Local Variability Mediates Vulnerability of Trout Populations to Land Use and Climate Change

• Published in: PloS one Vol. 10; no. 8; p. e0135334
• Main Authors: Penaluna, Brooke E, Dunham, Jason B, Railsback, Steve F, Arismendi, Ivan, Johnson, Sherri L, Bilby, Robert E, Safeeq, Mohammad, Skaugset, Arne E
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 21.08.2015; Public Library of Science (PLoS)
• Subjects: Animals; Biomass; Climate and land use; Climate Change; Climate change influences; Climate effects; Computer Simulation; Conservation of Natural Resources; Creeks & streams; Demography; Dynamic tests; Ecosystem; Emergence; Environmental aspects; Female; Fish; Fish populations; Forest biomass; Forest harvesting; Forest watersheds; Forests; Habitats; Headwater catchments; Humans; Influence; Land use; Male; Models, Statistical; Oncorhynchus clarkii clarkii; Oncorhynchus kisutch; Physiological aspects; Population Dynamics; Population statistics; Reproduction - physiology; Rivers; Salmon; Seasons; Streams; Summer climates; Temperature; Trout; Trout - physiology; Turbidity; United States; Variability; United States; Oregon; Rock Creek; California; United States > US; Pacific Northwest
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0135334

Land use and climate change occur simultaneously around the globe. Fully understanding their separate and combined effects requires a mechanistic understanding at the local scale where their effects are ultimately realized. Here we applied an individual-based model of fish population dynamics to evaluate the role of local stream variability in modifying responses of Coastal Cutthroat Trout (Oncorhynchus clarkii clarkii) to scenarios simulating identical changes in temperature and stream flows linked to forest harvest, climate change, and their combined effects over six decades. We parameterized the model for four neighboring streams located in a forested headwater catchment in northwestern Oregon, USA with multi-year, daily measurements of stream temperature, flow, and turbidity (2007-2011), and field measurements of both instream habitat structure and three years of annual trout population estimates. Model simulations revealed that variability in habitat conditions among streams (depth, available habitat) mediated the effects of forest harvest and climate change. Net effects for most simulated trout responses were different from or less than the sum of their separate scenarios. In some cases, forest harvest countered the effects of climate change through increased summer flow. Climate change most strongly influenced trout (earlier fry emergence, reductions in biomass of older trout, increased biomass of young-of-year), but these changes did not consistently translate into reductions in biomass over time. Forest harvest, in contrast, produced fewer and less consistent responses in trout. Earlier fry emergence driven by climate change was the most consistent simulated response, whereas survival, growth, and biomass were inconsistent. Overall our findings indicate a host of local processes can strongly influence how populations respond to broad scale effects of land use and climate change.