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An unresolved question of temperate forests is how pioneer tree species persist in mature forests. In order to understand the responsible mechanisms, we investigated a near‐climax mixed temperate forest dominated by Betula albosinensis in the Qinling Mountains of China. Through establishing four 50 m × 50 m plots, we examined the canopy disturbance characteristics and its effects on tree recruitments. We further test the intra‐ and interspecific effects on the recruitment of B. albosinensis. The obtained data demonstrated canopy disturbance was frequent but most small‐sized. The canopy gaps are caused mainly by adult B. albosinensis by snapping. The regeneration of coexistent tree species shows a distinct preference for gap size. B. albosinensis were clumped at the juvenile stage and small scales. B. albosinensis juveniles were positively associated with B. utilis juveniles and negatively associated with the conspecific and B. utilis large trees. In addition, B. albosinensis juveniles showed negative associations with contemporary other tree species. Our results suggested that canopy disturbance caused by canopy trees and gap partitioning among the coexistent tree species are important for the persistence of the mixed forest. As a main gapmaker, B. albosinensis appear to develop a self‐perpetuating life‐history trait and allow them to persist. [ABSTRACT FROM AUTHOR]

In this research, the design of general hybrid thruster cable-driven parallel robots (TCDPRs) is studied. TCDPRs combine the actuation advantages of both cables and thrusters(rotors) in order to achieve a larger payload capacity and workspace. The additional forces provided by the thrusters can efficiently increase the available wrench set (AWS), and hence the wrench-feasible workspace (WFW), compared with pure CDPRs. The focus of this work is to study the arrangement of thrusters such that the TCDPR can produce the desired wrench set over a required workspace. The arrangement refers the number, attachment locations, directions and maximum force of the thrusters. By comparing the WFW of both planar and spatial CDPRs with TCDPRs designed using the proposed methods, it is shown that the AWS and hence the WFW can be increased to meet the requirements. Furthermore, the contributions of the thruster force to decrease the maximum required cable forces is also shown in this work. These show that a well-designed thruster arrangement is an effective approach to increasing the CDPR capabilities. • Workspace enlargement of cable-driven parallel robots with thrusters. • The design of thrusters in generating available wrench sets of cable-driven parallel robots. • The optimization of cable forces distribution of hybrid thruster cable-driven parallel robots. [ABSTRACT FROM AUTHOR]

To contribute to a better understanding of the regeneration strategy of Betula albosinensis forests and the likely reasons behind either the successful recovery or failure after strip clearcutting, we compared the population structures and spatial patterns of B. albosinensis in eight B. albosinensis stands in Qinling Mountains, China. Four cut and four uncut stands were selected, and each sampled using a single large plot (0.25 ha). Results indicated that, on the one hand, B. albosinensis recruitment was scarce (average of 48 stems ha−1) in the uncut stands, relative to the mature population (average of 259 stems ha−1), suggesting a failure of recruitment. On the other hand, the subsequent regeneration approximately 50 years after the strip clearcutting showed that the density of the target species seedlings and saplings has increased significantly, and the current average density of seedlings and saplings was 156 stems ha−1. The clumped spatial pattern of B. albosinensis suggested that their regeneration was highly dependent on canopy disturbance. However, recruitment remained poor in the uncut stands because most gaps were small in scale. The successful regeneration of sunlight-loving B. albosinensis after strip clearcutting was attributed to the exposed land and availability of more sunlight. Bamboo density did not influence B. albosinensis recruitment in the uncut stands. However, stand regeneration was impeded after strip clearcutting; thus, removing bamboo is essential in improving the competitive status of B. albosinensis at the later stage of forest regeneration after clearcutting. The moderate severity of disturbance resulting from strip clearcutting reversed the degeneration trend of primary B. albosinensis stands. This outcome can help strike a balance between forest conservation and the demand for wood products by releasing space and exposing the forested land for recruitment. Life history traits and spatiotemporal disturbance magnitude are important factors to consider in implementing effective B. albosinensis regeneration strategies. [ABSTRACT FROM AUTHOR]

Purpose: Carbohydrate-active enzymes (CAZymes) mediate carbohydrate turnover and play vital roles in plant- and microbial-derived carbon decomposition. However, the changes of genes that encoding enzymes for plant- and microbial-derived carbon decomposition along environmental gradients remains unclear. Methods: We used metagenomic sequencing to explore changes in genes encoding enzymes for carbon decomposition in five forest sites along an elevational gradient (1503–3182 m) on Qinling Mountain, China. Results: The genes encoding CAZymes showed various patterns along the elevational gradient. In particular, the abundance of genes encoding auxiliary enzymes and glycoside hydrolases decreased with increasing elevation. The abundance of genes encoding enzymes for plant- and fungi-derived carbon decomposition was higher at low elevations than at high elevations, whereas the abundance of genes encoding enzymes for bacteria-derived carbon decomposition was higher at high elevations than at low elevations. The results indicate contrasting patterns of fungal- and bacterial-derived carbon decomposition with elevation. Proteobacteria and Acidobacteria were the dominant species that decomposed dead plant and microbial biomass. Moreover, our results reveal that soil properties (i.e., ammonium nitrogen and bulk density) and vegetation properties dominated the CAZymes gene distribution along the elevational gradient. Conclusion: Bacteria- and fungi-derived carbon decomposition potentials show contrasting elevational patterns in forest soils; soil and vegetation properties are common controls for the elevational patterns. [ABSTRACT FROM AUTHOR]

Assessing plant diversity during community succession based on plant trait and phylogenetic features within a community (alpha scale) and among communities (beta scale) could improve our understanding of community succession mechanism. However, whether changes of community functional diversity at alpha and beta scale are structured by different traits and whether integrating plant traits and phylogeny can enhance the ability in detecting diversity pattern have not been studied in detail. Thirty plots representing different successional stages were established on the Loess Plateau of China and 15 functional traits were measured for all coexisting species. We first analyzed the functional alpha and beta diversity along succession by decomposing species trait into alpha and beta components and then integrated key traits with phylogenetic information to explore their roles in shaping species turnover during community succession. We found that functional alpha diversity increased along successional stages and was structured by morphological traits, while beta diversity decreased during succession and was more structured by stoichiometry traits. Phylogenetic alpha diversity showed congruent pattern with functional alpha diversity because of phylogenetic conservation of trait alpha components (variation within community), while beta diversity showed incongruent pattern due to phylogenetic randomness of trait beta components (variation among communities). Furthermore, only integrating relatively conserved traits (plant height and seed mass) and phylogenetic information can raise the detecting ability in assessing diversity change. Overall, our results reveal the increasing niche differentiation within community and functional convergence among communities with succession process, indicating the importance of matching traits with scale in studying community functional diversity and the asymmetry of traits and phylogeny in reflecting species ecological differences under long‐term selection pressures. [ABSTRACT FROM AUTHOR]

Soil net nitrogen (N) mineralisation, the difference between organic nitrogen mineralisation and mineral nitrogen immobilisation, changes with elevation, thereby determining plant productivity and soil N cycling along elevation gradients. However, it has yet to be established how different microbial functional genes influence the rate of soil net N mineralisation along such gradients. To address this deficiency in our current knowledge, we performed metagenomic sequencing to identify soil microbial functional genes encoding enzymes involved in N cycling at five forest sites along an elevational gradient spanning a range from 1503 to 3182 m above sea level. Our results indicate that the rate of net N mineralisation follows a unimodal pattern with increasing elevation, with a peak (0.18 mg kg−1 d−1) being detected at the mid‐high elevation site. Further, we detected a significant correlation between the abundance of genes encoding enzymes involved in denitrification and ammonia assimilation pathways and net N mineralisation rate (p < 0.05). Moreover, we established that microbial species in the phyla Cyanobacteria, Acidobacteria and Planctomycetes, harbouring keystone functional genes, play a predominant role in determining the rate of net N mineralisation. Our findings also revealed soil substrate content (ammonium nitrogen and nitrite nitrogen, soil organic carbon, and C:N ratio) and soil environment (soil temperature and soil moisture) to be the major drivers of net N mineralisation in soil via their regulatory effects on the composition of microbial communities and functional genes. Our characterisation of the microbial metagenomic basis of net N mineralisation in forest soils accordingly highlights the importance of the combined contributions of soil microbial functional genes, soil substrate, and environmental factors in determining the cycling of N in forest soils at different elevations. Highlights: Net N mineralisation rate followed a unimodal pattern along an elevational gradient.Denitrification and ammonia assimilation genes were correlated with net N mineralisation rate.Cyanobacteria play a dominant role in determining net N mineralisation rate.Soil substrate and environment determine microbial functional gene distribution. [ABSTRACT FROM AUTHOR]

Soil priming is a microbial‐driven process, which determines key soil–climate feedbacks in response to fresh carbon inputs. Despite its importance, the microbial traits behind this process are largely undetermined. Knowledge of the role of these traits is integral to advance our understanding of how soil microbes regulate carbon (C) emissions in forests, which support the largest soil carbon stocks globally. Using metagenomic sequencing and 13C‐glucose, we provide unprecedented evidence that microbial traits explain a unique portion of the variation in soil priming across forest biomes from tropical to cold temperature regions. We show that microbial functional profiles associated with the degradation of labile C, especially rapid simple sugar metabolism, drive soil priming in different forests. Genes involved in the degradation of lignin and aromatic compounds were negatively associated with priming effects in temperate forests, whereas the highest level of soil priming was associated with β‐glucosidase genes in tropical/subtropical forests. Moreover, we reconstructed, for the first time, 42 whole bacterial genomes associated with the soil priming effect and found that these organisms support important gene machinery involved in priming effect. Collectively, our work demonstrates the importance of microbial traits to explain soil priming across forest biomes and suggests that rapid carbon metabolism is responsible for priming effects in forests. This knowledge is important because it advances our understanding on the microbial mechanisms mediating soil–climate feedbacks at a continental scale. [ABSTRACT FROM AUTHOR]

Microbial nitrogen transformation processes in grasslands are important nitrous oxide (N 2 O) sources on the Tibetan Plateau. Different microorganisms carrying various functional nitrogen (N) cycling genes colonize different soil types and have varying impacts on N 2 O emissions. However, the role of specific microbial components such as unique and shared microbial species, in N 2 O flux in alpine grassland soils remains understudied. Thus, we combined gas chromatography-based static opaque chamber methods with metagenomic sequencing to investigate the role of unique and shared microbial species carrying N-cycling genes in N 2 O emissions from two alpine grassland types on the Tibetan Plateau. Our results showed that the N 2 O flux in the alpine meadows (9.48 × 10−9 g m−2 h−1) was higher than that in the alpine steppes (4.21 × 10−9 g m−2 h−1). Furthermore, our study revealed a significant negative correlation between the abundance of unique microbial species and the N 2 O flux in alpine steppes. In contrast, the abundance of shared microbial species was significantly and positively correlated with N 2 O flux. The unique microbial species in the phyla Chloroflexi and Actinobacteria carried the ureC , nasA and nirB genes, which could consume nitrogen substrates in forms other than producing N 2 O, which could explain the N 2 O reduction seen in the alpine steppes. In addition, the higher abundance of shared microbial species in the phyla Proteobacteria , Actinobacteria , Thaumarchaeota and Acidobacteria carried genes encoding denitrification pathways (nirK , narG , and norB) could interpret the higher N 2 O emissions in the alpine meadows. In addition, our study revealed that the soil substrate contents (e.g., soil organic carbon and total nitrogen) and soil environment factors (e.g., soil pH and soil moisture) were potentially important drivers of N 2 O emissions in soil via their regulation of the composition of unique and shared microbial communities carrying N-cycling genes. Collectively, our results suggested that identifying the unique and shared microbial species carrying different N-cycling genes could provide potential biological strategies for mitigating N 2 O emissions in alpine grasslands, such as blocking the growth of shared microbial species. Future management practices for mitigating N 2 O emissions in alpine grassland should also focus on adopting appropriate nutrient management strategies, such as balanced fertilization, to prevent excessive nutrient. Our findings provide insights for further elucidating the different potential regulatory effects of unique and shared microbial species on emissions under the control of the soil environment in different types of grasslands on the Tibetan Plateau. • Unique species in alpine steppe suppressed the N 2 O emissions. • Shared species in alpine meadow promoted the N 2 O emissions. • Soil physicochemical factors influenced N 2 O emissions through affecting on microbial growth. [ABSTRACT FROM AUTHOR]

Questions: Interspecific differences in plant biomass allocation reflect plant nutrient use strategy, determining species fitness under different environmental conditions. However, plant biomass allocation may be affected by both habitat and plant traits. We asked how environmental conditions and plant traits jointly affect shrub biomass allocation. Specifically, how they further play roles in understanding community species composition as ecoregion changes. Location: Shaanxi province, North China. Methods: Plant biomass, plant traits and community composition were surveyed for 48 shrub sites distributed in five ecoregions. Species‐specific allocation parameters (allometric constants and scaling exponents) and plant traits were weighted with species abundance to calculate the community biomass allocation and community traits. Linear mixed models were used to assess relative contributions of plant traits and environmental factors in explaining biomass allocation pattern. Their roles in explaining species composition were analyzed by canonical correspondence analysis (CCA). Results: We reported that shrub biomass allocation parameters of stems vs leaves and roots vs shoots varied significantly among ecoregions. Plant traits explained more variation in stem vs leaf biomass allocation than soil and climate factors, while climate factors played important roles in variation of root vs shoot biomass allocation. Combined with plant traits and environmental conditions, biomass allocation showed a synergistic role in explaining community species composition. Conclusions: Environment and plant traits explain different aspects of shrub biomass allocation, and species‐specific biomass allocation strategy have the potential to predict community species composition and distribution across ecoregions. Our study sheds light on the biomass allocations significance in understanding species turnover and community distribution. [ABSTRACT FROM AUTHOR]

• Microbial diversity and enzyme activity varied significantly with elevation. • Climatic factors explained variation in microbial diversity and enzyme dynamics. • Temperature enhance the microbial interaction between root and soil. The distribution patterns of the microbial community and enzyme activity in soil systems along an elevation gradient have attracted considerable attention; however, the differences in microbial diversity and enzyme activity between the rhizosphere and bulk soil and their drivers are still unclear. Here, we used an elevation gradient that covered six elevation levels and ranged from 1308 to 2600 m above sea level. Illumina MiSeq sequencing of the 16S rRNA gene and ITS-1 gene was used to analyze the community of bacteria, total fungi, ectomycorrhizal (EcM) fungi, and saprotrophic fungi in both rhizosphere and bulk soil; in addition, the soil enzyme activity (β-glucosidase, N -acetyl-glucosaminidase, leucine aminopeptidase, and acid phosphatase) was investigated. The results revealed that the elevation significantly affected the diversity of the bacterial, total fungal, EcM, and saprotrophic fungal community, as well as the enzyme activity dynamics. The difference in the microbial diversity and enzyme activity between rhizosphere and bulk soil diminished as the elevation increased, except for the saprotrophic fungal diversity. Similarly, the dominant phyla from the compositions of bacteria, fungi, EcM fungi, and saprotrophic fungi, such as Proteobacteria , Acidobacteria , Actinobacteria , Basidiomycota , and Ascomycota , also changed with elevation and rhizosphere. In addition, the elevation-dependent differences in the microbial community and enzyme activity between the rhizosphere and bulk soil were affected mainly by climatic factors (mean annual temperature and precipitation) and soil properties, such as the bulk density, ammonium nitrogen, and total phosphorus. The effects of the climatic factors were greater than those of the soil properties along the elevation gradient. These results suggest that changes in climatic factors, such as temperature, with elevation may affect the microbial interaction between roots and the soil. The result highlight the importance of the ecological roles of the microbial community in climate change. [ABSTRACT FROM AUTHOR]

Community assembly processes is the primary focus of community ecology. Using phylogenetic-based and functional trait-based methods jointly to explore these processes along environmental gradients are useful ways to explain the change of assembly mechanisms under changing world. Our study combined these methods to test assembly processes in wide range gradients of elevation and other habitat environmental factors. We collected our data at 40 plots in Taibai Mountain, China, with more than 2,300 m altitude difference in study area and then measured traits and environmental factors. Variance partitioning was used to distinguish the main environment factors leading to phylogeny and traits change among 40 plots. Principal component analysis ( PCA) was applied to colligate other environment factors. Community assembly patterns along environmental gradients based on phylogenetic and functional methods were studied for exploring assembly mechanisms. Phylogenetic signal was calculated for each community along environmental gradients in order to detect the variation of trait performance on phylogeny. Elevation showed a better explanatory power than other environment factors for phylogenetic and most traits' variance. Phylogenetic and several functional structure clustered at high elevation while some conserved traits overdispersed. Convergent tendency which might be caused by filtering or competition along elevation was detected based on functional traits. Leaf dry matter content ( LDMC) and leaf nitrogen content along PCA 1 axis showed conflicting patterns comparing to patterns showed on elevation. LDMC exhibited the strongest phylogenetic signal. Only the phylogenetic signal of maximum plant height showed explicable change along environmental gradients. Synthesis. Elevation is the best environment factors for predicting phylogeny and traits change. Plant's phylogenetic and some functional structures show environmental filtering in alpine region while it shows different assembly processes in middle- and low-altitude region by different trait/phylogeny. The results highlight deterministic processes dominate community assembly in large-scale environmental gradients. Performance of phylogeny and traits along gradients may be independent with each other. The novel method for calculating functional structure which we used in this study and the focus of phylogenetic signal change along gradients may provide more useful ways to detect community assembly mechanisms. [ABSTRACT FROM AUTHOR]

• Ligninase-to-cellulase ratio increased from temperate to tropical forest ecosystems. • Soil substrates and fungal abundance drive of ligninase-to-cellulase ratio. • Microbes utilize recalcitrant C pools stronger in tropical forests. Soil enzymes are the most potent bioactive components in forest ecosystems. Cellulases and ligninases are vital carbon (C)-degrading enzymes that target different C pools. The ratio of ligninase-to-cellulase activity is good indicator for microbial soil C preference, play an important role in soil C cycling. However, our understanding of enzyme ratios and their drivers across forest ecosystems remains unclear. In this study, we hypothesized that (i) the ligninase-to-cellulase ratio increased from temperate forests to tropical forest ecosystems, and (ii) the dominant factors would be microbial abundances. About 2–3 kg of topsoil (0–10 cm) from each of the ten forest ecosystems were collected across a 3425 km gradient in China between July and August 2019. We analyzed the biogeographic patterns of ligninase and cellulase activities and the ratio of ligninase-to-cellulase activities to determine how this ratio responded to climatic factors, soil properties and substrates, and microbial abundances across the forest ecosystems along the latitudinal gradient. Our findings showed that the average soil ligninase activity was 3.49 nmol h−1 g−1, whereas the average soil cellulase activity was 525.26 nmol h−1 g−1 across the forest ecosystems sampled. The average activity ratio of ligninase-to-cellulase in tropical forest ecosystems was 27.9% higher than that in subtropical forests and 64.2% higher than that in temperate forest ecosystems. The partial least squares path model demonstrated that the ligninase-to-cellulase activity ratio was significantly negatively correlated with soil substrates (r = -0.94, p < 0.001) and significantly positively correlated with microbial abundances (r = 0.38, p < 0.01). The variation partitioning analysis further revealed that soil substrates explained 19.4% variation regarding ligninase-to-cellulase ratio, whereas microbial abundance (fungal abundance) contributed 2.8%. This study provides crucial information about the distribution of enzyme ratios along the latitude gradient, highlights the microbial utilization of recalcitrant C pools in tropical forests, and provides an insight into the response of the global C cycle under a changing climate. [ABSTRACT FROM AUTHOR]

• N limitation for microbe increased with increasing elevation. • The rates of SOC decomposition and microbial respiration decreased with elevation. • Global warming relieve microbial N limitation and lead to increased soil carbon release. • DOC:TDN explained more variation for microbial N limitation and microbial processes. Soil microbes have a great influence on the feedbacks of carbon (C)-climate, and their metabolic activities are limited by resource availability. Altitudinal gradients strongly affect soil microbial communities, but the effects on microbial resource limitation and their regulation for C dynamics remain unclear. In this study, we designed an altitudinal gradient experiment that included six altitudinal sites from 1308 m to 2600 m in the Qinling Mountains, China. The enzymatic stoichiometry was determined and modeled to investigate microbial resource limitations and major microbial metabolism processes (e.g., organic C decomposition rate and microbial respiration rate) along the elevation gradient. Other environmental variables including mean annual temperature (MAT) and mean annual precipitation (MAP), the C: nitrogen (N): phosphorus (P) ratio in soil total nutrients, available nutrients, and microbial biomass were also measured. The results showed that soil microbes suffered from N limitation in our study and microbial N limitation significantly increased with increasing elevation. But the rates of both organic C decomposition and microbial respiration greatly decreased with increased elevation. These trends suggest that warming induced by elevation change might relieve N limitation for microbes and lead to increased soil C release. Redundancy analysis (RDA) showed that MAT and soil nutrient stoichiometry, particularly for the DOC: TDN ratio, explained more variations for changes in microbial N limitation and major microbial processes. Collectively, our study demonstrated that the higher microbial N limitation at high elevation may be beneficial to soil carbon accumulation by changing the C: N ratio, which provided insights into microbially mediated soil carbon release under global warming. [ABSTRACT FROM AUTHOR]

• N limitation for microbe increased with increasing elevation. • The rates of SOC decomposition and microbial respiration decreased with elevation. • Global warming relieve microbial N limitation and lead to increased soil carbon release. • DOC:TDN explained more variation for microbial N limitation and microbial processes. Soil microbes have a great influence on the feedbacks of carbon (C)-climate, and their metabolic activities are limited by resource availability. Altitudinal gradients strongly affect soil microbial communities, but the effects on microbial resource limitation and their regulation for C dynamics remain unclear. In this study, we designed an altitudinal gradient experiment that included six altitudinal sites from 1308 m to 2600 m in the Qinling Mountains, China. The enzymatic stoichiometry was determined and modeled to investigate microbial resource limitations and major microbial metabolism processes (e.g., organic C decomposition rate and microbial respiration rate) along the elevation gradient. Other environmental variables including mean annual temperature (MAT) and mean annual precipitation (MAP), the C: nitrogen (N): phosphorus (P) ratio in soil total nutrients, available nutrients, and microbial biomass were also measured. The results showed that soil microbes suffered from N limitation in our study and microbial N limitation significantly increased with increasing elevation. But the rates of both organic C decomposition and microbial respiration greatly decreased with increased elevation. These trends suggest that warming induced by elevation change might relieve N limitation for microbes and lead to increased soil C release. Redundancy analysis (RDA) showed that MAT and soil nutrient stoichiometry, particularly for the DOC: TDN ratio, explained more variations for changes in microbial N limitation and major microbial processes. Collectively, our study demonstrated that the higher microbial N limitation at high elevation may be beneficial to soil carbon accumulation by changing the C: N ratio, which provided insights into microbially mediated soil carbon release under global warming. [ABSTRACT FROM AUTHOR]

[Display omitted] • Elevation is the most important regional-scale predictor of phylogenetic distance. • Resource availability shapes community assembly and diversity at the regional level. • Local and regional patterns of diversity are different because of shift in assembly. • It is vital to establish a complex gradient to dissect assembly mechanism. Diversity and its maintaining mechanism (community assembly) shift along resource availability gradients at local and regional levels. It is necessary to identify key natural factors shaping community assembly or diversity patterns, so that understanding the patterns of diversity and assembly along these factors across local to regional scales. In this study, we investigated the six local sites of plant community in Qinling Mountains region. Based on the relative importance of environmental factors in shaping the phylogenetic diversity, a complex resource availability gradient was established to assess taxonomic and phylogenetic diversity and assembly patterns along it at local or regional scale separately. Phylogenetic analyses and the biodiversity index were estimated along environmental gradients as well, to assess the difference between change tendencies along natural environmental and resource availability gradients. We found that 1) elevation was the most important regional-scale environmental predictor of phylogeny of community; 2) taxonomic and phylogenetic diversity studies showed similar patterns along both resource and elevational gradients at regional scale, and that diversity at local scale may differ regardless of gradients; 3) at the regional level, phylogenetic structures revealed convergent tendencies along the elevational gradient across different species pools. Phylogenetic assembly patterns along the elevation gradient at the local scale differed from the patterns at the regional scale, with consistent clustering tending to overspread along the resource availability gradient. In conclusion, resource availability shaped community assembly at the regional level. Local patterns of diversity influenced regional patterns differently because of variation in the colonization history or assembly process. Owing to varying assembly patterns along simple environmental gradients, it is vital to establish a complex resource availability gradient to dissect the real assembly mechanism or biodiversity patterns operating in local to regional-scale processes. These findings may provide valuable reference about forest restoration and management. [ABSTRACT FROM AUTHOR]

Afforestation can modify terrestrial carbon (C) pools, some of which are primarily fixed in the plant dead biomass and then incorporated into the microbial dead biomass. Soil microorganisms exert a critical role in C flow and potentially influence C balance through the degradation of plant and microbial dead biomass. Here, we compared sites along a 45-year Robinia pseudoacacia (RP) afforestation chronosequence on the Loess Plateau of China. Subsequently, the trends of microbial carbohydrate-active enzymes (CAZyme) and their responses to the decomposition of dead biomass of different origins were studied using metagenomics. The results show that soil microbial CAZyme families, which degrade the plant- and microbial-derived components, significantly increased after afforestation, with a significant peak at the 20-year site. The dominant bacterial phyla (i.e., Actinobacteria , Proteobacteria , and Acidobacteria) mineralized C sources from plant and microbial biomass components through their corresponding CAZyme families. Moreover, the increased abundance of CAZymes involved in the decomposition of plant-derived components (e.g., cellulose, hemicellulose, and lignin) contributed to the formation of C pools. In the case of microbial-derived components, the abundance of CAZymes encoding the bacterial-derived components (peptidoglycan) was larger than that encoding fungal-derived components (chitin and glucans) and was more associated with microbial metabolic activity (qCO 2 and Cmic: Corg ratio), indicating a higher investment of bacterial-derived components for microbial carbon turnover following afforestation. Overall, our study compares plant- and microbial-derived biomass to illustrate the differential contributions of dead biomass to C accumulation and confirms the importance of the bacterial community and derived biomass for C turnover following afforestation. • Microbial CAZymes increase after afforestation, peaking at 20-year site. • Dominant bacterial phyla encode more CAZymes that degrade plant and microbial biomass. • The CAZymes encoding bacterial biomass are higher than that encoding fungal biomass. • Bacterial biomass decomposition is more associated with microbial metabolic activity. [ABSTRACT FROM AUTHOR]

Trait-based approaches present a promising avenue for improving our understanding of species coexistence and community assembly, while intraspecific trait variation (ITV) across different spatial scales is important in trait-based community assembly mechanisms, especially in extreme environments. In this study, we focused on the functional diversity and community assembly patterns of a desert community across different spatial scales and investigated whether ITV plays a significant role in community assembly processes in arid habitats. A 50 m × 50 m plot with different small quadrats was established in a typical desert community at the transition zone between the Tengger Desert and Loess Plateau in China. A total of 14 traits were selected to assess the trait-based functional diversity and assembly processes in the community. We found that functional diversity showed different patterns when considering ITV and related to different types of traits (chemical traits or morphological traits) and some soil factors (pH and nitrate nitrogen). Plant communities in this study showed stochastic distribution patterns and similar functional diversity patterns based on functional trait approaches, regardless of spatial scales. Also, the effect of ITV on community assembly did not show more effect with increasing scales. These results indicated that ITV diluted deterministic processes in community assembly across scales in arid habitats. [ABSTRACT FROM AUTHOR]