Study On Spatial Structure Of The Secondary Poplar-birch Forest In North Mountain Of Hebei

In north mountain of Hebei, the secondary poplar-birch forest is one of the main secondary forest types, which have been recovered after destroyed by logging, grazing and natural disasters.The secondary poplar-birch forest have a series of problems, such as poor growth condition, low ecological function, low biodiversity, serious pests and so on, so can not give full play to the functions of the forest. Therefore, through the study of spatial structure of the secondary poplar-birch forest, it can reveal the spatial structure feature of the secondary poplar-birch forest.Adjusting the species composition, population spatial pattern and competitive relationship to build the optimal space structure, improve the economic benefits and provide a theoretical basis for the sustainable management of the secondary poplar-birch forest by the means of structured forest management.Set the 100m×100m plots in selected typical secondary poplar-birch forest in Taoshan forest farm of Hebei, it is based on forest individual space location information, adjacent timberwork element method and point pattern analysis was used to analyze spatial structure and population distribution patterns, the space structure parameters angle stand scale, ratio of stand and mingling degree are used to adjust the structure of the dominant tree species community. The main findings are as follows:(1) The density of the secondary poplar-birch forest is 1162 plants/hm2, there are eight kinds of trees that their diameter is greater than 3cm. From the basal area of tree species unit area, the species composition of the standard places: 7 Betula platyphylla +2 Populus davidiana +1 Betula dahurica + Acer mono. Diameter distribution was similar to the anti-“J”shape. Through the 6 commonly used equations of tree height in accordance with changes in diameter, fitting the high curve of the tree and the effect is quite good. The best tree height curve equation is h = 1. 269747+1.011394×d?0.01731×d2(R2=0.76).(2) The analysis of spatial structure of the secondary poplar-birch forest in north mountain of Hebei shows that: at the stand, the stand average mingling degree is 0.567, the level between moderate and intensity mingling degree. All species are often mixed with two adjacent trees or more,species mixed greatly. The ratio of stand are well-distributed, Populus davidiana and Betula dahurica have a certain degree of dominance in the spatial structure unit. The dominant trees, subdominant trees are more than others, the ratio of stand of others are larger. The stand competition adjustment direction should expand the nutrition space of other species, reduce the pressure of competition, so as not to be furthest extruded by adjacent competition trees. The stand average angle scale is 0.555, and according to the criterion of the average angular scale, the tree horizontal pattern of the secondary poplar-birch forest in north mountain of Hebei is aggregated.(3) The secondary poplar-birch forest in northern mountain of Hebei community (0~50m) , is aggregated at small scale (0~33m) but randomly distributed at large scale (34~50m). Single species distribution pattern of Betula platyphylla, Populus davidiana and Betula dahurica are also aggregated at small scale, specific scale were 0~27m, 0~33m and 0~44m, but randomly distributed at large scale specific scale were 28~50m, 34~38m and 45~50m. Acer mono is aggregated at all scales of this research. Betula platyphylla is positively associated with Populus davidiana, Acer mono and Betula dahurica. Populus davidiana is positively associated with Acer mono and Betula dahurica at small scale but negatively at large scale. Acer mono and Betula dahurica are significantly positively associated with each other.(4) On the basis of the stand spatial structure, adjust the management structure of different age, stratified, mixed secondary poplar-birch forest as the final goal, create the best stand space structure as the key point, using the structured forest management methods to adjust the secondary poplar-birch forest’s horizontal distribution pattern, composition of species and competitive relationship, and also evaluate the effect of management results in many ways.The evaluation showed that, through the adjustment of community structure, the nutrition space of the remaining trees has increased and the competitive pressures have reduced, creating a good environment for the growth of the remaining trees.