The secret life of microbes: soil bacteria and fungi undaunted by the harvesting of fire-killed trees

Abstract

Soil health is fundamental to ecosystem health. Disturbances such as fire and timber harvesting can affect the abundance, activity, and composition of soil microbial communities and thus affect soil productivity. In response to forest managers, scientists with the Pacific Northwest Research Station compared health and productivity indicators between soils disturbed by logging machinery to adjacent soils that were burned but not mechanically disturbed after a wildfire in the Deschutes National Forest in central Oregon.

After a wildfire, one management option is to remove fire-killed trees. Postfire logging recoups some of the economic value of the timber and reduces the fuel available for future fires. Prior to this study, little was known about how harvesting activities might affect soils already exposed to disturbance by fire.

Scientists found that microorganisms essential to soil health appeared resilient to compaction from harvest machinery and to deep tilling (subsoiling). However, these mechanical disturbances appeared to reduce soil nutrients, such as nitrogen and phosphorus, in forms that are readily available for plant uptake. Over two years, the differences in nutrients between the disturbed and undisturbed sites lessened as microbial diversity increased and communities changed in composition.

Citation

Meznarich, Paul.; Smith, Jane. 2013. The secret life of microbes: soil bacteria and fungi undaunted by the harvesting of fire-killed trees. Science Findings 153. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 6 p.