Foothills Fescue Range Plant Community Guide - Sustainable ...

5.0 Classification Methods
5.1 Plant Community Classification Methods
Data for this analysis consisted mostly of range survey and rangeland reference area data
collected by Alberta Sustainable Resource Development from 1986 until present. A total
of 487 vegetation inventory forms were analyzed. All data records were reviewed for
completeness, species seven letter codes were assigned along with a unique identifier
number for each transect. The data were then entered into the Prairie Data Base
(Rangeland Management Branch, Alberta Sustainable Resource Development). The data
base calculates mean values for species composition, total vegetation, moss/lichen and
bare soil cover.
The results of vegetation transect queries were extracted from the Prairie Data Base and
formatted for analysis in a two dimensional matrix in the *.wk1 format that PC-ORD
requires. Ordination and classification studies were carried out on the data sets using PC-
ORD (MJM Software, Gleneden Beach, Oregon). The corresponding land data including
soils and site information were sorted into a corresponding land data matrix.
In order to establish major plant community types, ordination and classification
interpretations were developed by using two statistical procedures (Willoughby 1997):
a) De-trended Correspondence Analysis was applied (Gauch 1982). This procedure
compares similarity and dissimilarity among sites. Plotting of the ordination scores in
three dimensional “species space” allows viewing of site and species distributions and
facilitates grouping of sites by community types.
b) A cluster analysis procedure was employed as an alternate grouping technique to
compare and contrast with the results of the DCA procedure. Ward’s method of cluster
analysis was the most easily interpreted from the six or more procedures that might be
chosen.
Plant community type summaries were generated in Quattro 9 by averaging plant species
composition, range in composition and percent constancy of occurrence among groups of
vegetation inventory plots considered to form a unique plant community type.
Environmental data were subsequently sorted into the same plant community groups as
described above for further analysis and correlation with plant community groupings.
Total vegetation canopy cover, moss/lichen and bare soil estimates were also calculated
for the plant community type groupings of vegetation inventory plots. The resulting plant
community descriptions are reported in one page summaries similar to those used by
Willoughby et al. (2003).
Ecologically sustainable stocking rates (ESSR) values are suggested for each plant
community. These values reflect the maximum number of livestock (e.g.Animal Unit
Months (AUM)/acre) that can be supported by the plant community given inherent
biophysical constraints and the ecological goal of sustainable health and proper
functioning of the plant community. When the ESSR is multiplied by the area (e.g. acres)
of a plant community polygon the result is termed ecologically sustainable carrying
capacity (ESCC), and is expressed as AUMs. At times, the ESCC must be adjusted for
management factors (e.g. reduced livestock distribution), management goals (e.g.
improve rangeland health, multiple use and values, etc.), drought conditions, and other
natural phenomena impacting the site (e.g. forage quality, fire, pests, etc.). This
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