Research Summaries

Share
Lesica, P. and S. Miles.
2004. Ecological strategies for managing tamarisk on the C. M. Russell National Wildlife Refuge, Montana, USA. Biological Conservation 119:535-543.

Tamarisk (Tamarix ramosissima) is an introduced shrub or small tree associated with the loss of biological diversity in riparian habitat throughout much of western North America. Control measures are often expensive and ineffective, so land managers need site-specific information to guide cost-effective integrated management strategies. We sampled 12 randomly selected tamarisk-infested inlets on Fort Peck Reservoir on the C. M. Russell National Wildlife Refuge stratified by stream basin size. At each site, we sampled 2-3 stands of riparian vegetation, recording plot elevation, canopy cover of vascular plants, density of weedy species and age estimates for representative woody plants. Tamarisk plants 1-3 years old were abundant in the drawdown zone along the shore of Ft. Peck Reservoir. The lack of plants older than three years indicated that tamarisk in the drawdown zone were destroyed during two recent summers of inundation and suggests that three months of inundation will kill tamarisk plants. The oldest (17-22 years) and largest tamarisk plants in the study area were found in the full-pool zone and were recruited during periods of significant drawdown following high-water years. Tamarisk was uncommon in cottonwood and silver sagebrush stands on stream terraces above full pool. Only the largest streams in our study area appeared to be capable of supporting tamarisk and significant native riparian vegetation. Tamarisk plants at or above full pool level should be removed in these drainages to prevent upstream invasion and loss of native species. The level of the reservoir should be raised to the level of full pool for three consecutive months during the growing season every 3-5 years to prevent development of extensive stands of tamarisk in the drawdown zone capable of producing large quantities of seed.

Bernhardt, E. S. and 24 others.
2005. Synthesizing US river restoration efforts. Science 308:636-637.

Despite the increasing popularity of stream restoration projects, there has been little systematic study of them to determine implementation and outcomes. To do so, the authors studied 37,099 stream restoration projects in the US in the National River Restoration Science Synthesis database. For the purposes of the study, “restoration” was defined broadly. The number of restoration project increased exponentially during the last decade. Project were not distributed uniformly across the country; rather, 88% of the projects studied were located in the Chesapeake Bay, Pacific Northwest or in California. Median projects were small, less than $45,000, although only 58% of the projects in the database had cost information. Only 10% of the projects had any form of assessment or monitoring, yet even most of these were not designed to evaluate the consequences of restoration activities of to disseminate monitoring results. Thus, opportunities to learn from successes and failures are largely being lost.

Rood, S. B., G. M. Samuelson, J. H. Braatne, C. R. Gourley, F. M.R. Hughes, and J. B. Mahoney.
2005. Frontiers in Ecology and the Environment 3:193-201.

River damming has dramatic environmental impacts, and while changes due to reservoir flooding are immediate, downstream impacts are more spatially extensive. Downstream environments are influenced by the pattern of flow regulation, which also provides an opportunity for mitigation. We discuss impacts downstream from dams and recent case studies where collaborative efforts with dam operators have led to the recovery of more natural flow regimes. These restoration programs, in Nevada, USA, and Alberta, Canada, focused on the recovery of flow patterns during high flow years, because these are critical for riparian vegetation and sufficient water is available for both economic commitments and environmental needs. The restoration flows were developed using the “Recruitment Box Model”, which recommends high spring flows and then gradual flow decline for seedling survival. These flow regimes enabled extensive recruitment of cottonwoods and willows along previously impoverished reaches, and resulted in improvements to river and floodplain environments. Such restoration successes demonstrate how instream flow management can act as a broadly applicable tool for the restoration of floodplain forests.

Martin, L. T., S. R. Pezeshki, and F. D. Shields, Jr. 2006.
Soaking treatment increases survival of black willow posts in a large-scale field study. Ecological Restoration 23: 95-98.

This study occurred along Topashaw Creek in Mississippi. Black willow posts were cut, then soaked in stream water for 14 days. The unsoaked posts were cut the day before planting to minimize water loss. The willows posts were planted in dispersed silt and clay soils overlying sands. At the end of the first growing season, soaked posts had greater survival that unsoaked posts, but only at high elevations (> 100 cm above the creek level). Rainfall during the first growing season was well below the 30-year average.

Unterschultz, J. R., J. Miller, and P. C. Boxall.
2004. The on-ranch economics of riparian zone cattle grazing management. Environmental Management 33:664-676.

A simulation model of a cattle ranch based in southern Alberta, Canada was developed to evaluate the on-ranch economics of adopting different grazing management strategies to improve riparian grazing capacity in natural grass rangeland. Under low-cost scenarios, there are positive economic incentives to adopt strategies to maintain riparian zones that already have high grazing capacity. However, riparian zones that have declined to moderate or low grazing capacity may require additional economic incentives to encourage ranches to adopt more costly management strategies to improve the grazing capacity. The economic incentives to adopt costly management strategies are highly sensitive to the size and shape of the riparian zone and rates of grazing capacity decline or improvement.

Annen, C. A., R. W. Tyler, and E. M. Kirsch.
2005. Effects of a selective herbicide, sethoxydim, on reed canarygrass. Ecological Restoration 23:99-102.

Reed canarygrass is an aggressive perennial grass that threatens wetland and riparian areas, because it can form dense, monotypic stands. Efforts to control this invasive plant have generally met with marginal to moderate short-term success. Sethoxydim (tradename Vantage) is a post-emergent, systemic herbicide that kills annual and perennial grasses. It has been used to control invasive grasses such as quackgrass and crabgrass. Sethoxydim was applied once to a stand of predominately reed canarygrass in central Wisconsin either early or late in the growing season and applied late in the season in concert with mowing. Sethoxydim reduced reed canarygrass biomass during the year of application but by the second year biomass was similar in all treatments. However, the herbicide reduced inflorescence density of reed canarygrass by 95% during the year of treatment. This is encouraging because uncontrolled reed canarygrass can produce large quantities of seed that may create a large soil seed reserve, and presumably retarding effects to permanently reduce reed canarygrass abundance. In addition, the herbicide did not reduce the biomass of non-target herbaceous plant species. Thus, sethoxydim showed some promise for controlling reed canarygrass.

Karaus, U., A. Laurenz, and K. Tockner.
2005. “Concave islands”: habitat heterogeneity of parafluvial ponds in a gravel-bed river. Wetlands v25, n1:26-37.

Floodplain pond distribution, density, and diversity were investigated along the active river corridor of the Tagliamento River in northeastern Italy, the last major semi-natural river in Central Europe. Along the corridor, ponds peaked in bar- and island-braided floodplains but were absent in constrained sections. Within the main study area, a 1.0-km2 large braided floodplain, the number of ponds containing water ranged between 18 and 39 depending on the water level in the main channel. Thermal properties and water-level fluctuations were the most important variables determining pond characteristics and heterogeneity. Results from a PCA on environmental variables distinguished four groups of ponds distributed along a hydrologic and thermal gradient. Parafluvial ponds are short-lived, discrete, aquatic “islands” within the floodplain matrix. They are expected to contribute disproportionately to aquatic biodiversity; however, they are very sensitive landscape elements that disappear as a consequence of river regulation, wood removal, and flow control.