Abstract:

In order to comprehend the sustainable developmental potential of Robinia pseudoacacia plantation in different habitats in Loess hilly region, diameter classes, species diversity, the soil moisture and nutrient were analyzed based on an investigation of R. pseudoacacia community in Zhifanggou and Liulinzhen of Yan’an Regions. The forests were planted 10, 25 and 40 years ago on the sunny and shady slope. The results showed that R. pseudoacacia plantations reached mature stage in 25 years, and the average diameter, height, understory species diversity, the soil moisture and nutrient reached stable state on both the sunny and shady slope. Height, diameter as well as other parameters, which reflect environment quality, increased quickly, but they did not show obvious increase after 25 years. On shady slope, the trees grew better and had adequate regenerated seedlings, there was rich species in the community, the soil moisture and nutrient were relatively abundant, and in general the R. pseudoacacia community had sustainable developmental potential. On the contrary,on sunny slope, the individuals were maldevelopment, there was no enough seedlings and lower species diversity in the community, the soil moisture and nutrient were relatively deficit, R. pseudoacacia community did not have sustainable developmental characters. In the future, it should be avoided to plant R. pseudoacacia on the sunny slope, and transformed the existing R. pseudoacacia plantations into R. pseudoacacia -sparse shrubs plantations in the loess region. In order to stimulate the regeneration of seedlings and promote the community evolving into an uneven-aged stand, some ungraded woods and diseased woods should be removed in the R. pseudoacacia plantations over 25 years old on shady slope. During the thinning process, the shrub layer should be protected by which the community complex structures are consummated to improve the ecological benefit.

Key words: loess hilly region, locust tree (Robinia pseudoacacia) plantation, different stages of recovery, community stability, natural development