Spatial Structure Of Natural Secondary Mixed Forest In Huanglong Mountain

Natural secondary mixed forest is one of main forest types. Now the stand growthcondition is poor which cannot fully bring into play to the functions of the forest. It is eargentto adjust the stand structure, especially spatial structure. This paper determined standparameters such as the tree height, diameter, basal area, and the coordinate of each tree in a1hm2plot. The study described the spatial structural characteristics of plot-level stand ofnatural secondary mixed forest in Huanglong mountain using mingling degree, neighborhoodcomparison and uniform angle index. Single tree selection cutting measure was used to adjustthe structure of the stand. The main research results include the following:(1)The density of the natural secondary mixed forest was2452plants/hm2; there were17kinds of trees, and Pinus tabulaeformi was the only type of conifer specie; the speciescomposition of the stand was:3Pinus tabulaeformi3Quercus liaotanggensis3Betulaplatyphylla+1Acer ginnala+Populus simonii-Pyrus betulaefoli-Toxicodendronvernicifluum-Crataegi cuneatae, so Pinus tabulaeformi made up the dominant species,andQuercus liaotanggensis and Betula platyphylla were the other two main species. Diameterdistribution was similar to the anti-‘J’ shape. Trees were mostly belong to small diameterclass; most of trees’ height was middle,the relationship between tree height and diametercould bedescribe as the fitting equation which the Weibull modelwas: H1.313.5171e. D., sotheywere non-linear relationship.(2) Stand spatial structure analysis shows that：a)The mingling degree of whole standwas high and most of the woods were moderately, strongly and extremely mixed, and themingling degree of Pinus tabulaeformi，Quercus liaotanggensis and Betula platyphylla were0.51,0.71and0.69respectively; b)In the spatial structure unit, the number of neighborhoodcomparison evenly distributed, and it accounted the percentage of about20%.What’s more,the size of trees difference was not obvious, so the forest was stable. But each specie’saverage neighborhood comparison was between0.31and1,so there was a big difference inthe differentiation of space between species. Most woods were in bad state and absolute poorstate, and only a small part of them were superior trees. c) The average uniform angle indexwhich was0.5made up50%,so spatial structure unit which was random distributioncomposed the biggest percentage. Seen by each species, most tress were aggregativedistribution. The proportion of even distribution and uneven distribution were respectively16% and17%which were nearly the same. Quite uneven distribution only had a small percentwhich was just8%.The uniform angle index of the whole stand was0.545which meant thenatural secondary mixed forest of Huanglong Mountain was aggregative distribution.(3) According to the stand condition and basic stand structure including speciescomposition, diameter and height, along with the spatial structure, the stand should be takensingle tree cutting measure.And it made use of structure-based forest management to regulatethe horizontal distribution pattern, After initially and lastly identifying the cutting wood,altogether chose272trees. The cutting intensity was11%. The mingling degree of the standimproved; the neighborhood comparison didn’t change; the uniform angle indexdescreased,so the stand changed into random distribution.