Predicting the growth and maximum biomass (M max) of woody plant communities (WPCs) remains a central challenge in terrestrial ecology due to the complex and heterogeneous nature of tree growth. While metabolic scaling theory (MST) provides a valuable conceptual framework, it remains limited in its ability to fully explain community-level growth or carbon dynamics. To address this limitation, we developed an iterative growth model for forests (IGMF), built upon an iterative growth framework grounded in MST's core principles and further incorporating the self-thinning effect. The IGMF and its extensions suggest that community-level growth, net primary productivity (NPP), and other key components of the carbon budget-including gross primary productivity, autotrophic respiration, organ turnover, and non-structural carbohydrate storage-may be approximated as functions of current biomass, biomass-specific maintenance respiration, stand age, or M max. These relationships provide a basis for estimating the global M max of WPCs during 2018-2020 at approximately 1440 +/- 26 Pg (1 Pg = 1 & times; 1015 g), with an additional biomass potential of about 510 Pg under current conditions. However, machine learning projections suggest that this potential may decline by up to 246 Pg by 2100, primarily within evergreen broadleaf forests. Our analyses also indicate that species richness, by promoting functional convergence, can amplify the negative effects of temperature and precipitation seasonality on M max. In contrast, warming in the Northern Hemisphere may favor M max accumulation in open shrublands. Together, these results help to clarify the growth dynamics of WPCs and suggest a possible shift in the major contributors to terrestrial carbon sequestration-from forests to shrublands-under future climate scenarios.

Multiple studies have revealed that soil organic carbon (SOC) continues to accumulate as forests age, old-growth forests had higher SOC content. Microbial carbon use efficiency (CUE) and its accurate assessment is crucial for understanding C cycling. Most previous studies were based on a single approach, which limits our ability to cross-compare CUE across studies and fully utilize the complementary information gained. However, whether the response of microbial CUE to environmental change and the relationship with SOC follows a consistent trend under different methods remain unclear. Therefore, we explore microbial CUE in long‐term subalpine forests (middle-aged and old-growth forests, MF and OF) under three approaches and evaluated how microbial CUE response to forest age and soil layer and how it relates to SOC. The choice of methods significantly affected microbial CUE, with mean value was 13C (0.60) > 18O (0.38) > SM (0.26). Irrespective of methods, the microbial CUE in OF is higher than in MF and it declined with soil depth. Microbial CUE increased from MF to OF by 8.1

How co-existing species of canopy trees and understory shrubs differentially respond to global warming may affect treeline ecotone dynamics, yet their growth trends and potential underlying ecophysiological mechanisms remain understudied. Here, we used dendrochronology and stable carbon isotope analysis to compare the stem radial growth, intrinsic water-use efficiency (iWUE) and climate sensitivity of co-occurring coniferous trees (Abies fabri Craib) and broadleaved shrubs (Rhododendron faberi subsp. prattiiradial) at a treeline ecotone site in the southeast Tibetan Plateau. The results revealed that the shrub's growth rate has increased significantly over the past 50 years (1973-2022) (P < 0.05), while the growth trend of co-existing trees did not increase significantly. Furthermore, compared with nearby trees, the radial growth of shrubs was more strongly positive correlated with temperature and moisture conditions during the growing season (May-October). Nonetheless, during the more recent 1990-2022 period, iWUE of both woody plant species steadily increased with a rising atmospheric CO2 concentration. Overall, our results suggest that at the treeline ecotone, morphological growth and functional trait differences between coniferous trees and broadleaved shrubs, as well as interactions within and between species, may drive divergent plant physiological processes and ecological strategies in response to rapid global warming.

Individual trees in natural forests often exhibit complex, inconsistent and variable growth trajectories influenced by genetics, climate change and uneven stand structure. These growth divergences pose a challenge in predicting the overall growth trend of trees at the aggregate level. Here, we propose a radius‐driven metabolic growth model (iterative growth model at the tree‐ring, IGMR) to explain the radial growth of trees. The IGMR suggests that the best radial growth trajectory (BGT) at the aggregate level varies within a predictable range and can be derived from the maximum radius and total growth time of an individual tree. Analyses based on a global database confirmed the applicability of the IGMR and found that the average radial growth trend closely follows half of the BGT, with the strength of this association potentially related to functional trait trade‐offs. Further analyses show that climate change and uneven stand structure may cause the overall growth trajectory to undergo more drifts (changes in growth rate only) than adaptations (changes in maximum size). Synthesis : Our results reveal not only a convergent growth trajectory in tree size (or radius) at the aggregate level, but also suggest that climate regulates the tree growth–climate relationship by influencing the height (i.e. maximum radial growth rate) of this unimodal trajectory, whereas the length (i.e. with maximum tree radius) of the trajectory shows greater dependence on species. These findings further imply that climate change is more likely to affect the forest's maximum carbon sequestration capacity through shifts in community composition, rather than through direct changes in individual tree growth rates.

Anthropogenic warming is predicted to alter ecological boundaries in energy-limited shrub ecosystems. Yet we still lack a sound understanding of the structural changes that shrub ecosystems are undergoing on a global scale and the factors driving them. To that end, here we collected studies of shrub dynamics from 227 sites worldwide to conduct a quantitative review, including the rate of advancing shrubline (their upslope shift), the rates of shrub cover and recruitment changes. Our results revealed that shrub expanded (e.g. shrubline shifts, shrub cover and recruitment increase) at the vast majority of sites (84 %); in contrast, they remained stable in 10 % of sites and descended at just 6 % of them. The mean global shift rate of shrubline was 1.22 m/year, being significantly faster in subarctic (> 60°N) than temperate (< 60°N) regions, and likewise more quickly in wet (total annual precipitation >400 mm) than dry (total annual precipitation <400 mm) areas; the annual change rates of shrub cover and recruitment increased by 0.89 % and 2.02 %. Shrubs communities have expanded rapidly in response to ongoing climate warming. The combination of autumn precipitation and winter temperature largely contributed to the general shift rates of shrubline, while the shrub cover and recruitment were mainly affected by summer temperature and precipitation in both spring and autumn. Furthermore, the site-specific pace of their expansion probably depends on a combination of local climatic and non-climatic drivers (such as fine-scale environmental conditions, disturbance, their interactions, and dispersal limitation). The increase of shrub distribution may alter the function and albedo of the ecosystems at high-latitude and -elevation regions, resulting in the feedback on climate.

It is widely accepted that old-aged forest can accumulate soil organic carbon (SOC). How microbial physiological traits respond to forest age and whether they drive SOC sequestration in old-aged forest remain elusive. Therefore, we compared the microbial C use efficiency (CUE), biomass turnover rate (rB), microbial biomass C (MBC) and necromass C (MNC) across soil profiles from middle and old-aged forest and evaluated how these microbial traits are related to SOC storage. The results revealed that both forests could accumulate SOC and old-aged forest supported higher SOC storage than middle-aged forest from 2005 to 2020. Moreover, SOC was concentrated on the surface soils of middle-aged forest, whereas it was more distributed across the deeper soil profile in old-aged forest. Compared with middle-aged forest, the O, A and B soil layers of old-aged forest presented increases in microbial CUE (17.8

[Background] Water conservation is one of the important services of the ecosystem, it is closely related to vegetation type and its coverage, litter composition and its quantity, soil layer thickness and soil physical properties, and is a result of the synergistic action of vegetation and soil. But there is no unified standard method to assess its capabilities, and the quantified results of the different methods vary greatly. [Methods] Therefore, taking the Miyaluo forest area of western Sichuan as an example, the total water conservation volume were determined by measuring and calculating the aboveground water retention capacity of typical vegetation and the different porosity constants of its soil. The water conservation capacity of vegetation was determined by water immersion, and the soil porosity constants were determined by soil core samples. [Results] Results showed that the aboveground water conservation capacity of mixed forest was the maximum with the amount of over 100 t/hm~2, and then the rank order of the capacity was artificial forest＞alpine rhododendron shrub forest＞birch forest＞coniferous forest＞meadow＞ alpine oak shrub forest ＞ alpine willow shrub forest, which indicates that increasing biodiversity can improve water conservation capacity. The rank order of soil total porosity of different vegetation was coniferous forest＞ birch forest ＞ meadows ＞ alpine rhododendron shrub forest ＞ artificial forest ＞ alpine willow shrub forest ＞ alpine oak shrub forest ＞ mixed forest. The water conservation capacity within the soils in the study area accounted for more than 90% of the total water conservation capacity, which was consistent with the results of the existing studies. The rank order of soil dehydration rate of different vegetation types was arbor forest＞ shrub forest＞ meadows. The difference of soil total porosity was not obvious under different vegetation, but the porosity of capillary and non-capillary were significantly different; the volume of aboveground water conservation of vegetation + water quantity of soil total porosity were not significantly different among various vegetation types, and coniferous and birch forest had the maximum, while mingled forest had the minimum; the volume of aboveground water conservation of vegetation+water quantity of soil non-capillary porosity were significantly different among various vegetation types, and coniferous-forest had the maximum, while meadow had the minimum; but there was opposite trend for the volume of aboveground water conservation of vegetation + water quantity of soil capillary, which was in accord with the results of InVEST model. [Conculsions] The current study suggests that the volume of aboveground water conservation of vegetation in vegetation system + water quantity of its soil capillary porosity is scientific and accurate for assessment the water-holding function of the ecosystem, and improving soil water conservation capacity is the key to enhance the water holding capacity of vegetation system.

Bauhinia faberi via.Microphylla(BFM)is an important tree species for vegetation restoration in the dry valley of southwestern China.However,there were few studies on the application of arbuscular mycorrhizal fungi(AMF)in improving the drought adaptation of BFM.In order to investigate the response of BFM to water stress(WS),we tested four inoculation treatments((no AMF,Control),Glomus mosseae(GM),Glomus intraradices(GI),Glomus mosseae+Glomus intraradices(GMI))in pots,experimented under three field water holding capacity(WHC)of 70％,50％and 30％.The changes of seedling survival rate(SR),AMF relative root length colonization rate(Col),growth,photosynthetic parameters,water status and leaf nutrients were examined.The results showed that under 30％WHC drought conditions,SR with dual inoculation of AMF was not higher than with single inoculation of GM,suggesting that increasing the diversity of AMF did not definitely improve plant SR,and that the species of inoculated AMF might have an important impact on SR.The sensitivity of dual inoculated Col to water stress was lower than that of single inoculation,which was more favorable for dual inoculated BFM seedlings adapting to drought environment.The overall drought resistance ability(D)also showed that dual inoculation of AMF improved plant drought adaptation compared with single inoculation,which was related to the higher Col of dual inoculated AMF.This study is of practical importance to promote vegetation restoration in arid areas in a cost-effective and environmentally friendly manner.

中国是世界山地大国，山地面积约为陆地国土面积的 2/3。近 10 年来，山地林草植被覆盖率增加8.2%，山地绿色覆盖指数均值达到 82.1%，植被覆盖率达到新中国成立以来最高水平，水土流失面积减少27.5×104km2，土壤年侵蚀量减少 27%。目前，中国山地生态安全屏障骨干体系基本形成，高效的山地灾害防控体系不断健全，山地灾害减灾成效显著；与此同时，山区脱贫攻坚战取得历史性胜利，山区产业结构得到显著优化，现代化进程稳步推进。

Soil microbial carbon use efficiency（CUE） is a critical physiological and ecological parameter in measuring soil C cycle and stock under the global change scenarios.It is defined usually as the ratio between carbon（C） allocated to growth and C taken up by microorganisms.It expresses the processes of C retention,turnover,soil mineralization,and greenhouse gas emission.CUE serves as a key regulator of microbial biomass turnover and soil C sequestration.Understanding the variation of soil microbial CUE and its influence mechanism in the context of global environmental change is critical for a better understanding of the partitioning of C between microbial biomass,and soil stock potential,and respiration,and the response of long-term C stock in soil to global changes.Soil microbial CUE and its response to environmental changes have received increasing attention from studies on soil carbon cycle,global change ecology,and terrestrial ecosystem models.In this review,it evaluated the advantages and adaptability of five microbial CUE measurement methods including 13 C(or 14 C) and 18 O isotope tracing approaches,calorespirometry,metabolic flux analysis,and stoichiometric modeling;it summarized the dynamic characteristics of soil microbial CUE with ecosystems,vegetation succession and different seasons;it analyzed the effects of the biological and abiotic factors including microbial community composition,substrate quality and nutrient availability,temperature,soil pH,soil moisture,soil aggregates and texture,soil layer depth,and anthropogenic disturbances on soil microbial CUE.According to the overview of CUE,the research prospect should be extended to:（1） Strengthen the soil microbial CUE research of forest ecosystems;（2） Explore the response process and mechanism of soil microbial CUE under the interaction of environmental and biological factors,especially for the effects of root exudates on soil microbial CUE and long-term carbon sequestration under the global changes;（3） Explore the dynamic of soil microbial CUE from microorganism’s ecosystem perspective;（4） Cross-compare CUE estimates by integrating different methods to capture different aspects of microbial metabolism and improve our understanding of processes controlling CUE variability;（5） Analyze dynamics of microbial CUE at the different soil layers and the influence of the CUE temperature sensitivity on long-term carbon stock in soil.

Soil microbial carbon use efficiency (CUE) is a vital physiological parameter in assessing carbon turnover. Yet, how the microbial assemblies with distinct trophic strategies regulate the soil microbial CUE remains elusive. Based on the oligotrophic-copiotrophic framework, we explored the role of microbial taxa with different trophic strategies in mediating microbial CUE (determined by a 13C-labeled approach) along the vegetation primary succession in Hailuogou glacier retreat area of the southeastern Tibetan Plateau. Results showed that soil microbial CUE ranged from 0.54 to 0.72 (averaging 0.62 ± 0.01 across all samples) and increased staggeringly along the vegetation succession. Microbial assemblies with distinct trophic strategies were crucial regulators of soil microbial CUE. Specifically, microbial CUE increased with microbial oligotroph: copiotroph ratios, oligotroph-dominated stage had a higher microbial CUE than copiotroph-dominated ones. The prevalence of oligotrophic members would be the underlying microbial mechanism for the high microbial CUE. Given that oligotrophs predominate in more recalcitrant carbon soils and their higher microbial CUE, we speculate that oligotrophs are likely to potentially enhance carbon sequestration in soils. In addition, the responses of the microbial CUE to fungal oligotroph: copiotroph ratios were higher than bacterial ones. Fungal taxa may play a dominant role in shaping microbial CUE relative to bacterial members. Overall, our results constructed close associations between microbial trophic strategies and CUE and provide direct evidence regarding how microbial trophic strategies regulate microbial CUE. This study is a significant step forward for elucidating the physiological mechanisms regulating microbial CUE and has significant implications for understanding microbial-mediated carbon cycling processes.

西南林区是我国第二大林区,也是我国25个生物多样性关键地区和全球生物多样性保护的热点地区之一,还是我国重要的水源涵养地和物种基因库,构建西南地区生态安全屏障,可为我国西南地区长江经济带发展战略、生态保护与修复等国家战略推进提供生态安全保障.本文论述了西南林区森林生态系统的特殊性和重要生态地位,综合分析了西南地区森林资源质量、水土流失、土地沙化、自然灾害等方面的现状与存在问题.从西南林区生态保护与修复建设目标、碳达峰碳中和任务和绿色低碳生产生活战略、防灾减灾能力与社会经济可持续发展、人民日益增长的物质与文化生活等方面,论述了建设生态安全屏障的必要性.从防护林体系科学合理的规划和总体布局、现有林保护与修复、低效林结构调整与功能提升、干热干旱河谷区植被恢复与重建等方面,提出了构建西南林区生态安全屏障的途径和生态对策,为西南地区森林生态系统多功能经营、生态系统管理、天然林保护与修复、生态安全屏障建设等提供参考.

Nitrogen (N) deposition increased forest carbon (C) sink significantly, hence exploring the microscopic mechanisms is critical to predicting future global ecosystem C cycle, especially the effects of enhanced N deposition on soil microbial carbon use efficiency (CUE), which still unclear. We evaluated the responses of soil microbial CUE to long-term (5 years) N addition in an evergreen broad-leaved forest and a mature coniferous forest by using a 13C isotope tracing method. The results showed that the soil microbial CUE ranged from 0.38 to 0.51, which was smaller than the results obtained from the previous studies based the same method and forest type. In evergreen broad-leaved forest, the microbial CUE had no significant changes in the low N-addition treatment, but it was increased by 9.23

[Objective] The changing trend of water-holding function in a subalpine area of Western Sichuan Province was analyzed in order to provide a scientific basis for defining the dynamic characteristics of water conservation in this area. [Methods] Taking the Zagunao River basin in the upper reaches of the Minjiang River as an example, the variation characteristics of water conservation capacity of the Zagunao River basin were studied based on precipitation, temperature, water, and sediment data collected at the outlet of the Zagunao River basin and by using the principle of water balance. [Results] ① Runoff was significantly reduced over time, with an average annual decrease of 2.83 mm (i.e., water-holding capacity increased by 28.3 t/ha annually), especially around year 2000 (when the ecological protection and ecological restoration project started) to 2020 when the average annual decrease was 3.12 mm (i.e., water-holding capacity increased by 31.2 t/ha annually); ② Sand content in the runoff also showed a significant decreasing trend, indicating that runoff in the area was decreasing while soil conservation capacity was increasing; ③ There was no significant fluctuation trend in precipitation over the study period, indicating that the observed runoff decrease was not caused by precipitation changes. [Conclusion] Ecological engineering, such as ecological protection and restoration, plays an obvious role in promoting water conservation.

为了解大渡河中游干暖河谷植物群落的稳定程度,促进川西干暖植被恢复与重建,采用方差比率法(VR)、x2检验统计、Person相关性分析、Spearman秩相关分析与M.Godron稳定性测度方法,分析大渡河中游干暖河谷植被种间关系与群落稳定性.结果表明:大渡河中游干暖河谷典型植物群落物种的种间总体关联性表现为不显著正关联,物种间存在的各种作用及相互依赖和相互竞争不强,植物更倾向于以少数几种物种组成的植物群落生长方式进行演替,正联结是该区域重要的种间关系之一,这与物种对环境的长期适应而形成稳定的生态系统类型和相同或者相似的适应策略有关.成对物种种间关系中,包含乔木的种对相关性显著的种对数量多,且仅表现为正相关,该区域植物具有植物群落正向演替的基础.M.Godron稳定性测度法得到的测量曲线与经过(0,100)、(100,0)的线段交点处坐标为(38.12,61.85),距离稳定点(20,80)距离为25.65.本研究表明群落依然处于不稳定状态,具有低阈值生态安全和高风险生态退化的特点,应从自然和人工植被恢复等途径提高植被覆盖率,促进植物群落正向演替.

川西亚高山原始针叶林遭受大规模采伐后自然恢复形成的次生林已成为该区域的主要森林类型之一,具有重要的生态功能.现有森林生态功能评价大多为水源涵养等单一生态功能,尚缺乏针对多种生态功能的综合评价.采用空间代替时间的方法,以岷江冷杉原始林为参照,基于植物群落学与生物量调查,以及植物和土壤样品采集与测定,分析次生林植物多样性、碳储量、林地涵水能力三大生态功能恢复动态,探讨次生林生态功能恢复速率及其影响因素.结果显示:(1)随着次生林的恢复,林分综合生态功能显著提高,生态功能指数为原始暗针叶林(0.823 6)＞针阔叶混交林(0.5464)＞阔叶林(0.367 7).川西亚高山次生林生态功能恢复大约需要180年以上,不同生态功能恢复速率为植物多样性功能＞林地水源涵养功能＞固碳功能,不同演替阶段为阔叶林＞针阔叶混交林＞原始暗针叶林;(2)恢复到50-60年阔叶林具有较高的物种丰富度、Simpson和Shannon-Wiener指数,尤其是物种丰富度恢复速率较快,但恢复到老龄林相似的冠层物种组成需要较长的时间,可能与砍伐前为原始森林、残余森林呈镶嵌分布,以及桦木和岷江冷杉等建群种周转率低等有关;(3)林地持水能力以针阔混交林为最高,其中土壤蓄水量占绝对优势,针阔混交林具有较高的土壤毛管持水量,而针叶林土壤非毛管持水量较高.恢复速率为土壤毛管持水量(110年)＞枯落物持水量(118年)＞苔藓层持水量(135年);(4)随着林龄的增加,地上植被层和土壤碳储量显著增加,土壤层碳储量显著大于植被层,恢复速率为土壤(110年)＞地上部分(160年)＞枯落物层和苔藓层(＞200年),较快的土壤碳储存以及毛管持水量恢复速率与先前地上植被遭受严重破坏而地下土壤干扰较轻有关.本研究表明川西亚高山次生林生态功能恢复是一个漫长的过程,不同恢复阶段、不同生态功能恢复速率差异显著,应针对不同演替阶段采取不同的生态功能恢复策略,尤其要加强现有原始老龄林栖息地和残余老树的保护,注重构建针阔叶混交林结构,保护和促进次生林地被物层的恢复.

Organism growth underlies numerous ecological processes. However, existing growth models from the von Bertalanffy family do not consider variable growth states (e.g., changes in resource uptake) and/or non-instantaneous changes in the growth rate of an organism along its size gradient. To address the above two points, we derived an iterative growth model (IGM) based on the necessary respiration allocation (i.e., maintenance and growth respiration), the intrinsic growth rate of tissue, and the von Bertalanffy paradigm. Some of the model parameters not only reflect the change of growth state, but also maintain a strict relationship with other parameters of biological and/or thermodynamic significance, making the model more basic and flexible. We then tested the basic performance of the IGM and its extension, and found that they are supported by some data, with different orders of magnitude, involving animals and plants. Starting with the IGM, we found that the existing metabolic growth models (e.g., the ontogenetic growth model (OGM) and its extensions) can be characterized as a special form of IGM. Not only that, the IGM also suggests true growth dynamics should have not an explicit analytic solution in most cases and lie somewhere between the Richards and Gompertz equations. Finally, the IGM revealed that the maximum biomass of an organism (M) is determined by organism average growth rate (D/T), maintenance respiration coefficient (mr) and resting metabolism exponent (b). The resulting effect of temperature on M will depend on the sensitivity to the temperature of both D/T and mr. If the former is the more sensitive of the two, M will increase. If not, it will decrease. The IGM displays great potential for the modeling and prediction of plants, endotherms and exotherms.

土壤质量是植被恢复重建的关键.大渡河干暖河谷区植被退化严重,开展土壤质量评价对于制定适合该区域的植被恢复重建措施尤为重要.本文采用最小数据集法,评价大渡河干暖河谷区灌丛、草本、针叶林、阔叶林和针阔混交林5种典型植被的土壤质量.基于16个土壤理化指标的主成分分析,构建由土壤毛管孔隙度、非毛管孔隙度、有机质、全氮、全磷、有效磷和速效钾7个指标组成的最小数据集(MDS);根据主成分因子载荷计算MDS指标权重,以毛管孔隙度(18.53％)、全磷(17.36％)、有机质(15.88％)3个指标权重为较大.基于MDS的土壤质量指数依次为:灌丛(0.558)＞草地(0.482)＞阔叶林(0.392)＞针阔混交林(0.387)＞针叶林(0.357),土壤肥力评分法进一步验证该评价结果.土壤质量指数分级表明,灌丛和草地以土壤质量等级较高的Ⅲ、Ⅳ级样地为主,而其余3个植被类型以等级较低的Ⅰ、Ⅱ级样地为主.大渡河干暖河谷灌丛具有较好的土壤改良效果,是今后大渡河干暖河谷区植被恢复重建的主要方向;草地土壤质量亦较好,具有较大的植被恢复潜力.