Abstract: Nitrogen (N), phosphorus (P), soluble carbohydrates (SC), and starch concentrations in leaves of two dominant grass species, Stipa grandis and Leymus chinensis, were examined based on a sevenyear nutrient addition experiment in a semiarid steppe in Inner Mongolia of China. The experiment included five treatments: control, low P, low N, low N + high P, and high N + low P. Results showed that N, P, SC, starch, and nonstructural carbohydrates (NSC) concentrations in leaves of the two plant species were significantly influenced by nutrient addition (P<0.05). A significant interaction effect (P<0.05) was observed between nutrient addition and plant species. Leaf N concentration was increased (P<0.05) for both plant species under the treatments with N addition; starch content was decreased (P<0.05) for both plants in the low N treatment; leaf SC in L. chinensis was decreased under the low P treatment; while NSC content in leaves of both species significantly decreased (P<0.05) with high N + low P addition. No significant response was observed for all variables in S. grandis leaf to P addition. The comparatively higher leaf C/N， C/P, and SC/starch in S. grandis implied more available carbohydrates and a higher use efficiency of S. grandis in N and P nutrients, while L. chinensis exhibited a competitively stronger feature of absorbing nutrients applied.

Key words: soil microbial community diversity., land consolidation, soil organic carbon