Not all disturbances increase soil greenhouse gas emissions

Abstract:

Soil greenhouse gas (GHG) fluxes are driven by a large number of factors, both biotic and abiotic, and both natural and anthropogenic. Since the soil can act both as a sink and source of GHGs, understanding the controls on soil GHG fluxes has significant implications for managing soil GHG emissions and thus mitigating climate change. Soil GHG fluxes can be strong affected by different disturbance regimes, such as burning/fire, crop or forest harvesting, addition of soil amendments, hurricane, and climatic warming, among others. Most disturbance regimes are expected to increase soil GHG fluxes and resulting in the soil becoming a net source of GHGs. However, some disturbance regimes can decrease GHG emissions. The addition of biochar, a charcoal-like substance produced by the pyrolysis of various types of biomass, to soil, for example, can improve soil fertility, increase carbon storage, and alter a range of soil properties and processes. Biochar addition often decreases nitrous oxide and methane emissions, depending on the type of biochar applied, the soil type, the climate condition, and the type of soil; and in most cases, the effect of biochar application on soil CO₂ emission rates is negligible. Our research shows that biochar application can decrease soil heterotrophic respiration through increasing soil organic carbon recalcitrancy and decreasing carbon degrading microbial activity. Taking together, biochar application is beneficial for mitigating climate change. Other types of disturbances that can potentially decrease soil GHG fluxes include fire, natural or man-made, conversion of land use from intensive to extensive form of land uses, and removal of organic matter from a land use system. This presentation will provide an overview of disturbance effects on soil GHG fluxes, with an emphasis on developing strategies to reduce GHG emissions from the soil.