施肥对荒漠化草原草本植物种群密度和生物量的影响

通过外源施加N肥、P肥和N-P混合肥的试验，研究了荒漠化草原草本植物种群密度和生物量对不同肥料的响应，3种肥料均设置了0(对照)、5、10 g·m-2和20 g·m-2 4个投加水平。一年的研究结果表明：种群密度在3种肥料作用下均随着施肥水平的增大呈现逐渐降低的趋势，尤其是在高的N肥（20 g·m-2）处理下，优势种草本植物茵陈蒿（Artemisia capillaris）、多根葱（Allium polyrhizum）和冠芒草（Enneapogon brachystachyus）的密度及总密度均显著低于对照（p<0.05）;地上部及根部生物量在3种肥料处理下的响应同种群密度，即地上和根部生物量均随着施肥水平的增大而减小，其中，3种优势种草本植物的地上部生物量及总的地上部生物量随着施肥水平的增大均呈现出显著的负相关的关系，其决定系数（R2）均在0.80以上。可见，在荒漠区较低的降水条件下（年降水<180 mm），施肥会抑制荒漠草本植物的种群密度和生物量，且其抑制作用与肥料种类无关。

Effects of Fertilization on Population Density and Biomass of Herbaceous Plants in Desert Steppe

In order to investigate the impacts of fertilizer enrichment on population density and productivity of herbaceous plants in the desert steppe, N, P, and N-P addition experiments were performed. Each fertilizer treatment included four addition levels, i.e. 0, 5, 10, and 20 g\5m-2. The results indicated that population density decreased with the increasing fertilizer addition levels regardless of the sort of fertilization, and especially, the total density as well as the density of Artemisia capillaris, Allium polyrhizum and Enneapogon brachystachyus significantly decreased compared to the control at the condition of 20 g\5m-2 N added. Responses of aboveground and root biomasses to fertilizer enrichment were similar to that found in population density, both the total aboveground biomass and the aboveground biomasses for A.capillaris, A. polyrhizum and E. brachystachyus were negatively correlated with increasing fertilizer addition levels, with all determination coefficients (R2) greater than 0.80. Therefore, in the case of desert regions (annual precipitation <180 mm), fertilizer enrichment would inhibit population density and productivity of herbaceous plants regardless of the sort of fertilizer.