Ecological stoichiometry is a science that studies the interaction relationships of chemical elements in ecological components.By studying the nutrient element content and ecological indicator ratios in the"soil-litter-leaf"system,this study aims to analyze the correlation between nutrient elements and reveal the nutrient status of ecosystems,as well as the coupling process,balance mechanisms,and their impact on plant community structure and function. The study area is located in the Lijiang River Basin in Guilin,Guangxi.The basin has a subtropical humid monsoon climate and consists of a non-karst area upstream and a karst/non-karst mixture plain landform downstream.Nine representative sample plots were selected along the Lijiang River Basin,categorized into limestone soil(dominated by limestone/dolomite)and acidic red soil(derived from granite),with subgroups of natural forests(e.g.,evergreen broad-leaved)and plantations(e.g.,eucalyptus,bamboo).Soil,litterfall,and leaf samples were collected in autumn,spring,and summer of 2017 and 2018,respectively.The samples were analyzed for Total Organic Carbon(TOC),total nitrogen(N),total phosphorus(P),potassium(K),calcium(Ca),sodium(Na),and magnesium(Mg)as well as soil ammonium(NH4+),nitrate(NO3-)and Available P(AP).The biological absorption coefficient was calculated to reflect the ability of plants absorbing and accumulating chemical elements from the environment. The results showed that soil pH varied between 3.77 and 7.57,with significantly higher pH values in limestone soils compared to acidic red soils.There were no significant differences in soil C and N content between limestone and acidic red soils,but they varied significantly among different altitudes,showing low-altitude soils had lower C and N content compared to high-altitude soils,and plantations had lower soil C and N content compared to natural forests.Soil P content ranged from 0.39 g·kg-1 to 2.50 g·kg-1,with higher P content in acidic red soils compared to limestone soils.The C:N ratio in soils was below 25,indicating nitrogen saturation and the risk for N leaching,especially for the limestone soil.High-altitude soils had higher C:P and N:P ratios compared to low-altitude soils.Litterfall element content and stoichiometric ratios showed smaller differences among different soils and forest types.Litterfall C and N content were slightly higher in natural forests compared to plantations.Litterfall P content ranged from 0.94 g·kg-1 to 2.62 g·kg-1.The average C/N of litterfall for limestone soil and acidic red soil were 20.0 and 17.8,respectively,consistently below the 25 threshold,indicating rapid decomposition.Leaves had the highest C,N,P and Ca content compared to soil and litterfall.The N:P＞16 in leaves(common in both forest types)suggested P limitation,particularly in forests under acidic red soil.Except for K,the biological absorption coefficient of leaves was above 1 and varied among different elements and forest types,with higher absorption coefficients observed in natural forests for K and Mg,lower for Na.The plants under acidic red soil had higher biological absorption coefficient for Ca compared to those under the limestone soil.Soil C,N,P,C:P,and N:P ratios,as well as litterfall K and Ca,played a central role in the element coupling relationship.Plantation and natural forests under limestone soil had similar soil element stoichiometric characteristics,mainly influenced by pH,Ca,and Na.Plantations under acidic red soil were mainly influenced by K and Mg,while natural forests were influenced by C,N,C:P,and N:P ratios.Soil elements had closer coupling relationships with litterfall elements compared to soil and leaf elements.In plantations under acidic red soil,P-related indicators(P,C/P,N/P and AP)and Ca played a key role in element coupling.Significant positive correlations were observed between litterfall K and soil pH,P,Ca,and between litterfall Mg and soil Ca.In natural forests under acidic red soil,litterfall Mg showed stronger coupling relationships with soil factors. This study revealed the soil-litter-leaf element stoichiometric characteristics and coupling relationships in different forest types in the Lijiang River Basin.The study identifies potential N loss and P limitation issues in the basin and suggests that integrating natural forest restoration could enhance ecosystem resilience by improving nutrient retention and reducing erosion risks.It provides scientific guidance for ecological conservation and restoration efforts.

In species-rich forests, the integration of vegetative and reproductive traits defines plant ecological strategies and underpins community assembly. How these trait syndromes assemble into functional groups to facilitate species coexistence in ecotones remains unclear. To address this, we measured 17 key functional traits in 121 woody plant species, covering vegetative and reproductive traits, and used hierarchical clustering to classify these species into functional groups (FGs). We found the following: (1) The woody plant community exhibits distinct trait syndromes adapted to the ecotonal environment: evergreen species accounted for 84.3%, microphanerophytes dominated (95.04%), simple leaves and alternate phyllotaxy prevailed, and animal-mediated pollination (91.74%) and seed dispersal (77.69%) were the primary reproductive strategies. (2) The 121 species were classified into 10 optimal FGs based on integrated differences in vegetative traits (e.g., leaf morphology, life form, phyllotaxy) and reproductive traits (e.g., pollination/dispersal mode, inflorescence/fruit type). Most FGs were dominated by evergreen microphanerophytes, reflecting convergent adaptation to the subtropical ecotonal environment, while distinct adaptive strategies differentiated the groups: FG1 (solely Meliosma rigida) was distinguished by whorled phyllotaxy and large leaves, a specialization for high-light microhabitats; FG5, a unique deciduous group, comprised species (e.g., Nyssa sinensis) with alternate leaves and axillary inflorescences, adapting to seasonal resource fluctuations. (3) These FGs reflected adaptive strategies to diverse microhabitats: rare species in FG4 (e.g., Acer cordatum) adopted wind-dependent pollination/dispersal to cope with mountainous wind variability, while FGs 3, 7, 8, 10 relied on animal mutualism to ensure reproductive success, highlighting the role of plant-animal interactions in community structure. Our study clarifies the trait differentiation patterns and FG assembly mechanisms of woody plants in the mid-subtropical-south-subtropical ecotone. The integrated trait-based FG classification could provide insights into how species coexist via niche differentiation and offer a theoretical basis for biodiversity and ecosystem conservation.

To reveal the differences in soil microbial nutrient limitation and nutrient availability at the aggregate scale of soil types in a subtropical forest in China,the O/A horizon(0-3 cm and 0-7 cm,respectively)and AB horizon(below O/A horizon to 20 cm depth)of typical acidic red soil and neutral limestone soil in Northern Guangxi were studied.The activities of carbon-acquiring enzymes(sucrase,amylase,β-1,4-glucosidase(BG)),nitrogen-acquiring enzymes(urease,β-1,4-N-acetyl-glucosaminidase(NAG),leucine amino peptidase(LAP)),and phosphorus-acquiring enzymes(phytase and acid phosphatase(AP))in different aggregate sizes were determined to reveal the variation in soil enzyme stoichiometry characteristics.The results showed that the limestone soil had higher nitrogen-acquiring enzyme activity compared to that in the red soil,with urease,NAG,and LAP activities being 38.84%,123.89%,and 4.06%higher,respectively.The differences in carbon-and phosphorus-acquiring enzyme activities between the two soils were not significant.The overall soil enzyme activities in the O/A horizon were higher than in the AB horizon for both red soil and limestone soil.Soil total organic carbon and pH were identified as key factors influencing soil enzyme activities.Most enzyme activities(BG,urease,NAG,and phytase)were higher in micro-aggregates(0.1-0.25 mm and<0.1 mm),emphasizing the role of micro-aggregates in promoting organic matter decomposition and accelerating soil nutrient cycling.Compared to those in red soil,limestone soil exhibited greater differences in NAG and phytase activities among aggregates.The mean values of ln(BG)∶ln(NAG+LAP)∶ln(AP)of red soil and limestone soil as well as their aggregates were 1.02∶1∶1.04 and 0.95∶1∶0.93,respectively,generally conforming to the global average ratio of 1∶1∶1.The ln(BG)∶ln(NAG+LAP)and vector lengths were higher in red soil than in limestone soil,indicating stronger carbon limitation in the red soil.The ln(NAG+LAP)∶ln(AP)ratio was lower in red soil than in limestone soil,with the former having a larger vector angle,suggesting stronger phosphorus limitation.Soil pH and total phosphorus were identified as the primary influencing factors of enzyme activity stoichiometry characteristics,suggesting that the bioavailability of organic matter and phosphorus in acidic soil was lower than in limestone soil,prompting microbes to secrete carbon and phosphorus enzymes to enhance acquisition efficiency.The high pH of limestone soil may lead to nitrogen limitation due to nitrate leaching caused by higher mineralization and nitrification rates.Microbes in the large aggregates(1-2 mm and 0.5-1 mm)of both soils experienced stronger phosphorus limitation,whereas carbon limitation was stronger in micro-aggregates,especially in the 0.1-0.25 mm aggregates.The microbial nutrient pattern in limestone soil aggregates shifted from phosphorus limitation to nitrogen limitation from large to micro-aggregates.This study reveals the influence of soil type and aggregate on the soil microbial nutrient limitation patterns of soil microbial elements in subtropical forest soils of China.

Variations in plant traits are indicative of plant adaptations to forest environments, and studying their relationships with tree growth provides valuable insights into forest regeneration. The spatial arrangement of plant seeds within the forest litter or soil critically influences the variations of root-leaf traits, thereby affecting the adaptive strategies of emerging seedlings. However, our current understanding of the impacts of individual root-leaf traits on seedling growth in different relative position, and whether these traits together affect growth, remains limited. This study focuses on the dominant tree species, Castanopsis kawakamii, within the Sanming C. kawakamii Nature Reserve of China. The present experiment aimed to examine the variations in root-leaf traits of seedling, focus on the relative positions of seeds within different layers: beneath or above the litter layer, or within the bare soil layer (without litter). Our findings provided evidence supporting a coordinated relationship between root and leaf traits, wherein leaf traits varied in conjunction with root traits in the relative positions of seeds. Specifically, we observed that seedlings exhibited higher values for specific leaf area and average root diameter, while displaying lower root tissue density. The mixed model explained 86.1% of the variation in root-leaf traits, surpassing the variation explained by the relative positions. Furthermore, soil nitrogen acted as a mediator, regulating the relationship between seedling growth and root-leaf traits, specifically leaf dry matter content and root tissue density. Therefore, future studies should consider artificially manipulating tree species diversity based on root-leaf traits characteristics to promote forest recovery.

The escalation of global nitrogen deposition levels has heightened the inhibitory impact of phosphorus limitation on plant growth in subtropical forests. Plant roots area particularly sensitive tissue to nitrogen and phosphorus elements. Changes in the morphological characteristics of plant roots signify alterations in adaptive strategies. However, our understanding of resource-use strategies of roots in this environment remains limited. In this study, we conducted a 10-month experiment at the Castanopsis kawakamii Nature Reserve to evaluate the response of traits of seedling roots (such as specific root length, average diameter, nitrogen content, and phosphorus content) to nitrogen and phosphorus addition. The aim was to reveal the adaptation strategies of roots in different nitrogen and phosphorus addition concentrations. The results showed that: (1) The single phosphorus and nitrogen–phosphorus interaction addition increased the specific root length, surface area, and root phosphorus content. In addition, single nitrogen addition promotes an increase in the average root diameter. (2) Non-nitrogen phosphorus addition and single nitrogen addition tended to adopt a conservative resource-use strategy to maintain growth under low phosphorus conditions. (3) Under the single phosphorus addition and interactive addition of phosphorus and nitrogen, the roots adopted an acquisitive resource-use strategy to obtain more available phosphorus resources. Accordingly, the adaptation strategy of seedling roots can be regulated by adding appropriate concentrations of nitrogen or phosphorus, thereby promoting the natural regeneration of subtropical forests.

Soil fungal communities play a critical role in the promotion of nutrient cycling and the stabilization of ecosystem functions in subtropical forests. Yet, clarifying the relationships between soil fungal diversity and microclimate variability along an elevational gradient, as well as understanding the driving mechanisms of their variations in subtropical forests, remains insufficiently understood. In this study, we recorded the composition and soil fungal diversity along an elevational gradient in Daiyun Mountain of China, aiming to elucidate the primary factors influencing the structure of the dominant soil fungal along an elevational gradient in subtropical forests. The results showed that (1) the dominant phylum of soil fungi at different elevations were Basidiomycota, Ascomycota (relative abundance > 10%) and Zygomycota (relative abundance > 1%). The Simpson index of soil fungi showed a clear upward trend along the elevational gradient, while no significant difference was observed in the other indices, and both overall reached their maximum value at the elevation of 1200 m. (2) The mean annual soil temperature and moisture, soil pH and available phosphorus were the main factors driving the dominant soil fungal along the elevational gradient. (3) Co–occurrence network analyses revealed a distinct modular structure of dominant soil fungal communities at different elevations, with Ascomycetes identified as the key taxa in fungi network relationships. Our research holds ecological significance in understanding the pivotal role of soil environmental factors in shaping the complex composition and interactions within soil fungal communities.

The investigation of taxonomic diversity within island plant communities stands as a central focus in the field of island biogeography. Phylogenetic diversity is crucial for unraveling the evolutionary history, ecological functions, and species combinations within island plant communities. Island effects (area and isolation effect) may shape species distribution patterns, habitat heterogeneity affects habitat diversity, and anthropogenic disturbances can lead to species extinction and habitat destruction, thus impacting both species diversity and phylogenetic diversity. To investigate how taxonomic and phylogenetic diversity in island natural plant communities respond to island effects, habitat heterogeneity, and anthropogenic disturbances, we took the main island of Haitan (a land-bridge island) and nine surrounding islands (oceanic islands) of varying sizes as the subjects of our study on the Pingtan islands. We aim to elucidate the influence of island effects, habitat heterogeneity, and anthropogenic disturbances on taxonomic and phylogenetic diversity. The results showed that, (1) Both the taxonomic and phylogenetic diversity of plants on the Pingtan islands followed the island area effect, indicating that as the island area increases, both taxonomic and phylogenetic diversity also increase. (2) Island effects and habitat heterogeneity were found to enhance taxonomic and phylogenetic diversity, whereas anthropogenic disturbances were associated with a decrease in both taxonomic and phylogenetic diversity. Furthermore, the synergistic influence of island effects, habitat heterogeneity, and anthropogenic disturbances collectively exerted a negative impact on both taxonomic and phylogenetic diversity. (3) The contribution of explanatory variables of anthropogenic disturbances for taxonomic and phylogenetic diversity was higher than that of island effects and habitat heterogeneity. Additionally, the contribution of the explanatory variables under the combined influence of island effects, habitat heterogeneity, and anthropogenic disturbances is higher than that of the individual variables for island effects and habitat heterogeneity. These findings suggest that anthropogenic disturbances emerged as the dominant factors influencing both taxonomic and phylogenetic diversity. These findings demonstrate the intricate interplay between island effects, habitat heterogeneity, and anthropogenic disturbances, highlighting their combined influence on both taxonomic and phylogenetic diversity on island.

Evaluating the carbon storage of forests and identifying the factors that influence it are essential in working towards the “dual carbon” goal. This assessment will facilitate research on carbon neutrality and promote regional ecological protection and development. This study utilized the “One Map” data of forest resources (2020) and the first year (2017) of the establishment of the national park in Wuyi Mountain National Park (WMNP). The continuous biomass expansion factor method, in conjunction with the vegetation carbon content coefficient, was employed to estimate the forest carbon storage within the park’s forested areas. Subsequently, the distribution of forest carbon storage was analyzed using remote sensing estimation methods, and a comparison was made between the forest carbon storage of these two years. Finally, correlation analysis and path analysis were conducted to identify the primary factors influencing forest carbon storage. The study findings reveal that in 2020, the total carbon storage in forests reached 4.851 × 106 t C, with an average carbon density of 49.55 t C·hm−2. Furthermore, the study identified positive correlations between dominant tree species, age groups, and elevation with carbon storage, whereas slope length and aspect were found to have negative correlations. Dominant tree species were observed to have the greatest impact on forest carbon storage in both 2017 and 2020, followed by age groups. These findings offer valuable scientific insights for the implementation of forest carbon storage pilot projects in WMNP.

Revealing the assembly mechanisms of the soil microbial community, which is crucial to comprehend microbial biodiversity, is a central focus in ecology. The distribution patterns of microbial elevational diversity have been extensively studied, but their assembly processes and drivers remain unclear. Therefore, it is essential to unravel the relationship between the deterministic and stochastic processes of the microbial community assembly and elevational gradients. Here, our study built upon previous physicochemical analyses of soil samples collected along an elevational gradient (900–1500 m) in Daiyun mountain, a subtropical forest located in southeastern China. Using the phylogenetic-bin-based null model analysis (icamp) and multiple regression on matrices approach, we explored the major drivers that influence the assembly processes of soil bacterial and fungal community across elevations. The results showed that: (1) bacterial rare taxa exhibited a broad habitat niche breadth along the elevational gradient; (2) homogeneous selection and homogenizing dispersal proved to be the most important assembly processes for the bacterial and fungal community; (3) soil phosphorus availability mediated the relative importance of deterministic and stochastic processes in the soil microbial community. Notably, the relative abundance of dominant microbial taxa controlled by homogeneous selection and homogenizing dispersal increased with increasing soil phosphorus availability. Collectively, the assembly processes of microbial elevational communities of the subtropical mountains in China can be explained to some extent by variations in the soil phosphorus availability. This conclusion provides valuable insights into the prediction of soil microbial diversity and phosphorus nutrient cycling in subtropical montane forests.

Plants allocate growth to different organs as a strategy to obtain limiting resources in different environments. Tree seeds that fall from a mother tree settle on, within, or below the forest floor and litter layer, and their relative positions can determine seedling biomass and nutrient allocation and ultimately affect survival to the sapling stage. However, how emerged seedling biomass and nutrients of each organ are affected by seeds in different positions is not yet completely understood in subtropical forests. Therefore, an experiment was conducted with seeds positioned above the litter layers of different thicknesses, on the forest floor, and beneath the litter layer, and the influences of seed position on biomass allocation and nutrient use efficiency of emerged seedlings of Castanopsis kawakamii was examined. The aim of the study was to determine the optimal seed position to promote regeneration. Allocation strategies were well coordinated in the emerged seedlings from different seed positions. Seedlings from seeds positioned above litter layers of different thicknesses (~40 and 80 g of litter) allocated growth to leaf tissue at the expense of root tissue (lower root mass fraction) and increased nitrogen (N) and phosphorus (P) accumulation and nutrient use efficiency. Seedlings from seeds positioned beneath a deep litter layer allocated most growth to roots (high root: shoot ratio, root mass fraction) to capture available resources at the expense of leaf growth. Seedlings from seeds positioned on the forest floor allocated most growth to roots to obtain limiting resources. Further, we also found that these traits were clustered into three groups based on trait similarity, and the cumulative interpretation rate was 74.2%. Thus, seed relative positions significantly affected seedling growth by altering the allocation of resources to different organs. The different strategies indicated that root N:P ratios (entropy weight vector was 0.078) and P nutrient use efficiency were essential factors affecting seedling growth in the subtropical forest. Of the seed positions analyzed, beneath a moderate litter layer (~40 g of litter) was the most suitable position for the growth and survival of Castanopsis seedlings. In future studies, field and lab experiments will be combined to reveal the mechanisms underlying forest regeneration.

Cellulose and lignin are the principal constituents of plant litter, and their degradation plays an important role in the maintaining the soil carbon balance in terrestrial ecosystems. Yet, our knowledge of the responses of litter mass loss and cellulose and lignin degradation to litter quality, environmental factors, and taxonomic diversity indices along an elevational gradient in subtropical forests remains sparse. To gain insight into litter decomposition dynamics and its influencing factors, we investigated the cellulose and lignin degradation of foliar litter that from the two most dominant tree species along an elevational gradient (900–1,600 m) in a subtropical forest on Daiyun Mountain, China. Our results showed the following. (1) The degradation rate of cellulose was higher than that of lignin for litter collected at each elevation. The mass loss for foliar litter at different elevations was greater in the early period (0–180 days) than later period (180–270 days). (2) Litter quality, as well as environmental factors and taxonomic diversity indices, together influenced the foliar litter mass loss rate in addition to the rates of cellulose and lignin degradation. The key environmental factors included air and soil temperature, which had significant correlations with litter decomposition positively. The litter quality, namely is N (nitrogen) and P (phosphorus) contents, had significant positive correlations with degradation rates of cellulose and lignin in litter, and vice versa for lignin/N and C/N ratios. Some of the taxonomic diversity indices had positive correlations with litter decomposition, indicating that the input of highly diver litter material leads to a non-additive effect. (3) The litter decomposition was affected by the combination of litter quality, environmental factors, and taxonomic diversity indices. Of these, however, the environmental factors are the main factors that controlled the litter decomposition along elevational gradients in this subtropical forest. The results could provide a theoretical basis for understanding foliar litter nutrient release for the subtropical forest ecosystem of China.

The formation of a canopy gap results in changes to the microenvironment which, in turn, affect litter decomposition and nutrient release. However, the mechanisms underlying these effects in differently sized gaps and non-gaps remain poorly understood. To address this gap in knowledge, we selected three large gaps (above 150 m2), three medium gaps (50–100 m2), three small gaps (30–50 m2), and three non-gaps with basically the same site conditions. We then used the litter bag method to investigate leaf and branch litter decomposition over a year in a Castanopsis kawakamii natural forest with the aim of characterizing the litter mass remaining and the nutrient release in canopy gaps and non-gaps. Our results revealed that the remaining litter mass of leaf and branch litter was lower in medium gaps compared to other gaps, and leaf litter decomposed faster than branch litter. Environmental factors were identified as the primary drivers of total carbon and nitrogen release during litter decomposition. Gap size (canopy openness), taxonomic Margalef index, the Brillouin index of soil microbes, soil total nitrogen content, soil pH value, and average air temperature were identified as the main factors driving carbon and nitrogen release from branch litter. In the late decomposition stage, the taxonomic Pielou index, soil total potassium content, soil water content, and average relative air humidity were the main drivers of nutrient release from branch litter. The soil water content and average relative air humidity were also found to be the main factors affecting the nutrient release from leaf litter throughout the different stages of decomposition. Overall, our study highlights the impact of canopy gaps on microenvironmental variation, taxonomic community diversity, and soil microbial functional diversity and how these factors ultimately influence litter decomposition and nutrient release. Our findings provide an important foundation for further research into soil nutrient cycling in subtropical natural forests.

To understand how diversity change with environmental gradients is a fundamental aim for clarifying biodiversity pattern and underlying mechanisms. Here, we studied the characteristics of beta diversity and its partitioning components for woody plant communities along an elevation gradient in subtropical forests of China, and thus explored the effects of environment and space on beta diversity. By using the Classification Method, we divided the species of Daiyun Mountain into four groups, namely generalists, high-elevation specialists, low-elevation specialists and rare species. We then calculated beta diversity, and partitioned it into species turnover and species nestedness. dbRDA was conducted to analyze the impact of spatial and environmental distance on the beta diversity and its partitioning components. Beta diversity comprised of two components: species turnover and species nestedness. Species turnover was the larger contributor to total beta diversity, and it tended to increase as elevation changed. This pattern can be attributed to environmental heterogeneity, resulting in the differentiation of specialized species and an increase in species turnover and beta diversity. Environmental factors, specifically the air temperature and slope, played a significant role in explaining the variation of turnover and beta diversity. However, spatial variables did not have a significant influence on these patterns. The maintenance of biodiversity in Daiyun Mountain was mainly governed by environmental filtering. Future conservation efforts should focus on strengthening the protection of specialized species in high elevation areas.

When seeds fallen from the mother trees, their initial contact physical environment was litter or soil. The dispersal positions of seeds (seeds positioned on top of the litter, the soil surface and beneath the litter) determine the process of their natural regeneration. We simulated three different dispersal positions of Castanopsis kawakamii, including seeds positioned on top of the litter (2 and 4 cm litter was placed below the seed layer), soil surface (without litter), and seeds beneath the litter (2, 4, 6 and 8 cm litter covers in the upper layer of seeds). We examined the effects of seed dispersal position on the chlorophyll fluorescence characteristics, non-structural carbohydrate, specific leaf area, leaf dry matter content and nutrient content of seedlings. The results showed that leaf nitrogen content per area of seedlings had significantly positive correlation with soluble sugar content, non-structural carbohydrate content, and negative correlation with specific leaf area across different dispersal positions. Seedlings of the moderate litter cover (2 and 4 cm) adopted resource acquisitive strategies by increasing relative chlorophyll content, soluble sugar content, non-structural carbohydrate content, leaf dry matter content, leaf nitrogen content and phosphorus contents per area, and decreasing specific leaf area to achieve their demands for rapid growth. Seedlings grew on soil surface and beneath the deep litter (6 and 8 cm) adopted the resource conservative strategies with higher leaf nitrogen content per mass and specific leaf area, lower leaf dry matter content, and non-structural carbohydrate content to intercept more effective light resources to compensate for the shady environment brought by deep litter. This would further decrease the probability of seedling mortality due to 'carbon starvation'. Seedlings under litter layer stored starch in leaf, and reduced the energy consumption of photosynthetic tissues (low PSⅡ maximum photochemical efficiency) to maintain seedling growth. Comprehensive analysis of entropy method indicated that low amount of litter cover (2 cm) significantly promoted seedling growth of C. kawakamii. In the future, we could regulate the thickness of litter layer to promote the growth and regeneration of C. kawakamii seedlings in natural forest.

林窗是森林更新演替的重要环节,揭示林窗环境下功能性状变异来源及其相对贡献,有助于阐明植物对林窗环境的响应.该研究以中亚热带格氏栲(Castanopsis kawakamii)天然林为对象,设置9个不同大小的林窗样地,运用方差分解探讨林窗、物种和个体对叶性状变异的相对贡献,采用线性回归分析不同大小林窗下群落性状变化及种间和种内性状变异的重要性.研究发现:(1)格氏栲天然林林窗植物比叶面积、叶干物质含量、叶厚和叶绿素含量由种间性状变异主导,叶氮含量由种内性状变异主导,叶磷含量受林窗大小影响最大.(2)群落叶磷含量与林窗大小具有显著正相关关系,土壤温度和水解氮含量对群落叶磷含量具有显著正效应,土壤有效磷含量具有显著负效应.(3)沿林冠开放度的群落叶磷含量变化主要由种内性状变异引起,优势种扮演着重要角色.结果表明,格氏栲天然林林窗环境下植物功能性状仍以种间性状变异为主(平均41％),但沿林窗环境梯度的群落性状变化主要源自种内性状变异,通过植物表型可塑性响应环境改变,优势种作用明显.

土壤微生物作为森林生态系统的主要分解者,参与土壤养分循环,在维持土壤生态系统功能和服务中发挥着重要作用.探讨不同海拔土壤微生物群落结构和功能多样性的季节变化,对维持土壤生态系统稳定具有重要研究价值.以戴云山南坡不同海拔土壤为研究对象(900-1500 m),采用Biolog-ECO微平板法,研究不同海拔土壤微生物群落结构和功能多样性的季节变化(夏季与冬季),揭示驱动戴云山不同海拔土壤微生物季节变化的主要因素.结果表明:(1)夏季海拔1400 m区域土壤微生物的碳源利用最强,微生物活性最高.冬季表现为海拔900 m处土壤微生物对碳源利用最强,活性最高.(2)土壤微生物群落对碳源利用特征的研究表明,夏季与冬季中氨基酸类和羧酸类碳源是7个海拔土壤微生物利用的主要碳源,且夏季碳源利用程度高于冬季.(3)冗余分析表明夏季和冬季戴云山南坡7个海拔土壤微生物群落功能多样性均受土壤环境因子驱动,解释量分别为72.63％和44.12％,均高于地形因子的解释量.(4)土壤温度和全钾含量等因子是驱动夏季土壤微生物群落功能多样性变化的主要因素;土壤全钾、全磷、有效磷含量和坡向是驱动冬季土壤微生物群落功能多样性变化的主要因素.海拔和季节变化通过调节土壤理化性质和土壤酶活性,进而影响森林土壤微生物群落结构和功能多样性.

The internal correlation of plant, litter and soil stoichiometric characteristics and their responses to the environment are helpful for revealing nutrient cycling mechanisms. However, few studies have assessed the nutrient relationship between plant, litter and soil and nutrient stock along elevational gradients, which limit the understanding of nutrient relationships in the ecosystem. To gain insight into the forces of nutrient stock and its stoichiometric ecological characteristics along the elevational gradients in forest ecosystem, we investigated the carbon (C), nitrogen (N) phosphorus (P) contents and stoichiometric ratios of dominant plants, litter and soil layers at different elevations (900–1600 m) in Daiyun Mountain. The results showed the following: (1) C, N and P contents showed an increasing order as plant > litter > soil in each elevation of Daiyun Mountain. Dominant plants were limited by N each elevation. C, N and P contents of plants at high elevation were higher than those at low elevation and significant correlations were found between plant and litter TN, TP and air and soil temperature (negative), which conforms to the Temperature-Plant Physiological Hypothesis (TPPH). (2) Significant correlations were found between plant C:N and litter C:N (positive); between litter C:P and soil N:P (positive); and between litter C:P and soil C:N (negative). (3) Elevation and slope were essential environmental factors to the stoichiometric ratio of plant and litter, and pH was the main factor that correlated negatively to soil stoichiometry ratio. Litter provided a link between plant and soil, and there was a coupling among plant, litter and soil nutrients. The results could provide a theoretical basis for understanding the nutrient cycling for the subtropical forest ecosystem of China.

土壤微生物作为森林生态系统主要驱动力,是影响生态系统物质循环和养分转化的重要因素.探讨不同海拔和季节森林土壤微生物群落的分布规律,对理解土壤生态过程和预测土壤生态系统功能具有重要研究意义.以戴云山南坡不同海拔森林土壤(海拔900～1 500 m)为研究对象,探讨夏季和冬季不同海拔土壤微生物群落结构和功能多样性,揭示驱动土壤微生物群落变化的主要因素.结果表明:①夏季土壤微生物群落中革兰氏阳性菌含量最高,冬季土壤真菌含量最高,海拔1 200 m处土壤总磷脂脂肪酸含量均高于其它海拔.随海拔升高,冬季土壤微生物群落中土壤真菌群比细菌群占据更大优势.②冗余分析表明,夏季7个海拔土壤微生物群落磷脂脂肪酸(PLFA)含量主要受环境因子和地形因子共同作用,累计解释量达56.72％;冬季土壤微生物群落磷脂脂肪酸含量主要受环境因子驱动,单独解释量达52.23％,环境因子和地形因子累计解释量为55.37％.③土壤全碳含量、土壤pH和多酚氧化酶是驱动夏季土壤微生物群落变化的主要因子;土壤有效磷、全钾、全碳含量和土壤pH是驱动冬季土壤微生物群落变化的主要因子.

种子从母株掉落于地面萌发后,其根系在不同散布位置(凋落物上层、土壤表层和凋落物下层)的生长形态影响幼苗定居及建成,而目前对其根系形态及生长特征的了解并不充分,限制了对幼苗根系在不同散布下适应策略的理解.为此,以格氏栲(Castanopsis kawakamii)为研究对象,通过模拟种子在凋落物中位置,设置凋落物上层(种子下层铺垫2 cm和4 cm凋落物,U2和U4处理)、土壤表层与凋落物下层(种子上层覆盖0、2、4、6 cm和8 cm凋落物,CK、D2、D4、D6和D8处理)等3种散布,探讨不同散布位置对格氏栲幼苗根系9个生长指标的影响.结果表明:(1)种子散布位置对幼苗根干物质质量具有显著影响,D2处理达最大值.(2)D2处理的幼苗根长、根表面积、根尖数、分枝数和比根长高于其它处理;根系平均直径在D6处理达最大值.(3)相关分析表明根长、根表面积、根尖数、分枝数和比根长与根系平均直径呈显著负相关关系.(4)对根系9个生长指标提取主成分后聚类为4个类群,D2与D4处理各划分一类;U2与U4处理划分一类,其余三个处理划分一类.综上所述,凋落物浅层覆盖(D2处理)适宜格氏栲根系生长;凋落物上层(U2和U4处理)种子萌生根根系受凋落物阻隔作用阻止其与土壤接触,而一旦根系与土壤接触,生长速度加快;土壤表层(CK处理)受地表光照及水分条件限制及凋落物深层覆盖(D6和D8处理)的幼苗受深层凋落物产生的机械阻碍力影响,通过调整对根干物质质量的投入和根系形态可塑性来适应种子散布.因此,在幼苗根系快速生长阶段,通过人为干扰方式,适当调节森林凋落物厚度,以促进格氏栲幼苗在林内更新.

Forest gaps affect the soil microbial community structure and soil function by altering the ambient environment. This study aimed to explore the effects of environmental factors on soil microbial communities and enzyme activities in Castanopsis kawakamii forest gaps. The soil properties, soil enzyme activities, and microbial composition inferred by high-throughput sequencing were determined to quantify the soil eco-physiological functions. A redundancy analysis and linear model (LM) were further used to test the significance of forest-gap effects on soil microbial community structure and its function. The formation of gaps significantly increased the canopy openness (CO) and soil temperature (ST), and the small gaps (GS) and large gaps (GL) were the most conducive to the accumulation of soil total nutrients. Soil characteristics in GS provided a favorable environment for microbial growth, which promoted the soil microbes and function in these forest gaps. The soil physical–chemical properties in GM were relatively low and influenced its soil function, resulting in this gap size having the lowest enzyme activities. Forest gaps govern the soil microbiomes and soil function by regulating gap characteristics and soil properties. Meanwhile, the presence of dominant microorganisms promoted enzyme activities. These results could help further our understanding of the impact of forest gaps on the soil process and forest succession.