Dissolved organic carbon (DOC) is made up of the tiny fragments of organic matter found in soil and water, but its small size can generate broad consequences. DOC is an important part of the carbon cycle, and it affects water chemistry and light penetration in rivers, lakes, and the sea. Changes in DOC can severely disrupt aquatic ecosystems. Here Oni et al. demonstrate how climate change and forest harvesting might increase DOC concentration and flow in boreal forests.
Boreal forest covers about 17% of the Earth’s surface and is known for its evergreen trees and long winters. Climate change and forest harvesting have separate effects on DOC in boreal stream water, but until now, no one has explored their combined effects.
The team linked regional climate change models with hydrological and biogeochemical models to simulate DOC changes in the boreal forest of Sweden. They examined water chemistry on a local level (about 10 hectares), considering multiple possible scenarios through the year 2090.
The simulations incorporated precipitation, temperature, and DOC data from the Krycklan catchment, a 68 square kilometer forested region in Sweden. They also took into account the effects of forest harvesting on hydrology and soil conditions, seen from the results from a nearby clear-cut experiment. A landscape model allowed the team to zoom out to see results for the whole region.
They found that on a regional level, forest harvesting and climate change increased DOC concentration and flow. However, their results vary widely at the local scale, where factors such as soil type and wetness come into play.
The models predict DOC concentration in boreal streams to rise by about 2 milligrams per liter. Different scenarios predict different changes in DOC flow out of the boreal forest landscape; some show a 50% increase, whereas others show a 100% increase in the next 75 years. Further study will help scientists understand how this might negatively affect downstream ecosystems in the Baltic Sea. (Journal of Geophysical Research: Biogeosciences, doi:10.1002/2015JG003190, 2015)
—Sarah Stanley, Freelance Writer
Citation: Stanley, S. (2016), Modeling the future of dissolved organic carbon in boreal forests, Eos, 97, doi:10.1029/2016EO045127. Published on 9 February 2016.