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Selected shrubland and grassland communities of the northern Great Plains PDF

124 Pages·1999·0.95 MB·English
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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

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