人工油松林恢复过程中土壤理化性质及有机碳含量的变化特征

Dynamics of soil physical-chemical properties and organic carbon content along a restoration chronosequence in Pinus tabulaeformis plantations

采用时空替代法,选取岷江上游大沟流域内不同恢复时期(12、18、25、35a)的人工油松林为研究对象,研究了植被恢复过程中土壤理化性质及有机碳含量的变化特征,同时探讨了它们之间的相互关系。研究结果表明沿恢复梯度,土壤质量得到了改善,主要表现为土壤粘粒含量、比表面积、有机质含量显著增加,土壤粉粒含量和pH值则显著下降。土壤有机质与土壤粘粒和比表面积呈显著正相关,与土壤容重呈显著负相关。此外,土壤有机碳含量沿恢复梯度显著增加,0—50 cm内土壤有机碳含量从5.59 kg/m2增加到12.64 kg/m2,土壤年平均固碳速率为0.31 kg/m2。

Soils are the largest carbon pool in the world and contain two to three times as much as carbon as either terrestrial vegetation or the atmosphere.Therefore,even a slight change in the soil carbon stock could have a major impact on global terrestrial carbon cycling.Afforestation and reforestation are widely recognized as cost-effective methods to mitigate global warming caused by rising atmospheric carbon dioxide（CO2） concentrations through sequestrating CO2 in the atmosphere into vegetation biomass and soil organic matter. Based on the chronosequence of Pinus tabulaeformis（PT） plantations（12,18,25,and 35 years old） located at the Dagou catchment in a dry valley region of the upper Minjing River,Southwestern China,we investigated the dynamics of soil physical-chemical properties and soil organic carbon content following restoration.Using these data,we examined the correlated relationships between soil organic matter and soil physical properties and among soil physical properties.The results show that soil quality was significantly improved along the restoration chronosequence,with the improvement in soil quality attributed to significant increases in soil clay content,soil surface area,and soil organic matter,as well as significant decreases in soil silt content and soil pH.Soil organic matter was significantly,positively correlated with soil clay content and soil surface area but significantly,negatively correlated with soil bulk density.Soil surface area was significantly,positively correlated with soil clay content and negatively correlated with soil silt content.Soil organic carbon content also significantly increased along the restoration chronosequence（from 5.59 kg/m2 in PT12 to 12.64 kg/m2 in PT35 at 0—50 cm depth）.However,the annual soil carbon sequestration rate ranged from an initial rate of 0.05 kg/m2（PT12—PT18） to late 0.36 kg/m2（PT25—PT35）,with the mean of 0.31 kg/m2.