Increased streamflow in catchments affected by a forest disease epidemic

Kevin D Bladon; Sharon Bywater-Reyes; Jared M LeBoldus; Susanna Keriö; Catalina Segura; Gabriela Ritóková; David C Shaw

doi:10.1016/j.scitotenv.2019.07.127

Increased streamflow in catchments affected by a forest disease epidemic

Sci Total Environ. 2019 Nov 15:691:112-123. doi: 10.1016/j.scitotenv.2019.07.127. Epub 2019 Jul 9.

Authors

Kevin D Bladon¹, Sharon Bywater-Reyes², Jared M LeBoldus³, Susanna Keriö⁴, Catalina Segura⁵, Gabriela Ritóková⁵, David C Shaw⁵

Affiliations

¹ Department of Forest Engineering, Resources, and Management, 280 Peavy Hall, 3100 SW Jefferson Way, Oregon State University, Corvallis, OR 97331, USA. Electronic address: bladonk@oregonstate.edu.
² Department of Forest Engineering, Resources, and Management, 280 Peavy Hall, 3100 SW Jefferson Way, Oregon State University, Corvallis, OR 97331, USA; Department of Earth and Atmospheric Sciences, University of Northern Colorado, 501 20th St Box 100, Greeley, CO, 80639, USA.
³ Department of Forest Engineering, Resources, and Management, 280 Peavy Hall, 3100 SW Jefferson Way, Oregon State University, Corvallis, OR 97331, USA; Department of Botany and Plant Pathology, 2082 Cordley Hall, 2701 SW Campus Way, Oregon State University, Corvallis, OR 97331, USA.
⁴ Department of Botany and Plant Pathology, 2082 Cordley Hall, 2701 SW Campus Way, Oregon State University, Corvallis, OR 97331, USA.
⁵ Department of Forest Engineering, Resources, and Management, 280 Peavy Hall, 3100 SW Jefferson Way, Oregon State University, Corvallis, OR 97331, USA.

PMID: 31319249
DOI: 10.1016/j.scitotenv.2019.07.127

Abstract

Natural disturbances help maintain healthy forested and aquatic ecosystems. However, biotic and abiotic disturbance regimes are changing rapidly. For example, the Swiss needle cast (SNC) epidemic in the Coast Range of Oregon in the U.S. Pacific Northwest has increased in area from 53,050 to 238,705ha over the 1996-2015 period. We investigated whether the hydrologic regime (i.e., annual streamflow, runoff ratio, and magnitude and timing of peak flows and low flows) was affected by SNC in 12 catchments in western Oregon. The catchments ranged in size from 183 to 1834km² and area affected by SNC from 0 to 90.5%. To maximize the number of catchments included in the study, we analyzed 20years of SNC aerial survey data and 15-26years of stream discharge (Q) and PRISM precipitation (P) and air temperature (T_air) data to test for trends in hydrologic variables for each catchment. As expected, we found that runoff ratios (Q/P) increased in five catchments, all with an area impacted by SNC >10%. This was likely due to the effects of SNC on the hydraulic architecture (i.e., needle retention, sapwood area, sapwood permeability) of affected trees, leading to decreased canopy interception and transpiration losses. Interestingly, two catchments with the greatest area affected by SNC showed no changes in hydrologic regime. The lack of hydrologic response could either be due to compensatory transpiration by vegetation unaffected by the disease or sub-canopy abiotic evaporation, which counteracted reductions in transpiration. This study is the first to illustrate that chronic canopy disturbance from a foliage pathogen can influence catchment scale hydrology.

Keywords: Catchment hydrology; Evapotranspiration; Forest disturbance; Runoff ratio; Swiss needle cast.

MeSH terms

Ecosystem
Environmental Monitoring*
Forests*
Hydrology
Oregon
Plant Diseases*
Rivers / chemistry*
Trees
Water Movements*