高寒草甸土壤有机碳和全氮变化对牧压梯度的响应

摘要

In order to understand the response of soil carbon and nitrogen to grazing intensity,the variation of soil organic carbon density (SOCD) and soil total nitrogen density (STND) under grazing gradients (CK),light grazing (LG),moderate grazing (MG) and heavy grazing (HG)) were measured and analyzed in Haibei alpine meadow during growing season.The results showed that both the SOCD and STND had a "V" quadratic curve relationship (P＜0.05) to grazing gradients,which indicated that CK could enhance the SOCD and STND and the turning point was 7.5 sheep per hectare.SOCD of CK、LG increased gradually in the growing season,while MG and HG reached to maximum in July and then decreased.STND appeared a "И" variation.SOCD and STND reduced gradually with the increase of soil depth.SOCD and STND had a significant positive correlation.The soil C/N increased gradually in the growing season under different grazing gradients and decreased with the soil depth.Grazing intensity could change the SOCD and STND,but it might not change the C/N.%针对高寒草甸土壤碳氮变化对牧压梯度的响应,以青海海北高寒草甸为研究对象,监测分析了禁牧(对照,CK)、轻牧、中牧、重牧试验地土壤有机碳密度、土壤全氮密度的变化特征.结果表明:SOCD和STND均与牧压梯度呈“V”形二次曲线关系(P＜0.05),说明禁牧可增加SOCD和STND,但放牧强度约高于7.5只羊·hm-2时存在由低向高的一个阈值转折点.同一放牧梯度上0～40 cm的SOCD均表现出5月最低,升至7月后,CK、LG到9月持续升高,而MG、HG有所下降,而STND自5月到9月表现为“И”型波动变化规律.随着土层深度加深SOCD和STND下降明显.不论是季节变化还是垂直变化,SOCD和STND相互间均呈显著的正相关关系(P＜0.05).C/N随生长季延长逐渐增加,随土层深度的加深而降低,放牧梯度并未改变土壤C/N的变化趋势.