EFFECTS OF HISTORIC LAND USE ON THE WHITE RIVER PLATEAU, COLORADO EXCEEDS LANDSCAPE RESPONSE TO HOLOCENE CLIMATE VARIABILITY
Holocene oxygen isotope ratios reflect hydroclimatic change on multi-decadal time scales and indicate a shift in precipitation during the mid-to-late Holocene from a rain to snow dominated seasonal balance that is typical of modern climate. Elemental data indicate greater watershed erosion concurrent with greater snowfall whereas pollen percentages are typical of the central Rockies and major taxa accumulation rates are nearly constant. The isotopes indicate that the most rapid and abrupt climate changes of the Holocene occurred in the past ~3500 years and are reflected by changes in watershed erosion, pollen and charcoal accumulation rates. However, the effects of these climate shifts are subsequently eclipsed by those after ~AD1850, including the typical decline in charcoal accumulation since ~AD 1900. We hypothesize that these changes reflect Euro-American elk hunting, fire suppression, grazing, and logging. Continuous high-resolution sampling excludes the possibility that the results are a function of sampling density. Our results indicate that the present-day WRP ecosystem is unprecedented during the Holocene, and appears to be largely a legacy of Euro-American land use.