关键词: 兴安落叶松, 空间分布格局, 尺度, 白桦

Abstract: To study the effects of nitrogen (N) addition on the plant and soil C∶N∶P stoichiometry is of significance in understanding the responses of ecosystem biogeochemical cycling to elevated N deposition. In this paper, a field experiment was conducted in a desert steppe of Ningxia to study the effects of N addition on C and N concentrations in green leaves of Agropyron cristatum, Stipa capillata, Lespedeza potanimill, and Cynanchum komarovii, and C, N and P concentrations in soil, with the relationships between the N limitation related plant and soil stoichiometry analyzed. The results showed that with the increasing amount of N addition, the community aboveground biomass and species individual biomass all decreased after an initial increase. The C concentration in the green leaves of the four species had no obvious variation pattern, the N concentration in the green leaves of the four species except A. cristatum had a significant increase, while the C∶N ratio in the green leaves of L. potanimil and C. komarovii decreased significantly. The soil total N content increased significantly, while the other soil indices had no significant responses to N addition. The individual biomass of C. komarovii had positive correlations with soil N and N∶P ratio, the N concentration in green leaves of A. cristatum and C. komarovii was positively correlated with soil N, while the C∶N ratios in the green leaves of S. capillata and C. komarovii were negatively correlated with soil total N. Our results indicated that shortterm N addition had little effects on the soil C∶N∶P stoichiometry but relieved the N limitation of plant growth in desert grassland to a certain extent, and thus, increased the N uptake by green leaves, promoted the biomass accumulation of plant, and improved the leaf litter decomposition quality. These species-specific responses not only reflect flexible adaptation to environment change, but also mean that long-term elevated N deposition may change the structure of desert steppe ecosystem.

Key words: Larix gmelinii, spatial distribution pattern,  , Betula platyphylla, scale.