Abstract Ecological communities are structured by a few common species, while most occur at low abundance. Understanding the drivers of this widespread pattern raises fundamental questions about community assembly rules and is important for applied ecology for identifying conservation targets. We used assemblages of phyllostomid bats to answer the following questions: (i) Does a higher divergence of morphological traits and functional hypervolume from the assemblage explain the prevalence of low‐abundance species? (ii) What is the relative importance of single functional traits and functional hypervolume divergence to explain such patterns? We sampled phyllostomid bats across an urban–rural landscape and estimated species abundance, measured key morphological traits, and calculated functional hypervolumes. We then applied a Bayesian causal inference framework to identify the drivers of abundance. The divergence of functional hypervolume, flight performance, and food acquisition traits had a negative impact on the abundance of the species. This pattern holds whether assessing aggregated species abundance or when considering spatiotemporal variation in assemblage structure, implying that low‐abundance species had functional hypervolumes and morphological traits more divergent from the assemblage average. Species ranked at the quantile intervals 0%–25% and 25%–50% of abundance occupied hypervolumes 45.9% and 46.8% more divergent compared to species ranked at Q 75%–100%. Similarly, the species at Q 0%–25% and 25%–50% exhibited a 59.5% greater divergence in morphological traits compared to common species. Such divergence on specific traits and intraspecific functional space from the assemblage centroid can result in a substantial reduction (13%–57%) in species abundance. Our results indicate that low‐abundance species are linked to their trait and hypervolume functional divergence. We propose that the position of the species in the functional space and the divergence of sensory‐ and vagility‐related traits are factors that determine the structure of bat communities, which denotes niche axes that have likely been narrowed at the current human‐dominated habitat. Our findings emphasize the importance of low‐abundance species, as they occupy unique ecological niches and likely contribute to specific ecosystem processes. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Mangrove forests are important blue carbon ecosystems, yet long‐term above‐ground biomass (AGB) dynamics in arid deltaic systems remain poorly understood. Here, we integrated field‐derived AGB data with multisource remote sensing and machine learning models (random forest, gradient‐boosted regression tree, support vector regression and classification and regression trees) to map historical patterns and predict future AGB dynamics in the Indus Delta mangroves for 2030, 2040 and 2050. AGB increased significantly over time, with mean values rising from 18.13 ± 9.1 Mg/ha in 2002 to 25.75 ± 8.32 Mg/ha in 2022, as indicated by Mann–Kendall trend analysis. Among models, GBRT performed best ( R 2 = 0.65, RMSE = 0.52) and projected continued increases in AGB to 30.31 ± 4.8 Mg/ha in 2030, 40.12 ± 6.4 Mg/ha in 2040 and 48.6 ± 7.9 Mg/ha in 2050. AGB was positively associated with vegetation indices and negatively related to land surface temperature and land‐use change. Synthesis . Mangrove AGB in the Indus Delta is increasing and is projected to continue rising under current conditions, highlighting substantial carbon sequestration potential in arid coastal systems. The strong performance of machine learning models demonstrates their utility for large‐scale biomass prediction, while the observed environmental controls emphasize the importance of sustaining freshwater input, sediment supply and restoration efforts for long‐term ecosystem resilience and blue carbon management. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Plants produce a variety of structural and chemical defences to deter herbivores, which can covary across every scale of biological organization. Along these lines, it has been suggested that young leaves differ from old leaves in their defence strategies, but studies have largely focused on woody plants and/or chemical traits. Thus, we lack an understanding of how structural and chemical defences ontogenetically covary across a large portion of plant diversity. We investigate the range of structural and chemical defences of thistles (tribe Cardueae), which comprise herbaceous species with a wide spectrum of defensive traits. We collected structural and chemical trait data across species and leaf ages from field collections, herbarium specimens and the literature. Species' young leaves tend to produce similar suites of traits, with greater interspecific variation in older leaves. Young leaves are dominated by chemical defences, while older leaves produce a broader range of both chemical and physical defence traits. Leaf spininess is associated with a distinct chemical profile that differs from that of non‐spiny species. Our study demonstrates how defence strategies can vary across the leaves of herbaceous species and their ages. Expanding such efforts will be critical to further our macroevolutionary understanding of variation in plant defences. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Plants play a critical role in the carbon cycle by driving carbon uptake and release through photosynthesis and respiration, with dominant species exerting large control over these fluxes. Invasive plants can disrupt carbon cycling because of their high biomass and rapid growth, yet their influence across a growing season remains unclear. Many studies show that invasive species exhibit greater phenological plasticity than native species, which can enhance their competitive ability. Under warming, this phenological plasticity may allow invasive species to better track resource availability and capitalize on longer growing seasons, potentially disadvantaging native communities. To test how warming and an invasive species interact to alter carbon dynamics, we measured plant biomass, net ecosystem exchange (NEE), gross primary productivity (GPP), and ecosystem respiration (ER) three times over the growing season in a Calluna vulgaris ‐invaded alpine community in New Zealand. We removed C. vulgaris and increased temperatures using open‐top chambers in a factorial design. With the removal of C. vulgaris, we found significantly lower community plant biomass and weakened ecosystem carbon sink strength due to lower GPP across the growing season. These responses reflect the removal of C. vulgaris itself rather than a general reduction in biomass, as biomass‐corrected NEE showed the same patterns. Surprisingly, warming increased GPP in native‐only plots, but not in C. vulgaris‐invaded plots. C. vulgaris had the strongest effects on carbon fluxes early in the season, with influence diminishing later in the season. This seasonal shift aligns with C. vulgaris phenology, as late‐season measurements coincided with peak flowering, a period likely characterized by reduced photosynthetic investment. Overall, removal of C. vulgaris decreased plot‐level biomass and productivity, while warming more strongly enhanced carbon uptake in native rather than in invaded plant communities. These findings indicate that invasive species can exert an outsized influence on ecosystem carbon dynamics, independent of warming, and these effects vary seasonally. As biological invasions and climate warming intensify, resolving their interactive and time‐dependent impacts on carbon cycling will be important for improving ecosystem and carbon models. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Intraspecific trait variation can strengthen or weaken species interactions in ecological communities. A mechanistic understanding of how intraspecific variation affects species interactions will help identify general rules about when intraspecific variation strengthens versus weakens species interactions. We used a series of greenhouse experiments to investigate the effect of larval body size variation of an herbivorous insect on the total damage and distribution of damage on its host plant, and to determine the mechanisms underlying the effects of size variation. Using groups of larvae with the same mean body size but different levels of variation in body size, we tested three mechanisms: (1) nonlinear averaging, (2) disproportionate effects of large individuals and (3) feeding facilitation. We found that groups of herbivores with high size variation damaged plants more and dispersed their damage more among leaves compared to groups of herbivores with low size variation. A nonlinear relationship between individual herbivore body size and plant damage suggests that the effects of size variation on total damage are likely due to nonlinear averaging. Though none of the mechanisms we tested fully explained the effect of size variation on the spatial distribution of damage, our results suggest that this effect may be due to size‐dependent changes in larval behavioural response to density. Our results suggest the effects of intraspecific trait variation can be mediated by different mechanisms for different response variables, and the mechanism can be context dependent. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Centuries of timber production have homogenized many forests by reducing variation in canopy density and deadwood availability, with far‐reaching consequences for biodiversity and trophic interactions. Recent studies indicate that increasing structural heterogeneity through canopy gap creation and deadwood enrichment can promote biodiversity and support tree regeneration. These management practices may also influence tree performance, among others assessed by folivory and leaf fluctuating asymmetry, which indicate how well trees resist leaf damage and maintain developmental stability under environmental stress. However, it remains unknown whether such management enables trees to mitigate folivory and developmental instability, especially across macroclimatic gradients such as elevation. We conducted a large‐scale experiment in Germany across 11 pairs of forests: one structurally homogeneous control forest and one experimentally heterogenized forest, where canopy gaps and deadwood were created to increase between‐patch structural heterogeneity. The forests spanned an elevation gradient from 38 to 1143 m. Across all forest pairs, we sampled 19,656 leaves from 1404 European beech ( Fagus sylvatica L.) trees. We quantified folivory, leaf fluctuating asymmetry, microclimatic conditions (temperature, vapour pressure deficit) and biotic pressures (predation, parasitism, competition). Experimental enhancement of structural heterogeneity reduced folivory overall but increased leaf fluctuating asymmetry. Folivory increased with elevation, while leaf fluctuating asymmetry declined, producing an inverse relationship: At low elevations, structural enhancement reduced folivory but increased asymmetry, whereas at high elevations it increased folivory but reduced asymmetry. Microclimatic variables explained variation in both folivory and leaf asymmetry more consistently than biotic pressures. These findings extend the stress‐gradient framework by showing that identical management interventions can yield opposite outcomes depending on the macroclimatic gradient associated with elevation. Thus, integrating elevation and climate context into forest management seems to be crucial for maintaining the resilience of temperate forests under global change. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Animals develop familiarity with specific areas through repeated use, gaining detailed knowledge of local conditions, such as food availability, predator presence, and landscape features, which can directly impact fitness. While site familiarity has been widely studied in the context of foraging and breeding, no studies have assessed the fitness consequences of using familiar locations near key sleeping sites. Moreover, studies on site familiarity have generally focused solely on predation risk, overlooking the potential influence of harvest. To further our understanding of the fitness impacts of site familiarity, we used GPS data from 106 male wild turkeys ( Meleagris gallopavo ) to quantify among‐individual differences in site familiarity, measured as proximity to familiar roosting sites, and examined how among‐individual differences in site familiarity related to susceptibility to both predation and harvest. We found substantive individual differences, with some males consistently remaining closer to familiar roosting areas than others. Male wild turkeys that exhibited greater site familiarity and stayed near familiar roosting sites were more likely to survive the hunting season, suggesting that site familiarity may facilitate hunter avoidance, possibly through increased knowledge of hunter activity. However, males that displayed greater site familiarity and occurred closer to familiar roosting sites had elevated predation risk, indicating a trade‐off in which spatial predictability may benefit individuals under one mortality source while exposing them to another. Our findings, together with prior research, challenge the assumption that site familiarity is inherently beneficial and emphasize the importance of evaluating space use behaviour in the context of multiple, interacting mortality risks. In harvested populations, such insights are especially valuable for understanding how animals navigate trade‐offs between predation and harvest risk, which can deepen our understanding of species responses to human activity. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Urbanization represents one of the major anthropogenic alterations of the Earth's surface, with significant impacts on biodiversity and its functions. Soil animals are essential components of biodiversity, and their trophic interactions play integral roles in the functioning of terrestrial ecosystems. However, how urbanization reshapes soil food webs is largely unknown. We assessed the structure and function of soil food webs using stable isotope analysis and the energy flux approach in urban grasslands and woodlands in a subtropical city in China, using natural ecosystems in the city surroundings with the same vegetation type as the reference. In urban woodlands, total biomass was six times higher and energy flux was two times higher than in the reference natural forests, resulting in a 50% lower energy turnover (energy flux‐to‐biomass ratio) and supporting longer food chains. By contrast, urban grasslands had similar total biomass, total energy flux and energy turnover to wild grasslands, but both the bacterial‐to‐fungal ratio and soil consumption‐to‐faeces production ratio increased, suggesting accelerated soil carbon cycling. Further, we found that urbanization increases spatial variability of trophic interaction strengths, especially in woodlands, which was attributed to the strong specific predator–prey interactions and higher environmental heterogeneity of urban green spaces. Overall, contrary to the generally assumed negative impacts of land‐use changes on soil communities, our study demonstrates that urbanization enhances the total energy flux in soil food webs but changes the balance between different energy channels and increases the variability of trophic interactions. In addition, the divergent responses to urbanization observed in woodlands and grasslands emphasize the importance of vegetation‐specific management to improve soil ecosystem functioning, such as C sequestration in urban areas. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Dead wood decomposition is a crucial ecological function in forests, influenced by climate and facilitated by microbial communities. While fungi are considered the primary decomposers, bacteria also contribute, interacting with fungi in both facilitative and competitive ways. However, it remains unclear how these interactions respond to climate, and how they influence decomposition. To study this, we placed 243 Norway spruce ( Picea abies L.) logs along a 1200‐km latitudinal gradient in Sweden, and under contrasting shade conditions, creating a gradient in microclimate. We characterized microbial communities and quantified wood density loss after 3 years of field exposure. Regional temperature had a positive effect on wood density loss and bacterial and nitrogen‐fixing bacterial richness, while fungi remained unaffected. Shade level had no effect on decomposition rates, but significantly influenced both fungal and bacterial absolute abundances, with higher abundances in sun‐exposed than shaded logs. Nitrogen‐fixing bacterial community composition and fungal richness correlated with wood density loss. Specifically, decomposition rates increased with fungal richness up to a certain level but then decreased. Our modelling revealed a significant three‐way interaction between fungal richness, nitrogen‐fixing bacterial richness and regional temperature, suggesting that in colder regions, decomposition rates increase with fungal richness when richness of nitrogen‐fixing bacteria is high, while in warmer regions, the same combination decreased decomposition. While underscoring fungi as key wood decomposers, our results suggest that nitrogen‐fixing bacteria play a complementary role in the decomposition process. Whereas antagonistic interactions among microbes may reduce decomposition rates in warm regions, facilitative interactions may increase decomposition rates in cold regions. Climate warming due to climate change and forestry operations might lead to an increase of nitrogen‐fixing bacteria, which, in turn, may enhance antagonistic interactions among fungi. Read the free Plain Language Summary for this article on the Journal blog.

Abstract Stand functional diversity (Rao Q ) and stand functional composition in terms of the functional traits of the component species (CWM trait) are critical for ecosystem processes and functioning, such as litter decomposition and associated nutrient cycling. Litter decomposition rates could differ among stands varying in functional diversity and composition because of interspecific variation of resource economic traits in litter quality as well as differences in microenvironmental conditions. However, whether and how functionally diverse stands with different microenvironmental conditions change the litter decomposition rates among functionally contrasting species is poorly understood. Here, we hypothesized that stand functional diversity would promote litter decomposition of resource acquisitive, intermediate and conservative species but with inconsistent strengths, because of the potential positive effects of higher probability for litter nutrient exchange or facilitative microclimate in diverse stands. Conservative species' litter might benefit less from the positive stand diversity effect than intermediate species' litter, and then acquisitive species' litter (Hypothesis 1). Meanwhile, we hypothesized two alternative scenarios for the effect of stand functional composition: First, acquisitive species' litter would decompose faster in stands dominated by acquisitive species, while conservative species' litter would decompose relatively faster in stands dominated by conservative species (Hypothesis 2a). Second, any species would decompose faster in stands halfway between ‘conservative’ and ‘acquisitive’ functional composition with a steeper humpback in acquisitive species' litter than in intermediate species' litter, and then in conservative species' litter, as a consequence of high functional diversity (Hypothesis 2b). We tested our hypotheses through a litter decomposition study in a tree diversity experiment in subtropical China. We quantified the leaf litter mass losses for acquisitive, intermediate and conservative species and measured microclimates across 30 stands that represent a range of tree functional diversity and composition over five decomposition periods over 394 days. Increasing stand species richness and stand functional diversity were significantly associated with higher leaf litter decomposition rates across all three functionally contrasting litter species. This positive effect did not change with the litter species' resource acquisition strategies, in partial support of our Hypothesis 1. Increasing stand functional composition along an axis from resource conservative to acquisitive had rather similar humpback relations with leaf litter decomposition rates for all three litter species, which partly supported our Hypothesis 2b but rejected our Hypothesis 2a. Our study provides mechanistic insights into the potential direct and indirect roles of functional trait diversity and composition in driving litter decomposition, and these insights are relevant to many ecosystem types globally. Read the free Plain Language Summary for this article on the Journal blog.