Size Inequality Research Articles

Shoot facilitation contributes more than root facilitation to plant size inequality under environmental stress: theoretical insights from a two-layer zone-of-influence model

Shoot facilitation contributes more than root facilitation to plant size inequality under environmental stress: theoretical insights from a two-layer zone-of-influence model

Experimental evidence of inbreeding depression for competitive ability and its population-level consequences in a mixed-mating plant.

Inbreeding depression is a key factor regulating the evolution of self-fertilization in plants. Despite predictions that inbreeding depression should evolve with selfing rates as deleterious alleles are increasingly exposed and removed by selection, evidence of purging the genetic load in wild populations is equivocal at best. This discordance could be explained, in part, if the load underlying inbreeding depression is subject to soft selection, i.e., the fitness of selfed individuals depends on the frequency and density of selfed vs. outcrossed individuals in the population. Somewhat counterintuitively, this means that populations with contrasting mutation load can have similar fitness. Soft selection against selfed individuals may be expected when there is inbreeding depression for competitive ability in density-regulated populations. We tested population-level predictions of inbreeding depression in competitive ability by creating a density series of potted plants consisting of either purely outcrossed, purely selfed, or mixed (50% outcrossed, 50% selfed) seed of the mixed-matingbiennial Sabatia angularis (Gentianaceae) representing ecological neighborhoods. Focusing on the growth and survival of juveniles, we show that mean plant size is independent of neighborhood composition when resources are limiting, but greatest in outcrossed neighborhoods at low densities. Across a range of densities, this manifests as stronger density-dependence in outcrossed populations compared to selfed or mixed ones. We also found significantly greater size inequalities among individuals in mixed neighborhoods, even at high densities where mean juvenile size converged, a key signature of asymmetric competition between outcrossed and selfed individuals. Our work illustrates how soft selection could shelter the genetic load underlying inbreeding depression and its demographic consequences.

Plant size inequality: How to analyse competing spatial dissimilarity indices?

Worldwide biodiversity loss is perceived as a major threat and is likely to be enforced by ongoing climate change. Continued monitoring of biodiversity can assist in compensating for decreasing biodiversity by goal-oriented conservation management. Plant size diversity, also termed size inequality and size hierarchy, has often been neglected in studies of biodiversity, but plays a crucial role in many ecosystems, e.g. in forests. Several competing diversity indices and other characteristics of spatial plant size inequality have been proposed but to date no protocols or guidelines exist for evaluating their relative merits. In our study, we proposed a broad framework for such an analysis. In order to put this framework to a test, we revisited the dissimilarity coefficient, a somewhat ignored but promising spatial size inequality index published at the end of the 1990s, identified its nearest index competitors and analysed their performances in different mathematical-statistical contexts. We learned that the dissimilarity coefficient is more sensitive in statistical significance tests relating to three very different summary characteristics than its closest competitor, the size differentiation index. In addition the dissimilarity coefficient has a more solid foundation than the differentiation index, since it is based on the well-known coefficient of variation. The dissimilarity coefficient can be recommended in a wide range of plant diversity applications. The principle of the dissimilarity coefficient can also be used to define an effective mark correlation function. We recommend our evaluation framework for use in similar analyses of competing diversity characteristics.

Market power and labour market inequality

Abstract I discuss how firms contribute to inequality in the UK as laid out in the article in this collection by De Loecker, Obermeier and Van Reenen. As in other economies around the world, the UK has seen a rise in market power since 1980 leading to an increase in inequality of firm sizes. While firm inequality per se is not harmful, when it is driven by market power, it does have major implications for the labour market. This commentary examines the effect of the firm size distribution and market power on the labour share, declining labour dynamism and wage inequality. I also outline policy responses that reduce inequality and increase economy-wide well-being.

Inequality Among Agricultural Households in Rural Punjab: The Effect of Income Sources

This study examined income inequality among agricultural households in Punjab using primary data collected during the agricultural year 2020-21. The study employed the Gini coefficient and Theil index to measure and decompose income inequality. The results indicated that agricultural household's involvement in off-farm and ad-hoc sources increased with their income level. Crop cultivation contributed the highest to total income inequality due to its dominance in household income. Still, it had an inequality-decreasing effect in marginal, small, semi-medium, and medium-category households. Livestock income was also identified as a potential tool for reducing inequality, especially in the south-western zone of the state. However, the off-farm income sources were inequality enhancing, likely due to disparities in skills and education required for engaging in such activities compared to agricultural activities. The Theil index revealed that intra-zonal and intra-landholding size inequality were the main contributors to overall inequality. These results indicated that there was a need for targeted policy interventions to enhance the livestock sector, promote income diversification, and address intra-zonal and intra-landholding disparities to promote inclusive and equitable development in Punjab's agricultural sector.

Abstract 53: T-cell receptor repertoire changes associated with clinical response in patients with B-cell non-Hodgkin’s lymphoma receiving CD19 CAR-T therapy

Abstract Background: Although CAR T-cell therapy has achieved remarkable response rates in adult patients (pts) with relapsed and refractory B-cell non-Hodgkin’s lymphoma (NHL), 20-30% of pts still have primary refractory disease, and 30-40% of pts relapse, often within 6 months of therapy. Given that durable clinical response can be achieved without CAR T cell persistence, we hypothesized that durable remission is correlated with the expansion of tumor-reactive T-cell receptor (TCR) clones following CAR T-cell infusion. To assess this, we examined the TCR repertoire of adult pts with B-NHL who received CD19 CAR T-cell (axi-cel) therapy to identify correlates of clinical response. Methods: Single-cell (sc) RNA sequencing (seq) and scTCR-seq were performed on peripheral blood mononuclear cells from B-NHL pts before lymphodepletion chemotherapy (pre), at peak CAR-T expansion (peak), and one month following CAR-T (M1). scRNAseq and scTCR-seq data were processed using CellRanger v7.0.1, which were then analyzed using Immunarch (v0.9.0) for TCR clonality and sample diversity. Diversity was assessed using the Gini coefficient to indicate clone size inequality (0 = maximum diversity). TCR diversity and phenotype of expanded and emerged TCR clones post CAR-T were compared across clinical response categories: CR (complete remission for at least 6 months), PD1 (primary refractory), and PD2 (relapsed after partial or complete response). Results: We analyzed 107,035 T cells from 77 serial samples of 32 pts (16 CR, 4 PD1, 12 PD2) and 5 healthy controls. Compared to pts with PD1 and PD2, pts with CR had a larger Gini coefficient for TCR clones at M1 relative to Pre and Peak. The Gini coefficient was the largest for tumor recirculating CD8 T effector memory (Tem) and activated CD8 peripheral memory (Tpm) cells at M1 for pts with CR. Examining the repertoire of emerged and expanded TCR clones at Peak and M1 from Pre, pts with PD2, compared to pts with CR, had a higher percentage of activated CD8 T peripheral memory (Tpm) and T regulatory cells (Treg) among the emerged clones and activated CD8 Tpm among the expanded clones. Patients with PD1, relative to patients with CR, had more proliferating and non-activated CD8 Tpm among the expanded and emerged clones. Conclusion: NHL pts with CR after CAR-T had more robust clonal expansion of T cells, particularly tumor recirculating CD8 Tem and activated CD8 Tpm, compared to pts with relapsed or refractory disease. In contrast, pts with relapsed or refractory disease had an expansion of TCR clones with a larger proportion of CD8 Tpm and Tregs. Endogenous tumor-reactive TCR expansion may help predict favorable clinical response following CAR T-cell therapy. Citation Format: Aiman J. Faruqi, Panwen Wang, Radhika Bansal, Andre De Menezes Silva Corraes, Henan Zhang, Zuoyi Shao, Kevin Regan, Eider Moreno Cortes, Arushi Khurana, Nora Bennani, Yucai Wang, Paul Hampel, Jonas Paludo, Patrick Johnston, Hemant Murthy, Madiha Iqbal, Stephen Ansell, Javier Munoz, Allison Rosenthal, Mohamed Kharfan Dabaja, Januario E. Castro, Saad Kenderian, Haidong Dong, Ying Li, Yi Lin. T-cell receptor repertoire changes associated with clinical response in patients with B-cell non-Hodgkin’s lymphoma receiving CD19 CAR-T therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 53.

Biology of Nicotiana glutinosa L., a newly recorded species from an archaeological excavation site in Egypt

BackgroundDuring a field survey of urban flora in Alexandria city in 2019–2022, an interesting species belonging to the Solanaceae was collected from a newly archaeological excavation site and identified as Nicotiana glutinosa L. Many visits were made to the herbaria of Egypt to confirm the species records, but no single record was found. Reviewing the available literature revealed that this tropical American taxon was never recorded in the flora of Egypt.AimsThe present study was focused on N. glutinosa growth structure and plant macro- and micromorphology.MethodsTen sampling sites were covered for N. glutinosa size structure. Plant samples were examined for stem anatomy, leaf, seed, and pollen morphology.ResultsThe species size structure reveals that the individual size index ranges from 1.33 to 150 cm, while its density ranges from 4 to 273 individuals /100 m−2.N. glutinosa has successfully established itself in one of the archaeological sites in Egypt, showing a “healthy” population with a high degree of size inequality, characterized by a relative majority of the juvenile individuals. Voucher specimens were deposited in the Herbarium of Alexandria University (ALEX) Faculty of Science, another specimen is processed to make herbarium specimens at the Herbarium of the Botanic Garden (Heneidy et al. collection, deposition number. 5502).ConclusionsFrom our observations, N. glutinosa seems to have invasive potential, as it shows characteristics shared by most invasive species that are thought to help in their successful establishment in new habitats. This article emphasizes the importance of monitoring and regularly reporting the threats of alien invasive species to avoid any possible negative impacts on indigenous biodiversity in the future.

New indices to balance α-diversity against tree size inequality

The number and composition of species in a community can be quantified with α-diversity indices, including species richness (R), Simpson’s index (D), and the Shannon–Wiener index (H΄). In forest communities, there are large variations in tree size among species and individuals of the same species, which result in differences in ecological processes and ecosystem functions. However, tree size inequality (TSI) has been largely neglected in studies using the available diversity indices. The TSI in the diameter at breast height (DBH) data for each of 999 20 m × 20 m forest census quadrats was quantified using the Gini index (GI), a measure of the inequality of size distribution. The generalized performance equation was used to describe the rotated and right-shifted Lorenz curve of the cumulative proportion of DBH and the cumulative proportion of number of trees per quadrat. We also examined the relationships of α-diversity indices with the GI using correlation tests. The generalized performance equation effectively described the rotated and right-shifted Lorenz curve of DBH distributions, with most root-mean-square errors (990 out of 999 quadrats) being < 0.0030. There were significant positive correlations between each of three α-diversity indices (i.e., R, D, and H') and the GI. Nevertheless, the total abundance of trees in each quadrat did not significantly influence the GI. This means that the TSI increased with increasing species diversity. Thus, two new indices are proposed that can balance α-diversity against the extent of TSI in the community: (1 − GI) × D, and (1 − GI) × H'. These new indices were significantly correlated with the original D and H΄, and did not increase the extent of variation within each group of indices. This study presents a useful tool for quantifying both species diversity and the variation in tree sizes in forest communities, especially in the face of cumulative species loss under global climate change.

Plant functional traits and tree size inequality improved individual tree height prediction of mid-montane humid evergreen broad-leaved forests in southwest China

Tree height and diameter at breast height (DBH) are key survey factors in forest inventory. Compared to measuring DBH, the process of measuring tree height is time-consuming, labor-intensive and costly, especially in natural mixed forests. Tree height is therefore commonly predicted using height-diameter (H-D) models. Nevertheless, developing H-D models for natural mixed forests are hampered by the large diversity of tree species and the small number of rare tree species observed. In this study, a nonlinear mixed effects H-D model was established for a mid-montane humid evergreen broad-leaved forest in southwest China. For this purpose, we classified tree species by K-means clustering according to the specific plant functional traits. Data were collected from 5, 737 trees in 100 subplots with 86 species. The results revealed that the nonlinear mixed effects model of tree height accounted for 75% of the variation in tree height without significant heteroscedasticity, and that the model parameters had biological significance. In the 10-fold cross validation, no clear fluctuation in the model evaluation metrics was observed, indicating the absence of overfitting in the model. Of the 15 stand variables, dominant height (Hd) and Margalef’s index of DBH (DMg), which contributed the most to the height-diameter model, were selected to expand the model. Our findings suggest that tree height increased with increasing values of Hd and DMg, and vice versa. This study highlights the feasibility of categorizing natural mixed forests by utilizing plant functional traits and the influential role of tree size inequality on tree height variation.

Temporal changes in size inequality and stand growth partitioning between tree sizes under various thinning intensities in subtropical Cunninghamia lanceolata plantations

Stand structural complexity and growth partitioning between different tree sizes influence trees competition and resource use efficiency, and thus are closely linked to stand productivity. The main aim of this study was to examine how the stand structure complexity (Gini coefficient Gini) and size-related partitioning of stand growth (growth dominance coefficient GDC and size-growth relationship SGR) temporally changed after different thinning intensities in Chinese fir (Cunninghamia lanceolata) forests, Southeastern China. We analyzed the data of 6 repeated measurements over a nearly 10-year period from a forest thinning experiment with progressively increasing intensity (0, 20%, 25%, 33% and 50% reduction of stand density by selection logging of releasing target trees) and assessed the effects of different thinning intensities using generalized mixed effect model. The thinning intensity of 0 was taken as a control group to identify the stand changes in unthinned stands over time. Size heterogeneity and the relative contribution of larger trees to total stand growth tended to increase as forest grew without thinning management. While the increases in Gini and SGR (excluding between 0 and 0.5) overall negatively influenced the average annual basal area increment of the remaining trees (BAI). Gini in thinned stands decreased during the short term (two years or more) after thinning and the heavy thinning had lower Gini than other treatments several years (eight years or less) after thinning. GDC reduced greater with increasing thinning intensity, and thinning had a significant negative effect on Gini and SGR and a positive effect on BAI. The thinning impacts on BAI increased with the thinning intensity, while the effect magnitudes of different thinning intensities on Gini and SGR were: T50 < T20 < T25 < T33. Overall, thinning increased the stand growth partitioning of small trees, contributing to a uniform stand structure. However, the changes in stand structural complexity and the partitioning of stand growth were related to both thinning intensity and post-thinning time, particularly to thinning intensity. The results provided some implications for designing the intensity and timing of thinning, as well as for determining the size classes of removed trees for different management goals.

A generalized performance equation and its application in measuring the Gini index of leaf size inequality

A generalized performance equation and its application in measuring the Gini index of leaf size inequality

Inequality of avalanche sizes in models of fracture.

Prediction of an imminent catastrophic event in a driven disordered system is of paramount importance-from the laboratory scale controlled fracture experiment to the largest scale of mechanical failure, i.e., earthquakes. It has long been conjectured that the statistical regularities in the energy emission time series mirror the "health" of such driven systems and hence have the potential for forecasting imminent catastrophe. Among other statistical regularities, a measure of how unequal avalanche sizes are is potentially a crucial indicator of imminent failure. The inequalities of avalanche sizes are quantified using inequality indices traditionally used in socioeconomic systems: the Gini index g, the Hirsch index h, and the Kolkata index k. It is shown analytically (for the mean-field case) and numerically (for the non-mean-field case) with models of quasi-brittle materials that the indices show universal behavior near the breaking points in such models and hence could serve as indicators of imminent breakdown of stressed disordered systems.

Effects of Tree Diversity, Functional Composition, and Large Trees on the Aboveground Biomass of an Old-Growth Subtropical Forest in Southern China

Forest aboveground biomass (AGB) plays an important role in regulating the global carbon cycle and is thus an essential component of ecosystem functioning. In the relationships between biodiversity and ecosystem functioning (BEF), studies have shown that many biotic factors (e.g., species, functional traits, and large trees) and abiotic factors have significant impacts on AGB. However, the relative strength of these affecting factors remains unclear. In this study, we analyzed woody plants (diameter at breast height [DBH] ≥ 1 cm) within a 1.6 ha plot in an old-growth subtropical natural forest in southern China. We used structural equation models to test the effects of tree diversity (species, phylogenetic, functional, and size inequality), functional composition, large trees, and environmental factors (topography, soil nutrients, and understory light) on AGB. Our results indicated that size inequality, the community-weighted mean of maximum DBH (CWM_MDBH), and large trees had significant, positive effects on AGB (p &lt; 0.001), while lower soil phosphorus content was found to promote an increase in AGB. Furthermore, large trees, which were mostly composed of dominant tree species, were the main driver of AGB, and the effect of functional composition (e.g., CWM_MDBH) on AGB was substantially reduced by large trees. We argue that the selection effect plays a key role in regulating BEF relationships in subtropical natural forests and conclude that retaining large-diameter trees and dominant species, along with sustaining a complex stand structure, are key measures for improving productivity.

Trade, investment and size inequalities between countries and the asymmetry in double taxation agreements

Trade, investment and size inequalities between countries and the asymmetry in double taxation agreements

The woody plant Haloxylon ammodendron (C.A. Mey.) provides new insights into the self-thinning relationship and size inequality with wind erosion stress

The self-thinning process and size inequality of plants change with age and wind erosion stress conditions. In this study, we used Haloxylon ammodendron (C.A. Mey.) shrubs in their juvenile stage (1–6 years) as the study subjects. Their density, height, and survival were investigated. The relationship between the mean and variation in the densities was calculated using Taylor’s power law, and the change laws of the density clustering state were analyzed. Additionally, changes in size inequality and the self-thinning process were examined. The results indicated that under the same wind erosion stress, the self-thinning slope was positive ( P &lt; 0.05); the shrub density aggregation of H. ammodendron became denser with increasing wind erosion stress. The size inequality first increased and then decreased as the developing stage progressed. Under the same stress, the competition index increased with increasing age and decreased with increasing stress. We demonstrated that under a harsher microenvironment for plant growth, plants’ clustering and growth increased facilitation, resulting in a shift in the net effect of the positive and negative interactions between individuals. Furthermore, the results revealed that as age increased, the size inequality was left-skewed.

Productivity determinants in the service industry: differences between high and low knowledge intensive sectors

PropósitoLa industria de servicios se ha convertido en un sector importante para el crecimiento económico, particularmente en los países en desarrollo. En este contexto, el objetivo de este artículo es comparar los determinantes de la productividad entre empresas que operan en sectores de servicios de baja y alta intensidad de conocimiento (LKIS y HKIS) en Ecuador.Diseño/metodología/enfoqueUtilizamos un método de estimación de dos pasos. En primer lugar, estimamos la productividad de las empresas y, en segundo lugar, los determinantes de la productividad. Para esto, utilizamos una base de datos de panel no balanceado sobre los estados financieros de las empresas formales ecuatorianas de los años 2007 a 2018.HallazgosNuestros resultados muestran que las empresas LKIS son ligeramente más intensivas en mano de obra en comparación con las empresas HKIS. Los determinantes de la productividad son similares entre las empresas HKIS y LKIS, excepto por las exportaciones y la concentración del mercado. Las empresas HKIS son más productivas cuando el nivel de competencia es bajo, lo que indica que un mayor poder de mercado está asociado con una mayor productividad. La influencia de los impuestos sobre la productividad depende del tamaño de la empresa. Las pequeñas y medianas empresas se ven más negativamente afectadas que las grandes empresas.Implicaciones prácticasLos impuestos deben diseñarse considerando el tamaño de las empresas, ya que podrían afectar su productividad. Por lo tanto, impuestos más bajos para las pequeñas y medianas empresas pueden reducir la desigualdad entre el tamaño de las empresas. Además, el conocimiento que tienen las HKIS debe extenderse a otras empresas convirtiéndose en una externalidad positiva en lugar de una barrera de entrada.Originalidad/valorA pesar de que los determinantes de la productividad del sector servicios se han explorado recientemente, en contraste con el sector manufacturero, los determinantes individuales y contextuales están menos identificados. En este artículo utilizamos un amplio conjunto de características de las empresas que podrían afectar la productividad en las empresas de servicios.

Some of the Mechanisms for Coexistence of Tree Species Diversity in Tropical Forests: A Review of Effects of Tree Density Dependence

Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively.

Inequality on the southwest Maya frontier: House size variations in three polities of the Rosario Valley, Chiapas

AbstractBeing a form of labor investment, house size is frequently analyzed as an index of socioeconomic inequality. However, datasets that lack wide-ranging residential stratigraphic information are not reliable sources of labor investment estimates. This is the case for Late Classic domestic architecture data from three polities in the Rosario Valley (modern-day Chiapas) on the southwest Maya frontier: Rosario, Ojo de Agua, and Los Encuentros. Although the sample's house size inequality generally cannot index period-specific labor investment, it may signify prestige differentiation. For each polity we generated Lorenz curves and calculated Gini coefficients for five variables representing house size (area and volume). Results resemble inequality data from lowland Classic Maya centers. We also demonstrate that the smallest, shortest-lived polity had more equal house size values, likely due to the modesty of its apical elite architecture. In contrast, the two larger, older polities were more unequal because they had substantial palaces.

The influence of climate, soil physicochemical properties and tree size inequality on tree slenderness in mixed forests of Northeastern China

The tree slenderness coefficient (TSC) reflects tree stability and plays an important role in the development of near-natural silviculture programs and forest management decisions. However, there is a lack of TSC models to explore the factors that promote tree stability in mixed forests. Based on the data from 316 boreal and temperate mixed forest plots in northeastern China, this study developed a nonlinear mixed-effects TSC model for 14 tree species. Biotic and abiotic factors including climate, soil, wind speed, species mixtures, and diversity indices were tested for their regulatory effects on the TSC. Response patterns of each species' stability to changes in environmental factor gradients were simulated. In addition, this paper quantified the influence of biotic and abiotic factors on tree stability using the hierarchical partitioning approach. The results showed that mean annual temperature (MAT), mean annual precipitation (MAP), soil cation exchange capacity (CEC), the proportion of sand particles (SAND), mean wind speed (MWS), basal area proportions of the species of interest (BAP), and the Gini coefficient (GC) significantly influenced TSC. Tree stability increased with increasing MAT, CEC, and SAND. In contrast, increasing MAP, MWS, BAP, and GC negatively affected tree stability. The effects of biotic and abiotic factors on TSC were related to species heterogeneity. Our study quantified the drivers of tree stability in mixed forests and revealed the response patterns of TSC to environmental gradients, which will support further assessments of the stability of multi-species mixed forests under future environmental changes.

Climate and forest attributes influence above‐ground biomass of deciduous broadleaf forests in China

Abstract Forests provide a huge carbon pool, a substantial portion of which is stored in above‐ground biomass (AGB). Deciduous broadleaf forests in China are an essential component of global deciduous broadleaf forests, yet the impacts of climate and forest attributes on their AGB are not well understood. Using a comprehensive forest inventory database from 772 plots distributed across temperate and subtropical deciduous broadleaf forests in China (23.51°–42.53°N and 104.24°–128.27°E), we applied variance partitioning analysis, model selection analysis and structural equation models to explore how climate and forest attributes (species diversity, community‐level functional traits and stand structures) affect AGB in different climatic forests (semi‐arid forests, semi‐humid forests and humid forests). Community‐level functional traits and stand structures together explained a great portion of the variance in AGB. The effect of community‐level functional traits was greater than that of stand structures in semi‐arid forests and semi‐humid forests, but smaller in humid forests. Further analyses showed that community‐level maximum tree height, stem density and tree size inequality were important explanatory variables. Although climate and species diversity had minor effects, the direct positive effect of mean annual precipitation (MAP) was still important, especially in semi‐arid forests. Synthesis. Community‐level functional traits but not species diversity were key drivers of AGB, indicating that tree species diversity loss may not impair AGB substantially in deciduous broadleaf forests in China. Moreover, stand structures also had strong effects on AGB in both semi‐arid forests and humid forests, highlighting the importance of structural complexity. In addition, MAP had a direct positive effect on AGB in semi‐arid forests and semi‐humid forests, and a future increase in drought might potentially reduce carbon storage in these forests.