Stand spatial structure characteristics of Pinus tabuliformis natural forest

In order to provide theoretical support for optimizing the stand spatial structure, it is necessary to analyze and evaluate the stand spatial structure of Pinus tabulaeformis natural forest in the nature reserve of Lingkong mountain.

Taking the natural P. tabulaeformis forest in the nature reserve of Lingkong mountain as the research object, five spatial structure parameters (Uniform angle index, neighborhood comparison, mingling index, storey index and open degree of stand) were selected to analyze the spatial structure characteristics of the natural P. tabulaeformis forest, the entroy weight methods were used to construct a comprehensive index of spatial structure for hierarchical evaluation of spatial structure.

The mean uniform angle indexes of the natural P. tabulaeformis forests were between 0.54 and 0.66. The spatial pattern was mainly clustering distributions. The mean mingling degree on sunny slope was 0.20, indicating that the overall stand was in weak mixed state, and those on the other slope aspects were belonging to the intermediate state of moderate and intensity. Stand neighborhood comparisons were between 0.35 and 0.50, the overall stands were closed to moderate neutral state. Stand layer index averages were between 0.29 and 0.41, and the average on shady slope was higher than that on sunny slope, stand layer structure was relatively simple, but the structure on shady slope was complex than that on sunny slope. The open degree of mean values were between 0.37 and 0.52, indicating that the light condition of entire stand was overall good, but light conditions of 50% trees of P. tabulaeformis on semi-shady slope and sunny slope were constrained. The comprehensive index of stand spatial structure was between 0.313 5 and 0.543 5, the evaluation grades of spatial structure were 2 and 3. The comprehensive indexes of P. tabulaeformis on semi-shady slope and Quercus wutaishanica on sunny slope were 0.283 6 and 0.253 3 respectively, and their evaluation grades were 2.

The spatial structure of the natural P. tabulaeformis forest in the nature reserve of Lingkong mountain was not very well, and need to optimize the stand spatial structure. Structural readjustments of P. tabulaeformis on semi-shady slope and Q. wutaishanica on sunny slope were urgent. The comprehensive index of spatial structure can be used as the basis of the structural adjustment of P. tabuliformis natural forest.