岷江流域不同土地利用方式对土壤有机碳组分及酶活性的影响

The Variation of Soil Organic Carbon Fractions and Soil Enzyme Activity of Different Land Use Types in Minjiang River Valley

土壤有机碳组分和酶活性是土壤质量和环境变化的"指示器",了解土壤有机碳组分和酶活性及其对土地利用变化的响应对预测区域土壤质量和环境变迁具有重要意义。以岷江流域不同土地利用方式(次生林、人工林、灌草丛和坡耕地)为对象,测定其土壤易氧化有机碳(EOC)、颗粒有机碳(POC)、轻组有机碳(LFOC)和水溶性有机碳(WSOC)以及蔗糖酶、脱氢酶、脲酶和磷酸酶活性,采用方差分析法对比分析了土壤有机碳组分及酶活性,并采用相关分析法分析了土壤有机碳各组分之间的关系,为该区未来土地利用管理提供科学依据。结果表明,不同土地利用方式下土壤总孔隙度(40.36%~47.81%)与土壤容重(0.75~1.38 g·cm-3)变化趋势相反,大致表现为次生林>人工林>灌草丛>坡耕地;不同土地利用方式下土壤养分(有机碳、全氮、全钾)均呈现出一致性规律,而不同土地利用方式下土壤全磷含量差异均不显著(P>0.05);与坡耕地相比,次生林、人工林和灌草丛土壤酶活性(土壤蔗糖酶、脱氢酶、脲酶、酸性磷酸酶活性)均有明显的增加,大致表现为次生林>人工林>灌草丛>坡耕地;EOC、POC、LFOC和WSOC均呈现出一致性规律,大致表现为次生林>人工林>灌草丛>坡耕地。相关性分析表明,土壤碳组分与土壤蔗糖酶、脱氢酶、脲酶和磷酸酶活性均呈显著或极显著的负相关(P<0.05,P<0.01),说明土壤微生物量碳是土壤有效养分的主要影响因素,其中土壤容重对土壤碳组分和酶活性贡献为负,土壤养分对土壤碳组分和酶活性贡献为正,这是造成不同土地利用方式土壤有机碳组分及酶活性差异的重要原因。

Land use types can cause the change of land ecology and biogeochemical cycle,then resulting in the change of soil property and land productivity.Soil organic carbon fractions and soil enzyme activity are sensitive indicators of soil quality and environmental change.Understanding responses of soil organic carbon fractions and soil enzyme activity to land use change is essential to predicate soil quality and environmental change at regional scale.Here,four typical land use systems were selected inMinjiang River Valley,including shrub-grassland,slope farmland,planted forest and secondary forest.Soil easily oxidized organic carbon(EOC),particulate organic carbon(POC),light fraction organic carbon(LFOC),water-soluble organic carbon(WSOC),soil enzyme activity(invertase,dehydrogenase,urease and phosphatase)and their controls were measured.The results showed that the soil conductivity,bulk density and total porosity in sequence was secondary forest,planted forest,slope farmland and shrub-grassland with local fluctuated,and soil fertility(soil organic carbon and total nitrogen)of different land use types had the same variation trend which showed secondary forest>planted forest>shrub-grassland>slope farmland,while there was no significantly difference of different land use types in soil total phosphorus(P>0.05).Compared with slope farmland,there were significantly increase in soil microbial biomass(carbon and nitrogen)and soil enzyme activity(invertase,dehydrogenase,urease and phosphatase),which ordered secondary forest>planted forest>shrub-grassland>slope farmland.Correlation analysis showed that there was an extremely significant difference between soil microbial biomass and soil enzyme activity(P<0.05,P<0.01),soil organic carbon and total nitrogen had an extremely significant difference with soil enzyme activity(P<0.01),while soil bulk density had an extremely negatively significant difference with soil microbial quantity,soil enzyme activity,which indicated that soil microbial biomass carbon was the main source of available nutrients,and soil bulk density had the negative contribution for soil microorganism quantity and enzyme activity.This was the mainly reason for the difference in soil microorganism quantity and enzyme activity,and the soil organic carbon and total nitrogen were the main sources of nutrients.