期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 110, 期 5, 页码 1756-1760出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1221029110
关键词
nitrogen biogeochemistry; streamwater chemistry; nitrate loss; watershed disturbance
资金
- US Geological Survey
- US Forest Service for long-term stream chemistry analysis at the Fraser Experimental Forest
- National Science Foundation [DEB 0743498]
- National Oceanic and Atmospheric Administration Western Water Assessment Regional Integrated Sciences and Assessments program at the University of Colorado
- National Science Foundation Boulder Creek Critical Zone Observatory [NSF 0724960, NSF 0742544]
- US National Park Service
- National Science Foundation
- A.W. Mellon Foundation
- Direct For Biological Sciences
- Division Of Environmental Biology [1114804, 1256696] Funding Source: National Science Foundation
- Division Of Earth Sciences
- Directorate For Geosciences [1239281] Funding Source: National Science Foundation
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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