Abstract Increasingly frequent seasonal droughts under rapid climate change threaten the growth stability of subtropical mixed forests across the mid‐subtropical monsoon region. In this study, we combined stable hydrogen and oxygen isotope analyses with high‐precision radial growth monitoring to explore how water source use influences the radial growth of four subtropical tree species. Three contrasting functional strategies were identified based on rooting depth and water uptake plasticity. The shallow water‐dependent species ( Cupressus funebris Endl.) featured a root system concentrated in the upper soil layer and obtained 38.3% of its water from shallow layers. During the drought period, declining surface soil water availability was accompanied by low stomatal conductance and photosynthetic rates, and the species experienced net stem shrinkage of 1.1 mm. The deep‐rooted species ( Michelia maudiae Dunn and Abies fabri Craib) exhibited a dual rooting strategy: Deep taproots accessed stable water in the 80–100 cm soil layer, which contributed 67.2%–75.8% of water uptake during drought, while shallow fine roots captured sporadic rainfall in the upper soil layers. During the drought period, these species maintained relatively high water potentials and positive cumulative radial growth, with annual radial growth 1.9–2.5 times that of C. funebris . The balanced‐strategy species ( Liquidambar formosana Hance) displayed a relatively uniform root distribution throughout the soil profile, enabling flexible water acquisition across soil layers and sustaining the highest cumulative radial growth during the drought period. Structural equation models revealed that access to stable water sources, particularly deeper reserves as surface soils dried, sustained radial growth indirectly by maintaining stomatal conductance and photosynthesis. This pathway provides a mechanistic explanation for contrasting drought adaptation among subtropical tree species. Read the free Plain Language Summary for this article on the Journal blog.
Abstract Anthropogenic activities have accelerated plant invasions in mountain ecosystems, impacting the structure and functions of native plant communities. Changes in above‐ground vegetation can drive shifts in below‐ground biota, yet the effects of plant invasions on soil micro‐food web structure and complexity along elevational gradients and the underlying mechanisms remain poorly understood. This study examined the differences between the communities of native herbaceous plants invading Ageratina adenophora along an elevational gradient in the Gaoligong Mountains. We surveyed the composition of the plant community, measured the physicochemical properties of the soil and the enzyme activities of carbon and nitrogen acquisition. The complexity of the soil micro‐food web complexity index (including bacteria, fungi, nematodes and protists) using high‐throughput sequencing and network analysis. Structural equation modelling and two‐way ANOVA were used to analyse the effects of elevation, invasion and their interaction on the micro‐food web. We found that native plant diversity, soil micro‐food web complexity and soil carbon‐ and nitrogen‐acquiring enzyme activities all increased significantly with elevation. However, invasion by A. adenophora both reduced native plant diversity and altered the original elevation pattern of the soil micro‐food web. At the highest elevation (2300 m), the complexity index of the soil micro‐food web in native communities was approximately 4.8 units higher than in invaded communities, while the activities of the C‐acquiring enzymes of the soil were 135% higher and the activities of the N‐acquiring enzymes 119% higher. The complexity of the soil micro‐food web was directly influenced by plant diversity, soil nutrient cycling capacity and multitrophic diversity, whereas environmental factors such as mean temperature and soil moisture exerted indirect effects through soil nutrient status and cycling processes. Our findings demonstrate that the invasion of A. adenophora primarily affects high‐elevation ecosystems by reducing native herbaceous plant diversity, thus reducing the complexity of the micro‐food web of the soil and altering the carbon and nitrogen cycling of the soil. This study advances the mechanistic understanding of how plant invasions impact soil food webs and associated mountain ecosystem processes, providing insights into invasion management and control strategies. Read the free Plain Language Summary for this article on the Journal blog.
Abstract Phosphorus (P) availability is widely recognized as an important constraint on plant growth in many subtropical forest ecosystems, yet how contrasting mycorrhizal strategies mediate the use of inorganic and organic P forms remains unclear. In a subtropical forest, we integrated a 50‐ha survey of adult tree dominance, a seedling growth survey across six 1‐ha plots and a shade‐house experiment to examine how arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) trees adjust root‐fungal foraging strategies across gradients of inorganic and organic P availability. In the field, quadrats with higher inorganic P availability were dominated by AM trees, whereas ECM trees were dominant in soils with greater organic P availability. In both the field survey and the shade‐house experiment, the growth of AM seedlings increased with inorganic P availability, whereas that of ECM seedlings increased with organic P availability. The results of structural equation modelling showed that, in AM seedlings, inorganic P enhanced specific root area and mycorrhizal colonization, thereby increasing root P concentration and biomass. In ECM seedlings, organic P increased mycorrhizal colonization and acid phosphatase activity, elevating root P concentration and biomass. Our findings reveal functional complementarity between AM and ECM tree species in nutrient acquisition strategies. By providing a trait‐based framework, we offer mechanistic insight into variation in seedling performance and community assembly along soil P gradients in subtropical forests. Read the free Plain Language Summary for this article on the Journal blog.
Abstract Generalist species may be comprised of individual specialists. Individual specialization can impact disease transmission at shared resources by shaping contact patterns. Mathematical models of pollinator diseases that spread via flowers have shown that R 0 can be greatly amplified when each forager specializes on one flower species at a time with slow turnover. Yet, such behaviour has not been empirically demonstrated in generalist bumblebees. Here, we used palynology from sequential pollen loads of individual common eastern bumble bees ( Bombus impatiens ) to assess their foraging preferences over time. We used an automated monitoring system to greatly improve recapture rates, hence allowing a more complete characterization of each bee's foraging behaviours. Individuals in a bumblebee colony exhibited unique foraging repertoires of two to three flower species while the full‐colony diet breadth was up to three times larger depending on time of year. Individual repertoires exhibited roughly 50% turnover, on average, over 10 days. Implications for disease transmission when individual repertoire sizes are greater than one may differ from specialization on a single flower species. Hence, we developed mathematical models where each bee has an effective repertoire size of two, and found that ignoring individual specialization still resulted in an underprediction of R 0 , although to a smaller extent compared to a single‐specialty model. Our results provide novel insights into the foraging behaviours of social bumblebees and improve predictions of how diseases are transmitted and persist in complex plant–pollinator networks. Read the free Plain Language Summary for this article on the Journal blog.
Abstract The ability to detect prey is crucial for survival in many animals. However, prey detection is a cognitive process that can be influenced by early life conditions such as prenatal stress or temperature. Mitochondrial function is likely to underlie these effects because cognitive abilities are energetically demanding (i.e. dependent on efficient metabolic function) and because metabolic‐derived oxidative stress and oxidative damage can impair cognitive function. Yet, whether prenatal stress and thermal environments affect prey detection, and whether mitochondrial function mediates such effects, remains poorly understood. Here, we investigated the links between prenatal environments, mitochondrial function and prey detection in the delicate skink ( Lampropholis delicata ). We manipulated egg corticosterone (CORT) levels—a key stress hormone in reptiles—and incubation temperature and assessed the ability of lizards to detect chemical and visual prey stimuli. Then, using flow cytometry, we measured metabolic function, oxidative stress and oxidative damage in the olfactory bulbs and optic tecta, two brain regions involved in sensory processing. While metabolic function and oxidative stress remained robust to early life conditions, CORT and temperature interacted to influence oxidative damage. Particularly, CORT decreased DNA damage in the olfactory bulbs of cold‐incubated lizards but had no effect on hot‐incubated lizards. In both brain regions, lipid peroxidation was lower in CORT‐treated lizards incubated at high temperatures compared to CORT‐treated cold‐incubated lizards, but no other between‐treatment differences were detected. Additionally, CORT‐treated lizards responded faster when presented with chemical cues but not visual stimuli. We did not find any relationship between mitochondrial function and prey detection. Our findings suggest that prenatal conditions have lasting effects on DNA damage and prey detection, but prey detection appears decoupled from mitochondrial function in L. delicata . Read the free Plain Language Summary for this article on the Journal blog.
