Abstract
An understanding of the ecological health of stream systems and riparian areas in Yellowstone National Park (YNP) requires knowledge of their response to climatic and hydrological influences; intrinsic factors such as relief and geological materials are important influences as well (e.g., O'Hara and Meyer 1995). Recent studies of southwestern (Ely et al. 1993) and midwestern U.S. rivers (Knox 1993) have shown that relatively minor climatic changes in the late Holocene are associated with large fluctuations in flood magnitude and frequency. In small, steep drainage basins of northeastern YNP (Figure 1), Meyer et al. (1992, 1995) associated increased fire-related debris-flow activity with decadal to millennial-scale cycles of drought over the Holocene. Observations of modern events indicate that debris-flow and flash floods are also produced in the absence of fire in this rugged mountainous region, primarily by intense summer thunderstorm precipitation. Although a correlation between drought severity and fire magnitude in Yellowstone is clear (Balling et al. 1992a, 1992b), the relationship hypothesized by Meyer et al. (1992,1995) between warm, drought-prone climatic episodes and debris-flow activity in this region requires further investigation. Therefore, we use relatively high-resolution lichenometric and treeÂring dating methods to construct a 250-year history of major hydrologic events in small, steep tributary basins of Soda Butte Creek in northeastern Yellowstone. This period spans the transition from the generally cooler global climate of the Little Ice Age to the present (e.g., Grove 1988). Although the Little Ice Age was not uniformly cold in either a spatial or temporal sense (Jones and Bradley 1995), and YNP climate is not well known in the earlier part of this interval, trends toward increasing summer temperatures and decreasing winter precipitation in YNP over the last ~100 yr are consistent with this transition (Balling et al. 1992a).