不同放牧强度对呼伦贝尔羊草草甸草原土壤活性有机碳的影响

Effects of different grazing intensities on soil active organic carbon in Leymus Chinensis meadow steppe in Hulunbuir

土壤活性有机碳是土壤中较为活跃的化学组分,能反映土壤有机碳(SOC)的有效性,可作为土壤质量和肥力的指示性指标。研究探讨放牧干扰对羊草草甸草原土壤活性有机碳的影响,从而了解放牧对草地生态系统中碳循环的影响机制,旨在为退化草地生态恢复过程提供理论支撑。依托于呼伦贝尔草原生态系统国家野外科学观测研究站的长期肉牛放牧平台,分析6种不同放牧强度[不放牧(G0.00)、较轻度放牧(G0.23)、轻度放牧(G0.34)、中度放牧(G0.46)、重度放牧(G0.69)、极重度放牧(G0.92)]下羊草草甸草原土壤活性有机碳的变化,并探讨其相关性。结果表明:(1)土壤有机碳和活性碳组分的含量在不同土层间差异显著,随着土层深度的增加,SOC和活性有机碳[颗粒有机碳(POC)、可溶性有机碳(DOC)、微生物生物量碳(MBC)、易氧化有机碳(EOC)]含量均显著降低。(2)不同土层活性有机碳占比与放牧强度呈线性正相关,随着放牧强度的增加土壤活性有机碳占比也随之增加,不同放牧强度不同土层下土壤各形态活性有机碳占比呈POC>EOC>MBC>DOC的趋势,且EOC、MBC和POC占比随土壤深度增加而降低。(3)随着放牧强度的增加,植被群落地上生物量、地下生物量和土壤水分均呈下降趋势。(4)放牧强度与SOC和DOC呈显著负相关;植被群落地上生物量与土壤碳组分间呈显著正相关;地下生物量与DOC之间呈极显著正相关;土壤温度与POC呈显著负相关;土壤水分与POC呈极显著正相关,与SOC之间呈显著正相关。研究表明:放牧会降低地上生物量、地下生物量和土壤水分,适度放牧不仅能增加土壤有机碳和活性碳组分,而且能增加土壤活性碳占比,且符合中度干扰的假说。

Soil active organic carbon is a relatively active chemical component in soil,which can reflect the availability of soil organic carbon(SOC)and can be used as an indicator of soil quality and fertility.The effects of grazing disturbance on soil active organic carbon in Leymus chinensis meadow steppe were explored,so as to understand the effect mechanism of grazing on carbon cycling in grassland ecosystem,and improve theoretical support for the ecological restoration process of degraded grassland.Based on the long-term beef cattle grazing platform of the National Field Scientific Observation and Research Station of Hulunbuir Grassland Ecosystem,six grazing intensities no grazing(G0.00),slightly grazing(G0.23),light grazing(G0.34),moderate grazing(G0.46),heavy grazing(G0.69)and extremely heavy grazing(G0.92)were set up,to analyze the changes of soil active organic carbon in Leymus chinensis meadow steppe under different grazing intensities and explore its correlation.The results showed that:(1)The contents of soil organic carbon and active carbon were significantly different among different soil layers,and the contents of soil organic carbon and active organic carbon[Particulate organic carbon(POC),dissolued organic carbon(DOC),microbial biomass carbon(MBC)and easily oxidizable organic carbon(EOC)]were decreased significantly with the increase of soil depth.(2)The proportion of active organic carbon in different soil layers was linearly positively correlated with grazing intensity,and the proportion of active organic carbon in soil was increased with the increase of grazing intensity.The proportion of active organic carbon in different soil layers under different grazing intensity was POC>EOC>MBC>DOC,and the proportion of EOC,MBC and POC were decreased with the increase of soil depth.(3)With the increase of grazing intensity,the above-ground biomass,underground biomass and soil moisture showed a downward trend.(4)Grazing intensity was significant negatively correlated with SOC and DOC.There was a significant positive correlation between above-ground biomass and soil carbon components.There was a very significant positive correlation between underground biomass and DOC.Soil temperature was negatively correlated with POC.Soil moisture and POC showed a very significant positive correlation,and was positively correlated with SOC.This study shows that grazing can reduce above-ground biomass,underground biomass and soil moisture.Moderate grazing can not only increase soil organic carbon and active carbon components,but also increase the proportion of soil active carbon,which conforms to the moderate disturbance hypothesis.