青海湖地区紫花针茅型中度与重度退化草地地下植物量的比较研究

Study on comparison of underground phytomass of Stipa purpurea steppe under moderate and heavy degradation

对青海湖地区紫花针茅型中度与重度退化草原地下植物量进行了比较研究，结果表明，中度与重度退化样地地下植物量的季节积累动态并不相同，随着退化程度加重，在草地植物地上部枯黄之前，光合产物向地下部的运转减少，根部贮藏的营养物质减少，地下与地上植物量的比值随退化程度的加重而增大。两个退化样地地下植物量的80％分布在0～20cm土层，用y—ax^b能够很好描述中度与重度样地在生长季各土层平均分布的植物量及其所占比例。在40cm深的土层中，中度与重度退化样地地下植物量每年的净生产量分别为849．6g／m^2、1346．05g／m^2；周转值分别为32．45％、51．93％。

Abstract： The underground phytomass of Stipa purpurea steppe under moderate and heavy degradation around Qinghai Lake was studied and the results showed that seasonal dynamics of phytomass in heavy and moderate degraded plots varied. Before withering stage of vegetation, the amount of photosynthate transferred to un- derground decreased and it aggravated With the degraded degree of grassland. More than 80% of underground phytomass distributed within 0 to 20 cm soil layer. The average phytomass and its proportion in each soil layer could be described with y=ax^b in two degraded plots at growing period. Within 40 cm of soil depth,the net production of underground phytomass of moderate and heavy degradation of grassland were 849.6 g/m^2 · a and 1 346.05 g/m^2 · a respectively,and meanwhile,the turnover values were 32.45% and 51.93% respectively.