Research Summaries

Wohl, E. 2005.
Compromised rivers: understanding historical human impacts on rivers in the context of restoration. Ecology and Society 10: (on-line)

A river that preserves a simplified and attractive form may nevertheless have lost function. Loss of function in these rivers can occur because hydrologic and geomorphic processes no longer create and maintain the habitat and natural disturbance regimes necessary for ecosystem integrity. Recognition of compromised river function is particularly important in the context of river restoration, in which the public perception of a river’s condition often drives the decision to undertake restoration as well as the decision about what type of restoration should be attempted. Determining the degree to which a river has been altered from its reference condition requires a knowledge of historical land use and the associated effects on rivers. Rivers of the Front Range of the Colorado Rocky Mountains in the United States are used to illustrate how historical land uses such as beaver trapping, placer mining, tie drives, flow regulation, and the construction of transportation corridors continue to affect contemporary river characteristics. Ignorance of regional land use and river history can lead to restoration that sets unrealistic goals because it is based on incorrect assumptions about a river’s reference condition or about the influence of persistent land-use effects.

Blank, R. R., T. Svejcar, and G. Riegel.
2006. Soil attributes in a Sierra Nevada riparian meadow as influenced by grazing. Rangeland Ecology and Management 59:321-329.

Data on the effects of livestock grazing on soil nutrient availability are virtually nonexistent for meadow systems. We measured the effect of livestock grazing on soil, emphasizing soil-solution chemistry, in a Sierra Nevada riparian meadow. Treatments were livestock exclusion (begun in 1989) and grazing to leave 1?000 kg&#middot;ha-1 of vegetation. Ceramic tension lysimeters were placed in the treatments (2 replicates) by landscape position (stream edge, midfloodplain, and forest edge), and by depth (approximately 0.1, 0.6, and 1.2 m below the soil surface). Lysimeter water was extracted twice monthly in April, May, and June of 1990 through 1993, and cations and anions were quantified. In addition, KCl-extractable NO3- and NH4+; bicarbonate-extractable ortho-P; available Mn, Cu, Fe, and Zn; and root-length density (RLD) were quantified in soils by treatment, landscape position, and soil depth in July 1991 and September 1993. RLD was not affected by grazing. Significant (P?=?0.05) treatment effects were largely limited to the forest edge. The grazed treatment had greater lysimeter-extractable Na+, Ca+2, Mg+2, and NO3-; higher pH; and less K+ and NH4+ than the excluded treatment. Compared with corresponding excluded treatments, bicarbonate-extractable P was significantly greater on the grazed forest edge, and available Mn was significantly greater at the grazed stream-edge position in 1991. Extractable NO3- was significantly higher in the 0-25 cm depth increment of the grazed treatment, and available Zn was significantly greater on the grazed mid-floodplain position in 1993. Grazing did not result in more anoxic soil conditions than the excluded treatment. Grazing effects were most pronounced at the forest edge, possibly as a result of spatial transfer of nutrients via cow urine and feces. Management goals to sustain high-elevation meadows should emphasize maintenance of high RLD to sequester soil nutrients.

Anderson, K. E., A. J. Paul, E. McCauley, L. J. Jackson, J. R. Post, and R. M. Nisbet.
2006. Instream flow needs in streams and rivers: the importance of understanding ecological dynamics. Frontiers in Ecology and the Environment 6:309-318.

Resource managers have traditionally had to rely on simple hydrological and habitat-association methods to predict how changes in river flow regimes will affect the viability of instream populations and communities. Yet these systems are characterized by dynamic feedbacks among system components, a high degree of spatial and temporal variability, and connectivity between habitats, none of which can be adequately captured in the commonly employed management methods. We argue that process-oriented ecological models, which consider dynamics across scales and levels of biological organization, are better suited to guide flow regime management. We review how ecological dynamics in streams and rivers are shaped by a combination of the flow regime and internal feedbacks, and proceed to describe ecological modeling tools that have the potential to characterize such dynamics. We conclude with a suggested research agenda to facilitate the inclusion of ecological dynamics into instream flow needs assessments.

Robertson, M. 2006.
Emerging ecosystem service markets: trends in a decade of entrepreneurial wetland banking. Frontiers in Ecology and the Environment 6:297-302.

Markets in ecosystem services are now commonly considered by policy makers to be effective ways of achieving the goals of federal environmental protection laws. However, little empirical data currently informs policy development around such markets. Can a market-like arrangement solve the problems of compensatory wetland replacement under the Clean Water Act? This research examines the dynamics of the Chicago, Illinois market in wetland credits over a 9-year period, and shows that, although successful in many ways, it is prone to regulatory turbulence and may not fully address losses of wetland function. Market-based approaches to environmental policy problems will proliferate as more policy makers become convinced of the power of markets to achieve effective environmental conservation. Due to the new challenges of standardized commodity measurement that are present in these markets, environmental scientists are likely to be increasingly drawn into policy development and evaluation. This article is intended to alert ecosystem scientists and the environmental policy community to issues involved in evaluating the success of ecosystem service markets in achieving environmental policy goals.