Abstract:

Sample plots with Pinus armandii as the constructive species or dominant species were selected for investigation in Nyingchi City,Tibet. Based on the calculation methods of Levins niche breadth,Shannon-Wiener niche breadth and Pianka niche overlap,the main plants in the shrub and grass layer under P. armandii forest were calculated and their niche characteristics were analyzed. The results showed that: 1) There were 7 species and 12 species of main plants in shrub layer and herb layer,respectively. In shrub layer,the important value of Syringa pubescens was the largest,and in herb layer,the important value of Fragaria moupinensis was the largest. 2) The species with the largest niche breadth in shrub layer were S. pubescens and Lonicera tangutica, and the smallest niche breadth was Lindera obtusiloba. In herb layer,the largest Levins niche breadth were F. moupinensis,Geranium wilfordii,and Malva sinensis, and the largest niche breadth of Shannon-Wiener were G. wilfordii and G. aparine var. Tenerum. The smallest was Sinopodophyllum hexandrum. 3) The species pairs with the highest overlap in shrub layer were Rosa macrophyllavar. Glandulifera and Berberis diaphana. The species pairs with the lowest degree of overlap were L. obtusiloba and R. macrophyllavar. Glandulifera.The species pairs with the highest niche overlap in the herb layer were Circaea alpina and G. aparine var. Tenerum,The species pairs with the lowest degree of overlap were S. hexandrum and Ophiopogon bodinieri. The competition intensity of herb layer was greater than shrub layer in P. armandii forest in southeast Tibet. The community species had strong utilization ability for resources,which had a certain impact on the growth and development of P. armandii seedlings. The growth conditions of seedlings could be optimized under the premise of maintaining species diversity.

Key words: niche characteristics, shrub layer, herb layer, Pinusarmandii forest, Southeast Tibet