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USE OF A HABITAT/NICHE MODEL FOR OLD GROWTH MANAGEMENT:
A PRELIMINARY DISCUSSION
Bruce G. Marcot
Oregon State University
Corvallis, Oregon
Cautious analyses of ecological interrelationships and
extent of behavioral stereotypyare necessary requirements
within any forest management program for avian species.
(McEllin 1979)
ABSTRACT
The basic tenets of a life history approach to a wildlife habitat
relationships information base are explored. The life history
approach involves detailing habitat, niche, and general descriptors
of each wildlife species, and sifting by a computer program to
generate groups of functionally-related species. An example of
the model to assess stand conditions for obligate old-growth
wildlife species is provided.
INTRODUCTION
With recent legislations guiding multiple-resource management on National Forest
lands (see Salwasser et al. 1980), the need is great for a multi-species approach for
the assessment of habitat conditions for forest and rangeland wildlife, including
nongame birds. Such a multi-species approach should be effectively incorporated into
the management system in regard to specialist input and planning needs. The approach
also should be user-oriented and theoretically sound, and should deal with terrestrial vertebrate species of both emphasis and nonemphasis statuses.
This paper explores some of the basic tenets underlying a habitat and niche
based multi-species model, and an example of how the model may be used to aid management of older age stands of timber for wildlife.
Model Axioms
The model to be explored is a product of the California Wildlife Habitat Relationships (WHR) Program of the U. S. Forest Service (Salwasser et al. 1980). The WHR
involves a compilation of information on the life histories and habitat relationships
of species of amphibians, reptiles, birds, and mammals. The goal of the program is to
develop new tools to assist biologists and planners to assess occurrence of and change
in wildlife species in relation to existing and potential land managemen~ activities.
390
Conceptual Framework
Warren et al. (1979) define a conceptual framework as a set of axioms characterized by low verifiability and high explanatory power, existing at the "most encompassing level amenable to reasonably complete and adequate verbal articulation." Using
this notion, the conceptual framework of the habitat/niche model involves the following tenets.
1.
Wildlife habitat is a product of forest and wildland management.
Thus, wildland management is wildlife habitat management, desirable or undesirable (Thomas 1979).
2.
The degree to which wildlife habitat is managed desirably is dependent on a) the accuracy of prediation and simulation models
of wildlife habitat relationships, and b) how well a WHR program
can be integrated into multi-resource management schema.
3.
All habitat types and their seral stages provide suitable conditions for some groups of wildlife species (Thomas 1979).
The Blue Mountain tome of Thomas et al. (1979) goes a long way in establishing
an ecological, interdisciplinary and even socio-political conceptual framework under
which a WHR program and subservient models may be subsumed. "Species have niches
and habitats" is but one of the numerous tenets of the ecological facet of this conceptual framework. Another and a more general tenet is that "the concepts of species
and viable populations are meaningful and are a useful base for conducting wildlife
resource management." The mandates of the National Forest Management Act of 1976
(NFMA) specifically addresses management for retaining viable populations. The conceptual framework provides a foundation on which a habitat/niche model may arise.
Theoretical Generalizations
On a logical level down from the conceptual framework, the theoretical generalizations of the approach to be considered here involves a detailing of the life
history characteristics of each wildlife species in terms of their environmental
needs. The environmental needs of species can be specified along the lines of niche
theory and macrohabitat (vegetation type) affiliation.
At the base of this detailing of species' environmental needs is the fundamental
tenet that only species' life histories and ecological performances define such
(theoretical) terms as (suitable) habitat, viability, facultative and obligate associations with habitat elements, and niche. That is, in contradistinction to an
agglomerative approach which may ~ priori assign species to ecological categories or
roles, the proposed life history approach allows such categorization~ posteriori in
a nonfixed manner. Such ecological categories as life forms, guilds, species types,
habitat use, and levels of response to habitat change, are generated in the divisive
approach from initial life history details. To be sure, certain categories are initially given, such as the species/habitat matrix, but these are still subsumed in an
interacting life history information base and are generative of categories, indices,
etc. in a functional and fundamental way. The agglomerative approach, on the other
hand, may begin with a particular category or index as "fixed" and from this say
things about species' viability or response to habitat shifts.
The enumeration of a species' environmental needs as a theoretical generalization may be regarded in light of the species' habitat ("address") and niche ("occupation"). The WHR information base allows the description of species' habitats (the
391
I
species/habitat matrix) and niches (the life history narratives) in a categorical and
codifiable fashion. (Emphasis species guidelines and special habitat narratives can
serve to deepen these descriptions.)
A guiding tenet of the division of species into such detailed life history
categories, at the level of theoretical generalizations, is that specific life history
information can be used to develop predictive capabilities and simulation models, to
help assess (i) effects on the wildlife resource from habitat manipulation and (ii)
spatia-temporal arrangement of habitats (macro and micro) necessary to optimize a
particular fauna, to meet particular goals for wildlife management. The question of
whether this habitat-and-niche approach is either adequate or necessary will not be
addressed here.
The life history approach seeks to describe species in details of their.behavior
and their ecological and geographical distribution. This description may be aided,
in part, by adopting a multiple-category niche model. As well, distributions may be
described by a combination of habitat descriptors {specifically, vegetation types and
their seral or structural stages) and political geographic locators. Additionally,
political and social categories, such as legal statuses, taxon/species i.d. numbers,
and some indication of social concern or desirability, may further describe each species.
Another theoretical generalization is that the divisive approach may be based
on, and feed back into, habitat management as contrasted against single-species population management. From a multi-species approach, planning scales may widen to encompass as large a land base as necessary.
Theorems and Models
Following the life history approach, a number of more specific theorems and
models may be informally deduced.
Species can be grouped according to functional (habitat and/or niche) relations
into species groups or guilds. The grouping of species in the model used below is
based on a computerized data storage and access system, the Wildlife Habitat Information Matrix Program (WHIMP), of the WHR. WHIMP uses multi-level boolean algebra
to allow sorting (delineation of habitat or niche parameters) and sifting (grouping
of species having the specified characteristics) through the WHR information base,
which is set up to represent various categories of each species' habitat, niche, and
other general descriptions (Table 1).
Table 1.
Species-specific categories of information coded for computer access by the
Wildlife Habitat Information Matrix Program.
GENERAL DESCRIPTORS
Species common name
Species scientific name
Taxon/species i.d. no.
Legal status
Abundance, by geographic
landbase
NICHE DESCRIPTORS
Nesting substrate
Diet items
Residency
Foraging substrate
Foraging methods
Time of diel activity
Breeding season, range and peak
Territory size, range and mean
Breeding home range, range and mean
Wintering home range, range and mean
Nest height
392
HABITAT DESCRIPTORS
Vegetation types {by
seral or structural
stages)
13 zonal types
5 azonal types
Life functions,
by levels of use
Breeding
Feeding
Resting
Season of use
Guilds or groups can be a set of species bracketed by management activities as
such activities affect the species' habitats and/or niches.
A guild-generating model can make (testable) predictions of species occurrence
and changes given a description of a habitat and its manipulations.
A guild-based model can generate indicator species based on detailed functional
relations and fealties to micro- and macro-habitat elements.
Several levels of models may be used in the life history approach: (1) simple
storage and sifting access of WHR information for a generalized predictive tool; (2)
statistical treatment of particular, sifted information; and (3) higher-level ecologi~
cal or mathematical assessments of within- and between-group parameters, e.g. indices
of niche/habitat breadth and overlap, for more site-specific predictions.
Further, each species needs to be described in detail (niche, habitat, and
general descriptors) in order to effectively combine species management needs, such
as by optimizing habitat diversity for particular groups of species.
Wildlife management may be thought of, in part, as the descriptions of a range
of manipulations in a given space, over time, for particular groups of species, that
balance or optimize species' needs. This range of management options to·attain a
particular optimum ·for wildlife may then be narrowed down according to the needs of
other resources. Other resources may similarly identify the range of options that
would still meet· ~their management goals and objectives. The overlap of options among
different resources' management is the range of total management options, over time,
that will meet needs of most or all resources in a given management area. (This
overlap may also be derived through linear programming, n-person games, iterative
solutions of effects on land base suitabilities from different resources' management
options, graphic multi-resource assessment of mini-max or saddle points, etc. While
such multi-resource management and planning goes beyond the domain of the present
discussion, the life history approach nonetheless may provide deductively-derived
models to fit into this schema.)
I·
DEFINITION OF "OLD GROWTH" -- A Brief Discussion
The term "old grm:vth" literally refers to a mature age class of vegetation, a
seral descriptor, but stand age is only one variable of a forest habitat. Because
various types of land modification - especially timber harvesting - can cause such
a wide spectrum of changes, the specific component or structural descriptors of
"old growth" that the wildlife manager is most interested in must be clearly defined.
Among the components of "old growth" that may be of importance to wildlife
species and that may be affected by land management practices are:
1.
2.
3.
4.
5.
6.
7.
8.
large-sized trees
old-aged trees
decadence of standing vegetation
much dead and down woody material
uneven-aged vegetation
multi-layered vegetation
moderate foliar height diversity
mesic microhabitats afforded by high canopy closure.
Many components that are associated with old growth can be differentiated and
defined according to different wildlife species' needs. Indeed, to arrive at a
singular definition of old growth is a dubious goal. What is therefore recommended
is to define old growth in terms of any combination of these or other attributes, as
393
'·
I~ ,
I
delimited by the needs of species that are to be managed in a particular area. Not
all the attributes of old growth as listed above may be met on every site. Managing
old growth areas for wildlife therefore may involve knowing the specific requirements
of the species to be managed and relating these requirements to the special components outlined above. In this way, old growth can be more efficiently managed on a
species-specific basis.
"OLD GROWTH" SPECIES -- Meeting Their Needs
In light of the model axioms developed above, the following theorems may be
outlined that guide the use of a life history approach in regard to management of
old growth areas for wildlife.
1)
"Old growth" -- a la its components -- may be defined not by a
priori definitions and categories, but rather by the environmental
(macro- and micro-habitat) needs of the wildlife species that live
there.
2)
Wildlife species may be identified that use older age classes of
forests facultatively and obligately, based on the species' life
history patterns that involve macro-habitat components of general
seral (age-class) stages of forest stands.
3)
Such a facultative or obligate set of species may be further
represented by their needs for particular microhabitat components.
4)
"Old growth" - using species can be ordinated according to their
life history (microhabitat and niche) characteristics to show
functional relations.
The wildlife habitat relationships information file was queried using WHIMP to
extract species that are associated with old growth habitats as defined above.
Specifically, the following queries were made.
}fucrohabitat Associations
The habitat descriptors in the wildlife habitat information file was queried to
determine which wildlife species are associated with mature or over-mature stages
of coniferous vegetation types on the Six Rivers National Forest in northwestern
California.
Two classes of associations were defined:
Table 2.
facultative and obligate (Table 2).
Definitions of facultative and obligate associations of wildlife species
with mature seral stages of coniferous vegetation types.
Seral Stage Use
Association
Mature
Early
Facultative
Breeding
0 or S
and
0 or S
Feeding
0 or S
and
0 or S
or
394
Table 2 (cont'd).
Early
Mature
Association
Obligate
Breeding
0 or S
and
M, N, or?
Feeding
0 or S
and
M, N, or?
or
Use levels: 0
? = unknown.
optional, S
suboptional, M = marginal, N
no occurrence,
Many species (12 amphibians, 16 reptiles, 86 birds, and 42 mammals species) were
found to be facultatively associated with mature forests for breeding or feeding.
However a key interest for managers lies in those 14 bird and mammal species that
were identified as obligate associates. The remainder of this discussion will deal
with these less flexible species.
Microhabitat Associations and Functional Relations
Table 3 presents selected microhabitat and niche characteristics of the 14
obligate old growth species on the Six Rivers National Forest. Based on this table,
a similarity matrix (Table 4) was calculated by using S~rensen's (1948) similarity
index. Finally, Figure 1 presents a cluster analysis of the obligate old growth
species. The clustering methods followed the two-axis, Euclidean distance method
in Mueller- Dombois and Ellenberg (1974).
I.
395
Table 3.
Selected microhabitat and niche characteristics of obligate users of
mature forest stands on the Six Rivers National Forest, California.
(Information summarized from Marcot 1979).
sa
~
1. Spotted OWl
MKC MKC
JQ-100
X
"large"
300
2. Pilt."atcd
MOC MKC
15-70
X
20
100
2-20
?
10
4. Little Brown Bat MKC
n/a
X
12
5. :Lort;J-leqged
MKC
n/a
X
MKC MKC
n/a
7. Red-backai z.blse MKC MKC
X
X
X
X
X
X
X
X
X
WooCpecker
3.
BrO\'i':l
Creeper
M
M
20?
X
X
X.
none
X
X
X
X
?
none
X
X
X
X
?
n/a
512,000
?
?
n/a
X
n/a
5-15
X
24
100
X
2Q-BO
X
12
300
X
-n/a,
X
15
?
?
M)Otis
6. Wolverine
8. t'lhi tc-'headed
c
KC
i'b:x!pecker
9. Goshawk
10. Marten
K
K
K
c
n/a
12. \"uma Myotis
MKC
n/a
13. Ialg-eared
MKC
n/a
11. Vaux 's SWift
X
"small"
20
"snail"
n/a
none
12
?
?
?
X
X
X
X
X
X
X
X
X
?
?
?
X
X
X
X
X
X
X
X
X
~l,iotis
14. Northem Flyinq
2
MK
X
12
7-10
f
ffiI'll~·i~CD
X
X
X
Squirrel
l.m
~~
n~
~
g.
::s
rt'
Ill
~
-I'll
Hlrt'
!:i.....
'§.
rt'
.....
•
HI~
I
I'll
.....
0"
;;m
c:
Ll
~
~~
~B-CI
!j•rt'
i
ro
@8"
~rt'l1
tii
0.
"S"!=i
() .....
rt:J"g
I'll
g
~
0
.....
fg
I
~
lCD
,~
I
~~ [
mB'cT
I'll
~
5-
o.Q
a
~c:
I'll
~
c::
p:ffi
g·~
I
~
~I'll.....
()
roi:!
~ 8a
~ro ~~.....
()()
l
:1'
fj
~
~I
aB = use for breeding.
bF = use for· feeding.
CKuchler vegetation types: M = Mixed Evergreen Forest with Chinquapin or
Rhododendron; K = Klamath Montane Forest; C = Coast Range Montaine Forest.
(Source: A. W. Kuchler. 1977. A map of the potential natural vegetation
of California.
396
~
~
§"
c:
!J)
~
I'll
I
I
Table 4. Similarity (lower left) and diss:imilarity (upper right) matrix of the
species characteristics presented in Table 3, as calculated with 5¢rensen 's
(1948) s:imilarity imex. a:Ms and oolumns are n\lll'bered acoonli.nq to the
species' rumbers in Table 3.
1
2
1
-
2
83
3
45 35
4
67
3
4
5
6
17 55 33 30 33
-
7
44
56 56
53 60
9 10 11 12 13 14
28 33 39 33 67
65 44 42 36 23
-
8
68
45 45 38
44 42 45 68
37 37
44 41
73
47 67
5 53 33 30 26 29 43 18
30
47 47
6
5
t·
47 95
-
'.
50 30 26 33 37 38 12
5
70
6
67 64 40 47 50
7
72 77 32 67 70 67
8
67 56 56 70 74 35 48
-
47
9
61 58 59 74 67 13 60 53
-
58
55 53
63
33 65 87 71
-
52 40 44 73
29 56 47 63
53
33 44
67
f.
27
'·
1 .· . .
57 65 65 52
37 85 75
-
0 10
82 57 57
10
67
11
33 32 33 57 62 18 27 43 15 36
12
55 63
27 82 88 43 67 35 25 43 18
13
55 63
53
94 100 43 56 35 so
14
62
53
95 90 33 73
70
71
-
.
64
50 30
57 43 44
82 64 60
-
57 36 86
48 70 56 40 78
14 22
-
22
78.
...
_
397
Figure 1. Cluster analysis of old-growth obligate species on the Six Rivers
National Forest, nort.hwestem California. Analysis was made based on the
EUclidean distance metrod in Mueller-Ik:mbois and Ellenberg (1974), using
the similarity matrix data fran Table 4. Numbers on the graph refer to
species as numberoo in Table 3. * = bird species; + = mamna1 species.
100.
90
*11
80
' ...
...
~
- ....
,
,
~
""
70
60
8
*
*3
50
I
+10
40
s+
'
30
'
,,
I
I
+4
*9
\
\
\
'•
I
20 6
10
,,
*1
*2
+13
+7
I
I
~
...
--
- - "' ....
0
10
20
30
+14
\
\
'
''
40
50
60
398
70
80
90
100
...
What are the implications of this clustering of obligate old growth species
based on their microhabitat and niche characteristics? First, the uneven dispersion
of the species throughout the ordination plane suggests that some species are more
closely related functionally than others. Therefore, by inference a particular
management prescription that would provide for some obligate old growth species may
not suffice for all such species.
Second, four species are distinctly different in life histories than the remaining ten, which occupy a central cluster in the graph. Three of these one-species
"clusters" may not be considered in the development of old growth descriptions. These
are: wolverine (Gulo gulo), which ranges widely, and of which little is known about
its distribution and ecology in Six Rivers National Forest; Yuma myotis (Myotis
yumanensis), which uses buildings, caves, or mines as well as snags, as hi9ernacula
or nurseries; and Vaux's swift (Chaetura vauxi), which uses hollow trees that may be
found in other than old growth stands.
The remaining clusters include spotted owl (Strix occidentalis), goshawk
(Accipiter gentilis), and the central cluster of ten species. The large distance
between spotted owl and goshawk on the graph suggests different prescriptions for
their concomitant management, although managing for one or the other may as well
manage for other species in the central cluster.
Thus, two clusters of "old growth obligates" fall out, guided by spotted owl
and goshawk as focal species. The stand characteristics necessary for meeting these
species' needs are as follows:
CLUSTER 1 - Multistoried Unevenage Stands - these stands are of a multistoried nature
usually of pure conifer or mixed hardwood - conifer vegetative composition. The
average DBH of both live and dead (snag) trees of the overstory exceeds 20" with a
high degree of decadence including heart rot and natural occurring cavities. The
canopy is closed (>60%) helping to create a mesic microhabitat at ground level. Dead
and down material is present. Close proximity to riparian areas is essential.
Wildlife species associated with this habitat type are:
*1.
2.
3.
4.
5.
6.
7.
8.
9.
Spotted Owl
Pileated Woodpecker
Brown Creeper
Little Brown Bat
Long-legged Myotis
Red-backed Mouse
Marten
Northern Flying Squirrel
Long-eared Hyotis
*Not in Cluster II, below.
Other habitat requirements are:
Area Size:
To include the territory and/or home range of all species
listed requires contiguous habitat >300 acres in size. This
may be irregular in shape but long linear strips are unsuitable.
Location:
The area needs to be tightly adjoining or incorporating perennial
streams or other water bodies.
399
,..
CLUSTER II - Evenage Stands - these stands are of a single storied, park-like, nature
usually of pure conifer or conifer/hardwood mix. Trees are greater than 18" DBH.
The prime user of such stands, the goshawk, does not require a high degree of decadence or snags for its needs. Therefore, such stands may better be termed as an
evenage mature forest. However, if such stands are to be used by other "old growth"
obligate species decadence and snag requirements must be met. Microhabitats are
usually drier but mesic situations are optimal. Crown closure is >60%. Close proximity to riparian areas is essential.
Wildlife species associated with this habitat are:
*1.
2.
3.
4.
5.
6.
7.
8.
9.
Goshawk
Pileated Woodpecker
Brown Creeper
Little Brown Bat
Long-legged Myotis
Red-backed Mouse (?)
Marten
Long-eared Myotis
Northern Flying Squirrel
*Not in Cluster I, above.
The more specific habitat requirements are:
Area Size:
To include the territory and/or home range of all species
listed requires contiguous habitat >100 acres in size.
As with Cluster I, this may be irregular in shape but
long linear strips are unsuitable.
Location:
Loosely adjoining or incorporating perennial streams or
other water bodies.
In addition to these two clusters, a third might be established to account for more open canopy users such as
the white-headed woodpecker. It was not considered a
major management concern in this discussion.
DISCUSSION
The above clustering is based on gross, nominal data, and such assessment should
be considered with caution. Functional relationships between species inferred from
such a model could vary with more refined information on species' microhabitats and
niches.
Other ecological factors not presently included in this approach may limit the
degree of both general and site-specific predictability that resultant models may
offer. These factors include: (1) "diversity" of the habitat, including juxtaposition and configuration of different habitat patches (Marcot 1979); (2) species-area
and habitat "island" effects (Whitcomb 1977, MacClintock et al. 1977, Johnson 1975,
Diamond et al. 1976, Simberloff 1976, and others); (3) interspecific interactions,
especially competition and predation; (4) density-independent effects such as weather,
which may greatly affect wintering bird populations (Anderson and Ohmart 1976,
Fretwell 1972); (5) edge effects (Thomas et al. 1979); and (6) the timing of habitat
perturbations.
400
In general, a multi-species model and information base, using a life history and
habitat approach, must be usablf> by field personnel such as biological technicians
and by resource planners, who may or may not have greater training in computerese and
ecological theory. The system- to be used in management on a project level (i.e.,
on a day-by-day level) - must approach a cookbook formula, or at least present access
to information on a fundamentally simple level, or else it will not be used.
In conclusion, a life history approach utilizing the model axioms developed
above may be useful for assessing habitat conditions on a multiple species basis.
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D. S. Simberloff, and L. G. Abele.
1976. Island biogeography and conservation: strategy and limitations. Science
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Fretwell, S. D.
1972. Populations in a seasonal environment.
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Johnson, N.
1977. Controls of number
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~f
Princeton Univ. Press, Princeton,
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McEllin, S. M.
1979.
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547 p.
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1976. Species turnover and equilibrium island biogeography.
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Science 194:572-578.
,_.
I
I'
S~rensen,
T.
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1979. Edges. P. 48-59 in J. W. Thomas, ed. Wildlife habitats in managed forests.
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1979. Conceptual frameworks and the philosophical foundations of general living
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I. Introduc-