RIPARIAN VEGETATION AND FLUVIAL GEOMORPHIC PROCESSES

Riparian vegetation and fluvial-geomorphic processes and landforms are intimately connected parts of the bottomland landscape. Relations amo ng vegetation, processes, and landforms are described here for represe ntative streams of four areas of the United States: high-gradient stre ams of the humid east, coastal-plain streams, Great Plains streams, an d stream channels of the southwestern United States. Vegetation patter ns suggest that species distributions in the humid east are largely co ntrolled by frequency, duration, and intensity of floods. Along channe lized streams, vegetation distribution is largely controlled by variat ion in fluvial geomorphic processes (cycles of degradation and aggrada tion) in response to increases in channel gradient associated with cha nnelization. Similarly, riparian vegetation of Great Plains streams ma y be controlled by fluxes in sediment deposition and erosion along bra ided streams. Patterns of riparian vegetation in semi-arid regions may be most closely related to patterns of water availability, unlike mos t other streams in more humid environments. Channel-equilibrium condit ions control stability of the coincident fluvial landform and attendan t vegetation pattern throughout the continent. In most situations, rip arian-vegetation patterns are indicative of specific landforms and, th us, of ambient hydrogeomorphic conditions.