生境面积大小对Janzen-Connell效应中密度和距离制约的影响

Influences of Habitat Area Size on Density- and Distance- dependence of Janzen-Connell Effects

关键词:  Janzen-Connell效应  密度制约  距离制约  生境破碎化  生物多样性

Key words:  Janzen-Connell effect  density-dependence  distance-dependence  habitat fragmentation  biodiversity

摘要:

为探究生境面积大小对Janzen-Connell (JC)效应中密度和距离制约的影响以及驱动机制，为生境破碎化背景下植物多样性的维持机制提供科学依据，本研究在Web of Science数据库中收集并筛选出1970-2019年全球50个森林地点作为数据基础，采用荟萃分析法分析密度和距离制约实验中不同类型驱动者的效应值大小，并采用分段回归和非分段回归分别模拟分析密度和距离制约效应值与生境面积的关系。结果表明，在67项研究的161项实验中，病原菌和无脊椎动物的效应值大小在距离制约实验中显著小于0(存在JC效应)，而在密度制约实验中不显著。相反地，脊椎动物的效应值大小仅在密度制约实验中显著小于0。虽然只有距离制约效应值随生境面积的减少呈先增大后减小的趋势，但密度制约趋势线的拟合转折点在距离制约之前，表明生境面积减少会先影响密度制约。本研究阐明了密度和距离制约的主要驱动者分别是密度型驱动者(脊椎动物)和距离型驱动者(病原菌和无脊椎动物)，而密度制约比距离制约对生境面积的减少有更为敏感的表现，可能是这两种驱动者对生境面积的需求不同所导致的。因此，在不同生境面积的片段中关注不同类型的驱动者有利于生物多样性的维持。

Abstract:

In order to explore the effects of habitat area size on density- and distance- dependence of the Janzen-Connell (JC) effect and its driving mechanism,and to provide a scientific reference for the maintenance mechanism of plant diversity under the background of habitat fragmentation,this study collected and screened 50 forest sites around the world from 1970 to 2019 in the Web of Science database as the data basis,and the meta-analysis was used to analyze the effect values of different types of drivers in density- and distance- dependent experiments.Piecewise regression and non-piecewise regression were used to simulate and analyze the relationship between the size of density- and distance- dependent effect and the size of habitat area.The results showed that in 161 experiments of 67 studies,the effect size of pathogens and invertebrates was significantly less than 0 in distance-dependent experiments (with JC effect),but not significant in density-dependent experiments.On the contrary,the effect size of vertebrates was significantly less than 0 only in density-dependent experiments.Although only the distance-dependence effect value increased first and then decreased with the decrease of habitat area,the fitting turning point of the density-dependence trend line was before the distance-dependence,indicating that the decrease of habitat area would first affect the density-dependence.This study clarified that the main drivers of density- and distance- dependence are density drivers (vertebrates) and distance drivers (pathogens and invertebrates),respectively,and the density-dependence are more sensitive to habitat area reduction than the distance-dependence,which may be caused by the different needs of these two drivers for habitat area.Therefore,focusing on different types of drivers in fragments of different habitat areas is conducive to the maintenance of biodiversity.