INSTREAM FLOW MODELS FOR MIXED DECIDUOUS RIPARIAN VEGETATION WITHIN ASEMIARID REGION

Empirical evidence from a semiarid watershed of the southwestern Unite d States (Verde River basin, Arizona) indicated that abundance and spe cies richness of mixed deciduous riparian forests varied in a curvilin ear and quantifiable fashion as a function of stream flow parameters. Three indicators of riparian abundance-foliage area, stem basal area a nd stand width-increased most significantly with growing season flow v olume, a surrogate indicator of riparian water availability. Tree spec ies richness varied in a bell curve fashion with flood size, with the greatest richness occurring at streams with intermediate flood magnitu des. These instream flow models have management implications for ripar ian habitats. They suggest that flow volume (and the related attribute s of water-table recharge and floodplain soil wetting) is the primary factor regulating riparian vegetation abundance in the Verde River wat ershed, and provide a first approximation of the extent of riparian lo ss expected from flow diversion or other types of flow reduction.