CO2 Emissions from Soil in Response to Climatic Warming are Overestimated—The Decomposition of Old Soil Organic Matter is Tolerant of Temperature

摘要

The storage of organic carbon in soil ispredicted to decrease with global warming because thedecomposition of organic matter is expected toaccelerate relative to the net primary production (NPP)of vegetation. This decrease would substantiallyincrease the atmospheric CO2 concentration because soilcontains twice as much C as the present atmosphere andthe decomposed C from soil will be released to theatmosphere. These predictions of the decrease in soilC storage are, however, largely dependent on the impliedassumption that the decomposition of all soil organicmatter is as sensitive to temperature as is thedecomposition of young litter. We used measurements ofthe amount and age of soil C and the decomposition oflitter on temperature gradients and a simple modeldescribing soil C dynamics to show that thedecomposition of old soil organic matter is resistantto changes in temperature. Accordingly, in response toclimatic warming, we estimate decomposition toaccelerate significantly less than previously expected,and predict that the C storage of boreal forest soils will increase.