2.3.3. Calculation of the suitability index
We assessed waterbird habitat suitability in the West Songnen
Plain by overlaying factor layers using ArcGIS 9.3 software. These
data layers were translated into numerical data before the index of
habitat suitability was calculated, and all data were standardized.
The waterbird habitat suitability was graded as good (75–100), fair
(50–75), poor (25–50), and not suitable (0–25).
The AHP method was adopted to determine reliable and
objective weights for the factors. This method combines the relationships
between habitat suitability factors (David and Ludwig,
2006). The main steps of the AHP to determine the weights of
each factor are as follows (Dolan, 2008): (1) define the decision
elements (habitat suitability factors); (2) construct the decision
model, with a linear function adopted to calculate the integrated
index; (3) decompose and make pairwise comparisons to determine
local priorities; (4) combine the scales created through the
pairwise comparisons to determine how well the options can be
expected to meet the goal; (5) perform a sensitivity analysis,
if desired, to allow a range of sensitivity analyses to determine how
different judgments or assumptions affect the analysis; (6) either
make a decision or go back and refine the analysis until everyone
is satisfied that a decision can be made.
2.3.3. Calculation of the suitability indexWe assessed waterbird habitat suitability in the West SongnenPlain by overlaying factor layers using ArcGIS 9.3 software. Thesedata layers were translated into numerical data before the index ofhabitat suitability was calculated, and all data were standardized.The waterbird habitat suitability was graded as good (75–100), fair(50–75), poor (25–50), and not suitable (0–25).The AHP method was adopted to determine reliable andobjective weights for the factors. This method combines the relationshipsbetween habitat suitability factors (David and Ludwig,2006). The main steps of the AHP to determine the weights ofeach factor are as follows (Dolan, 2008): (1) define the decisionelements (habitat suitability factors); (2) construct the decisionmodel, with a linear function adopted to calculate the integratedindex; (3) decompose and make pairwise comparisons to determinelocal priorities; (4) combine the scales created through thepairwise comparisons to determine how well the options can beexpected to meet the goal; (5) perform a sensitivity analysis, if desired, to allow a range of sensitivity analyses to determine howdifferent judgments or assumptions affect the analysis; (6) eithermake a decision or go back and refine the analysis until everyoneis satisfied that a decision can be made.
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