Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario K1A0C6, Canada.
Ottawa Research and Development Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario K1A0C6, Canada.
Sci Total Environ. 2021 Apr 15;765:142701. doi: 10.1016/j.scitotenv.2020.142701. Epub 2020 Oct 2.
Surface albedo and soil carbon sequestration are influenced by agricultural management practices which impact the Earth's radiation budget and climate change. In this study we investigate the impact of reduced summer fallowing and reduced tillage in the Canadian Prairies on climate change by estimating the change in radiative forcing due to albedo and soil carbon sequestration. Seasonal variations of albedo, which are dependent on agricultural management practices and soil colour in three soil zones, were derived from 10-day composite 250-m Moderate Resolution Imaging Spectroradiometer (MODIS) data. Using this information, we found an overall increase of surface albedo due to the conversion from summer fallowing to continuous cropping and from conventional tillage (CT) to either no-tillage (NT) or reduced tillage (RT). The increase was dependent on soil brightness, type of vegetation and snow cover. Using data from the Census of Agriculture and taking into consideration both albedo and soil carbon changes, we estimated that from 1981 to 2016, the total radiative forcing for the cropland area in the Canadian Prairies was -405 μW m due to the conversion of CT to either NT or RT and about 70% was due to the change in albedo. During the same period, the total radiative forcing was -410 μW m due to a reduction in the area under summer fallow and about 62% was due to the change in albedo. The equivalent atmospheric CO drawdown from these two management changes from albedo change was about 7.8 and 8.7 Tg CO yr, respectively. These results demonstrate that it is important to consider both the changes of soil carbon and surface albedo in evaluating climate change impacts due to agricultural management practices.
地表反照率和土壤碳固存受农业管理措施的影响，这些措施会影响地球辐射预算和气候变化。本研究通过估算反照率和土壤碳固存引起的辐射强迫变化，来调查加拿大草原减少夏季休耕和减少耕作对气候变化的影响。从三个土壤带的农业管理措施和土壤颜色依赖的 10 天复合 250m 分辨率成像光谱仪（MODIS）数据中得出了反照率的季节性变化。利用这些信息，我们发现由于从夏季休耕到连续种植以及从常规耕作（CT）到免耕（NT）或减少耕作（RT）的转变，地表反照率总体上有所增加。这种增加取决于土壤亮度、植被类型和积雪覆盖。利用农业普查数据，并考虑到反照率和土壤碳的变化，我们估计从 1981 年到 2016 年，加拿大草原农田的总辐射强迫由于 CT 转变为 NT 或 RT，约为-405 μW m，约 70%是由于反照率的变化。在同一时期，由于夏季休耕面积减少，总辐射强迫为-410 μW m，约 62%是由于反照率的变化。这两种管理措施因反照率变化而导致的大气 CO 减排量分别约为 7.8 和 8.7 Tg CO yr。这些结果表明，在评估农业管理措施对气候变化的影响时，考虑土壤碳和地表反照率的变化非常重要。
