Carbon storage potential of windbreaks on agricultural lands of the continental United States.

摘要

Agricultural production systems face major challenges under climate change scenarios in terms of expected negative impacts on productivity and persistence of the crops. Greenhouse gases from agriculture continue to rise although not as fast as from other fossil fuel-based human activities. Windbreaks perform several ecosystems functions that improve the local and regional capacity of crop systems to increase yields and offer environmental services by minimizing the negative effects of extreme weather events. Windbreaks also represent an important means of mitigating greenhouse gas emissions. This is predominantly accomplished by the windbreak trees storing carbon (C) in their above and belowground woody tissue while reducing carbon dioxide (CO2) emissions either through avoidance of emissions or through energy savings. However, available and reliable data for estimating windbreak contributions to whole-farm and regional C assessments are scarce and in most regions, do not exist.;The main objective of this research was to analyze the C storage potential of field and farmstead windbreaks and to estimate the extent of potential reduction in emissions due to the presence of windbreaks in different farming scenarios in the continental United States. This study was focused on 1) identifying allometric equations suitable for use with the more open-grown trees in windbreaks and then using them to estimate the C storage potential of 16 windbreak tree species in different regions of the continental United States, 2) analyzing the avoidance of carbon emissions for different crops by planting windbreaks, and 3) evaluating hypothetical farms synthesized with different windbreak designs together with cropping systems and farmstead. These scenarios were evaluated in the way they best can offset their carbon emissions.;There were several important results from this study. First, the Jenkins model was found to be the best tool for estimating biomass/carbon storage potential for windbreaks. Second, there were many suitable tree species with promising carbon storage potentials for designing diverse windbreaks. Third, different windbreak designs can offset total carbon emissions from cropping systems in small and large-scale farms. Fourth, windbreaks have an important impact in carbon emissions reduction when planted on agricultural lands. Fifth, two- or three row field windbreaks can potentially offset most carbon crop emissions. Sixth, key aspects determining the windbreak potential for offsetting carbon emissions in farming operations included: site conditions, tree species, house size, windbreak designs, and farmers' willingness to adopt these changes. The findings from this project provide further evidence of the role windbreaks can play in GHG mitigation by agriculture and describe a reasonable, science-based approach for estimating the level of these contributions.