differentiate the relative values of unfragmented habitat patches. Habitat patch size
classifications are intended to represent the habitat interests of various wildlife species
ranging from small mammals, reptiles and amphibians to larger wide-ranging mammals
such as black bear, moose (alces alces) and river otter (Lutra Canadensis). These
categories are: (a) 0-1499 acres; (b) 1500 10,000 acres; and (c) greater than 10,000
acres. The second size classification was designed to include the home range habitat size
of Vermont's wide-ranging mammals such as moose. The third and largest core area
classification was a product of the data as 44 parcels were outliers with over 10,000 acres
of unfragmented core habitat. It is assumed that the large habitat patches would provide
suitable habitat for many species of wildlife (Noss and Cooperrider 1994; Meffe et al.;
Hammond 2002). These size classifications were designed generally for comparative
purposes and do not necessarily reflect the exact habitat size requirements for specific
species.
The acreage of each core habitat polygon was used to calculate corresponding buffer
areas, as shown in Figure 1. The buffer analysis enables us to examine the value of
habitat outside the core habitat polygons based on proximity to those polygons. This is
important to identify areas of overlap between buffers for
separate core habitat polygons that may indicate a potential
connection between those habitats. We are assuming that
distance from core habitat polygons has some influence on
animal movement and use of core habitats. In order to keep the
buffer areas relative to the size of the unfragmented blocks the
buffers were designed as a function of the area of the core habitat
polygons. For each individual patch, the square root of the area
in acres was used to calculate a distance in meters. This distance
was multiplied by 1 through 5 to create 5 buffers around each
polygon relative to its size. The buffers were dissolved between
each polygon so that buffers from two separate polygons would
not be additive. By doing this it was possible to receive a value
for each cell corresponding to the highest value without giving
higher values to those cells in between core habitat areas. Once
the five buffers were created they were converted into raster
format and added together. This created a gradient from core
areas down to non-core areas. The final raster coverage
describes three sizes of core habitat and five zones of areas close to core habitat and
relative to the core areas' acreage. The values were normalized to values of 1- 10 to fit
into the analysis (see Table 2).
Figure 1. Unfragmented
Habitat and least cost
travel analysis
.
The buffer analysis allows the model to rank the value of habitat based on proximity to
unfragmented habitat. Furthermore, the model can now reflect the potential for habitat
patch size to influence wildlife habitat suitability.
7
Summary :
The buffer analysis enables us to examine the value of habitat outside the core habitat polygons based on proximity to those polygons. This is important to identify areas of overlap between buffers for separate core habitat polygons that may indicate a potential connection between those habitats. We are assuming that distance from core habitat polygons has some influence on animal movement and use of core habitats. The final raster coverage describes three sizes of core habitat and five zones of areas close to core habitat and relative to the core areas' acreage.
Tags :
size,areas,buffers,polygons,each,unfragmented,acres,analysis,alue,between,relatie,buffer,alues