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Litter of different species coexists in the natural ecosystem and may induce non-additive effects during decomposition. Identifying and quantifying the origins of species in litter mixtures is essential for evaluating the responses of each component species when mixed with co-occurring species and then unraveling the underlying mechanism of the mixing effects of litter decomposition. Here, we used near-infrared spectroscopy (NIRS) to predict the species composition and proportions of four-tree species foliage mixtures in association with litter crude ash and litter decomposition time. To simulate the whole mixed litter decomposition process in situ, a controlled mixture of four tree species litter leaves consisting of 15 tree species combinations and 193 artificial mixed-species samples were created for model development and verification using undecomposed pure tree species and decomposed litter of single tree species over one year. Two series of NIRS models were developed with the original mass and ash-free weight as reference values. The results showed that these NIRS models could provide an accurate prediction for the percentage of the component species from in the litter leaf mixture's composition. The predictive ability of the near-infrared spectroscopy model declined marginally with the prolonged litter decomposition time. Furthermore, the model with ash-free litter mass as a reference exhibited a higher coefficient of determination (R2) and a lower standard error of prediction (RMSECV). Thus, our results demonstrate that NIRS presents great potential for not only predicting the organic composition and proportion in multi-species mixed samples in static conditions, but also for samples in dynamic conditions (i.e., during the litter decomposition process), which could facilitate evaluation of the species-specific responses and impacts on the interspecific interactions of co-occurring species in high-biodiversity communities. [ABSTRACT FROM AUTHOR]

The process of rapid urbanization in China has led to various impacts on the urban ecological environment and one of these significant effects is the urban heat island (UHI). Pursuing the construction of a ecological city is recognized as an important direction to relieve the contradictions between environmental protection and city development. Yet how the landcape configuation and composition in such city development influences the UHI has not been well understood. This paper attempted to evaluate the spatial patterning of land surface temperature (LST) and to discuss the effects of source and sink landscape patterns upon LST in a smart city demonstrated at the local level in China. The results revealed that the UHI was spatially associated with the land use changes driven by rapid urbanization and gradually declines along the urban–rural gradient. When the urban–rural gradient reached the range of 7.5 to 8.75 km from the city center, there exhibited a tipping point where the combinative effects of source and sink landscapes on UHI significantly decreased. Through exploring the impact of source-sink landscape area ratio on UHI, we also found a tipping point that when source-sink area ratio in a patch was smaller than the golden separation value (1.30), UHI effect was almost mitigated because the warming effect of source area would be weaker than the cooling effect of sink area. Overall, this study highlights that controlling the optimal area ratio of source-sink landscape are very important strategy for mitigating the UHI effect during urban development and planning. [ABSTRACT FROM AUTHOR]

Background: Forest ecosystems play an important role in carbon sequestration, climate change mitigation, and achieving China's target to become carbon (C) neutral by 2060. However, changes in C storage and net primary production (NPP) in natural secondary forests stemming from tree growth and future climate change have not yet been investigated in subtropical areas in China. Here, we used data from 290 inventory plots in four secondary forests [evergreen broad-leaved forest (EBF), deciduous and evergreen broad-leaved mixed forest (DEF), deciduous broad-leaved forest (DBF), and coniferous and broad-leaved mixed forest (CDF)] at different restoration stages and run a hybrid model (TRIPLEX 1.6) to predict changes in stand carbon storage and NPP under two future climate change scenarios (RCP4.5 and RCP8.5). Results: The runs of the hybrid model calibrated and validated by using the data from the inventory plots suggest significant increase in the carbon storage by 2060 under the current climate conditions, and even higher increase under the RCP4.5 and RCP8.5 climate change scenarios. In contrast to the carbon storage, the simulated EBF and DEF NPP declines slightly over the period from 2014 to 2060. Conclusions: The obtained results lead to conclusion that proper management of China's subtropical secondary forests could be considered as one of the steps towards achieving China's target to become carbon neutral by 2060. [ABSTRACT FROM AUTHOR]

Canopy interception loss is an important hydrological process that affects rainfall redistribution, nutrient cycling, and soil and water conservation in forest ecosystems. However, the manner in which interception loss is affected in forests that are in restoration stages dominated by different tree species has not been fully understood. In this study, interception loss, throughfall, and stemflow were measured consecutively for 2 years (May 2017 through April 2019) in three secondary forests in subtropical China: a coniferous and broadleaved mixed forest (Pinus massoniana, Lithocarpus glaber, PM) in early restoration stage, a deciduous broadleaved forest (Choerospondias axillaris, CA) in middle restoration stage, and an evergreen broadleaved forest (L. glaber–Cyclobalanopsis glauca, LG) in late restoration stage. For a given amount of rainfall, the relative interception loss in the CA was significantly lower than that in the evergreen forests in summer, spring, or winter. The amount of interception loss during light rain, moderate rain, or heavy storms was also significantly lower in CA as compared to that in evergreen forests, owing to the lesser leaf area and phenology of deciduous tree species as well as a higher leaf area index (LAI) and stand density in PM and LG. Meanwhile, the highest relative interception loss, interception loss amount, canopy storage capacity, canopy cover fraction, and mean evaporation rate was observed in the climax forest (LG), which has a higher LAI and stand density. Further, the revised Gash's analytical model (RGAM) and the sparse Rutter models were successfully applied to simulate interception loss in these forests, with the RGAM performing better as compared to the sparse Rutter model. The results of the field measurements and model simulations depict that the climax community at the late restoration stage can effectively reduce the amount of rainwater reaching the soil surface, thus weakening the effect of flood peaks. [ABSTRACT FROM AUTHOR]

Aim: Tree species diversity can increase the stability of ecosystem productivity by increasing mean productivity and/or reducing the standard deviation in productivity. However, stand structure, environmental and socio‐economic conditions influence plant diversity and might strongly influence the relationships between diversity and stability in natural forest communities. The relative importance of these factors for community stability remains poorly understood in complex (species‐rich) subtropical forests. Location: Subtropical area of southern China. Time period: 1999–2014. Major taxa studied: Forest trees. Methods: We conducted bivariate analyses to examine the mechanisms (overyielding and species asynchrony) underlying the effects of diversity on stability. Multiple regression models were then used to determine the relative importance of tree species diversity, stand structure, socio‐economic factors and environmental conditions on stability. Structural equation modelling was used to disentangle how these variables directly and/or indirectly affect forest stability. Results: Tree species richness exerted a positive effect on stability through overyielding and species asynchrony, and this effect was stronger in mountainous forests than in hilly forests. Species richness positively affected the mean productivity, whereas species asynchrony negatively affected the variability in productivity, hence increasing forest stability. Structural diversity also had a positive effect, whereas population density had a negative effect on stability. Precipitation variability and slope mainly had indirect influences on stability through their effects on tree species richness. Main conclusions: Overall, tree species diversity governed stability; however, stand structure, socio‐economic conditions and environmental conditions also played an important role in shaping stability in these forests. Our work highlights the importance of regulating stand structure and socio‐economic factors in forest management and biodiversity conservation, to maintain and enhance their stability to provide ecosystem services in the face of unprecedented anthropogenic activities and global climate change. [ABSTRACT FROM AUTHOR]

Background: Soil and vegetation have a direct impact on the process and direction of plant community succession, and determine the structure, function, and productivity of ecosystems. However, little is known about the synergistic influence of soil physicochemical properties and vegetation features on vegetation restoration. The aim of this study was to investigate the co-evolution of soil physicochemical properties and vegetation features in the process of vegetation restoration, and to distinguish the primary and secondary relationships between soil and vegetation in their collaborative effects on promoting vegetation restoration in a subtropical area of China. Methods: Soil samples were collected to 40 cm in four distinct plant communities along a restoration gradient from herb (4–5 years), to shrub (11–12 years), to Pinus massoniana coniferous and broadleaved mixed forest (45–46 years), and to evergreen broadleaved forest (old growth forest). Measurements were taken of the soil physicochemical properties and Shannon–Wiener index (SD), diameter at breast height (DBH), height (H), and biomass. Principal component analysis, linear function analysis, and variation partitioning analysis were then performed to prioritize the relative importance of the leading factors affecting vegetation restoration. Results: Soil physicochemical properties and vegetation features showed a significant trend of improvement across the vegetation restoration gradient, reflected mainly in the high response rates of soil organic carbon (SOC) (140.76%), total nitrogen (TN) (222.48%), total phosphorus (TP) (59.54%), alkaline hydrolysis nitrogen (AN) (544.65%), available phosphorus (AP) (53.28%), species diversity (86.3%), biomass (2906.52%), DBH (128.11%), and H (596.97%). The soil properties (pH, SOC, TN, AN, and TP) and vegetation features (biomass, DBH, and H) had a clear co-evolutionary relationship over the course of restoration. The synergistic interaction between soil properties and vegetation features had the greatest effect on biomass (55.55%–72.37%), and the soil properties contributed secondarily (3.30%–31.44%). The main impact factors of biomass varied with the restoration periods. Conclusions: In the process of vegetation restoration, soil and vegetation promoted each other. Vegetation restoration was the cumulative result of changes in soil fertility and vegetation features. [ABSTRACT FROM AUTHOR]

Forest productivity may be determined not only by biodiversity but also by environmental factors and stand structure attributes. However, the relative importance of these factors in determining productivity is still controversial for subtropical forests.Based on a large dataset from 600 permanent forest inventory plots across subtropical China, we examined the relationship between biodiversity and forest productivity and tested whether stand structural attributes (stand density in terms of trees per ha, age and tree size) and environmental factors (climate and site conditions) had larger effects on productivity. Furthermore, we quantified the relative importance of environmental factors, stand structure and diversity in determining forest productivity.Diversity, together with stand structure and site conditions, regulated the variability in forest productivity. The relationship between diversity and forest productivity did not vary along environmental gradients. Stand density and age were more important modulators of forest productivity than diversity.Synthesis. Diversity had significant and positive effects on productivity in species‐rich subtropical forests, but the effects of stand density and age were also important. Our work highlights that while biodiversity conservation is often important, the regulation of stand structure can be even more important to maintain high productivity in subtropical forests. [ABSTRACT FROM AUTHOR]

Rocky desertification is a major ecological problem of land degradation in karst areas. In these areas, the high soil calcium (Ca) content has become an important environmental factor that can affect the restoration of vegetation. Consequently, the screening of plant species that can adapt to high Ca soil environments is a critical step in vegetation restoration. In this study, three grades of rocky desertification sample areas were selected in karst areas of southwestern Hunan, China (LRD: light rocky desertification; MRD: moderate rocky desertification; and IRD: intense rocky desertification). Each grade of these sample areas had three sample plots in different slope positions, each of which had four small quadrats (one in rocky-side areas, three in nonrocky- side areas). We measured the Ca content of leaves, branches, and roots from 41 plant species, as well as soil total Ca (TCa) and exchangeable Ca (ECa) at depths of 0- 15, 15-30, and 30-45 cm in each small quadrat. The results showed that the soil Ca2+ content in rocky-side areas was significantly higher than that in non-rocky-side areas (p < 0:05). The mean soil TCa and ECa content increased gradually along with the grade of rocky desertification, in the order IRD >MRD> LRD. For all plant functional groups, the plant Ca content of aboveground parts was significantly higher than that of the belowground parts (p < 0:05). The soil ECa content had significant effects on plant Ca content of the belowground parts but had no significant effects on plant Ca content of the aboveground parts. Of the 41 plant species that were sampled, 17 were found to be dominant (important value > 1). The differences in Ca2+ content between the aboveground and belowground parts of the 17 dominant species were calculated, and their correlations with soil ECa content were analyzed. The results showed that these 17 species can be divided into three categories: Caindifferent plants, high-Ca plants, and low-Ca plants. These findings provide a vital theoretical basis and practical guide for vegetation restoration and ecosystem reconstruction in rocky desertification areas. [ABSTRACT FROM AUTHOR]

Chinese subtropical forests contain a diversity of tree species and exhibit a high carbon (C) sequestration capacity, but biomass and C stock assessments in subtropical secondary forests remain uncertain because of a limited availability of allometric equations and an uncertain applicability of existing allometric equations that have not been tested for these forests. We developed allometric equations for important coniferous ( Pinus massoniana), deciduous broadleaved ( Alniphyllum fortunei, Choerospondias axillaris, Liquidambar formosana) and evergreen broadleaved ( Cyclobalanopsis glauca, Litsea rotundifolia, Schima superba) species. A total of 70 trees (10 trees for each species) with diameters at breast height ( D) ranging from 2.6 to 50.9 cm were destructively harvested and dissected into tree components (stem, branch, leaf and coarse root). Species-specific equations using D alone as the predictor variable fitted the data well ( p < 0.0053 and R > 0.72) for each tree component. Including height ( H) in the form of D H only improved the regression fit for A. fortunei and L. rotundifolia. The relationships of branch, leaf and root biomass against D varied among tree species. General equations for functional groups and all species combined showed comparable bias for stem, aboveground and total tree biomass to species-specific equations. We recommend the general equations of multiple species to estimate forest biomass at regional scales and also to estimate stem, aboveground and total tree biomass for each species when species-specific allometric equations are not available at a given site. For branch, leaf and root biomass, species-specific equations are preferred, even though this requires biomass data for additional tree species. [ABSTRACT FROM AUTHOR]

Subtropical forests across south China have been extensively affected by anthropogenic disturbances with potential profound effects on plant biodiversity and ecosystem function (BEF). However, whether and to what degree biodiversity influences biomass of subtropical forests remains uncertain. In this study, we analyzed the effects of tree biodiversity (species diversity, functional diversity and phylogenetic diversity) on stand biomass at three stages (early, mid and late) of succession in subtropical forests. As forest succession progressed, we found that the changes in species diversity were different compared with those of functional and phylogenetic diversity. Most of the indices of species and functional and phylogenetic diversity were not significantly correlated with stand biomass at two spatial grains (plot sizes of 10 m × 10 m and 20 m × 30 m). However, when other abiotic and biotic factors (i.e., altitude, canopy light, stem density and forest phase) were included with diversity indices in mixed models to explain biomass, the effect of functional diversity on biomass was significant at both resolution. For species diversity indices, the effect was significant at the 20 m × 30 m resolution, and phylogenetic diversity had no significant effect. Our results indicate that biodiversity affects forest biomass during the succession of a subtropical forest and suggest that functional diversity may provide a better metric than species or phylogenetic diversity for determining the biodiversity effect on biomass. Moreover, our results indicate that the diverse conclusions reached in other BEF analyses might be explained by differences in the plot size examined and the diversity metrics selected. Because the bivariate relationship between biodiversity and biomass can be strongly confounded by covarying abiotic and biotic factors, we suggest that the effects of abiotic factors, succession stage, and management practices on BEF should be carefully considered in future research. [ABSTRACT FROM AUTHOR]

Aims A lack of explicit information on differential controls on net primary productivity (NPP) across regions and ecosystem types is largely responsible for uncertainties in global trajectories of terrestrial carbon balance with changing environment. The objectives of this study were to determine how NPP of different forest types would respond to inter-annual variability of climate and to examine the responses of NPP to future climate change scenarios across contrasting forest types in northern China. Methods We investigated inter-annual variations of NPP in relation to climate variability across three forest types in northern China, including a boreal forest dominated by Larix gmelinii Rupr., and two temperate forests dominated by Pinus tabulaeformis Carr. and Quercus wutaishanica Mayr., respectively, and studied the responses of NPP in these forests to predicted changes in climate for the periods 2011–40, 2041–70 and 2070–100 under carbon emission scenarios A2 and B2 of Intergovernmental Panel on Climate Change. We simulated the responses of NPP to predicted changes in future climate as well as inter-annual variability of the present climate with the Biome-BGC version 4.2 based on site- and species-specific parameters. The modeled forest NPP data were validated against values in literature for similar types of forests and compared with inter-annual growth variations reflected by tree-ring width index (RWI) at the study sites. Important Findings Inter-annual variations in modeled NPP during the period 1960–06 were mostly consistent with the temporal patterns in RWI. There were contrasting responses of modeled NPP among the three forest types to inter-annual variability of the present climate as well as to predicted changes in future climate. The modeled NPP was positively related to annual mean air temperature in the L. gmelinii forest (P < 0.001), but negatively in the P. tabulaeformis forest (P = 0.05) and the Q. wutaishanica forest (P = 0.03), while the relationships of modeled NPP with annual precipitation for the three forest types were all positive. Multiple stepwise regression analyses showed that temperature was a more important constraint of NPP than precipitation in the L. gmelinii forest, whereas precipitation appeared to be a prominent factor limiting the growth in P. tabulaeformis and Q. wutaishanica. Model simulations suggest marked, but differential increases in NPP across the three forest types with predicted changes in future climate. [ABSTRACT FROM AUTHOR]

The continuous global climate change has affected the living habits, morphological characteristics and spatial distribution of tree species. Chinese fir (C. lanceolata (Lamb.) Hook) is one of the most important conifer tree species in China, which plays a major role in terms of timber supplies and environment protection. Predict the potential suitable habitats of Chinese fir under different climatic scenarios, can not only provide scientific theoretical basis for the planning and planting of Chinese fir, but also have great significance for maintaining the stability of the plantation ecosystem. Here, we used the maximum entropy (Maxent) model which optimized by the ENMeval package, to predicted the potential suitable habitats for Chinese fir under current climatic conditions and two climatic scenarios in 2070s. Our results showed that the complexity of the model was relative low, when the regularization multiplier (RM) was 0.5 and feature combination (FC) was linear (L) and quadratic (Q). Under this parameter setting, the high and moderate suitable habitat area of Chinese fir were 83.90 × 104 km2 and 97.62 × 104 km2, respectively, which suggested we can carry out Chinese fir planting activities with different cultivation purposes. The minimum temperature of the coldest month, annual precipitation, annual mean temperature and mean temperature of warmest quarter were identified as the essential factors shaping habitat suitability for Chinese fir. Under future climate scenarios, the high suitable habitat was reduced and the degree of fragmentation was increased, and the total potential suitable habitat of Chinese fir had the tendency to migrate to high-altitude regions. Managers should be cautious about the cultivation area selection of Chinese fir plantation as the potential suitable habitat changed under the global climate change continuously. It is therefore imperative to adjust the long-term management and protection strategy of Chinese fir plantation. • Maxent was used to predicted the potential habitat of Chinese fir. • R package ENMeval was used to optimized the Maxent model. • Potential habitat of Chinese fir were concentrated in subtropical regions. • Potential habitat had a tendency to migrate to high-altitude regions. • Temperature and precipitation were main factors affecting potential distribution. [ABSTRACT FROM AUTHOR]

• Equations were based on rates of change rather than state variables. • Self-thinning equations accounted for species mixing, dominance, site, and climate. • All-species equations were also developed, and could be used for rarer species. • Based on temperate, Mediterranean and subtropical stands in Australia, China and Switzerland (1579 plots). Self-thinning dynamics are often considered when managing stand density in forests and are used to constrain forest growth models. However, self-thinning relationships are often quantified using only data at a conceptualised self-thinning line, even though self-thinning can begin before the stand actually reaches a self-thinning line. Also, few self-thinning relationships account for the effects of species composition in mixed-species forests, and stand structure such as relative height of species (in mixtures), and/or size or age cohorts in uneven-aged forests. Such considerations may be important given the effects of global climate change and interest in mixed-species and uneven-aged forests. The objective of this study was to develop self-thinning relationships based on changes in the tree density relative to mean tree diameter, instead of focusing only on data for state variables (e.g. tree density) at the self-thinning line. This was done while also considering how the change in tree density is influenced by site quality and stand structure (species composition and relative height). The relationships were modelled using data from temperate Australian Eucalyptus plantations (436 plots), subtropical forests in China (88 plots), and temperate forests in Switzerland (1055 plots). Zero-inflated and hurdle generalized linear models with Poisson and negative binomial distributions were fit for several species, as well as for all-species equations. The intercepts and slopes of the self-thinning lines were higher than many published studies which may have resulted from both the less restrictive equation form and data selection. The rates of self-thinning often decreased as the proportion of the object species increased, as relative height increased (species or size cohort became more dominant), and as site (quality) index increased. The effects of aridity varied between species, with self-thinning increasing with aridity index for Abies alba, Pinus sylvestris, Quercus petraea and Quercus robur , but decreasing with aridity index for Eucalyptus nitens, Fagus sylvatica and Picea abies as sites became wetter and cooler. Self-thinning model parameters were not correlated with species traits, including specific leaf area, wood basic density or crown diameter – stem diameter allometry. All-species self-thinning relationships based on all data could be adjusted using a correction factor for rarer species where there were insufficient data to develop species-specific equations. The approach and equations developed could be used in forest growth models to calculate how the tree density declines as mean tree size increases, as height changes relative to other cohorts or species, as species proportions change, and as climatic and edaphic conditions change. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is the most commonly grown afforestation species in subtropical China. It is essential that we understand the response of radial tree growth to climate factors, yet most experiments have been conducted based on total annual growth and not on monthly dynamics, which alone can detail the influence of climatic factors. In this study, we aimed to: (i) construct a monthly growth model and compare the growth rate of different social statuses of trees, and (ii) determine the response of radial increments of different social statuses to climate factors. The radial growth was monitored monthly during four years using manual band dendrometers (MBD). The data were fitted using the Gompertz function. Within-stand differences in the social status of Chinese firs resulted in growing period and growth rate length variations. The radial growth began in March, and suppressed trees—especially groups of AS1 and BS1 (suppressed trees of classes I in sites A and B)—stopped in September, whereas dominant and intermediate trees were delayed and stopped in November. The periodic monthly increment curve showed double peaks, and the maximum growth rate occurred in April and August. The peak values were affected by social status, which showed that dominant trees had the greatest radial growth rates. S-shaped Gompertz meant that monthly increment models were successfully fitted to our data, which explained more than 98% of the variation in increment data and passed the uncertainty test. Temperature and precipitation had a significant influence on radial growth, and the correlation between radial growth and air temperature was the highest. Our results also revealed that temperatures explain the double-peak features of Chinese fir. The limiting factors of radial growth changed with the seasons and were mainly affected by temperature and precipitation, which should be considered in predicting the response of tree growth to climate change. [ABSTRACT FROM AUTHOR]

Despite the accumulating evidence of the beneficial effects of diverse mixed species forests on ecosystem functioning and services, foresters in subtropical forest cultivation in China still prefer easily managed monocultures, which is also due to the complexity of mixed forests and the unknown underlying mechanisms related to relationships between biodiversity and forest growth. In a designed pot experiment, we selected two early-successional tree species (Pinus massoniana Lamb., Liquidambar formosana Hance.) and two late-successional tree species (Schima superba Champ., Elaeocarpus decipiens Hemsl.) and planted four saplings in one pot with regard to tree species diversity (monoculture, two species and four species mixtures), each combination replicated four times. In this three-year duration experiment, the effect of tree species diversity, tree identity, and functional traits on sapling growth (tree height, ground diameter, crown projection area), were analyzed. The results showed that the increments of ground diameter and crown projection area increased with tree species richness, whereas the mean tree height increment showed the opposite effect. This growth variation was species specific and related to functional traits (early or late succession), as the increments of the early successional tree species (P. massoniana Lamb. and L. formosana Hance.) had a positive correlation with tree species richness, while the late successional tree species (E. decipiens Hemsl. and S. superba Champ.) showed negative effects. In addition, our study provided evidence for the allometric differences between mixtures and monocultures, which have an important reference value on mixed-species forests. [ABSTRACT FROM AUTHOR]

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is an important native tree species that is widely distributed in subtropical areas of southern China and cultivated for wood extraction. However, information on water use by Chinese fir plantations is still scarce. In this study, we performed species-specific parameter calibrations for the original Granier equation for sap flow density (SFD) estimates. Stand transpiration (Es) was related to environmental inputs, such as rainfall, air temperature (Ta), vapor pressure deficit (VPD), photosynthetically-active radiation (PAR), air relative humidity (RH), and potential evapotranspiration (PET) in order to examine how environmental factors affect the Es of Chinese fir plantations. According to our results, Granier’s original parameters set underestimated C. lanceolataSFD by up to 54% compared to our species-specific calibrated parameters set. A strong positive correlation was found between SFD, diameter at breast height (DBH), and tree height among trees populations. The total Es in 2015 was 522.1 mm, with obvious seasonal dynamics and an average of 1.4 mm·day−1. Daily and monthly Es were positively correlated with VPD, PAR, Ta, and PET. A negative relationship between Es and RH was detected only at a daily timescale. Our findings indicate that the original Granier equation requires a parameter calibration when it is applied to species-specific thermal dissipation probe (TDP) estimates, and our findings can also provide novel insights on the water use of Chinese fir in major wood production areas in Southern China. [ABSTRACT FROM AUTHOR]

• Late stage forest supplied higher overall and more evenly distributed ES benefits. • Magnitudes of trade-offs between paired ESs changed with restoration stages. • The beneficiary in several paired trade-offs changed along the restoration gradient. • Tree functional groups are important to ES trade-offs and ecosystem management. Secondary forests have received more attention in recent decades because their total area is increasing and the greater recognition of ecological and economical benefits provided by forest ecosystems. Therefore, the Chinese government has given high priority to implementing its Natural Forest Program that includes the restoration of degraded secondary forests. Hence, how ecosystem services (ESs) and their trade-offs are altered during the restoration process of secondary forests merits research. Here, we selected five key ecological indicators of forests, namely plant diversity and four ESs—air quality regulation, maintenance of soil fertility, global climate regulation, and timber provisioning—to examine the trends and patterns in the variation of multiple indicators and their trade-offs during forest restoration. Furthermore, secondary forests in subtropical China are characterized by a diverse tree species community that transitions from conifers in the early stage of restoration, to deciduous broadleaf and evergreen broadleaf species in its mid and late stages; this provides an excellent opportunity to investigate the influences of different tree functional groups on ESs and the trade-offs among them. Our results showed that late-forest had a greater capacity to supply higher and more evenly distributed benefits of ESs than did early or mid-stage restored forests. We also found that the magnitude of trade-offs between paired ESs changed with the stage of restoration. Furthermore, the variation of the beneficiary in critical trade-offs corresponded to the patterns of change in benefits of specific ESs. Trade-offs between plant diversity and other ESs were significantly influenced by tree functional group, in that the deciduous broadleaved species had significant positive effects whereas the conifer and evergreen broadleaved species had negative effects. We conclude that accurate prediction and management of ESs in restoration forests should explicitly account for tree functional groups, in addition to the effects from combined trade-offs among multiple ESs. [ABSTRACT FROM AUTHOR]

[Display omitted] • A spatially explicit planning model was developed to adjust forest age structure. • Smart management could improve stand volume and carbon stocks. • Social preferences had less effects on stand quality after forest structure adjustment. • Forest management was more sensitive to carbon prices than timber prices. Forest farms are the main body of forest management at the landscape-scale in China, and have long sought ways to jointly maximize timber production and other ecosystem services. Carbon sequestration is of particular interest because China has established the goal of becoming carbon neutral by 2060. However, optimizing the balance between timber production and carbon sequestration is a challenge due to a lack of methods that account for the spatial arrangement of forest management activities within a landscape. This study developed a multi-objective planning model for forest management approaches to promote natural forest regeneration, adjusting the stand age structure of plantation forests to an even distribution across a landscape, and quantified the effects of social preferences and market prices on optimal management. The results show that depending on the dominant ecosystem services provided by the forests, forest management could promote an increased timber volume and stand carbon stock that is sustainable in the long-term. Social preferences have a relatively small influence on optimal management plans after forests are restructured to a normal forest age class distribution. In addition, forest management dynamics are more sensitive to carbon prices than timber prices. Hence, the spatial allocation of different management practices and forest restructuring, rather than protecting forests or managing them less intensively, is more effective for improving forest carbon stocks. More importantly, an urgent need also exists to increase the carbon price to guide and strengthen the attention of forest managers to forest carbon sequestration, with the goal of achieving a win–win strategy. [ABSTRACT FROM AUTHOR]

• Ordered weighted averaging method was used to handle ecosystem service trade-offs. • Ecological sources were selected based on the conservation efficiency. • Proposed a resistance surface framework considering the characteristics of the karst. • Ecological security patterns showed that large-scale farmland hampered connectivity. The construction of ecological security patterns (ESPs) from the perspective of ecosystem services is vital in regional sustainability. However, previous approaches have often not considered the complex trade-offs between ecosystem services during the construction of ESPs. Taking the Daning river basin in karst areas of southwest China as our study area, we improve the current methodological framework to construct an ESP by integrating ecosystem service trade-offs, typical characteristics of the karst area, and circuit theory. The multi-criterion decision method of ordered weighted averaging was used to balance ecosystem service trade-offs and to determine the ecological sources with the optimum conservation efficiency. The resistance surface based on land use was modified by the nighttime light intensity and rocky desertification index. Circuit theory was then applied to identify corridors, pinch points and barriers. The results showed that the spatial patterns of the six ecosystem services (food provision, carbon sequestration, soil retention, water yield, habitat quality and ecological recreation) varied considerably within the study area. By comparing the conservation efficiencies, scenario 5 was selected as the optimal scenario, and the conservation efficiencies of six ecosystem services within the ecological sources were > 1 and were more balanced, illustrating the flexibility and feasibility of our method. The modified resistance surface comprehensively reflected the dual influence of human activity and rocky desertification on ecosystems. The ESP in the Daning river basin included 34 ecological sources, 66 key corridors, ecological corridors with an area of 957 km2, and 100 pinch points and 36 barriers distributed on the corridors. The ecological sources mostly covered by forest land were mainly distributed in the north and east of the study area. The key and ecological corridors were densely located in the south and central areas, where pinch points were also mainly concentrated. Barriers were distributed on the edge of ecological sources and corridors. Based on ESP, the Daning river basin was divided into ecologically important areas in northern and eastern and ecologically improving areas in central and southern, the corresponding ecological restoration measures were also proposed. In summary, this study makes up for the shortcomings of constructing ESPs by the simple spatial overlaying of ecosystem services. Our findings could also effectively enhance the robustness and sustainability of ESPs in karst areas. [ABSTRACT FROM AUTHOR]

• Mean concentration and annual output fluxes of DOC were the highest in the deciduous broadleaved forest. • Mean concentration of TDN tended to increase but annual TDN output fluxes decreased with forest restoration. • DOC cycle in the deciduous broadleaved forest was relatively open whereas TDN cycle turned to be closed as forest restored. In the restoration of subtropical forests, the hydrological fluxes of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) have not been fully investigated in different stages dominated by different tree species. The concentrations of DOC and TDN in rainfall, throughfall, stemflow, and surface runoff were measured for two years in each of the three forests at different restoration stages: early coniferous forest (Pinus massoniana - Lithocarpus glaber), intermediate deciduous broadleaved forest (Choerospondias axillaris), and late evergreen broadleaved forest (L. glaber - Cyclobalanopsis glauca). Input and output fluxes as well as leaching and migration coefficients of DOC and TDN were calculated to examine the nutrient cycling status in the processes of forest restoration. In stemflow, DOC concentrations in the evergreen broadleaved forest differed significantly from those in the coniferous and deciduous broadleaved forests, whereas TDN concentrations differed significantly between the coniferous forest and other two forests. In throughfall, DOC and TDN concentrations were not significantly different among the three forests. The amount of DOC leached was primarily influenced by rainfall and was significantly related to fluxes in throughfall, with the highest value in the deciduous broadleaved forest (57.78 kg C ha−1). However, the amount of TDN leached was affected by rainfall and the absorption of vegetation and was not significantly related to fluxes in throughfall, except for the deciduous broadleaved forest. The highest value of TDN leached was in the coniferous forest (11.90 kg N ha−1). Mean TDN concentration in surface runoff tended to increase but annual TDN output fluxes decreased with forest restoration. However, both mean concentration and annual output fluxes of DOC in surface runoff were the highest in the deciduous broadleaved forest at the intermediate restoration stage. The concentrations were closely related to surface runoff, decomposition rate of litterfall, and soil organic matter content. The annual output fluxes of DOC and TDN in surface runoff were less than 30% of the input in throughfall, indicating nutrient accumulation in subtropical secondary forests. [ABSTRACT FROM AUTHOR]

Afforestation is an effective method to increase carbon (C) sinks and address climate change. It is crucial to understand how the stand growth affects C sequestration capacity, especially when the trade-offs with timber production from plantations have not been fully examined. We used a chronosequence approach to estimate C storage in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) plantations (including the trees, understory, litter, and soils) at seven stand ages (3, 8–11, 16, 21, 25, 29, and 32 years). Ecosystem C storage increased nonlinearly from 76.4 to 282.2 t ha−1 with stand age and was fitted with a logistic model that had a maximum C storage and age of 271.9 t ha−1 and 33 years, respectively, to reach 95% of the maximum stored C. The C increment was mainly contributed by an increase in tree biomass, which ranged from 2.8 to 177.7 t ha−1 and comprised 4–64% of the total ecosystem C. Live root C (sum of the stump, coarse, and fine root C) showed a logistic increase from 2.0 to 26.3 t ha−1 with stand age and constituted 2.5–9.3% of ecosystem C. Understory plants and litter represented a small pool (<2% of ecosystem C). The C storage in shrubs and litter slightly increased, while that in herbs decreased as the stands aged. Soil C storage was an important and relatively stable pool, ranging from 69.6 to 130.1 t ha−1. Stand volume was also best fitted with a logistic model with a maximum value of 552.6 m3 ha−1. Additionally, the time needed to reach 95% of the maximum volume was 25 years. Hence, extending the rotation age to over 30 years for Chinese fir plantations could potentially maximize the synergistic benefits of C storage to mitigate climate change and obtain timber products for economic profit. [Display omitted] • Chinese fir plantations have high carbon (C) sequestration capacity. • Accumulation of ecosystem C was mainly contributed by increase in tree biomass C. • Soil C storage remained relatively stable except for stand at age of 21 years. • Rotation extension enhances ecosystem C storage and large-trees' timber production. [ABSTRACT FROM AUTHOR]

Establishing forest plantations is an important solution to the growing conflict between an increasing human population and mounting pressure to protect the natural forests, as plantations also harbor great potential for providing multiple ecosystem services (ESs). However, because of the trade-offs between multiple ESs and the conflicts between different stakeholders, the sustainable management of plantations has been exceedingly challenging. Especially in recent years, with China's emphasis on ecological civilization construction and sustainable development, forestry departments have begun to focus on long-term ecological benefits, which conflict with farmers' attention to short-term economic gains. In this study, we quantified 15 field-based ES indicators from the data measured in Chinese fir (Cunninghamia lanceolata) plantations aged 4 to 32 years. Corresponding to the concerns of two different stakeholders (forestry departments and farmers), we calculated ES-multifunctionality with different thresholds under four management scenarios: equal weight, production only, production multifunctionality, and supporting multifunctionality. Our results suggested pronounced stand age effects on both individual ESs and ES-multifunctionality of plantations. For individual ESs, stand age had a greater impact on provisioning services than on supporting services. High degree of trade-offs existed between plantation provisioning ESs and soil nutrient supporting ESs, and between water relevant ESs and the other ESs. With respect to ES-multifunctionality, the values under different scenarios were all augmented with stand age, but to differing degrees. The values for supporting multifunctionality were higher than those of production multifunctionality and production only before 21 years of stand development, but completely reversed once the fir plantations reached an age of 25 years. Finally, several stage-based plantation management recommendations are proposed to minimize conflicts between different stakeholders. Our results combined measures of temporal stability and multifunctionality, thereby providing valuable and timely insight into the multifunctional stability of plantations represented by Chinese fir., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Background: Mixed forests are believed to enhance ecosystem functioning and sustainability due to complementary resource use, environmental benefits and improved soil properties. The facilitation between different species may induce overyielding. Meanwhile, the species-specific fine root foraging strategies and tradeoffs would determine the structure and dynamics of plant communities. Here the aim was to investigate the admixing effects of fine-root biomass, vertical distribution and morphology in Pinus massoniana-Cinnamomum camphora mixed plantations and corresponding monocultures at 10-, 24- and 45-year old stands., Results: The fine root biomass in the Pinus-Cinnamomum mixed forest exerted a certain degree of overyielding effect. These positive admixing effects, however, did not enhance with forest stand development. The overall relative yield total ranged from 1.83 and 1.51 to 1.33 in 10-, 24- and 45-year-old stand, respectively. The overyielding was mainly attributed to the over-performance of late successional species, Cinnamomum, in mixed stands. The vertical fine root biomass distribution model showed fine roots of pioneer species, Pinus, shifted to the superficial layer when mixed with Cinnamomum. Furthermore, the specific root length (SRL) of Pinus was significantly higher in Pinus-Cinnamomum mixed stands than that in monocultures, and the magnitude of differences increased over time. However, the vertical fine-root distribution and SRL for Cinnamomum did not show significant differences between monoculture and mixtures., Conclusions: Our results indicated that the magnitude of fine root overyielding in mixed forests showed a high degree of consistency with the total amount of fine root biomass itself, suggesting the overyielding effects in mixed forests were correlated with the degree of belowground interaction and competition degree involved. The late successional species, Cinnamomum, invested more carbon to belowground by increasing the fine root biomass in mixtures. While the pioneer species, Pinus, adapted to the presence of the species Cinnamomum by modification of vertical distribution and root morphological plasticity in the mixtures. These species-specific fine root foraging strategies might imply the differences of forest growth strategies of co-occurring species and contribute to the success and failure of particular species during the succession over time.