Soil Organic Carbon Response to Cultivation in the Community Land Model

Wednesday, May 14, 2014 - 07:00
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Land surface models have undergone significant changes in order to improve the representation of soil organic carbon (SOC) dynamics. However, some ecosystems that have large influences on the terrestrial carbon cycle are lack sufficient detail to capture the impact on below ground biogeochemistry. Agricultural management practices can influence the inputs of carbon to the soil system. In CLM4.5, a yield calculation was added along with an improved harvest subroutine. Grain is treated as a product and respired as a carbon flux rather than returned as litter. Global and point simulations were performed to examine crop productivity and soil organic carbon changes when grain is not treated as litter. CLM3.5 and CLM4.5 crop models were evaluated and both show a loss of soil organic carbon when harvesting crops. However, the new century-type belowground biogeochemistry model in CLM4.5 changes the soil response to agricultural disturbance, allowing carbon accumulation to incur after several decades. The response is due to inconsistencies in carbon partitioning within the plant components resulting in an increased distribution of residue litter in the soil column. Results are compared against over 4,000 soil organic carbon observations from the International Soil Carbon Network. A brief description of the crop model followed by the simulated effect of cultivation on soil carbon will be presented. The findings indicate the importance of including agriculture ecosystems in climate models in order to capture SOC dynamics.

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