放牧对荒漠草原克氏针茅种群和土壤生态化学计量特征的影响

该研究选取内蒙古荒漠草原,设计无牧区(NG)、中度放牧(MG)、重度放牧(HG)3个处理,测定分析不同放牧强度处理5年后,优势植物克氏针茅以及土壤的C、N、P营养元素的化学计量特征及其协同关系,以揭示放牧生态系统养分循环的影响机制,为区域草地的利用以及修复提供理论依据。结果表明:(1)轻度放牧下荒漠草原的物种多样性均显著高于中度和重度放牧条件(P<0.05)。(2)土壤中C、N含量以及C∶N、N∶P、C∶P,均随着放牧强度的增加呈先升高后降低的变化趋势,土壤P含量随放牧强度的增加而升高。(3)随放牧强度增加,克氏针茅地上部分C含量降低,N、P含量以及N∶P先升高后降低,C∶P则先减少后升高;克氏针茅地下部分的C、N含量以及N∶P一直呈增加的趋势,P含量先减少后升高,而C∶N、C∶P则是与P含量规律相反。(4)与地上部分各元素含量相比,克氏针茅地下部分各元素含量及其比值与土壤中各元素含量的相关性更高,说明放牧条件下荒漠草原优势植物的根系与其所处的土壤环境具有一定的协同变化能力。

Effects of Grazing on Ecological Stoichiometry of Stipa krylovii and Soil in Desert Grassland

This study selected desert grasslands in Inner Mongolia,and designed three treatments:no grazing(NG),moderate grazing(MG),and heavy grazing(HG).The stoichiometric characteristics and synergetic relationship of nutrient elements C,N and P of dominant plant S.krylovii and soil were analyzed after five years,to reveal the mechanism of nutrient cycling in grazing ecosystem and provide theoretical basis for the utilization and restoration of regional grassland.The results showed that:(1)the species diversity of desert grassland was significantly higher than that of moderate and heavy grazing(P<0.05).(2)The contents of C,N,C∶N,N∶P,C∶P in the soil all showed a trend of increasing firstly and then decreasing with the increase of grazing intensity,while the content of P in the soil increased with the increase of grazing intensity.(3)With the increase of grazing intensity,the contents of C in the aboveground part of S.krylovii decreased,and N,P,N∶P increased firstly and then decreased,while C∶P decreased firstly and then increased.The contents of C,N,N∶P in the underground part of S.krylovii have been increasing.P content firstly decreased and then increased,while C∶N,C∶P were contrary to the rule of P content.(4)Compared with the contents of elements in the aboveground part,the correlation between the content and ratio in the underground part of S.krylovii and the contents of elements in the soil is higher,which indicates that the root system of dominant plants in the desert grassland and its soil environment have certain cooperative change ability under grazing conditions.