Initial greenhouse gas emissions and nitrogen leaching losses associated with converting pastureland to short-rotation woody bioenergy crops in northern Michigan, USA

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• 作者：Paligwende Nikiè ; ma^a ; ^{nikiemap@msu.edu} ; David E. Rothstein^a ; Raymond O. Miller^b
• 关键词：Land use conversion ; Tillage ; Populus spp. ; Salix spp. ; Pastureland ; Carbon debt
• 刊名：Biomass and Bioenergy
• 出版年：2012
• 期刊代码：3_09619534
• 类别：pw
• 出版时间：April, 2012
• 卷：39
• 期：Complete
• 页码：413-426
• 文件大小：628 K

摘要

We assessed the short-term effects of converting pastureland to hybrid poplar and willow bioenergy plantations on soil greenhouse gas (GHG) fluxes and nitrogen (N) leaching in northern Michigan, USA. We used static chambers to measure soil carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄) efflux, and tension lysimeters to measure nitrate (NO₃^{鈭?/sup>) leaching, in newly-established poplar and willow plantation plots, and in reference pasture plots. Emissions of N₂O increased markedly following cultivation with cumulative direct N₂O emissions of 0.3, 4.6 and 5.9 Mg ha鈭? of CO₂ equivalents (CO₂eq) in the reference, willow and poplar plots, respectively. Similarly, land conversion resulted in large increases of NO₃鈭?/sup> leaching with losses of 2.6, 38.8 and 53.9 kg ha鈭? of N from the reference, willow and poplar plots, respectively. Soil CO₂ fluxes were significantly affected by land-use conversion; soils from willow and poplar plots emitted 29-42%less CO₂ relative to the reference plots. Greater root respiration in the pastureland likely explained the greater soil CO₂ efflux in these plots. Estimates of the net GHG emissions due to land-use conversion were strongly influenced by assumptions regarding the root contribution (RC) to total soil CO₂ efflux. Assuming an RC = 50%, we estimate that pastureland conversion at this site incurred GHG debts of 7.4 and 11.6 Mg ha鈭? y鈭? as CO₂eq for willow and poplar, respectively, during the establishment year. These results demonstrate the need to include soil disturbance impacts on the N cycle in future life cycle assessment of these bioenergy crops.}