Abstract
Understanding the spatial distribution of tree species in subtropical evergreen-deciduous broadleaf karst forest is fundamental to studying species coexistence and karst species diversity. Here, complete spatial randomness and heterogeneous Poisson process models were used to analyze the spatial distribution patterns of 146 species with at least one individual per ha in a 25-ha plot in southwest China. We used canonical correspondence analysis (CCA) and the torus-translation test (TTT) to explain the distributions of observed species. Our results show that an aggregated distribution was the dominant pattern in Mulun karst forests; the percentage and intensity of aggregated decreased with increasing spatial scale, abundance, mean diameter at breast height (DBH), and maximum DBH. Rare species were more aggregated than intermediately abundant and abundant species. However, functional traits (e.g., growth form and phenological guild) had no significant effects on the distributions of species. The CCA revealed that the four analyzed topographic variables (elevation, slope, aspect, and convexity) had significant influences on species distributions. The TTT showed that not all species have habitat preferences and that 68.5% (100 out of 146 species) show a strongly positive or negative association with at least one habitat. Most species were inclined to grow on slopes and hilltops.
Highlights
The spatial distributions of tree species in forests and their influencing mechanisms have always been a hot topic in research, as such information can help us to understand the potential ecological processes that control species coexistence and community structure[1,2]
Research in forest plots has shown that habitat factors and microhabitat heterogeneity play vital roles in the spatial patterns of tree species[7,12,13], and some studies have shown that many species have a significantly positive or negative relationship with slope, elevation, or aspect[7,14,15]
Spatial distribution can be affected by differences in functional traits and ecological strategies[16,17,18,19]
Summary
The spatial distributions of tree species in forests and their influencing mechanisms have always been a hot topic in research, as such information can help us to understand the potential ecological processes that control species coexistence and community structure[1,2]. Mixed evergreen-deciduous broadleaf forest is unique and representative of the karst landscape in southwest China This forest type has a complicated community structure, rich biodiversity, and high habitat heterogeneity[23,24,25,26], making it an ideal community in which to study spatial patterns. The community-wide patterns of the spatial distributions of species and species-habitat associations and the underlying mechanisms of species coexistence are not well understood in karst forests[5]. This study will contribute to our understanding of species coexistence and diversity in subtropical karst forests
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