4.0 Polygon Data and Interpretations

The greatest value of ecosystem unit characterization and mapping is in providing interpretations for a variety of disciplines (for examples, see Klinka, 1976; Lindeburgh and Trowbridge, 1985; Lea et al., 1990; Cichowski and Banner, 1993; and BC Ministry of Forests regional field guides) (Figure 4.1). The importance of interpretive mapping lies in the opportunities it gives users to evaluate the landbase for its land use values and sensitivities. The Forest Practices Code requires a number of land based interpretations related to operational and strategic level planning. Landscape unit planning, forest development planning and biodiversity requirements for maintaining forest ecosystem networks (including retention of old growth, the temporal and spatial distribution of cutblocks, and rare and endangered plant communities) are all examples of interpretations that can be accommodated by TEM.

Figure 4.1 Examples of possible interpretations from ecosystem map

For each mapping project, a digital map with an associated polygon database must be produced. Some examples of polygon attributes included in the database are polygon number, site series, structural stage, and genetic material. The number of individual data attributes that could be recorded for each map polygon is very large, especially compared to the information actually portrayed in a map unit label. The interpretative capabilities of any given map are based on the amount of data associated with each mapped polygon. Through the use of GIS, ecosystem map units may be combined to form interpretative or treatment units, where they share similar characteristics with regard to a specific resource value or management interpretation. As well, ecosystem maps can be readily combined with other data sources (such as bedrock geology maps and soils mapping) to allow further resource interpretations.

To ensure standardization of baseline ecological information, minimum data standards (core polygon attributes) have been developed for those data attributes common to many interpretations (Table 4.1). Additional attributes may be required to make specific interpretations for a particular project. Based on discussions with potential ecosystem map users, interpretations and corresponding data attributes have also been identified and grouped into five broad subject areas: biodiversity management, terrain and soils management, forest management, range management and wildlife management. Table 4.2 provides examples of possible interpretations under each of these areas. Terrain stability mapping is not an interpretation from TEM mapping, but is a separate mapping procedure.

4.1 Core Polygon Data

The attributes listed in Table 4.1 must be recorded for each map polygon. These core attributes constitute the minimum information that must be included when 1:50 000 and larger scale ecological inventories are conducted in the province². Core attributes are primarily interpreted attributes. Some, such as structural stage and a few site modifiers, can be modeled or derived from other sources. Others, such as Project name and ecosystem mapper are applied universally to the data file rather than interpreted for each polygon. Attributes such as ecosection and biogeoclimatic map unit designations need only be recorded once for each ecosystem map unit, while ecosystem and terrain attributes may be recorded up to three times for compound polygons.

² A standardized coding format for core polygon data should follow "Standards for Digital Terrestrial Mapping (TEM) Data Capture in British Columbia".

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