岩溶槽谷区植被恢复对土壤团聚体有机碳及碳库管理指数的影响

Effects of vegetation restoration on soil aggregate associatedorganic carbon and carbon pool management index in karst trough valley region

关键词:  岩溶槽谷区, 植被恢复, 团聚体有机碳, 碳库管理指数

Key words:  karst trough valley region, vegetation restoration, aggregate associated organic carbon, carbon pool management index

摘要:

为揭示岩溶槽谷区植被恢复对土壤结构、土壤有机碳积累和碳库管理水平的影响,该研究选取了弃耕地、林地和草地三种土地利用方式,测定0～20 cm土层土壤团聚体组成、土壤有机碳(SOC)、团聚体有机碳以及土壤易氧化有机碳(EOC)含量。结果表明:(1)与弃耕地相比,林地和草地土壤团聚体平均重量直径(MWD)、几何平均重量直径(MGD)和2～5 mm团聚体含量显著增加,林地和草地土壤团聚体组成以2～5 mm为主,弃耕地以0.5～1 mm和<0.25 mm为主,表明退耕还林还草能够促进土壤团聚体形成和稳定。(2)土壤团聚体有机碳含量呈现出林地>草地>弃耕地,随团聚体粒级增加而增加的趋势; 林地和草地以2～5 mm团聚体有机碳贡献率最大,弃耕地则以<0.25 mm团聚体贡献为主,表明弃耕地转变为林地和草地后,土壤SOC积累主要归功于2～5 mm有机碳含量的增加,以及团聚体由小粒径向大粒径转变。(3)与弃耕地比较,林地和草地土壤SOC、EOC 含量和碳库管理指数(CPMI)均显著提高,其中土壤EOC含量和CPMI变化较为明显; 土壤EOC可作为土壤碳库早期变化的有效指标,CPMI能够良好地表征植被恢复对土壤SOC和EOC的影响。

Abstract:

In order to understand the effects of vegetation restoration on soil structure, accumulation of soil organic carbon(SOC)and carbon pool management levels in karst trough valley region. Three land use patterns including abandoned farmland, woodland and grassland were chosen. Soil samples at 0-20 cm depth were collected and separated into aggregate size fractions. The aggregate amounts, SOC in whole soils and aggregates and easily oxidized organic carbon(EOC)contents were determined. The results were as follows:(1)Compared with abandoned farmland, the mean weight diameter(MWD), the mean geometric diameter(MGD)and 2-5 mm aggregate amounts significantly increased, but 0.5-1 mm and <0.25 mm aggregate amounts significantly decreased in woodland and grassland.(2)The SOC content in soil aggregates decreased as follows: woodland > grassland > abandoned farmland and generally increased with the increase in aggregate size class; The SOC content was mainly attributed by 2-5 mm aggregate associated organic carbon contents in woodland and grassland, but the contribution in abandoned farmland was dominated by <0.25 mm size fraction. The results suggested that SOC accumulation is mainly due to the increase of organic carbon in 2-5 mm aggregate and the conversion from smaller aggregates to larger aggregates.(3)The SOC, EOC contents and carbon pool management indexes(CPMI)in woodland and grassland were greatly improved relative to those of in abandoned farmland. The responses of EOC and CPMI were sensitive to land use changes; Soil EOC can be used as an effective indicator of early changes in SOC status brought about by vegetation changes, and soil CPMI is a good indicator to reflect the impact of vegetation changes on SOC and EOC.