Study On The Community Structure And Stability Of Forest Gap In Castanopsis Fissa Natural Forest

Scientific management of natural forests is one of the main ways to improve the quality of forest resources in our country.Forest gap as an important stage of forest growth cycle plays a role in promoting regeneration.Castanopsis fissa is one of the main tree species of natural broad-leaved forest in Fujian Province,it integrates ecological economic and social benefits.Using line transect sampling method and quadrat investigation method to survey 20 gaps in Castanopsis fissa natural forest.In this paper,the community structure,stability,regeneration niche and edge effect of gaps in Castanopsis fissa natural forest were studied,and the impacts of different size gaps for Castanopsis fissa natural forest community were explored.The aim of this study was to reveal the dynamic law of gaps in Castanopsis fissa natural forest,and to provide the theoretical basis for the protection and regeneration of Castanopsis fissa natural forest.The results were listed as follows:(1)The Castanopsis fissa natural forest was in a relatively stable state.The gaps,non-gaps,arbor layer,shrub layer,various sizes gaps in Castanopsis fissa natural forests were all in stable state.The stability of arbor layer was higher than that of shrub layer.The formation of gaps reduced the stability of Castanopsis fissa natural forest.The overall stabilities of the tree layer,the shrub layer and gap community were weaker than that in the non-gaps.There were some differences in the stability of the gaps in each size gaps,ranging from strong to weak:0～100 m2>150～200m2>100～150 m2>0～50 m2.The gap improved the species diversity of the community,and the change tendency of the species diversity in Castanopsis fissa natural forest was opposite to that of the stability.There was no significant negative correlation between the community stability and species diversity in Castanopsis fissa natural forest,that is,there was no necessary linear relationship between community stability and species diversity.(2)The niche overlap of the main tree species in the gap was greater than that in the non-gap.The niche overlap of the arbor layer in the gap was also larger than that in the non-gap,while the shrub layer in the gap was opposite,the niche overlap of the main tree species in the non-gap shrub layer was larger than the gap.The niche overlap of the gaps with an area of 0～50 m2 were the smallest.The niche overlap of the gaps with an area of 100～150 m2 and 150～200 m2 were larger,and their niche overlap and the degree of utilization were similar.The important value of Castanopsis fiss was the largest in the community,while its niche breadth was also large.The important values of tree species such as Schima superb,Castanopsis carlesii and Cyclobalanopsis glauca were larger,and their niche breadths were larger than those of the other species in the community.After long-term succession,Schima superb,Castanopsis carlesii and Cyclobalanopsis glauca would form a mixed community with Castanopsisfiss.(3)The edge effect of gap in Castanopsis fiss natural was positive,which had an effect on increasing species diversity and decreasing ecological dominance.There was a significant negative correlation between the ED and EC.In different size gaps,the gap edge effect ED showed a trend that 507～100 m2>0～50m2>100～150 m2>150～200m2.The gap edge effect Ec showed a trend that 50～100 m2<0～50 m2<100～150 m2<150～200 m2.The edge effect intensity showed that the gaps of 50～100m2 had the strongest edge effect.And the edge effect was gradually weakened with the increase of gap area.