Neighborhood Effects Of Woody Plants In Evergreenbroad-leaved Forest In Tiantong, Zhejiang Province

Neighborhood effects play a key role in regulating the structure and function of plant communities.To date,revealing the consequences of neighborhood effects in plant communities has become a focus of ecological research.Although our understanding of the relationship between aboveground biomass and diversity and its mechanisms has been significantly advanced,it is still not clear how different in size of conspecific or heterospecific neighbors affect aboveground biomass of focal trees.This study mainly focused on neighborhood effects in a 4.84 ha subtropical evergreen broadleaved forest in Tiantong,Zhejiang province.We used linear mixed effect model to study the influence of trees on the composition and function at its neighborhood and the relationship between neighboring trees and aboveground biomass of the focal tree,based on plants spatial distribution information,environmental factors and functional traits.We found that:1.Neighborhood abundance of conspecific neighbors and species richness both increased with increase in trait difference among neighbors and soil moisture.Tree size had no influence on abundance of conspecific neighbors and species richness of all neighbors,however,it positively increased abundance of conspecific neighbors and species richness of neighbors smaller than focal trees.In terms of abundance of conspecific neighbors smaller than focal trees,it only increased with increase in tree size at 10-meter scale.2.Functional diversity of neighbors were mainly affected by tree size,competition intensity of neighbors and variance in soil moisture.Specifically,tree size significantly decreased functional richness of neighbors,while neighborhood competition intensity and variance in soil moisture both significantly increased functional richness.Secondly,functional evenness of neighbors increased significantly with increase in variance in soil moisture,and significantly decreased with increase in competition among neighbors,but had no relationship with tree size.In addition,tree size,competition intensity and variance in soil moisture all significantly increased functional divergence of neighbors.3.The aboveground biomass of focal trees mainly depended on functional dissimilarities between focal trees and its neighbors,with the interpretation of models as high as 58%.Specifically,focal trees' aboveground biomass was positively correlated with dissimilarities both in tree height and wood density,whereas negatively correlated with dissimilarities in leaf nitrogen content,leaf dry mass content and specific twig length.We found that functional dissimilarities between focal trees and its neighbors larger than it(tree height,relative crown area,specific twig length,Huber value,leaf phosphorus content,specific leaf area and leaf dry mass content),soil fertility and density of neighbors larger than the focal tree all were negatively correlated with focal trees' aboveground biomass.On the contrary,dissimilarity in wood density showed positively relationship.In terms of neighbors smaller than the focal tree,dissimilarities in tree height,wood density,relative crown area and specific leaf area and stem density all were positively correlated with focal trees' aboveground biomass.4.The influence pattern of functional dissimilarities between focal trees and its neighbors on its aboveground biomass was not changed with heterospecific or conspecific neighbors.No matter either heterospecific or conspecific neighbors,trait dissimilarities between focal trees and neighbors larger than it were negatively correlated with trees aboveground biomass,while trait dissimilarities between trees and neighbors smaller than it were positively correlated with trees aboveground biomass.Our results showed that tree size may promote neighborhood species richness and functional divergence,but it also decreased functional richness,and these effects mainly played a role in neighbors smaller than the focal tree.Meanwhile,functional difference between focal trees and neighbors was the key biological drivers which influenced its aboveground biomass,and the intensity and direction of the relationship depended on size of neighbors.Functional dissimilarities between focal trees and neighbors larger than it were negatively correlated withits aboveground biomass which indirectly reflected niche overlap between them,that could benefit for accumulating biomass.However,functional dissimilarities between focal trees and neighbors smaller than it were positively correlated with its aboveground biomass which indirectly indicated niche complementary also could benefit for increasing biomass.This study enhanced our understanding on diversity maintenance mechanism involving neighbors in subtropical evergreen broad-leaved forests,especially the neighborhood effects on individual growth.