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These matrix occurrences represent the viable matrix forest occurrences in the ecoregion. Tier 1 o ccurrences are the portfolio matrix occurrences. They represent the best examples of viable matrix forest and encompass at least 1 representative of each matrix Ecological Land Unit (ELU) group. Tier 2 occurrences are also viable matrix occurrences, but are not needed to meet representation goals for the portfolio. Tier 2 occurrences represent the alternate portfolio. Eight candidate matrix blocks that were dropped from consideration were preserved in this dataset; they have values of 0 in the "Tier" field. Matrix occurrences are bounded by features from the 1:100k US Census Bureaus TIGER line dataset such as roads, railroads, major utility lines, and major shorelines. The bounding block feature types were chosen due to their ecological impact on biodiversity in terms of fragmentation, dispersion, edge-effects, and invasion of alien species.

Purpose

Matrix sites are large contiguous areas whose size and natural condition allow for the maintenance of ecological processes, viable occurrences of matrix forest communities, embedded large and small patch communities, and embedded species populations. The goal of the matrix forest selection was to identify viable examples of the dominant forest types that, if protected and allowed to regain their natural condition, would serve as critical source areas for all species requiring interior forest conditions or associated with the dominant forest types.