Spatial Structure And Competition Characteristics And Simulated Logging Evaluation Of The Secondary Poplar-birch Forest In Taoshan Forest Farm

The secondary poplar-birch forest is one of the main secondary forest types in north mountain of Hebei, based on the research of structure and competition characteristics of the cutting solution is of great significance for the further optimization of forest management technology system.The research work taked three different species composition of secondary poplar-birch forest as the research object in Taoshan forest farm of Mulan national forestry administration in Hebei Province,set the50m×50m plots to conduct field investigation in July2012. Taking the method of neighboring trees structure unit, from the individual, population and stand three levels,using spatial structure parameters (mingling degree,uniform angle index,neighborhood comparison and open comparison) combined niche characteristics and Hegyi competition index, quantitative analysised the spatial structure characteristic and competition situation of the secondary poplar-birch forest. On the basic rational description of stand spatial structure, using Winklemass space structure analysis software to simulate the cutting on the different levels, adjust the forest stand structure, and then provide the theoretical basis for adjusting the unreasonable stand structure and sustainable management of the secondary poplar-birch forest in north mountain of Hebei. The main findings are as follows:(1) The species composition of S-1:6Betula platyphylla+3Populus davidiana+1Be tula dahurica, the species composition of S-2:5Betula platyphylla+5Populus davidiana+Betula dahurica,diametet distribution was similar to normal distribution. The species composition of S-3:10Betula platyphylla, diameter distribution was twin peaks shape curve. Betula platyphylla occupied the largest basal area proportion in each stand,was the constructive species and dominant species.(2) The analysis of spatial structure showed that:the stand average mingling degree of S-1was0.395,bad mixed; the stand average mingling degree of S-2was0.430,better than S-1; the stand average mingling degree of S-3was0.083,mixed worst; correlation analysis showed that the mingling degree and the proportion of Betula platyphylla and Populus davidiana in each diameter class were of negative correlation. The neighborhood comparison of S-1, S-2and S-3were0.488,0.498and0.512,basically in a moderate condition; Betula platyphylla, Populus davidiana and Betula dahurica occupied dominant position in spatial structure unit; the neighborhood comparison decreased with increasing diameter at breast height(DBH). The uniform angle index of S-1was0.482, belong to the random distribution; the uniform angle index of S-2was0.469, belong to the uniform distribution; The uniform angle index of S-3was0.532, belong to the aggregative distribution. The open comparison of S-1and S-2were0.772and0.775, they were in the open light environment; the open comparison of S-3was0.638,it was in the light environment between medium and open; Betula platyphylla and Populus davidiana occupied dominant position in light utilizing and light competition; the open comparison increased with increasing diameter at breast height; correlation analysis showed that species neighborhood comparison and open comparison were of negative correlation in each stand. The average distance between reference tree and neighboring trees in spatial structure unit were1.846m,2.006m and1.747m; most neighboring trees appeared within the distance of3m,mainly concentrated within the distance of2m,which showed that the competition between trees was intense. Space isolation degree of forest, the spatial distribution pattern and forest spatial structure unit distance mainly connected with the percentage and their biological characteristics of Betula platyphylla in each stand.(3) The aspect of trees competition:The average competitive intensity of S-1, S-2and S-3were4.971,3.818and8.093; intraspecific competition constantly occurred in the growth process of Betula platyphylla, the competitive intensity to Betula platyphylla decreased with increasing diameter at breast height; the competition strength from Betula platyphylla to other tree species had certain differences,which mainly connected with the percentage,growth characteristics and niche characteristics of Betula platyphylla in each stand.(4) On the basic rational description of stand spatial structure, taking create the best stand structure as the target, using the structured forest management methods, set four simulation cutting solution, to adjust horizontal distribution pattern, composition of species, and competitive relationship of the secondary poplar-birch forest, and also evaluate the effect of adjustment results in many ways. The evaluation results showed that, the average mingling degrees,open comparison and the distance of spatial structure unit have increased in varying degrees;the average competitive intensity of each stand had decreased, reduced the competitive pressures and increased nutrition space of the remaining trees. Comprehensive analysised, the suited simulation cutting solution of S-1, S-2and S-3were cutting30%,20%and40%from the original number.