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MANAGEMENT IMPLICATIONS ASSOCIATED WITH LAND
STRATIFICATION AND HABITAT TYPING
Ronald K. Tew
ABSTRACT: The Boise National Forest is following
land systems inventory procedures to identify
resource values and management constraints.
Habitat-typing concepts are used to refine the
inventory data and provide additional interpretations on land systems units. Several levels of
inventory are used to meet planning needs.
FOREST STRATIFICATION
The land systems inventory process presented by
Wertz and Arnold (1972) provided the original
framework for land stratification on the Boise
National Forest. Work by Wendt and others (1975)
expanded the interpretations and provided a Forest
map. Since that time, additional changes have
been made using the concepts of Arnold (1975) and
Bailey (1980) to obtain a broader frame of reference than just the Boise National Forest.
INTRODUCTION
Land management planning is currently being done
on National Forest System lands as required by
the National Forest Management Act of 1976. Broad
inventories, together with site-specific evaluations, provide the basic data for preparing plans
and for making critical land management decisions.
The site-specific information is also used extensively in preparing environmental assessments and
in selecting areas to be improved.
Bailey's map was used to identify analysis areas
for the Forest Service Regional Plan in the Intermountain Region (USDA Forest Service 198lb). The
Boise National Forest is located within the Northern Rockies Analysis Area, characterized by the
grand-fir-Douglas-fir vegetation types.
Within the Northern Rockies Analysis Area,
subsections identified by Arnold (1975) were
superimposed on the forest base map. These subsections established differences in basic geologic
structure and landform and helped refine analysis
areas. The resulting units are the zones previously defined. Landtype associations recognized
by Wendt and others (1975) were expanded to
provide contiguous units within these zones. The
stratification process used in delineating associations was based on five broad geomorphic
groupings: (1) Glaciated lands formed on
high-elevation landscapes, (2) cryic lands occurring on frost-churned areas at moderately high
elevations, (3) fluvial lands formed on landscapes
dominantly affected by the erosive action of water,
(4) volcanic lands formed on flows and cones, and
(5) depositional lands resulting from glacial
moraines, outwash materials, and alluvium.
Much of the data required is being collected
through land systems inventories (Wertz and Arnold
1972; Bailey 1980). Habitat types (units of land
that are capable of producing similar climax vegetation) are used to refine inventory units by
recognizing vegetation types that are indicative
of an integra~ed moisture and temperature regime.
Although nine levels of land systems inventory are
recognized by Bailey (1980), only three levels
will be discussed here. The most inclusive of
these three levels will be referred to as "zones."
Zones are broad units of land with similar geologic
structure, landform, and climate. Within zones,
"landtype associations" are recognized on the
basis of landform, soils, geology, and climate.
"Landtypes" are identified within the associations.
They provide more site-specific information on
landform, soils, and vegetation. Habitat types
or groups of habitat types are recognized within
any land systems level desired.
All or portions of 21 zones were established to
cover approximately 3 million acres of land. From
three to five landtype associations were recognized
within each zone. More than 100 landtypes were
identified throughout the forest.
All three levels are being used to: (1) Describe
the location of resources available for management, (2) improve predictive capabilities in terms
of production potentials and limitations imposed
on management within sensitive environments, (3)
provide a basis for extrapolation of information
from one unit of land to another, (4) improve
interdisciplinary communication where a common
land base has been established, and (5) provide
a relatively homogeneous environment that reduces
sampling variation.
GEOLOGY AND SOILS
Granitic (quartz monzonite and granodiorite)
parent materials of the Idaho Batholith cover
approximately 85 percent of the Boise National
Forest. Soils are sandy and often shallow to
moderately deep over fractured decomposed bedrock.
Clayton and Arnold (1972) have described the
differences in bedrock characteristics in terms
of structure, texture, weathering, and fracturing
qualities which affect the type of soil being
developed.
Ronald K. Tew is Range, Watershed, and Wildlife
Officer on the Boise National Forest, USDA, Forest
Service, Boise, Idaho.
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Basalt flows are common on the southern end of the
forest where deeply cut canyons overshadow the
streams. A limited acreage of structurally controlled basalt lands with west-facing dip slopes
occurs on the west-central portion of the forest.
In the basalt parent materials, soils are often
shallow, cobbly clay-loams, although some sites
have moderately deep to deep soils that are very
productive.
Sampling Intensity
Because inventory and sampling is a continuous
process, one must decide the proper level of
sampling. Previous inventories provide the measure of variation needed to make these estimates.
Although the example being used relates to range
production, equal use can be made of the homogeneous land units for wildlife studies, soil
monitoring programs, timber production estimates,
and similar studies.
MANAGEMENT IMPLICATIONS
Using range analysis data, it is possible to
determine the coefficient of variation for production studies and relate these values to the
number of samples needed to obtain acceptable
estimates. The coefficient of variation expresses
the sample standard deviation as a fraction of
the sample mean and is useful in calculating sample size using the following equation:
Discussion of management implications associated
with land systems inventory and habitat typing
is limited to production potentials, sampling
intensities, extrapolation of data, sedimentation
and mass wasting problems, and implementation of
watershed and forage improvement projects.
Range Forage Production
where
Forage production has been measured on range
allotments for many years. In the past, information has been collected by range type (sagebrush/
grass, dry meadow, etc.) without correlation to
soils and habitat types. As a result, sampling
variability has been greater than desired.
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Because range forage sampling sites were identified on maps, they can now be correlated with
mapped land systems units. Also, because range
habitat types have been established for Idaho,
this concept can be applied to the older inventory
information by recognizing key species identified
on inventory forms.
E
the number of samples needed.
a tabular value from the student's t-distribution based on a specified confidence level
and on sample size.
the coefficient of variation.
the percent variation from the true mean
value that is acceptable (expressed as a
decimal).
A quick evaluation of the equation can be made
by referring to figure 1.
With major funding constraints, there will be few
opportunitie~ to continue range analysis in the
traditional manner, yet production information is
still needed to prepare adequate plans for allotment management. To meet this demand, information
from approximately 1,300 transects was assembled
and analyzed. Production was evaluated by range
types on land systems units at various levels of
stratification.
Although this type of analysis helped in interpreting production values, there was a real need
for further refinement. It was recognized that
year-to-year variation was great and that production and species composition varied greatly
within range types, which included many habitat
types. Also, it was common to only have 1 year
of inventory data.
0~--~----L---~----L---~----~--~----L----L--~
10
30
40
50
NUMBER OF SAMPLES
To improve interpretations, information was sorted
into habitat types. Herbage production was then
summed, using data from 1963 to 1981. Production
by habitat type was established for individual
species of grasses, forbs, and shrubs together
with totals for each of these categories. Forage
values were assigned to individual species and
total herbage production was adjusted based on
differences in species palatability. Using many
years of data greatly increased the reliability
of production estimates on specific areas identified in the land systems inventory.
Figure 1.--Relation between sample variability
and the number of samples needed for various
levels of precision.
This figure is based on a 20 percent confidence
level and has curves for ±10 to ±40 percent of
the true mean for any coefficient of variation
specified. The number of samples needed to reach
an acceptable level of precision can be read
directly from the curve without having to go
through several approximations with the equation.
Although a 20 percent confidence level is used
3
Because onsite erosion, as well as stream sedimentation, are evaluated, it is possible to predict
average changes in water quality and to relate to
fisheries interpretations. Although surface
erosion is usually insignificant on forested
watershed, it becomes an important factor to consider on lands disturbed by man's activities.
and is assumed to be acceptable for range sampling, curves for other confidence levels can also
be easily prepared.
Data Extrapolation
Because funding and time constraints limit the
amount of sampling that can be done, the system
being described provides a basis for extrapolating
present information to units of land where no
information has been obtained. The data previously
described can be used to extrapolate production
estimates to land units where no sampling has been
done. The range type or habitat type must be
identified for the unit of land in question
together with the land systems unit that has been
mapped. The production estimates can then be
used directly. It is best to keep the extrapolation of data within the mapped zones because
of differences encountered between zones.
Mass erosion hazards related to soil failure and
movement of material by gravity, either slowly
or quickly, can be a significant factor on many
landtypes. Therefore, hazard ratings are assigned
to all landtypes and are used in the total sediment
yield predictions on selected watersheds. By
combining the sediment yields from natural processes with yields from surface erosion and mass
erosion, a total sediment yield can be predicted.
The ability of soil scientists and hydrologists
to adequately predict sedimentation may truely
determine the use constraints on critical watersheds in the near future.
Restoration and Improvement Work
CONCLUSIONS
Land systems inventory and habitat typing have
significant values in restoration work. Some
important considerations include: (1) The land
areas suitable for seeding, planting, burning,
spraying, or for some type of mechanical treatment
can be easily identified and a backlog of work
needs programed for accomplishment, (2) predicted
responses for any given environment can be made
including planting success on trees and shrubs,
increases in production following seeding or
burning, limitations associated with hot or cold
temperatures, moisture deficits or excesses, and
slope stability and erosion concerns, and (3) seed
collection and planting can be tied directly to
the habitats of. concern as well as selecting
adapted species that will increase success of
restoration projects. The need for such improvements as water developments can also be related
to land units in a general way.
Land systems inventory units combined with habitat
typing concepts provide a useful land management
framework. Resources available for management can
be cataloged in an orderly manner using a land
stratification system. Communications between
disciplines are improved when land units have bee~
clearly defined. This becomes a critical factor
in more aspects than is commonly recognized.
Sampling and extrapolation of data from one unit
of land to ~nother can be greatly improved. This
can effect significant savings, which is important
during periods with rapidly declining budgets.
Predictive capabilities on sediment yields, site
productivity, and response to restoration work are
greatly improved by characterizing land units.
Because of these advantages, land systems inventories in combination with habitat typing concepts
can be highly recommended for characterizing lands
where management is being intensified. Continual
improvement is needed to meet changes in management
direction. This change is what makes management
difficult, but it also provides challenges.
Erosion and Sedimentation
Slope instability and sedimentation are a major
concern to land managers in the Idaho Batholith
because sediment constraints are tied directly
to management activities. In order to meet
requirements in various plans, sedimentation
associated with fire, road construction and maintenance, mining, grazing, and timber harvest
activities must be planned for, controlled, and
monitored closely. The land manager must understand slope stability as it relates to bedrock
structure, texture, weathering, fracturing qualities, and landscape characteristics.
PUBLICATIONS CITED
Arnold, John F. The Idaho Batholith -A source of
information. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain
Region; 1975. 290 p.
Bailey, Robert G. Description of the ecoregions
of the United States. Ft. Collins, CO: U.S.
Department of Agriculture, Forest Service; Misc.
Publ. No. 1391; 1980. 77 p.
The sediment prediction procedure currently being
used on the Boise National Forest is applied on
watersheds that are stratified into land systems
inventory units (USDA Forest Service 198la). The
model is used to predict natural sediment levels
together with current rates and any increase that
might be created by management activities. Cumulative effects are evaluated over time, taking
any increase in sedimentation into account and
evaluating the rate of return to natural levels.
The information is useful in comparing impacts of
different alternatives being considered in the
planning process.
Clayton, James L.; Arnold, John F. Practical grain
size fracturing density, and weathering classification of intrusive rocks of the Idaho
Batholith. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain
Forest and Range Experiment Station; Gen. Tech.
Report INT-2; 1972. 17 p.
4
U.S. Department of Agriculture, Forest Service.
Guide for predicting sediment yields from
forested watersheds. Ogden, UT. Missoula, MT:
U.S. Department of Agriculture, Forest Service,
Northern and Intermountain Regions and the
Intermountain Forest and Range Experiment
Station; 198la. 112 p.
A draft Regional plan for the Intermountain
Region. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain
Region; 198lb. 92 p.
Wendt, George E.; Thompson, Richard A.;
Larson, Kermit N. Land systems inventory,
Boise National Forest, Idaho. Ogden, UT: U.S.
Department of Agriculture, Forest Service,
Intermountain Region; 1975. 54 p.
Wertz, William A.; Arnold, John F. Land systems
inventory. Ogden, UT: U.S. Department of
Agriculture, Forest Service, Intermountain
Region; 1972. 12 p.
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