降水量对荒漠草原植物群落多样性和C:N:P生态化学计量特征的影响

基于2014年在宁夏荒漠草原设立的降水量变化的野外模拟试验平台(年均降水量减少50%、减少30%、增加30%、增加50%以及对照),研究了植物群落多样性和C:N:P生态化学计量特征的变化,并分析了二者间的关系。结果表明,减少降水量降低了白草(Pennisetum centrasiaticum)种群生物量,但对其他物种种群生物量和群落生物量无明显影响。适量增加降水量促进了多数植物生长,提高了Shannon-Wiener多样性指数和Patrick丰富度指数。但过量增加降水量抑制了苦豆子(Sophora alopecuroides)和猪毛蒿(Artemisia scoparia)生长、降低了Shannon-Wiener多样性指数;减少降水量对植物群落C:N:P生态化学计量特征影响较小。增加降水量降低了植物群落全碳、全氮和N:P;植物种群生物量与植物群落C:N以及土壤含水量存在较强的正相关关系,与植物群落全氮和全磷存在较强的负相关关系。植物群落多样性指数与土壤含水量、植物群落C:N以及土壤C:N存在较强的正相关关系,与植物群落全氮、全磷以及N:P存在较强的负相关关系。以上结果表明改变短期降水量荒漠草原植物群落组成不仅与土壤水分有效性密切相关,而且受植物N和P摄取能力的调控。

Effects of Precipitation on Plant Community Diversity and C:N:P Ecological Stoichiometry in a Desert Steppe of Ningxia,Northwestern China

In this study,changes in plant community biodiversity,ecological stoichiometry of C:N:P,and their relationship were explored based on a simulated precipitation field experiment in the desert steppe of Ningxia,northwestern China in 2014,which involved five precipitation treatments(30%and 50%reduction in annual mean precipitation,30%and 50%increase in annual mean precipitation,and natural precipitation).The results showed that lower precipitation decreased the population biomass of Pennisetum centrasiaticum,whereas it had no effect on the population biomass of other species and community biomass.An appropriate elevation of precipitation stimulated the growth of most species and increased Shannon-Wiener diversity and Patrick richness indexes.In contrast,excessively increased precipitation resulted in sharp decreases of biomass of Sophora alopecuroides and Artemisia scoparia as well as Shannon-Wiener diversity index.Reduced precipitation had no influence on C:N:P ecological stoichiometry of plant community.However,increased precipitation decreased total C and N concentrations,and N:P of plant community.Plant population biomass had close positive correlations with C:N of plant community and soil water content,whereas it had close negative correlations with total N and P concentrations of plant community.Plant community diversity had close positive correlations with soil water content,C:N of plant community,and soil C:N,whereas it had close negative correlations with total N and P concentrations of plant community,and N:P.It can be concluded that the composition of desert steppe plant community is not only closely related to soil water availability but also regulated by N and P intake capacities of plants under short-term changed precipitation regimes.