Cluster Analysis of Spatial Patterns in Malaysian Tree Species

Abstract

Tree species in tropical rain forests exhibit a rich panoply of spatial patterns that beg ecological explanation. The analysis of tropical census data typically relies on spatial statistics, which quantify the average aggregation tendency of a species. In this article we develop a cluster-based approach that complements traditional spatial statistics in the exploration and analysis of ecological hypotheses for spatial pattern. We apply this technique to six study species within a fully mapped 50-ha forest census in peninsular Malaysia. For each species we identify the scale(s) of spatial aggregation and the corresponding tree clusters. We study the correlation between cluster locations and abiotic variables such as topography. We find that the distribution of cluster sizes exhibits equilibrium and nonequilibrium behavior depending on species life history. The distribution of tree diameters within clusters also varies according to species life history. At different spatial scales, we find evidence for both niche-based and dispersal-limited processes producing spatial pattern. Our methodology for identifying scales of aggregation and clusters is general; we discuss the method's applicability to spatial problems outside of tropical plant ecology.

Tree spatial patterns in fire-frequent forests of western North America, including mechanisms of pattern formation and implications for designing fuel reduction and restoration treatments

“…Continuum percolation (Meester and Roy, 1996) was first applied to spatial analysis of individual mapped tree locations by Plotkin et al (2002), who introduced a method to detect spatial clusters (clumps) in tree maps, and used the approach to investigate habitat associations of Malaysian tree species. Recently, forest scientists working to characterize reference spatial patterns to inform forest restoration have independently converged on this approach (Larson and Churchill, 2008;Abella and Denton, 2009;Sánchez Meador et al, 2011).…”

Seed, dispersal, microsite, habitat and recruitment limitation: identification of terms and concepts in studies of limitations

“…The table does not include studies in which the term was used only as a general term without explanation (35 studies). Even though not mentioned by the authors, we consider the terms safesite limitation (van der Meijden et al 1992), and nichebased limitation (Plotkin et al 2002) synonyms to microsite limitation and include these studies in our comparison. The results of this review clearly show that there is no consistency in the usage of the terms (Table 1), thus, supporting the need of consistent definitions.…”

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

“…Clark et al 1998Clark et al , 1999John et al 2007), but other studies have shown that dispersal limitations could yield similar aggregated distributions if a species were not able to disperse to all suitable sites and instead established near the parent trees (Hubbell 1997;Dalling et al 2002). Some researchers argue that species distributions in plant communities are determined by both processes (Coomes et al 1999;Plotkin et al 2002;Lancaster 2006;Wiegand et al 2007). Analyzing species-environment associations is one effective way to assess the influence of habitat association on species distributions.…”

“…However, as described above, the fact that dispersal limitation may also lead to species aggregation challenges researchers to understand the underlying process of species distributions. Many statistical methods were proposed to resolve this problem Plotkin et al 2002;Diggle 2003). In particular, spatial point process models are a particularly promising method recently developed to address this issue (Moller and Waagepetersen 2003;Waagepetersen 2007).…”