PARENT SESSION
Oral Session #67: Metapopulations, fragmented landscapes, and patch dynamics. Presiding: C. Kraft.
Thursday, August 9, 2001. 1:00 PM to 4:30 PM. Hall of Ideas F.
Landscape changes in the semi-arid steppe of western Colorado: Impacts on winter habitat of mule deer (Odocoileus hemionus).
Manier, Daniel 1, Hobbs, N. Thompson1,2, Theobald, David1, Reich, Robin1, Campbell, Mark1, 1 2
ABSTRACT- Evidence suggests that forest expansion in many areas across the intermountain west is largely the result of suppression of wildfire and climate patterns. Domestic and wild ungulates graze extensively across this region influencing the structure of herbaceous and shrub vegetation, which also affects fire regimes and inter-specific competition. We investigated how forest encroachment, grazing pressure, and land management practices have affected the distribution of these semi-arid shrub and forest communities over a period of 57 years. Changes in these communities may offer a compelling explanation for the observed region-wide decline in the abundance mule deer populations. We hypothesized that increases in woody species cover have caused substantial declines in deer habitat across the study region. We used multi-temporal aerial photographs (1937, 1961, 1994) to estimate canopy cover of major vegetation types (e.g. Pine, Pinion-Juniper, Aspen, shrub and grasslands) on the Uncompaghre Plateau. Changes in each cover type are modeled back in time using the transition probabilities calculated from the photo interpretation. Spatial analyses and ANOVA suggest major changes associated with forest expansion and canopy closure in some areas, but little to no change in other nearby communities. Locations with change are compared with the records of human and natural disturbances for the region. We conclude that impacts of human activities on landscapes of the shrub-steppe may not be as widespread as previously believed.
KEY WORDS: landscape, change, semi-arid, aerial photography