Estimating Coho Habitat Capacity in a Dynamic Landscape Using GIS-Based Variables

We are linking a dynamic landscape model with a habitat-based life cycle model for Oregon coastal Coho salmon to explore scenarios of natural disturbance and forest management.  The landscape model simulates wood and sediment inputs to the stream.  The Coastal Landscape Analysis and Modeling Study provide inputs to the landscape model of initial forest conditions and simulated responses to a variety of land management scenarios.  Modeled wood inputs to the stream are from riparian and upslope processes (e.g., tree mortality and debris flows) and modeled sediment sources are landslides and debris flows.  In-channel wood and sediment budgets are simulated for each reach.  The Coho life-cycle model is based on the approach of Nickelson and Lawson (1998).  They estimated production of egg, summer parr, smolts, adults, and spawners for each modeled stream reach.  They also estimated smolt capacity, which reflects habitat quality, from stream survey data using Oregon Department of Fish and Wildlife’s Habitat Limiting Factors Model (HLFM).  In their published model application, habitat quality was either held constant or varied uniformly over the landscape.  The research presented here builds on their efforts by introducing an explicit spatial component for both habitat quality and salmon distribution among reaches.  This is accomplished by linking outputs from the dynamic landscape model to estimate habitat capacity spatially in the landscape, which is then used in the Coho life cycle model.  Specifically, we are developing a method that estimates habitat capacities at various stages of the life cycle based on simulated estimates of sediment and wood loads, and physical characteristics of the channel from a 10-m digital elevation model.  We are using HLFM v 7.1 to calibrate our estimates of habitat capacities for a given life stage to unit-level habitat survey data collected by Oregon Department of Fish and Wildlife.  We are also using a separate validation dataset to compare our GIS-based capacity estimates with those from HLFM.  We simulated habitat capacity under different land management scenarios in the Nehalem basin to explore changes in the spatial distribution of capacity through time.