Elevation provides a critical environmental context for studying the photosynthetic adaptation mechanisms of plants and is of great significance for understanding plant responses and acclimation to environmental change. Although elevational variation strongly influences photosynthetic capacity, the underlying regulatory mechanisms remain insufficiently understood. This study addresses this gap by systematically examining the photosynthetic and anatomical adaptations of two dominant tree species with contrasting functional types, Sorbus rehderiana Koehne (deciduous broad-leaved tree) and Quercus aquifolioides Rehd. et Wils (evergreen broad-leaved tree), distributed widely along the eastern edge of the Qinghai-Tibetan Plateau, China. Our findings reveal distinct adaptive strategies. S. rehderiana enhances CO2 assimilation efficiency at higher elevations (in the 2600-3400 m a.s.l.) by increasing the surface area of mesophyll cells and chloroplasts exposed to intercellular airspace (Sm and Sc), reducing cell wall thickness (Tcw) and optimizing nitrogen allocation within the photosynthetic apparatus. These modifications maximize carbon gain during a short growing season. In contrast, Q. aquifolioides adopts a conservative strategy by reducing photosynthetic capacity at higher elevations, allocating more nitrogen to structural tissues, increasing Tcw and reinforcing mechanical defenses, thereby prolonging leaf lifespan in high-elevation environments. This study reveals the intrinsic mechanisms underlying the elevational variation in photosynthetic capacity between deciduous and evergreen trees and provides a scientific basis for improving predictions of the plants' response to future climate change.

Aims Ectomycorrhizal trees obtain nitrogen(N)through direct root uptake from soil(root pathway)and via ectomycorrhizal fungal mycelia translocated to roots(mycelia pathway).However,the relative contribution of the mycelial pathway to tree N acquisition(ffungi)remain highly uncertain,and the key influencing factors are not well defined in natural ecosystems. Methods In this study,we employed the 15N natural abundance method to quantify the relative contribution of the mycelial pathway to N acquisition in two ectomycorrhizal trees(Abies fargesii var.faxoniana and Betula utilis)on the eastern Qingzang Plateau.We further analyzed the influencing factors of ffungi. Important findings Our results showed that the contribution of mycelia pathways to total N uptake was comparable to that of root pathways in both A.fargesii var.faxoniana and B.utilis.Specifically,the mycelia pathway contributed to 33.6％-71.8％ of total N uptake in A.fargesii var.faxoniana and 41.6％-63.0％ in B.utilis.Moreover,the soil carbon to nitrogen ratio,mean annual temperature and soil pH were identified as a key influencing factor for ffungi.This study provides perspectives and insights for understanding N acquisition strategies and their influencing factors in ectomycorrhizal trees within natural ecosystems.

四川米亚罗森林生态系统国家定位观测研究站(简称“米亚罗生态站”)可追溯至1955年,从我国生态站网络奠基人蒋有绪在川西亚高山林区开展植物群落类型调查开始.米亚罗生态站的创建开拓我国森林定位观测研究的新纪元,相关研究成果为长江上游水源涵养林保护、生态屏障等国家战略的确立提供科学依据.本文回顾总结米亚罗生态站70年来在森林气象与水文、恢复与演替、碳固持与循环、气候变化响应与适应等领域的研究成果.本文着重指出川西亚高山森林具有强大的水源涵养和固碳增汇潜力,是当前森林生态系统修复与多功能精准提升研究的天然“实验室”.继续开展川西森林长期定位监测研究,加强多学科交叉与融合创新,实现科学研究、观测评估、示范应用、社会服务等一站多能定位,将会对引领西南林区森林保护与修复、生态系统功能提升和森林可持续经营等方面的研究提供引领与示范.

Plantations are becoming more common globally as one of the important initiatives to mitigate global climate change, but the results on whether the soil organic carbon (SOC) can reach the level of natural forests are still inconsistent. Here, we conducted a meta-analysis of 418 paired observations, comparing plantations to adjacent natural forests (primary and secondary forests), from 47 published studies to explore the global patterns and associated drivers of SOC functional fractions (particulate OC, POC; mineral-associated OC, MAOC) and their ratios (the ratio of POC to MAOC, POC:MAOC; the ratio of POC to SOC, POC:SOC; the ratio of MAOC to SOC, MAOC:SOC). We found significant reductions of POC (42.4%, 35.9%), MAOC (19.4%, 15.2%), POC:MAOC (29.0%, 25.5%), and POC:SOC (18.2%, 18.9%) in plantations compared to primary and secondary forests. In contrast, MAOC:SOC in plantations had no change. The effects of plantations on POC, MAOC and their ratios were significantly affected by tree species, plantation age, soil type, and soil depth. Moreover, soil physical properties (soil bulk density, mean weight diameter), element contents (total phosphorus) and microbial communities (microbial biomass C) appeared to be drivers of lower POC, MAOC and their ratios in plantations. Our findings suggest that the reduction of SOC in plantations is mainly distributed in relative labile POC. The results reveal that the SOC functional fractions in plantations developed over time and were comparable to adjacent secondary forests after about 60 years, and plantations with native species will be more conducive to the formation of POC and MAOC. We emphasize that primary forests are not replaceable, and plantations with native species might be a reliable way for restoring a stable distribution of SOC.

Morphological plasticity (MP) is an essential strategy for plants in nutrient acquisition, disturbance alleviation, and community coexistence during environmental and climatic changes. However, to date, there has been little research concerning the MP for alpine–subalpine forests on the Qinghai–Tibet plateau. These forests are representative of the ectomycorrhizal (ECM) type, and morphological traits of these ECM roots, such as root tip lengths, diameters, and their adherent hyphal lengths and exploration types, have rarely been studied in the context of nutrient and environmental gradients. In this study, we examined the morphological traits of ECM roots for faxon fir (Abies fargesii var. faxoniana), which dominated in subalpine forests across nine elevations on the Eastern Qinghai–Tibet plateau. By quantifying ca. 90,000 root tips, the hyphal lengths of ectomycorrhizal extraradical mycelium (EEM, i.e., short- and long-distance exploration types) reached up to 1.1 × 106 cm/m3 in soil, which decreased significantly due to gradually increasing altitude. In contrast, the variability of ECM root traits (diameter, length, and superficial area) was highly conserved along the altitudinal gradients, yet the root tip lengths were positively associated with soil protease enzyme activity. The increase in diameter and length of ECM root tips was climate-independent yet significantly associated with increasing root N concentration. In the studied forests, a long-distance exploration type of ECM hyphae was controlled by precipitation (p < 0.05), whereas the short-distance one was controlled by precipitation and temperature simultaneously. The EEM lengths of short- and long-distance exploration types were associated with high C concentration and low N concentration in host tree root tissues. Our findings demonstrated that MP expression in nutrient-foraging strategies for the dominant coniferous trees facilitates the adaptation to changing environments by specialized hyphal structures. In conclusion, ECM root tips and hyphal structures are two dimensions of functional traits linked to root N concentration in opposite ways, and their MP collectively ensures the temporal stability and resistance of subalpine forests on the Qinghai–Tibet plateau. These results provide new insights into ECM morphological traits and their adaptation in changing environments, which is valuable for understanding responses of subalpine forests to climate change.

As the most senstitive plant organs to environmental changes, leaves serve as crucial indicators of plant survival strategies. We measured the morphology, anatomical traits, gas exchange parameters, and chlorophyll fluorescence parameters of Quercus aquifolioides (evergreen broad-leaved) and Sorbus rehderiana (deciduous broad-leaved) at altitudes of 2600, 2800, 3000, 3200 and 3400 m on the eastern edge of the Qinghai-Tibet Plateau, China. We explored the similarity and difference in their responses to altitude change and the ecological adaptation strategy. The results showed that as the altitude increased, leaf dry matter content of Q. aquifolioides decreased, that of S. rehderiana increased, leaf size for both species gradually decreased, and the palisade coefficient of Q. aquifolioides showed a decreasing trend, contrasting with the increasing trend in S. rehderiana. As the altitude increased, the thickness of leaves, palisade tissue, spongy tissue, upper epidermis, and lower epidermis of both species increased significantly, with the increment of 22.4%, 4.9%, 45.1%, 23.3%, 19.6%, and 28.2%, 46.9%, 8.9%, 25.9%, 20.8% at altitude of 3400 m, respectively, compared with the altitude of 2600 m. The gas exchange and chlorophyll fluorescence parameters of S. rehderiana significantly increased with increasing altitude, while Q. aquifolioides showed the opposite trend. Leaf anatomical traits, gas exchange, and chlorophyll fluorescence parameters of both species displayed considerable plasticity. There were significant correlations among most leaf traits and between leaf traits and altitude. The survival strategy of Q. aquifolioides was more conservative in response to altitude changes, while that of S. rehderiana was more active. Both species adapted to different altitudes by adjusting their own traits.

The natural abundance of stable carbon and nitrogen isotopes (δ13C and δ15N) in leaves can provide comprehensive information on the physiological and ecological processes of plants and has been widely used in ecological research. However, recent studies on leaf δ13C and δ15N have focused mainly on woody species, few studies have been conducted on herbs in different vegetation types, and their differences and driving factors are still unclear. In this study, we focused on the herbs in subalpine coniferous forests, alpine shrublands, and alpine mea-dows on the eastern Qinghai-Tibet Plateau, and investigated the differences in leaf δ13C and δ15N of herbs and the driving factors. The results showed that there were significant differences in leaf δ13C and δ15N values of herbs among different vegetation types, with the highest δ13C and δ15N values in alpine meadows, followed by alpine shrublands, and the lowest in subalpine coniferous forests. Using variation partitioning analysis, we revealed that differences in leaf δ13C and δ15N of herbs among various vegetation types were driven by both leaf functional traits and climate factors, with the contribution of leaf functional traits being relatively higher than that of climate factors. Hierarchical partitioning results indicated that mean annual temperature (MAT), chlorophyll content index, leaf nitrogen content per unit area (Narea), and leaf mass per area were the main drivers of leaf δ13C variations of herbs across different vegetation types, while the relative importance of Narea and MAT for variation in leaf δ15N of herbs was much higher than those other variables. There was a strong coupling relationship between leaf δ13C and δ15N as indicated by the result of the ordinary least squares regression. Our findings could provide new insights into understanding the key drivers of leaf δ13C and δ15N variations in herbs across different vegetation types.

Soil stable carbon isotope (soil δ13C) can reflect soil carbon metabolic processes and record environmental and vegetation change information, so mapping the spatial distribution of soil δ13C (isoscapes of soil δ13C) can help us better understand the spatial variability of ecosystem carbon cycles. However, efficient approaches for obtaining the isoscapes of soil δ13C remain challenging, especially in mountainous areas with complex terrain. A total of 150 soil samples were collected and their soil δ13C was measured to investigate the spatial variation of soil δ13C in an alpine-gorge region on the eastern Qinghai-Tibetan Plateau which is characterized by complex terrain. Four prediction methods included ordinary kriging interpolation, multiple linear regression, random forest regression, and geographically weighted regression (GWR) were selected and compared to find the best prediction model for mapping the isoscapes of soil δ13C. The pathways of vegetation, topography, soil, and spatial factors influencing the spatial variability of soil δ13C were explored using variance partitioning analysis and structural equation model. The soil δ13C was significantly different among vegetation types, and ranged from −27.155‰ to −9.647‰. The spatial heterogeneity of soil δ13C showed moderate variation, and was dominated by spatial structural factors. The GWR model had higher prediction accuracy in the modeling soil δ13C in comparison to other models. Soil carbon to nitrogen ratio and normalized difference vegetation index were the main factors determining the spatial variability of soil δ13C, and other topographic and soil factors indirectly regulated the spatial distribution of soil δ13C by influencing these two factors. Our results provided a useful tool (GWR model) for mapping the isoscapes of soil δ13C and explored the factors controlling the spatial variability of soil δ13C in the alpine-gorge region on the eastern Qinghai-Tibetan Plateau, which are important for an in-depth understanding of soil carbon cycling in mountain ecosystems.

Plant aboveground biomass reflects the resilience of ecosystem productivity to different environmental factors and plays an important role in biodiversity and ecosystem carbon cycles. Although many studies have investigated the relationship between aboveground biomass and species diversity, stand structural diversity is an important factor affecting ecosystem function. The mechanism of how climate and soil factors affect aboveground biomass through species diversity and structural diversity remains unclear. Here, combing data from 8 locations of Abies fargesii var. faxoniana primary forest, a structural equation model was used to study the effects of climate factors, soil factors, species diversity, and structural diversity on aboveground biomass. Our results demonstrated that climate factors affect aboveground biomass mainly through the indirect effect of species diversity. Species diversity indirectly affects aboveground biomass through its effects on structural diversity. Both direct effects of soil factors and indirect effects through structural diversity can significantly affect aboveground biomass. Therefore, maintaining higher diversity of stand structure and soil nutrients can improve aboveground biomass, and thus better improve ecosystem functions such as carbon storage.

Despite the sensitivity to climate change in the alpine-gorge region on the eastern Qinghai-Tibetan Plateau, comprehensive information on the elevational variation patterns of plant intrinsic water use efficiency (iWUE) and plant nitrogen (N) availability in this region is still lacking. To explore the elevational patterns and their drivers of plant iWUE (calculated from leaf δ13C) and plant N availability (assessed by leaf δ15N) of different plant growth forms, plant iWUE and leaf δ15N of 654 observed samples of 158 species from seven typical vegetation types distributed along the elevation were investigated, and the effects of taxonomic identity, leaf functional traits, soil and climatic factors on them were explored by linear mixed-effects model. It was found that both plant iWUE and leaf δ15N differed significantly among different plant growth forms, with plant iWUE showed shrubs > herbs > trees and leaf δ15N showed herbs > shrubs > trees. The plant iWUE and leaf δ15N showed a U-shaped pattern along elevation, and the elevation patterns of different plant growth forms were consistent. The plant iWUE of different growth forms first decreased and then increased with increasing humidity index, and the humidity index breakpoints of different plant growth forms were different. The leaf δ15N of herbs and shrubs showed a significantly positive correlation with humidity index, whereas the leaf δ15N of trees had an insignificant correlation with humidity index. The elevation variations of plant iWUE and leaf δ15N of different plant growth forms were jointly influenced by biotic (i.e., plant taxonomy and leaf functional traits) and abiotic (i.e., soil and climate) factors, but were mainly determined by biotic factors. Our results showed that the significant coupling between plant iWUE and leaf δ15N did not vary by plant growth forms, thereby suggesting a close link between carbon and N cycles. This study deepens our knowledge regarding elevation variations and their drivers of plant iWUE and leaf δ15N, and confirms the importance of biotic factors on plant iWUE and leaf δ15N variations along elevation gradients in the alpine-gorge region.

The study aimed to reveal the elevational patterns and drivers of leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometry at both the individual and community levels in the alpine-gorge region on the eastern Qinghai-Tibetan Plateau. Based on the datasets of leaf C, N and P concentrations from 665 field samples and information on plant community structure from 150 plots along the elevation, linear mixed model and general linear model were used to identify drivers of leaf C, N, and P concentrations and their stoichiometry at the individual and community levels, respectively. Leaf C, N, and P concentrations and their stoichiometry showed a linear elevation pattern at the individual level and a nonlinear elevation pattern at the community level. At the individual level, elevational variations in leaf C, N, and P concentrations and their stoichiometry were determined mainly by plant taxonomy and growth forms. At the community level, interspecific variation was larger than intraspecific variation for leaf C, N concentrations, and C/N, whereas intraspecific variation was larger than interspecific variation for leaf N/P. The interspecific variation in leaf C, N, and P concentrations and their stoichiometry was affected jointly by edaphic and climatic factors, whereas edaphic factors mainly drove their intraspecific variation. This study indicated that both intraspecific and interspecific variation play critical roles in adjusting leaf ecological stoichiometry to increase the resilience and tolerance of the community to environmental change in the alpine-gorge region on the eastern Qinghai-Tibetan Plateau.

We analyzed multidimensional biodiversity(including species diversity,functional diversity,and phylo-genetic diversity)of needle-broadleaf mixed forests of Abies fargesii var.faxoniana-Betula spp.and needleleaf for-ests of A.fargesii var.faxoniana in the subalpine regions of eastern edge of Qinghai-Tibet Plateau.We measured leaf functional traits including leaf area,leaf thickness,leaf dry matter content,and specific leaf area.The results showed that leaf thickness(0.28 mm)and leaf dry matter content(319.86 mg·g-1)in the needle-broadleaf mixed forests were significantly lower than in the needleleaf forest(0.39 mm and 371.33 mg·g-1,respectively),while specific leaf area(192.74 cm2·g-1)was significantly higher(100.91 cm2·g-1).Leaf area showed no significant difference between the two forest communities(27.88 and 26.63 cm2,respectively).The phylogenetic signals of all leaf functional traits were significant,except for leaf thickness.The phylogenetic structure of the needle-broadleaf mixed forests and needleleaf forest communities tended toward divergence.Shannon diversity index,Simpson diver-sity index,species richness,functional richness,functional dispersion,Rao's quadratic entropy,and phylogenetic diversity in the needle-broadleaf mixed forests were all significantly higher than in the needleleaf forest,and these indices were significantly positively correlated.Competitive exclusion played a major role in the assembly of subal-pine forest communities,and species diversity,functional diversity,and phylogenetic diversity exhibited synchrony.

Elevational variation in plant growing environment drives diversification of photosynthetic capacity, however, the mechanism behind this reaction is poorly understood. We measured leaf gas exchange, chlorophyll fluorescence, anatomical characteristics, and biochemical traits of Salvia przewalskii at elevations ranging from 2400 m to 3400 m above sea level (a.s.l) on the eastern Qinghai-Tibetan Plateau, China. We found that photosynthetic capacity showed an initial increase and then a decrease with rising elevation, and the best state observed at 2800 m a.s.l. Environmental factors indirectly regulated photosynthetic capacity by affecting stomatal conductance (gs), mesophyll conductance (gm), maximum velocity of carboxylation (Vc max), and maximum capacity for photosynthetic electron transport (Jmax). The average temperature (T) and total precipitation (P) during the growing season had the highest contribution to the variation of photosynthetic capacity of S. przewalskii in subalpine areas, which were 25% and 24%, respectively. Photosynthetic capacity was mainly affected by diffusional limitations (71%-89%), and mesophyll limitation (lm) played a leading role. The variation of gm was attributed to the effects of environmental factors on the volume fraction of intercellular air space (fias), the thickness of cell wall (Tcw), the surface of mesophyll cells and chloroplasts exposed to intercellular airspace (Sm, Sc), and plasma membrane intrinsic protein (PIPs, PIP1, PIP2), independent of carbonic anhydrase (CA). Optimization of leaf tissue structure and adaptive physiological responses enabled plants to efficiently cope with variable climate conditions of high-elevation areas, and the while maintaining high levels of carbon assimilation.

Nitrogen (N) deposition has changed plants and soil microbes remarkably, which deeply alters the structures and functions of terrestrial ecosystems. However, how forest fungal diversity, community compositions, and their potential functions respond to N deposition is still lacking in exploration at a large scale. In this study, we conducted a short-term (4–5 years) experiment of artificial N addition to simulated N deposition in five typical forest ecosystems across eastern China, which includes tropical montane rainforest, subtropical evergreen broadleaved forest, temperate deciduous broadleaved forest, temperate broadleaved and conifer mixed forest, and boreal forest along a latitudinal gradient from tropical to cold temperature zones. Fungal compositions were identified using high-throughput sequencing at the topsoil layer. The results showed that fungal diversity and fungal community compositions among forests varied apparently for both unfertilized and fertilized soils. Generally, soil fungal diversity, communities, and their potential functions responded sluggishly to short-term N addition, whereas the fungal Shannon index was increased in the tropical forest. In addition, environmental heterogeneity explained most of the variation among fungal communities along the latitudinal gradient. Specifically, soil C: N ratio and soil water content were the most important factors driving fungal diversity, whereas mean annual temperature and microbial nutrient limitation mainly shaped fungal community structure and functional compositions. Topsoil fungal communities in eastern forest ecosystems in China were more sensitive to environmental heterogeneity rather than short-term N addition. Our study further emphasized the importance of simultaneously evaluating soil fungal communities in different forest types in response to atmospheric N deposition.

Interactions between soil fungi and soil environmental factors regulate soil nitrogen (N) mineralization rates on the eastern Qinghai-Tibetan Plateau. Some studies have also illuminated differences in soil N mineralization rate based on different mycorrhizal forests, but the associated effect of soil fungal functional guilds and soil environmental factors underlying this process are not well-understood. Three primary forests respectively dominated by Abies fargesii var. faxoniana (ectomycorrhizal, EcM), Cupressus chengiana (arbuscular mycorrhizal, AM) and Rhododendron phaeochrysum (ericoid mycorrhizal, ErM) trees were selected in this area. Meanwhile, soil net N mineralization rate, soil fungal composition and soil enzyme activity among these three mycorrhizal forests were studied. Our results showed that there were significant differences in the seasonal variation of soil net N mineralization rates among three mycorrhizal forests. Soil net N mineralization rate in the AM forest was faster. EcM fungi and saprotroph are the main functional guilds in these three mycorrhizal forests. Meanwhile, the relative abundances of soil fungal functional guilds, soil temperature and soil peroxidase activity could explain 85.0% in the difference of soil net ammonification rate among three mycorrhizal forests. In addition, soil temperature, soil water-filled pore space and soil ammonium content play a central role in controlling the differing soil net nitrification rate among three mycorrhizal forests. Our results suggest differences in soil net mineralization among different mycorrhizal forest types are driven mainly by soil net ammonification. Soil fungal functional guilds and temperature regulate the rate of soil net ammonification by modulating soil peroxidase activity.

Aims Plants and soils are key factors in maintaining ecosystem multifunctionality (EMF). Yet, it remains unclear how climate factors regulate the EMF through soil properties and plant diversity of different plant functional groups in primary dark coniferous forests of subalpine regions. Methods Nine functional indicators related to carbon, nitrogen, phosphorus cycling and plant productivity, four leaf functional traits, mean annual precipitation (MAP) and mean annual temperature (MAT) were collected from 50 primary dark coniferous forests in ten sites on the eastern Qinghai-Tibetan Plateau. The EMF was calculated using two approaches. The averaging approach involves converting and averaging the functional indicators, and the multiple threshold approach quantifies the number of functions across different thresholds. Results MAP promoted EMF. Soil water content and shrub species richness had a significant positive effect on EMF, whereas herb species richness had a negative effect. Functional diversity and specific leaf area of tree species rather than richness had a significant positive effect on EMF, indicating the increase in functional traits was beneficial to EMF. Climatic factors could directly or indirectly affect EMF through species richness, functional diversity, and soil abiotic factors. Conclusions The effects of species richness on EMF varied among different plant functional groups, possibly related to different mechanisms, and highlighted the role of functional diversity in maintaining EMF. Spatial variation in climate could modify soil properties and plant diversity, further affecting EMF in primary dark coniferous forests. Hence, these findings should be considered in future predictions of how a changing climate could affect EMF.

Exploring the resource limitation of soil microbial metabolism is essential to understand ecosystem functions and processes. However, the spatially divergent patterns and drivers of soil microbial nutrient limitation cha-racteristics in montane ecosystems at small scales, especially at the slope aspect scale, are still unclear. In this study, we measured soil enzyme activities involved in carbon (C), nitrogen (N) and phosphorus (P) cycle and quantified the microbial nutrient limitations by enzyme stoichiometry in two representative mountain sites in subalpine region of western Sichuan, including the sunny and shady slopes with different vegetation types (shrubland and forest, respectively) in Miyaluo of Lixian County, and with the same vegetation type (shrubland) in Yakexia of Heishui County. The results showed that soil enzyme activities and their stoichiometric ratios were significantly different between slope aspects in Miyaluo, while the differences were not significant in Yakexia. The stoichiometry ratio of C-, N- and P-acquiring enzymes on the sunny slope of Miyaluo was 1:0.96:0.92, approaching the 1:1:1 ratio at the global scale, but deviated from 1:1:1 on the shady slope of Miyaluo (1:1.39:0.75) and the different slopes of Yakexia (1:1.09:1.35). There was no significant difference in vector length between slope aspects at both sites, indicating no significant effect of slope aspect on the microbial C limitation. The vector angle was significantly higher on the sunny slope (43.6°) than that on the shady slope (28.7°) in Miyaluo, suggesting that the microorganisms were mainly N-limited. Partial least squares path model showed that the vector angle was mainly directly influenced by the soil nutrient ratios. The vector angle ranged from 50.3° to 51.4°, and did not differ between slope aspects in Yakexia. Therefore, differences in vegetation types between slope aspects drove variations in soil enzyme activity and microbial nutrient limitation through soil properties. It would provide a scientific basis for predicting the spatial pattern of soil enzyme activity and microbial nutrient limitation.

Leaf traits are important indicators of plant life history and may vary according to plant functional type (PFT) and environmental conditions. In this study, we sampled woody plants from three PFTs (e.g., needle-leaved evergreens, NE; broad-leaved evergreens, BE; broad-leaved deciduous, BD) on the eastern Qinghai-Tibetan Plateau, and 110 species were collected across 50 sites. Here, the divergence and correlations of leaf traits in three PFTs and relationships between leaf traits and environment were studied. The results showed significant differences in leaf traits among three PFTs, with NE plants showed higher values than BE plants and BD plants for leaf thickness (LT), leaf dry matter content (LDMC), leaf dry mass per area (LMA), carbon: nitrogen ratio (C/N), and nitrogen content per unit area (Narea), except for nitrogen content per unit mass (Nmass). Although the correlations between leaf traits were similar across three PFTs, NE plants differed from BE plants and BD plants in the relationship between C/N and Narea. Compared with the mean annual precipitation (MAP), the mean annual temperature (MAT) was the main environmental factor that caused the difference in leaf traits among three PFTs. NE plants had a more conservative approach to survival compared to BE plants and BD plants. This study shed light on the regional-scale variation in leaf traits and the relationships among leaf traits, PFT, and environment. These findings have important implications for the development of regional-scale dynamic vegetation models and for understanding how plants respond and adapt to environmental change.

[目的]研究川西亚高山不同森林恢复方式对土壤团聚体稳定性的影响,为退化森林的适应性恢复和可持续经营提供科学依据.[方法]选取川西亚高山不同恢复方式下的 3种森林类型,即岷江冷杉-红桦次生林(自然恢复,SF)、云杉阔叶混交林(人工种植后自然恢复,MF)和云杉人工林(人工恢复,PF),采用干筛法测定了 6个粒级(＞5、2～5、1～2、0.5～1、0.25～0.5和＜0.25 mm)土壤团聚体的分布特征,计算平均重量直径(MWD)、几何平均直径(GMD)、大于 0.25 mm团聚体含量(R＞0.25)和土壤可蚀性因子(K)等团聚体稳定性参数,探究不同森林恢复方式对土壤团聚体稳定性的影响.[结果]研究发现,SF和MF的团聚体分布以＞2 mm团聚体为优势粒级,而PF的团聚体在各粒级分布较均匀.不同恢复方式对土壤团聚体稳定性参数(MWD、R＞0.25、K)影响差异显著(P＜0.05),其中SF和MF的土壤MWD和R＞0.25 均高于PF,而土壤可蚀性因子K低于PF.不同恢复方式的土壤团聚体稳定性与土壤有机碳、全氮含量和碳氮比及细根周转率显著相关,且细根周转率能解释超30%的土壤团聚体稳定性变异,说明森林恢复方式对土壤团聚体稳定性的影响与土壤有机质的周转过程密切相关.[结论]主要受不同森林的细根周转差异对土壤有机碳输入的影响,自然恢复形成的混交林较人工种植的针叶纯林更有利于土壤团聚体的稳定.因此,在川西亚高山地区退化森林恢复中,宜采用自然恢复或营建混交林的方式,有利于土壤结构的稳定.

Soil microbial community composition and extracellular enzyme activity are two main drivers of biogeochemical cycling. Knowledge about their elevational patterns is of great importance for predicting ecosystem functioning in response to climate change. Nevertheless, there is no consensus on how soil microbial community composition and extracellular enzyme activity vary with elevation, and little is known about their elevational variations on the eastern Qinghai-Tibetan Plateau, a region sensitive to global change. We therefore investigated the soil microbial community composition using phospholipid fatty acids (PLFAs) analysis, and enzyme activities at 2,820 m (coniferous and broadleaved mixed forest), 3,160 m (dark coniferous forest), 3,420 m (alpine dwarf forest), and 4,280 m (alpine shrubland) above sea level. Our results showed that soil microbial community composition and extracellular enzyme activities changed significantly along the elevational gradient. Biomass of total microbes, bacteria, and arbuscular mycorrhizal fungi at the highest elevation were the significantly lowest among the four elevations. In contrast, extracellular enzyme activities involved in carbon (C)-, nitrogen (N)-, and phosphorus (P)- acquiring exhibited the maximum values at the highest elevation. Total nutrients and available nutrients, especially P availability jointly explained the elevational pattern of soil microbial community, while the elevational variation of extracellular enzyme activities was dependent on total nutrients. Microbial metabolism was mainly C- and P-limited with an increasing C limitation but a decreasing P limitation along the elevational gradient, which was related significantly to mean annual temperature and total P. These results indicated a vital role of soil P in driving the elevational patterns of soil microbial community and metabolism. Overall, the study highlighted the contrasting responses of soil microbial biomass and extracellular enzyme activities to elevation, possibly suggesting the differences in adaption strategy between population growth and resource acquisition responding to elevation. The results provide essential information for understanding and predicting the response of belowground community and function to climate change on the eastern Qinghai-Tibetan Plateau.