Study On Structure Diversity Of Larch-Spruce-Fir Mixed Stands Based On The Neighborhood Trees

Quantifying trees diversity at the spatial scale was very important in terms of evaluating the economic,ecological and social values of stands and providing guidelines for forest management.This study quantified the non-spatial structure and the spatial structure diversity based on the neighborhood trees through using forest structure indicators(tree species composition,importance value,diameter structure,tree species and diameter class diversity,neighbourhood diversity index,spatial density index,open degree,mingling index,neighborhood comparison ratio and competition index)of the 4 semi-natural mixed stand of larch-spruce-fir with different composition of larch in Jingouling Forest Farm which only exists in the over-logged forest of Changbai Mountains,and compared the heterogeneity of non-spatial structure,forest spatial pattern,size differentiation,tree species spatial isolation degree and trees competition.The main conclusions were as follows:1)The larch-spruce-fir stands in the study area contained more than 10 typical tree species in Changbai mountain area.Cultivated Larch and natural fir have been dominant in the stand.The diameter distribution of stands was a single-peak anti-J-shaped curve or a left side mountain-liking curve.Weibull model has high fitting accuracy to be applied for the tree diameter distributions.The values of diversity index by species and diameter class and evenness index of the larch-spruce-fir stands with different composition of larch changed little,but there were small differences.Over time,the larch-spruce-fir mixed stands will eventually succeed as a spruce-fir forest.2)Larch-spruce-fir stands was random distributed,and the distribution of the main tree species were consistent with the results of the stands.The openness of stands was obviously insufficient,and the space for the trees' growing was small.The species diversity of spatial structure units in the mixed forest of larch are highly diverse,and the segregation of coniferous trees was slightly higher than broadleaf trees.When the fir and some other species were affected little by larch and had high degree of tree species spatial isolation in the relatively pure forests,the spatial structure moves towards a stable mixed forests.The size of the tree was indicated a middle level,and the difference of the diameter of the forest was little.There were a certain number of small-diameter trees in the plot,and the regeneration was better.From the view of trees competition,the pressure of the larch mainly came from intraspecific competition and other tree species mainly came from interspecific.Overall,when the larch account for 30%,the needle broad ratio of 8:2 and the forest density of 880,the competition of trees was low.3)The results of the analysis of the three neighbourhood diversity indices(species diversity,structural diversity by diameter distribution,and structural diversity by diameter variation)are consistent with the results of the Shannon diversity index,and the close index values are obtained for stand with similar structure.The neighbourhood diversity index can describe the diversity of forest stands and spatial structure characteristics,and reflect the spatial variation of species and structure diversity,and has obvious ecological significance.It can be applied to the structural adjustment of forest stands and provide a theoretical basis for rational forest management.