Bark beetle impacts on forest evapotranspiration and its partitioning

John F Knowles; Nels R Bjarke; Andrew M Badger; Max Berkelhammer; Joel A Biederman; Peter D Blanken; Mario Bretfeld; Sean P Burns; Brent E Ewers; John M Frank; Jeffrey A Hicke; Leanne Lestak; Ben Livneh; David E Reed; Russell L Scott; Noah P Molotch

doi:10.1016/j.scitotenv.2023.163260

Bark beetle impacts on forest evapotranspiration and its partitioning

Sci Total Environ. 2023 Jul 1:880:163260. doi: 10.1016/j.scitotenv.2023.163260. Epub 2023 Apr 6.

Authors

John F Knowles¹, Nels R Bjarke², Andrew M Badger³, Max Berkelhammer⁴, Joel A Biederman⁵, Peter D Blanken⁶, Mario Bretfeld⁷, Sean P Burns⁸, Brent E Ewers⁹, John M Frank¹⁰, Jeffrey A Hicke¹¹, Leanne Lestak¹², Ben Livneh¹³, David E Reed¹⁴, Russell L Scott⁵, Noah P Molotch¹²

Affiliations

¹ Department of Earth and Environmental Sciences, California State University, Chico, CA, USA. Electronic address: jfknowles@csuchico.edu.
² Department of Civil, Environmental and Architectural Engineering, University of Colorado Boulder, Boulder, CO, USA.
³ Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA.
⁴ Department of Earth and Environmental Sciences, University of Illinois Chicago, Chicago, IL, USA.
⁵ Southwest Watershed Research Center, USDA Agricultural Research Service, Tucson, AZ, USA.
⁶ Department of Geography, University of Colorado Boulder, Boulder, CO, USA.
⁷ Department of Ecology, Evolution, and Organismal Biology, Kennesaw State University, Kennesaw, GA, USA.
⁸ Department of Geography, University of Colorado Boulder, Boulder, CO, USA; National Center for Atmospheric Research, Boulder, CO, USA.
⁹ Department of Botany and Program in Ecology, University of Wyoming, Laramie, WY, USA.
¹⁰ Rocky Mountain Research Station, USDA Forest Service, Fort Collins, CO, USA.
¹¹ Department of Earth and Spatial Sciences, University of Idaho, Moscow, ID, USA.
¹² Institute of Arctic and Alpine Research, University of Colorado Boulder, Boulder, CO, USA.
¹³ Department of Civil, Environmental and Architectural Engineering, University of Colorado Boulder, Boulder, CO, USA; Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA.
¹⁴ Environmental Science, University of Science and Arts of Oklahoma, Chickasha, OK, USA.

PMID: 37028665
DOI: 10.1016/j.scitotenv.2023.163260

Abstract

Insect outbreaks affect forest structure and function and represent a major category of forest disturbance globally. However, the resulting impacts on evapotranspiration (ET), and especially hydrological partitioning between the abiotic (evaporation) and biotic (transpiration) components of total ET, are not well constrained. As a result, we combined remote sensing, eddy covariance, and hydrological modeling approaches to determine the effects of bark beetle outbreak on ET and its partitioning at multiple scales throughout the Southern Rocky Mountain Ecoregion (SRME), USA. At the eddy covariance measurement scale, 85 % of the forest was affected by beetles, and water year ET as a fraction of precipitation (P) decreased by 30 % relative to a control site, with 31 % greater reductions in growing season transpiration relative to total ET. At the ecoregion scale, satellite remote sensing masked to areas of >80 % tree mortality showed corresponding ET/P reductions of 9-15 % that occurred 6-8 years post-disturbance, and indicated that the majority of the total reduction occurred during the growing season; the Variable Infiltration Capacity hydrological model showed an associated 9-18 % increase in the ecoregion runoff ratio. Long-term (16-18 year) ET and vegetation mortality datasets extend the length of previously published analyses and allowed for clear characterization of the forest recovery period. During that time, transpiration recovery outpaced total ET recovery, which was lagged in part due to persistently reduced winter sublimation, and there was associated evidence of increasing late summer vegetation moisture stress. Overall, comparison of three independent methods and two partitioning approaches demonstrated a net negative impact of bark beetles on ET, and a relatively greater negative impact on transpiration, following bark beetle outbreak in the SRME.

Keywords: Ecohydrology; GLEES; MODIS; Niwot Ridge; Spruce beetle; Water resources.

MeSH terms

Animals
Coleoptera*
Forests
Plant Bark
Trees
Weevils*