土壤有机碳和活性碳的梯度分布及其对环境变化的反应

Based on data from a field survey in 2001 along the Northeast China transect （NECT）, a precipitation gradient, and a short-term simulation experiment under ambient CO2 of 350μmol mol^-1 and doubled CO2 of 700μmol mol^-1 with different soil moisture contents of 30%-45%, 45%-60%, and 60%-80% soil water holding capacity, the distribution of soil organic carbon and labile carbon along the NECT, their relationships with precipitation and their responses to CO2 enrichment and soil moisture changes were analyzed. The results indicated that the soil labile carbon along the gradient was significantly related to soil organic carbon （r = 0.993, P 〈 0.001）. The soil labile carbon decreased more rapidly with depth than organic carbon. The soil organic and labile carbon along the gradient decreased with decrease in longitude in both the topsoils and subsoils, and the coefficient of variation for the labile carbon was greater than that for the organic carbon. Both the soil organic carbon and labile carbon had significant linear relationships with precipitation, with the correlation coefficient of soil organic carbon being lower （0.677 at P 〈 0.001） than that of soil labile carbon （0.712 at P 〈 0.001）. In the simulation experiment with doubled and ambient CO2 and different moisture contents, the coefficient of variation for soil organic carbon was only 1.3%, while for soil labile carbon it was 29.7%. With doubled CO2 concentration （700μmol mol^-1）, soil labile carbon decreased significantly at 45% to 60% of soil moisture content. These indicated that soil labile carbon was relatively more sensitive to environmental changes than soil organic carbon.

Soil organic carbon and labile carbon along a precipitation gradient and their responses to some environmental changes