Research Summaries

Share
Benda, L., et al.
2004. The networks dynamics hypothesis: how channel networks structure riverine habitats. BioScience 54:413-427.

Hierarchical and branching river networks interact with dynamic watershed disturbances such as fires, storms, and floods to impose a spatial and temporal organization on the nonuniform distribution of riverine habitats, with consequences for biological diversity and production. Abrupt changes in water and sediment distribution occur at channel confluences in river networks and trigger changes in channel floodplain morphology. This observation, when taken in the context of a river network as a population of channels and their confluents, allows the development of testable predictions about how basin size, basin shape, drainage density, and network geometry interact to regulate the spatial distribution of physical diversity in channel and riparian attributes throughout a river basin. The spatial structures of river networks also regulates how stochastic watershed disturbances influence the morphology and ages of fluvial features found at confluences.

Clary, W. P. and J. W. Kinney.
2002. Streambank and vegetation response to simulated cattle grazing. Wetlands 22:139-148.

Simulated grazing techniques were used to investigate livestock impacts on structural and vegetation characteristics of streambanks in central Idaho, USA. The treatments, continued over two years, consisted of no grazing, simulated moderate early summer grazing, simulated moderate mid-summer grazing, and simulated heavy season-long grazing. The moderate treatments depressed the streambank surface about 3 cm while the heavy season-long treatment resulted in an 11.5-cm depression. There were no differences between the no-grazing and moderate-grazing treatments for change in stream width, bank angle, bank retreat, or root biomass. The heavy season-long treatment, however, produced significant changes in these variables. The amount of foliage biomass removed by treatment was similar between the two years of the study for the moderate treatments. The foliage removed from the heavy season-long treatments plots greatly decreased in the second year as plant growth decreased. Ten months after the last treatment application, the average spring foliage growth was 20-43% lower on the moderate treatment plots and 51-87% lower on the heavy season-long treatment plots that on the untreated control plots.

Hyatt, T. L., T. Z. Waldo, and T. J. Beechie.
2004. A watershed scale assessment of riparian forests, with implications for restoration. Restoration Ecology 12:175-183.

A combination of air-photo interpretation, field data, and geographic information system (GIS) analysis was used to map riparian areas that are likely to provide wood and shade to small- and medium-sized streams and where, conversely, restoration might be most beneficial. The analysis encompassed all salmonid-bearing waters of the Nooksack River basin, in northwestern Washington State, plus small tributaries that were thought to contribute wood or effective shading. The size and composition of each riparian stand was examined to determine whether trees were large enough to contribute logs that would form ponds in the adjacent channel, with pool-forming size of wood a function of channel width. Riparian stands were classified according to whether that passed this pool-forming test. Model results were an exact match to actual conditions in 69% of field-verified stands. A large proportion (74%) of the stands failing the test in reaches of anadromous fish were in agricultural areas. Passing stands typically had high shade levels, because both stream shade and effective large woody debris are a function of the size of the trees relative to the size of the stream. The GIS layer of passing and failing riparian stands can be combined with layers depicting property ownership, threatened fish distribution, and other information to objectively prioritize riparian restoration locations and strategies.

Gage, E. A. and D. J. Cooper.
2004. Controls on willow cutting survival in a montane riparian area. Journal of Range Management 57:597-600.

To provide information to guide restoration of montane willow communities, we investigated factors influencing the survival of prerooted and unrooted mountain willow (Salix monticola) cuttings in 2 degraded montane riparian areas in Rocky Mountain National Park Colorado. We planted cuttings across a gradient of water table depths and soil textures and evaluated their survival using logistic regression analysis. We found that few cuttings (7.8% rooted and 3.9% unrooted) survived where summer water table depths exceeded approximately 90 cm. Soil texture was not a significant factor in our logistic models, potentially because of low silt and clay fractions in our plots. Rooted cuttings survived at a higher rate that unrooted cuttings after 1 (55.8% vs. 36.5%) and 2 (44.5% and 26.1%) years of growth. We conclude that when combined with appropriate hydrologic data, the use of rooted cuttings represents an effective technique to restore and revegetate degraded montane riparian ecosystems.

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 PACFISH-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 and others, in preparation).