Prevalence of Inter-Tree Competition and Its Role in Shaping the Community Structure of a Natural Mongolian Scots Pine (Pinus sylvestris var. mongolica) Forest

Hongxiang Wang,Gongqiao Zhang,Ling Liu,Pan Wan,Qianxue Wang,Gangying Hui

doi:10.3390/f8030084

Hongxiang Wang, Gongqiao Zhang + Show 4 more

Open Access

https://doi.org/10.3390/f8030084

Copy DOI

Abstract

Inter-tree competition is considered one of the most important ecological processes of forest development. However, its importance in structuring the spatial patterns of plant communities remains controversial. We collected observational data from two plots in a natural Mongolian Scots pine forest to study the contribution of competition to tree growth, mortality, and size inequality. We used the nearest neighbour method to determine the presence of competition, and unmarked and marked spatial point pattern analyses to test the density-dependent mortality effects and the spatial autocorrelation of tree size. We identified significant positive correlations between tree canopy diameter and nearest neighbour distance in both plots, which were more evident in the denser plot. The pair correlation functions of both plots indicated regular distribution patterns of living trees, and trees living in more crowded environments were more likely to die. However, the mark differentiation characteristics showed weak evidence of a negative spatial autocorrelation in tree size, particularly in the high-density plot. The high mortality rate of suppressed trees and weak asymmetric competition may have accounted for the lack of dissimilarity in tree size. This study showed that inter-tree competition is an important determinant of the development of Mongolian Scots pine forests.

Highlights

Numerous attempts have been made to understand the processes and mechanisms that determine tree spatial patterns [1,2]
The two P. sylvestris var. mongolica stands analysed in this study developed after a fire that occurred determining community spatial patterns is of particular interest in this community, where tree–tree competition is the only interspecies interaction and forest structure is relatively homogeneous
The nearest neighbour analysis of the correlation between the combined distances of the nearest neighbours to a focal tree and the combined crown diameter suggests that competition was an important factor in reducing individual tree growth (Figure 4)

Summary

Introduction

Numerous attempts have been made to understand the processes and mechanisms that determine tree spatial patterns [1,2]. A number of studies have found evidence of competition among plants [9,10,11,12,13], its importance in structuring plant spatial patterns remains controversial [5,12,14,15,16]. Studies of spatial distribution patterns have detected the prevalence of competition among plants, and concluded that competition is a significant contributor to tree mortality [4,17,18]; inconsistent results have been observed in some tree species [5,15,19]. When using spatial pattern analysis methods, determining the prevalence of competition in the structuring of plant communities largely depends on the intensity of inter-tree interactions [9,20] and Forests 2017, 8, 84; doi:10.3390/f8030084 www.mdpi.com/journal/forests. The contribution of competition to plant community patterns may be more detected in shade-intolerant species growing in homogeneous habitats

Results

Discussion

Conclusion