Gary Frasier

Sediment movement through riparian vegetation under simulated rainfall and overland flow.

A 2-year rainfall simulation study was conducted to evaluate the effectiveness of riparian vegetation to reduce sediment movement. Three vegetation height treatments [clipped to the soil surface, 10 cm height, and undisturbed (unclipped)] were evaluated in 2 montane riparian vegetation communities in northern Colorado. One community was a tufted hairgrass (Deschampsia caespitosa (L.) Beauv.), cinquefoil (Potentilla gracilis Dougl. ex Hook), Kentucky bluegrass (Poa pratensis L.), and sedge (Carex spp.) association. The other community was dominated by beaked sedge (Carex rostrata Stokes) and water sedge (Carex aquatilis Wahl.). Water was sprayed on plots (3 m X 10 cm) at a rate of 60 mm hour-1 with a rainfall simulator, while overland flow containing sediment was introduced at the upper end of the plots at a rate of 25 mm hour-1. Two sediment sources were evaluated. In the first years studies the sediment was derived from an upland soil. The second year a fine silica sediment was used. Thirty kg of sediment was added to each plot. The first of 2 experiments was concerned with movement of sand particles greater than 200 micrometers. The second experiment was designed to evaluate the quantity of 5 particle size classes (2-10, 10-30, 30-50, 50-100, and 100-200 micrometers) contained in sediment traps at 60, 120, and 180 cm downslope from the upslope border of the simulator plots. Results of the first experiment showed a significant increase in sand movement downslope when vegetation was clipped to the soil surface compared with undisturbed vegetation. In the second experiment, most significant differences in movement for finer particles occurred in the 2-10 micrometers and 10-30 micrometers particle ranges. A smaller percentage of particles in the 2-10 micrometers range was present in sediment traps at all 3 distances downslope when vegetation was clipped to the soil surface, as these smaller particles stayed in suspension. Increased vegetation height resulted in a significantly smaller percentage of the 10-30 micrometers particle size range present at 120 cm distance. This study showed that additional variables (% surface vegetation cover, aboveground biomass, % shrubs, surface roughness coefficient, soil texture of introduced sediment, % bare ground, distance downslope, vegetation density, grass spp., and sedge spp.), besides vegetation height, influenced sediment movement. Land managers should understand that when they manage ecosystems for a single factor, such as vegetation height, they cannot address complex issues such as sediment particle detachment, movement and filtration.

Sediment filtration in a montane riparian zone under simulated rainfall

A 2 year study was conducted to evaluate the effectiveness of riparian vegetation to filter sediment from overland water flow. Three vegetation height treatments: clipped to the soil surface, clipped to a 10 cm height, and undisturbed were evaluated in 2 montane riparian vegetation communities (grass and sedge) in northern Colorado. Water was sprayed on 2 macro-plots (3 m X 10 m) and 2 micro-plots (0.6 m X 2 m) simultaneously at a rate of 60 mm hr-1 with a rotating boom rainfall simulator. Overland flow containing sediment was introduced at the upper end of the plots at a rate of 25 mm hr-1 to simulate runoff and sediment transport from an upland area. Two sediment sources were used, a sandy loam soil and a ground silica sediment (loam). Thirty kg of sediment were added to each macro-plot and 1.2 kg of sediment were introduced to each micro-plot (10 Mg ha-1). Sediment yields, at the downslope end of the plot, were greater when the finer silica sediment was introduced into overland flow as compared with sediment derived from the sandy loam soil. As expected the small micro-plots yielded more sediment and were often more sensitive to community and treatment differences than larger plots. We believe this resulted from the shorter travel distance. However, sediment filtration treatment effects were usually similar for both plot sizes. Sediment yields, measured at the outlet of the plots, did not decrease, or increase, as vegetation heights increased. Accurate prediction of sediment filtration from shallow flow in riparian zones required consideration of a combination of vegetation and soil surface characteristics.

Bare Ground and Litter as Estimators of Runoff on Short- and Mixed-Grass Prairie

After 56 years of grazing on shortgrass prairie and 13 years of grazing on mixed-grass prairie, surface runoff was estimated with a rotating boom rainfall simulator. Runoff was strongly and positively correlated with percent bare ground, and was strongly and negatively correlated with percent litter cover. Neither foliar nor basal plant cover were useful estimators of runoff.

Hydrologic responses of shortgrass prairie ecosystems.

Runoff hydrographs from 3 separate rainfall simulation runs at 11 different shortgrass prairie sites were evaluated to determine the hydrologic similarity within a single ecosystem at widely separated sites. There were no consistent patterns in the equilibrium runoff among sites and simulator runs. When the sites were stratified by soil type, there were differences in time-to-peak of the runoff event and the regression slope of the rising limb of the runoff ratios. Spearmans rank correlation showed no relation of the rising limb slope regression coefficient to measured vegetative characteristics across all sites. There was minimal correlation between the runoff regression coefficient and the percent cover and bare soil. Differences in the biotic components of the sites were not useful in predicting runoff characteristics. If equilibrium runoff was the measured hydrologic response, the sites were dissimilar. Using the time-to-peak and slope of the rising limb components of the runoff hydrograph, the sites were similar on the same soil type. The technique of comparing components of the runoff hydrograph, other than equilibrium runoff has promise to allow one to quickly compare responses among ecosystems to determine if they have similar hydrological functions. Our study on shortgrass prairie sites indicated that easily estimated factors such as biomass, cover and litter were not good indicators of hydrologic function. Also, it is necessary to identify which portion of the runoff event is most important in the assessment. Future hydrologic and erosion models need to develop nonlinear prediction equations to estimate infiltration rates as a function of cover, biomass, and soil properties and also to stratify soils into functional units to accurately estimate runoff rates. DOI:10.2458/azu_jrm_v53i4_weltz

Readers of Rangelands Survey Results

n May and June 2006, a survey (see sidebar table) was sent to the Society for Range Management readers of Rangelands to gain an assessment of how Rangelands was being perceived. The survey was conducted by the Rangelands publishing service, Alliance Communications Group, Allen Press Inc. Over 3,000 surveys were sent via e-mail and 500 copies via Member Resource News. A total of 847 responses were returned through the online version of the survey and 24 paper copies for an overall 26% response rate.

Water Management in Northwestern Egypt

April 2005 V isualize an area of 50 km by 400 km (30 × 120 miles) supporting an agricultural community of 40,000 people. Farmers raise sheep and goats, and better soil areas are planted to trees (figs and olive; Photo 1). Now, impose a climate of a desert regime with 100–200 mm (4–8 inches) of precipitation a year, mostly arriving during the winter months (November–March). This is the area along the Mediterranean coast of northwestern Egypt, from west of Alexandria to the Libyan border and extending inland for 50–70 km (30–40 miles).

Case Study: Long-Term Livestock Grazing Influence on Vegetation Class in Coyote Flat, California, USA

On the Ground Parker Three-Step data that exist on many US Forest Service allotments may be the only remaining, truly long-term vegetation and soil data available. Although Parker Three-Step procedures have been abandoned on many Forest Service districts, the historical insight they provide may be worth revisiting for management purposes. The Parker photos that accompany the transect data may be of more value than the data. Long-term vegetation records in Coyote Flat reveal the range to remain generally in fair condition since at least 1931, despite large reductions in livestock numbers, drastically shortened season of use, and 7 years of rest out of the last 13 grazing seasons. The correlation and interaction between reduced grazing pressure and ecological condition on high-elevation mountain meadow ecosystems, particularly as revealed by Parker Three-Step data, is not always intuitive or linear.

Working Landscapes—Providing for the Future

Working Landscapes—Providing for the Future: Annual Meeting of the Society for Range Management and the Weed Science Society of America DOI:10.2458/azu_rangelands_v31i4_farsier

Working Landscapes: Providing for the FutureWorking Landscapes—Providing for the Future: Annual Meeting of the Society for Range Management and the Weed Science Society of America

Working Landscapes—Providing for the Future: Annual Meeting of the Society for Range Management and the Weed Science Society of America DOI:10.2458/azu_rangelands_v31i4_farsier

Water Harvesting from Low-Standard Rural Roads

Book Review: Water Harvesting from Low-Standard Rural Roads, Bill Zeedyk. The Quivira Coalition, Zeedyk Ecological Consulting, LLC, the Rio Puerco Management Committee—Watershed Initiative, and the New Mexico Environment Department—Surface Water Quality Bureau (2006).