The Influence Of Mowing And Grazing On Plant Community Characteristics And Soil Nutrients In Stipa Grandis Steppe

The vegetation type of Stipa grandis +Leymus chinensis was used to examine the influence of mowing and grazing on vegetation characteristics, plant diversity and soil nutrients with the line transect method in order to understand the influence of two utilizing ways and to supply basic data on grassland use. The main results show as follows:1 The plant community height and above-ground biomass under two different uses on the grassland were significantly different (P<0.05), whereas the community density and the coverage showed no difference (P>0.05). Species composition showed no obvious difference:hay field had 22 families,45 genera and 60 plant species, and grazing area was of 20 families,46 genera and 62 plant species. However, species composition changed, for example, some annual forbs species with drought tolerance were present in grazing area and not in mowing area.2 The important value in grazing area regarding Cleistogenes squarrosa, Carex duriuscula and Potentilla acaulis were significantly higher than the ones in mowing area (P<0.05). Nevertheless, in grazing area, the important value of Serratula centauroides, Artemisia scoparia and Allium bidentatum were significantly lower than those in mowing area (P<0.05).3 The Shannon-Wiener index (H’), Simpson index (D) and evenness index (JP) showed a similar trend under grazing and mowing. Both richness indices (Ma,Pa) and evenness index (EA) displayed significant difference between the two use areas. Overall the grazing activity seems to have some impact on the plants development but the plant diversity is not more influced by grazing than mowing. According to the results of the study, the activity of mowing, in similar conditions, did not present a significantly negative impact on the grassland.4 The soil organic matter in 0-5cm layer of soil under these two different uses were significantly different (P<0.05), whereas the soil total carbon and the total nitrogen between 0-30cm layers showed no difference (P>0.05). In the 0-5cm layer of the soil, the content of available nitrogen in grazing area was higher than that in mowing area, higher around 10.27 mg/kg. The available potassium in the 0-10cm soil layer was significantly different under two using types of grassland (P<0.05). However, the available phosphorous had no difference with the two type of use of the grasslands. In the 20-30 cm layer of the soil, the pH in the grazing area was significantly higher than in the mowing area (P<0.05).5 Except the Perennial grasses, the above-ground biomasses of the other three function groups such as Perennial forbs, Annual and biennial and small-half shrubs etc. in mowing area were significantly higher than these in grazing area (P<0.05); The important value of the four function groups showed no difference (P>0.05). There were significant correlation between above-ground biomass, density of plant community with soil total nitrogen, available phosphorous and soil water content. The relashionship between soil total nitrogen, total carbon and available phosphorous had significant effect on plant community coverage.