Riparian Ecosystem Creation and Restoration:
A Literature Summary
Monitoring
Many techniques used to document and monitor riparian habitats are untested, and some were designed to optimize time rather than accuracy (Platts et al. 1987a). The value of information obtained from monitoring riparian ecosystem creation/restoration projects depends on the precision, accuracy, and comprehensiveness of the data used for interpretation and decision making. Because past measurements can seldom be verified for quality, data must be collected with tested methods using a valid sampling design, followed by proper analysis and interpretation.
Platts et al. (1987a) present a comprehensive review of methods used to evaluate various components of riparian ecosystems. Guidelines useful for monitoring riparian ecosystem creation/restoration efforts are included in sections concerning sampling schemes, measuring vegetation, classifying riparian communities, determining various features of the soil, remote sensing, water column measurements, streambank morphology, measuring and mapping organic debris, and use of benthic macroinvertebrates to evaluate stream riparian conditions.
Determination of parameters to be monitored should be based on project goals and objectives (Platte et al. 1987b) and may include both independent (i.e., habitat) and dependent (i.e., population) parameters. Examples of independent parameters include frequency and duration of flooding; groundwater dynamics; channel morphology; streambank stability; streamflow characteristics; water quality; vegetative composition, cover, and production; and stream shading. Dependent parameters may include density and diversity of fish and wildlife populations. Frequency of monitoring is based on project goals and deadlines. Monitoring can be conducted frequently in the beginning and less frequently after rates of trends are determined. By far, the most common monitoring method has been to evaluate plant growth and survival over time. Monitoring plant species distribution below the level of community dominants provides superior benchmark information as well as a more sensitive scale to detect changes in water level, substrate type, and nutrient status (Chapman et al. 1982). If productivity studies are combined with detailed floristic measurements, results will yield far more sensitive and useful information regarding both the structure and function of the ecosystem than simple observations of dominant species distribution or survival.
Hydrologic responses should be monitored when riparian ecosystems are manipulated; however, this is usually left out of most research efforts (Skinner et al. 1985). Riparian ecosystem research should include determining: (1) water storage differences between degraded, natural, and improved habitats; (2) various water storage capabilities among different stream reaches; (3) improved riparian zone changes in flow regime, and possible prolonged release of water for downstream users; (4) hydrologic responses associated with each riparian zone improvement practice; (5) mechanisms of any possible reduction in nonpoint source pollution downstream as a result of riparian zone improvement practices; (6) hydrologic responses associated with grazing of improved riparian zones by livestock and wildlife; and (7) economic costs and benefits of improved riparian zones.
Monitoring methods need to be kept constant throughout data gathering (Anderson and Ohmart 1979). Pioneer efforts should be monitored until desired objectives have been achieved. Anderson and Ohmart (1979) recommended monitoring desert riparian systems in the lower Colorado River valley for at least 7 years to fully document establishment of plant communities. Anderson et al. (1979) stressed that long-term monitoring is especially necessary when restoration involves initial clearing of woody vegetation (e.g., to remove exotic vegetation) because habitat components are being removed. In addition, survival of riparian trees (e.g., cottonwoods) may change due to wind damage or disease before reaching maturity, which needs to be documented. Haynes and Moore (1988) reviewed efforts to reestablish bottomland hardwoods on 12 National Wildlife Refuges in the Southeast and found that even after 7 years desired plant species diversity had not yet been achieved on planted sites where natural regenerative processes were relied on to establish herbaceous understory plants.
Matter and Mannan (1988) stressed more frequent monitoring of creation/ restoration efforts over the first 1-2 years after habitat construction so that unsuccessful manipulations (e.g., failed plantings) can be replaced or revised as necessary. Periodic (every 3-5 years) monitoring of selected conditions (e.g., amount and types of major plant and animal species) should be conducted to ensure that habitat, once established, is not lost.
A monitoring study also needs to be of adequate duration to determine how climate affects the ways in which wildlife reacts to vegetative structure (Anderson and Ohmart 1979). Only then can a realistic evaluation of the impact or a prediction of the outcome of manipulation designed for enhancement be made. Anderson and Ohmart (1979) recommended that population data be collected for all major groups of animals (birds, mammals, reptiles, and amphibians) on a monthly or seasonal basis. Birds were found to be extremely responsive to habitat changes on the lower Colorado River and were used as the primary test group for Anderson and Ohmart's (1979) study.
Many avian population studies reported in the literature involve only the breeding season; however, this may not be the most critical season. Anderson and Ohmart (1979) found that bird populations reacted to structure (e.g., patchiness, vertical diversity, responses to particular plant species) less in summer than in other seasons. Populations in various plant communities tended to be more similar in summer than winter.
To determine effects of stream modifications (including improving riparian zones to provide cover for fish), Cooper and Wesche (1976) recommended monitoring trout populations for at least 5 years after stream restoration to follow 1 year-class through a life cycle.
Riparian ecosystem creation/restoration projects are often in impacted areas. Maintenance of ecosystem quality of the site requires three basic components related to monitoring: (1) a baseline biological-chemical-physical study of present conditions, (2) hazard evaluation based on knowledge of known potential pollutants entering the system and the estimated biological response to pollutants, and (3) a systematic and regular surveillance system designed to give early warning of impending harm (Cairns et al. 1979).
Proper monitoring of a created or restored riparian site over a long period of time and thorough analysis of the vegetation, animals, hydrologic regime, water quality, sediment deposition, and recreational use of this habitat will provide much-needed information for future creation/restoration efforts.
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