Abstract
In order to clarify mechanism of pasture degradation a survey was carried out on distribution of vegetation types in connected with such environmental factors as relative ground level, pH and electric conductivity of soil in Wulanaodu, Inner Mongolia, the same region as the previous report. The results obtained were as follows. 1. It was observed in the grazing plot that Suaeda type distributed around bare ground at the low ground level and Aneurolepidium type disributed around Agropyron type at the highest ground level, and that between these circles Chloris type spread at the medium ground level. 2. Sequence of soil alkalinity of vegetation types was as follows ; bare ground > Suaeda type > Chloris type・Artemisia type・Puccinellia type > Aneurolepidium type > Arundinella type. It was considered that distribution pattern of vegetation types, which adapt to soil alkalinity, corresponding to relative ground level and soil alkali was a phenomenon of "habitat segregation". 3. These results indicate that soil alkalinity as well as over grazing are the main causes of pasture degradation, and suggest that decreasing soil alkali may improve degraded pasture vegetation. As for a measure for decreasing soil alkali, effects of proper use of pasture and the drainage of surface water is discussed.
