Assessing the Dynamics of the Sagebrush-Steppe Ecosystem in the Context
of Restoration and Fire in Western North America using the Ecosystem
Demography (ED2) Model
Abstract
Ecosystem dynamic models have been widely used to estimate terrestrial
carbon flux and to project ecosystem structure and composition over time
and space, because of their efficiency over direct field measurements
and easy applicability to broader spatial coverage. However, such models
have also been associated with internal uncertainties, as well as
complexities arising from distinct qualities of the ecosystem being
analyzed. The widespread sagebrush-steppe ecosystem (dominated by
Artemisia spp.) in Western North America holds high ecological and
social significance, but is threatened by anthropogenic forcing factors,
including impacts from invasive species, climate change, and altered
fire regimes. To restore the ecosystem, land managers have focused on
reducing flammable vegetation and seeding native species. However, the
collective effects of restoration activities, fire, climate change, and
invasive species on ecosystem dynamics are poorly understood. We applied
the Ecosystem Demography (ED2) model to analyze its effectiveness in
predicting plant function type (PFT) composition and ecosystem fluxes,
parameterized and validated using empirical datasets for different
carbon, vegetation and fire scenarios at Reynolds Creek Experimental
Watershed (RCEW), Idaho, USA. We initialized ED2 with 20 x 40 grids of 1
km resolution representing and allowed PFTs to grow for 20 years to
reach an equilibrium state. Results showed shrubs dominating C3 grass in
a few years of time, sooner for increased CO2 and initial ecosystem
condition. A separate scenario with potential fire showed significant
loss in biomass within eight years of time. Results from this modeling
study can improve our understanding of broad-scale ecosystem processes
in sagebrush-steppe landscapes and inform land management and
restoration strategies.