based on ecological responses. In other words, 
biodiversity can be assessed across a region by the 
differentiation and location of separate BLUs - 
homogeneous response units defined spatially by 
attribute composition. 
Another important spatial modeling concept of BLUs 
for biodiversity is the desirable effect of retaining the 
"patchy" detail of existing environments. BLUs 
provide spatial definition of complex ecologic details 
in a form that can be graphically displayed in a single 
map layer. This single layer can display the first level 
of analysis - the "core components" of existing 
environments, to which a few other defining layers 
(lice administrative boundaries or cultural features) 
can be added for reference, without confusing 
displayed information beyond the point of recognition 
and interpretation. Focus is on spatial patterns and 
the assemblages of those patterns (communities) 
and the ecotones which provide the transition 
between homogeneous areas. The approach allows 
the analyst to better understand the dynamics 
occurring in the ecological system and not become 
overwhelmed with specifics of multiple data layers. 
As previously mentioned, the spatial patterns of 
homogeneous BLUs may not always be visually 
distinct, (without GIS), but defined rather by ecologi- 
cal responses. 
The emphasis, therefore, becomes one of dynamics, 
anomalies, edge conditions, seral stages(s), stability, 
and sustainability. Inferred information derived from 
the interface of components of the BLU are tested 
with field visits and comparable landscapes to better 
understand the natural system in any locality. 
ASSESSMENTS AND ENHANCEMENTS 
When areas of anomalies have been identified, field 
verified and found to require more detailed analysis, 
another step in the hierarchy of BLU resolution is 
added. Additional spatial data layers can be overlaid 
to isolate possible contributing dynamics, or site 
specific data can be collected, geocode and ana- 
lyzed. 
Work is currently underway to enhance BLU model- 
ing methods using site specific data. Site data, like 
transects, correlate detailed snapshots in time to the 
broader scope, more generalized spatial snapshots in 
time provided by satellite remote sensing data. 
Satellite data, along with subsequently derived layers 
like BLUs, provide total area coverage. It has long 
been recognized that one of the most practical uses 
of satellite data is the identification of areas where 
more specific data collection and evaluation methods 
are required. This same simple notion supports the 
BLU concept of hierarchal scales of detail, allowing 
bi-directional flow of information between generic, 
regional dynamics, and local, more specific dynam- 
ics. 
An ultra simple, practical example is an effort to 
automate and link transect data to satellite data, and 
BLUs. The approach is to use: transect data collect- 
ed into polycorder files, Global Positioning System 
758 
(GPS) data for geocoding transect location, and at 
those transect points, use of a simple compass for 
determining the vector of transects in relationship to 
spectral classes and BLUs. 
Attempts to correlate historic transect data digitized 
into GIS has revealed only a weak correlation with 
satellite spectral data. Many historic transects appear 
to have been selected within, and parallel to ecotone 
areas, probably in an effort to get the best possible 
representation of diversity, while trying to conserve 
in numbers of personnel and field time. This makes 
it very difficult to relate site specific data to generic 
alternatives management is forced to choose be- 
tween on a regional scale. These choices could easily 
be confounded by shifts in ecotone areas, which are 
areas most sensitive to change. Further, if it were 
determined that changes were occurring, it would be 
difficult to determine the extent or percent of change 
in an area, and what the change represents. 
The current effort using the previously mentioned 
technologies would use BLUs to locate sites for 
transects. Locations would include sites well within 
a homogeneous area, allowing a clear definition of 
the community assemblages. Locations could also 
include transects perpendicularto ecotones, and thus 
spectral or community boundaries. Transects could 
also be long enough to bisect the boundary and 
allow for boundary shift through time. With a 
reasonable correlation of transect data to BLUs, it 
should be possible to track subtle shifts in local 
ecological dynamics. 
MONITORING AND APPLICATIONS 
In the EI Malpais National Conservation Area (NCA), 
(at a 30 meter cell sampling scale), BLUs have 
already been used to detect change, and consider: 
the rate, amount, and direction of change; as well as 
the relationship of change to management manipula- 
tions and fluctuations in weather patterns. For 
example, habitat patchiness, difficult to quantify 
without GIS derived BLUs, and a critical component 
in management of biodiversity, has been recognized 
as becoming more homogeneous in some areas of 
the EI Malpais NCA. One possible management 
response to this change may be relaxation of "full 
suppression" in fire management. 
Another use of BLU tracking of change in biodiver- 
sity is the delineation and monitoring of ecological 
components that represent only a small percentage 
of a protected area. Tracking these areas, and using 
GIS to overlay management alternatives, could 
eliminate the areas from consideration for incompati- 
ble uses like a camping area, interpretive trail, or 
range improvement. GIS graphic representation of 
BLUs and the conflict resolutions are then useful for 
policy implementation within an agency, and for 
public information, especially when use restrictions 
are necessary. 
The hierarchal framework of BLUs, besides providing 
flexibility in scale and detail of components of 
current conditions, is meant to facilitate correlation