Climate change could alter the population growth of dominant plant species, leading to profound effects on community structure and ecosystem dynamics. Population models are powerful tools for predicting species’ responses to climate change: if we can understand how populations responded to historical climatic variation, we can then predict population responses to future climate. Here we illustrate the population modeling approach using a unique, long-term dataset from northeast Idaho. We parameterized Integral Projection Models for key range species (Pseudoroegnaria spicata, Hesperostipa comata, and Artemisia tripartita) to identify the demographic rates and climate variables most important for population growth. For the shrub, lower previous year’s precipitation increased survival and population growth. For the bunchgrasses, increased February and March snowfall and winter precipitation increased survival, though February and March snowfall increased population growth more than winter precipitation alone. Future shifts from a snow- to rain-dominated winter precipitation regime could decrease the abundance of perennial grasses relative to shrubs, resulting in decreased forage availability for domestic and wild ungulates. Evaluating the influence of climate variability on the population dynamics of these species requires several years of observations due to the lagged effects of snow and precipitation on survival and growth. Our historical analysis suggests that future work should focus on understanding the interactions among grazing management (which can affect population size structure), winter precipitation regimes and population dynamics in order to forecast the effects of climate change on the structure and function of the sagebrush steppe ecosystem.
Available at: http://works.bepress.com/peter_adler/91/