1. Review of existing information
Within each survey region (county or ECS subsection), site and native plant community surveys begin with a review of existing records and information about areas of native vegetation. Among the sources consulted are:
- satellite imagery and aerial photos
- existing records in the Natural Heritage Information System
- climate, geologic, topographic, hydrologic, and soils data
- ecological classification system maps
- museum and herbarium records
- historical records, such as bearing tree data (184kb) and other information from the public land surveys conducted in Minnesota from 1847 to 1907
- records of natural disturbance events (for example, wildfires and windstorms)
- other research, monitoring, and inventory data, including timber stand inventories, the National Wetlands Inventory, forest songbird surveys, amphibian surveys, lake surveys, and vegetation monitoring data.
- local experts and other knowledgeable individuals
2. Site selection
Sites that appear to be have important areas of native vegetation or habitat are delineated on topographic maps and digitized in a geographic information system (GIS), using aerial photography, satellite imagery, and other related resource maps and data to determine boundaries. These sources also provide preliminary information about the types of native plant communities present within each site.
- If a site appears to contain several different kinds of native plant communities (for example, oak forests, sedge meadows, and tamarack swamps), the preliminary boundaries of each community type are delineated within the site.
- MBS has developed guidelines for determining which sites to select for survey within each county or ecological unit. These guidelines consider size, current condition (including type and extent of human disturbance), landscape context, spatial distribution of native plant communities, aquatic systems, and availability of critical rare plant or rare animal habitat.
- Each site is assigned a priority for survey of high, moderate, or low, based on its apparent condition. These survey priorities provide guidance for the amount of time to devote to a given site relative to others in the survey region.
3. Field surveys
Plant ecologists conduct field surveys of sites identified through the survey selection process, recording notes about the type and structure of vegetation present, common and "indicator" plants, and evidence of disturbance, such as cut stumps, soil erosion, and presence of non-native invasive plant species.
- Plant Ecologists often record a vegetation plot sample, or relevé, within one or more of the native plant communities at the site. Relevés involve marking out a standard-sized plot in a representative area of a plant community and listing all of the plant species in the plot along with information on the heights of the plants and their cover or abundance within the plot. These vegetation samples are used to develop statewide classifications of native plant communities and also provide descriptive information about the plant community.
- For small sites or sites that appear to be disturbed by recent human activity, the ecologist may confirm the quality of the vegetation from a brief field survey, from air photos, or from a "drive-by" survey.
- On occasion ecologists do low-level aerial surveys of sites. These are especially useful in landscapes with large tracts of native vegetation, such as Minnesota's northern peatlands and forests. Aerial flights provide information useful in refining site boundaries, assessing the condition of the vegetation, and targeting areas for field survey.
Condition Ranks for Native Plant Communities
Condition Ranks for native plant communities reflect the degree of ecological integrity of a specific occurrence of a native plant community. Condition Ranks are assigned by considering species composition, vegetation structure, ecological processes and functions, level of human disturbance, presence of exotic species, and other factors.
- Upland Prairie System–Condition Ranking Guidelines
- Wetland Prairie System–Condition Ranking Guidelines
- Prairie Extremely Rich Fen Condition Ranking Guidelines
4. Information management
After site and native plant community surveys are completed, ecologists finalize site and community boundaries and determine which sites and native plant communities meet minimum MBS standards for size and quality. Poor quality sites are eliminated from further consideration. For good quality sites, ecologists enter information collected during surveys into databases in the Natural Heritage Information System.
- Descriptive summaries of each site are recorded in the MBS Site Database. These summaries include information on landforms, soils, hydrology, native plant communities, rare plants and animals, kinds of disturbance, threats to the site, and statewide biodiversity significance.
- Site and native plant community polygons are stored in GIS shapefiles. These shapefiles are used to produce many different kinds of maps, including maps displaying the biodiversity significance of MBS sites and maps displaying native plant communities in a county or region.
- Data from relevé samples are entered into the DNR's Relevé Database, including plant community type and location, species data, and a brief written description.
- Ecological evaluations are written for selected high-quality sites. These reports provide detailed descriptions of the physical setting of the site, native plant communities, and rare plants and animals, and also provide information about threats and management concerns. They are used to guide conservation activity, such as special vegetation management, conservation easements, or acquisition as parks or natural areas.
- Ecologists also produce regional reports and books that describe the findings of the survey and provide context for the information collected by MBS.