Study On Spatial Structure And Optimization Of Natural Secondary Forest Stands In Mountainous Area Of Northern Hebei Province

Polar-Birch secondary forest stands is the most common type of forest stands in northern mountain of Hebei province, the native species there is larch. At present, there are several problems for Polar-Birch secondary forest:bad growth conditions, ecological dysfunction, low biodiversity and serious pest problems, all of the problems makes Polar-Birch secondary forest stands can not give full play to the function of the forest. In this study, taking the mixed forest of different mixed degree as the object of study, using the structured forest management theory, analyzing the the composition of the dominant populations, diameter distribution and spatial structure, the method of structural adjustment is studied. The main research results are as follows:(1) There are10kinds of main species in the study area-north ditch Secondary Forest tree layer species, according to the analysis of the number of trees ratio, aspen and birch are taken as the dominant species which occupy the absolute proportion; while according to the basal area analysis, birch, aspen and North China larchas are taken as the dominant species.(2) The analysis of the tree number of different diameter classes of different forest types showed that the forest stand density is relatively large, the most trees are in the small diameter class and the growth is poor. Diameter class-strains curve presents anti-"J", unimodal and multimodal.Fitting four stands with negative exponential distribution, only one stand diameter structure is irrational distribution, q value is less than1.2. The hierarchy layer of the four kinds of forest types is above2, and the layer is relatively obvious, natural regeneration is good.(3) In addition to the stand B belongs to random distribution, the other three forest types belong to group distribution; stand D occupies dominant positioning in the competition of the top of species in forest stand, while the rest3stands are in the low position and take a disadvantage in the competition; stand A belongs to the weak mixed degree and need to be adjusted, the other three stands belong to moderate mixed. Comprehensive analysis manifest that the space distribution features of four forest types are poorer, parameter values generally are beyond the reasonable scope, it is necessary to take measures to adjust.(4) The formation of the primitive forest experienced a long evolution process, thus, it is difficult to make the existing stands in the study area reach the top status just by a simple operation, indeed, it is a long-term process of management.