Smoke on the water: Disentangling the mechanisms through which mega-fires affect lake productivity
Wildfire is one of the most pressing management challenges currently facing western North America. Smoke and ash deposition have become pervasive and long-lasting features of the landscape and affecting lakes in ways that are still not well understood. This project will disentangle the interactive effects of reduced solar radiation, elevated presence of smoke and increased atmospheric deposition of particulates and ash on ecosystem metabolic rates in lake systems to improve management in the face of increasing wildfires.
Climate change and historic forest management that suppressed fire have altered the frequency, severity, and duration of wildfire in western North America, where record size wildfires now occur with increasing regularity. As a result, smoke and ash deposition have become pervasive and long-lasting features of the landscape. So called “smoke storms” are capable of blanketing tens of thousands of square kilometers, substantially reducing incident solar and UV radiation at the surface, lowering temperatures, and raining down ash and fine particulates rich in carbon, nitrogen and phosphorus. The mega-fires currently burning in western North America are altering fundamental drivers of aquatic ecosystem function at regional scales, providing an opportunity to understand how variation among lakes at local scales interact with the effects of such large-scale phenomena to determine individual lake responses.
Primary production and respiration are fundamental processes that structure ecosystems. In aquatic ecosystems, seasonal dynamics in gross primary production (GPP) and ecosystem respiration (ER) determine the magnitude and timing of energy inputs, control rates of carbon and nutrient cycling, affect nutrient stoichiometry, regulate the occurrence of cyanobacterial and other harmful algal blooms (HABs), and ultimately, regulate the structure of aquatic food webs. Although the factors that regulate primary production (i.e., light, nutrients, and temperature) within individual aquatic ecosystems are well understood, similar drivers operating at large spatial scales might result in variable outcomes at the landscape level because of indirect effects from interactions among drivers. This makes predicting the effects of largescale disturbances such as the historically large and sever wildfire currently burning in western North America difficult.
Although the frequency and severity of wildfire is accelerating globally, and there evidence that such fires disrupt the timing of production and sever critical trophic linkages within lake food webs; however, we lack a mechanistic understanding of how interactions among drivers of ecosystem function at landscape scales affect responses in individual aquatic ecosystems. We will disentangle the interactive effects of reduced solar radiation, elevated presence of smoke and increased atmospheric deposition of particulates and ash on ecosystem metabolic rates.
This project will help develop a mechanistic understanding and predictive models for lake responses to wildfire in California. Results from this study will be disseminated to scientific audiences and management implications and predictive models will be will be passed directly to managers.
Regional satellite image (Oregon and California) showing distribution of smoke (A) and air quality patterns (PM2.5) (B) for mid-September, 2020. Study site locations are marked with circles, with yellow denoting study sites Castle Lake (north-most), Lake Tahoe (central), and Emerald Lake (south-most). Some points denote more than one site.