Studies On Plant Community And Species Diversity Of Desert Steppe In Sandy Atea Of Eastern Ningxia

The desert steppe in sandy area of eastern Ningxia is an important ecological barrier and animal husbandry base of Ningxia, and it has changed a lot because of drought, ecotope fragile, vegetation was erosioned and human disturbance, etc. Thus it is significant to clear and definite the actually of vegetation community types of desert steppe in eastern sandy area and know the changes of soil and vegetation to manage the steppe scientifically. This paper focused on the subject of desert steppe in sandy area of eastern Ningxia, it definited the types of plant community through the investigation and measure by using Twinspan number classification; it compared the different degrees of degradation of vegetation and the changes of physicochemical and biological properties of soil. It studies the variety of phytocenosis of the desert steppe. It used Canoco ranking method for analysis the relationship between the distribution of plant communities, the species and the soil properties. The main conclusions as follows:(1)According to the number of TWINSPAN classification, combined with "Chinese Vegetation" classification principle, the desert steppe plant communities type in sandy area of eastern Ningxia was divided into eight branches, that was, Lespedeza potaninii, Pennisetum centrasiaticum, Sophora alopecuroides, Leymus secalinus, Stipa breviflora, Glycyrrhiza uralensis, Artemisia frigidal community, and Nitraria tangutorum community.(2)The important value of dominant species in each community were higher, the community coverage showed that the Artemisia frigidal community was the highest; the aboveground biomass was significantly different (P<0.01). The results of DCCA showed that the distribution of communities affected by soil moisture, clay, organic matter and available phosphorus content greater impact, the soil moisture played a decisive factor that it influenced on plant community distribution in study area.(3)With the degree of degradation was being aggravated, the height, coverage, density, above-ground biomass of plant community and the richness, evenness and diversity index had trended down, the perennial species composition were reduced and the proportion of annual was increased; the highest of dominance was non-degraded grassland, moderately degraded grassland minimum; With the degree of grassland degradation intensifies, soil clay, moisture, organic matter content and the number of soil bacteria, actinomycetes, fungus and urease, polyphenol oxidase, protease, phosphatase, sucrase activity decreased change, but the bulk density increased; The performance of soil quality index in grassland was Non-degraded> light degraded> moderately degraded> heavily degraded, showed that desert grassland degradation in sandy area impact on soil physical, chemical and biological traits had relatively consistent.(4)The characters of coverage and biomass of vegetation communities in different degradation stages was more effected by soil available potassium, available phosphorous, actinomycetes; community species diversity was more effected by soil clay, moisture, available potassium.(5)Sandy desert steppe region was more single species, mostly concentrated in the 3-17 species; within the community less competitive species to reduce, the dominant species had higher important value. The species diversity in community was significantly difference(P<0.05);species richness effect on community diversity was more than uniformity.(6)Species diversity index and the soil moisture content, organic matter, urease, protease, invertase, bacteria were significantly positively correlated(P<0.05), with soil clay, potassium, available phosphorus showed a significant negative correlation(.P<0.05); richness index, evenness index and thermal index, wet bulb temperature was highly significantly positively correlated (P<0.01), with the humidity was a significant negative correlation (P<0.05). Canonical Correspondence Analysis results showed:when soil moisture, clay, organic matter and N, P, K were higher levels, vegetation species relative abundance.