Ecological Stoichiometry And Plant Community Diversity Of Different Plant Communities In Desert Steppe Of Ningxia

Ningxia desert steppe is the fragile ecosystem. Plant communities characteristics and ecological stoichiometry play an important role in this zone. In this study, six plant communities, i.e., Stipa bungeana, Agropyron mongolicum Keng, Glycyrrhiza uralensis Fisch., Cynanchum komarovii Al., Artemisia ordosica and Sophora alopecuroides were determined, an investigation on communities characteristics and ecological stoichiometry, including biodiversity index, communities and individual level ecological stoichiometry in different organs, which provided a scientific basis to rich the diversity of desert steppe. The results indicated:1. Desert steppe communities presented allometric growth patterns. The response curves of communities richness to aboveground biomass was unimodal, while biodiversity inhibited the ground biomass, but did not hold the underground biomass. Soil nutrients of different communities gradually reduced with the increasing of soil depth, which showed continuous reduction and had obvious "surface accumulation".2. The different organs and litters of different communities level, individual level in desert steppe were showed C> N> P, and the content of C, N, P of plants live leaves was higher than root. Leguminous plants leaf N was significantly higher than Gramineous plants N content (P< 0.05), Different plants had the different forms of C, N, P resources utilization.3. In desert steppe, the average content of carbon as well as nitrogen of plant leaf is lower than that of the global level, with an average content of 434.36 ±19.87 g·kg-1 and 18.94 ± 0.40 g·kg-1.Whereas the average content of phosphorus of plant leaf is higher than that of the global level, with an average content of 1.27 ±0.03 g·kg-1, which is lower than that of global level. And these results is closely related to the vegetative pattern and growth rhythm of plant leaf.4. The variable coefficient of different communities level, individual level in desert steppe was lower (<25%), while the variable coefficient of under-ground was higher than above-ground, which showed that plant nutrients in desert steppe was relatively stable. The content of N was significantly positive correlation with P (P< 0.01) in communities and individual level, which showed that the content of leaf nutrients was not affected by the content of C, and reflected the consistent demand of N, P and the better economic strategy of leaf properties.5. Correlation analysis showed that the C, N and P concentration of communities, individual level and litters of different plant communities was significant correlation with SOC, N and P of 0-5 cm soil layer, the correlation significantly weakened with soil depth, which showed that the C, N, P in different organs in desert steppe was absorbed in uniformity and flowing, also there were ecological niche differentiation and the trade-offs of the nutrition absorption capacity and resource allocation strategy.