喀斯特小流域不同土地利用方式下土壤有机碳的组分特征

Composition Characteristics of Soil Organic Carbon under Different Land Use Types in Small Watershed of Karst

本文以贵州高坡喀斯特小流域的土壤为研究对象,在野外调查及室内分析的基础上,探讨了稻田、林地和荒草地三种土地利用方式对土壤有机碳(SOC)组分含量特征及其分配比例的影响。采用物理-化学联合分组方法,将SOC分为不同粒径的12个土壤组分。研究结果表明,在0~20 cm的表层土壤范围内,林地(3.77 k/kg)各组分有机碳平均含量均显著(P<0.05)高于荒草地(3.17 k/kg),荒草地显著(P<0.05)高于稻田(2.11 k/kg)。在SOC的各组分中,稻田、林地和荒草地三种土地利用方式下iPOM即物理保护有机碳分配比例分别为10%、7%、11%,其在林地中的分配比例较低;cPOM和fPOM作为活性较强的未保护游离活性有机碳,在林地和荒草地中所占SOC分配比例最高,达到30%以上;稻田中游离态粉粒、粘粒和微团聚体粉粒、粘粒有机碳组成的化学保护有机碳分配比例最大为5%。在SOC及其各组分中,fPOM可作为土地利用变化对土壤有机碳影响的评估指标。

The effects of three land use types of woodland,grassland and paddy field on the content and distribution ratio of soil organic carbon（ SOC） were studied on the basis of field investigation and indoor analysis.SOC was divided into 12 soil components based on different particle sizes by physical-chemical combination grouping method. The results showed that in the surface soil of 0 -20 cm,the average content of soil organic carbon in the woodland（ 3. 77 k/kg） was significantly higher（ P 〈0. 05） than that of the grassland（ 3. 17 k/kg）,which was significantly higher（ P 〈0. 05） than that of the paddy field（ 2. 11 k/kg）. Among the components of SOC,the proportion of iPOM,i. e. physical protective organic carbon,was 10% for paddy field,7% for woodland and 11% for grassland,respectively,i. e. iPOM is low in woodland. cPOM and fPOM are the most active unprotected free active organic carbon,and their proportion in SOC components of woodland and grassland was the highest,reaching up to 30%. The proportion of chemical protection organic carbon,consisting of free-grain particles,clay particles and micro-aggregate particles,in the paddy field is the largest,reaching 5%. Among the SOC components,fPOM can be used as an indicator for evaluating the impact of land use changes on the soil organic carbon.