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> Abstract: Bachelet et al 2000
Bachelet, D.; Lenihan, J.; Daly, C.; Neilson, R. 2000. Interactions
between fire, grazing, and climate change at Wind Cave National Park,
S.D. Ecological Modelling. 134: 229-244.
Projected changes in global climate have important ramifications for
the future of national parks and other reserves set aside to conserve
ecological uniqueness. We explored potential implications of climate changes
on life-form distribution and growth at Wind Cave National Park (WCNP),
South Dakota, which lies on a climatically determined ecotone between
grassland and forest. Fire, promoted by healthy grasslands, is a negative
feedback limiting tree development because it kills seedlings and consumes
live foliage, thus reducing tree growth and survival. Historical records
show that fire suppression has enhanced forest expansion. On the other
hand, livestock grazing reduces grass biomass and fuel loads thus indirectly
reducing fire frequency and enhancing the expansion of forests or woodlands.
Natural fires and moderate grazing by native herbivores have maintained
the coexistence of trees and grasses but climatic variations affecting
the area's water resources can lead to dominance by either life form.
We used a dynamic vegetation model (DVM), MC1, to simulate the interactions
among climate changes, natural fire regime, and grazing pressure and their
impact on the biogeographical and biogeochemical characteristics of the
park. We used one future climate projection (HADCM2SUL) that simulates
warmer weather by the end of the next century: the temperature increase
would constrain the growth of trees that rely on the availability of deep
water, favor shrub and grass development, and promote a shift from forests
to woodlands. Woody encroachment of shrubs in grasslands areas, enhanced
by grazing, was only held in check by frequent natural fires in the simulation.