Forested Ecosystems and Interacting Stressors: Management of Unintended Consequences

W.J. Otrosina and P. Spaine

USDA Forest Service Southern Research Station

Recent management activities and various land uses have dramatically altered edaphic and environmental conditions from those under which forest tree species and ecosystems have evolved.  For example, fire suppression in fire-dependent Sequoia giganteum stands has resulted in increased mortality due to Heterobasidion annosum.  One hypothesis is that fire suppression results in increased encroachment of true firs, readily infected by S group H. annosum, thereby transferring the disease via root contacts with S. giganteum.  Also, the existence of a hybrid between the S and P groups of H. annosum may be evidence for anthropogenic influences on evolutionary pathways in this pathogen.  In other ecosystems, such as Pinus palustris (longleaf pine) in the southeastern United States, increased mortality following prescribed fire is being observed.  Various Leptographium species and H. annosum have been associated with this mortality following relatively cool fires.  How these fungi interact with fire and various edaphic factors is not known, however, these examples illustrate the concept of “exotic ecosystems” corresponding to root disease effects on some present day forest ecosystems.

corresponding author:

W.J. Otrosina
USDA Forest Service
320 Green Street
Athens, GA 30602
706-559-4295
wotrosina@fs.fed.us