不同放牧方式下高寒草甸土壤碳组分的对比研究

高寒草甸具有重要的碳汇功能。在冷湿环境下,土壤有机质分解缓慢,碳库积累对区域碳平衡发挥着重要的作用。然而,高寒草甸土壤退化对人类活动异常敏感,研究土壤碳库变化对放牧干扰的响应,可以为深入揭示高寒草甸的退化机理提供科学依据。藏猪放牧是目前存在于我国海拔3 000~4 000 m地区的主要放牧形式之一,本文以滇西北高原湿地——纳帕海作为研究对象,对比分析了纳帕海高寒草甸上的牛羊与猪拱放牧对土壤碳库特征的差异化影响。研究表明,猪拱放牧较牛羊放牧降低了土壤总有机碳以及活性有机碳(高活性碳、中活性碳以及低活性碳)的含量。与其他碳库相比,中活性碳库对猪拱放牧的响应最为敏感,可以作为重要的干扰指示因子。猪拱放牧影响下,土壤微生物生物量碳含量小于牛羊践踏下的土壤微生物生物量碳含量。随着土层深度的增加,土壤碳存储量呈下降趋势,对放牧干扰的响应也逐渐减弱,表层土壤(0~10 cm)受放牧干扰的影响最大。在不同研究区域上,由于土壤理化性质的差异,与沼泽化草甸相比,陆生草甸对猪拱放牧的响应较大。冗余分析(RDA)进一步表明,土壤碳库与土壤含水率、容重与孔隙度等理化因子的变化密切相关。综上,土壤碳库改变与放牧方式、放牧区域以及土壤剖面深度有关,猪拱放牧导致土壤表层裸露并引起土壤结构发生变化,进而导致土壤有机碳含量显著下降。其生态破坏程度较牛羊放牧更为严重。

Study on Soil Carbon Fractions in Alpine Meadow Under Different Herding Patterns

Alpine meadow is important for carbon (C) sequestration. Under cold and humid circumstances, the decomposition of soil organic matter is relatively slow, and thus soil C accumulation plays crucial roles in maintaining regional C balance. However, soil degradation of alpine meadow is extremely sensitive to anthropogenic activities. The study on the response of soil C pools to herding can provide scientific basis for deepening the mechanism of alpine meadow degradation. Pig uprooting is one of the major herding forms at the altitude of 3 000-4 000 m in China. In this work, the northwestern plateau wetland (Napahai) was selected as the study area, and the differences in soil C pools between yak tramping and pig uprooting on alpine meadows in Napahai was analyzed. The results showed that the pig uprooting reduced the total organic C and labile organic C (highly labile organic C, medium labile organic C, and low labile organic C) when compared to the yak tramping. The medium labile organic C is the most sensitive to pig uprooting among all studied C pools, and thus can be used as an important ecological indicator for soil disturbance. The soil microbial biomass C under pig uprooting was lower than that under yak tramping. Along with increasing soil depth, soil C storage decreased, and its response to herding disturbance also decreased. While, topsoil (0-10 cm) was the most affected by herding. In different study areas, due to the distinct soil physical and chemical properties, soils in terrestrial meadows showed a greater response to pig uprooting when compare to swamp meadows. Redundancy analysis (RDA) further indicated that soil C pools was closely related to soil water content, bulk density, porosity and so on. Overall, the changes in soil C pools were associated with herding patterns, regions, and soil depths. Pig uprooting led to soil bareness and structural changes, which resulted in a significant decrease in soil organic C, thus may lead more severe damages to ecosystems when compared to yak tramping.