Biogeochemistry of beetle-killed forests: Explaining a weak nitrate response

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A current pine beetle infestation has caused extensive mortality of lodgepole pine (Pinus contorta) in forests of Colorado and Wyoming; it is part of an unprecedented multispecies beetle outbreak extending from Mexico to Canada. In United States and European watersheds, where atmospheric deposition of inorganic N is moderate to low (<10 kg⋅ha⋅y), disturbance of forests by timber harvest or violent storms causes an increase in stream nitrate concentration that typically is close to 400% of predisturbance concentrations. In contrast, no significant increase in streamwater nitrate concentrations has occurred following extensive tree mortality caused by the mountain pine beetle in Colorado. A model of nitrate release from Colorado watersheds calibrated with field data indicates that stimulation of nitrate uptake by vegetation components unaffected by beetles accounts for significant nitrate retention in beetle-infested watersheds. The combination of low atmospheric N deposition (<10 kg⋅ha⋅y), tree mortality spread over multiple years, and high compensatory capacity associated with undisturbed residual vegetation and soils explains the ability of these beetle-infested watersheds to retain nitrate despite catastrophic mortality of the dominant canopy tree species.

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Publication type Article
Publication Subtype Journal Article
Title Biogeochemistry of beetle-killed forests: Explaining a weak nitrate response
Series title PNAS
DOI 10.1073/pnas.1221029110
Volume 110
Issue 5
Year Published 2013
Language English
Publisher National Academy of Sciences
Contributing office(s) Colorado Water Science Center
Description 5 p.
First page 1756
Last page 1760
Country United States
State Colorado
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