Abstract: As a low- efficiency forest, defective forest has worse forest form and ecological stability, resulting in poor landscape and ecological function. By sample-plot survey method, we analyzed the main defective communities forest and the species diversity in different site conditions of Jiufeng Forest Park for the forest form transformation technology after studying its structure and function of ecosystems. The defective degree of each community type of defective forest in Jiufeng National Forest Park was different, the order of species diversity was as follows: Chinese pine plantation>Robinia pseudoacacia plantation>Acer mono and Prunus mixed plantation>Shrub and grass plantation>Oriental Arborvitae plantation>Quercus variabilis plantation. In different site, in terms of the distribution of defective forest, the impacts of slope and soil conditions is more obvious, and the order of species diversity were slope>semi-shady slope>sunny, thick soil layer>thin soil, with the non-obvious effects in shrub layer. The typical characteristics of Jiufeng defective forest is lack of trees and grass, and in the specific performance the forest form of tree layer is dilapidated and herb layer coverage is low population differentiation. The population with wider niche may have a higher degree of overlaps, however, this situation is not certain, and the frequency distribution is an important factor affecting the degree of overlap of species. Therefore, the diversity of relict forest species has great difference with common forest species, and the different stand of the defective degree, serious differentiation, single species and poor site conditions are the main reasons for the formation of relict forest.

Key words: Jiufeng, defective forest, species diversity, site conditions, niche