The effects of nutrient addition on plant species diversity in desert grassland, Xinjiang, northwest China

Fertilization (CK, N, P, K, NP, NK, PK, NPK) and watering (CK, rain, snow) were applied to a desert grassland of northwest Xinjiang, China. Results showed that: (1) After nutrient and water additions for one year, the plant community structure changed, the individual number of Graminoids increased significantly, while the individual number of Cruciferaes decreased sharply. The total species number was 16 before the treatment and 10 after the treatment, reduced by 37.5%. (2) The vegetation coverage above ground and the plant density increased significantly under the additions of NP and NPK (p < 0.05), while the other nutrient additions had no significant effects on the vegetation coverage and density. Neither additional snow addition nor rain had significant effects. (3) Compared with the control (CK), the additions of N, P and PK increased the diversity indexes (D & H′) and Evenness (J); the additions of K, NP, NK and NPK decreased the diversity indexes (D & H′) and evenness (J). However, neither of the treatments has significant effect on the diversity indexes and Evenness based on the ANOVA (p < 0.05). (4) Snow significantly decreased the plant species richness (p < 0.05). However, neither the rain nor the nutrient addition has significant effect on the species richness. (5) The inter-annual variation trend of the diversity indexes (D & H′) and Evenness (J) showed an increasing trend during 2009–2012.