Forest Management Impacts on Greenhouse Gas Fluxes from Riparian Soils Along Headwater Streams

Increasing concentrations of atmospheric greenhouse gases (GHGs; CO 2 , CH 4 , N 2 O) cause climate change. Depending on the conditions, soils have the potential to store carbon or to be a source of GHGs to the atmosphere. Riparian soils in particular have high potential to store carbon, but also to be sources of CH 4 and N 2 O. Headwater streams make up a large proportion of stream length in a drainage network, and their riparian zones have valuable ecosystem functions. In parallel, the riparian zones of headwater streams are particularly vulnerable to forest harvest. Studies of GHG fluxes from these unique ecosystems remain limited. Our objective was to quantify the effects of forestry practices and groundwater discharge (DIS) areas on GHG emissions from riparian forest soils in coastal British Columbia. We compared nine sites with three different forest management protocols: (1) harvesting with a riparian buffer, (2) no buffer, and (3) reference sites without harvesting. We measured gas fluxes, soil temperature, soil moisture and depth to the groundwater table alongside headwater streams monthly over one growing season. We found that CH 4 uptake rates were 65% lower at the no buffer sites, and N 2 O emission rates were 52% lower at the no buffer sites, when compared to the reference sites. Additionally, CH 4 uptake was 54% lower at DIS areas than in non-DIS areas. The results of our research help inform forest management by demonstrating that maintaining riparian buffers can be effective in protecting the ecosystem functions contributing to soil GHG fluxes.