Oral Session # 87: Riparian Ecology II: Landuse, Diversity, Structure, and Function.
Presiding: M Stevens
Thursday, August 7. 1:30 PM to 5:00 PM, SITCC Meeting Room 205.

Riparian patch types as indicators of watershed hydrologic complexity.

Schmitz, Denine1, Patten, Duncan, 1 Montana State University, Bozeman, 59717

ABSTRACT- Watershed characteristics and climate drive catchment hydrology, which controls the magnitude of flood disturbance regimes. These, in turn, drive riparian vegetation dynamics. This study in the northern Greater Yellowstone Ecosystem (GYE) quantifies the relationship between watershed characteristics and the spatial structure of riparian patch types using hydrology as the common element. In the GYE, watershed alterations such as fire and grazing have modified flood magnitude and frequency consequently changing the character of associated riparian areas. Applying the Intermediate Disturbance Hypothesis, a gradient of frequency and magnitude of hydrological events should produce successional diversity represented by riparian patch type structural variability. Riparian patch types were ranked relative to average flood frequency and stream power. Flood frequency and magnitude were related to watershed characteristics using canonical correlation analysis. Once hydrologically linked, riparian patch types were then related to watershed characteristics. Recently burned watersheds in the northern GYE tended to produce riparian sites with early seral stages, which were characteristically simple in vertical and horizontal structure. Riparian sites in unaltered watersheds were generally diverse in patch type spatial structure. DCA Axis 2 scores show that patch types dominated by deciduous and herbaceous species appear to represent seral stages better than those dominated by coniferous species with those dominated by deciduous species representing intermediate stages. Thus, regions of a watershed with riparian canopies dominated by deciduous and herbaceous species are likely to yield more information through remote sensing techniques than those dominated by coniferous species. These data suggest that the character of the riparian zone through linkages to surface hydrology may be indicative of basin attributes, a useful connection for watershed management.

Key words: watershed indicators, succession, riparian patch types, hydrologic disturbance