Some Responses of Riparian Soils to Grazing Management in Northeastern Oregon

Abstract

Infiltration, sediment production, penetrometer penetrability and bulk density were measured on control/treatment paired plots of several grazing schemes in a riparian zone of northeastern Oregon. Treatments were in effect over a period of 5 years. Restrotation favored the hydrologic parameters measured, while deferred rotation and season-long did little to enhance, and sometimes hindered, hydrologic expression. Late-season grazing in September demonstrated a positive hydrologic response, whereas Iateseason grazing in October was negative-probably due to the onset of fall rains and a change in soil moisture conditions. Although land managers generally acknowledge that the rate at which an upland soil accepts water largely determines erosion rates, surface ponding, soil moisture, and ground water recharge, little attention has focused on infiltration in riparian areas. Infiltration into the soil may influence stream systems because erosion delivers sediment and nutrients to the stream, and discharge and dissolved salt concentrations respond differently to runoff and groundwater flows (Morisawa 1968). Infiltration, therefore, may be of particular interest in a riparian zone, which is the last terrestrial area water crosses before entering the stream. Furthermore, compactionand low infiltration rates may interfere with the riparian zone’s function as a stream source area. These areas contribute to streamflow according to rainfall characteristics and the water storage and transmission properties of the soil (Branson et al. 1981).