Study On Spatial Structure Of Natural Secondary Phoebe Bournei Forest And Its Interspecific Association

Taking the natural secondary Phoebe bournei forest in Anfu as research object, this paper gathered data through investigating sample plots. The indices of mingling degree,neighborhood comparison and uniform angle index were used to analyze its characteristics of spatial structure. According to evaluation index of the stand spatial structure, it was divided into 5 levels. The interspecific associations between Phoebe bournei in different periods and other tree layer species were analyzed by using variance ratio(VR) test,2?-test for2 ? 2 contingency table, Spearman's rank correlation coefficient. The research results could provide scientific evidences for making adjustments of optimizing spatial structure of natural secondary Phoebe bournei forest and management. The main results were as follows:(1) The composition of the natural secondary Phoebe bournei forest tree species mainly included 15 species,such as Phoebe bournei ? Castanopsis fargesii ?Machilus pauhoi and so on and it showed big difference between different stand; according to the rule of diameter distribution,the number of trees in stand presented obviously features of uneven — aged forest and its distribution was fundamentally in the shape of inverse J type.(2) Average mingling degree of stands was 0.525 which was intensive mingling;Average neighborhood comparison was 0.506 which was in the state from intermediate to poor; Average uniform angle index was 0.518 which was aggregated distribution. Average mingling degree of the research object-Phoebe bournei was 0.569 which belonged to intensive mingling; Average neighborhood comparison was 0.534 which belonged to the state from intermediate to poor; Average uniform angle index was 0.463 which indicated uniform distribution.(3) The range of evaluation index of spatial structure was from 0.08 to 0.89, existing great distances with ideal spatial structures. Only the level of standard sample plots of numbers 5 was the highest(level of V)and the mingling degree of forest tree also was high;The size of the stand had no distinctive difference and its distribution patterns were arranged randomly. Further more, Phoebe bournei was the dominant tree species, which had advantages in competition. All of these elements composed the ideal spatial structure.(4) According to diameter at breast height, Phoehe bournei was divided into three period of growth- big tree(20 cm?DBH)?middle tree(10 cm?DBH<20 cm) and small tree(5 cm?DBH<10 cm). All of the overall association between Phoehe bournei in different periods and other tree layer species was not significant. The correlation ratios of 105 species pairs formed of Phoehe bournei in three different period of growth and other tree layer species were 0.86, 0.76 and 0.69 respectively. Its tested significant rates were 11.43%,8.75% and 5.71% respectively, which showed middle tree was lower than big tree but higher than small tree in both aspects. So, concluded that the interspecific association between different species was loose and forest community was on a unstable developing stage.