He, 1993). Vegetation coverage, a GIS term, 
was used to distinguish this work from 
traditional plant inventories and vegetation 
mapping. The inventories do not attempt to 
create complete and continuous data such as a 
map or coverage about species composition of 
floristic communities. Traditional hard copy 
vegetation maps are fixed in time and 
resolution, unlike a GIS coverage, which can 
incorporate new data as acquired. The 
vegetation coverage employed here, represents a 
GIS approach towards an integrated 
manipulation of floral data. It has the 
characteristics listed below. 
* GIS digital vegetation layers, which 
contain polygons of species information 
and associated database records. The 
database contains multiple attributes of 
each polygon, such as dominant tree 
species, co-dominant tree species, 
identifications in a multi-level forest 
classification system, etc. 
* Several other spatial data layers which 
influence the vegetation or the 
interpretation of the coverage, such as 
topography, soils, hydrography, and 
administrative boundaries. 
* A flora database from field plots, which 
incorporates all available field inventory 
records. Precise plot locations are 
determined and linked with the above 
databases. The flora database can be 
used to support many spatial and non- 
spatial queries and analyses, such as 
species distribution or spatially 
associated species analysis. 
+ A flexible, hierarchical vegetation 
classification based on species 
composition. 
With the above characteristics, the vegetation 
coverage can provide hard copy vegetation maps 
at different scales and classifications, and also 
can support complicated spatial analyses which 
are difficult by traditional methods, such as 
selection and display of critical tree species 
distribution (e.g., hemlock, white cedar), and 
analysis of site conditions on which these occur. 
60 
METHODS 
The project integrated previous studies with new 
data from a recent flora inventory (Judziewicz 
and Koch, 1992), air photo interpretation and 
other environmental GIS data layers (Ventura 
and He, 1993). 
Data from Previous Vegetation Inventory 
Data from a recent vegetation inventory 
conducted by Judziewicz and Koch during 1991 
and 1992 were compiled by National Park 
Service staff into a flora database (FLORADB). 
Flora were observed on a regular grid of 200, 
300, or 400 meter spacing depending on the size 
of the (Eagle, Gull, Long and the Mainland Unit 
were not included) (Judziewicz and Koch, 
1992). These plots were quite systematic and 
complete in terms of both plot location and plot 
attribute recording. The database incorporated 
1424 field plots. It was converted to INFO 
format with more than 20,000 records, each 
representing a species description. The 
information derived from FLORADB can be 
used for species based analyses, such as 
dominance, commonness, and so forth. 
Since each surveyed plot had a recorded 
location, we built those plots into a point 
coverage. The point coverage can be used in 
association with FLORADB for many on- screen 
queries, or overlaid with other data layers such 
as a data layer from air photo delineation to help 
interpretation. 
Integrated Terrain Units (ITUs) 
ITU is a coverage which incorporates several 
environmental factors. It is typically generated 
from physical and biotic factors influencing 
vegetation, such as slope, aspect, soils, 
hydrography, and etc. Thus each ITU polygon 
has a unique combination of slope, aspect, soil 
type, and hydrological conditions. For the 
Apostles, these data were automated only where 
source material of sufficient quality to contribute 
to vegetation characterization was available 
(hydrography and terrain were used on all 
islands; soils were less available). 
All the data layers were prepared in the Arc/Info 
format from existing paper or mylar maps. 
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