摘要
本研究预测,相对于植被的净初级生产力(NPP)来说,随着全球变暖,有机质分解速度加快,土壤有机碳的贮藏速度将减少。因为土壤碳的含量是目前大气含量的两倍,而且从土壤中分解的碳要释放到大气中,因此,土壤碳贮量的减少会大量增加大气CO_2浓度。但是,土壤碳贮量减少的预测在很大程度上依赖于这样的隐含假设:所有土镶有机质的分解像新鲜凋落物的分解一样对温度较为敏感。我们测定了土壤碳的数量和年龄,以及沿温度梯度的凋落物的分解,并用一个简单的模型来描述土壤碳的动态,以显示老土壤有机质的分解阻抗温度的变化。因此,在对气候变暖的响应下,我们估算的分解速度的加快比从前预计的明显要低,并且预测北方森林土壤碳的贮量将增加。
The storage of organic carbon in soil is predicted to decrease with global warming because the decomposition of soil organic matter is expected to accelerate relative to the net primary production (NPP) of vegetation. This decrease would substantially increase the atmospheric CO2 concentration because soil contains twice as much C as the present atmosphere and the decomposed C from soil will be released to the atmosphere. These predictions of the decrease in soil C storage are, however, largely dependent on the implied assumption that the decomposition of all soil organic matter is as sensitive to temperature as is the decomposition of young litter. We used measurements of the amount and age of soil C and the decomposition of litter on temperature gradients and a simple model describing soil C dynamics to show that the decomposition of old soil organic matter is resistant to changes in temperature. Accordingly, in response to climatic warming, we estimate decomposition to accelerate significantly less than previously expected, and predict that the C storage of boreal forest soils will increase.
