OOS 36-7 - Multi-scale observations of hydrologic partitioning following insect-induced tree mortality: Implications for ecosystem water and biogeochemical cycles

Thursday, August 9, 2012: 10:10 AM
A105, Oregon Convention Center
Paul D. Brooks1, Holly R. Barnard2, Joel Biederman1, Bujidmaa Borkhuu3, Steven L. Edburg4, Brent E. Ewers5, Dave Gochis6, Ethan Gutmann7, Adrian A. Harpold1, Jeffrey A. Hicke8, David J.P. Moore9, Elise Pendall10, David Reed11, Andrew Somor1 and Peter A. Troch12, (1)Department of Hydrology and Water Resources, University of Arizona, Tucson, (2)Geography/INSTAAR, University of Colorado, Boulder, CO, (3)University of Wyoming, (4)University of Idaho, (5)Botany, Program in Ecology, University of Wyoming, Laramie, WY, (6)NCAR, Boulder, CO, (7)NCAR, (8)Department of Geography, University of Idaho, Moscow, ID, (9)School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, (10)Botany, University of Wyoming, Laramie, WY, (11)Department of Botany, 3165, University of Wyoming, Laramie, WY, (12)Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ
Background/Question/Methods

Widespread tree mortality associated with insect infestations has impacted millions of hectares across western North America in recent years.  Although previous work on post-disturbance responses (e.g. experimental manipulations, fire, and logging) provides insight into how water and biogeochemical cycles may respond to insect infestations and drought, we find that the unique nature of this disturbance complicates extrapolation to larger scales.  We present a conceptual model of how temporal changes in forest structure impact the individual components of energy balance, hydrologic partitioning, and biogeochemical cycling and the interactions among them.  We evaluate and refine this model using integrated observations and process modeling on multiple scales including plot, stand, flux tower footprint, hillslope, and catchments to identify scaling relationships and emergent patterns in hydrological and biogeochemical responses.

Results/Conclusions

Our results suggest that changes in forest structure at point or plot scales largely have predictable effects on energy, water, and biogeochemical cycles that are well captured by land surface, hydrological, and biogeochemical models.  However, observations from flux towers, isotopic tracers, and nested catchments suggest that both the hydrological and biogeochemical effects observed at tree and plot scales may be attenuated or exacerbated at larger scales.  Compensatory processes are associated with attenuation (e.g. as transpiration decreases, evaporation and sublimation increase), whereas both attenuation and exacerbation may result from nonlinear scaling behavior across transitions in topography and ecosystem structure that affect the redistribution of energy, water, and solutes.  Consequently, the effects of widespread tree mortality on ecosystem services of water supply and carbon sequestration exhibit high spatial heterogeneity, primarily mediated by canopy controls on the hydrologic partitioning of incoming precipitation.