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Increased evaporation following widespread tree mortality limits streamflow response
Author(s) -
Biederman J. A.,
Harpold A. A.,
Gochis D. J.,
Ewers B. E.,
Reed D. E.,
Papuga S. A.,
Brooks P. D.
Publication year - 2014
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2013wr014994
Subject(s) - environmental science , evapotranspiration , streamflow , canopy , hydrology (agriculture) , snow , eddy covariance , potential evaporation , atmospheric sciences , transpiration , drainage basin , ecology , ecosystem , geography , chemistry , geology , cartography , geotechnical engineering , meteorology , biochemistry , photosynthesis , biology
A North American epidemic of mountain pine beetle (MPB) has disturbed over 5 million ha of forest containing headwater catchments crucial to water resources. However, there are limited observations of MPB effects on partitioning of precipitation between vapor loss and streamflow, and to our knowledge these fluxes have not been observed simultaneously following disturbance. We combined eddy covariance vapor loss (V), catchment streamflow (Q), and stable isotope indicators of evaporation (E) to quantify hydrologic partitioning over 3 years in MPB‐impacted and control sites. Annual control V was conservative, varying only from 573 to 623 mm, while MPB site V varied more widely from 570 to 700 mm. During wet periods, MPB site V was greater than control V in spite of similar above‐canopy potential evapotranspiration (PET). During a wet year, annual MPB V was greater and annual Q was lower as compared to an average year, while in a dry year, essentially all water was partitioned to V. Ratios of 2 H and 18 O in stream and soil water showed no kinetic evaporation at the control site, while MPB isotope ratios fell below the local meteoric water line, indicating greater E and snowpack sublimation (S s ) counteracted reductions in transpiration (T) and sublimation of canopy‐intercepted snow (S c ). Increased E was possibly driven by reduced canopy shading of shortwave radiation, which averaged 21 W m −2 during summer under control forest as compared to 66 W m −2 under MPB forest. These results show that abiotic vapor losses may limit widely expected streamflow increases.