Point patterns of tree distribution determined by habitat heterogeneity and dispersal limitation

Abstract

Understanding processes underlying spatial distribution of tree species is fundamental to studying species coexistence and diversity. This study modeled point patterns of tree distribution, expressed by Cartesian coordinates of individual trees within a mapped forest stand, for the purpose of identifying processes that may generate spatial patterns of tree communities. We used four primary point pattern processes (homogeneous Poisson process, inhomogeneous Poisson process, homogeneous Thomas process, and inhomogeneous Thomas process) to model tree distribution in two stem-mapped forests in Taiwan, Republic of China. These four models simulate spatial processes of habitat association and seed dispersal, allowing us to evaluate the potential contribution of habitat heterogeneity and dispersal limitation to the formation of spatial patterns of tree species. The results showed that the inhomogeneous Thomas process was the best fit model and described most of the species studied, suggesting that spatial patterns of tree species might be formed by the joint effects of habitat associations and dispersal limitation. The homogeneous Thomas process that models the effect of dispersal limitation was the second best model. We also found that the best fit models could be predicted by species attributes, including species abundance and dispersal mode. The significant traits, however, differed between the two study plots and demonstrated site-specific patterns. This study indicated that the interactive operation of niche-based (habitat heterogeneity) and neutral-based (dispersal limitation) may be important in generating spatial patterns of tree species in forest communities.

Population structure and spatial pattern of predominant tree species in a pine–oak mosaic mixed forest in the Qinling Mountains, China

“…Interspecific associations gradually change as forests develop, increasing as the trees age, and determining the spatial distribution pattern (Liu et al 2014). Interspecific competition occurs at small scales, and the effect of environmental heterogeneity (resources and space) dominates the distributional patterns of different species (Lin et al 2011;Kang et al 2014). Our analysis showed that negative association between Q. aliena var.…”

Spatial association and optimum adjacent distribution of trees in a mixed coniferous-broadleaf forest in northeastern China

“…For example, cones of coniferous trees are large and heavy; thus, the cones do not disperse far. The seedlings and saplings from these seeds inevitably form aggregated distributions after germination (Seidler and Plotkin, 2006;Tamme et al, 2010;Lin et al, 2011). With Tilia trees, seedlings are typically abundant near the mother tree because of root sprouting (Zhang et al, 2011).…”

Strong plant-soil associations in a heterogeneous subtropical broad-leaved forest

“…In order to simulate the spatial autocorrelation structure of species caused by dispersal limitation, a homogeneous Thomas model was employed to simulate the aggregation of species based on observed data (Waagepetersen 2007;Shen et al 2009;Lin et al 2011). These mimicked distributions were used as a null model in the analysis (John et al 2007).…”

“…Spatial point process models can mimic the observed spatial structure produced by ecological processes such as dispersal limitation, and can contribute to disentangling the compound effect of habitat association and dispersal limitation in the study of community assembly rules (e.g. Shen et al 2009;Lin et al 2011). Studies of species-environment associations in forest ecosystems are often based on habitat types in term of topographic factors previously Lai et al 2009;Legendre et al 2009).…”