Wildfire may increase habitat quality for spring Chinook salmon in the Wenatchee River subbasin, WA, USA

Abstract

a b s t r a c tPacific Northwest salmonids are adapted to natural disturbance regimes that create dynamic habitat patterns over space and through time. However, human land use, particularly long-term fire suppression, has altered the intensity and frequency of wildfire in forested upland and riparian areas. To examine the potential impacts of wildfire on aquatic systems, we developed stream-reach-scale models of freshwater habitat for three life stages (adult, egg/fry, and juvenile) of spring Chinook salmon (Oncorhynchus tshawytscha) in the Wenatchee River subbasin, Washington. We used variables representing pre-and post-fire habitat conditions and employed novel techniques to capture changes in in-stream fine sediment, wood, and water temperature. Watershed-scale comparisons of high-quality habitat for each life stage of spring Chinook salmon habitat suggested that there are smaller quantities of high-quality juvenile overwinter habitat as compared to habitat for other life stages. We found that wildfire has the potential to increase quality of adult and overwintering juvenile habitat through increased delivery of wood, while decreasing the quality of egg and fry habitat due to the introduction of fine sediments. Model results showed the largest effect of fire on habitat quality associated with the juvenile life stage, resulting in increases in high-quality habitat in all watersheds. Due to the limited availability of pre-fire high-quality juvenile habitat, and increased habitat quality for this life stage post-fire, occurrence of characteristic wildfires would likely create a positive effect on spring Chinook salmon habitat in the Wenatchee River subbasin. We also compared pre-and post-fire model results of freshwater habitat for each life stage, and for the geometric mean of habitat quality across all life stages, using current compared to the historic distribution of spring Chinook salmon. We found that spring Chinook salmon are currently distributed in stream channels in which in-stream habitat for most life stages has a consistently positive response to fire. This compares to the historic distribution of spring Chinook, in which in-stream habitat exhibited a variable response to fire, including decreases in habitat quality overall or for specific life stages. This suggests that as the distribution of spring Chinook has decreased, they now occupy those areas with the most positive potential response to fire. Our work shows the potentially positive link between wildfire and aquatic habitat that supports forest managers in setting broader goals for fire management, perhaps leading to less fire suppression in some situations.Ó 2015 Published by Elsevier B.V.

Wildfire Smoke Cools Summer River and Stream Water Temperatures

“…We hope our results contribute to a more holistic understanding of wildfire‐aquatic ecosystem interactions to inform management of wildfires and wildfire smoke. Our results also add to recent research documenting diverse mechanisms through which wildfire can positively affect lotic ecosystem productivity (e.g., Boisramé et al, ; Flitcroft et al, ; Malison & Baxter, ). Together, these studies imply that in fire‐prone ecosystems, the restoration of more natural fires regimes may help recover Pacific salmon populations and other imperiled aquatic species.…”

Regional patterns of postwildfire streamflow response in the Western United States: The importance of scale‐specific connectivity

“…Wildfires are natural disturbances vital to the health of many terrestrial and aquatic ecosystems (Brown & Smith, ; Conway, Nadeau, & Piest, ; Flitcroft et al . , ). However, forest fires in the United States and elsewhere increasingly represent a threat to water supplies due to longer wildfire seasons, increasing annual area burned, and higher fire severity associated with forest densification (Dennison, Brewer, Arnold, & Moritz, ), persistent drought (Borsa, Agnew, & Cayan, ; Diffenbaugh, Swain, & Touma, ), climate change (Calder, Parker, Stopka, Jiménez‐Moreno, & Shuman, ; Rocca, Brown, MacDonald, & Carrico, ; Stavros, Abatzoglou, Larkin, McKenzie, & Steel, ), and a progressively populated wildland–urban interface (Radeloff et al .…”

A Rapid‐Assessment Method to Estimate the Distribution of Juvenile Chinook Salmon in Tributary Habitats UsingeDNAand Occupancy Estimation

“…Adult Chinook Salmon spawn in larger rivers in the presence of suitably sized substrate, and these habitats are often located in close proximity to high‐quality juvenile rearing habitats (Flitcroft et al. ). Moreover, large streams with high discharge provide increased feeding opportunities for juvenile salmon via mass transport of invertebrate food resources.…”