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Revised September 1989 DETERMINATION OF SPECIES DIVERSITY STANDARD Coal regulations require the establishment of a diverse vegetative cover on reclaimed mine lands. Consequently, species diversity must be evaluated on revegetated lands prior to bond release. The Colorado Mined Land Reclamation Division (CMLRD) recommends using a simple comparison of species composition, life form, and seasonality between pre-mine communities and the revegetated area to demonstrate success in establishing a diverse vegetative cover (CMLRD 1988). WECC used the CMLRD-recommended method to establish the species diversity criterion for the Mt. Gunnison No.l Mine. Generally, the CMLRD-recommended method involves determining the number of perennial herbaceous species contributing greater than 3 percent relative production or cover in the pre-mine data for each affected community. The species in this group are used to determine the number of species and the seasonal growth patterns and life forms of each species to be established on the reclaimed area. To ensure that no one species dominates ,the stand to the • extent that desired species are inhibited, the maximum allowable relative cover value for any one species would be the relative cover value of the most dominant species in the pre-mine com- munities. For example, the pre-mine data from a hypothetical mine consist of the following species and relative cover values: • Aaronvron smithii 30$ • Bromus inermis 60~ • Poa nratensis 2~ • Melilotus officinale 8~ The species diversity standard would be the establishment of at least 2 cool season grasses and 1 perennial forb with relative cover values of at least 3 percent and less than 60 percent. According•to the CMLRD, success can be evaluated in two ways: based on direct comparison between a particular pre-mine community and corresponding parcel of reclaimed land or a .weighted average comparison based on the relative acreage occupied by all the various vegetation communities prior to disturbance. WECC has elected to use the direct community to parcel comparison approach, because the disturbed communities are sufficiently different to _.. warrant separate treatment. At the Gunnison No. 1 Mine, two vegetation communities will be disturbed: dry meadow and mixed-shrub wet. In the dry meadow community and mixed-shrub wet community four and five perennial herbaceous species contribute at least 3 percent relative cover, respectively (See Tables 2.3.5.6.A and 2.3.5.7.A). In the dry meadow community the species are Aaropyron smithii (63$); Bromus •~ Y" F