Treatments used to stabilize and revegetate disturbed sites should be monitored and analyzed regularly to determine whether design objectives were met, to evaluate success of design treatments and their implementation over time, and to meet performance criteria established by permitting agencies and owners.
Typical National Pollutant Discharge Elimination System permits require that 70% of predisturbance vegetative cover be established before the notice of termination for the project is issued. If baseline or predisturbance data is not available, a reference area that is representative of the desired plant community can be used instead.
Monitoring methodology must be identified in the project’s initial planning stages to ensure that adequate resources are allocated for implementation. A number of different methodologies can be used, depending on the nature of the project, the project objectives and financial resources.
Qualitative sampling. This type of sampling includes photo points, aerial photos, cover estimates, a species list and information about the general community condition. Plant vigor can be described and rated on a scale of one to five. Indicators of vitality (reproduction) are observed, including successful seed production as well as vegetative means of reproduction.
Qualitative observations may be particularly useful for steep slopes where quantitative measurements can result in damage to vegetation and increased erosion. Unfortunately, many projects simply do not have the resources for qualitative sampling or owners are not interested in subjective, ecological observations.
Quantitative sampling. This method includes measurements and collection of hard data regarding vegetation cover (foliar or canopy); frequency (how often a species is encountered in a given sampling area); density (number of plants in a sampling area); diversity (number of species per sampling area); and survival (containerized plants). Seedling density can be a useful measurement, especially for first-year results in arid and semi-arid climates where vegetation is slow to establish.
Line intercept and point intercept. These are common, repeatable and objective sampling methods of intense quantitative monitoring. The point intercept method, a personal preference, measures absolute and species-specific cover by vegetation and other forms of cover, such as rock and mulch. A helpful instrument used to sample cover is the cover-point laser device developed by Synergy Research Solutions. An ocular device, also known as a sighting tube, also can be used.
The data recorded using the point intercept method includes type of cover (vegetative, nonvegetative or none) and the species that are intercepted by the beam, or “dot,” projected by the laser device. All plants intercepted by the beam along permanent transects are identified to the lowest possible taxonomic level. (Typically 100 “hits” are obtained per transect to simplify the arithmetic.) Analysis of cover can be broken into forms of vegetation—native and nonnative, perennial and annual, etc.—so that a better notion of community structure is achieved.
The analysis needs to provide the project owner with information that will determine whether performance criteria have been met. A minimum report may include photo points as well as a written summary of observations.
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