| Gansu Wapiti (Cervus ealphus kansuenswas) plays an important role in the alpine grassland ecosystem in Qilianshan Mountain. On the base of comprehensively studying the soil, vegetation and wapiti of the Sunan Deer Farm, the dynamics of soil and vegetation with the different grazing pressure in the overgrazed winter pasture (WP) and the relatively light-grazed spring- autumn pasture (SAP) of Gansu wapiti was paid more attention. It could be useful to find out the structural characteristics of grassland, the role of wapiti in the grazing system, the relationship between soil-vegetation-animal and to restore and reconstruct the degenerated grassland ecosystem. 1 Effects of Wapiti Grazing on Soil The increased grazing pressure reduced the content of water, total N, available N, available P, organic matter, total salt and mean ratio of C/N in soil of both WP and SAP, but increased the soil bulk density. There were a positive relationship between the density, depth, width of the trampled path, the number, dry weight of the feces and the grazing intensity and a negative relationship between the number of the left plant in path and the grazing intensity in WP. The soil with the relatively heavy grazing was less susceptive to trampling than that with relatively light one in terms of the relationship between the comprehensive index of trampling and the distance of site from the door of WP. The daily mean respiration and the capacity of regulating temperature of soil reduced while the grazing intensity rose in WP, but soil respiration in early morning increased in SAP which closely related to the coverage of community. The heavy grazing resulted in the discordance of spatial pattern between soil characters and root which was advantageous to the growth of the poisonous plants such as horse-drunken grass (Achnatherum inebrians) and the development of the degenerated community with horse-drunken grass as the dominant species. The topsoil and available P was more susceptive to grazing than subsoil and the other characteristics of soil respectively. iii The quality indices of both single factor and comprehensive factors rose as well as the suitability of soil resources (SSR) while the grazing intensity reduced. Basing on relationship between SSR and vegetation, the reasonable SSR, standing crop of herbage and ratio of palatable herbage were suggested to be 0.59, 190.58g/m2 and 99.03% respectively, in order to keep a healthful grazing ecosystem in Sunan Deer Farm. The clustering analysis could well showed the succession stages of soil in the wapiti grazing grassland. The reduced content of water and mineral elements, especially in topsoil, and the discordance of vertical distribution between the soil characteristics and root could play an important role in the degeneration of grassland as a result of overgrazing. 2 Effects of Wapiti Grazing on Vegetation Due to the decrease of grazing intensity of Gansu wapiti in winter, the photosynthetic active radiation, air temperature and vapor pressure difference in canopy of community declined, but the relative humidity in the middle and top of canopy rose; net photosynthetic rate (Pn) became low in shortflower needlegrass (Stipa brevalora) and common aneurolepidium (Leymus secalinus), but high in horse-drunken grass; the apparent quanta efficiency, the temperature of leaf and reproductive branch and...
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