用计算机模型验证土壤有机碳周转负反馈作用现象与机理

有机物料腐殖化系数（h）与有机碳降解系数（k）是控制土壤有机碳周转过程的两个关键参数，为研究有机碳含量对该两参数的影响，应用计算机模型探讨有机碳含量对自身周转作用的影响以及相应的机理。结果显示，有机碳含量的动态变化不能反映有机碳含量是否对自身周转造成影响，但有机碳含量与碳输入水平的关系可以反映有机碳含量的作用：即不管该两参数是否与有机碳含量有关，有机碳含量均随着时间延长而渐近线增加或降低至平衡值；当假设两参数与有机碳含量无关，则有机碳含量随碳输入水平增加呈直线增加；但当假设有机碳含量通过有机碳周转负反馈作用影响该两参数，即h随有机碳含量增加而降低，且k同时增加，则有机碳含量随碳输入水平增加而渐近线增加。进一步验证该负反馈作用机理分析也发现，当考虑负反馈作用的机理时，有机碳含量随着碳输入水平增加而渐近线增加。因此有机碳周转负反馈作用合理，在计算机模型构建中考虑该影响因素是必要的，也是可行的。

Validation of negative feedback in soil organic carbon dynamics and its underlying mechanisms using computer models

The humification coefficient of input organic material(h)and decomposition rate(k)of soil organic carbon(SOC)are two key parameters that control the SOC turnover processes. Many previous studies have investigated how elements such as water and temperature can affect these processes, but how the SOC content can affect its own turnover processes is seldom concerned. We developed computer models to test the effect of the SOC content on the SOC turnover processes and its underlying mechanisms. The results showed that however h and k changed the SOC content, it also changed asymptotically with time, and eventually reached equilibrium; When assuming that these two parameters were constant with the SOC content, the SOC content would linearly increase without being limited by the C input level; The SOC content would increase asymptotically with the C input level when assuming that h decreased with the SOC content and k increased simultaneously; An asymptotic relationship between the SOC content and C input level would occur. The changes in h and k with the SOC content were termed as negative feedback to SOC turnover. Further study on the mechanisms underlying the negative feedback supported the asymptotic relationship between the SOC content and C input level. We suggest that the negative feedback of SOC turnover is reasonable, and it is necessary and possible to consider this effect in model development.