Recruitment in Tropical Tree Species: Revealing Complex Spatial Patterns

Abstract

Seed dispersal should leave a signature on the spatial distribution of recruits that can be quantified using sophisticated techniques of spatial pattern analysis. Here we study spatial patterns of five frugivore-dispersed tropical tree species at the Barro Colorado Island forest, Panama, to describe detailed properties of the spatial patterns of recruits and to investigate whether these patterns were produced by temporally consistent mechanisms. Our spatial point pattern analyses detected the existence of surprising spatial structures, such as double-cluster and superposition patterns, and they allowed for a detailed quantification of their properties. The spatial recruitment patterns were composed of two independent components comprising a random component and a component showing a complex spatial pattern with two critical scales of clustering. The analysis allowed an estimation of the relative contribution of scatter dispersal versus clump dispersal in effective seed dispersal for our study species. Additionally, the cluster characteristics were temporally consistent over 25 years and correlated with several species traits. We are just beginning to discover the richness of spatial patterns found at tropical forests, and we are confident that a combination of advanced point pattern analysis with field data will allow for significant advances in establishing the link between spatial patterns and processes.

Fitting Ecological Process Models to Spatial Patterns Using Scalewise Variances and Moment Equations

“…This represents a major advance over previous approaches because it provides a clear analytical link to models formulated explicitly in terms of ecological processes. Some previous studies have related patterns to classic cluster algorithms (Waagepetersen and Guan 2009;Wiegand et al 2009), but such linkages provide little insight into, for example, how dispersal and density dependence contribute to pattern formation. Linking to individual-based models derived using basic ecological principles (e.g., reproduction, mortality, dispersal, competition) allows easier interpretation (e.g., Anand and Langille 2010).…”

Forest dynamics of a subtropical monsoon forest in Dinghushan, China: recruitment, mortality and the pace of community change

“…There is a possibility that upper-canopy species create a suitable environment for lower-stature species, and if canopy individuals die, the environment can become less hospitable and lead to death of subcanopy individuals (Flores & Jurado 2003). However, ontogenetic factors could also affect the outcome of facilitative interactions (Callaway & Walker 1997), and spatial scales should be included in the analyses because spatial processes and mechanisms may act on different scales (Wiegand et al 2009). …”

Sex-specific pattern of spatial genetic structure in dioecious and clonal tree species, Populus alba L.

“…As a summary statistics, we used the pair correlation function, g(r), being the normalized neighborhood density function. It can be defined as the expected density of points (ramets) of the average point of the pattern at a certain distance r, divided by the mean density (λ) of points (Illian et al 2008;Wiegand et al 2009;Wiegand and Moloney 2014). We used the double-cluster process as the null model.…”