模拟干旱对鼎湖山季风常绿阔叶林土壤碳氮磷化学计量特征的影响

Effects of Drought on the C/N/P Stoichiometry in the Soil of a Subtropical Monsoon Evergreen Broad-leaved Forest

以对气候变化敏感的南亚热带季风气候区的地带性森林-季风常绿阔叶林为研究对象,依托鼎湖山的降水变化人工控制实验平台,设自然降水和全年降水量减少50%两种处理,分析在2年降水强度改变下,南亚热带季风常绿阔叶林森林土壤碳(C)、氮(N)、磷(P)的变化趋势,探讨模拟干旱对季风常绿阔叶林土壤C、N、P化学计量特征的影响。结果表明:减少降水处理明显降低了土壤含水量;季风常绿阔叶林土壤C、N、P随着土层深度的加深呈逐渐减少的趋势。干旱处理下土壤C、P含量明显增加,N含量变化不明显。在化学计量比方面,季风常绿阔叶林土壤C∶N、C∶P以及N∶P随着土层深度的加深而减少;在减少降水(干旱)处理下,C∶N和C∶P均高于对照,而表层土壤(0~10 cm)N∶P低于对照。2年降水强度减少使该森林土壤呈现干旱趋势,使土壤有机质分解速率下降,影响南亚热带季风常绿阔叶林土壤C、N、P的积累。

In order to investigate the effects of drought on soil carbon （C）, nitrogen （N） and phosphorus （P）, this study was conducted to analyze soil C, N and P content of a subtropical monsoon evergreen broad-leaved forest in the Dinghushan Natural Reserve, with manmade precipitation pattern manipulations. The studied forest is the climax forest in southern China but most sensitive to environmental changes, and therefore important to the stabilization of climate system in this region. A treatment to remove 50% of annual precipitation was conducted for 2 years in the studied forest, with natural precipitation as the control. Results showed that compared with the control, the drought treatment significantly reduced soil moisture. Soil C, N and P content of the subtropical monsoon evergreen broad-leaved forest gradually decreased with the increase of soil depth. Soil C and P content tended to increase but soil N content did not change obviously under the drought treatment in relative to the control. The C∶N, C∶P and N∶P of the subtropical monsoon evergreen broad-leaved forest decreased with the increasing of the soil depth. Detectable increases in soil C∶N and C∶P ratios but a decrease in soil （0-10 cm） N∶P ratio induced by the drought treatment. Our results suggest that a 2-year-period precipitation decrease can significantly reduce soil moisture and therefore decrease the decomposition rate of soil organic matter, change the accumulations of soil C, N and P in the subtropical climax forest of southern China.