using NDVI data from Landsat (2000–2022) with medium-high spatial resolution. The analytical methods involve Sen's slope, Mann–Kendall non-parametric test, and Hurst exponent to assess trends and forecast sustainability. The findings reveal that between 2000 and 2022, vegetation coverage in the Loess Plateau increased by an average of 0.86% per year (p < 0.01), marked by high vegetation cover expansion (173 × 103 km2, 26.49%) and low vegetation cover reduction (149 × 103 km2, 22.83%). The spatial pattern exhibited a northwest-to-southeast gradient, with a transition from low to high coverage levels, reflecting a persistent increase in high vegetation cover and decrease in low vegetation cover. Approximately 93% of the vegetation cover in the Loess Plateau showed significant improvement, while 5% (approximately 31 × 103 km2) displayed a degradation trend, mainly in the urbanized and Yellow River Basin regions. Projections suggest that 90% of vegetation cover will continue to improve. In GGP-targeted areas, high and medium-high levels of vegetation cover increased significantly at rates of 0.456 ×103 km2/year and 0.304 × 103 km2/year, respectively, with approximately 75% of vegetation cover levels exhibiting positive trends. This study reveals the effectiveness of the GGP in promoting vegetation restoration in the Loess Plateau, offering valuable insights for vegetation recovery research and policy implementation in other ecologically fragile regions. [ABSTRACT FROM AUTHOR]

Vegetation restoration plays a crucial role in conserving soil and water, as well as rehabilitating ecosystems, by enhancing soil properties and vegetation attributes. The evaluation of the ecological consequences among different vegetation restoration types can be achieved by clarifying the impacts on carbon, water and nutrient storages. In this study, we selected four typical vegetation restoration types (Pinus tabuliformis forest (PTF), Platycladus orientalis forest (POF) and Robinia pseudoacacia forest (RPF) as typical planted forests, and the natural secondary forest (NSF) as the control treatment) in the eastern Loess Plateau of China. The soil properties (at 0–200 cm depth) and vegetation attributes (including arborous, shrubs and herbaceous plants) were measured, as well as calculated soil carbon, water and nutrient storages, with a total of 1600 soil samples and 180 vegetation survey plots. The partial redundancy analysis (pRDA) and correlation analysis were also used to analyze the contributions and relationships among environmental factors, soil eco-hydrology and nutrient supplement services in different forestry ecosystems. The results indicate the following: (1) NSF has the lowest soil bulk density (1.21 ± 0.184 g·cm−3). Soil properties varied significantly at vertical scales, and had obvious surface accumulation. (2) Soil moisture storages were better in natural forests than those in planted forests, with more drastic changes in soil moisture dynamics. (3) The soil carbon, nitrogen, and phosphorus storages significantly differed among four vegetation types, with the highest carbon storages in PTF (207.75 ± 0.674 t·ha−1), the highest nitrogen storages in POF (5.54 t·ha−1), and the highest phosphorus storages in RPF (4.33 t·ha−1), respectively. (4) Soil carbon storages depend primarily on the coupling effect of soil properties and precipitation, while nutrient storage is mainly influenced by soil properties. The results quantify the significant differences in soil water, carbon, and nutrient storage across various vegetation restoration types, and reveal the individual and combined contributions of environmental factors, providing new insights into the mechanisms driving these differences. These findings offer practical guidance for the sustainable management of forest ecosystems and the optimization of ecological restoration strategies on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms and patterns of runoff generation in watersheds is fundamental to building hydrological and soil erosion models. It also provides important guidance for watershed water resources management and rational utilization. In order to reveal the in- fluence of vegetation restoration on the runoff production mechanism and model of the Loess Plateau, the Dongzhuanggou watershed, which is dominated by natural grassland restoration, and the Yangjiagou watershed, which is dominated by afforestation restorationin in the gullied loess plateaus were taken as research areas. The flood process lines and regression curves of two contrasting small catchments under different rainfall types were analyzed, and the change of runoff production pattern in the gullied region of loess plateau under vegetation restoration was studied. The results indicate that with the restoration of the watershed's vegetation and its eco-hydrological functions in these small water- sheds, annual runoff generation capacity decreases, while water retention capacity increases. Vegetation restoration effectively reduces peak flow and prolongs flood duration, especially the recession period of the flood, thereby achieving the effect of flood mitigation. Under the influence of vegetation restoration, the runoff generation pattern tends to shift from the traditional infiltration-excess runoff pattern to a shallow sub- surface saturation runoff pattern. This change demonstrates that vegetation restoration can effectively mitigate floods and thus play a significant role in flood control and disaster reduction. Additionally, it can efficiently transform generalized precipitation resources into soil water and interflow, regulate the seasonal distribution of streamflow, increase ecological water use, and promote the healthy and stable development of vegetation ecosystems in semi-arid areas. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vegetation restoration is an effective measure to cope with global climate change and promote soil carbon sequestration. However, during vegetation restoration, the turnover and properties of carbon within various aggregates change. The effects of plant source carbon input on surface soil and subsurface soil may be different. Thus, the characteristics of carbon components in aggregates are affected. Therefore, the research object of this study is the Robinia pseudoacacia forest located in 16–47a of the Loess Plateau, and compared with farmland. The change characteristics of organic carbon functional groups in 0–20 cm, 20–40 cm, and 40–60 cm soil layers were analyzed by Fourier near infrared spectroscopy, and the relationship between the chemical structure of organic carbon and the content of organic carbon components in soil aggregates was clarified, and the mechanism affecting the distribution of organic carbon components in soil aggregates was revealed in the process of vegetation restoration. The results show the following: (1) The stability of surface aggregates is sensitive, while that of deep aggregates is weak. Vegetation restoration increased the surface soil organic carbon content by 1.97~3.78 g·kg−1. (2) After vegetation restoration, the relative contents of polysaccharide functional groups in >0.25 mm aggregates were significantly reduced, while the relative contents of aromatic and aliphatic functional groups of organic carbon were significantly increased. The opposite is true for aggregates smaller than 0.25 mm. (3) With the increase in soil depth, the effect of litter on organic carbon gradually decreased, while the effect of root input on the accumulation of inert carbon in deep soil was more lasting. [ABSTRACT FROM AUTHOR]

Soil erosion is mainly affected by the rainfall characteristics and land cover conditions, and soil erosion modelling is important for evaluating land degradation status. The revised Universal Soil Loss Equation (RUSLE) have been widely used to simulate soil loss rate. Previous studies usually considered the general rainfall characteristics and direct effect of runoff with the event rainfall erosivity factor (Re) to produce event soil loss (Ae), whereas the fluctuation of rainfall intensity within the natural rainfall profile has rarely been considered. In this study, the relative amplitude of rainfall intensity (Ram) was proposed to generalize the features of rainfall intensity fluctuation under natural rainfall, and it was incorporated in a new Re (Re=RamEI30) to develop the RUSLE model considering the fluctuation of rainfall intensity (RUSLE-F). The simulation performance of RUSLE-F model was compared with RUSLE-M1 model (Re=EI30) and RUSLE-M2 model (Re=QREI30) using observations in field plots of grassland, orchard and shrubland during 2011–2016 in a loess hilly catchment of China. The results indicated that the relationship between Ae and RamEI30 was well described by a power function with higher R2 values (0.82–0.96) compared to QREI30 (0.80–0.88) and EI30 (0.24–0.28). The RUSLE-F model much improved the accuracy in simulating Ae with higher NSE (0.55–0.79 vs −0.11∼0.54) and lower RMSE (0.82–1.67 vs 1.04–2.49) than RUSLE-M1 model. Furthermore, the RUSLE-F model had better simulation performance than RUSLE-M2 model under grassland and orchard, and more importantly the rainfall data in the RUSLE-F model can be easily obtained compared to the measurements or estimations of runoff data required by the RUSLE-M2 model. This study highlighted the paramount importance of rainfall intensity fluctuation in event soil loss prediction, and the RUSLE-F model contributed to the further development of USLE/RUSLE family of models.

[Objective] To explore the effectiveness of the Revised Universal Soil Loss Equation (RUSLE) model in simulating soil erosion on slope surfaces during vegetation restoration in the Loess Plateau. [Methods] This study utilized rainfall-runoff and sediment data from ten runoff plots in Ansai Fangta small watershed in northern Shaanxi Province during 2016—2022. Utilizing various commonly used algorithms for RUSLE model factors specific to the Loess Plateau, a total of 144 combinations of factors were simulated to estimate soil erosion on restored slopes. The Nash-Sutcliffe efficiency coefficient (NSE) and root mean square error (RMSE) were used to evaluate the effectiveness of the model simulations. [Results] The results indicated that the simulated soil erosion on restored slopes using the 144 factor combinations ranged from -38.47 to 0.19 for NSE and from 1.92 to 12.65 t/(hm2·a) for RMSE, suggesting limited model performance. The selected algorithms for RUSLE model factors appeared to be inadequate for assessing soil erosion on slopes undergoing vegetation restoration. Further improvements are needed for the individual factors within the RUSLE model. When applying RUSLE model to simulate soil erosion on restored slopes in the Loess Plateau, it is recommended to utilize data with high temporal resolution to reduce errors in calculating the R-factor, and comprehensively consider the effects of soil physical and chemical properties such as soil organic matter content, soil particle size and aggregate structure and bulk density on K-factor, and the the effects of vegetation coverage, vegetation height, litter, and biological crust and C-factor, full consider to slopes steeper than 10° in refining the LS-factor. [Conclusion] The RUSLE model is not well-suited for simulating soil erosion in the context of vegetation restoration on abandoned slopes in the Loess Plateau.This study provides some reference for the research and development of soil erosion model and the application of RUSLE model on the slope of vegetation restoration in the Loess Plateau.

The implementation of the Grain for Green Project has increased vegetation coverage and provided suitable habitats and food resources for soil fauna, thereby promoting the development of soil faunal communities. Studying seasonal variations in soil fauna communities in different vegetation areas can improve our understanding of the mechanisms that drive soil fauna recovery. We selected five typical artificially restored vegetation habitats, including Populus simonii (POS), Pinus tabulaeformis (PIT), Caragana korshinskii (CAK), Stipa bungeana (STB), and Medicago sativa (MES), and one farmland (Zea mays, FAL) habitat on the Loess Plateau. In this study, soil fauna communities and environmental factors were investigated during spring (May), summer (August), and autumn (November). Among the habitats, the STB habitat had the largest seasonal variation in soil faunal density (from 1173 ind·m−2 in May to 10,743 ind·m−2 in August), and the FAL habitat had the smallest (from 2827 ind·m−2 in August to 5550 ind·m−2 in November). Among the restored vegetation habitats, Acarina (44.89–88.56%) had the highest relative abundance of all taxa. The redundancy analysis (RDA) results showed that among the factors driving seasonal variation in soil animal communities, temperature (47.41%) was the most important, followed by precipitation (22.60%). In addition, the dominant groups, Acarina and Collembola, played an influential role in seasonal variations in soil faunal density. Temperature mainly determined the seasonal variations in soil faunal communities. Seasonal factors should be considered when conducting soil fauna research, as they contribute to biodiversity conservation and regional ecological management in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Vegetation restoration is an effective measure to cope with global climate change and promote soil carbon sequestration. However, during vegetation restoration, the turnover and properties of carbon within various aggregates change. The effects of plant source carbon input on surface soil and subsurface soil may be different. Thus, the characteristics of carbon components in aggregates are affected. Therefore, the research object of this study is the Robinia pseudoacacia forest located in 16–47a of the Loess Plateau, and compared with farmland. The change characteristics of organic carbon functional groups in 0–20 cm, 20–40 cm, and 40–60 cm soil layers were analyzed by Fourier near infrared spectroscopy, and the relationship between the chemical structure of organic carbon and the content of organic carbon components in soil aggregates was clarified, and the mechanism affecting the distribution of organic carbon components in soil aggregates was revealed in the process of vegetation restoration. The results show the following: (1) The stability of surface aggregates is sensitive, while that of deep aggregates is weak. Vegetation restoration increased the surface soil organic carbon content by 1.97~3.78 g·kg−1. (2) After vegetation restoration, the relative contents of polysaccharide functional groups in >0.25 mm aggregates were significantly reduced, while the relative contents of aromatic and aliphatic functional groups of organic carbon were significantly increased. The opposite is true for aggregates smaller than 0.25 mm. (3) With the increase in soil depth, the effect of litter on organic carbon gradually decreased, while the effect of root input on the accumulation of inert carbon in deep soil was more lasting.

[Objective] The changes in herbaceous plant diversity and the factors influencing those changes after revegetation at a gully head were studied in order to provide a relevant foundation for the assessment of the benefits of soil and water conservation in the loess tableland. [Methods] Herbaceous plant diversity at a gully head was measured and soil property indexes related to the topsoil (0—10 cm and 10—25 cm) were determined by selecting grassland gully heads with vegetation restoration periods of 5, 13, 18, and 22 years in the Baicao Tableland. Farmland was used as the control. [Results] The Patrick richness index initially increased with increasing number of vegetation restoration years, and then stabilized. The Shannon-Wiener index showed a continuously increasing trend, and the Shannon-Wiener index values in 18 and 22 years of vegetation restoration were greater than at 13 years of restoration. However, the differences were not significantly different. The Pielou evenness index exhibited a fluctuating trend of increasing, and then decreasing, then increasing again, reaching a maximum value (0.89) in 22 years of recovery. The soil bulk density in both the 0—10 cm and 10—25 cm layers reached a minimum value in 22 years of recovery, with significant decreases of 13.1% and 17.8%, respectively, compared with values observed for farmland (p

[Objective] Elucidating the influence of long-term returning farmland to forest, shrubland, and grassland on soil hydrophysical properties on the Loess Plateau is conducive to improving soil hydrology research and providing a theoretical basis for the subsequent ecological restoration of the Loess Plateau. [Methods] Through sampling analysis and double-ring infiltrometer test, the soil hydrophysical properties such as soil organic matter, bulk density, porosity, soil moisture and infiltration capacity of different vegetation restoration types were analyzed. [Results] Vegetation restoration had a significant impact on soil physical properties（p＜0.05）, and the resulting changes were most obvious in the 0—40 cm soil layer. The content of organic matter, porosity and the stability of water-stable aggregates significant increased, the soil bulk density decreased significantly. Converting farmland to forest, shrubland, and grassland enhanced soil infiltration capacity. Compared with farmland, the initial infiltration of Suide and Shenmu grassland increased by 50% and 31%, respectively; the stable infiltration rates of grassland, shrubs and forest in Suide area increased by 76%, 11% and 19%, respectively; those in Shenmu area increased by 53%, 128% and 58%, respectively. Soil stable infiltration and average infiltration were significantly negatively correlated with bulk density（p＜0.05）, and significantly positively correlated with total porosity, capillary porosity（p＜0.05） and organic matter content（p＜0.05）. [Conclusion] Vegetation restoration has a significant effect on soil hydrophysical properties, soil infiltration performance has been significantly improved, and organic matter content, bulk density and porosity have significant effects on infiltration performance. [ABSTRACT FROM AUTHOR]

Given the developmental program outlined in United Nations Sustainable Development Goal 15 (Life on Land) and the to effectively address the challenge of biodiversity decline while mitigating the adverse effects of climate change, particularly drought, on terrestrial forest ecosystems, a fundamental reorientation of global forest restoration paradigms is warranted. It is imperative to move beyond a narrow emphasis on expanding forest area and instead prioritize the enhancement of biodiversity and functional attributes within these ecosystems. However, the differential response mechanisms of forest ecosystem functional communities and main plant functional types (PFTs) to environmental factors, especially soil and topography, remains unclear, especially at plant level. Here, we divided the functional communities of 93 sites in the study area into seven groups through Two‐way indicator species analysis (TWINSPAN), and studied the different functional communities, namely dynamic succession, species richness, and PFT compositional differences. We also analyzed the various PFTs and functional community response mechanisms to soil and topographic factors using canonical correspondence analysis (CCA). The main results were as follows: (1) With the successional stages of PFTs, vegetation diversity across multiple functional communities inceased, tree and shrub proportions and importance increased, while herbs decreased. (2) From the arid and barren areas (i.e., G2), to the humid and fertile areas (i.e., G6 and G7), various compositional PFT differences, and their responses to soil and topographic factors, were found, namely, xerophytic, annual and biennial species gradually changed to mesophytic, hygrophytic, and perennial species (richness increased 6.94 ~ 27.33%, important value (IV) increased 8.73 ~ 29.45%) for shrubs and herbs. (3) Functional communities in various successional stages display distinct sensitivities to soil and topographic factors, as evidenced by a notable increase in the richness and IV of deciduous broad‐leaved tree species, rendering their communities more responsive to SOC and AS, whereas evergreen coniferous trees (e.g., Pinus tabuliformis Carr.) were sensitive to altitude (AL) and exhibited a tendency to transition from plantations to natural secondary forests predominantly at higher altitudes (above 1200 m). Our findings suggest that site conditions influence scenarios, and that different PFT responses and adjustments to soil and topography factors affect whole functional community dynamic succession processes, which can profoundly impact forest ecosystem function predictions based on PFT changes in the Loess Plateau of China. [ABSTRACT FROM AUTHOR]

[Objective] The effects of different long-term vegetation restoration types on differences of soil surface infiltration and water storage in the loess gully region of Western Shanxi Province were studied in order to screen and enhance the ecological benefits of natural vegetation restoration as well as artificial vegetation restoration in Loess Plateau in the future, thereby providing a scientific reference for an in-depth understanding of the ecological benefits of vegetation restoration. [Methods] We measured infiltration in the top 30 cm of soil under four types of restored vegetation (Pinus tabulaeformis pure forest, Robinia pseudoacacia pure forest, Platycladus orientalis pure forest, natural forest). We also measured soil physical and chemical properties such as soil bulk density and mechanical composition, and monitored soil moisture dynamics in the four types of restored vegetation in the loess hilly-gully region. We calculated soil water storage and analyzed differences due to vegetation type, and conducted correlation analysis and principal component analysis. Three soil infiltration models were then fitted to the measured processes in order to compare their suitability for use in vegetation restoration areas of the loess hilly-gully region. Differences in soil infiltration and water storage between different vegetation restoration types were also determined. We also evaluated the ability of the models to supplement and improve the surface soil water infiltration pattern under different vegetation restoration types in the Loess Plateau region. [Results] ① Natural forest was more effective in improving the physical properties of the 0—30 cm surface soil compared with pure planted forests. Natural forest had greater water content and better water retention, and planted forests were more effective in improving the infiltration capacity of the soil in the study area compared with natural forest. ② The stable infiltration rate of soil under different vegetation types from largest to smallest followed the order of natural forest > Robinia pseudoacacia pure forest > Pinus tabulaeformis pure forest > Platycladus orientalis pure forest (for the 0—10 cm layer); Pinus tabulaeformis pure forest > Robinia pseudoacacia pure forest > Platycladus orientalis pure forest > natural forest (for the 10—20 cm layer); Pinus tabulaeformis pure forest > Robinia pseudoacacia pure forest > Platycladus orientalis pure forest > natural forest (for the 20—30 cm layer); ③ The Horton model performed better than the Kostiakov and Philip models in fitting soil infiltration in the study area (R2=0.94), and will be helpful in better understanding the soil infiltration pattern in the study area. ④ The main physical characteristics affecting soil infiltration rate were soil bulk density, soil organic carbon, soil water storage capacity and soil clay particle content. [Conclusion] There were significant differences in soil infiltration properties due to different long-term vegetation restoration types. Compared with long-term replanted forests, the long-term natural forest had greater vegetation restoration benefits, and could effectively improve soil quality and enhance soil water retention capacity for the Loess Plateau.

The implementation of the Grain for Green Project has increased vegetation coverage and provided suitable habitats and food resources for soil fauna, thereby promoting the development of soil faunal communities. Studying seasonal variations in soil fauna communities in different vegetation areas can improve our understanding of the mechanisms that drive soil fauna recovery. We selected five typical artificially restored vegetation habitats, including Populus simonii (POS), Pinus tabulaeformis (PIT), Caragana korshinskii (CAK), Stipa bungeana (STB), and Medicago sativa (MES), and one farmland (Zea mays, FAL) habitat on the Loess Plateau. In this study, soil fauna communities and environmental factors were investigated during spring (May), summer (August), and autumn (November). Among the habitats, the STB habitat had the largest seasonal variation in soil faunal density (from 1173 ind·m−2 in May to 10,743 ind·m−2 in August), and the FAL habitat had the smallest (from 2827 ind·m−2 in August to 5550 ind·m−2 in November). Among the restored vegetation habitats, Acarina (44.89–88.56%) had the highest relative abundance of all taxa. The redundancy analysis (RDA) results showed that among the factors driving seasonal variation in soil animal communities, temperature (47.41%) was the most important, followed by precipitation (22.60%). In addition, the dominant groups, Acarina and Collembola, played an influential role in seasonal variations in soil faunal density. Temperature mainly determined the seasonal variations in soil faunal communities. Seasonal factors should be considered when conducting soil fauna research, as they contribute to biodiversity conservation and regional ecological management in the Loess Plateau.

The effects of vegetation restoration on soil moisture dynamics and nutrient content have been widely studied; however, the knowledge on variation in rainfall redistribution and soil nitrogen component characteristics remain limited, particularly with respect to their relationship in restored ecosystems. Therefore, the characteristics of plant community structure, rainfall redistribution, and soil nitrogen components from farmland and Robinia pseudoacacia (RP) plantations of four restoration ages (12, 20, 30, and 45 a) were investigated and measured in the Wuliwan watershed in the Loess Plateau, China. The results showed that changes in plant community structure affected the rainfall redistribution processes. The throughfall and moisture entering the soil (MES) had the largest proportions (79.50 % and 60.25 %) in the initial and second distributions of atmospheric rainfall, respectively. With the increase in restoration age, the content of soil total nitrogen (STN), soil nitrate nitrogen (SNN), soil soluble total nitrogen (SSTN), soil soluble organic nitrogen (SSON), and soil soluble inorganic nitrogen (SSIN) all increased with restoration age in the upper soil (0–40 cm), fluctuated in the middle soil (40–100 cm), and increased and then decreased in the deeper soil (100–200 cm). In addition, the vegetation restoration process can indirectly affect soil nitrogen content and distribution patterns by affecting the rainfall redistribution process. In the upper soil, litter interception (LI) had a significant effect on STN by affecting SSIN and SSON. In the middle soil, both LI and MES had significant effects on STN through SSIN and SSON, respectively. In the deeper soil, LI had no significant effect on any nitrogen component, whereas MES had a significant effect on STN by affecting SSIN. Overall, this study indicates that RP plantation restoration has the potential to transform rainfall redistribution and soil nitrogen distribution, providing an important reference for the reciprocal feedback relationship between water and nitrogen.

Investigating the impact of vegetation restoration on changes in runoff generation patterns is essential for understanding watershed hydrology and soil erosion processes in a changing environment. This study examined the influence of vegetation restoration to the runoff generation patterns in a typical small watershed in the gullied rolling loess area through stratified in-situ double-ring infiltration tests and the analysis of the measured flood process before and after vegetation restoration. The results show that a) vegetation restoration has significantly enhanced soil infiltration capacity, resulting in varying degrees of increase in the infiltration rate at different depths (0-60 cm). Vegetation restoration has increased the difference in infiltration capacity between the surface soil and the 10 cm layer. b) Soil infiltration capacity increases significantly with a decrease in soil bulk density and an increase in porosity. Vegetation restoration can affect soil infiltration and runoff generation processes by reducing soil bulk density and increasing porosity. c) After vegetation restoration, the peak flow, runoff depth, runoff coefficient and surface runoff ratio of storm events in the small watershed are decreased, while subsurface runoff is increased. The runoff generation pattern is shifted from excessive infiltration to saturated runoff. These findings indicate that vegetation restoration has an impact on the runoff generation patterns and provide a scientific basis for further studying soil hydrological processes in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vegetation restoration is an important means for regional climate change mitigation and terrestrial carbon sequestration. However, large‐scale vegetation restoration in arid and semiarid regions can excessively consume local water resources, thus threatening regional water supply safety. To explore the impact of vegetation restoration on the water–carbon relationship in the Loess Plateau in China before and after the implementation of the Grain‐for‐Green Program (GfGP), the regional hydro‐ecological simulation system (RHESSys) model was used to simulate the temporal and spatial evolution of key variables of the water cycle, including the actual evapotranspiration (ET) and the surface runoff (Rs), and that of the carbon cycle, including the net primary productivity (NPP) and the total carbon density (TC). In addition, statistical methods were applied to analyze the interaction between water and carbon cycles. Results show that the RHESSys model is capable of simulating the key ecohydrological elements. In the period of 1990–2019, ET and NPP both showed significant increasing trends at rates of 8.9 mm yr−1 and 6.9 g C m−2 yr−1, respectively. The TC also had a slightly increasing trend, with rates of 0.04 t C hm−2 yr−1 (land‐use in 1995), 0.07 t C hm−2 yr−1 (land‐use in 2005), and 0.08 t C hm−2 yr−1 (land‐use in 2015). In contrast, Rs decreased at the rate of 0.35 mm yr−1. As for spatial distribution, in the middle and southeastern parts of the Yanhe River basin with the vegetation well‐restored, ET, NPP, and TC showed significant increasing trends, while the Rs showed a decreasing trend. ET was also found to have a positive correlation with NPP and TC, while the Rs has a negative correlation with NPP and TC. Moreover, the correlation of Rs‐NPP and Rs‐TC was found to increase after the implementation of the GfGP, which indicates the reinforcing effect of vegetation restoration on the water–carbon trade‐off relationship. Therefore, it is critical to coordinate and regulate the interaction between water consumption and runoff in the context of vegetation restoration in the Yanhe River basin, as well as to promote the synergy between regional ecological restoration and social economic development for water security. [ABSTRACT FROM AUTHOR]

Large-scale vegetation restoration can significantly affect catchment hydrology. Assessing the impact of vegetation restoration on hydrological regimes is important for water resource management. We chose three less-forested catchments (LFCs, forested area <30%) undergoing major vegetation restoration, i.e., Wuqi, Zhidan, and Liujiahe, and two forested reference catchments (FCs, forested area >77%) that have had secondary forests for more than 150 years, i.e., Zhangcunyi and Huangling, of the Beiluo River basin located in the Loess Plateau (LP) to compare and analyze the stationary and variation characteristics of streamflow and its components from 1958 to 2019. Results show that the mean annual streamflows were 25.07~34.21 and 21.62~48.02 mm in the LFCs and FCs, respectively. The mean streamflow in the LFCs decreased by 50% on average from before the year 2000 to after. The decreasing trend of high flows and increasing trend of low flows is represented in the daily flow duration curves of the LFCs. The result of baseflow separation shows that the average percentages of baseflow in the streamflow were 31.89~43.36% in the LFCs and 58.23~60.14% in the FCs. The Mann–Kendall tests showed significant decreasing trends in annual streamflow (−0.27~−0.70 mm/a) and stormflow (−0.29~−0.64 mm/a) in the LFCs from 1958 to 2019, while the baseflow exhibited increasing trends except for in the Zhidan catchment. The seasonal streamflow and stormflow showed significant decreasing trends in the summer and non-flood season, while the winter and non-flood season's baseflow increased in LFCs. In FCs, however, the streamflow and its components showed only slight fluctuations over the study period in annual trends, decadal variability, and seasonal trends over the study period, suggesting that FCs have stable hydrological regimes. These results indicate that 20 years of large-scale vegetation restoration greatly influenced hydrological regimes by reducing stormflow and increasing baseflow, and played an important role in streamflow regulation. Conversely, areas with well-preserved vegetation can effectively mitigate the effects of weather and other factors on runoff with stable hydrological regimes. This study can help vegetation restoration and water resource management on the LP. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Soil & Water Conservation is the property of Bulletin of Soil & Water Conservation Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Large-scale vegetation restoration has been performed to improve the fragile ecological environment of the Loess Plateau in the last decades. At present, the effects and mechanism of long-term vegetation restoration on soil properties in ecosystems require further exploration to provide a reference for rational ecological construction. Hence, we investigated the differences in vegetation attributes and soil properties between three typical vegetation types (Pinus tabulaeformis plantation forest, PTPF; Robinia pseudoacacia plantation forest, RPPF; natural secondary forest, NSF) after long-term (30–40 years) vegetation restoration in the western Loess Region, China. Our results showed that (1) the arborous synusia biomass of the plantation forests was twice that of NSF, whereas NSF had almost 50% higher near-surface synusia biomass than the plantation forests; (2) the soil nutrient contents of the plantation forests were lower (30%) than those of NSF; (3) the soil bulk density, organic matter, total nitrogen, and phosphorus were positively related to arborous and shrub synusia biomass; (4) the coupling effects of four biological synusiae (with the contribution of 47.67%) were the dominant factors affecting soil physicochemical properties. Natural forests have the better vegetation attributes and soil properties than plantation forests, indicating that the close-to-nature restoration should be considered in ecological restoration. These findings can provide scientific support and theoretical basis for reforestation and ecological restoration in the Loess Plateau region and similar areas in the future.

Effects of 15-year vegetation restoration on organic carbon content of soil aggregates in the Wangmaogou Watershed in China were evaluated. Major land use types include grassland, forestland, shrubland, and sloping cropland. Soils from depths of 0–20, 20–40, and 40–60 cm were collected from each study site. Soil aggregates were divided into macro (5–2 mm), small (2–0.25 mm), and micro (< 0.25 mm) aggregates. Vegetation restoration improved the organic carbon content of soil aggregates, which was positively correlated with soil aggregate stability (R = 0.44 and 0.53 for the mean weight diameter and geometric mean diameter, respectively) and negatively correlated (R = – 0.57) with the soil erosion rate (measured by 137Cs tracer). The levels of macro- and small- aggregates in vegetated lands were more than double than those in sloping cropland. Following vegetation restoration, the dominant soil aggregates in the 0–20 cm soil layer were transformed from micro-aggregates to macro-aggregates. The mean weight diameter and geometric mean diameter of soil aggregates from vegetated land were significantly higher than those of sloping cropland. Vegetation restoration increased the organic carbon content of soil aggregates by improving the stability of soil aggregates and reducing soil erosion. [ABSTRACT FROM AUTHOR]

Vegetation disturbance during infrastructure construction can cause serious ecological problems, especially in fragile environments. The Northern Shaanxi Loess Plateau is an oil industry base in China with a fragile ecosystem. Vegetation restoration on the disturbance area can effectively control soil erosion and ensure the safety of oil pipelines. In the linear disturbance area, surrounding vegetation traits and topography may play an important role in vegetation restoration by influencing propagules and recruitment microsites. This study aimed to reveal the influence of vegetation type and topography on vegetation restoration in the disturbance area along the oil pipeline. The results showed that 89 species were recorded, and they belonged to 30 families and 74 genera. These species were mainly native herbaceous plants, especially perennial herbs. The species number and species diversity index in the disturbance area had a positive relationship with the undisturbed area. The lateral undisturbed vegetation type and species reproductive strategies influenced the vegetation restoration in the disturbance area. The species that produce a large number of seeds or regenerate by rhizome recolonized quickly in the disturbance area. However, the shrubs and arbor species that need seeds for recruitment will take a long time for restoration. The topographic factor had an obvious influence on the vegetation restoration and species diversity in the disturbance areas. On the sunny and steep slopes, vegetation restoration was difficult and slow, and artificial measures were needed to control soil erosion and maintain soil moisture to help seedling recruitment and survival. [ABSTRACT FROM AUTHOR]

As soil structural units, soil aggregates are crucial in soil total nitrogen and organic carbon sequestration, which has been gradually discovered by scholars. However, how aggregates affect the storage of soil organic carbon and soil total nitrogen pools through aggregate proportion and their carbon and nitrogen content, remain unclear. Here, we examined soil aggregate composition, and the characteristics of aggregate-associated organic carbon and total nitrogen under different recovery years (15, 30, and 45 years) to explore the contribution in different sizes aggregates to soil carbon and nitrogen accumulation and its driving factors across different vegetation types of Natural grasslands (NG), Caragana korshinskii plantations (CK), and Robinia pseudoacacia plantations (RP) on the loess hilly areas. The results indicate that microaggregates dominated all soils, with the average proportions of 44.91 % in NG, 44.47 % in CK, and 42.19 % in RP. Yet, with the increase of recovery years, the proportion of microaggregates reduced and the proportion of macroaggregates rised. After vegetation restoration, the contents of carbon and nitrogen in soil and aggregates were increased. In addition, macroaggregate contributed more than 71.5 %, 67.0 %, and 67.9 % to organic carbon and total nitrogen stocks in NG, CK, and RP, respectively. The result that highlights the fact that macroaggregate is critical drivers of soil organic carbon and total nitrogen accumulation in different vegetation types. The growing percentage of macroaggregates was a key factor in the accumulation of soil organic carbon and total nitrogen stocks in NG, while the increasing percentage of macroaggregates and their associated carbon and nitrogen contents jointly led to an explicit increase in soil organic carbon and total nitrogen stocks in CK and RP. Overall, our findings revealed the soil organic carbon and total nitrogen accumulation process mediated by macroaggregates during vegetation recovery period on the Loess Plateau, providing a scientific basis for a deeper understanding of the potential of soil organic carbon and total nitrogen sequestration during the vegetation restoration in fragile habitats. [Display omitted] • Revegetation decreased microaggregate and increased macroaggregate proportions. • C and N contents in bulk soil and aggregates were promoted after restoration. • Macroaggregates plays a key role in C and N accumulation in all vegetation types. • Increased macroaggregate proportion promoted C and N accumulation in NG. • Increased C and N contents and proportion of macroaggregate promoted C and N accumulation in CK and RP. [ABSTRACT FROM AUTHOR]

China's Grain‐for‐Green Program (GFGP) motivates conversion from steep slope cropland to forest or grassland to reverse serious land degradation. However, impoverished farmers potentially persist with inefficient slope farming for survival, thereby threatening the sustainable GFGP efforts. Consequently, a strategy for balancing farming and vegetation restoration from a spatial optimization perspective is necessary. Here, we selected two catchments with high and low agricultural intensity in the loess hilly and gully regions for a case study. Spatial analysis and binary logistic regression models were used to clarify the effects of topography, accessibility, and location factors on cropland distribution and explore spatially optimized cropland distribution. The results show that steep slope cropland is still widespread, of which cropland with slopes >15° accounts for 46.7% and 34.7% in the two catchments, respectively. Residences and roads significantly impact steep slope cropland distribution, and around 80% of cropland with slopes >15° is distributed within 200 m from residences or 100 m from roads. In cropland redistribution scenarios, cropland with slopes >25° and >15° can be redistributed to gentler slopes while maintaining cropland areas in catchments with high and low agricultural intensity. Correspondingly, 38.8% and 81.2%, respectively, of simulated cropland on gentle slopes needs optimized attributes such as accessibility in order to be priorities of farmers. Our research provides new insights into GFGP strategies for steep slope cropland restoration in catchments with different agricultural intensities, thereby advancing sustainable farming and vegetation restoration in China's mountainous regions. [ABSTRACT FROM AUTHOR]

Plant secondary succession is a very effective approach for the rejuvenation of degraded ecosystems. In order to comprehend alterations and driving mechanisms of soil bacterial communities under secondary succession of old-field and reveal their subsequent impacts on the decomposition and accumulation of soil organic carbon (SOC) and nitrogen (SON), we investigated changes in soil bacterial communities following ~160 years of old-field succession on the Loess Plateau of China through analyses of quantitative polymerase chain reaction (qPCR) and Illumina MiSeq DNA sequencing of 16S rRNA genes. Our results revealed that subsequent to secondary succession of old-field, soil bacterial abundance progressively increased, while bacterial richness and diversity significantly decreased. Principal component analysis and Bray–Curtis similarity index showed that bacterial community composition gradually shifted following old-field succession. Specifically, the relative abundances of Proteobacteria, Rokubacteria, and Verrucomicrobia progressively increased, while Actinobacteria and Firmicutes slightly decreased following old-field succession. The most enriched of Proteobacteria (e.g., Rhizobiales, Xanthobacteraceae, Gammaproteobacteria, Bradyrhizobium, Rhizobiaceae, and Mesorhizobiur) were found in a climax forest, while Chloroflexi and Gemmatimonadetes had the lowest relative abundances. Further, the most enriched members of Actinobacteria, including Geodermatophilaceae, Frankiales, Blastococcus, Micrococcales, Micrococcacea, Propionibacteriales, Nocardioidaceae, Nocardioide, and Streptomycetaceae, were exhibited in the farmland stage. Our results suggested that secondary succession of old-field greatly modified soil bacterial communities via the transformation of soil nutrients levels, altering plant biomass and soil physiochemical properties. Soil bacterial community composition was transformed from oligotrophic groups to copiotrophic Proteobacteria following old-field succession, which may promote SOC and SON accumulation through increasing the utilization of labile organic carbon (C) and nitrogen (N), while decreasing decomposition of recalcitrant organic C and N from the early- to late-successional stages. [ABSTRACT FROM AUTHOR]

Study region: The Loess Plateau, China. Study focus: Land-use and rainfall characteristics are two crucial influencing factors that affect the surface runoff and soil loss process; however, less attention has been paid to nested watersheds in vulnerable geo-ecosystems. Here we analyzed rainfall characteristics impacts on runoff and sediment in one of the nested watersheds, which contains six sub-watersheds with different land uses. According to rainfall amount, duration, and maximum rainfall intensity within 30 min (I30), 180 rainfall events during 2004–2019 were categorized into four types using K-means clustering method, and different hydrological years were distinguished. New hydrological insights for the study region: The runoff coefficient and sediment yield under the rainfall regime Ⅰ (little precipitation, moderate duration of precipitation, low intensity of precipitation) were the lowest; under the rainfall regime Ⅳ (high precipitation, short duration of precipitation, high intensity of precipitation), these values were the largest. The average runoff coefficient among the six sub-watersheds analyzed varied as follows: farmland watershed > farming-pastoral watershed > closed watershed > secondary forest watershed > mixed forest watershed > plantation watershed. The closed watershed had the lowest average sediment yield, while the farming-pastoral watershed showed the highest one. In addition, the runoff coefficient and sediment yield also changed differently in various hydrological years. The results of this study suggest that natural restoration measures are the optimal choice for coordinating the relationship between surface runoff and sediment yield. Enhanced long-term monitoring is needed to accurately describe watershed processes.

The impacts of vegetation restoration on the soil erosion have been widely elucidated in the semi-arid regions. However, the magnitude of soil erosion on abandoned sloping farmland still remained unclear and their responses to vegetation succession were rarely addressed. The main objective of this study is to determine the magnitude of soil erosion along vegetation succession and explore the impact of vegetation succession on soil erosion from abandoned sloping farmland. Field observations were employed to monitor the rainfall, runoff, and soil erosion of seven sloping farmland plots with different abandoned ages and bare land from 2015 to 2019. The results indicated that the annual runoff depth and soil erosion modulus of vegetation types were in the range of 0.46 to 5.49 mm·a−1 and 1.3 to 24.5 t·km−2·a−1, respectively. The vegetation effectively reduced the annual surface runoff and soil erosion with reduction of 73.8% to 97.8% and 98.0% to 99.9% as opposed to bare land. However, there were no significant differences in runoff and soil erosion for different vegetation types along succession. The largest event of vegetation types contributed to 38.7%–44.1% of the annual runoff and 42.5%–66.3% of the annual soil erosion, respectively. Vegetation restoration considerably alleviated the contribution of largest erosive event to annual soil erosion. The relationships between soil erosion, runoff and rainfall factors could be fitted well by linear functions, and the performances of regression models in predicting runoff were more satisfactory compared to predicting soil erosion. The Artemisia gmelinii (Agm) + Stipa bungeana (Sb) optimized the trade-off between sediment reduction and runoff maintenance, which should be selected as the suitable vegetation types to achieve the sustainability of socio-ecological systems. [ABSTRACT FROM AUTHOR]

Although the microbial fixation of CO 2 is a key process in regulating soil carbon cycling, the effects of vegetation type on microbial carbon-fixing pathways and their driving factors in soils have yet to be sufficiently established. In this study, based on macro-genome sequencing and other analytical methods, we sought to determine the soil physicochemical properties, soil organic carbon contents, carbon-fixing microorganisms, and carbon-fixing genes in areas of farmland (FL), grassland (GL). Robinia pseudoacacia (RP), Caragana korshinskii (CAK), and Prunus sibirica (PS) in the Wuliwan watershed of the Loess Plateau region of China. Our findings revealed that the organic carbon contents of the assessed soils increased in the following order: FL < GL∼PS < CAK < RP (P < 0.05). Re-vegetation-based restoration was found to enhance soil organic carbon pool stability. Compared with farmland soil, the proportions of recalcitrant organic carbon had increased by 6 % and 9 % in the soil at sites that had undergone restoration with C. korshinskii and R. pseudoacacia respectively. Among the identified carbon fixation pathways, the DC/4-HB cycle had the highest relative abundance of 25.10–25.52 %. The dominant groups of carbon-fixing microorganisms were identified as Actinobacteria and Proteobacteria , accounting for over 60 % of the total abundance. Furthermore, analysis based on a partial least squares path model revealed labile organic carbon and soil nitrate nitrogen as the primary drivers of carbon fixation pathways. Collectively, our findings in this study provide evidence to indicate that restoration of vegetation on the Loess Plateau can contribute to increases in soil organic carbon content and stability and the abundance of carbon-fixing microorganisms, with R. pseudoacacia and C. korshinskii having the most significant effects in this regard. These findings have important implications for restorative vegetation carbon pool management and provide additional perspectives for understanding global carbon cycling. • Afforestation increases soil carbon content and proportion of recalcitrant organic carbon. • The DC/4-HB cycle had the highest relative abundance. • Actinobacteria and Proteobacteria are the main phyla of CO 2 fixing. • Soil labile organic carbon and nitrate nitrogen are the key factors driving microbial CO 2 fixation. [ABSTRACT FROM AUTHOR]

Assessing ecosystem services (ESs) is vital for the environment development. This study explored the variation characteristics of ESs under the restoring vegetation since the Grain for Green Project (GFGP) in Jinghe Watershed, which is a typical watershed experiencing severe soil erosion in the Loess Plateau of China. Herein, the fractional vegetation cover (FVC) is selected as an indicator of the changes in vegetation restoration from 2000 to 2020. Simulations of ESs are based on the Soil and Water Assessment Tool (SWAT), Carnegie Ames-Stanford Approach (CASA) model, Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST). This paper analyzed the spatiotemporal heterogeneity in vegetation coverage and the response of vegetation coverage to ESs in the Jinghe Watershed with Mann-Kendall test, Pearson correlation coeffificient R and the gray relational analysis (GRA). The results showed that: (1) Since the implementation of the GFGP, the area of forests and grassland has increased significantly. The proportion of vegetation restoration area was 95.15 %; (2) At the whole watershed scale, vegetation restoration and soil conservation (SC), water yied (WY), net primary production (NPP) and habitat quality (HQ) were synergistic relationships, while focusing on the sub-watershed scale, vegetation restoration and SC and HQ were transformed into trade-off relationships in some sub-watershed. (3) Vegetation restoration in the Jinghe Watershed had positive effects on SC, WY, NPP, and HQ. The order of relevance with vegetation restoration was: SC > HQ > NPP > WY, indicating that vegetation restoration in the Jinghe Watershed has the highest closeness to SC. This study showed that since the implementation of the GFGP, vegetation coverage in the Jinghe Watershed has significantly restored, which has promoted the improvement of ESs.

[Display omitted] • Vegetation restoration on the Loess Plateau increased the extend and depth of infiltration. • Vegetation restoration on the Loess Plateau has altered the pattern of uniform water infiltration, resulting in a distinct preferential flow in the infiltration processes. • Mixed-mode afforestation is better than single-dominant-species afforestation to promote precipitation infiltration. • The preferential flow phenomenon was more pronounced in the natural secondary forest than that in plantation forests. In order to improve the fragile ecological environment, the Loess Plateau region of China has implemented a large number of long-term forest vegetation restoration projects. Infiltration, as an important part of the hydrological cycle, is also changing with vegetation restoration, and a comprehensive study of these changes is an essential aspect of evaluating the effectiveness of vegetation restoration. In the study, three typical forest vegetation types in the Loess Plateau were selected to investigate and analyse infiltration characteristics and infiltration patterns by staining tracer experiments. The results showed that (1) vegetation restoration increased the extend and depth of infiltration. (2) The extent of infiltration in mixed plantation forest of Pinus tabulaeformis and Robinia pseudoacacia was better than that in pure Pinus tabulaeformis plantation forest. (3) Vegetation restoration resulted in more pronounced preferential flow phenomenon in the infiltration processes. (4) The preferential flow phenomenon was more pronounced in the natural secondary forest than in plantation forests, especially if the amount of infiltrated water was low. (5) The extent of infiltration was mainly influenced by the infiltration water volume, soil water content, and total soil porosity; and the degree of preferential flow development was mainly influenced by the infiltration water volume, soil organic matter, and root distribution. At present, vegetation restoration on the Loess Plateau can play a role in promoting precipitation infiltration, and mixed-mode afforestation is better than single-dominant-species afforestation to fulfil this function of forests. [ABSTRACT FROM AUTHOR]

Coal mining, an important human activity, disturbs soil organic carbon (SOC) accumulation and decomposition, eventually affecting terrestrial carbon cycling and the sustainability of human society. However, changes of SOC content and their relation with influential factors in coal mining areas remained unclear. In the study, predictive models of SOC content were developed based on field sampling and Landsat images for different land-use types (grassland, forest, farmland, and bare land) of the largest coal mining area in China (i.e., Shendong). The established models were employed to estimate SOC content across the Shendong mining area during 1990–2020, followed by an investigation into the impacts of climate change and human disturbance on SOC content by a Geo-detector. Results showed that the models produced satisfactory results (R2 > 0.69, p < 0.05), demonstrating that SOC content over a large coal mining area can be effectively assessed using remote sensing techniques. Results revealed that average SOC content in the study area rose from 5.67 gC·kg−1 in 1990 to 9.23 gC·kg−1 in 2010 and then declined to 5.31 gC·Kg−1 in 2020. This could be attributed to the interaction between the disturbance of soil caused by coal mining and the improvement of eco-environment by land reclamation. Spatially, the SOC content of farmland was the highest, followed by grassland, and that of bare land was the lowest. SOC accumulation was inhibited by coal mining activities, with the effect of high-intensity mining being lower than that of moderate- and low-intensity mining activities. Land use was found to be the strongest individual influencing factor for SOC content changes, while the interaction between vegetation coverage and precipitation exerted the most significant influence on the variability of SOC content. Furthermore, the influence of mining intensity combined with precipitation was 10 times higher than that of mining intensity alone. [ABSTRACT FROM AUTHOR]

The long-term "Grain-to-Green Program" (GGP) on China's Loess Plateau is a major global ecological engineering project which has significantly boosted vegetation renewal. Some studies have found that the rate of restoration is quite rapid during the implementation of ecological engineering, however, the influence of multi-scale climatic conditions on the performance of ecological engineering is unclear. In this study, multiple sources of remote sensing data were used to estimate the dynamics of vegetation structural and functional indicators, water-related local climatic factors, and atmospheric circulation factors. These datasets were also used to detect possible causes for vegetation restoration on the Loess Plateau over the past 20 years. The results show that widespread increases in rates of normalized difference vegetation indexes (NDVI), leaf area indexes (LAI), gross primary production (GPP), and aboveground biomass carbon (ABC) during 2000–2016 were significantly higher than before 2000. GPP was significantly correlated with rainfall and surface runoff on a monthly scale, and there were significant positive correlations between GPP and atmospheric circulation. Our results demonstrate that both vegetation structural and functional indicators rapidly increase, and ecological engineering greatly accelerated vegetation restoration after 2000. Local climatic conditions and atmospheric circulation patterns enhance vegetation growth and impact of ecological engineering. [ABSTRACT FROM AUTHOR]

With years of vegetation restoration and check dam construction on the Loess Plateau, the sediment load of the middle reaches of the Yellow River have decreased sharply; however, the effects of check dam on this decrease of sediment load with such extensive vegetation restoration remains unclear. In order to further clarify the effects of check dam on sediment load reduction under vegetation restoration, we calculated vegetation coverage and check dam index based on multi-source remote sensing data, and calculated sediment reduction rate caused by human activities by Mann-Kendall statistical test and double cumulative curve, then established regression equations incorporating the check dam index and the sediment reduction rate using data from different geomorphic regions with different vegetation coverages. The results showed that sediment load in the Hekou-Longmen region and its 17 tributaries decreased significantly every year, and the change in sediment load could be divided into 3 typical periods: the base period (P1), the period mainly impacted by check dam construction (P2) and the period with comprehensive impact of check dam construction and vegetation restoration (P3). Compared with sediment load of the tributaries during P1, the sediment load decreased by 60.96% during P2 and by 91.76% during P3. Compared with the contribution of human activities to the reduction in sediment load in P2, the contribution of human activities in P3 increased significantly, while that of precipitation decreased slightly. The sediment reduction effect of check dams is greater in basins with low vegetation coverage than in basins with high vegetation coverage. There are differences in sediment reduction effect of vegetation restorations in different geomorphic regions, and the effect of vegetation restoration alone have certain upper limits. Such as, the upper limit of sediment reduction rate of vegetation restoration for rivers flowing through the sandstorm region is 47.86%. Hence, only combined the construction of check dam with vegetation restoration can it achieve more significant sediment reduction benefit and control soil erosion more effectively.

It is of great significance to measure and evaluate vegetation restoration efficiency of ecological compensation (VREoEC) in an ecological project. However, the output efficiency of ecological compensation is still unclear, and its influencing factors need further exploration. In this research, Wuqi and Zhidan, two pioneer counties in China's Grain for Green (GFG) project, were taken together as the study area, and remote sensing vegetation indices were used to reflect the vegetation coverage level, and the geographically-weighted regression model was applied to measure the VREoEC in the GFG project. Then, the classic multiple linear regression model was used to explore the influencing factors of VREoEC. The findings were as follows: (1) while the overall vegetation coverage in the study area was improved greatly, the VREoEC showed noticeable spatial trend and accumulation, and suffered from regional water-heat distribution; (2) local terrain, micro-climate conditions, rural roads density, classified highway, and intensity of ecological compensation affected the VREoEC; and (3) because local natural and socio-economic conditions can affect the VREoEC, ecological compensation measures need to be formulated according to local conditions. Thus, this study provides a methodological reference and corresponding policy suggestions. [ABSTRACT FROM AUTHOR]

Plantations have been widely established to improve ecosystem services and functioning. Black locust, Robinia pseudoacacia L. is a common, widely planted species to control soil erosion on the Loess Plateau. Previous studies have focused on economic values but the interactions between soil and plant carbon (C), nitrogen (N) and phosphorus (P) remain unknown. Investigating variations of soil, green and senesced leaf C, N and P levels in R. pseudoacacia along a latitudinal gradient is useful to understanding its ecological functions. The results show that soil C, N and senesced leaf N and P significantly decreased with an increase in latitude, but there were no significant changes in the senesced leaf C and soil P. The resorption efficiency of N was related with latitude and soil N levels, and the relation between green leaf N and soil N was significant. These relations suggest that soil N was the key in affecting green leaf N levels. At higher latitudes, senesced leaves had lower N levels associated with higher N resorption efficiency to maintain a stable N content in green leaves. With a decrease of soil N, R. pseudoacacia can enhance N resorption efficiency to meet the demand of growth. Thus, it is an important species for reforestation, especially in nutrient-poor environments. [ABSTRACT FROM AUTHOR]

Soil moisture is essential for vegetation restoration in arid and semi‐arid regions. Ascertaining the vertical distribution and transportation of soil moisture under different vegetation types has a profound effect on the ecological construction. In this study, the soil moisture at a depth of 500 cm for four typical vegetation types, including Robinia pseudoacacia, Caragana korshinskii, Stipa bungeana, and corn, were investigated and compared in the Zhifanggou watershed of the Loess plateau. Additionally, hydrogen and oxygen stable isotopes were detected to identify the transport mechanism of soil moisture. The results showed vertical distribution and transportation of soil moisture were different under different vegetation types. Depth‐averaged soil moisture under S. bungeana and corn generally increased along the profile, while C. korshinskii and R. pseudoacacia showed weakly increasing and relatively stable after an obvious decreasing trend (0–40 cm). The soil moisture under R. pseudoacacia was lower than that under other vegetation types, especially in deep layer. However, the effect of R. pseudoacacia on soil moisture in the topsoil (< 30 cm) could be positive. For R. pseudoacacia (160–500 cm), C. korshinskii (0–500 cm), and S. bungeana (0–100 cm), the soil moisture declined with increased in vegetation age. Planting arbor species such as R. pseudoacacia intensified the decline of soil moisture on the Loess Plateau. The capacity of evaporation fractionation of soil moisture followed the sequence: corn > S. bungeana > R. pseudoacacia > C. korshinskii. The δ18O values in soil water fluctuated across the profile. The δ18O values changed sharply in upper layer and generally remained stable in deep layer. However, in middle layer, the vertical distribution characteristics of the δ18O values were different under different vegetation types. We estimated that piston flow was the main mode of precipitation infiltration, and the occurrence of preferential flow was related to vegetation types. These results were helpful to improve the understanding of the response of deep soil moisture to vegetation restoration and inform practices for sustainable water management. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vegetation restoration decreased deep soil water storage in the Loess Plateau. • Revegetation increased steady infiltration but reduced initial and mean rates. • Soil infiltration rates exhibited gradual decline trends along the slope. • The effect of vegetation type on infiltration was higher than slope position. • Soil water and clay content were key factors influencing infiltration rates. Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems. [ABSTRACT FROM AUTHOR]

• Climate change and restoration policies are the primary and secondary factors to the greening of the Loess Plateau. • The difference-in-differences method suggest lowered contribution of the restoration policy to vegetation greening than previously thought. • Using spatially specific starting time of the policy implementation instead of a fixed year can help better estimate the effects of restoration programs. The vegetation greening on the Loess Plateau, China, over recent decades, has been primarily driven by a series of vegetation restoration programs (VRPs) and other natural environmental changes (including climate change, rising atmospheric CO 2 concentration, and nitrogen deposition, etc.). However, accurate determination of the contributions of natural environmental change and the VRPs to this greening has been challenging due to the lack of the exact time of policy implementation in different areas. Herein, we extracted the starting time of greening (SOG) from different sources of remote sensing data and used it as the starting time of the VRPs. Then, we employed a difference-in-differences (DID) method to ascertain the relative contributions of the VRPs on the observed vegetation greening. Results showed that the contribution of the VRPs to vegetation greening on the Loess Plateau was 23.8–35.8 %, with a greater contribution potentially originating from natural environmental factors. Our findings contribute to a better understanding of the complex relationships among vegetation restoration policies and climate change, and offer a platform to quantify the climate effects on vegetation greening. [ABSTRACT FROM AUTHOR]

Knowledge of soil organic carbon (OC) components and enzyme activities is essential to maintain soil health and for sustainable land use during long-term vegetation restoration. The effects of vegetation restoration on soil physicochemical properties have been widely documented; however, knowledge of the relationships among soil OC components, enzyme activities, and soil properties in restored ecosystems remains unclear. Here, the soil from four successional stages of restored Robinia pseudoacacia vegetation (10, 20, 30, and 40 years) were sampled in China's Loess Plateau. The soil water content (SWC), bulk density (BD), pH, total nitrogen (TN), soil microbial biomass C (MBC) and N (MBN) contents, OC components (labile and recalcitrant OC), and soil enzyme (hydrolytic and oxidase) activities were measured. We found that restoration time significantly affects soil physicochemical properties, OC components and enzyme activities. Across the restoration time, the SWC decreased from year 10 to year 30, then increased from year 30 to year 40. Soil OC and TN increased with restoration time, while soil clay content decreased with restoration time. Following 40 years of restoration, soil MBC and MBN significantly increased by 214% and 88%, respectively. For OC components, 40 years of restoration significantly increased recalcitrant C component rather than labile C component. Soil hydrolytic enzyme activities significantly increased by 76.9% and 80.3% in 40 years stand compared with that of in 10 years stand, respectively, while soil oxidase enzyme activities significantly decreased with restoration time. Correlation analysis demonstrated that the SOC and MBC content significantly influenced soil recalcitrant C component and hydrolytic enzyme activities, while MBC and clay content significantly influenced soil oxidase enzyme activities. These results provided useful insights on the responses of forest restoration on soil OC components and related OC degrading enzymes and the understanding of soil C sequestration in the restored ecosystems in such areas. [ABSTRACT FROM AUTHOR]

The relationship between soil fauna and vegetation diversity has been of continuous concern. The effects of the “Grain-for-Green” program on the Loess Plateau in maintaining the abundance and diversity of soil fauna are poorly understood. This study assessed the spatial influence of five common artificial restoration habitats, Populus simonii, Pinus tabulaeformis, Caragana korshinskii, Medicago sativa, and Stipa bungeana, and one farmland habitat on the characteristics of soil fauna communities. Results showed that six soil fauna groups (Araneae, Acarina, Collembola, Isoptera, Coleoptera larvae, and Coleoptera adults) were shared among these habitats, accounting for 37.5% of the total number of groups. Acarina was the dominant group in each habitat. The soil fauna abundance in the P. tabulaeformis habitat was the highest among the habitats, reaching 7656 ind m−2. S. bungeana had the highest diversity, richness, and evenness indices of soil fauna among the habitats. Furthermore, a remarkable correlation among main soil properties (water content, organic carbon, and available potassium), litter properties (vegetation coverage, vegetation density, and litter thickness), and soil fauna were observed. The differences in microenvironment among the six habitats had a strong influence on the composition of soil fauna communities. Compared with other habitats, the S. bungeana habitat is more conducive to the protection of biodiversity. Vegetation restoration increases the diversity of soil fauna by improving their living environment, and soil fauna communities can be used as assessment indicators for “vegetation restoration benefits.” These findings help reveal the developmental tendencies of soil fauna during vegetation restoration in the Loess Plateau, and provide important support for evaluating environmental quality by soil fauna.

The transport of eroded soil to rivers changes the nutrient cycles of river ecosystems and has significant impacts on the regional eco-environment and human health. The Loess Plateau, a leading vegetation restoration region in China and the world, has experienced severe soil erosion and nutrient loss, however, the extent to which vegetation restoration prevents soil erosion export (to rivers) and it caused nutrient loss is unknown. To evaluate the effects of the first stage of the Grain for Green Project (GFGP) on the Loess Plateau (started in 1999 and ended in 2013), we analyzed the vegetation change trends and quantified the effects of GFGP on soil erosion export (to rivers) and it caused nutrient loss by considering soil erosion processes. The results were as follows: (1) in the first half of study period (from 1982 to 1998), the vegetation cover changed little, but after the implementation of the first stage of the GFGP (from 1999 to 2013), the vegetation cover of 75.0% of the study area showed a significant increase; (2) The proportion of eroded areas decreased from 41.8 to 26.7% as a result of the GFGP, and the erosion intensity lessened in most regions; the implementation significantly reduce the soil nutrient loss; (3) at the county level, soil erosion export could be avoided significantly by the increasing of vegetation greenness in the study area (R = −0.49). These results illustrate the relationships among changes in vegetation cover, soil erosion and nutrient export, which could provide a reference for local government for making ecology-relative policies.

Gully erosion has been considered as one of the main forms of soil erosion on the Loess Plateau of China. To control soil and water loss and improve the eco-environmental quality of the Loess Plateau, the Chinese government implemented the “Grain for Green” project in 1999 to restore vegetation on steep slope farmlands. Although the project has been implemented for two decades, soil erosion on the loess hilly region caused by extreme rainstorms is still serious. Therefore, the controlled effects of vegetation restoration on gully formation and soil erosion on loess hillslopes under extreme rainstorms need to be evaluated. Moreover, the effect of land use change on the morphology of gullies and gully volume estimation under extreme rainstorms is poorly understood. Given these issues, the Chabagou watershed (a typical watershed in the Loess Plateau of China) suffered by an rainstorm (called “7·26” rainstorm) was selected as the study area of gully erosion. Four small basins in the Chabagou watershed were selected from the upper, middle, and lower reaches, respectively, to explore the morphological characteristics and derive volume estimation models of three land uses (farmland, fallow land, and abandoned land) under extreme rainstorm. A total of 140 gullies were investigated, including 45 gullies on farmland, 66 gullies on fallow land and 29 gullies on abandoned land. The gully length was measured by the laser rangefinder and the gully was divided into three sections (upper, middle and lower) by a 50-m tape. In each section, the top width, bottom width and the depth of the gully were measured using a steel tape. The measuring times was adjusted according to the gully length to ensure the measuring accuracy. The measured cross-sectional parameters (i.e. width and depth) of the three sections were averaged as the eventual width and depth of each section, and the gully volumes of the three sections were summarized to be the amount of gully erosion. The results showed that: 1) the gullies less than 20 m on farmland, fallow land and abandoned land accounted for 55.6%, 34.8% and 44.8%, respectively. The averaged gully depth on farmland was 110 cm, which was 18.3%, and 19.2% higher than those on fallow land and abandoned land, respectively. The width-depth ratios of gully on farmland and fallow land were 0.87 and 0.84, respectively, and their cross sections were characterized by the wide and shallow shape, but the crossed section of the gully on abandoned land was closed to squared shape (width-depth ratio was 1.01). 2) The lowest gully erosion volume was found on abandoned land, which was 47.8% and 28.3% lower than that of farmland and fallow land, respectively, indicating that vegetation restoration can effectively contain gully erosion under extreme rain. 3) Gully erosion volume of farmland on upslope was largest, followed by downslope and mid-lope, while fallow land and abandoned land showed an increasing trend along the slope. For the three types of land use, the widening rate of gully on the upslope was greater than that on the downslope, but the opposite was found on the mid-slope. 4) The significant (P<0.001) power functions could express the relationships between gully erosion volume and gully length and/or gully cross-sectional area on farmland, fallow land, and abandoned land, and the cross-sectional area was a more effective parameter for estimating gully volume. This study results can provide important information for predicting the gully erosion of different land use types and controlling gully erosion in the hilly area of the Loess Plateau. [ABSTRACT FROM AUTHOR]

The transport of eroded soil to rivers changes the nutrient cycles of river ecosystems and has significant impacts on the regional eco-environment and human health. The Loess Plateau, a leading vegetation restoration region in China and the world, has experienced severe soil erosion and nutrient loss, however, the extent to which vegetation restoration prevents soil erosion export (to rivers) and it caused nutrient loss is unknown. To evaluate the effects of the first stage of the Grain for Green Project (GFGP) on the Loess Plateau (started in 1999 and ended in 2013), we analyzed the vegetation change trends and quantified the effects of GFGP on soil erosion export (to rivers) and it caused nutrient loss by considering soil erosion processes. The results were as follows: (1) in the first half of study period (from 1982 to 1998), the vegetation cover changed little, but after the implementation of the first stage of the GFGP (from 1999 to 2013), the vegetation cover of 75.0% of the study area showed a significant increase; (2) The proportion of eroded areas decreased from 41.8 to 26.7% as a result of the GFGP, and the erosion intensity lessened in most regions; the implementation significantly reduce the soil nutrient loss; (3) at the county level, soil erosion export could be avoided significantly by the increasing of vegetation greenness in the study area (R = −0.49). These results illustrate the relationships among changes in vegetation cover, soil erosion and nutrient export, which could provide a reference for local government for making ecology-relative policies. [ABSTRACT FROM AUTHOR]

Vegetation restoration is identified as an effective approach to control soil erosion and affects soil detachment and resistance to concentrated flow on the Loess Plateau. However, the effects of vegetation restoration at gully heads in loess‐tableland remains unclear. This study was performed to investigate the effects of nine vegetation restoration types at gully heads on soil detachment rate (Dr) and soil resistance to concentrated flow (i.e. soil erodibility, Kr and critical shear stress, τc). Undisturbed soil samples were collected from nine vegetation‐restored lands and one slope cropland (as the control) and were subjected to a hydraulic flume to obtain Dr values of gully heads under six inflow discharges (0.5–3.5 L s‐1). The results showed that the Dr values of nine revegetated gully heads were 77.11% to 95.81% less than that of slope cropland, and the grassland dominated by Cleistogenes caespitosa and the shrubland dominated by Hippophae rhamnoides had a relatively greater decrease in Dr than those of other seven restoration types. The Dr value of nine revegetated gully heads could be better simulated by stream power than by flow velocity and shear stress and was also significantly affected by soil disintegration rate (positively), soil bulk density, saturated hydraulic conductivity, organic matter content, and water‐stable aggregate stability (negatively). Additionally, roots with diameters of 0 to 0.5 mm showed a greater effect on Dr than those with larger diameters. Compared to cropland, the nine restored types reduced Kr by 76.26% to 94.26% and improved τc by 1.51 to 4.68 times. The decrease in Kr and the increase in τc were significantly affected by organic matter content, water‐stable aggregate, mean weight diameter of aggregate and root mass density. The combination of grass species (Cleistogenes caespitosa) and shrub (Hippophae rhamnoides) could be considered the best vegetation restoration types for improving soil resistance of gully heads to concentrated flow. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Vegetation restoration has returned a large number of steep slope farmlands to forests and grasslands, and effectively controlled soil erosion in the Loess Plateau. In the loesstableland and gully region of the Loess Plateau, loess-tableland, hill-slope and gully-slope are widely distributed. Geomorphological location and land use may lead to differences in soil properties and vegetation root systems, and thus affect soil erodibility. However, few studies have been conducted to explore the impact of vegetation restoration at different geomorphological locations on soil erodibility, and the relationships between soil erodibility and influencing factors. This study was carried out in the Nanxiaogou watershed in the loesstableland and gully region of the Loess Plateau. The undisturbed topsoil (0-20 cm) of farmland, grassland, shrub land and woodland was sampled on loess-tableland, hill-slope and gully-slope (no farmland on gully-slope). The comprehensive soil erodibility index (CSEI) was obtained by weighted sum method. The results indicated that: (1) The significant difference in CSEI was found among different geomorphological locations. The CSEI of gully- slope was 8.1% and 77.7% higher than those of hill- slope and loess- tableland, respectively. (2) As for the loesstableland, the CSEI of grassland, shrub land and woodland decreased by 21.1%, 29.2% and 28.8%, respectively compared with that of farmland. For the hill- slope and gully- slopes, the CSEI of woodland was lower than that of other land use types. (3) The CSEI had significantly negative correlations with clay content, sand content, soil capillary porosity, root weight density, root mean diameter, root length density and root surface area density, but significantly positive correlations with silt content and soil bulk density. Multivariate linear stepwise regression indicates that silt content, root mean diameter and soil bulk density are the most important factors influencing CSEI, among which silt content has the greatest direct influence on CSEI, while root mean diameter exerts negative influence on CSEI through direct or indirect effects. This study suggests that shrubs should be the preferred vegetation for vegetation restoration on the loess- tableland. Revegetation with arbor as dominant community may be more effective in controlling soil and water loss on hill-slope and gully-slope. [ABSTRACT FROM AUTHOR]

A thorough understanding of the vegetation succession in relation to both climatic changes and anthropogenic activities is vital for the formulation of adaptation strategies that address potential ecosystem challenges. Various climatic factors such as temperature, precipitation, and solar radiation, as well as anthropogenic factors such as ecological engineering and population migration, will affect the conditions for vegetation. However, the relationships among various factors remain unclear and the response of vegetation to climate change and anthropogenic activities in the Loess Plateau of China has not been well established. This study investigated the spatio-temporal characteristics and relationships between vegetation coverage and climatic factors in the Loess Plateau for the period of 1985–2015. Further analysis separated the anthropogenic and climatic factors on vegetation succession based on residual analysis. The results showed that the normalized difference vegetation index (NDVI) followed a significant upward trend with annual change rates of 0.15% during 1985–2015. The trend of human-induced NDVI increase was consistent with the spatial distribution of increasing forest areas in the eastern part of the Loess Plateau. Eco-restoration projects were the main driving factors that promoted vegetation coverage on the Loess Plateau. Furthermore, these results demonstrated that migrants to cities in the Loess Plateau could relieve ecological pressures and promote vegetation restoration. Therefore, the government should strive to increase population mobility and restore vegetation to sustain this particularly fragile ecological environment. [ABSTRACT FROM AUTHOR]