Effects of fertilization on population density and productivity of herbaceous plants in desert steppe

In order to investigate the impacts of fertilization on population density and productivity on herbaceous plants in desert steppe, nitrogen (N), phosphorus (P), and N-P addition experiments were performed. Each fertilizer treatment included four addition levels, i.e., 0, 5, 10, and 20 g/m². The results indicated that population density decreased as fertilization levels increased regardless of the sort of fertilizer. More specifically, total density as well as density of Artemisia capillaris, Allium polyrhizum, and Enneapogon brachystachyus decreased significantly in 20 g/m² treated plots, as compared with the control plots. Fertilization effects on aboveground and root biomasses were extremely similar to that found in population density; that is, both total aboveground biomass and aboveground biomasses for A. capillaris, A. polyrhizum, and E. brachystachyus were negatively correlated with increasing fertilization levels, with all determination coefficients (R²) greater than 0.80. Therefore, in the case of desert regions (annual precipitation <180 mm), fertilization would inhibit population density and productivity of herbaceous plants.