秦岭辛家山典型植被类型土壤活性有机碳分布特征

Distribution Characteristics of Active Soil Organic Carbon under Typical Vegetation Types in Xinjiashan Forest in Qinling Mountains

为探究秦岭辛家山林区不同植被类型土壤有机碳及活性组分分布特征,调查采集秦岭辛家山林区云杉林、灌木林、红桦林、锐齿栎林和落叶松林不同土层土壤样品,比较分析5种植被下土壤有机碳(SOC)、水溶性有机碳(DOC)、微生物生物量碳(MBC)和易氧化碳(ROC)。结果表明,1)林区高海拔地区SOC显著高于低海拔地区,高海拔地区0~60cm各土层SOC灌木林>云杉林>红桦林,同处低海拔地区的落叶松林SOC大于锐齿栎林;2)土壤DOC和MBC总体表现出高海拔地区高于低海拔地区,云杉林MBC和灌木林ROC均高于相同土层的其他植被类型,高海拔区域各土层不同植被类型ROC表现为灌木林>云杉林>红桦林,低海拔区域各土层ROC表现为落叶松林>锐齿栎林;3)各植被类型DOC/SOC均随土层深度的加深而增大,ROC/SOC均随土层深度的加深而减小,而MBC/SOC在土壤剖面上的规律因植被类型不同而异;4)SOC、DOC、MBC、ROC、全氮(TN)和土壤含水量之间均存在极显著正相关关系,土壤有机碳及其活性组分与容重和pH之间表现为极显著负相关性。研究表明辛家山林区高海拔地区SOC显著高于低海拔地区,处于高海拔地区的灌木林>针叶林>阔叶林,同一海拔梯度下针叶林SOC大于阔叶林,林区有机碳活性组分受海拔、植被、土壤含水量、容重和pH等多种因素的共同影响,能够较为灵敏的反映外界环境的改变和有机碳库的变化。

In order to explore the distribution characteristics of soil organic carbon as well as active soil organic carbon under typical vegetation types at different altitudes in Xinjiashan forests of Qinling Mountains, soil samples of 0-10,10-20,20-40 and 40-60 cm in depth were collected to analyze the variations in soil organic carbon （SOC）, soil dissolved organic carbon （DOC）, microbial biomass carbon （MBC） and soil readily oxidizable carbon （ROC） under the vegetation types of Picea asperata, Shrub,Betula albo-sinensis ,Larix and Quercus aliena var. acuteserrata. The results indicated that 1） SOC in high alti- tude area was significantly higher than in low altitude area, SOC in high altitude area was in the order of Shrubs〉P. asperata〉B, albo-sinensis along the whole soil profiles; SOC of Larix was greater than Q. aliena war. acuteserrata in low altitude area. 2） DOC and MBC in high altitude area were higher than in low altitude area. The MBC contents of P. asperata and the ROC contents of Shrubs were higher than the corresponding values in the same soil layer of other vegetation types. ROC in high altitude area was in the order of Shrubs〉P. asperata〉B, albo-sinensis along the whole soil profiles; ROC of Larix was greater than the Q. aliena var. acuteserrata in low altitude area. 3） The DOC/SOC ratio increased with the increase of soil depth,while the ROC/SOC ratio decreased with soil depth for all vegetation types. Nevertheless, the variations of MBC/SOC ratio along soil profile differed among different vegetation types. 4） There were significant positive correlations between SOC,DOC, MBC, ROC, total nitrogen （TN） and soil moisture content. The contents of soil organic carbon and active soil organic carbon were negatively correlated with soil bulk density and pH. The present study demonstrated that soil organic carbon in high altitude area was significantly higher than low altitude area,SOC in high altitude area was Shrubs〉coniferous forest〉broadleaf forest along the whole soil profiles. SOC of coniferous forest was greater than broadleaf forest at the same altitude. The active fractions of soil organic carbon were under the combined effects of many various factors and they could quickly respond to the environmental changes and variations of soil organic carbon pool.