Regional Dynamic Vegetation Model for the Colorado Plateau: A Species- Specific Approach

Principle Investigator: Neil S. Cobb, Northern Arizona University, Neil.Cobb@nau.edu

Co-Investigators: Kenneth L. Cole, USGS Colorado Plateau Research Station
Gregg Garfin, University of Arizona
Philip B. Duffy, University of California
Jon Eischeid, University of Colorado

Collaborators: John D. Shaw, USDA Forest Service
Jimmie D. Chew, USDA Forest Service
Henry Diaz, National Oceanic and Atmospheric Administration
Deanna Pennington, University of New Mexico

Abstract:: Changes in climate alter the distribution and abundance of species, resulting in species; 1) migration, 2) adaptation to new climates, and 3) local to regional extinctions. Climate change impact studies have taken two general approaches: 1) statistically modeling changes in the future location of potential habitat for individual species, and 2) creating models simulating ecosystem processes using vegetation units. Method 1 has been criticized for not including important ecosystem processes and Method 2 has been criticized for not taking into account species-specific responses to change. Paleoecological evidence shows vegetation units (classified vegetation associations) have rarely responded as a unit; instead, past associations have been re-arranged through species-specific responses to major climate changes. We propose to integrate the two methods by predicting species-specific responses to climate change using a landscape process model.

Location: We will predict 26 plant species responses to climate change for their distributions in the western US (a sub-continental scale >2,000,000 km 2) by modeling species-specific relationships to climate. These models will then be incorporated into a regional scale (15,000 km 2) model, to make landscape-level predictions of disturbance events and processes influencing species distributions, abundance, and size classes. For this modeling effort we have selected 26 dominate plant species occurring along the 3,000 m elevation gradient from the low deserts of the Grand Canyon to the alpine tundra of the San Francisco Peaks in Northern Arizona to represent the regional study area .

Hypotheses: We hypothesize future changes in climate will cause dominant plant species to independently shift distributions, resulting in a reshuffling of plant associations. We also hypothesize many future disturbance processes influenced by climate such as bark beetle outbreaks, drought mortality, wildfire frequency, and exotic species spread, can be simulated using climate model results.

Methods: To test these hypotheses we must synthesize existing experimental and observational research to create dynamic vegetation models in order to better understand and forecast potential effects of climatic change. We will intercompare the IPCC 4th Assessment Coupled Global Climate Models (GCM) for the Colorado Plateau to select GCM output representing the range of climate change scenarios. We will also use regional and high resolution global climate models for simulations. Specifically, we will: 1)develop individual species-specific climate models evaluating changes in suitable climate, improving upon previous methods by increasing resolution 2) develop an ecosystem model at the landscape scale using the SIMPPLLE framework that simulates ecosystem processes using species-specific relationships. Species-specific mortality and migration in response to climate will be simulated under downscaled GCM scenarios in SIMPPLLE which will improve the SIMPPLLE modeling system.

Deliverables: Our modeling effort will significantly increase our understanding of how species-specific responses to climate change and related disturbances can influence ecosystem dynamics. The proposed research will significantly advance modeling efforts described in Focus 2 because it will bring together two important aspects of predicting climate change impacts, the idea that species matter and there are several processes controlling species occurrences.

last updated: 28 August 2006 PLH