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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]

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]

Highlights • Up-regulated P2X 4 in DRG SGCs companied with diabetic neuropathic pain. • Osthole decreased up-regulated P2X 4 and hyperalgesia in diabetic rats. • Osthole inhibited SGC activation in DRG of diabetic rats. • Osthole alleviate diabetic neuropathic pain by inhibiting P2X 4. Abstract Diabetes mellitus (DM) is considered the primary cause of neuropathic pain. Osthole (7-methoxy-8[3-methylpent 2-enyl]coumarin) is a component extracted from Cnidium monnieri (L.) cusson plant seeds and has anti-inflammatory and anti-oxidative properties. The aim of the present study was to investigate the effects of osthole on diabetic neuropathic pain (DNP) involving the P2X 4 receptor on satellite glial cells (SGCs) in the dorsal root ganglia (DRG) of type 2 diabetic rats. These data showed that the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) in DM rats were lower than those in control rats. MWT and TWL in DM rats treated with osthole were higher compared with those in untreated DM rats. The expression levels of P2X 4 mRNA and protein in the DRG of DM rats were higher compared with those in the control rats, while those in DM rats treated with osthole were significantly lower compared with those in the untreated DM rats. Osthole treatment decreased the co-expression levels of P2X 4 and glial fibrillary acidic protein (GFAP) and reduced the up-regulated expression of interleukin-1 beta (IL-1β), tumour necrosis factor-α (TNF-α), brain-derived neurotrophic factor (BDNF) and phosphorylated-p38MAPK and enhanced the down-regulation of IL-10 in DM rats. Thus, osthole treatment may act on the P2X 4 receptor to alleviate the mechanical and thermal hyperalgesia in DM rats. [ABSTRACT FROM AUTHOR]

Carbon and water cycles in forest ecosystems are tightly coupled, but global warming-induced soil and atmospheric droughts alter the coupling, thereby greatly increasing uncertainty in predicting carbon and water cycles. Therefore, a carbon–water coupled model (TRIPLEX-CW-Flux) was developed, and an R package (rTRIPLEXCWFlux) was created to facilitate model application. TRIPLEX-CW-Flux integrates vapor pressure deficit and soil moisture into a stomatal conductance submodule to estimate forest carbon and water fluxes. Prediction accuracy of TRIPLEX-CW-Flux and rTRIPLEXCWFlux application were evaluated in a Chinese fir (Cunninghamia lanceolata) plantation. Simulated net ecosystem production (NEP) and evapotranspiration (ET) were in good agreement with flux observations (R 2 : 0.76 for NEP ; 0.71 for ET). Thus, the TRIPLEX-CW-Flux model can be used to predict and quantify effects of global warming-induced droughts on forest carbon and water cycles. The open-access rTRIPLEXCWFlux package facilitates estimations of carbon sequestration and water consumption in forest ecosystems using the observed flux data. • A physiological process model that couples carbon and water flux was developed. • Both atmospheric and soil drought stress were also integrated into the model. • An R package was encoded for the model to predict forest carbon and water flux. • The simulated values were comparable to the flux data observed in the forest. • This R package can be used to evaluate forest functions under climate change. [ABSTRACT FROM AUTHOR]

• Combination therapy has gradually become a therapeutic trend, and studies on the intervention program combining fecal microbial transplantation and aerobic exercise are novel. • Fecal microbial transplantation and aerobic exercise can effectively improve intestinal dysfunction after spinal cord injury and further enhance neurological function. • Researchers may be able to use the intestinal system or other organs as intervention targets to achieve repair of spinal cord injury. Spinal cord injury (SCI) leads to severe intestinal dysfunction and decreased motility. There is an interaction between the intestine and the nervous system, intestinal intervention through microbial regulation and exercise is a potential treatment option for spinal cord injury. We investigated the effects of swimming rehabilitation training combined with fecal microbial transplantation on intestinal as well as neurological functions in rats with spinal cord injuries, and explored the potential mechanisms. The animals were randomly divided into five groups: sham-operated control group (Sham), spinal cord injury only group (SCI), swimming training group (Swimming), fecal microbial transplantation group (FMT) and combined interventions group (Combined). Behavioral assessments, pathological and immunological analyses were performed after the interventions. Compared to rats in the spinal cord injury group, rats subjected to swimming training, fecal microbial transplantation and combined interventions group exhibited improved intestinal transit, barrier functions, motility, and motor conduction pathway conductivity(P < 0.05). The combined interventions group had better outcomes(P < 0.01). In addition, combined interventions significantly suppressed inflammatory factor levels (P < 0.05) in the colon and spinal cords and significantly protected forefoot motor neurons (NeuN) in the spinal cord injury area, inhibiting astrocyte activation and reducing the expressions of the signature glial fibrillary acidic protein (GFAP) and markers of microglia (Iba-1) at the lesion site(P < 0.05). In conclusion, all effects of combined swimming training and fecal microbial transplantation interventions were superior to swimming training or fecal microbial transplantation alone. Swimming training and fecal microbial transplantation interventions have a synergistic effect on the recovery of intestinal function and motility after spinal cord injury. The mechanism of mutual facilitation between gut function and motility may be related to the brain-gut axis interaction. [ABSTRACT FROM AUTHOR]

Low P-containing wastewaters (LPWs) exhibit huge P recovery potential, considering their larger volume. P recovery via CaP crystallization using apatite as seed is documented as being potentially well suited for LPWs. However, its responsible mechanisms remain a subject for debate. Taking hydroxyapatite (HAP) as the seed of LPWs, this paper conducted HAP adsorption/dissolution experiments, titration experiments, and P recovery experiments to distinguish the primary responsible mechanism. Results showed that it was HAP dissolution, not P adsorption, that occurred when the initial P concentration was no higher than 5 mg/L, ruling out adsorption mechanism of P recovery from LPWs using HAP as the seed. Significant OH− consumption and rapid P recovery occurred simultaneously within the first 60 s in titration experiments, suggesting CaP crystallization should be responsible for P recovery. Moreover, the continuous increase in P recovery efficiency with seed dosages observed in P recovery experiments seemed to follow well the mechanism of pre-nucleation ion clusters (PNCs) aggregation. During PNCs aggregation, P aggregates with Ca2+ quickly, generating CaP PNCs; then, CaP PNCs aggregate with seed particles, followed by CaP PNCs fusion, and ultimately transform into fines attached to the seed surface. PNCs' aggregation mechanism was further supported by a comparison of seed SEM images before and after P recovery, since denser and smaller rod-shaped fines were observed on the seed surface after P recovery. This study suggests that PNCs' aggregation is the dominant mechanism responsible for the recovery of P from LPWs via CaP crystallization using HAP as the seed. [ABSTRACT FROM AUTHOR]

• TsMS combined with EA treatment significantly improved function recovery. • Combined treatment reduces gastrocnemius atrophy and improves nerve conduction. • Combined treatment alters miRNA expression within dorsal root ganglion. • Combined treatment promote axonal regeneration via miR-539-5p/Sema3A/PlexinA1. Enhancing axonal regeneration is one of the most important processes in treating nerve injuries. Both magnetic and electrical stimulation have the effect of promoting nerve axon regeneration. But few study has investigated the effects of trans -spinal magnetic stimulation (TsMS) combined with electroacupuncture (EA) on nerve regeneration in rats with sciatic nerve injury. In this study, we compared the improvement of neurological function in rats with sciatic nerve crush injuries after 4 weeks of different interventions (EA, TsMS, or TsMS combined with EA). We further explored the morphological and molecular biological alterations following sciatic nerve injury by HE, Masson, RT-PCR, western blotting, immunofluorescence staining and small RNA transcriptome sequencing. The results showed that TsMS combined with EA treatment significantly promoted axonal regeneration, increased the survival rate of neurons, and suppressed denervation atrophy of the gastrocnemius muscle. Subsequent experiments suggested that the combination treatment may play an active role by mediating the miR-539-5p/Sema3A/PlexinA1 signaling axis. [ABSTRACT FROM AUTHOR]

Secondary lung injury after SCI is a major cause of patient mortality, with apoptosis playing a key role. This study aimed to explore the impact of treadmill training and miR145-5p on the MAPK/Erk signaling pathway and apoptosis in rats with complete SCI. SD rats were used to establish T10 segmental complete SCI models and underwent treadmill training 3, 7, or 14 days postinjury. Various techniques including arterial blood gas analysis, lung wet/dry weight ratio, HE staining, immunofluorescence staining, immunohistochemical staining, qRT-PCR, and Western blotting were employed to assess alterations in lung function and the expression levels of crucial apoptosis-related factors. In order to elucidate the specific mechanism, the impact of miR145-5p on the MAPK/Erk pathway and its role in apoptosis in lung cells were confirmed through miR145-5p overexpression and knockdown experiments. Following spinal cord injury (SCI), an increase in apoptosis, activation of the MAPK/Erk pathway, and impairment of lung function were observed in SCI rats. Conversely, treadmill training resulted in a reduction in alveolar cell apoptosis, suppression of the MAPK/Erk pathway, and enhancement of lung function. The gene MAP3K3 was identified as a target of miR145-5p. The influence of miR145-5p on the MAPK/Erk pathway and its impact on apoptosis in alveolar cells were confirmed through the manipulation of miR145-5p expression levels. The upregulation of miR145-5p in spinal cord injury (SCI) rats led to a reduction in MAP3K3 protein expression within lung tissues, thereby inhibiting the MAPK/Erk signaling pathway and decreasing apoptosis. Contrarily, rats with miR145-5p knockdown undergoing treadmill training exhibited an increase in miR145-5p expression levels, resulting in the inhibition of MAP3K3 protein expression in lung tissues, suppression of the MAPK/Erk pathway, and mitigation of lung cell apoptosis. Ultimately, the findings suggest that treadmill training may attenuate apoptosis in lung cells post-spinal cord injury by modulating the MAP3K3 protein through miR145-5p to regulate the MAPK/Erk signaling pathway. [ABSTRACT FROM AUTHOR]

Aims: Although plant–microbial interactions are essential to sustain terrestrial ecosystem functions, root–microbial interactions remain poorly understood. Therefore, understanding how functional trait diversity of fine roots mediates soil microbial diversity and composition provides insightful information to maintain forest ecosystem functions. Methods: A total of 87 plots with 1–12 tree species richness gradient in three subtropical secondary forests were selected. Functional trait diversity (functional dispersion, FDis, and community-weighted mean, CWM) of fine roots was quantified. Soil microbial diversity and community composition were analyzed by high-throughput Illumina sequencing. Results: Bacterial and fungal richness was primarily predicted by CWM of root diameter (CWM_diam) in the humus horizon, but by FDis of specific root length (FDis_SRL) in the mineral horizon. Microbial community composition in two soil horizons increased with FDis_SRL, including the abundance of copiotrophic bacteria (r-strategists, e.g., Proteobacteria, Actinobacteria), Chloroflexi, saprotrophs and pathogens. FDis_SRL was also indirectly mediated microbial richness and composition via decreasing carbon:nitrogen ratio and increasing pH, total nitrogen, total and available phosphorus contents. Conclusions: Overall, functional trait diversity of fine roots plays a pivotal role in mediating soil microbial richness and community composition in subtropical secondary forests. These results deepen our understanding of the important role of plant–microbial interactions in terrestrial biogeochemical processes. [ABSTRACT FROM AUTHOR]

Although stand age affects biomass partitioning and allometric equations, the size of these effects and whether it is worth incorporating stand age into allometric equations, requires further attention. We sampled a total of 90 trees for 10 Chinese fir (Cunninghamia lanceolata) plantations at seven stand age classes to obtain the data of tree component biomass using destructive harvesting. A multilevel modeling approach was applied to examine how stand age effects differ among tree components and predictor variables (diameter at breast height, DBH and tree height, H). Age class-specific allometric equations and the best fitting generalized equation that included stand age as a complementary variable were developed for each tree component. Large differences in both the intercept and slope for different stand age classes indicated that stand age affected allometric models. Branch and leaves were more sensitive to the environment and were the tree components most affected by stand age. Age class-specific allometric equations fitted well (R2 > 0.65, p < 0.001) using DBH and the combined form DBH2H as predictor variables. Including stand age as a complementary variable improved the fit of generalized allometric equations. Stem, aboveground and total tree biomass predicted by the multilevel model and generalized equation were comparable to the observed data. However, the multilevel model and generalized equations had a relatively low predictive capacity for branch, leaf and root biomass. These results could improve our capacity to evaluate carbon sequestration and other ecosystem functions in plantations. [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]

Increased availability of soil phosphorus (P) has recently been recognised as an underlying driving factor for the positive relationship between plant diversity and ecosystem function. The effects of plant diversity on the bioavailable forms of P involved in biologically mediated rhizospheric processes and how the link between plant and soil microbial diversity facilitates soil P bioavailability, however, remain poorly understood.This study quantified four forms of bioavailable P (CaCl2‐P, citric‐P, enzyme‐P and HCl‐P) in mature subtropical forests using a novel biologically based approach, which emulates how rhizospheric processes influence the release and supply of available P. Soil microbial diversity was measured by Illumina high‐throughput sequencing.Our results suggest that tree species richness significantly affects soil microbial diversity (p < 0.05), increases litter decomposition, fine‐root biomass and length and soil organic carbon and thus increases the four forms of bioavailable P. A structural equation model that links plants, soil microbes and P forms indicated that soil bacterial and fungal diversity play dominant roles in mediating the effects of tree species richness on soil P bioavailability.An increase in the biodiversity of plants, soil bacteria and fungi could maintain soil P bioavailability and alleviate soil P limitations. Our results imply that biodiversity strengthens plant and soil feedback and increases P recycling. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

• Long-term iTBS ameliorated neurological deficits and neurological damage. • Long-term iTBS could consistently improve the neuronal microenvironment. • iTBS treatment altered miRNA expression in the peri-infarcted area. • iTBS inhibit neuronal apoptosis via miR-34c-5p/p53/Bax signaling pathway. To investigate intermittent theta-burst stimulation (iTBS) effect on ischemic stroke and the underlying mechanism of neurorehabilitation, we developed an ischemia/reperfusion (I/R) injury model in Sprague-Dawley (SD) rats using the middle cerebral artery occlusion/reperfusion (MCAO/r) method. Next, using different behavioral studies, we compared the improvement of the whole organism with and without iTBS administration for 28 days. We further explored the morphological and molecular biological alterations associated with neuronal apoptosis and neuroinflammation by TTC staining, HE staining, Nissl staining, immunofluorescence staining, ELISA, small RNA sequencing, RT-PCR, and western blot assays. The results showed that iTBS significantly protected against neurological deficits and neurological damage induced by cerebral I/R injury. iTBS also significantly decreased brain infarct volume and increased the number of surviving neurons after 28 days. Additionally, it was observed that iTBS decreased synaptic loss, suppressed activation of astrocytes and M1-polarized microglia, and simultaneously promoted M2-polarized microglial activation. Furthermore, iTBS intervention inhibited neuronal apoptosis and exerted a positive impact on the neuronal microenvironment by reducing neuroinflammation in cerebral I/R injured rats. To further investigate the iTBS mechanism, this study was conducted using small RNA transcriptome sequencing of various groups of peri-infarcted tissues. Bioinformatics analysis and RT-PCR discovered the possible involvement of miR-34c-5p in the mechanism of action. The target genes prediction and detection of dual-luciferase reporter genes confirmed that miR-34c-5p could inhibit neuronal apoptosis in cerebral I/R injured rats by regulating the p53/Bax signaling pathway. We also confirmed by RT-PCR and western blotting that miR-34c-5p inhibited Bax expression. In conclusion, our study supports that iTBS is vital in inhibiting neuronal apoptosis in cerebral I/R injured rats by mediating the miR-34c-5p involvement in regulating the p53/Bax signaling pathway. [ABSTRACT FROM AUTHOR]

• Only stem harvest can avoid P loss due to<23% P stock allocated in stem. • Higher P fluxes showed stronger P acquisition and recycling in mature plantations. • The combined use of acquisition and recycling strategies favors P biological cycle. • The maximum annual P uptake by trees occurred at stand age of 22 years. The cycling dynamics and supply–demand balance of nutrients can provide useful information for improving the management of tree plantations and maintaining their long-term productivity. Phosphorus (P) is an essential nutrient for plant growth; however, its cycling characteristics and availability in soils along different stand developmental stages remain unclear, especially in intensively managed plantations. In this study, we examined the stocks, distribution, flux, and supply–demand balance of P across a chronosequence of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.; Taxodiaceae) plantations aged 3, 8–11, 16, 21, 25, 29, and 32 years. <22.18% tree P stock allocated for stem across a chronosequence, suggesting that only stem harvest could return more than three-quarters of tree P stock to soil. The annual P resorption, P return, and P-use efficiency increased with stand age, indicating strong P recycling. Indicators of P acquisition and recycling strategies significantly increased with stand age and promoted P fluxes. The combination of acquisition and recycling strategies might favor the entrainment of P into the biological cycle. With the increase in stand age, the available soil P stocks initially decreased and then increased after 11 years, while the annual P uptake increased at first and then stabilized after 22 years. Based on the best fitted model, the lower soil P supply and higher tree P demand in 9- to 40-year-old plantations revealed that timely and appropriate fertilization could enhance soil P supply and improve stand productivity. This work provides crucial information about the time of fertilization and appropriate harvest methods for the sustainable management of forest P nutrition. [ABSTRACT FROM AUTHOR]

Glycoprotein 120 (gp120) is an HIV envelope glycoprotein. Gp120 can directly stimulate the primary sensory afferent neurons and cause hyperalgesia. The P2X 3 receptor in dorsal root ganglia (DRG) is involved in the transmission of pain. In this study, we aimed to explore the role of the P2X 3 receptor in gp120-induced neuropathic pain. Our data showed that mechanical and thermal hyperalgesia in rats treated with gp120 were increased compared to those in the control group. The expression levels of the P2X 3 mRNA and protein in rats treated with gp120 were higher than those in the control group. The P2X 3 antagonist A317491 decreased mechanical hyperalgesia and thermal hyperalgesia and the up-regulated expression levels of P2X 3 mRNA and protein in rats treated with gp120. A317491 decreased ERK1/2 phosphorylation levels in the gp120-treated rat DRG. In addition, P2X 3 agonist α,β-methylene ATP (α,β-meATP)-activated currents in DRG neurons cultured with gp120 were higher than those in control neurons. The inhibitory effect of A317491 on α,βme-ATP-induced currents in DRG neurons from the gp120-treated neurons was larger than that for control neurons. Molecular docking data showed that A317491 may be acted in the gp120 protein to inhibit the gp120 initiated the P2X 3 activation, decrease the sensitizing DRG primary afferents and reduce the signal transmission of neuropathic pain in gp120-treated rats. Therefore, the inhibition of the P2X 3 receptor in rat DRG neurons relieved gp120-induced mechanical hyperalgesia. [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]

[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]

Neutral‐theory‐based stochastic and niche‐theory‐based determinative processes are commonly used to explain the mechanisms of natural community assembly. However, considerable uncertainty remains regarding the relative importance of different ecological processes in shaping forest communities. Functional traits and phylogeny provide important information about plant environmental adaptation strategies and evolutionary history and promise a better mechanistic and predictive understanding of community assembly. Based on nine leaf functional traits and phylogenetic data of 18 dominant species in a Lithocarpus glaber–Cyclobalanopsis glauca evergreen broad‐leaved forest, we analyzed the variation in traits, explored the influence of phylogeny and environment on leaf traits, and distinguished the relative effects of spatial and environmental variables on functional traits and phylogenetic compositions. The results showed the following: (i) Leaf traits had moderate intraspecific variation, and significant interspecific variation existed especially among life forms. (ii) Significant phylogenetic signals were detected only in leaf thickness and leaf area. The correlations among traits both supported "the leaf economics spectrum" at the species and community levels, and the relationships significantly increased or only a little change after removing the phylogenetic influence, which showed a lack of consistency between the leaf functional trait patterns and phylogenetic patterns. We infer the coexistent species tended to adopt "realism" to adapt to their habitats. (iii) Soil total potassium and phosphorus content, altitude, aspect, and convexity were the most critical environmental factors affecting functional traits and phylogenetic composition. Total environmental and spatial variables explained 63.38% of the variation in functional trait composition and 47.96% of the variation in phylogenetic structures. Meanwhile, the contribution of pure spatial factors was significantly higher than that of the pure environment. Stochastic processes played dominant roles in driving community functional trait assembly, but determinative processes such as environmental filtering had a stronger effect on shaping community phylogenetic structure at a fine scale. [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]

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]

• Homogeneous and heterogeneous CaCO 3 precipitation were distinguished using magnetite as seeds. • Increasing SI preferentially promoted heterogeneous crystallization at low SI, but homogeneous at high SI. • High seed dosage and small seed particle size facilitate heterogeneous crystallization. • Heterogeneous nuclei adhered to seed surfaces, exhibiting better settleability than homogeneous ones. Homogeneous and heterogeneous crystallization of CaCO 3 simultaneously occur in seed-induced crystallization during water softening, while suppressing homogeneous crystallization is necessary due to the production of fine particulates that poorly precipitate. However, homogeneous crystallization is difficult to distinguish from heterogeneous crystallization. Consequently, a central focus in improving water softening is understanding their competing activities. In this study, a novel method for distinguishing homogeneous and heterogeneous calcium carbonate crystallization is described that utilizes magnetite as seed particles. Results showed that saturation index (SI) was the primary driver of both homogeneous and heterogeneous crystallizations. Heterogeneous crystallization was preferentially promoted at low SI, while homogeneous crystallization was promoted at high SI. The highest suppression effect to homogeneous crystallization occurred at SI of about 1.01. Seed dosage and mean particle size were the primary parameters related to the competition of the crystallization types. Higher seed dosage and smaller seed particle sizes promoted heterogeneous crystallization and suppressed homogeneous crystallization. Due to the good adaptability of heterogeneous crystallization at low SI, the absorption of CO 2 from the air into the solutions also improved the efficiency of hardness removal. The introduction of seed particles did not change crystalline product phases, with calcite being the only observed phase and possessing rhombohedral forms with highly regular and smooth edges. Water softening pilot test results showed that SI of 1.5 was more favorite for CaCO 3 layer formation on seed surface and hardness removal in comparison with SI of 1.0 and 2.0. Overall, the results from this study demonstrate that the introduction of seed particles is a promising approach to suppress the homogeneous crystallization of CaCO 3. Moreover, these results can serve as a framework for improved seed-induced crystallization during water softening. [Display omitted] [ABSTRACT FROM AUTHOR]

Primary or secondary forests around the world are increasingly being converted into plantations. Soil microorganisms are critical for all biogeochemical processes in ecosystems, but the effects of forest conversion on microbial communities and their functioning remain unclear. Here, we conducted a meta‐analysis to quantify the impacts that converting forests to plantations has on soil microbial communities and functioning as well as on the associated plant and soil properties. We collected 524 paired observations from 138 studies globally. We found that conversion leads to broad range of adverse impacts on soils and microorganisms, including on soil organic carbon (−24%), total nitrogen (−29%), bacterial and fungal biomass (−36% and −42%, respectively), microbial biomass carbon (MBC, −31%) and nitrogen (−33%), and fungi to bacteria ratio (F:B, −16%). In addition, we found impacts on the ratio of MBC to soil organic C (qMBC, −20%), microbial respiration (−18%), N mineralization (−18%), and enzyme activities including β‐1,4‐glucosidase (−54%), β‐1,4‐N‐acetylglucosaminidase (−39%), and acid phosphatase (ACP; −34%). In contrast, conversion to plantations increases bacterial richness (+21%) and microbial metabolic quotient (qCO2, +21%). The effects of forest conversion were consistent across stand ages, stand types, and climate zone. Soil C and N contents as well as the C:N ratio were the main factors responsible for the changes of microbial C, F:B, and bacterial richness. The responses of qCO2, N mineralization, and ACP activity were mainly driven by the reductions in F:B, MBC, and soil C:N. Applying macro‐ecology theory on ecosystem disturbance in soil microbial ecology, we show that microbial groups shifted from K to r strategists after conversion to plantations. Our meta‐analysis underlines the adverse effects of natural forests conversion to plantations on soil microbial communities and functioning, and suggests that the preservation of soil functions should be a consideration in forest management practices. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of ecosystem service (ES) bundles and their socioecological drivers is vital for ecological management and policymaking. However, the underlying mechanisms are still unclear due to less attention being paid to their historical dynamics. Taking the Three Gorges Reservoir Area as a case study, this study used Pearson parametric correlation analysis, k-means clustering analysis, and redundancy analysis to investigate how the ESs and their interactions have changed over time, and to identify historical spatial patterns of ES bundles and their associations with socioecological drivers. Results showed that: (1) most ESs improved over time but soil retention, water yield, and habitat provision showed slightly decreasing trends; (2) intensive agriculture and advances in technology diminished potential ES trade-offs related to food production, while the decrease in soil retention led to a decline in its synergistic relationships with water yield and nitrogen retention; (3) three ES bundles were identified at the watershed scale. The trajectory of each ES bundle could be attributed to the common effects of ecological projects and rapid urbanization. In particular, ecological projects have promoted the transformation of the ES bundle to the direction of high supply and low trade-off, yet trade-offs between ESs have not significantly improved because of constant urban expansion in a major city and its surrounding area; (4) the socioecological drivers determining ESs and ES bundles were also time-dependent, with the ratio of forest to land, slope, and population density being the major drivers. However, other random drivers (e.g., climate change) should also be highlighted as they generate great uncertainty for predicting future ES bundles and further ES management. Overall, our results advocate the historical assessment of the relationships between multiple ESs and socioecological drivers and emphasize the necessity of embracing a historical dynamic perspective in the sustainable management of ESs. [Display omitted] • Both ecosystem services (ESs) and their interactions changed over time. • Three ES bundles were identified and mapped for each time point. • Forest to land ratio, slope, and population density were the major drivers. • Analyzing historical spatial patterns of ES bundles is fundamental for their future management. [ABSTRACT FROM AUTHOR]

The mechanism whereby tree species richness and identity affect the production of fine roots (≤ 2 mm) in forests remains controversial. Complementarity effects (via resource partitioning and facilitation, CEs) and selection effects (that is, dominant of species with particular traits, SEs) are the two hypotheses to explain biodiversity effects on ecosystem functions. This study aimed to (1) examine how tree species diversity affects fine root production and (2) disentangle the complementarity effect and the selection effect on the relationship between biodiversity and fine root production. A total of 60 tree clusters with 15 combinations of diversity gradients consisting of 1–4 tree species (Pinus massoniana, Choerospondias axillaris, Cyclobalanopsis glauca and Lithocarpus glaber) were established in subtropical forests. The sequential soil core and ingrowth core methods were used in each cluster to measure fine root biomass and productivity. Fine root production increased with increase in tree species richness. The biodiversity effects on fine root production mostly resulted from CEs. In the nongrowing season, in most cases, the CE on biomass was positive and became stronger as richness increased, but the opposite situation was observed in the growing season. The strong positive and negative effects of the proportions of C. glauca and L. glaber in the tree clusters on fine root biomass, CEs and SEs, suggest the coordinated action of species diversity and identity in modulating biodiversity effects on belowground processes. [ABSTRACT FROM AUTHOR]

Stand development affects soil properties, nitrogen (N) dynamics, and soil microbial community composition, but the question remains whether differences in N mineralization rates are mirrored by the abundance of relevant functional genes. In this study, we used the 15N pool-dilution method to estimate N mineralization (i.e. , ammonification and nitrification) rates across a Chinese fir (Cunninghamia lanceolata) chronosequence, with stands aged 7, 16, 29, 36, and >80 years. Gene copy numbers of bacteria (16S rRNA), fungi (ITS), ammonia-oxidizing archaea (AOA) and bacteria (AOB) (amoA), denitrifiers (nirS , nirK), N 2 fixers (nifH) and organic N decomposers (chiA) were quantified by qPCR. Gross ammonification and nitrification rates increased linearly with stand age in the topsoil (0–5 cm depth) and were strongly positively correlated with the abundance of the bacterial 16S rRNA gene and AOA amo A, respectively. Higher net nitrification but lower NO 3 − immobilization rates in older stands (32 and > 80 years) drove higher N availability for vegetation than in young stands (7 years). Older stands also had higher rates of NH 4 + consumption than younger stands due to the increased fungal ITS abundance and higher microbial biomass N (MBN), and AOA amoA was more abundant and active than AOB amoA due to the more acid conditions characteristic of mature forests. Redundancy analysis showed that functional gene abundance was strongly affected by soil properties such as pH, NH 4 +-N content, and MBN. We also found that microbial N storage potential was lower, and the NO 3 −-N leaching and gaseous N loss potential were higher in older stands than in younger stands. Collectively, stand developmental stage gave rise to the observed spatial gradient of gross ammonification and nitrification rates by altering the abundance of microbial functional genes, which affected plantation productivity via its modulation of the supply of bioavailable N. [Display omitted] [ABSTRACT FROM AUTHOR]

The importance of species richness to ecosystem functioning and services is a central tenet of biological conservation. However, most of our theory and mechanistic understanding is based on diversity found aboveground. Our study sought to better understand the relationship between diversity and belowground function by studying root biomass across a plant diversity gradient. We collected soil cores from 91 plots with between 1 and 12 aboveground tree species in three natural secondary forests to measure fine root (≤ 2 mm in diameter) biomass. Molecular methods were used to identify the tree species of fine roots and to estimate fine root biomass for each species. This study tested whether the spatial root partitioning (species differ by belowground territory) and symmetric growth (the capacity to colonize nutrient‐rich hotspots) underpin the relationship between aboveground species richness and fine root biomass. All species preferred to grow in nutrient‐rich areas and symmetric growth could explain the positive relationship between aboveground species richness and fine root biomass. However, symmetric growth only appeared in the nutrient‐rich upper soil layer (0–10 cm). Structural equation modelling indicated that aboveground species richness and stand density significantly affected fine root biomass. Specifically, fine root biomass depended on the interaction between aboveground species richness and stand density, with fine root biomass increasing with species richness at lower stand density, but not at higher stand density. Overall, evidence for spatial (i.e. vertical) root partitioning was inconsistent; assumingly any roots growing into deeper unexplored soil layers were not sufficient contributors to the positive diversity–function relationship. Alternatively, density‐dependent biotic interactions affecting tree recruitment are an important driver affecting productivity in diverse subtropical forests but the usual root distribution patterns in line with the spatial root partitioning hypothesis are unrealistic in contexts where soil nutrients are heterogeneously distributed. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a limiting nutrient for plant growth in most forest ecosystems. In response to P deficiency, plants alter root exudates (organic acids, phosphatases, and protons) to increase P bioavailability in soils. However, little is known about how bioavailable P pools (soluble-P, exchangeable-P, hydrolysable-P, and ligand-P extracted by CaCl2, citric acid, enzyme mixture, and HCl solution, respectively) change with stand age, especially for plantation forests. We selected a chronosequence of second-generation Chinese fir [Cunninghamia lanceolata (Lamb.) Hook., Taxodiaceae] plantations with increasing age including 3, 8–11, 16, 20, 25, 29, and 32 years. We measured total P and four bioavailable P pools in organic (O) and mineral horizons, and rhizosphere soil, as well as root exudates in the rhizosphere, litter biomass on the forest floor, and annual P uptake. Soluble-P, exchangeable-P, and ligand-P in the O horizon increased with stand age due to litter accumulation. Exchangeable-P and ligand-P in mineral soil decreased with stand age because of the increasing annual P uptake that depleted inorganic P. Exchangeable-P and ligand-P in the rhizosphere increased with stand age because the decrease in pH and citric acid concentration led to phosphate being more strongly bound to Fe and Al oxyhydroxides. Consequently, the trees' ability for P mobilization decreased with stand age, but the P recycling within the tree increased. Continuous mineralization of hydrolysable-P by acid phosphatase replenished inorganic P pools, especially in solution. The progressive incorporation of P in the biological cycle with increasing tree age indicates that extending rotation periods might be an appropriate measure to increase P supply. [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]

Aims: There is evidence that different facets of biodiversity such as species richness (SR), phylogenetic diversity (PD) and functional diversity (FD) can modulate ecosystem functioning via niche-complementarity or mass-ratio effects, but the support for these hypotheses on fine root biomass remains unclear. Methods: In a tree diversity gradient in subtropical forests (ranging from 2 to 10 tree species), we identified the species identity of fine roots (≤ 2 mm in diameter) using a molecular method. This allowed computation of PD as well as trait-based FD and community-weighted means (CWM) metrics, which were then tested as predictors of fine root biomass. Results: Three metrics (SR, CWM of specific root length and PD) were positively related to root biomass. SR was the best predictor of fine root biomass and its predicting ability depended on stand density. The predicting power of CWM of specific root length varied with the soil nutrient status. Conclusions: Overall, the results supported both tested hypotheses (mass-ratio and niche-complementarity) that seem to be non-mutually exclusive. Furthermore, our findings emphasize that stand density and soil nutrient status are the important variables driving fine root biomass and trait-values. [ABSTRACT FROM AUTHOR]

Plant interactions and feedbacks with soil microorganisms play an important role in sustaining the functions and stability of terrestrial ecosystems, yet the effects of tree species diversity on soil microbial community in forest ecosystems are still not well understood. Here, we examined the effects of tree species richness (1-12 species) and the presence of certain influential tree species (sampling effect) on soil bacterial and fungal communities in Chinese subtropical forests, using high-throughput Illumina sequencing for microbial identification. We observed that beta rather than alpha diversities of tree species and soil microorganisms were strong coupled. Multivariate regression and redundancy analyses revealed that the effects of tree species identity dominated over tree species richness on the diversity and composition of bacterial and fungal communities in both organic and top mineral soil horizons. Soil pH, nutrients and topography were always identified as significant predictors in the best multivariate models. Tree species have stronger effect on fungi than bacteria in organic soil, and on ectomycorrhizal fungi than saprotrophic fungi in mineral topsoil. Concluding, tree species identity, along with abiotic soil and topographical conditions, were more important factors determining the soil microbial communities in subtropical forests than tree diversity per se. [ABSTRACT FROM AUTHOR]

Subtropical broadleaved forests play a crucial role in supporting terrestrial ecosystem functions, but little is known about their belowground soil fungal communities despite that they have central functions in C, N, and P cycles. This study investigated the structures and identified the drivers of soil fungal communities in subtropical deciduous and evergreen broadleaved forests, using high-throughput sequencing and FUNGuild for fungal identification and assignment to the trophic guild. Fungal richness was much higher in the deciduous than in the evergreen forest. Both forests were dominated by Ascomycota and Basidiomycota phyla, but saprophytic fungi were more abundant in the deciduous forest and ectomycorrhizal fungi predominated in the evergreen forest. Fungal communities had strong links to plant and soil properties. Specifically, plant diversity and litter biomass were the main aboveground drivers of fungal diversity and composition in the deciduous forest, while host effects were prominent in the evergreen forest. The belowground factors, i.e., soil pH, water content, and nutrients especially available P, were identified as the primary drivers of soil fungal communities in the broadleaved forests. Co-occurrence network analysis revealed assembly of fungal composition in broadleaved forest soils was non-random. The smaller modularity of the network in the deciduous forest reflects lower resistance to environment changes. Concluding, these results showed that plant community attributes, soil properties, and potential interactions among fungal functional guilds operate jointly on the divergence of soil fungal community assembly in the two broadleaved forest types. [ABSTRACT FROM AUTHOR]

To quantify and assess the processes underlying community assembly and driving tree species abundance distributions(SADs) with spatial scale variation in two typical subtropical secondary forests in Dashanchong state‐owned forest farm, two 1‐ha permanent study plots (100‐m × 100‐m) were established. We selected four diversity indices including species richness, Shannon–Wiener, Simpson and Pielou, and relative importance values to quantify community assembly and biodiversity. Empirical cumulative distribution and species accumulation curves were utilized to describe the SADs of two forests communities trees. Three types of models, including statistic model (lognormal and logseries model), niche model (broken‐stick, niche preemption, and Zipf‐Mandelbrodt model), and neutral theory model, were estimated by the fitted SADs. Simulation effects were tested by Akaike's information criterion (AIC) and Kolmogorov–Smirnov test. Results found that the Fagaceae and Anacardiaceae families were their respective dominance family in the evergreen broad‐leaved and deciduous mixed communities. According to original data and random sampling predictions, the SADs were hump‐shaped for intermediate abundance classes, peaking between 8 and 32 in the evergreen broad‐leaved community, but this maximum increased with size of total sampled area size in the deciduous mixed community. All niche models could only explain SADs patterns at smaller spatial scales. However, both the neutral theory and purely statistical models were suitable for explaining the SADs for secondary forest communities when the sampling plot exceeded 40 m. The results showed the SADs indicated a clear directional trend toward convergence and similar predominating ecological processes in two typical subtropical secondary forests. The neutral process gradually replaced the niche process in importance and become the main mechanism for determining SADs of forest trees as the sampling scale expanded. Thus, we can preliminarily conclude that neutral processes had a major effect on biodiversity patterns in these two subtropical secondary forests but exclude possible contributions of other processes. [ABSTRACT FROM AUTHOR]

Abstract Plant interactions and feedbacks with soil microorganisms play an important role in sustaining the functions and stability of terrestrial ecosystems, yet the effects of tree species diversity on soil microbial community in forest ecosystems are still not well understood. Here, we examined the effects of tree species richness (1–12 species) and the presence of certain influential tree species (sampling effect) on soil bacterial and fungal communities in Chinese subtropical forests, using high-throughput Illumina sequencing for microbial identification. We observed that beta rather than alpha diversities of tree species and soil microorganisms were strong coupled. Multivariate regression and redundancy analyses revealed that the effects of tree species identity dominated over tree species richness on the diversity and composition of bacterial and fungal communities in both organic and top mineral soil horizons. Soil pH, nutrients and topography were always identified as significant predictors in the best multivariate models. Tree species have stronger effect on fungi than bacteria in organic soil, and on ectomycorrhizal fungi than saprotrophic fungi in mineral topsoil. Concluding, tree species identity, along with abiotic soil and topographical conditions, were more important factors determining the soil microbial communities in subtropical forests than tree diversity per se. Highlights • Soil bacterial and fungal beta diversities couples well with tree beta diversity. • Effects of tree identity dominate over richness on bacterial and fungal communities. • Soil pH, nutrient contents and topography were always identified as key drivers. • Tree species have stronger effect on fungi than bacteria in organic soil. • Differential responses of ectomycorrhizal and saprotrophic fungi to tree effects. [ABSTRACT FROM AUTHOR]

Aims: The phylogenetic variations of fine root traits, which are related to plant growth and development as well as to physiological and ecological processes, are not fully understood. This study aimed to: (1) examine how tree species and sampling methodology affect the anatomical, morphological and nutrient traits of fine roots; and (2) determine whether phylogenetic signals affect fine root trait relationships and influence comparison of root traits between the branch order-based and diameter-based cut-off sampling categories.Methods: Fine root samples of 16 subtropical forest tree species were obtained and their anatomical, morphological and nutrient traits were studied. The phylogenetic signals of trait variations were calculated to determine trait relationships.Results: Tree species and sampling methodology significantly affected fine root traits (p < 0.05). Mean root diameters, root tissue density (RTD) and carbon-to-nitrogen ratio were the lowest in the first-order category and highest in the ≤2 mm category. The reverse pattern was found for specific root length, specific root area and nitrogen concentration. Morphological traits showed significant phylogenetic signals; however, nutrient traits did not reflect phylogenetic conservatism. Phylogenetic factors influenced correlations between traits for the first-order root economics spectrum. Root traits were multidimensional and RTD was loaded on a novel phylogenetic principal component analysis.Conclusions: Functional traits of fine roots are multidimensional for subtropical tree species and closely linked to phylogeny. Morphological traits of first order roots showed a much stronger phylogenetic signal than those of roots ≤2 mm (traditionally defined fine roots). The findings improve understanding of root trait strategies in response to environmental changes. [ABSTRACT FROM AUTHOR]

• StemAnalysis package can optionally perform several tasks for any tree species. • Age class determination is a useful approach to address field plague. • The growth trends of outside-bark diameter for a given tree are calculated. • Tree biomass and carbon storage estimated by volume and allometric models. • Height-diameter relationship is fitted with nonlinear models in this package. 1. Accurate information about age dynamics of timber production and carbon storage in forest ecosystems is frequently required by scientists, stakeholders, and policymakers. However, we lack standardized tools to calculate tree growth dynamics, even though this could be obtained by combining typical tree inventory, allometry and stem analysis data. 2. Here we present an integrated R package, StemAnalysis, designed to reconstruct stem growth profiles, construct height-diameter relationships, and consequently to compute growth trends in terms of diameter at breast height (DBH), tree height, stem volume, tree biomass and carbon for an individual tree. 3. StemAnalysis performs a number of standard tasks on input stem analysis data: (i) age class determination; (ii) the cumulative growth, mean annual increment, and current annual increment of outside-bark DBH, tree height, and stem volume are estimated; (iii) height-diameter relationship is fitted with nonlinear models; and (iv) tree biomass and carbon storage estimation from allometric and volume models are calculated. These tasks can be performed optionally. 4. StemAnalysis provides investigators with a set of procedures for exploring tree growth patterns, thereby contributing to the ongoing development of forest multifunctional management sciences. [ABSTRACT FROM AUTHOR]

• Xylem hydraulic traits were highly correlated to tree-level stomatal regulation. • Leaf photosynthetic traits showed no correlations with L cond. • Tree species with higher hydraulic efficiency took isohydric stomatal regulation. • Species inhabiting humid region adopt avoidance strategy in stomatal regulation. • L cond displayed a phylogenetic signal with a low Blomberg's K. Understanding stomatal regulatory mechanisms across various woody species is helpful for explaining their adaptations to diverse environmental conditions. Stomatal opening and closing are driven by the requirements for maintaining water transport integrity and carbon uptake; however, distinguishing which factor plays a dominant role in the regulation of tree-level stomatal behavior has seldom been explored. To address this knowledge gap, we investigated differences in tree-level iso/anisohydric stomatal regulation among various tree species (61 and 59 species, at daily and hourly timescales, respectively) across diverse biomes, and analyzed the association of tree-level stomatal regulation with xylem hydraulic and leaf photosynthetic traits. Xylem hydraulic traits were closely related to tree-level stomatal regulation, whereas leaf photosynthetic traits showed non-significant correlations. Reduction in tree-level stomatal conductance with the same vapor pressure deficit increment (ranging from 0.6 to 2 kPa; L cond), representing the degree of iso/anisohydry, was positively correlated to xylem pressure inducing 50% loss of hydraulic conductivity and vessel diameter, but negatively correlated to the hydraulic safety margin. The associations between xylem hydraulic traits and L cond revealed that tree species with greater xylem hydraulic efficiency were more likely to adopt an avoidance strategy for tree-level stomatal regulation, whereas tolerance strategy occurred in species with a stronger hydraulic safety system. Furthermore, L cond was positively correlated to mean annual precipitation and temperature, suggesting that species inhabiting humid and warm regions rely upon isohydric stomatal regulation. Moreover, L cond displayed a phylogenetic signal, suggesting that variation in L cond has been influenced by evolutionary history. Overall, tree-level stomatal regulation is more closely related to xylem hydraulic traits than to leaf photosynthetic traits, and maintaining water transport integrity rather than fulfilling requirements for carbon uptake is the major factor impacting tree-level stomatal regulation. [ABSTRACT FROM AUTHOR]

Wood density ( WD) is not only an important parameter to estimate aboveground biomass but also an indicator of timber quality and plant adaptation strategies to stressful conditions (i.e., windthrow, pests, and pathogens). This study had three objectives: (1) to compare WD among seven subtropical tree species; (2) to determine how tree growth traits may influence possible differences in WD between the pioneer and shade-tolerant species; and (3) to examine whether or not WD differs by tree social status (dominant vs. suppressed trees) within species. To do this, 70 trees were destructively harvested. From each tree, disks at different stem heights were obtained and subjected to a method of stem analysis to measure whole tree level WD. The results showed that WD differed significantly among the seven species ( p < .001). Their average WD was 0.537 g/cm3, ranging from 0.409 g/cm3 for Choerospondias axillaris to 0.691 g/cm3 for Cyclobalanopsis glauca. The average WD of the four pioneer species (0.497 ± 0.13 g/cm3) was significantly lower ( p < .01) than that of the three shade-tolerant species (0.589 ± 0.12 g/cm3). The WD of the pioneers had a significant positive correlation with their stem diameter at breast height ( DBH), tree height ( H), and tree age, but WD had a significant negative correlation with relative growth rate ( RGR). In contrast, the WD of the shade-tolerant tree species had no significant relationships with DBH, H, tree age, or RGR. The dominant trees of the pioneer species had a higher WD than the suppressed trees, whereas the shade-tolerant species had a lower WD for dominant trees than the suppressed trees. However, the differences in WD between dominant and suppressed trees were not significant. Taken together, the results suggest that classifying species into pioneer and shade-tolerant groups to examine the effects of tree growth traits and social status could improve our understanding of intra- and interspecific variation in WD among subtropical tree species. [ABSTRACT FROM AUTHOR]

Coarse root biomass (CRB) is an important store of carbon (C) and forest residue for renewable energy, but is often overlooked due to the lack of a simple and effective way to estimate its magnitude. In this study, we developed allometric equations for three functional groups using data from 133 tree samples, with a diameter at breast height (DBH) ranging from 2.6 to 52.0 cm. The functional groups included evergreen coniferous ( Pinus massoniana), deciduous broad-leaved ( Alniphyllum fortunei, Choerospondias axillaris, Liquidambar formosana and Quercus fabri) and evergreen broad-leaved ( Castanopsis carlesii, Cyclobalanopsis glauca, Litsea coreana and Schima superba) species. Allometric equations that related CRB to plot inventory data (e.g. DBH or tree height (H)) and their combinations significantly fitted ( P < 0.0001) for the functional groups and all tree species. The equations using DBH or DBH-H as predictor variables were the best fit ( R ≥ 0.90) and produced good predictions with little bias (less than 21%) for local sites and at regional scales. Allometric equations related to easily obtained remote sensing data (i.e. crown width (CW) and H) were also significantly fitted ( P < 0.0001, R ≥ 0.76), and predictions were close to the observed CRB, despite a high bias (larger than 98.0%). In conclusion, the use of these equations to estimate CRB is essential to the harvest process and helps to formulate new policies for managing the feedstock supply to bioenergy production in subtropical forests. [ABSTRACT FROM AUTHOR]

Aims: Our study aimed to determine whether, and to what extent, stand characteristics and topography affected spatial variations in soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) concentrations in subtropical forests. Methods: Soil samples were taken from a Choerospondias axillaris deciduous broadleaved forest and a Lithocarpus glaber-Cyclobalanopsis glauca evergreen broadleaved forest. Spatial variations in SOC, TN and TP concentrations and the factors affecting them were investigated using geostatistical analysis and stepwise linear regression, respectively. Results: The L. glaber-C. glauca forest exhibited higher coefficients of variation (CVs) of SOC (35 %) and TN (34 %) concentrations than the C. axillaris forest (27 % for SOC and 21 % for TN), but the CV of TP concentration in the L. glaber-C. glauca forest (17 %) was lower than that in the C. axillaris forest (24 %). Stand characteristics contributed the most to spatial variations in SOC and TP, while soil texture made the greatest contribution to variations in TN. Topography contributed the least to variations in SOC, TN and TP. Conclusions: Stand characteristics, together with topography and soil texture, contributed to spatial variations in SOC, TN and TP concentrations. The contributions of stand characteristics differed in SOC, TN and TP due to their different cycling characteristics. [ABSTRACT FROM AUTHOR]

• Contents of soil total nitrogen (N) and N forms increased with vegetation restoration. • The availability of soil N decreased as vegetation restoration proceeded. • Soil N cycle was still closed when forests restored to climax communities. • Soil N availability was co-regulated by plant diversity index and soil available N pools. Nitrogen (N) is an essential element for the functioning of terrestrial ecosystems and is often the primary limiting resource for the productivity of many terrestrial ecosystems. Existing knowledge on the effect of vegetation restoration on soil N dynamics is inconsistent. The aim of this study was to investigate the dynamics of soil N contents and availability with vegetation restoration and other influencing factors. Soil samples were collected to a depth of 40 cm from four distinct plant communities along a restoration gradient from scrub-grassland (4–5 years), shrub (10–12 years), coniferous and broadleaved mixed forest (45–46 years) to the evergreen broadleaved forest (>90 years). Total N (TN), soluble organic N (SON), microbial biomass N (MBN), inorganic N (IN, including ammonium (NH 4 +), nitrate (NO 3 –)), IN/SON, NO 3 –/NH 4 +, and MBN/IN were compared across vegetation factors, soil physicochemical properties and microbial activities. TN, SON, MBN, and NH 4 + contents increased remarkably with vegetation restoration, while NO 3 – decreased from scrub-grassland to shrub and then increased. The dominant influencing factors of soil N forms were fine root biomass, soil organic carbon, C/N ratio, pH, microbial biomass carbon, and ureases, which indicated that vegetation factors, soil physicochemical properties, and microbial activities collectively control soil N accumulation. IN/SON and NO 3 –/NH 4 + ratios were < 1 and decreased with vegetation restoration, while the MBN/IN ratio increased. The results implied that soil N availability reduced with vegetation restoration and N cycling remained closed, although it has been restored to the broadleaved forest stage. The close correlation between plant diversity index and soil N availability indicated that soil N availability reduces largely due to increasing plant N demands induced by the improvement in plant species diversity. Therefore, vegetation restoration facilitates long-term soil N accumulation and retention in this region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tree mycorrhizal associations drive soil N cycling pattern in subtropical forests. • Soil nitrate N decreased with increasing ectomycorrhizal (ECM) tree dominance. • ECM tree and associated fungi reduce soil N mineralization and nitrification rates. • High NAGase activity and C:N ratio but low pH was found in ECM-dominated soils. Trees and their associated arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) fungi drive carbon (C) and nitrogen (N) cycling patterns. However, the mechanisms underpinning this relationship and the degree to which mycorrhiza mediate the effects of forest tree composition on soil N cycling outside of the temperate zone remain unclear. Here, we conducted field surveys to establish a natural gradient with increasing ECM tree dominance in subtropical forests, and explored the effects of tree mycorrhizal associations on soil N cycling. Across this mycorrhizal gradient, we quantified soil available N, microbial biomass N, net N transformation rates, as well as N -acquiring enzyme activities, litterfall biomass and quality, and soil pH during the one-year growing season. We found that with increasing ECM tree dominance, the dissolved organic N and nitrate N decreased, while the microbial biomass N increased linearly. Soils dominated by AM trees had 1.8–2.3 times larger mineral N contents, net N mineralization rate, and net nitrification rate than ECM-dominated stands, suggesting a rapid N cycling in AM-dominated stands. ECM trees and their associated fungi reduce the net N mineralization rate in topsoil mainly by producing recalcitrant litterfall (i.e., higher C:N) and by secreting β- N -acetylglucosaminidase to deplete N directly from soil organic matter, which together increased N limitation for free-living decomposers. The low pH and high C:N ratio in ECM-dominated soils inhibit the proliferation of ammonia-oxidizers and thus decrease the net nitrification rate. Our results demonstrate that the increasing ECM tree dominance increase soil N -acquiring enzyme activity and C:N ratio but decrease pH value, all of them critically mediating soil N availability. Consequently, by altering the relative abundances of tree mycorrhizal associations shifts in forest composition under global changes and plantation establishment can be expected to result in altered soil N cycling. [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]

Fine root production accounts for a large proportion of net primary production (NPP) in forest ecosystems that is highly responsive to environmental and biotic changes. The underlying mechanisms of the relationship between tree species richness and fine root production have not been fully examined. Here we hypothesized that: (i) the relationship between aboveground species richness and fine root production could be attributable to belowground spatial resource partitioning; (ii) either symmetrical or asymmetrical root proliferation to obtain nutrients leads to increased fine root production; and (iii) stand density affects the relationship between species richness and fine root production. We used an ingrowth core method to estimate fine root production coupled to molecular approaches for identifying the tree species of sampled fine roots within each ingrowth core. There was a significant and positive relationship between aboveground species richness and fine root production. The increase in fine root production might partially be attributed to asymmetrical root proliferation rather than belowground spatial resource partitioning. A piecewise structural equation model (SEM) linking stand density and soil nutrients revealed that both factors play dominant roles in mediating the effects of aboveground species richness on fine root production. Moreover, fine root production and relative abundance of fine root distribution within-layers both depended on the effects of aboveground species richness × stand density × soil phosphorus (P) interactions. Therefore, soil P concentration and stand density partially explained the positive aboveground species richness–fine root production relationship. Unlabelled Image • Fine root production was positively related to tree species richness. • Causes of the positive relationship were determined by piecewise structure equation modeling. • Stand density and asymmetric foraging for soil nutrients were the main explanations. • Our results support the stress-gradient hypothesis. • Phosphorus limitation and high stand density favored belowground complementary effect. [ABSTRACT FROM AUTHOR]