Rising carbon uptake and sequestration but declining carbon allocation
to biomass production and grain yield in a high-yield agroecosystem
Abstract
Photosynthetically carbon (C) allocation largely determines yield and C
sequestration of agroecosystem. However, how C allocation of crops
responses to climate change at the long-time scale is poorly defined.
Combining thirteen years of eddy covariance and inventory measurements,
we comprehensively investigated C allocation mechanism in a winter-wheat
and summer-maize double cropping field. Significantly increased gross
primary production (GPP) was benefited from CO2 fertilization, and 35%
of increased GPP transferred to strengthening C sequestration. However,
elevated temperature and drying surface soil moisture stimulated the
partitioning of GPP to autotrophic respiration, resulted in conservative
net primary production and grain yield. Maize faced a greater risk of C
loss and yield reduction than wheat to warming and drying. By
synthesizing published long-term data of agroecosystems, we further
highlight that the GPP partitioning cannot be simply predicted by
allometric theory, particularly for grains, which should be considered
in predicting C budget and crop yield.