2024 Abstracts

Watershed Ecohydrological Responses to Disturbances Under Changing Climate


Xingyuan Chen1* (xingyuan.chen@pnnl.gov), Faria Zahura1, Gautam Bisht1, Zhi Li1, Nate McDowell1, Peishi Jiang1, Qianyu Zhang2, Heping Liu2, Tim Scheibe1


1Pacific Northwest National Laboratory, Richland, WA; 2Washington State University, Pullman, WA



Disturbances such as wildfire, insect outbreaks and droughts cause significant but poorly understood impacts on water and carbon cycles, posing an unpredictable threat with increasing frequency, spread, and severity of disturbances. It is crucial to comprehend post-disturbance recovery processes in watersheds to elaborate the understanding of disturbance impacted ecohydrological processes and the implications of changing climate. Thus, researchers investigated climate, topography and fire impacts on recovery responses in burned areas that occurred in 2015 across the Columbia River Basin. Using the Enhanced Vegetation Index (EVI) as a proxy of post-fire vegetation biomass recovery, random forest (RF) models were trained for each land cover type to quantify the relationships between incremental EVI recovery and various climate and biophysical factors, including annual precipitation, annual median maximum daily temperatures, elevation, slope, aspect, burn severity and years elapsed after fire. Feature importance analyses revealed that precipitation and temperature were the two most influential factors controlling the EVI recovery. Partial dependence analyses revealed that increasing precipitation was associated with increasing incremental EVI changes for all land cover types.

Evergreen forest showed increasing EVI change with increasing temperature. Conversely, shrubs and grassland showed rising trends in EVI until reaching 12.5°C, above which a reverse trend was observed. This work is an important step towards understanding and representing ecohydrological responses to disturbances. While current work explores vegetation recovery using remote sensing products, the next step is to employ vegetation dynamics model ELM- FATES to account for post-fire vegetation recovery and its impact on water, energy, and carbon budgets. ELM-FATES can be further coupled with ATS-PFLOTRAN to enable the integration between ecohydrologic and hydrobiogeochemical processes from the hillslopes to watersheds, providing new insights into water and carbon export from land to streams as impacted by the interactions among watershed biophysical setting, climate, and disturbances.