Impacts of soil accumulation from erosion on greenhouse gas production and emission from soil within a complex and cultivated landscape.

摘要

In cultivated, topographically complex landscapes, soil erosion results in the redistribution of large amounts of soil. This soil redistribution changes the source materials and related soil properties within landscapes and within soil profile. These changes are expected to affect production and emission of greenhouse gases (GHG). To evaluate the effect of soil accumulation on CO2 and N2O production and emission, two laboratory experiments and one field experiment were carried out.;Based on the preliminary results of the column study, a detailed field experiment was conducted to study the effect of soil accumulation from soil erosion on GHG profile concentrations and surface emissions. This study was carried out in three depressions within a complex, cultivated landscape, 17 km north of Brandon, Manitoba. Results showed CO2 flux and profile concentrations had obvious seasonal patterns. CO2 flux and concentration changed dramatically as air and soil temperature varied, indicating that temperature is the key factor controlling greenhouse gas production and emission. The highest variation in CO2 concentration occurred during the growing season.;In summary, the effect of the soil accumulation on GHG production and emission was complex. Its effect on CO2 and N2O flux was soil environment-specific. Soil accumulation increased GHG production in that it thickens the surface soil with high available carbon and nitrogen. However, this accumulation may have decreased CO2 and N2O emission due to the limited diffusion in the soil resulting in the further conversion of N2O to N2. The effect of soil deposition also could affect GHG flux through its effect on soil moisture, temperature and substrate availability.;The column study was first conducted in a growth chamber to study the relationship between soil depth and GHG emission. Results showed soil depth had a great effect on CO2 flux. CO2 flux increased dramatically with soil depth. Regression analysis of data collected over 70 days showed the relationship between cumulative flux and soil depth can be described using a linear regression. However, as soil depth increased, emissions are not expected to increase proportionally. The effect of soil depth on N2O flux was observed as well. Generally, N2O flux increased with soil depth. Regression analysis of data collected over 70 days showed the cumulative flux also increased linearly. This experiment was limited in ability to determine the exact effect of soil depth due to limited numbers of depth treatments and the single replicate.