不同载畜率下短花针茅和土壤生态化学计量特征研究

以荒漠草原建群种短花针茅为研究对象，分析不同载畜率（对照，CK；轻度放牧，LG；中度放牧，MG和重度放牧，HG）对短花针茅与其对应土壤（0~20 cm和20~40 cm）碳（C）、氮（N）、磷（P）及化学计量比的影响。结果表明：放牧对短花针茅N、P及C∶N∶P化学计量比没有显著影响，但C含量随载畜率的增加而显著增加（P<0.05）；除表层土壤C∶N外，载畜率对两层土壤的N、P及C∶N∶P化学计量比有显著的影响（P<0.05），这些差异主要由土壤N和P的变化决定，但不同土层下载畜率间的化学计量特征没有一致的变化规律；整体上看短花针茅化学计量特征不受土壤化学计量特征变化的影响，放牧具有降低短花针茅P和土壤C的作用，但这种作用随载畜率的增加而降低。相比不放牧处理，重度放牧完全改变了土壤N、P、C∶N和短花针茅C、C∶N特征，而土层深度的加深对MG处理下的土壤P、N∶P和C∶P影响较大。

Stocking rate effects on stoichiometric characteristics of the steppe grassland pioneer species Stipa breviflora and its underlying soil

We investigated the effect of stocking rate(Control,CK;Lightly grazed,LG;Moderately grazed,MG and Heavily grazed,HG)on carbon(C),nitrogen(N),phosphorus(P)and their stoichiometry for the pioneer species Stipa breviflora(Sb)and its underlying soil for the 0-20 and 20-40 cm depths in desert steppe grassland.Stocking rate had no significant effect on N,P content and no effect on C∶N∶P stoichiometry in Sb foliage,but C content in Sb foliage significantly increased with increase in stocking rate(P<0.05).Soil N,P and C∶N∶P values for the two soil layers were significantly(P<0.05)affected by stocking rate,except for soil C∶N from 0-20 cm.Those differences between C∶N∶P ratios were mainly caused by the changing of soil N and P content,and these effects for the two soil layers were somewhat random with no consistent pattern across stocking rates.The stoichiometry of Sb foliage was not affected by changes in soil stoichiometry.Grazing decreased the Sb P and soil C content,but this effect was decreased by increased stocking rate.Compared with CK,HG markedly changed the characteristics of soil N,P and C∶N and of Sb foliage C and C∶N.The increasing of soil depth showed greater impact on soil P,N∶P and C∶P under MG.