Study On Hydrologic Adaptation Response Of Plants And Its Stable Isotope In Karst Rocky Desertification

The problem of karst rocky desertification was attached importance in 1990's, which represents a unique rocky desertification ecosystem in humid area. Desertification often results in a dysfunctional system in which the mean residence time is reduced for resources entering the ecosystem or being produced by it. The degraded process of the vegetation structure and functions changed by the rocky desertification were in relation with water, the key limiting factor. The plant water use strategies were examined by stable isotope and plant ecophysiology techniques. Along a water gradient, the competitive and adaptive strategies of plant were discussed.By the analysis of the characters of plants and environment of a small drainage basin in the hot valley of Huajiang area, we get the conclusions as bellow:1. Implication of karst rocky desertification on the environmental background(1) On the basis of measurement for microclimatic parameters, once the desertification occurring, followed the order of strong (ST)> medium (M) > slight (SL) > latent (L), owing to the decrease of the coverage and degeneration of adjustment of vegetation.(2) The layers of the synusia were no significantly different in the community. The coverage of the vegetation is different in the degree of desertification. There were no dominant species in all the community. Co-occurrence of plant species among communities at different grade desertification was analyzed, for species of trees or all the species as a whole, co-occurrence of plant species between the plots of latent desertification was the highest. The valley values of co-occurrence of plant species among communities along environment gradient were between the L-SL and SL-M, the results showed that turning point of plant species compositions at the types. The above ground biomass and the gross per annum were significantly different. The coefficient of variability of biomass in different degrees followed the order of L>M>ST>SL, showed the highest stable community was the latent one contrast with the unstable slight plots. Species abundance, species richness, total diversity and species evenness were significantly different. In general, most of the diversity index showed a decrease trend. The abundance takes the order of L>SL >ST=M. The lowest equitability (species evenness) occurred in the slight community, which can describe the low community stability. The β _W diversity in plant communities along the...