Spatial Distribution Pattern and Intraspecific Competition of Populus euphratica Population in the Lower Reaches of the Tarim River Based on LiDAR Data
[Objective]This study aims to analyze the spatial distribution pattern and intraspecific competition intensity variation of Populus euphratica tree populations under different groundwater depth levels in arid regions,and explore the response characteristics of population spatial structure to the arid environmental condition.[Method]Fifteen plots of 50 m × 50 m in a natural P.euphratica forest were set up at equal distances within a range of 1 000 m away from the river channel at three cross-sections in the lower reaches of the Tarim River.The terrestrial laser scanning(TLS)technique was used to acquire the three-dimensional structural parameters of trees in the plots.The spatial distribution indicators such as aggregation index(R),David-moor clustering index(I),point pattern function g(r),and competition index(CI)were used to analyze the spatial distribution pattern and intraspecific competition intensity.[Result]1)The R and I indices indicated that P.euphratica population structure mainly showed aggregated patterns at the different groundwater levels in the study area.2)The analysis of the g(r)function values obtained from the radius(r)distance of 0-25 m away from a tree in various plots showed that most of the plots exhibited an aggregated distribution pattern within r＜5 m distance,and changed to random distribution pattern with r＞5 m.With the increase in groundwater depth,the tree's aggregation distance r will decreased.3)The analysis results of the point pattern function g12(r)indicated that there were differences in their distribution patterns among different age-class trees.Middle-aged trees mainly showed an aggregated pattern,while other age-class trees showed a random distribution pattern.There was a positive correlation between middle-aged trees and young or mature trees,showing a mutually promoting relationship,while trees of other age classes did not show significant correlations.4)The average CI index showed a decreasing trend with the increase of distance from the river channel,and the individual tree CI decreased with the increase of DBH.[Conclusion]P.euphratica population in the lower reaches of the Tarim River shows an aggregated distribution pattern at small observation scales and however exhibits to a random distribution pattern characteristics with the increase of scale.As the distance from the river increases and the groundwater level gradually decreases,the stand density decreases and the average competition intensity within the species weakens,resulting in a declining trend of trees.
Populus euphraticaterrestrial laser scanningspatial distribution patternintraspecific associationcompetitive intensity
万方数据
维普
