climatic variability, land-cover change, and forest hydrology in the pacific northwest david w....
Post on 22-Dec-2015
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Climatic variability, land-cover change, and forest hydrology in the Pacific NorthwestDavid W. PetersonJISAO Climate Impacts GroupForest Hydrology
Current Research:Climate – Water – Forest
Interactions
Climate
Water Forests
Water and ecosystem productivity
Annual Outflow Gross photosynthesis
Numeric Terradynamics Simulation GroupUniversity of Montana
Forest dependence on water resources in the PNW
Trees require water for photosynthesis and growthSummer water deficits limit forest productivity Total precipitation Seasonality of precipitation
At high elevations, excessive snowpack limits growing season length and forest productivityWater availability influences forest species composition and density
Forest influences on water resources
Forests influence water resources by… Intercepting precipitation Influencing infiltration and runoff rates Modifying soil water-holding capacity Extracting soil water to meet
transpiration requirements Influencing snowpack accumulation
and melt rates
Water and ecosystem productivity
Annual Outflow Gross photosynthesis
Numeric Terradynamics Simulation GroupUniversity of Montana
Land-cover changes
Disturbances (variable intensity) Forest harvesting Wildfires Insects and diseases Land conversions
Forest growth and development Forest structure Leaf area Species composition
Climate change
Climatic variability and change
Annual climatic variability and ENSO Affect forest stress levels Extreme events can disturb forests
Decadal climatic variability (e.g., PDO) Forests may acclimate to new conditions Problems switching from wet to dry?
Atmospheric carbon dioxide concentrations Will higher CO2 levels reduce forest water use?
Climate change – temperature/precipitation
Simulation model approach
Identify likely hydrological impacts of: Vegetation changes Climatic variability
and change Soils and
topography
Integrate results across the region
Hydrological responses
Snowpack water storage and snowmeltSoil water storage Infiltration versus runoff Summer water deficits – severity and
duration of plant stress
Transpiration and evaporationRunoff and baseflow
Forest cover changes due to forest harvest and regrowth
Brush cover(post-harvest)
Mature forest(50-60 yr)
Mica – Potlach Watershed, Idaho, 1933-1990
Forest cover and snowpack
As forest coverincreases…
… spring snowpack declinesby up to 20%March 1 May 1
Forest density affects water use and soil water storage
Forest density affects surface runoff and baseflow
Questions to be addressed…
How will future climate and vegetation changes affect surface water fluxes and soil water storage in PNW forests?Which has a bigger impact on forest hydrology – climatic variability or vegetation change?What are the hydrological implications of changes in forest management practices?How might future changes in water resources affect forest productivity and species composition?
Presentation OutlineForest – water interactions Forest dependence on water resources Forest influences on water resources
Effects of land-cover change and climate on water cycling in PNW forest ecosystems Types and effects of land-cover changes Effects of climatic variability Interactions between climate and forest cover