岷江流域不同土地利用方式下紫色土壤活性有机碳分布特征及其影响因子

Labile Organic Carbon of Different Land Use Patterns in Minjiang River Basin,Sichuan Province

作为土壤质量的重要指标,土壤活性有机碳(SLOC)在土壤许多物理、化学和生物特性中发挥着重要作用。通过对不同土地利用方式土壤进行采样和分析,系统地研究和比较了四川省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)SLOC分布特征及其影响因子。结果表明:岷江流域不同土地利用方式土壤机械组成不尽一致,土壤总孔隙度与土壤容重变化趋势相反。不同土地利用方式对土壤养分具有较大影响,土壤有机碳、全氮、全磷和全钾均呈现出一致性规律,大致表现为次生林和灌草丛高于人工林和坡耕地,而不同土地利用方式土壤全磷差异并不显著(p>0.05)。不同土地利用方式SLOC均呈现出一致性规律,大致表现为次生林和灌草丛高于人工林和坡耕地。不同土地利用方式SLOC垂直方向随土层深度的增加表现出递增趋势,并且降低幅度逐渐减小,坡耕地、灌草丛、次生林和人工林SLOC从表层至底层逐渐递减,呈"T"形分布,"表聚性"较为明显。人工林、灌草丛和坡耕地在10—20cm SLOC/SOC比例最高,而次生林0—10cm SLOC/SOC比例最高,不同土地利用方式SLOC/SOC比例均在30—40cm最低。相关性分析表明,不同土地利用方式SLOC与SOC和全氮均呈极显著正相关性(p<0.01),与土壤容重均呈负相关。表明SLOC受土壤养分和机械组成影响较大,其中SOC和全氮是不同土地利用方式SLOC变化的重要影响因素。SLOC与土壤有机碳之间呈极显著正相关关系(R2=0.9961),说明SLOC能够作为研究不同土地利用方式SOC动态变化的一个敏感性指标而提前反映土壤碳库的动态变化,其含量在很大程度上依赖于所处生境下SOC含量。

The Minjiang River Basin has great position for its ecology and geography.As an essential indicator of soil quality,soil labile organic carbon(SLOC)and its fractions play an important role in many soil chemical,physical and biological properties.A field experiment was conducted to determine the variation and influencing factors of SLOC under different land use patterns in the Minjiang River Basin.The results are as follows.The soil mechanical composition under different land use patterns was different,and the change trend of soil total porosity was contrary with the soil bulk density.The soil organic carbon,total nitrogen,total phosphorus and total potassium had the same change trends,which showed secondary forest and scrubgrassland higher than that of artificial forest and slope cropland,while the soil total phosphorus had no significant difference under different land use patterns(p>0.05).SLOC under different land use patterns ordered secondary forest and scrub-grassland higher than that of artificial forest and slope cropland.SLOC declined with decreasing soil depth and showed a decline along the vertical soil profile with a‘T'shape distribution with the obvious‘surface accumulation'.The highest ratio of SLOC/SOC of scrub-grassland,artificial forest and slope cropland was in 10—20cm,while secondary forest was in 0—10cm,and the lowest ratioof SLOC/SOC under different land use patterns was in 30—40cm.Correlation analysis showed that SLOC had a significant difference with SOC,TN(p<0.01),which indicated that SLOC was mainly depended on the organic carbon content to a large extent.In addition,the content of SOC was the important influencing factors under different land use patterns in the Minjiang River Valley.SLOC and the soil organic carbon presented extremely significant correlation(R2=0.996),which could be a better parameter to reflect the status of soil organic carbon pool in the Minjiang River Valley than soil total organic carbon content.