Tropical and subtropical karst forests of south China are under increasing pressure from over-exploitation causing widespread habitat degradation and biodiversity loss. Previous research has demonstrated that topography, as a proxy for resource availability, plays an important role in shaping tree species distributions in tropical forests. However, the association between growth stages and habitats types has not been considered in this analysis. Our aim was to examine the differences among different habitat types to determine whether tree species show similar species–habitat associations at young and mature life stages. We used multivariate regression tree analysis to examined species–habitat associations among eight topographically defined habitats. The results were tested with a torus-translation test and canonical correspondence analysis (CCA) for 74 species in a 15 ha karst tropical seasonal rain forest at the Nonggang National Natural Reserve in south China. We considered two life stages (young and mature) of trees species that showed a positive association with topography. We found marked differences in community characteristics and number of associations among the eight habitats. Of the 74 species subjected to torus-translation test, 63 had significant positive and 70 had significant negative associations with one or more of the eight habitats. Positive associations were more frequent in higher elevation habitats and negative associations were more frequent in lower elevation habitats. This suggests that edaphic and hydrological variation related to topography play important roles in habitat partitioning in heterogeneous karst forests. For the 63 tree species with significant positive associations to at least one habitat, 40 of them had the same positive association at young and mature life stages. The CCA revealed that the six topographic variables considered had consistent relationships with species distribution among all individuals and their two life stages. This indicates that most of the karst forest tree species show consistent associations with a single habitat throughout their life. We conclude that niche differentiation plays an important role in maintaining the diversity of this heterogeneous species-rich karst forest.

Both deterministic and stochastic processes have been linked to forest community assembly; however, their contribution to beta diversity has not been properly explored, and no studies to date have investigated their impacts on sparse depleted soils in forests that contain widespread exposed limestone karst. We found that the pairwise differences in species composition between quadrates was determined by a balanced variation in abundance, whereby the individuals of some species at one site were substituted by an equivalent number of individuals of different species at another site. Both the total beta diversity and its balanced variation in abundance declined with increasing sampling grain size. Our research indicated that environmental differences exert a strong influence on beta diversity, particularly total beta diversity and its balanced abundance variation in larger grain sizes. It was evident that deterministic and stochastic processes worked together, and that deterministic processes were more important than stochastic processes in the regulation of beta diversity in this heterogeneous tropical karst seasonal rainforest of Southern China. However, in future research a functional trait based approach will be required to tease out the relative degree of deterministic and stochastic processes toward an assessment of the temporal changes in species composition.

This study investigates drought resistance-growth trade-offs in dominant tree species across elevationally stratified habitats (depression, middle slope, hilltop) of Nonggang karst seasonal rainforest in southwestern China. Analysis of 38 species along a 190-meter aridity gradient reveals drought resistance enhancement through foliar modifications: 56.79% increase in cuticle thickness, 56.42% denser palisade mesophyll thickness, and 36.48% expansion in spongy mesophyll thickness, accompanied by 45.67% growth reduction. Structural equation modeling confirms a significant drought resistance-growth trade-off (β = − 0.504), indicating carbon allocation constraints. Hilltop species employ an anisohydric strategy combining stomatal optimization (4.45% shorter length, 27.17% wider apertures achieving 33.10% increased opening) with 15.52% reduced upper epidermis cell width and cuticle thickening, enhancing hydraulic efficiency despite 111.63% elevated dark respiration rates. This high-resistance/low-growth strategy contrasts with depression-adapted species showing superior low-light performance: 30.35% higher quantum yield and 63.44% lower light compensation points compared to hilltop counterparts. Environmental driver analysis identifies soil moisture (β = − 0.706) and bedrock exposure (β = − 0.594) as key factors shaping trait divergence. Drought suppresses growth through dual pathways: direct resource limitation (β = − 0.667) and indirect metabolic costs of resistance traits (β = − 0.469). Coordinated leaf trait evolution reduces niche overlap via drought-growth trade-offs, establishing habitat filtration-mediated biodiversity maintenance in karst ecosystems. These results provide a multidimensional framework for balancing stress resistance and productivity in tropical karst vegetation restoration.