A Big Sky Carbon Sequestration Partnership (BSCSP) research team examined the utility and developed methods for monitoring cropping practices in north central Montana that are currently subject to potential carbon credit trading. The advantage of developing remote sensing methods for this purpose is to provide monitoring and validation over large areas to support carbon trading markets.
The research team used an object-oriented approach in conjunction with the Random Forest algorithm to classify agricultural practices, including tillage (till or no-till (NT)), crop intensity, and grassland-based conservation reserve (CR). This study hypothesized that the inclusion of high temporal data into the classification process would increase conservation tillage accuracy due to the added likelihood of capturing spectral changes in Montana fields following a tillage disturbance. Classification accuracies were evaluated for Random Forest models based on 250-m and 500-m MODIS, 30-m Landsat, and 30-m synthetic reflectance values.
These remote sensing methods enabled the team to establish regional percentage estimates of cropland under no-till as influenced by prior tillage management, various degrees of crop intensity, and conservation reserve within north central Montana. Literature-based carbon sequestration estimates were used to generate carbon gain data associated with the conversion to no-till and to conservation reserve. These estimates were then applied to the area-based cropland statistics to estimate potential regional carbon sequestration associated with these management changes.
Results for this study indicated that an estimated 26% of the evaluated research region was under a grassland-based CR management in 2007, yet only 2% of this area was documented as being under current CRP contract. For cropland management, findings estimated that 56% of the region used NT in 2007, while 44% remained under a tillage-based management. Correspondingly, potential regional sequestration estimates for north-central Montana were calculated at 18,855 t C year−1 (69,198 t CO2 year−1). For tillage and minimal-tillage (MT) lands, estimates showed that 46,555–60,522 t C year−1 (170,857–222,116 t CO2 year−1) might be sequestered within the 0–20 cm soil depth. The predicted regional SOC sequestration was found to be more moderate for the MT-to-NT assumptions (37,244 t C year−1), and was expectedly higher under an intensive tillage-to-NT adjustment (55,866–81,472 t C year−1). Values for sequestration potential are additionally influenced by specific environmental inputs, such as vegetation type, soil nitrogen levels, crop type, livestock management, and other variables that should be considered in potential sequestration analyses.