An interyear comparison of CO2 flux and carbon budget at a commercial‐scale land‐use transition from semi‐improved grassland to Miscanthus x giganteus

分类： 生物学 >> 植物学 >> 植物生态学和植物地理学 提交时间： 2016-05-04

Jon P. McCalmont Niall P. McNamara Iain S. Donnison Kerrie Farrar John C. Clifton-Brown

摘要： A 6-ha field at Aberystwyth, UK, was converted in 2012 from semi-improved grassland to Miscanthus x giganteus for biomass production; results from transition to the end of the first 3years are presented here. An eddy covariance sensor mast was established from year one with a second mast added from year two, improving coverage and providing replicated measurements of CO2 exchange between the ecosystem and atmosphere. Using a simple mass balance approach, above-ground and below-ground biomass production are combined with partitioned CO2 fluxes to estimate short-term carbon deltas across individual years. Years one and two both ended with the site as a net source of carbon following cultivation disturbances, cumulative NEE by the end of year two was 138.5716.91gCm2. The site became a cumulative net sink for carbon by the end of June in the third growing season and remained so for the rest of that year; NEE by the end of year three was 616.52 39.39gCm2. Carbon gains were primarily found in biomass pools, and SOC losses were limited to years one (1.43MgCha1yr1) and two (3.75MgCha1yr1). Year three saw recoupment of soil carbon at 0.74MgCha1yr1 with a further estimate of 0.78MgCha1 incorporated through litter inputs over the 3years, suggesting a net loss of SOC at 3.7Mgha1 from a 0- to 30-cm baseline of 78.613.28Mgha1, down 4.7%. Assuming this sequestration rate as a minimum would suggest replacement of cultivation losses of SOC by year 8 of a potential 15- to 20-year crop. Potential coal replacement per hectare of harvest over the three-year study would offset 68Mg of carbon emission, more than double the SOC losses.

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