But what happens to the soil\u2019s carbon levels after forest harvests? <\/p>\n\n\n\n
According to published research by OSU and Weyerhaeuser Company, conventional timber harvesting has no effect on carbon levels in the mineral soils of the western Pacific Northwest for at least three-and-a-half years after harvest. <\/p>\n\n\n\n
Historic in its scope, a collaborative and long-term effort between Hatten and Scott Holub of Weyerhaeuser monitored nine managed Douglas-fir forest stands in Oregon and Washington before and after traditional timber harvest and replanting, analyzing more than 50,000 soil samples from 2700 sample points.<\/p>\n\n\n\n
\u201cOur original hypothesis that timber harvesting would decrease soil carbon in the short term was disproven,\u201d Hatten says. \u201cEven where you have the highest soil temperatures and the highest soil moistures \u2013 the strongest environment for decomposition that releases carbon dioxide into the atmosphere \u2013 harvesting doesn\u2019t seem to have an impact in the areas we studied.\u201d<\/p>\n\n\n\n
Across all the sites combined, after harvest, the scientists found little change (+2%) in mineral soil carbon content and a 184% hike in forest floor carbon, the result of harvest residue.<\/p>\n\n\n\n
![\"\"](\"https:\/\/osu-wams-blogs-uploads.s3.amazonaws.com\/blogs.dir\/3115\/files\/2022\/04\/mccool_blog.png\")
<\/figure><\/div>\n\n\n\n\u201cWe should not overlook the importance of the 184% increase in forest floor carbon,\u201d says Katherine McCool, a master\u2019s student in Hatten\u2019s lab who is researching forest soil and watershed processes. \u201cWe can expect this increase because the branches, needles and bark that fall to the ground as harvest residue, in addition to the dead roots and stumps from harvested trees, will provide much of the future carbon that will infiltrate into the soil.\u201d<\/p>\n\n\n\n
The study, the most extensive sampling ever conducted to determine if harvesting has an impact on soil carbon, is essential because of soil\u2019s ability to store carbon to mitigate and prevent increased greenhouse
gases and maintain a stable carbon balance in the soil for sustainable forest management.<\/p>\n\n\n\n
\u201cSoil carbon also is useful in establishing a suitable microbiome for plant and fungal growth,\u201d says McCool. \u201cWithout ample soil carbon, new seedlings in post-disturbance areas will not be able to grow.\u201d<\/p>\n\n\n\n
Hatten had plans to resample these research sites in coming years and decades to look at the longer-term impacts. Then the 2020 Holiday Farm fire occurred, tearing through some of the research sites near Eugene, Oregon, and dramatically altering the forest landscape. The research continues, but now Hatten and McCool are also studying the role and effect of fire on soil carbon dynamics, examining one of the nine research sites which burned and assessing how soil changes after a severe wildfire in a harvested stand.<\/p>\n\n\n\n
\u201cThe existence of this preestablished soil carbon site provides an excellent opportunity to study the difference between pre- and post-fire soil carbon, which is often hard to come by due to the spontaneity of wildfire,\u201d says McCool.<\/p>\n\n\n\n
Hatten and McCool found a 97% decrease in forest floor carbon within the research site, which equates to 14-times less forest floor carbon than in the pre-harvest stand. The fire\u2019s impact on the mineral soil carbon is still undetermined, but given that 90% of the soil\u2019s carbon lies below the forest floor, the results will have big ramifications for the total carbon budget of the site.<\/p>\n\n\n\n
\u201cThese initial results show that disturbances like fire can reduce carbon sequestration progress,\u201d says McCool. \u201cTherefore, management activities need to include a focus on fire-safe landscapes if we want to prioritize carbon containment.\u201d<\/p>\n\n\n\n
A version of this story appeared in the Spring 2022 issue of <\/em>Focus on Forestry<\/a>, the alumni magazine of the Oregon State University College of Forestry.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":" The amount of carbon stored in soils is about three times that in living plants and double that in the atmosphere. But, we often overlook soils\u2019 powerful ability to store carbon. \u201cConcern about rising atmospheric carbon dioxide concentrations has heightened interest in the role that forests play in carbon sequestration, storage and cycling,\u201d says Jeff… Continue reading