Effects of rotational and continuous overgrazing on newly assimilated C allocation
Biology and Fertility of Soils(2020)
摘要
In situ 13CO2 pulse labeling was conducted in temperate grasslands, managed by no grazing, rotational, or continuous overgrazing, to trace the allocation pattern and the dynamics of newly assimilated C into the plant-soil system. Forty-eight days after the labeling, the belowground 13C allocations under overgrazing were substantially lower than those under no grazing (55% for no grazing, 29% for rotational grazing, 36% for continuous grazing). Overgrazing reduced the relative amount of C incorporation into soil organic C (SOC). Overgrazing led to more C losses through shoot respiration (23%, 54%, 46% by no, rotational, and continuous grazing, respectively), but fewer losses via soil respiration (33%, 12%, 13% by no, rotational, and continuous grazing, respectively). Continuous grazing produced more C allocation to roots than rotational grazing (12% vs 4%), indicating that plants had stronger root C storage capacity under continuous than rotational grazing. The mean C residence time of the belowground rhizodeposits and C used for root respiration under rotational grazing (2.08 days) was longer than that under no grazing (1.47 days) or continuous grazing (1.37 days). Overgrazing decreased the C stocks in shoots but remained stable in roots. Meanwhile, overgrazing decreased the newly assimilated C allocation to belowground, creating a negative effect on C sequestration. Under overgrazing regimes, continuous grazing is more preferable in the investigated temperate grasslands than rotational grazing for C allocation and sequestration in soil.
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关键词
13C pulse labeling,Belowground C allocation,Overgrazing,Newly assimilated C,Soil organic matter,Temperate grassland
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