Understanding how Increasing Wildfires Under Climate Change Affect Tree Regrowth and Water Availability in Forests

Lolo National Forest fire

Under a changing climate, the wildfire regime in moist, mixed-conifer forests is shifting in the Pacific Northwest. These wet, high elevation forests, which historically had infrequent fire, are now experiencing multiple severe wildfires over a much shorter timescale. This shift is of particular concern for forest and stream management, as wildfire patterns affect water availability for both forest regeneration and down-gradient water resources. Yet in this ecosystem, little is known about the effects of a new recurrent wildfire regime on post-fire water availability.

This research will assess the effect of wildfire history (frequency and time since burn) for forested hillslope soil-plant-water dynamics. Using Washington State’s Mount Adams as a representative backdrop, this project will quantify post-fire water relations in plots with varying burn history by first evaluating the effects on post-fire hillslope storage and transport using an empirical water balance approach. We will then assess the impact of burn history on tree seedling water stress using several ecophysiology methods both in the field and in the lab. This work will provide a better understanding of the relationships among shifting wildfire patterns, plant water availability, water availability for down-gradient ecosystems and tree seedling vulnerability during the growing season. These results could inform resource management decisions, as well as to provide inputs to models that forecast water and reforestation under recurrent wildfire regimes.