FIRE EFFECTS GUIDE - National Wildfire Coordinating Group

habitat size is approximately 200 acres (81 hectares). It is recognized
that habitat requirements of individual species determine the relative
potential benefit of a particular size burn where species richness is not
the primary objective.
A seldom discussed aspect of habitat quality is that of habitat
fragmentation (Reese and Ratti 1988, Rosentreter 1989). Small isolated
islands of shrubs and trees following prescribed or wildfire are examples
of fragmented habitat. Many wildlife species exhibit high extinction rates
in fragmented habitat (Wilcox 1980). Fragmented habitat fails to provide
areal extent and linkages between and among components that are
implied with "quality" mosaic, juxtaposition, interspersion and diversity
for a given species or collection of species. Adequate linkage of habitat
components (e.g., a stringer of cover connecting larger areas of escape
cover) is a determining factor for many species. As with other
wildlife/habitat considerations, some species are favored over others by
a particular mosaic or juxtaposition of elements and a few species may
be eliminated entirely.
c. Burned area location. The location of a burn relative to animal use
patterns can have a major influence on subsequent use. The proximity
of propagules or potential inhabitants has an influence on what species
may occur on a burn site. Species mobility also plays a part. A young
bighorn ram may travel miles, a shrew (Sorex spp.), hardly any.
Whether potential inhabitants can see, smell or be expected to wander
across a burned area may dictate the presence or absence of a
particular species. An otherwise "excellent" burn (prescribed or wild)
that is too distant from traditional use areas (e.g., bighorn) may not be
utilized in any reasonable timeframe. Proximity of the burn to a critical
habitat component such as water or cover also determines use. Sage
grouse exhibit a reluctance to use water sources devoid of adequate
surrounding cover. In contrast, pronghorn generally avoid water sources
screened with tall dense vegetation. Loss of a critical habitat component
and how soon - if ever - that element is replaced may be of paramount
importance. Burn location can strongly influence ultimate vegetational
establishment. A small stand of Douglas-fir (Pseudotsuga menziesii) on
a steep south exposure may - from a practical standpoint - never
regenerate whereas a similar stand on a more moist north exposure
may be restocked in comparatively few years. Slope, aspect, and
elevation affect snow deposition, snow crusting, thermal patterns, and
wind conditions on burned areas. All of these factors have a bearing on
habitat quality for a given species.