摘要：As nations debate whether and how best to include the agricultural sector in greenhouse
gas pollution reduction schemes, the role of soil organic carbon as a potential large carbon
sink has been thrust onto center stage. Results from most agricultural field trials indicate a
relative increase in soil carbon stocks with the adoption of various improved management
practices. However, the few available studies with time series data suggest that this relative
gain is often due to a reduction or cessation of soil carbon losses rather than an
actual increase in stocks. On the basis of this observation, we argue here that
stock change data from agricultural field trials may have limited predictive power
when the state of the soil carbon system is unknown and that current IPCC
(Intergovernmental Panel on Climate Change) accounting methodologies developed
from the trial results may not properly credit these management activities. In
particular, the use of response ratios is inconsistent with the current scientific
understanding of carbon cycling in soils and response ratios will overestimate
the net–net sequestration of soil carbon if the baseline is not at steady state.
