The Ecology of Riparian Ecosystems of Northeast Oregon: Shrub Recovery at Meadow Creek and the Structure and Biomass of Headwater Upper Grande Ronde Ecosystems

Riparian ecosystems play numerous and essential roles related to the quality and flow of water, and foodlhabitat for fish, and varieties of wildlife. Due to lateral and linear linkages throughout the landscape, these zones influence the integrity of the terrestrial as well as the entire aquatic-riverine ecosystem. Since Euro-American settlement in the West, the structure and condition of many riparian ecosystems has been significantly altered. To provide tools and an ecological perspective related to riparian restoration and management, and to document late 20th century headwater riparian structure and biomass in the Upper Grande Ronde Basin, this research project was undertaken. At Meadow Creek, the response of riparian hardwood species to the termination of livestock grazing was quantified. Regression equations were developed to predict shrub biomass. Permanently marked hardwood plants were measured annually to quantify parameters ofgrowth (height, crown area, mainstem diameter, number of stems, biomass). Permanent belt transects on gravel bars were utilized to quantify rates of shrub establishment. Elk/deer-proof exc10sures allowed the quantification ofthe browsing influence of wild ungulates. In 1991, initial shrub heights and densities reflected decades of grazing pressure. Mean heights of515 woody plants (14 species) was 47 em and densities on gravel bars averaged 10.7 plants/100m 2. After two seasons without livestock grazing, mean crown volumes ofwillows (Salix spp.) increased 550% inside of wild I I ~ ungulate exclosures and 195% outside, black cottonwood (populus trichocarpa) 773% inside and 808% outside, and thin-leaf alder (Alnus incana) 1046% inside and 198% outside, respectively. Willows were significantly impeded by mule deer and Rocky Mountain elk (p<O.OI), alder sample size was too small to statistically test, and cottonwood was not significantly impeded. Impacts by deer and elk may be exaggerated due to restricted migrations and the unique wild/domestic ungulate density-dynamics within the 77 km 2 Starkey Experimental Forest big-game enclosure surrounding the study site. Establishment rates are low at this time, i.e., only 10% of previously suppressed willows produced catkins. Hardwood densities in transects increased by 5 new woody plants! 100m 2 (50m of streambank). Other non-anthropogenic factors influencing the recovery of shrubs, included beaver which removed mainstems from 20% of willows, 11% of thin-leaf alder, and 4% of black cottonwood, and active insect defoliation which was noted on 16% of willows, 7% of thin-leaf ~lder, and 0% of black cottonwood. Crude protein levels measured in willow and alder leaves was relatively high (16.1 to 16.3%) helping to explain …