Selected shrubland and grassland communities of the northern Great Plains

124 Pages·1999·0.95 MB·English

by  Comer, Patrick,editor

SELECTED SHRUBLAND AND
GRASSLAND COMMUNITIES

OF THE NORTHERN GREAT PLAINS

Patrick Comer (editor)
Lorna Allen
Steve Cooper
Don Faber-Langendoen
George Jones

A Report to the Nebraska National Forest

February 1999
SELECTED SHRUBLAND AND
GRASSLAND COMMUNITIES
OF THE NORTHERN GREAT PLAINS

Patrick Comer (editor)
The Nature Conservancy,
Western Conservation Science Department,
2060 Broadway, Suite 230
Boulder, CO 80303

Lorna Allen
Natural Heritage Planning and Evaluation
2nd Floor, Oxbridge Place
9820 - 106 St. Edmonton AB Canada T5K 2J6

Steve Cooper
Montana Natural Heritage Program
1515 E. 6th Ave., P. O. Box 201800
Helena, MT 59620-1800

Don Faber-Langendoen
The Nature Conservancy
3467 Amber Road
Syracuse, NY 13215

George Jones
Wyoming Natural Diversity Database
1604 Grand Avenue Suite 2
Laramie, WY 82070

A Report to the Nebraska National Forest

February 1999

© The Nature Conservancy, 1999
Under 43 CFR, Part 12, Section 12.936, The Nature Conservancy (TNC) holds the copyright and maintains
ownership of data developed under this agreement. The U.S. Forest Service has the right to reproduce and
use these products for governmental purposes, provided that TNC is properly acknowledged as the author.
Acknowledgements

The Nature Conservancy and the Natural Heritage Programs of Montana and Wyoming
gratefully acknowledge the U.S. Forest Service-Nebraska National Forest for the
financial support to compile these ecological community type descriptions. We also
thank the staff ecologists of the Alberta, Colorado, Idaho, Oregon, and Washington
Natural Heritage Programs for their review of the types that occur in their respective
jurisdictions.
ii
SELECTED SHRUBLAND AND GRASSLAND COMMUNITIES
OF THE NORTHERN GREAT PLAINS

TABLE OF CONTENTS

Acknowledgements.......................................................................................... ii

Executive Summary......................................................................................... iv

Introduction...................................................................................................... 1

Ranking Methods............................................................................................. 2

Estimating Ranks............................................................................................. 2

Community Characterization Abstracts............................................................ 5

References ...................................................................................................... 7

Index to Association Descriptions.................................................................... 8

Index to Archived Association Descriptions..................................................... 9

LIST OF TABLES

Table 1. Global Ranking Definitions and Codes ............................................... 3

Table 2. Criteria used for Ranking.................................................................... 4

APPENDIX

Appendix 1. Archived association descriptions..................................................85

iii
EXECUTIVE SUMMARY

Conservation of the community/ecosystem level of biological organization is a
key component of a comprehensive approach to biodiversity conservation. The
Conservancy and its Natural Heritage Program partners have completed a
national classification of ecological communities. These types have been
preliminarily ranked in terms of their rarity, using a scale from G1 (Global 1,
critically imperiled globally due to rarity, endemism, and/or threats) to G5 (little to
no risk of global elimination). Currently, approximately 144 G1 - G3 communities
are known from the Northern Great Plains region, where a region-wide
management review is underway by the Great Plains program of the Nebraska
National Forest. A total of 52 G1 and G2, as well as eight G3 communities, were
described in a previous report (Faber-Langendoen et al. 1997).

This report serves as an addendum to the 1997 effort, providing descriptions for
an additional 28 shrubland and grassland communities ranked G3-G5. These
descriptions should allow for improved inventory of these types, thereby leading
to a future refinement of the preliminary global rank, as well as guidance on
conservation actions.

Fifteen additional shrubland and grassland types were researched and tentatively
described. This process brought to light classification issues that forced these
types to be "archived" until additional research can resolve specific classification
issues. These tentative descriptions are included as an appendix to help
document the classification process and status.

iv
INTRODUCTION

Federal, state and private agencies and organizations in the Northern Great
Plains region are concerned with the conservation of ecological communities.
Ecological communities1, which can be viewed as the biotic component of
ecosystems, are one level of biological diversity, which includes all levels of
biological organization - genes, species, communities, and ecosystems.
Conservation of the community/ecosystem level of biological organization is a
key component of a comprehensive approach to biodiversity conservation.

Ecological communities have been tracked as elements of conservation by The
Nature Conservancy (TNC) and the Natural Heritage Programs for nearly twenty
years, and exemplary occurrences of all communities (as well as those of rare
species) have helped form the basis for protection decisions throughout the
Conservancy’s history. The ecological community concept was recognized as a
critically important conservation tool because: (1) communities have inherent
value that is worth conserving (e.g., they provide important ecosystem functions);
(2) by protecting communities, many species not specifically targeted for
conservation are protected as well; and (3) communities can be used as
surrogates in areas where little is known about species patterns or ecological
processes, e.g., in tropical forests or desert areas.

The absence of a national classification of these communities has hindered our
understanding of them. To meet this need, The Nature Conservancy, in
conjunction with state Natural Heritage Programs, has drafted a comprehensive
classification of all natural and semi-natural ecological communities across the
country (Grossman et al. 1998, Schneider et al. 1997). The classification utilizes
a physiognomic-floristic ordering of existing vegetation that can be applied
internationally. The system is hierarchical, with physiognomic criteria at the
highest levels of the hierarchy and floristic criteria at the lowest levels. The
formation concept guides both the definition of the physiognomic units and
shapes the floristic units. The association and alliance concepts define the
floristic units in the context of the physiognomic units. This system brings
together the broad-scale geographic patterns of physiognomic characteristics
with that of local, site-specific, floristically-defined units. In combination, these
hierarchical levels can satisfy a broad range of objectives for use in a single
classification system.

The association is currently the lowest level of the hierarchy, as well as the basic
unit for vegetation classification, in the national classification system as it applies
to North America. The association is defined as "a plant community of definite

1Ecological communities are defined as a species assemblage that co-occur in a defined area at a
certain time and that potentially interact with one another. Typically some characteristics of the
habitat are included, either directly or indirectly, when defining ecological community types.
1
floristic composition, uniform habitat conditions, and uniform physiognomy," a
concept that has been used by most of the schools of floristic classification (see
Grossman et al. 1998). The association concept as used here applies to existing
vegetation regardless of successional status. The value of using the association
level as the most basic unit of the classification is that the full complement of
vascular plant species and ecological factors are used to help define the units.
The term community type, as used throughout this report, is synonymous with
“association.”

RANKING METHODS

Once communities are classified to the association level, they are ranked
according to their relative endangerment (Grossman et al. 1994). Ranking is
done at the association level. The ranking system is intended to help determine
conservation priorities, whereby more endangered community types are
considered higher priority (endangerment per se is, however, only one of several
factors that are considered when setting conservation priorities).

Community types are ranked on a global, national, and state scale of 1 to 5. A
rank of G1 (Global 1) indicates that a community type is critically imperiled
globally due to rarity, endemism, and/or threats, and a rank of G5 indicates little
to no risk of global elimination (see Table 1). Similar definitions apply to national
and state ranks (Grossman et al. 1994).

ESTIMATING RANKS

Although community ranking is best done when the information on the factors
listed above is available, it is often necessary to do some preliminary ranking
when the information is incomplete. This is particularly true when community
types have not been well described. Four main factors are useful in providing
some preliminary assessment of a community’s global rank: range, long term
decline across the range, the degree of site specificity, and the commonness or
rarity across the range (as ranked by state Natural Heritage Programs).

The two major criteria that determine the rank of a community type are the total
number of occurrences and the total area (acreage) of the community range-
wide. Measures of geographic range, trends in status (expanding or shrinking
range), trends in condition of remaining acreage, threats, and fragility are
secondary factors that are considered when assigning a rank (Table 2).

2
TABLE 1. GLOBAL RANKING DEFINITIONS AND CODES

G1 = Critically imperiled globally because of extreme rarity (typically five or fewer occurrences
or very few remaining acres) or because of some factor(s) making it extremely vulnerable to
extirpation.

G2 = Imperiled globally because of extreme rarity (typically six to 20 occurrences or few
remaining acres) or because of some factor(s) making it very vulnerable to extirpation.

G3 = Vulnerable; either very rare and local throughout its range or found locally (even
abundantly at some of its locations) in a restricted range (e.g. a single Great Plains state, a single
physiographic or ecoregional unit) or because of other factors making it vulnerable to extirpation
throughout it’s range.

G4 = Apparently Secure; Uncommon, but not rare (although it may be quite rare in parts of its
range, especially at the periphery). Apparently not vulnerable in most of its range.

G5 = Secure; Common, widespread, and abundant (though it may be quite rare in parts of its
range, especially at the periphery). Not vulnerable in most of its range.

GU = Unrankable; Status cannot be determined at this time.

G? = Unranked; Status has not yet been assessed.
____________________________________________________________________________

Modifiers and Rank Ranges

? A question mark added to a rank expresses an uncertainty about the rank in the range of
1 either way on the 1-5 scale.

G#G# Greater uncertainty about a rank is expressed by indicating the full range of ranks which
may be appropriate.

Q A "Q" added to a rank denotes questionable taxonomy. It modifies the degree of
imperilment and is only used in cases where the type would have a less imperiled rank if
it were not recognized as a valid name (i.e. if it were combined with a more common
type).

3
TABLE 2. CRITERIA USED FOR RANKING

The criteria for ranking are based on a set of quantitative and qualitative factors. These factors
are listed below in order of their general importance:

a. Number of Element Occurrences (EOs):
the estimated number of EOs throughout the Element's global
range;

b. Abundance:
the estimated global abundance of the Element (measured by
number of individuals, or area, or stream length covered);

c. Size of Range:
the estimated size of the Element's global range;

d. Distribution trend:
the trend in the Element's distribution over it's global
range;

e. Number of protected EOs:
the estimated number of adequately protected EOs throughout
the Element's global range;

f. Degree of threat:
the degree to which the Element is threatened globally;

g. Fragility:
the fragility or susceptibility of the Element to intrusion;

h. Other global considerations:
for example, the quality or condition of EOs that affect or
may affect endangerment status; unexplained population
fluctuations; reproductive strategies that are dependent on
specific habitat; etc.

4
COMMUNITY CHARACTERIZATION ABSTRACTS

We used the Conservancy’s standard form for describing community types
(called a Community Characterization Abstract or CCA) and compiled information
for selected fields in that form. The resulting descriptions are compiled here for
selected shrubland and grassland communities in the Northern Great Plains.
Communities selected for this project are considered characteristic, albeit rare or
uncommon, for national forest lands in the region. These descriptions should
allow for improved inventory of these types, thereby leading to a future
refinement of the preliminary global rank, as well as guidance on conservation
actions.

The descriptions included in this report were compiled by the authors from the
literature and personal field experience with these types. These descriptions
have been reviewed by others who are knowledgeable of these types. The most
current versions of these descriptions are maintained by the Conservation
Science Department of The Nature Conservancy in cooperation with state
Natural Heritage Programs.

The naming conventions for the community types (or associations) are as
follows: (1) dominant or diagnostic canopy species are listed first, (2) a “/”
separates species in different strata, whereas a “-” separates species within the
same stratum2, (3) species placed in parentheses have lower constancy (they
are less consistently found in all stands of the element), (3) an environmental
term is occasionally used as part of the name when the defining species of an
association are not well understood, and (4) the species names are ordered
loosely, generally reflecting decreasing levels of dominance, constancy, or
indicator value. A maximum of six species are currently allowed in a name,
though fewer is desirable. Plant nomenclature follows the nationally
standardized list of Kartesz (1994), with few exceptions to accommodate more
recent changes in the taxonomy or nomenclature of plant species used as
nominals.

The distribution of the community types is given by state, by ecoregion (using
Bailey et al. 1994), and by National Forest ownership. The latter information is
incomplete, and needs further review from resource managers in the Northern
Great Plains.

2A stratum is defined as a combination of life-form and height, e.g. a tall shrub
stratum is defined by the shrub life-form that is between 1 and 5 m tall.

5