Growing forests take greenhouse gases such as carbon dioxide out of the atmosphere. National forests must account for how natural and management-oriented disturbance processes affect carbon storage as an ecosystem benefit. Although it doesn’t always cause large, eye-catching areas of mortality, root disease likely affects carbon storage by reducing tree growth and regeneration over vast areas. However, no previously available tools allowed monitoring of the effect of root disease on carbon storage at a landscape level.
We compared the effects of root disease against the effects other types of forest disturbance across six national forests in Idaho and Montana from 1990-2011. To compare the effects we used a monitoring tool called the Forest Carbon Management Framework (ForCaMF), which makes use of Forest Service Forest Inventory and Analysis data, an empirical growth model, and time series of Landsat satellite imagery. Despite several large fires that burned across these landscapes during the study period, retrospective ForCaMF analysis showed that fire and root disease had approximately equal impacts on carbon storage. While tools informing management of forest carbon storage have generally ignored long-term disturbance processes such as root disease, the recent history of several national forests suggests that such disturbances can be just as important to the carbon cycle as the more conspicuous events like wildfires.
While root disease typically has a lower per-acre impact on carbon storage than processes like intense wildfires, disease can affect much larger areas, and those impacts can last for decades.
Root disease and fires had approximately equal effects on carbon storage across six national forests from 1990 to 2011.