Distribution and Movement of Soil Organic Carbon in Grassland and Agricultural Landscapes
Abstract
In order to quantify land use impacts on the magnitude and landscape distribution of soil organic carbon (SOC) we are applying terrain attributes calculated from LiDAR-derived digital elevation models to predict SOC in the upper 1.5 m of soil at grassland and agricultural sites situated on loess soils in southeastern Minnesota. We developed separate regression models for surface (upper 25 cm) and deep (down to 1.5 m) soils and for grassland vs. agricultural sites. Key attributes were: profile curvature, slope, and compound topographic index. In addition to soil depth, these attributes were used to generate regression equations that were able to predict 82% and 77% of the observed variability in grassland and agricultural soils, respectively. While efforts to expand these relationships to perform landscape-scale SOC mass balance are ongoing, preliminary results suggest that agricultural landscapes don't necessarily have less SOC than grasslands. Observed SOC in the upper 10 cm of grassland soils is generally greater than in agricultural soils, this is in agreement with conventional thinking that conversion of grasslands to agriculture results in depletion of SOC. However, when SOC is quantified over the top 1.5 m of soil, agricultural sites show substantial SOC accumulation to deeper soil depths in downslope areas which can represent large pools of SOC in these landscapes. Ongoing efforts include dating of soil horizons via 137Cs analysis in order to assess rates of soil and SOC movement and potential loss in these landscapes.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.B31F0374N
- Keywords:
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- 0402 BIOGEOSCIENCES / Agricultural systems;
- 0428 BIOGEOSCIENCES / Carbon cycling;
- 0486 BIOGEOSCIENCES / Soils/pedology