Linking landscape‐level change to habitat quality: an evaluation of restoration actions on the freshwater habitat of spring‐run Chinook salmon

Abstract

1. Conservation planning is often hampered by the lack of causal quantitative links between landscape characteristics, restoration actions and habitat conditions that impact the status of imperilled species. Here we present a first step toward linking actions on the landscape to the population status of endangered stream-type Chinook salmon (Oncorhynchus tshawytscha). 2. We developed relationships between land use, landscape characteristics and freshwater habitat of spring Chinook salmon in the Wenatchee River basin. Available data allowed us to find relationships that described water temperatures at several life stages (prespawning, egg incubation and summer rearing) and substratum characteristics, including fine sediments, cobble and embeddedness. Predictors included altitude, gradient, mean annual precipitation, total and riparian forest cover, road density, impervious surface and alluvium. We used a model averaging approach to account for parameter and model selection uncertainty. Key predictors were total forest cover and impervious surface area for prespawning and summer rearing temperatures; precipitation and stream gradients were important predictors of the percent of fine sediments in stream substrata. 3. We estimated habitat conditions using these relationships in three alternative landscape scenarios: historical, no restoration and one that included a set of restoration actions from local conservation planning. We found that prespawning and summer temperatures were estimated to be slightly higher historically relative to current conditions in dry sparsely forested areas, but lower in some important Chinook salmon spawning and rearing areas and lower in those locations under the restoration scenario. Fine sediments were lower in the historical scenario and were reduced as a consequence of restoration actions in two areas currently unoccupied by Chinook salmon that contain reaches with some potential for high quality spawning and rearing. Cobble and embeddedness in general were predicted to be higher historically and changed little as a result of restoration actions relative to current conditions. 4. This modelling framework converts suites of restoration actions into changes in habitat condition, thereby enabling restoration planners to evaluate alternative combinations of proposed actions. It also provides inputs to models linking habitat conditions to population status. This approach represents a first step in estimating impacts of restoration strategies, and can provide key information for conservation managers and planners.

Explaining spatial variability in stream habitats using both natural and management‐influenced landscape predictors

“…Several studies have identified similar immutable predictors as primary drivers of sediments or geomorphic conditions describing stream size (e.g. pool volume or depth) Burnett et al , ; Jorgensen et al , ). Much of the current research has shown that sediment dynamics in streams is sensitive to land use and management (Wood and Armitage, ; Kaufmann et al , ; Larsen et al , ).…”

Empirical evaluation of the conceptual model underpinning a regional aquatic long-term monitoring program using causal modelling

“…We hypothesized that precipitation is an overarching driver of the chemical, physical, and biological processes contained within the conceptual model (Feminella, 1996;Monk et al, 2008;Jorgensen et al, 2009). Essentially, we are assuming that precipitation moderates the entire casual graph.…”

Assessing freshwater life-stage vulnerability of an endangered Chinook salmon population to climate change influences on stream habitat

“…Wenatchee River Basin hydrology is dominated by snowmelt with the highest flows occurring between May and July and the lowest in August and September. See Jorgensen et al (2009) for a more detailed description of the basin. We modeled all of the major salmon-producing tributaries of the Wenatchee River, including the Chiwawa, White, and Little Wenatchee rivers, as well as Nason Creek and the upper reaches of the mainstem Wenatchee River.…”

“…Landscape attributes included total forest cover, riparian forest cover, road density, stream channel slope, elevation, precipitation, and drainage area. See Jorgensen et al (2009) for additional details of the landscape models. For this analysis, we expanded on our previous work in Jorgensen et al (2009) by re-examining the landscape models to determine the key landscape variables that could be targets for action to ameliorate climate impacts on stream habitat.…”

“…See Jorgensen et al (2009) for additional details of the landscape models. For this analysis, we expanded on our previous work in Jorgensen et al (2009) by re-examining the landscape models to determine the key landscape variables that could be targets for action to ameliorate climate impacts on stream habitat. We did this by assessing which landscape variables were most frequently present in the highest-ranked models predicting climate-linked stream habitat variables -i.e.…”