高寒草甸冷季放牧对凋落物分解及C、N、P化学计量特征的影响

摘要

为深入理解放牧对青藏高原高寒草地冷季牧场凋落物分解及C、N、P化学计量特征的影响,本研究分析了不同放牧强度下冷季牧场凋落物现存量及C、N和P化学计量特征动态.结果表明,凋落物现存量随着放牧强度的增加而减少,轻度(22.50个羊单位·hm-2)、中度(26.25个羊单位·hm-2)、重度(32.04个羊单位·hm 2)放牧草地凋落物现存量依次为45.72～125.52、17.32～56.6、8.64～30.96 g·m-2.放牧季随时间推移各放牧强度下现存凋落物的C含量逐渐降低,同一时期现存凋落物C含量依次为轻度放牧＞中度放牧＞重度放牧.在休牧期,随时间推移,中度和重度放牧的凋落物C含量呈显著增加趋势.放牧期,凋落物N含量随时间推移呈下降趋势.放牧期,同一时期现存凋落物P含量均表现为重度放牧＞中度放牧＞轻度放牧;而休牧期,同一时期现存凋落物P含量均表现为轻度放牧＞重度放牧＞中度放牧.重度放牧下,草地现存凋落物C/N均在90以上,休牧初期(7月)草地现存凋落物C/P较高,均在1 000以上.综合得出,随着放牧强度的增加,凋落物损失率显著增大,N含量降低,C含量变化不显著,P出现富集.%To understand the effects of grazing on litter decomposition characteristics during the cold season in the alpine grassland of Qinghai Tibet Plateau,biomass and C,N,and P chemical measurements of litter in the cold season pasture under three different grazing intensities were studied.The results showed that the amount of litter decreased with an increase in grazing intensity.In light grazing (LG,22.50 sheep unit · ha-1),moderate grazing (MG,26.25 sheep unit · ha 1),and heavy grazing (HG,32.04 sheep unit · ha-1) alpine meadows,the litter biomass ranged from 45.72 to 125.52,17.32 to 56.6,and 8.64 to 30.96 g · m-2,respectively.The C content of the existing litter under different grazing intensities gradually decreased during the grazing season,and the C content of litter decreased in the order of LG,MG,and HG during the same period.In addition,the C content of litter showed a significant increasing trend in MG and HG during the rest from grazing period.The content of N in litter decreased during the grazing period,whereas the P content of the litter decreased in the order of HG,MG,and LG.During the rest from grazing period,the decreasing order of P content in the existing litter was HG,LG,and MG.The C/N of existing litter was above 90 in LG,and the C/P of existing litter was higher during the early rest from grazing period (July),which was greater than 1 000.The results from the present study demonstrated that litter loss rate increased significantly,N content decreased,C content did not change significantly,and P content appeared enriched with an increase in grazing intensity.