SHEEP CREEK TOUR

GRAZING IN THE RIPARIAN ZONE

AND WATER QUALITY-QUANTITY ISSUES

Research Highlights

Sponsored by

Departments of Rangeland Ecosystem Science and Earth Resources
College of Natural Resources
Colorado State University

Agricultural Experiment Station
Colorado State University

Civil Engineering Department
University of Wyoming

and

United States Department of Agriculture
Agricultural Research Service

and

U.S. Forest Service
Canyon Lakes District

Eaton Reservoir has a storage volume of approximately 3800 acre feet. Water diversions from the Wilson Ditch supplement the natural streamflow generation from the upper watershed. A mean annual water yield of 13 cm on an area basis produces 3000 acre feet per year. Diversions volumes range from 300 acre feet to approximately 4400 acre feet per year, depending on the spring snowpack water content and downstream needs.

The annual hydrograph for Sheep Creek is bimodal. The initial snowmelt hydrograph increases to a peakflow of approximately 50 cfs and then quickly decreases. Water is held in Eaton Reservoir until called by downstream water rights. Water is then released from the Eaton Reservoir. The release is literally opening the dam gates and draining the reservoir. Peakflows are approximately 50 cfs and have steep rising and falling limbs (see figure). Releases are stored in the lower Halligan Reservoir for subsequent delivery downstream. The mean annual water yield increase from Upper Sheep Creek from Wilson Ditch additions is 15 percent. The water release rate is approximately 50 cfs, equaling the spring snowmelt flows. The flow augmentation by the Eaton Reservoir-Wilson Ditch system has increased Sheep Creek low and mean flows. Peakflows are less affected as the release flow rates often approximates the snowmelt hydrograph.

Water quality in Sheep Creek is excellent and reflects the high mountain granitic parent material. The designated beneficial uses are Aquatic Life - Class 1 Cold Water, Recreation Class 1 - Primary Contract, Water Supply, and Agriculture. Little to no water quality monitoring has been done in Sheep Creek. Our research represents the first routinely collected water quality data. See the following abstracts for more details.

In general, it is the conclusion of this team that conditions in Sheep Creek have been improving over time. This improvement includes riparian areas, channel condition in the main stem Sheep Creek, the Wilson Ditch, and management of Eaton Reservoir releases. The basin was probably more disturbed in the late 1800's than in the past 5 decades. During the later part of the 19^th century, the Forest Service had not yet been established and grazing and timber harvesting were proceeding at a destructive rate. Since 1902, when lands in Sheep Creek have been excluded from public domain and under the stewardship of the Forest Service, the health of the watershed has improved. However, at late as 1956, erosion from flow diversions and flow releases was recognized. To resolve these and other problems, the Forest Service initiated several management strategies including exclosures, limited flow releases from Eaton Reservoir, and closure and revegetation of roads. Exclosures have improved canopy cover and increased fish populations. The limited flow releases may be responsible for the improved condition of the main stem Sheep Creek. Closure and revegetation of roads may be responsible for a decrease in road density from 1956-1994 observed in Deadhorse Basin. Deadhorse Basin had the highest area timber harvested (18%) of any sub-basin.

Timber harvesting is proposed for the Green Mountain area (Trout Creek and Green Mountain basin) and Beaver Creek. Based on the erosion condition from 1994 photos, Beaver Creek is rated 12^th, Trout Creek is rated 8^th, and Green Mountain basis is rated 10^th. In an analysis of possible cumulative watershed effects based on past management practices, Beaver Creek has the second highest ranking. According to our analysis, timber harvesting in Beaver Creek and Green Mountain basin can proceed if implemented with BMPs.

The success of the exclosures in the riparian areas indicates that this is a management activity that should continue. However, rotational grazing may be allowed in these exclosures if it is limited spatially and temporally. Rotational grazing will include choosing the optimum season for grazing based on grass species. We suggest that grazing can continue at the current AUM level (250) if recreational vehicles are prohibited from the riparian areas. If livestock AUMs are to increase, then a monitoring program should be established in the riparian zone. Monitoring should include vegetative transects, fish habitat condition and population, photographic points, enforcement of regulations, and monumented geomorphic surveys.

Management fires are being prescribed for Sheep Creek to reduce fuel loading and increase the amount of aspen. Sub-basins rated with over 50% of their basin area as 'high' fire hazard include: Deadhorse Basin, Lower Sheep Creek, and Trout Creek. Therefore, these are areas that should be restricted from management prescribed fires.

Flow augmentation and flow released from Eaton Reservoir were labeled a management concern. According to our analyses, flow augmentation above Eaton Reservoir has resulted in substantial increase in the magnitude of low to average peak flow. These flow have recurrence intervals of 2-2.5 years and are described as channel-forming flows. This may have substantially altered channel morphology in the upper reaches. Field reconnaissance of these reaches may verify these suggested problems. In addition, this area should be monitored through monumented cross-sectional surveys to quantify long-term channel changes. If channel morphologic changes are occurring, then flow diversions will have to be controlled more effectively. Below Eaton Reservoir, flow releases have both beneficial and detrimental effects on channel and riparian habitat. The difference in effects are related to the timing and magnitude of releases. Therefore, no strong conclusion can be made about the current effect of flow releases from Eaton Reservoir. It is concluded that the channel below Eaton Reservoir is in an improved condition since 1956.

Past land uses in Sheep Creek, such as mining, recreation, and grazing, may have impacted water quality; but the data is too sparse to reach any conclusions. A background water quality study should be conducted to determine the status of the water quality in Sheep Creek.

Fencing was used to protect 40 hectares of riparian stream habitat along 2.5 km of Sheep Creek, Colorado, from adverse impacts caused by heavy streamside recreation use and cattle grazing. Fish habitat within the fenced areas was narrower, deeper, and had less streambank alteration, and better streamside vegetation than comparable unfenced sections. Estimated trout standing crop was twice as great, and proportional stock density (PSD) was higher in exclosures than in unfenced sections. There was a higher proportion of nongame fish present in unfenced sections. Projected fishing opportunities within the fenced sections were double those estimated for a comparable length of unfenced habitat along the same stream.

Terry Tucker Schulz and Wayne Leininger

The valuable role that healthy riparian ecosystems play in regional diversity of plant and wildlife communities is beginning to be recognized. Resource managers need to know how degraded riparian areas respond to changes in management, such as reduction or elimination of grazing. Differences in vegetation structure were examined in a montane riparian zone in north-central Colorado after 30 years of cattle exclusion and continued, but reduced, grazing pressure. Canopy coverage, density, and standing crop of important riparian plant species were measured in 1985 and 1986 to assess the changes in the riparian community. Total vascular vegetation, shrub, and graminoid canopy cover was greater (P0.05) in the exclosures as compared to grazed areas, while forb canopy cover was similar (P>0.05) between treatments. Exclosures had nearly 2 times the litter cover, while grazed areas had 4 times more bare ground. Willow canopy coverage was 8½ times greater in protected areas than in grazed areas. Kentucky bluegrass (Poa pratensis L.) cover was 4 times greater in grazed areas than exclosures, while the cover of fowl bluegrass (Poa palustris L.) was 6 times greater on the protected sites. Canopy cover of other important riparian species, such as tufted hairgrass (Deschampsia caespitosa), Nebraska sedge (Carex nebraskensis), and beaked sedge (C. rostrata), was similar (P>0.05) between treatments. Mean peak standing crop over the 2 years of the study was 2410 kg/ha in the exclosures, and 1217 kg/ha in caged plots within grazed areas. Cattle utilized approximately 65% of the current year's growth of vegetation during the 1985 and 1986 grazing seasons.

Terry Tucker Shulz and Wayne Leininger

Bird and small mammal populations were examined in a montane riparian zone in north-central Colorado following 30 years of cattle exclusion and continued, but reduced, grazing pressure. Strip transects were sampled for birds within the riparian zone from May through June, 1986. Wilson's warbler (Wilsonia pusilla) was found only inside livestock exclosures, and Lincoln's sparrow (Melospiza lincolnii) was twice as abundant in the exclosures when compared with grazed areas. Conversely, the American robin (Turdus migratorius) was twice as abundant in grazed areas when compared with numbers observed within livestock exclosures. Other species, such as ruby-crowned kinglet (Regulus calendula) and dark-eyed junco (Junco hyemalis), appeared to be unaffected (P>0.05) by cattle grazing. Small mammals were trapped from July through August, 1986. The western jumping mouse (Zapus princeps) was the dominant small mammal in the exclosures, while the deer mouse (Peromyscus maniculatus) dominated grazed areas. Exclusion of cattle from the riparian zone led to changes in the vegetation structure, resulting in changes in the species composition of nongame communities, while the level of diversity was maintained.

Carlo A. Popolizio, M.S. Range Science, 1990

Western montane riparian ecosystems are composed of mesic vegetative communities and associated faunas found between an aquatic environment and xeric upland sites. These ecosystems were detrimentally impacted by road construction, logging, mining, grazing, hunting, fishing, trapping, recreational developments, agricultural conversions, and water use. This study provided the opportunity to assess ecological condition and successional status of montane riparian vegetation. Moreover, it established a trend study by quantitative measurements of percent relative cover, percent composition, percent relative frequency of vegetation, and density of selected forbs in long-term and short-term grazed and ungrazed treatments. This study provided three replications of each treatment.

Data were collected in August 1988, June 1989, and August 1989, employing random, permanent plots and transects. Photographs of permanent plots and the general area were taken at the end of each sampling period.

Means for cover of bare ground, legumes, common dandelion (Taraxacum officinale Wiggers), and white Dutch clover (Trifolium repens L.) were significantly different among treatments. Sedges and forbs were least affected by treatments. Differences in mean foliar cover of all life forms and selected plant species were not significant over time.

Ecological condition was good under long-term protection and short-term grazing, but only fair under long-term grazing and short-term protection. Sedges were assumed to decrease under grazing, but various researchers stated that some species may increase in grazed areas.

Good correlations between density and cover of common dandelion were obtained for all treatments. This may allow researchers of riparian areas within the Rocky Mountains to estimate dandelion numbers from cover values at various levels of grazing.

Riparian areas are important ecosystems in rangelands, and the impact of livestock grazing on runoff and soil loss in riparian areas is a major concern of society. Actual runoff and soil loss data are often not available, but hydrologic simulation models make it possible to simulate hydrologic response to grazing when measured data are incomplete. The Sheep Creek exclosures in the Roosevelt National Forest in Colorado have a 30-year history of livestock exclusion. Surface runoff and soil loss from Sheep Creek riparian areas were simulated using the Areal Non-Point Source Watershed Environment Response Simulation (ANSWERS) model. Both grazed and ungrazed areas were considered.

The ANSWERS model is a distributed, physically-based model. It utilizes single rainfall events for simulation. The riparian study area was divided into square elements. The model simulations were run for daily rainfall events, with synthetic intensities derived from a type-modeled storm. ANSWERS model parameters were estimated from infiltration measurements, soil bulk density, and vegetation cover data collected from 1985 through 1989 from the grazed and ungrazed areas. Best estimates from the literature were used for parameters that were not determined on site.

The mean runoff, soil loss, maximum erosion, and maximum deposition rates estimated by the ANSWERS model were significantly higher for the grazed areas than for the ungrazed area, although the ANSWERS model gave low runoff and soil loss from both the grazed and ungrazed areas. This is attributed to good hydrologic properties of soil, adequate ground cover, flat topography, and high organic matter content in soils, all of which reflect high infiltration rates.

The ANSWERS simulations were very sensitive to changes in steady-state infiltration rates and slope, moderately sensitive to control zone depth-bulk density interactions, control zone depth, return periods, and maximum infiltration rate in excess of steady-state infiltration rate. The model results were least sensitive to plant cover and soil bulk density parameters estimated from the site data. Evidence indicated that livestock grazing in the Sheep Creek riparian zone reduced infiltration, which, in turn, increased runoff and soil loss.

Amanda Clements, M.S. Range Science, 1990

Many riparian areas throughout the western United States have deteriorated as a result of improper livestock management. As the desire to improve riparian management has increased, the need for more accurate understanding of riparian vegetation response to defoliation has arisen. This study was designed to detect the phenological stages during which Nebraska sedge (Carex nebraskensis Dewey), and planeleaf willow (Salix planifolia Pursh.) are least vulnerable to defoliation. A second focus was to assess plant vigor in response to defoliation intensity.

The study was conducted over one year. Nebraska sedge and planeleaf willow were clipped once at light, moderate, or heavy intensities to remove approximately 30, 60, and 90% of current year's growth. Plants were defoliated at one of four phenological stages that corresponded to either spring, early summer, late summer, or fall. An unclipped control and treatment representing season-long continuous use were also included. An estimation of Nebraska sedge vigor was made at the end of the growing season on the basis of shoot population structure, flowering characteristics, shoot height, aboveground biomass, and belowground total nonstructural carbohydrate (TNC) concentrations. Vigor of planeleaf willow was estimated through twig growth and elongation, bud activity, tissue death, aboveground TNC concentrations, and morphological characteristics.

Fall and spring were the least harmful periods for short-term defoliation of Nebraska sedge, as indicated by 30% greater new shoot production compared to late summer clipped plants, 54% more flowering shoots, and 45% taller shoots. Defoliation intensity affected only shoot height and leaf length for Nebraska sedge. Fall was the least harmful period for defoliation of planeleaf willow, followed by spring, and then summer periods. Fall-treated plants had 52% greater twig production, and 83% more new twigs initiated than summer-treated plants. Heavy defoliation influenced willow response to season of clipping for some responses observed; and differential responses to clipping intensity were apparent during some seasons.

Maria Bemhaja, M.S. Range Science, 1990

A greenhouse study was conducted to determine how a perennial riparian grass (Deschampsia caespitosa L. Beauv.) and sedge (Carex nebraskensis Dewey) responded to four different factors: frequency and intensity of defoliation, nitrogen fertilization, and interspecific competition under non-limiting soil water conditions. Plant variables of above- and belowground biomass and carbohydrate reserves were used to assess how these two important herbaceous species reacted to manipulations. Competitive ability of these two species, either along or in a mixture (50-50), were determined under three frequencies of clipping (every 2, 4, or 6 weeks), two intensities of clipping (2.5 and 5.0 cm stubble height), and at two levels of added nitrogen (0 and 100 kg N/ha).

Significant differences in aboveground biomass production and root biomass for both species and the mixture were detected among plants that were clipped at varying frequencies. Aboveground biomass production for the grass, sedge, and mixture produced 31, 19, and 22%, respectively, more biomass when clipped every 6 weeks as compared with plants clipped every 2 weeks. Roots of the grass, sedge, and mixture clipped every 6 weeks had 12, 33, and 100% more mass, respectively, than when clipped every 2 weeks. A moderate intensity of use (5.0 cm stubble height) had little effect on above- or belowground biomass production of the sedge. However, root biomass of the grass and the mixture was significantly reduced by clipping at either a 5.0 or 2.5 cm stubble height.

Number of tillers were significantly affected by clipping frequencies by the end of the experiment. Number of tillers of the grass, sedge, and the mixture in treatments clipped every 6 weeks had 51, 45, and 25%, respectively, more tillers than when similar plants were clipped every 2 weeks.

Addition of nitrogen fertilizer resulted in a significant increase in aboveground biomass and number of tillers of D. caespitosa when grown in a monoculture. Leaf senescence was reduced in both species under high nitrogen fertility.

C. nebraskensis had greater root biomass, lower shoot/root ratios, and higher root TNC pools than did D. caespitosa under all the clipping treatments.

Results obtained suggested that the most frequent clipping (clipped every 2 weeks) and the most intense defoliation (2.5 cm stubble height) treatments could not be sustained by these species. This intensity of use may compromise future biomass production, performance, fitness, and persistence of the two species.

Sara Beth Mayben, M.S. Range Science, 1990

The valuable role of woody plants in maintenance of healthy riparian ecosystems has been well documented. Resource managers need to have fast, reliable techniques available to estimate utilization of woody browse. Various models were constructed for six species of montane willows to determine the relationship between stem diameter and weight. A general linear model that used stem basal area best represented this relationship. Although one specific model of all species had a high correlation coefficient (r=.85), two models best explained the relationship between stem basal area and biomass for the six willow species. Two species of willow that generally occupy lower elevation ranges (Salix exigua and S. lutea) were included in one group, while the remaining four willows on the study site (S. amygdaloides, S. drummondiana, S. planifolia and S. wolfii) comprised the second group.

A rainfall simulation experiment was conducted in the laboratory to study soil loss as affected by different types and amounts of surface cover. Results of this laboratory work were used to develop a refined surface cover submodel for use in the Revised Universal Soil Loss Equation (RUSLE) and to determine the cover types that would provide adequate protection of soil from raindrop impact and overland water flow. It was anticipated that this refined surface cover submodel would improve the predictability of soil loss in RUSLE so that it might be more effectively used for rangeland watersheds.

The experiment was designed in such a way that it provided for a wide range of cover types combinations. A simplex lattice design was used to reduce the total number of treatment combinations. A total of 105 plots for various amounts and types of surface cover were exposed to simulated rainfall at 100 mm/h for 30 min. Cover treatments included herbaceous litter of Carex spp. and Poa spp., shrub litter of Salix spp., small rocks (average length = 22.0 mm and average width = 15.4 mm), and mixtures of these cover types at several levels of cover (25, 50, 75, 100%), and bare soil (control).

Multiple regression was used to determine the refined surface cover subfactor (RSC) that best fit the experimental data. A coefficient of determination (R²) of 0.94 was obtained, which indicated that most of the soil lost from laboratory plots could be accounted for by the type and amount of cover.

Validation of the RSC was performed by comparing current RUSLE predictions of soil loss with those predicted by the refined RUSLE model using the same field data. Predicted values of soil loss from both the original and revised versions of RUSLE were then compared with actual field measurements of soil loss from the Reynolds Creek Watershed in Idaho (John and Gordon 1988) to determine if the RSC had improved the predictability of RUSLE for use on rangelands. In addition, parametric analysis was conducted to determine the effects that various RUSLE parameters had on soil loss simulations.

Soil loss was significantly reduced by vegetation litter. No significant difference was detected in soil loss between herbaceous litter and shrub litter when either covered the soil surface. A surface cover proportion of about 0.60 by vegetation litter, 0.70 by combinations of vegetation litter and gravel, (when vegetation litter was in higher cover proportion than gravel), and 0.75 by gravel reduced soil loss to 5000 kg/ha, assumed as an upper limit of the acceptable level of soil loss tolerance for rangelands (Moldenhauer 1982). Gravel cover was not as effective as herbaceous litter or shrub litter in protecting the soil from water erosion. However, a surface coverage of 100% by combinations of vegetation litter and gravel offered the best protection of the soil against erosion by water than did either 100% vegetation litter cover or 100% gravel cover alone.

Model predictions of soil loss were mostly affected by slope steepness, surface cover, bare soil, and surface roughness. The refined RUSLE model underpredicted average soil loss from a rangeland by about 3 times, as compared with observed data. However, RUSLE underpredicted average soil loss by about 20 times when the original version of the surface cover subfactor (SC) was used. Therefore, the use of the RSC in RUSLE improved the predictive ability of the RUSLE model to simulate observed soil loss from an Idaho sagebrush-grass range site.

The regression equation developed as RSC in this study for use in RUSLE is an improvement over the original equation (SC) as the RSC takes into account the type and amount of surface cover. The RSC is proposed as a satisfactory quantitative expression for inclusion as a surface cover subfactor in RUSLE to predict soil loss from rangeland watersheds. However, additional testing of RSC on other rangeland types is needed. In addition, more research work is needed to determine effectiveness of surface rock cover to reduce soil loss.

Cattle grazing has had a profound effect on plant communities within riparian areas throughout the western United States. Willow (Salix spp.)communities are a common feature of the montane riparian area. A better understanding of the effects cattle grazing has on the dynamics within the willow community is needed to better manage livestock and preserve, replenish, and promote willow stands along western mountain streams.

Data were collected from a montane willow community in northcentral Colorado from 1988 to 1991. The area had been heavily grazed by cattle from before the turn of the century. Three large exclosures were established in 1956 along Sheep Creek to prevent grazing along sections of the stream. In 1988, 3 new exclosures were constructed along previously grazed reaches of the stream, and portions of the 3 older exclosures were opened up to grazing. This created 4 grazing treatments: long-term grazing, long-term livestock exclusion, recent livestock exclusion, and recent grazing.

Data were collected on willow height, density, and canopy coverage at randomly selected plots within the 4 grazing treatments. These data were analyzed to determine effects of different levels of grazing on willow height, density, and canopy coverage of willow overstory and herbaceous understory.

Willows increased in height during the 3 years of study across all treatments. Cattle grazing had little effect (P>.05) on the growth of willows. Willow density increased (P.05) in the recent exclosures over the course of the study in response to livestock removal. The other treatments showed little effect (P>.05) from livestock grazing.

Overstory canopy cover, consisting almost solely of willows, had little discernible effect (i.e., low r² values) on canopy coverage of herbaceous understory. Willow canopy cover remained the same (P>.05) over the period of study. In contrast, canopy coverage of understory composed of grasses forbs increased, regardless of the grazing treatment.

The mountainous riparian corridor performs important hydrologic functions in western rangelands, by transferring nutrients from upslope ecosystems to streams. The riparian corridor along Sheep Creek, Colorado, was studied to determine if variations in nitrate-nitrogen concentrations were the result of spatial and temporal variations, and if cattle grazing affected nitrate-nitrogen concentrations.

Four different stream cross sections were sampled from June 25, 1991 to October 9, 1991. These cross sections encompassed the stream, the riparian corridor, and the upslope ecosystem. Statistical analyses included the Multi-Response Permutation Procedures (MRPP) to compute p values, which were compared to an alpha of 0.10 to determine significant differences.

The nitrate-nitrogen fluxes calculated over the entire 16 week period were as follows: 0.63 g/ha/day, 0.41 g/ha/day, 0.41 g/ha/day, and 0.58 g/ha/day for Cross Sections #1, #3, #5, and #7, respectively. Three flow periods were defined based on changes in discharge, including a variable source area flow (Flow Period #1), the release of the Eaton Reservoir (Flow Period #2), and the autumn low flow (Flow Period #3). An increase in discharge (>0.25 cms) resulted in a corresponding decrease in nitrate-nitrogen concentrations, showing a flow dilution effect.

Cattle grazing was not a factor in finding significant differences in nitrate-nitrogen concentrations. This could be because the intensity of grazing during the study was too low to show any significant impacts. Another possible explanation is that other variables, such as hydrology, vegetation, soils, and channel morphology had a greater impact than the potential negative effect of cattle grazing.

The effects of previous intensive grazing on soil hydrologic properties, leaf area, transpiration, and water use were studied within grazed and ungrazed areas in a montane riparian ecosystem in northern Colorado. Soil moisture content, bulk density, porosity, and infiltration rates were measured during the 1986, 1989, and 1990 growing seasons. Seasonal changes in leaf area, transpiration, and water-use efficiency were measured in four graminaceous species (Carex nebraskensis Dewey, Carex rostrata Stokes, Juncus balticus Willd., Poa pratensis L.), one herbaceous species (Taraxacum officinale Weber), and three willow species (Salix drummondiana Barrat in Hook., Salix lutea Nutt., Salix planifolia Pursh.).

Soil bulk density increased and infiltration rates decreased in grazed areas during the 1986 growing season. Infiltration rates improved in the grazed areas following a decline in the number of cattle grazing on the allotment during the summers of 1989 and 1990, but bulk density increased in both grazed and ungrazed treatments.

Herbaceous and graminaceous species growing in grazed sites had higher leaf-area indices, transpiration rates, and water-use efficiencies than conspecifics growing on ungrazed sites. Willows had greater leaf area in ungrazed areas, and S. planifolia consistently had lower leaf-area indices, transpiration rates, and higher water-use efficiency than either S. lutea or S. drummondiana. The willows also had higher or comparable water-use efficiencies than the dominant graminaceous and herbaceous species.

Output from a model (WILLOWS) that predicted daily and seasonal transpiration at the level of an individual willow shrub and a 1-ha willow stand followed the same trend as that from a portion of a more mechanistic model, DAYTRANS (Running 1984). However, the WILLOWS model predicted only about one-third the transpiration rate as that predicted when DAYTRANS was run using the same data.

The results of this study indicated that some level of grazing might stimulate growth of herbaceous and graminaceous species in riparian communities without markedly altering soil hydrologic conditions or plant water use. Because the willows reduce evaporative demand through shade and cover, a combination of shrub species and herbaceous and graminaceous species may maintain ground cover and reduce transpiration loss in this montane riparian ecosystem.

Planeleaf willow (Salix planifolia) is an important woody component of montane riparian ecosystems. Years of season-long heavy grazing have significantly altered both the amount and type of vegetation in riparian communities. Some nonriparian species have been shown to be able to deter herbivory by means of secondary compounds. Information on the relationship between herbivory and the presence of secondary compounds in riparian species is conspicuously absent in the literature.

Initial work on planeleaf willow revealed the presence of ampelopsin (3,5,7,3',4',5'-hexahydroxydihydroflavonol, also called dihydromyricetin), and high levels of condensed tannins, while only low levels of phenolic glycosides were noted. Ampelopsin has been documented in willows in Europe and Japan, but this is the first time it has been isolated from a willow native to the United States.

The purpose of this study was twofold. First, ampelopsin was isolated (T. Clausen, pers. comm.) and identified by comparison with spectral data (UV and spectral shift analysis) from the literature. Second, a study involving areas with 4 different histories of grazing was initiated to determine effects of grazing on levels of ampelopsin. Levels of ampelopsin in planeleaf willow were not affected (p>0.05) by livestock grazing. Variation within replicates was large enough to cancel any possible treatment effects. Chronological effects were generally noted, with ampelopsin decreasing in concentration over the growing season.

Although western riparian ecosystems comprise only a very small part of our rangelands, riparian issues have become increasingly controversial in the 1990's. This study of Nebraska sedge (Carex nebraskensis Dewey) and planeleaf willow (Salix planifolia Pursh.) was designed to determine the effects of intensity of defoliation and season of use on these two important riparian species. The study was conducted over 4 years in a montane riparian zone in northern Colorado at an elevation of 2500 m. During the first 3 years of study, Nebraska sedge and planeleaf willow were clipped once at light, moderate, or heavy intensities to remove approximately 30, 60, and 90% of current year's growth (CYG). Plants were defoliated at one of four phenological stages which corresponded to either spring, early summer, late summer, or fall. An unclipped control and a treatment representing season-long continuous use were also included. Nebraska sedge vigor, following 3 years of clipping, was estimated by sampling shoot density, shoot height, aboveground biomass, species composition, and belowground total nonstructural carbohydrates (TNC). Vigor of planeleaf willow was determined by estimating number of shoots, number of buds, leaf length, and aboveground TNC concentrations. Data suggest that fall and spring were the least harmful periods for defoliation of both species. Early summer treatments were most detrimental, and were not significantly different than the continuous use treatment. Defoliation at 90% CYG was significantly more detrimental than the remaining levels. By the fourth year of the study, 33% of the willows clipped at 90% during early summer had died.

Laboratory and field rainfall simulations were conducted to determine the influence of soil and vegetation characteristics on sediment yield from vegetated buffer strips. The laboratory experiment was used to compare the influence of three lengths of vegetation buffer strips and two vegetation heights on sediment filtration. The field experiments were used to evaluate the influence of two riparian communities, three vegetation heights, two plot sizes, and two particle size distributions on sediment filtration from overland flow. It was hypothesized that increased vegetation height alone was not sufficient to increase sediment filtration, but that several vegetation and soil surface characteristics were required to decrease sediment yield.

Rainfall (50 mm hr^-1) was simulated in the laboratory over six trays (0.6 m x 1.0 m). Concurrently, sediment laden overland flow was introduced to the up-slope end of the trays (50 mm hr^-1). Two trays contained 12.5 cm, two trays contained 25.0 cm, and two trays contained 50 cm of Kentucky bluegrass (Poa pratensis L.) buffer strips within each simulation run. Paired buffer length trays either were clopped to the soil surface or had 10 cm tall grass. Vegetation height did not significantly affect sediment yield, but the length of bluegrass buffers did affect sediment yield. The 50 cm buffer length filtered more sediment than either the 12.5 or 25 cm buffers.

Field rainfall simulations (60 mm hr^-2) were performed over two macro-plots (3 m x 10 m) and two micro-plots (0.6 m x 2 m) simultaneously. Overland flow (25 mm hr^-1) containing sediment (two particle size distributions) was introduced simultaneously to the up-slope end of the plots.

Sediment yield was not affected by vegetation height or vegetation community. The micro-plots yielded more sediment than the macro-plots. Coarse sediment (>200 m) traveled farther down-slope in the clipped to the soil surface treatment than in either the 10 cm or natural height vegetative treatments.

Study results indicated that vegetation height is not an important variable effecting sediment yield, but that height may be relevant on a small scale basis for coarse particle movement.

Riparian zones are subjected to the combined impacts of many activities. Because of this, management recommendations to achieve desired goals are difficult to prescribe. This research was conducted to determine the relationship between herbaceous utilization and diet preference in a montane riparian zone. The study site was the Sheep Creek Allotment in north-central Colorado. The Allotment is located within the Roosevelt National Forest at an elevation of approximately 2500 m. Species composition and biomass of the vegetation were determined using the double sampling technique. Utilization of the herbaceous vegetation was determined by measuring the residual stubble heights of plants along five randomly placed line transects. Standard growth curves were used to determine the height-to-weight ratios of the plant species found in the research area. The botanical composition of the steers' diets was determined with esophageally fistulated animals. Diet sample were taken at four phenological stages of the indigenous Salix spp. The grazing seasons were late-spring, early-summer, late-summer, and early-fall. Diet samples were taken each morning at 0, 25, 50, and 75% levels of utilization. Preliminary findings suggest that willow use increases as the grazing season progresses. In addition, willow consumption increased within a grazing season as high utilization levels reduced the availability of herbaceous vegetation. Differences in relative preference to willows were also observed among the individual steers. Information obtained from this research will improve our understanding of plant/animal interactions within riparian zones.

Cattle grazing in riparian zones has become increasingly controversial during the past decade. This study was designed to determine changes in seasonal diet preferences of cattle in a riparian zone. The study area was located in northern Colorado at an elevation of 2500 m. Vegetation and diet samples were taken during four phenological stages which corresponded to late-spring, early-summer, late-summer, and early-fall. Three paddocks were sampled during each phenological stage. Vegetation was sampled using a double sampling method to determine biomass by species on offer to cattle. Diet samples were obtained using six esophageally fistulated steers. A relative preference index was determined by individual species for each phenological stage. Cattle generally preferred Kentucky bluegrass (Poa pratensis) and water sedge (Carex aquatilis) during the late-spring and early-summer grazing periods. Consumption of willows (Salix spp.) by cattle increased throughout the growing season with the greatest use occurring during late-summer. Information obtained in this study should help managers develop grazing systems that allow for a desirable mix of herbaceous and woody vegetation in a riparian zone.

Ann R. Dernburg, Ph.D. Rangeland Ecosystem Science, 1997

The objective of this study was to determine cattle preferences among five species of willows -Salix planifolia, S. geyeriana, S. bebiana, S. lutea and exigua- in a mountain riparian site using a cafeteria trial. Five steers were penned individually in a riparian meadow at Sheep Creek, Colorado. Five branches of each species were placed in equidistant buckets in each pen. Consumption of each species was measured by weight. Branches were weighed at 0, 2, 12, 24, 48 hours. Trials were repeated in spring, early-summer, late-summer and fall of 1994 and 1995. In 1994, individual animal preferences were insignificant. However, there were seasonal differences in the consumption of willows, irrespective of species (p=0.0002). Furthermore, within seasons, willow species preference occurred (p=0.08). Over, S. lutea was most preferred, while S. exigua was least utilized. Not surprisingly, willow consumption varied significantly between weighing periods (p=0.007) and was generally greatest during the first two hours of the trial. Data from this study suggest that management of riparian sites should include considerations of willow species and seasonal preferences.

Proper grazing management of montane riparian zones has become a concern because of increased awareness of the importance of these areas for proper functioning of adjacent ecosystems. Soil physical properties that ensure rapid infiltration in the riparian zone are important to maintain the function of these systems. We investigated seasonal effects of grazing (early spring vs. late summer) on soil physical properties in a mountainous riparian zone. Assessment of the recovery of the soils after heavy seasonal grazing was conducted by measuring various soil physical properties such as bulk density, infiltration, porosity, moisture, texture and organic matter. Statistical models that used bulk density and cumulative infiltration as responses to treatments were significant (p<0.01), but low r² values indicated much unexplained variability. This was perhaps caused by inherent spatial and temporal variations in the environment or missing parameters. Multiple regression analysis indicated that the amount of clay present at a 5-cm soil depth had a strong influence on infiltration.

High intensity rainfall was simulated over upland range plots with varying amounts of grass, forb, and shrub cover. Variables measured included surface roughness, soil moisture, bulk density, and cover of individual species, litter, bare ground, and erosion pavement. Data for runoff, infiltration, and sediment yield were collected. Surface roughness, as influenced by vegetation type, was effective for reducing runoff and sediment yield. However, the location of the vegetation cover within a plot had little influence on runoff and sediment yield. Grassland vegetation had less sediment yield as compared with shrub or forb vegetation.

Forage nitrogen (N) and phosphorus (P) concentrations and in-vitro dry-matter digestibility (IVDMD) were measured in 2 important riparian species the year following short-term, high-intensity cattle grazing treatments in a montane riparian ecosystem. Nitrogen, P, and IVDMD were the response variables used to determine effects of grazing and season of grazing in 1995 on forage quality the following growing season. Current year's growth of water sedge (Carex aquatilus) and planeleaf willow (Salix planifolia) were collected monthly from May through September, 1996. Nitrogen and phosphorous concentrations and IVDMD declined over the course of the growing season for both species. Nitrogen, P, and IVDMD in water sedge were different from those found for planeleaf willow. Planeleaf willow N and P concentrations were 43% and 52% higher, respectively, than for water sedge when averaged over the growing season. Digestibility of water sedge was 25% higher than that for planeleaf willow.

Season of grazing (i.e., late-spring, early-summer, late-summer, and fall) the previous year did not affect forage quality in either species. Cattle use the previous year did, however, increase forage quality of water sedge as compared with plants that were not previously grazed. Grazed water sedge plants had higher concentrations of N and P and greater IVDMD than ungrazed controls.

Nitrogen and P concentrations of browsed planeleaf willow were not different from controls, but IVDMD in browsed willow plants was 12% greater than those that were not browsed. The 2 species responded uniquely to cattle use, and this suggests that these life-forms differ in response to herbivory. This study supported the hypothesis that previous cattle use can improve forage quality in a riparian ecosystem, although results varied with life-form.

Riparian areas are under increased scrutiny in the western states as advocates for water quality and wildlife point out the degraded state of many stream environments. A growing body of laws, policies, and regulations will require changes in rangeland grazing practices necessary to protect and enhance ecosystem diversity and water quality. It is recognized that streambanks have been altered by animal and human impacts, with direct consequences to water quality, wildlife habitat, and aquatic life. These alterations are distinct from changes related to fluvial geomorphology. Past research efforts have not conclusively shown how livestock use affects streambanks. The objectives of this study were to evaluate streambank morphological changes as affected by cattle trampling; to determine the importance of streambank soil physical properties, herbaceous plant cover, and root structure for streambank stability as affected by livestock use and trampling; and to relate trampling and soil and root physical properties to soil displacement as an index of streambank stability. Experimental plots were constructed at the Sheep Creek Research area in north-central Colorado. Steers were stocked at two levels of grazing intensity and changes to streambank morphology evaluated. Preliminary results indicated insignificant effects on streambanks from moderate and heavy one-time use by cattle. A follow-up study used a hoofprint simulator to relate trampling depressions to soil texture, organic matter, moisture content, aboveground vegetative composition, and belowground root characteristics. Results of this work are not yet analyzed.

Use of herbaceous stubble height criteria as a management tool in riparian areas has been variously recommended in recent years. The assumed benefits of maintaining minimum herbaceous stubble heights in the streamside zone of riparian areas included maintenance of forage plant vigor, sediment entrapment for streambank building, maintenance of sufficient biomass to reduce late-season cattle browsing of willows (Salix spp.), limitation of streambank trampling, and provision for an easily communicated management criterion. Follow-up studies and discussions with professional land managers have been used to evaluate these proposed benefits. Stubble height standards seemed to be particularly useful for maintaining plant vigor in mountain meadow sedge (Carex spp.) communities. Conversely, although some plant stubble is useful to create surface roughness, much of the sediment deposition is not dependent on plant stubble height. The primary sedimentation value of the plants appeared to be the stabilization of deposits after initial deposition. Recently completed studies illustrated the benefits of additional stubble height and forage biomass in reducing the cattle browsing impacts on streamside willow communities. The evidence for reduction of streambank trampling is somewhat circumstantial. Higher stubble heights generally mean that less grazing and less trampling has occurred and, therefore, less impact on streambank morphology has resulted. The correlation of stubble height with morphology, however, will vary by soil parent material. The ease of communication of stubble height criteria among livestock permittees and public land managers appears to be almost universally accepted. Overall, herbaceous stubble height criterial still appears to be an effective tool in proper management of streamside grazing in many situations.

The mountainous riparian corridor performs important hydrologic functions including nutrient transfers between the terrestrial (upslope) and aquatic (stream) ecosystems. Streamflow and soil water samples were collected from Sheep Creek and soil water samples collected from the riparian corridor and upslope systems to determine nitrate-nitrogen and ammonium-nitrogen concentrations under both losing and gaining streamflow conditions. Three sampling traverses from the stream through the riparian corridor, into the upslope ecosystem were sampled in 1993 and 1994 with a variable sampling frequency.

Statistical comparisons were made spatially and temporally between: 1) the upslope ecosystem and the riparian corridor, 2) the upslope ecosystem and the stream, and 3) the riparian corridor and the stream. Water quality differences were evaluated over two distinct streamflow periods during snowmelt (gaining system) and reservoir release (losing system).

The Sheep Creek riparian corridor serves as a sink for nitrate-nitrogen in both gaining and losing streamflow conditions, while the riparian serves as a source for ammonium nitrogen in gaining streamflow conditions. Riparian characteristics, coupled with streamflow generation mechanisms, determine if the riparian is a nutrient sink or source.

Riparian areas are extremely valuable ecological resources for the abundance of services they provide to both humans and herbaceous understory plant species, and is essential for many wildlife species. The objectives of this study were to 1) determine survival and growth rates of two species of willow cuttings planted in highly disturbed sites as compared with those planted in undisturbed control areas; and 2) compare the rates of recovery in vegetation cover and species diversity in areas heavily disturbed during different times of the growing season versus undisturbed control plots. Nine 4 x 5-m plots were trampled by 5 steers during the 1995 growing season in spring (June 11-13), summer (July 9-11), and fall (September 17-19). Cuttings of Salix planifolia and S. lutea were obtained from a nearby stand in May 1996. Ten of each species were planted in each of the 9 disturbed plots and in 3 undisturbed control plots. 1996 monitoring revealed Salix lutea cuttings had higher rates of survival and growth the S. planifolia. Willow cuttings planted on disturbed sites showed higher rates of establishment and growth than those in control plots. Visual estimates of percent cover by species were taken on each site (disturbed and control) during early growth and peak standing crop in 1996 and 1997. Results from 1996 show the trampled sites contain higher numbers of individual species (greater species diversity) than the undisturbed areas. The origins of the species (exotic/native) and their niches will be used to explore their desirability in this riparian ecosystem. During the 1997 growing season, ion-exchange resin bags have been buried in all plots to estimate relative rates of soil nitrogen mineralization. Mesh bags of Carex aquatilis and Salix planifolia litter were placed on each of the 12 plots to monitor differences in decomposition rates between the disturbed and undisturbed plots.

Riparian ecosystems are the final terrestrial zone before runoff water enters a stream. They provide the last opportunity to decrease non-point source pollution delivery to streams by removing sediments from overland water flow from uplands or roads. To quantify processes of sediment transport, filtration, and deposition, it is necessary to determine runoff characteristics. A rotating boom rainfall simulator was used to evaluate the effects of 3 vegetation height treatments in 2 montane riparian plant communities (grass and sedge) on runoff characteristics. Rainfall simulation events consisted of 2 phases, a dry run of about 60 minutes followed by a wet run approximately 30 minutes later. There were no differences in time to runoff initiation for either dry or wet runs that could be attributed to vegetation height treatments for either plant community. It usually required more time for runoff to be initiated in the sedge community compared to the grass community. Generally, there were lower equilibrium during wet runs. Several runoff parameters had characteristics of runoff from water repellent soils. The organic layer on the soil surface exhibited signs of water repellency that reduced the water infiltration rate during the initial stages of a rainfall simulation. These results indicate that runoff and infiltration processes in the surface organic horizon of riparian zones may not respond in the classical manner. This characteristic has important implications in managing overland flow in the riparian zone.

It was hypothesized that the type and height of riparian vegetation would affect its ability to filter and retain inorganic nitrogen [nitrate-nitrogen (NO₃^--N), ammonium-nitrogen (NH₄^--N)], and inorganic phosphorus [phosphate-phosphorus (PO₁^-3-P)]. A rotating boom rainfall simulator was used to evaluate 2 montane riparian communities as filters for removing NO₃^--N, NH₄^--N, and PO₁^-3-P nutrients from sediment laden overland flow water. One riparian community was characterized by Kentucky bluegrass (Poa pratensis L.) and tufted hairgrass (Deschampsia caespitosa (L.) Beauv.), while the second community was dominated by beaked sedge (Carex rostrata Stokes) and water sedge (Carex aquatilus Wahl.). Three vegetation height treatments were evaluated: control (natural condition), moderate treatment (clipped to 10-cm height and clipped material removed), and heavy treatment (clipped to ground level, clipped material removed, and litter vacuumed up). A 10-m wide riparian buffer zone was an efficient filter as about 84% NO₃^--N and 79% PO₄^-3-P was removed from the applied water and sediment. However, there were no consistent differences among specific vegetation height treatments or communities in the removal of N and P nutrients.

Short duration-high intensity cattle grazing and trampling in 3 x 10 m montane riparian buffer strips was evaluated for effects on runoff, infiltration, and sediment filtration under simulated rainfall (100 mm hr^-1) plus overland flow (25 mm hr^-1) conditions. Commensurate with equilibrium discharge, 60 kg of a fine silica sediment was introduced to the overland flow at the top of each plot by applying 3 kg of ground silica sediment every 2 min for 40 min. Four treatments were replicated 4 times in a randomized complete block design. The treatments consisted of: 1) undisturbed control, 2) mowed to 10 cm stubble height, 3) trampled by cattle, and 4) cattle grazed plus trampled (grazed). Trampling by cattle reduced soil surface spatial heterogeneity which was indicated by decreased drainage density and microchannel sinuosity. Herbaceous stem density was reduced by cattle grazing. Average stem density was 5300, 5500, 4700, and 3300 stems m^-2 for the control, mowed, trampled and grazed treatment, respectively. Regression analysis indicated that stem density was the most important variable for predictions of runoff and sediment filtration.

Infiltration capacity was decreased and accumulated runoff was increased by cattle grazing after 1 hour of simulated rainfall. Hydrograph analyses showed that short duration-high intensity cattle activity altered different components of the discharge hydrograph. Cattle grazing reduced time to runoff initiation and time to equilibrium runoff and extended the falling limb of the runoff hydrograph.

Results from this study indicated that a 10 m wide montane riparian buffer strip was an effective means for reducing sediment in overland flow. Control and mowed treatments retained 90% of the applied sediment, while short duration-high intensity cattle trampled and grazed treatments retained 84 and 77% of the applied sediment, respectively. Monitoring of stem density may aid in management decisions where riparian buffers are integrated into a system of Best Management Practices to protect surface water quality.

Water quality of runoff from grazed and ungrazed plots in a montane riparian ecosystem was assessed. A rainfall simulator was used to create runoff from these plots. Runoff rates, concentrations, and fluxes of all water quality parameters were much greater from heavily grazed plots as compared with ungrazed plots. The concentrations of nitrate-N and ammonia-N in runoff from grazed plots did not exceed the established EPA criteria of 10 mg/L and 5.1 mg/L (based on an average temperature of 5 C and pH of 7.5), respectively. The average concentration of fecal coliform in runoff from grazed and control plots exceeded the EPA standard of 1000 CFU/100mL for secondary water contact.

Fluxes from the grazed plots were significantly greater than fluxes from control plots for all contaminants. Nitrate-N, ammonia-N, phosphate-P, and fecal coliform fluxes from grazed plots were 180%, 1350%, 2100%, and 2400% greater, respectively, than fluxes from control plots. Heavy cattle grazing increased the concentrations of contaminants in runoff water and also increased runoff rates; both were responsible for the increased fluxes from grazed plots.

A single heavy grazing event increased runoff rates by 70% in a montane riparian ecosystem. Manure and urine deposited during heavy grazing significantly increased the concentrations of nitrate-N, ammonia-N, phosphate-P, and fecal coliform in runoff as compared with their concentrations in runoff from control plots and water from Sheep Creek. These increases in concentrations and runoff rates were responsible for increased fluxes of contaminants from the grazed riparian area. Heavy cattle use of riparian areas adjacent to streams could result in non-point source pollutants reaching the stream.

Riparian areas link streams with their terrestrial catchments and decrease pollution by trapping sediments from upland sources before they reach streams. Livestock grazing in riparian areas is a controversial practice, since if not properly managed, cattle can cause degradation to both the riparian zone and adjacent water body. To quantify the effects of cattle on flow dynamics and sediment movement, vegetative, soil microtopographical, and microchannel characteristics were measured in a montane riparian community in northern Colorado. Following 4 treatments (cattle trampling, cattle grazing plus trampling, mowing and control), water was applied to plots (3 m x 10 m) at a rate of 100 mm hr^-1. The amount of sediment collected in sediment traps at 5 distances downslope (1 m, 1.5 m, 2 m, 2.5 m, 3 m), both within and between channels, was evaluated. Microchannel sinuosity, slope, flow depths, and drainage density were also measured. Greater movement of sand (particles>200 m) downslope occurred for the grazed plus trampled treatment. Additionally, greater amounts of sediment were present in traps at 1 m in channels and 1.5 m between channels on grazed plus trampled plots. For each distance downslope, more sediment was collected in channels than between channels. Cattle treatments resulted in lower microchannel sinuosity and drainage density. Plots that were trampled or grazed by cattle showed greater channel slope and flow depths. Therefore, runoff in microchannels resulted in greater runoff and sediment movement on grazed plots.

Cattle use and presence of overstory canopy have been shown to affect diversity of understory plants in riparian areas. However, the degree to which these two factors interact and affect diversity of forbs and graminoids has not been explores in depth. Cover of understory species and growth of willow overstory canopy were determined between 1988 and 1998 adjacent to Sheep Creek, CO. Understory light penetration was measured in 1998. Light penetration was higher in areas of long-term grazing (LG) and recent exclosure (RE) than in long-term exclosures (LE) and recently grazed (RG) plots. Ten years after RE and RG plots were formed from LG and LE areas in 1988, the average number of species found in plots was similar for the LG and LE plots and the plots that were formed from them (LE = 13.1, RG= 13.0, and LG = 10.7, RE = 10.8). Data were used to create a model to predict the effect of different grazing levels and different amounts of willow overstory canopy coverage on species diversity for two sets of functional groups: forbs and graminoids, as well as native and exotic species. Information on how grazing history and overstory canopy cover affect understory plant diversity should be useful for resource managers in development of conservation plans in similar western riparian ecosystems.

Stuber, R.J. 1985. Trout habitat, abundance, and fishing opportunities in fenced vs. protected riparian habitat along Sheep Creek, Colorado, p. 310-314. In Riparian Ecosystems and Their Management: Reconciling Conflicting Uses. USDA Forest Service Gen. Tech. Rep. Rm-120.

Schulz, T.T. and W.C. Leininger. 1990. Differences in riparian vegetation structure between grazed areas and exclosures. J. Range Manage. 43:295-299.

Schulz, T.T. and W.C. Leininger. 1991. Nongame wildlife communities in grazed and ungrazed montane riparian sites. Great Basin Naturalist 51:286-292.

Benkobi, L., M.J. Trlica, and J.L. Smith. 1993. Soil loss as affected by different combinations of surface litter and rock. J. Environ. Qual. 22:657-661.

Benkobi, L. M.J. Trlica, and J.L. Smith. 1994. Evaluation of a refined surface cover subfactor for use in RUSLE. J. Range Manage. 47:74-78.

Popolizio, C.A., H. Goetz, and P. Chapman. 1994. Short-term response of riparian vegetation to 4 grazing treatments. J. Range Manage. 47:48-53.

Pearce, R.A., M.J. Trlica, W.C. Leininger, J.L. Smith, and G.W. Frasier. 1997. Efficiency of grass buffer strips and vegetation height on sediment filtration in laboratory rainfall simulations. J. Environ. Qual. 26:139-144.

Pearce, R.A., M.J. Trlica, W.C. Leininger, D.E. Mergen, and G.W. Frasier. 1998. Sediment movement through riparian vegetation under simulated rainfall and overland flow. J. Range Manage. 51:301-308.

Pearce, R.A., G.W. Frasier, M.J. Trlica, W.C. Leininger, J. Stednick, and J.L. Smith. 1998. Sediment filtration in a montane riparian zone under simulated rainfall. J. Range Manage. 51:309-314.

Pearce, R.A., G.W. Frasier, W.C. Leininger, and M.J. Trlica. 1998. Sediment movement and filtration in riparian vegetation. pp. 167-177. In D.F. Potts (ed.) Rangeland Management and Water Resources. Proc. AWRA Speciality Conf., 27-29 May 1998. Reno, Nev.

Arp, C.D., D.J. Cooper, and J.D. Stednick. 1999. The effects of acid rock drainage on Carex aquatilis leaf litter decomposition in Rocky Mountain fens. Wetlands 19:605-674.

Phillips, R.L., M.J. Trlica, W.C. Leininger, and W.P. Clary. 1999. Cattle use affects forage quality in a montane riparian ecosystem. J. Range Manage. 52:283-289.

Stednick, J.D. and A.G. Fernald. 1999. Nitrogen dynamics in stream and soil waters. J. Range Manage. 52:615-620.

Frasier, G.W., M.J. Trlica, W.C. Leininger, R.A. Pearce, and A. Fernald. 1999. Runoff from simulated rainfall in 2 montane riparian communities. J. Range Manage. 51:315-322.

Corley, C.J., G.W. Frasier, M.J. Trlica, F.M. Smith, and E.M. Taylor, Jr. 1999. Nitrogen and phosphorus in runoff from 2 montane riparian communities. J. Range Manage. 52:600-605.

Clary, W.P. and W.C. Leininger. 2000. Stubble height as a tool for management of riparian areas. J. Range Manage 53:562-573.

Trlica, M.J., E.A. Nibarger, W.C. Leininger, and G.W. Frasier. 2000. Runoff water quality from grazed and ungrazed montane riparian plots. pp. 263-268. In Proc. AWRA's 2000 Summer Speciality Conference Riparian Ecology and Management in Multi-Land Use Watersheds. August 28-31, Portland, OR.

Flenniken, M. R.R. McEldowney, W.C. Leininger, G.W. Frasier, and M.J. Trlica. 2001. Hydrologic responses of a montane riparian ecosystem following cattle use. J. Range Manage. 54:567-574.

Mergen, D.E., M.J. Trlica, J.L. Smith, and W.H. Blackburn. 2001. Stratification of variability in runoff and sediment yield based on vegetation characteristics. J. Amer. Water Resour. Assoc. 37:617-628.

McEldowney, R.R., M. Flenniken, G.W. Frasier, M.J. Trlica, and W.C. Leininger. 2002. Sediment movement and filtration in a riparian meadow following cattle use. J. Range Manage. 55:(in press).

Wheeler, M.A., M.J. Trlica, G.W. Frasier, and J.D. Reeder. 2002. Seasonal grazing affects soil physical properties of a montane riparian community. J. Range Manage. 55:(in press).
 

Return to CREAM home page

College of Natural Resources | Colorado State University
Disclaimer | Equal Opportunity | Apply to CSU

Forest, Rangeland, and Watershed Stewardship Department
College of Natural Resources
Colorado State University
Fort Collins, CO 80523-1472 USA
FRWSwebmaster