海拔对神农架表层土壤活性有机碳含量的影响

Effects of Elevation on Surface Layer Soil Active Organic Carbon Content in Shennongjia Nature Reserve

土壤作为陆地生态系统最大的有机碳库，其碳贮量现状及贮碳能力是气候、植被及人类活动等长期作用的结果（ Craine et al．，2011），其微小变化都将明显影响大气CO2浓度，因而在全球碳循环过程中起重要作用（ Tarnocai et al．，2009）。弄清陆地土壤有机碳的分布、转化及其对环境变化的响应是正确理解陆地生态系统碳循环过程和准确评估碳排放的关键（王建林等，2009）。

In this study,five typical vegetation types were selected along the elevational gradient in Shennongjia Nature Reserve,including shrubs, coniferous forest, mixed forest between coniferous and deciduous broad-leaved forest, deciduous broad-leaved forest,and evergreen broad-leaved forest. The content of soil organic carbon （ SOC ） ,water dissolved organic carbon （ WDOC ） ,labile organic carbon （ LOC ） ,and microbial biomass carbon （ MBC ） and their allocation proportions to SOC were analyzed. Furthermore,the Pearson relationship was analyzed between soil active organic carbon and plant diversity or soil physiochemical properties. The results showed that the soil organic carbon in the surface layer increased with the elevation increased, except for the deciduous broad-leaved forest. Distribution characteristics of MBC and LOC content along elevation gradient were obvious,but WDOC content was independent of the elevation gradient. The contents of the three kinds of active organic carbon in different elevational gradients were in the order of： LOC〉MBC 〉WDOC. The allocation ratios of MBC,LOC and WDOC to SOC did not significantly alter with elevational gradient. Pearson relationship showed that SOC and MBC had a significant negative correlation with the diversity of trees and shrubs （P 〈 0. 05）,while LOC and WDOC content had no significant correlation with plant diversity. In addition,SOC and MBC were significantly positively correlated with the content of soil moisture,total nitrogen,available nitrogen,total phosphorus and total sulfur （P〈0. 01）. LOC had a significant and positive correlation with the content of soil moisture,total nitrogen,available nitrogen and total sulfur （P 〈0. 01）. There was a significant correlation between LOC and total phosphorus （ P〈0 . 05 ） . The results revealed that these factors had a dominating impact on SOC,LOC and MBC. WDOC content had no obvious correlation with soil factors.