Geoscience Reference
In-Depth Information
Table 16.2 Patch-Based Landscape Metrics Describing Forest in
Michigan's Huron River Watershed as Mapped in the NLCD
Data Compared with a Separate Classification of Forested
Cover Derived from Landsat TM; All Metrics Are Summarized
at the Class Level for the Forest Patches
Metric
NLCD Forest Data
Forest Cover Classification
Percentage forest
No. of patches
Mean patch size (ha)
Edge density (m/ha)
Mean shape index
Total core area index
28.1
28857
2.17
106.05
1.37
37.33
31.1
19137
3.62
85.33
1.37
50.53
Table 16.3 Percentage of Generalized NLCD Forest Classes Based on
the Classification of Landsat TM data and the Percentage
of the Total Forested Cover within each NLCD Class
Generalized NLCD Class
% Forest Cover
% Forest Cover Total
Urban
5.6
5.6
Forest
57.1
65.1
Agriculture and Herbaceous
13.2
25.8
Other
17.5
3.5
Total
100.0
Note:
The first column indicates how much forested cover was contained
within each NLCD class. The second indicates the amount of the
forested cover within each class.
within forest classes as defined by NLCD, 25% was located in agricultural areas and
<
6% in urban
areas (Table 16.3).
These findings indicate that landscape metrics are sensitive to the definitions of the input classes.
This sensitivity is a result of differences in the meaning of the classes themselves rather than the
lack of classification detail or because of inaccuracy in the classification. For some landscape
analysis purposes (e.g., habitat of a wildlife species), accounting for forested urban areas may be
important. Therefore, some LC classifications, while not necessarily inaccurate, may be inadequate
for some purposes.
16.4.2.2
Comparing Photographic Classifications
Urban LU classes, as identified from aerial photographs, all had some amount of forest and
impervious cover (Table 16.4). This comparison again illustrated the importance of class definitions
but raised the additional issue of class definitions based on LC vs. LU. In the case of LU, the
diversity of cover types that made up residential areas was lumped together to map the LU type
termed “residential.” Cover types contained within urban LU regions included impervious surfaces,
forest, and others (e.g., grasslands).
Table 16.4 The Percentage of Impervious Surface
and Forested Cover within Three Urban
Land-Use Classes
Land-Use Class
% Impervious
% Forest
High-density residential
36.1
15.4
Low-density residential
23.1
16.8
Other urban
45.4
19.1
