Research Summaries

Boyd, C. S. and T. J. Svecar.
2004. Regrowth and production of herbaceous riparian vegetation following defoliation. Journal of Range Management 57:448-454.

Stubble height regulations are frequently used to manage livestock grazing of herbaceous riparian vegetation. The objective of this study was to determine the impact of stubble height, time of clipping, and soil water status on production and regrowth of herbaceous riparian vegetation. We used a randomized block design with 4 study sites on each of three small (< 2 m width) streams in northern Harney County, Oregon. In June and July of 2000-2003, 40 x 50 cm experimental plots were clipped to stubble heights of 2, 4 and 6 inches, and paired control plots were left unclipped. Complete treatment sets were located adjacent to the stream and 4 meters from the stream at each site. All plots were clipped to 1 cm in October and regrowth was calculated by comparing clipped and control plots. Water table depth was measured weekly using PVC wells. Results indicated that height regrowth was associated positively with stubble height and was less with July compared to June clipping. Weight regrowth was also positively related to stubble height and decreased with July compared to June clipping whereas annual aboveground production increased with July clipping. Annual production values for clipped plots were higher than for unclipped plots, indicating compensatory production in response to defoliation. Plots distant from the stream has less water availability, but regrowth and production were not strongly influenced by distance fro active stream channel. Timing and intensity of defoliation were reliable predictors of regrowth and production performance. Most clipping height x time combinations produced end of season heights sufficient to meet current federal stubble height requirements (4-6 inches). Our results provide insight on the timing and intensity of defoliation that will allow for adequate regrowth to meet different management objectives. However, other factors such as stream channel morphology, animal selectivity, and annual weather variation will need to be considered.

Lucas, R. W., T. T. Baker, M. K. Wood, C. D. Allison, and D. M. Vanleeuwen.
2004. Riparian vegetation response to different intensities and seasons of grazing. Journal of Range Management 57:466-474.

Sustainable management of riparian ecosystems depends on our understanding of these complex systems. Thus far, the scientific literature has not adequately addressed the effects of livestock grazing on riparian areas in the American southwest. Most available information is observational, anecdotal, based on unreplicated experiments or compares heavily grazed areas to areas from which livestock have been completely excluded. This study, in the Black Range of western New Mexico, compared effects of different seasons of use (cool season, warm season, and dormant season) and grazing intensities (light, moderate, and none) of cattle on young narrowleaf cottonweed populations and herbaceous vegetation in two adjacent southwestern riparian areas. Cottonwoods lightly grazed and moderately grazed plots received significantly greater use than cottonwoods in ungrazed plots which experienced negligible grazing pressure. Increased grazing pressure did not have significant impacts on cottonwood populations. Effects of season of use were significant on both herbaceous species richness and diversity. We conclude that no single riparian area management approach is best in all situations, but the grazing treatments used in this study appear to have been successful at maintaining riparian communities.

Evans, S. G., A. J. Pester, W. C. Leininger, and M. J. Trlica.
2004. Seasonal diet selection of cattle grazing in a montane riparian community. Journal of Range Management 57:539-545.

Cattle grazing in riparian areas has become increasingly controversial. More information is needed about cattle use of these areas to develop Best Management Practices. This study was designed to determine seasonal changes in diet selection of cattle in a montane riparian community in northern Colorado. Previous cattle diet studies in riparian zones have not separated the interaction between seasonal preference and biomass utilization. The experiment was conducted within large exclosures that had not been grazed by livestock since 1956. Vegetation biomass estimates and diet samples from 5 esophageally fistulated steers were taken during 4 grazing periods (spring, early summer, late summer, and fall) in 1995. Vegetation measurements and diet samples were also collected during the late summer and fall of 1994. One of the three paddocks in each grazing period of 1995 had been grazed in 1994. Steer diets in 1995 were found to contain 15% more Carex spp. From paddocks that had been ungrazed until 1995 compared with paddocks previously grazed in 1994. Kentucky bluegrass and forbs were consumed about 15 times and 5 times greater, respectively, in previously grazed paddocks as compared to ungrazed paddocks. Carex spp. were the most preferred component of cattle diets throughout the study. Willows were not preferred in any grazing period of either year, and consisted of less that 4% of cattle diets in any season. However, a trend towards increased consumption of willows was found from spring to fall in 1995. Information obtained in this study should help managers develop grazing systems that allow for a desirable combination of herbaceous and woody species in a riparian community while still affording grazeable forage.

Wigington, P. J., S. M. Griffith, J. A. Field, J. E. Baham, W. R. Horwath, J. Owen, J. H. Davis, S. C. Rain, and J. J. Steiner.
2003. Nitrate removal effectiveness of a riparian buffer along a small agricultural stream in western Oregon. Journal of Environmental Quality 32:162-170.

The Willamette Valley of Oregon has extensive areas of poorly drained, commercial grass seed lands. Little is known about the ability of riparian areas in these settings to reduce nitrate in water draining from grass fields. We established two study sites with similar soils and hydrology, but contrasting riparian vegetation along an intermittent stream that drains perennial ryegrass fields in the Willamette Valley of western Oregon. We installed a series of nested piezometers along three transects at each site to examine nitrate in shallow ground water in grass seed fields and riparian areas. Results showed that a noncultivated riparian zone comprised of grasses and herbaceous vegetation significantly reduced nitrate concentrations of shallow ground water moving from grass seed fields. Darcy’s law-based estimates of shallow ground water flow through riparian zone A/E horizons revealed that this water flowpath could account for only a very small percentage of the streamflow. Even though there is great potential for nitrate to be reduced as water moves through the noncultivated riparian zone with grass-herbaceous vegetation, the potential was not fully realized because only a small proportion of the stream flow interacts with riparian zone soils. Consequently, effective nitrate water quality management in poorly drained landscapes similar to the study watershed is primarily dependent on implementation of sound agricultural practices within grass seed fields and is less influenced by riparian zone vegetation. Wise fertilizer application rates and timing are key management tolls to reduce the export of nitrate in stream waters.

Kaufmann, J. B., A. S. Thorpe, and E. N. J. Brookshire.
2004. Livestock exclusion and belowground ecosystem responses in riparian meadows of eastern Oregon. Ecological Applications 1671-1679.

Ecological restoration of riparian zones that have been degraded by decades of overgrazing by livestock is on paramount importance for the improvement of water quality and fish and wildlife habitats in the western US. An increasingly common approach to the restoration of habitats of endangered salmon in the Columbia Basin of the Pacific Northwest is to exclude livestock from streamside communities. Yet, few studies have examined how ending livestock grazing changes ecosystem properties and below processes in herbaceous-dominated riparian plant communities (meadows). Along the Middle Fork of the John Day River, Oregon, we compared properties of dry (grass and forb-dominated) and wet (sedge-dominated) meadow communities at three sites that had been managed for sustainable livestock production with three sites where livestock has been excluded for 9-18 years as a means of riparian and stream restoration. Profound differences in the belowground properties of grazed and exclosed communities were measured. In dry meadows, total belowground biomass (consisting of roots and rhizomes) was ~ 50% greater in exclosures (1105 and 1652 g/m2 in the grazed and exclosed sites, respectively). In exclosed wet meadows, the total belowground biomass was 62% greater that in the grazed sites (1761 and 2857 g/m2, respectively). Soil bulk density was significantly lower and soil pore space was higher in exclosed sites of both meadow types. The mean infiltration rate in exclosed dry meadows was ~ 13 fold greater than in grazed dry meadows (142 vs. 11 cm/hr), and in wet meadows the mean infiltration rate was 233 % greater that in grazed sites (24 vs. 80 cm/hr). In exclosed wet meadows, the rate of net potential nitrification was 149-fold greater, and the rate of net potential soil mineralization was 32-fold greater when compared to grazed sites, though these changes observed in dry meadows were not significant. Livestock removal was found to be an effective approach to ecological restoration, resulting in significant changes in soil, hydrological, and vegetation properties that, at landscape scales, would likely have great effects on stream channel structure, water quality, and the aquatic biota.

Moerke, A. H. and G. A. Lamberti.
2004. Restoring stream ecosystems: lessons from a midwestern state. Restoration Ecology 12:327-334.

Reach-scale restorations are becoming a common approach to repair degraded streams, but the effectiveness of these projects is rarely evaluated or reported. We surveyed governmental, private, and nonprofit organizations in the state of Indiana to determine the frequency and nature of reach-scale stream restorations in this Midwestern state. For 10 attempted restorations in Indiana, questionnaires and on-site assessments were used to better evaluate current designs for restoring stream ecosystems. At each restoration site, habitat and water quality were evaluated in restored and unrestored reaches. Our surveys identified commonalities across all restorations, including the type of restoration, project goals, structures installed, and level of monitoring conducted. In general, most restorations were described as stream-relocation projects that combined riparian and in-stream enhancements. Fewer than half of the restorations conducted pre- or post-restoration monitoring, and most monitoring involved evaluations of riparian vegetation rather than aquatic variables. On-site assessments revealed that restored reaches had significantly lower stream widths and greater depths that did upstream unrestored reaches, but riparian canopy cover often was lower in restored than in unrestored reaches. This study provides basic information on midwestern restoration strategies, which is needed to identify strengths and weaknesses in current practices and to better inform future stream restorations.

Rains, M. C., J. F. Mount, and E. W. Larsen.
2004. Simulated changes in shallow groundwater and vegetation distributions under different reservoir operations scenarios. Ecological Applications 14:192-207.

The objectives of this study were to develop and use a linked groundwater and vegetation model to simulate groundwater and vegetation distributions in a riverine and reservoir-fringe system under different reservoir operations scenarios. The study was conducted where Little Stony Creek flows into East Park Reservoir on the east front of the Coast Range, northern California. A numerical groundwater model was used to model mean depth to groundwater during the growing season for water years 1980-1999 for each of five community types identified on the study site. Multiple vegetation models were developed, each of which described the probability that a given community type would occur primarily as a function of modeled mean depth to groundwater during the growing season and secondarily as a function of flooding. Four scenarios representing four different reservoir operations were simulated: existing condition, existing condition with late drawdown, full drawdown, and full pool. A groundwater backwater effect caused by the imposed reservoir stage extends to portions of the terrace, but the most pronounced effects occur on the delta. Consequently, the most pronounced changes in vegetation distributions also occur on the delta. Compared to the existing-condition scenario, modeled vegetation distributions do not change under the existing condition with the late drawdown scenario, a xeric herbaceous community type is greatly expanded under the full drawdown scenario, and mesic herbaceous, scrub-shrub, and forested community types are greatly expanded under the full-pool scenario. The results of this study are two-fold. First, the linked groundwater and vegetation model is relatively simple to construct and can be used to efficiently simulate multiple surface-water and groundwater management scenarios. Second, changes in reservoir operations can have pronounced effects on shallow groundwater and associated vegetation distributions in riverine and reservoir-fringe systems. Thus, the effects of changing reservoir operations must be considered if the management of shallow groundwater and associated plant and wildlife habitat resources is to be successful.

Archer, E. K., et al.
2004. Testing common stream sampling methods for broad-scale, long-term monitoring. Rocky Mountain Research Station General Technical Report 122. USDA-Forest Service, Fort Collins, CO.

We evaluated sampling variability of stream habitat sampling methods used by the USDA Forest Service and the USDI Bureau of Land Management monitoring program for the upper Columbia River basin. Three separate studies were conducted to describe the variability of individual measurement techniques, variability between crews, and temporal variation throughout the summer sampling season. We quantified the variability between crews and through time, and described the percent of the total variability attributed between crew and seasonal variability. We then estimated the number of samples needed to detect change between managed and reference sites.

Differences among streams accounted for a larger share of the total variability than did differences along observers. Stream variability was greater that 80% of the total variability for 12 of the 16 variables measured. This is somewhat surprising given the similarity between the study streams. Observer variability was minimal for stream habitat methods describing reach, streambank, and cross-sectional variables. Conversely, variability was higher for pool, large woody debris, and substrate variables. Seasonal variation was minimal for stream channel variables with the exception of substrate particle sizes. Sample sizes derived from both observer and stream variability (type I error 0.1, type II error 0.9, minimum detectable change 10%) ranged from 10 to 3502 sites to detect changes between two populations. We believe that these estimates represent an unambiguous and powerful way to display the consequences of variability to scientists and managers.

Kershner, J. L., et al.
2004. Guide to effective monitoring of aquatic and riparian resources. Rocky Mountain Research Station General Technical Report 121. USDA-Forest Service, Fort Collins, CO.

This monitoring plan for aquatic and riparian resources was developed in response to monitoring needs addressed in the Biological Opinion for bull trout (US Department of the Interior, Fish and Wildlife Service 1998) and steelhead (US Department Commerce, National Marine Fisheries Service). It provides a consistent framework for implementing the effectiveness monitoring of aquatic and riparian resources within the range of the Pacific Anadromous Fish Strategy (PACFISH) and the Inland Fish Strategy (INFISH). The primary objective is to evaluate the effect of land management activities on aquatic and riparian communities at multiple scales and to determine whether PPACFISH-INFISH management practices are effective in maintaining or improving the structure and function of riparian conditions at both the landscape and watershed scales on federal lands throughout the upper Columbia River Basin.

A list of attributes thought to be important in defining aquatic and riparian habitat conditions and their relationship with listed species was identified. The list of attributes was then translated into measurable criteria and compiled to form sampling protocols for both stream and channel parameters (Part II) and vegetation parameters (Part III). These sampling methods were tested for variability, and the results are documented in two other publications. “Testing Common Stream Sampling Methods for broad-scale, long-term monitoring” (Archer and others 2004) and “The Repeatability of Riparian vegetation Sampling Methods: How Useful Are These Techniques for Broad-scale Monitoring?” (Coles-Ritchie et al., in preparation).