Plant Community Development in a Dryland CREP in Northeastern Oregon

Abstract

Riparian areas in dryland crop regions of the Intermountain Pacific Northwest have largely been converted to cropland or pasture during the last 140 years. Some formerly cultivated floodplains have become difficult to farm; enrollment of these lands into conservation programs provides the opportunity to use them as wildlife habitat and as buffer areas near streams. Our objective was to evaluate plant community development on an USDA Conservation Reserve Enhan- cement Program site in northeastern Oregon from when the plant was planted in 1999 through 2008. The research was designed as a descriptive study. We established permanent line-transects to quantify vegetation establishment and changes in species composition through time. We collected data in 2000-2001 and 2007-2008. Vegetation cover in 2000-2001 was 100%, dominated by tall wheatgrass. Living plant material cover decreased from 98% in 2000-2001 to 33% in 2007 and 68% in 2008; dead plant residue significantly increased and tall wheatgrass cover decreased. Native species were present in similar percentages from 2000 to 2008, although there was a shift from target to nontarget species. The 1999 seeding can be judged a success because of the ground cover provided and the establishment of one target species, tall wheatgrass. However, the increased ratio of dead to living plant material and shift to non-target annual weed species suggests that more active management (i.e., fire, grazing, or mowing) of the tall wheatgrass stand is needed to maintain its productivity and/or a healthy mix of multiple species.