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Publications - Occasional Papers

Map of Mixed Prairie Grassland Vegetation, Rocky Flats, Colorado

INSTAAR Occasional Paper 35

1980, 66 pp. 2 plates. (cost: $5)

A color vegetation map at the scale of 1:12,000 of the area surrounding the Rocky Flats, Rockwell International Plant near Boulder, Colorado, provides a permanent record of baseline data which can be used to monitor changes in both vegetation and environment and thus to contribute to future land management and land-use policies. Sixteen mapping units based on species composition were identified, and characterized by two 10-m2 vegetation stands each. These were grouped into prairie, pasture, and valley side on the basis of their species composition. Both the mapping units and these major groups were later confirmed by agglomerative clustering analysis of the 32 vegetation stands on the basis of species composition. A modified Bray and Curtis ordination was used to determine the environmental factor complexes controlling the distribution of vegetation at Rocky Flats. So that a great number of zero similarities between stands would not occur, a growth-form data matrix was used as ordination input; this proved to be a satisfactory alternative to input of species data to ordination programs. It was determined during ordination trials that the above-mentioned ordination technique was more efficient and successful in interpreting the vegetation at Rocky Flats than principal components analysis when growth-form data input was used. Three environmental factor complexes correlated significantly with the ordination axes: percentage of nonvegetated area (X axis), moisture regime (Y axis), and grazing regime (Z axis). This correlation agreed well with the observations made during field work and during map analysis. The growth forms were shown to have a significant relationship with the controlling environmental factors. Recommendations are made for future policies of environmental management and predictions of the response to environmental change of the present vegetation at the Rocky Flats site.

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