Soil carbon content decreases for up to 30 years following clear-cutting in forested areas, according to a major study from the Nordic countries and Canada.
Photo credit: Anne Sverdrup-Thygeson
Nearly half of all the carbon stored on land is found in forests, as both trees and soil act as powerful carbon sinks.
Forest management approaches affect forests ability to store carbon. A large dataset from the Nordic countries and Canada now shows how clear-cutting impacts the soil’s ability to store carbon over time.
“Our analyses show that in coniferous forests, there is a continuous loss of carbon from the organic soil layer for approximately 30 years following clear-cutting,” says Carl-Fredrik Johannesson, researcher at the Norwegian Institute for Nature Research (NINA) and lead author of a recently published study.
At the lowest point, carbon stocks had decreased by 23 percent in spruce forests and by 14 percent in pine forests. In spruce forests, carbon levels remained at this reduced level for the remainder of the observation period (up to 53 years after clear-cutting), whereas in pine forests, carbon stocks gradually recovered and returned to pre-harvest levels 48 years after clear-cutting.
“We are most certain for the period up to 40 years after clear-cutting. Beyond this, we have less data, and uncertainty increases,” Johannesson points out. As suggested in previous studies, the new findings indicate that areas with higher initial carbon stocks also face a greater risk of carbon loss.
“In this context, it is important to note that we have not been able to examine areas where the organic soil layer exceeds 40 cm in thickness—that is, the most carbon-rich sites,” says Johannesson.
Extensive network collaboration
This is the first time that soil data from national forest inventories in Norway, Sweden, Denmark, Finland, and Canada have been compiled and harmonized to account for methodological differences.
“The strength of this study lies in the large, integrated dataset. It has enabled us to identify long-term carbon trends following clear-cutting,” says Johannesson.
There has previously been considerable uncertainty regarding what happens to soil carbon following logging, and this study therefore represents an important contribution to advancing knowledge in this field.
“Clear-cutting leads to long-term loss of soil carbon in the organic layer, and the losses are greatest in the most carbon-rich forests—such as high-productivity spruce forests, which are also particularly important for biodiversity. Extensive clear-cutting makes it even more challenging to meet Norway’s climate targets for 2030 and 2050,” says NINA researcher Jenni Nordén, who leads the ForBioFunCtioN project, to which the recently published soil carbon study is linked.
“Soil carbon loss following logging is accounted for in the methodology used in Norway’s greenhouse gas inventory for forests, but to achieve more realistic and less uncertain estimates, additional data from Norwegian forests are needed,” says Nordén.
The work was carried out through the researcher network NorForSoil, funded by Nordic Forest Research and coordinated by Lise Dalsgaard at Norwegian Institute of Bioeconomy Research (NIBIO); the research project ForBioFunCtioN, funded by the Research Council of Norway; and the BIOCARBON project at NINA, led by Zander Venter. NINA’s collaborators in the study included NIBIO, the Swedish University of Agricultural Sciences, the University of Copenhagen, the Natural Resources Institute Finland (Luke), and the Canadian Forest Service.
Contact: Carl-Fredrik Johannesson
Read article here: Decadal Decline in Forest Floor Soil Organic Carbon after Clear-Cutting in Nordic and Canadian Forests