Spatial distribution and interspecific associations of tree species in a tropical seasonal rain forest of China.

Guoyu Lan,Min Cao,Thorsten Wiegand,Hua Zhu,Yuehua Hu,Stephan Getzin,Guishui Xie,Ethan P White

doi:10.1371/journal.pone.0046074

Abstract

Studying the spatial pattern and interspecific associations of plant species may provide valuable insights into processes and mechanisms that maintain species coexistence. Point pattern analysis was used to analyze the spatial distribution patterns of twenty dominant tree species, their interspecific spatial associations and changes across life stages in a 20-ha permanent plot of seasonal tropical rainforest in Xishuangbanna, China, to test mechanisms maintaining species coexistence. Torus-translation tests were used to quantify positive or negative associations of the species to topographic habitats. The results showed: (1) fourteen of the twenty tree species were negatively (or positively) associated with one or two of the topographic variables, which evidences that the niche contributes to the spatial pattern of these species. (2) Most saplings of the study species showed a significantly clumped distribution at small scales (0–10 m) which was lost at larger scales (10–30 m). (3) The degree of spatial clumping deceases from saplings, to poles, to adults indicates that density-dependent mortality of the offspring is ubiquitous in species. (4) It is notable that a high number of positive small-scale interactions were found among the twenty species. For saplings, 42.6% of all combinations of species pairs showed positive associations at neighborhood scales up to five meters, but only 38.4% were negative. For poles and adults, positive associations at these distances still made up 45.5% and 29.5%, respectively. In conclusion, there is considerable evidence for the presence of positive interactions among the tree species, which suggests that species herd protection may occur in our plot. In addition, niche assembly and limited dispersal (likely) contribute to the spatial patterns of tree species in the tropical seasonal rain forest in Xishuangbanna, China.

Highlights

Numerous mechanisms have been proposed to explain coexistence of tree species in tropical forests on local scales [1,2]
The maps suggest that these twenty species have distribution patterns which are related to topography, especially for P. chinensis (Fig. S2a), C. echidnocarpa (Fig. S2j), P. kerrii (Fig. S2n), M. creaghii (Fig. S2o or Fig. 2e)
In this study we investigated how the univariate and bivariate spatial patterns of twenty dominant tree species changed in a tropical seasonal rain forest with life stage

Summary

Introduction

Numerous mechanisms have been proposed to explain coexistence of tree species in tropical forests on local scales [1,2]. One of the most prominent hypotheses is the Janzen–Connell hypothesis that states that distance- or density-dependent mortality due to predation or host-specific pests should promote less aggregated and more mingled spatial distributions of species [3,4]. An extension of the Janzen–Connell hypothesis, the species herd protection hypothesis, suggests that heterospecifc neighbors can promote coexistence by thwarting the transmission of biotic plant pests [7,9]. According to the species-herd protection hypothesis, heterospecific crowding may be of general benefit for the survival of recently established seedlings because fewer encounters between a host and its speciesspecific pests and pathogens would occur [9,10]

Methods

Results

Conclusion