Attachment-09 Plant Association Habitat Type Volume 1 Forests.pdf

Southwestern Region | FR-R3-16-04a | 2023

Plant Associations of Arizona and New Mexico, Edition 4 Volume 1: Forests

USDA Forest Service. 2023. Plant associations of Arizona and New Mexico: Volumes 1-3.

Edition 4. Forestry Report FR-R3-16-04 a,b,c available online <www.fs.usda.gov/main/r3/landmanagement/resourcemanagement>. Southwestern Region, Regional Office, Albuquerque, NM.

Cover: Jim Youtz, History Stand, Valles Caldera National Monument, Jemez Mountains

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Contents Plant Associations of Arizona and New Mexico, ................................... i

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

Preface ..................................................................................................... iii

Introduction

Format Notes for Plant Association Descriptions

Keys to Plant Associations of Southwestern Forests and Woodlands

Series Key to Forests and Woodlands

Key A: Engelmann Spruce, Subalpine Fir & Bristlecone Pine Series 21

Key B: Blue Spruce Series

Key C: White Fir Series

Key D: Douglas Fir (& Limber Pine) Series

Key E: Ponderosa Pine Series

Key F: Apache Pine and Chihuahuan Pine Series

Key G: Riparian Forests

Key H: Madrean Oak Woodlands

Key I: Pinyon Pine Series

Key J: Juniper Woodlands

Engelmann Spruce Series

PIEN/ACGL

PIEN/EREX4

PIEN/GERO2

PIEN/LETR5

PIEN/Moss ii

PIEN/PACA34

PIEN/RIMO2

PIEN/VAMY2

PIEN/VAMY2-POPUD3

Subalpine Fir Series

ABLA/CASI12

ABLA/EREX4

ABLA/JAAM

ABLA/JUCO6

ABLA/LALAL3

ABLA/MECI3

ABLA/Moss

ABLA/PASA12

ABLA/RUPA

ABLA/VAMY2

Bristlecone Pine Series

PIAR/FEAR2

PIAR/FETH

PIAR/RIMO2

Blue Spruce Series

PIPU/ARUV

PIPU/CASI12

PIPU/COSES

PIPU/EREX4

PIPU/FEAR2

PIPU/LIBO3

iii

PIPU/PACA34

White Fir Series

ABCO/ACGL

ABCO/ACGR3

ABCO/ARUV

ABCO/CASI12

ABCO/EREX4

ABCO/FEAR2

ABCO/JUMA

ABCO/LALAL3

ABCO/LETR5

ABCO/MARE11

ABCO/MUST

ABCO/QUGA

ABCO/PASA12

ABCO/RONE

ABCO/SYOR2

ABCO/VAMY2

Limber Pine Series

PIFL/ARUV

Douglas-Fir Series

PSME/ACGR3

PSME/ARUV

PSME/BRCI

PSME/FEAR2

PSME/HODU

iv

PSME/MARE11

PSME/MUMO

PSME/MUST

PSME/PHMO4

PSME/QUAR

PSME/QUGA

PSME/QUHY

PSME/QUPA4

Ponderosa Pine Series

PIPO/ACHY

PIPO/ARNO4

PIPO/ARPU5

PIPO/ARUV

PIPO/BOGR2

PIPO/FEAR2

PIPO/JUMA

PIPO/MUMO

PIPO/MUST

PIPO/MUST-FEAR2

PIPO/PUST

PIPO/QUAR

PIPO/QUEM

PIPO/QUGA

PIPO/QUGR3

PIPO/QUHY

PIPO/QUPA4

v

PIPO/QURU4

PIPO/rockland

Chihuahua Pine Series

PILE/PIFI

PILE/QUAR

PILE/QUHY

Apache Pine Series

PIEN2/MULO

PIEN2/QUHY

Riparian Forests

Scree Forests

Synonymy

Plant Reference List

Bibliography

Photos (some associations) vi

Acknowledgements This guide represents the product of the work of many people over many years to develop and improve a vegetation classification system for the forests and woodlands of Arizona and New Mexico.

This is the 4th edition of Forest and Woodland field guides. These guides were revised in 2023 by a working group of forest managers and academic specialists to include knowledge gained over the subsequent quarter century since the 3rd edition was published in 1997, and to update terminology and botanical nomenclature. This effort was organized and co-edited by James Youtz (USDA Forest Service, Regional Silviculturist), Mary Stuever (New Mexico Forestry Division, Chama District Forester), Jack Triepke (USDA Forest Service, Regional Ecologist), and Bruce Buttrey (USDA Forest Service, retired silviculturist). Esteban Muldavin (University of New Mexico, Natural Heritage New Mexico Division Leader and Ecology Coordinator), Mark Nabel (USDA Forest Service, Silviculturist), and Shawn Martin (USDA Forest Service, Forest Silviculturist) provided input and review. Mariah Stover and Jordan Felt (USDA Forest Service, Terrestrial Ecological Unit Inventory) provided significant assistance with review and editing of plant name updates, and synonymic references with names used in the 3rd edition. Monique Duke and Olivia Diaz of the Southwestern Region provided help with formatting and final editing. This working group also developed Volume 3 as a companion publication to these field guides titled “Ecological Response Units of the Southwestern United States”, which references current science, classification linkages, plant association groupings, and tools for management and project planning and implementation.

The 3rd edition was compiled and edited by Mary Stuever and John Hayden (1996, revised 1997). It is primarily based on three regional guidebooks compiled in the mid 1980’s by editors/authors Will Moir and Milo Larson, with assistance from Dick Bassett, Reggie Fletcher, Esteban Muldavin, Suraj Ahuja, and Maurice Williams. Information for the third edition update was derived from many sources including comments from reviewers-- primarily natural resource professionals who utilize habitat typing information, information from the Fire Effects Information System-- a database maintained by the U.S. Forest vii

Service’s Intermountain Fire Sciences Laboratory in Missoula, Montana, and a large body of literature on fire history generated by researchers associated with the University of Arizona’s Laboratory of Tree Ring Research in Tucson, Arizona, and numerous other research publications. Comments on the third edition plant association descriptions were provided by: Norm Ambos, Jack Carpenter, Francisco Escobedo, Will Moir, Don Moniak, Wayne Robbie, Gregg Sant, John Shafer, and Rita Suminski. Comments on the regional key were provided by: Norm Ambos, Kim Paul, John Shafer, and Charlie Wicklund. Thanks also to the 1997 Habitat Typing Workshop participants who provided additional field review.

The 2nd edition was a three-volume set of Forest and Woodland Habitat Types for three geographic regions within the Southwest (Arizona South of the Mogollon Rim and Southwestern New Mexico -yellow cover, Southern New Mexico and Central Arizona north of the Mogollon Rim -brown cover, and Northern New Mexico and Northern Arizona -green cover) compiled by Moir & Larson in 1987, based on the handouts described below and input from 8 workshops in the mid 1980’s.

The 1st edition was the handouts synthesized from the research literature provided during the first round of habitat typing training in this region (taught by Will Moir & Milo Larson). Research to describe habitat types in Arizona and New Mexico was conducted by Billy G.

Alexander, Jr., Fairley J. Barnes, Robert L. DeVelice, E. Lee Fitzhugh, Richard E. Francis, Jess P. Hanks, Sharon R. Hanks, Kathryn Kennedy, Earl F. Layser, John A. Ludwig, Will Moir, Esteban Muldavin, Frank Ronco, Jr., Gilbert H. Schubert and Alan S. White. In addition, plant association descriptions from numerous authors and data sources were adapted by Moir and Larson to develop the woodland descriptions.

viii

Preface Habitat typing or plant association concepts provide natural resource professionals a way to communicate with peers about specific forest ecology observations without assigning them to broad areas where they may not apply. This ability to separate knowledge by more specific ecosystems allows for rapidly increasing the collective understanding of a wide diversity of forest ecosystems. Habitat typing (referring to forest stands by their plant associations) provides a language for the transmission of ideas and observations and has greatly enhanced our ability to discuss and understand the role of forest vegetation management in many specific situations.

Although foresters (particularly silviculturists) originally pioneered the use of habitat types in this region, this tool is now employed by many types of natural resource professionals, including fuels managers, vegetation ecologists, range conservationists, wildlife biologists, engineers, soil scientists, landscape architects, etc. Every year more natural resource professionals realize the value of using this classifi-cation system to provide site specific guidelines based on past experiences in similar plant associations for predicting future responses to management activities.

The management implementation guidelines associated with this classification system are dynamic. As more experience is assembled by many professionals and researchers working in the field, our overall un-derstanding of each plant association increases. When Will Moir compiled the regional habitat typing guides in 1987, he stated that this was just the beginning. As a working professional in the field, it is our responsibility, as well as our colleagues, to collect the information we glean from our experiences to enhance these guides. All users of this guide are challenged to continue to document observations and experiences for Edition 5. Comments on this guide should be sent to the Regional Forester, USFS Southwestern Region, 333 Broadway Blvd.

SE, Albuquerque, New Mexico 87102

Introduction Forests and woodlands are naturally complex and diverse ecosystems and, therefore, difficult to thoroughly understand or predict changes which may result from management activities or natural vegetation development over time. This classification of forests and woodlands allows us to make general statements about observations in one site and apply the knowledge learned to other sites of the same plant association.

The recognition of plant associations (habitat types) provides one system of classification, based on potential natural vegetation. The core classification level are the plant associations which are nested in sub-series and series levels. Occasionally plant associations are subdivided into phases, particularly when there is a wide geographic distribution.

Plant associations are closely related to other classifications. For example, the National Vegetation Classification System is similar, and share the plant community as the foundational level, but is based on current vegetation, rather than potential natural vegetation. These plant associations are cross walked to the National Vegetation Classification System hierarchy. Since plant associations are quite specific to micro-site changes, mapping plant associations is rarely practical beyond the local area scale. The Terrestrial Ecological Unit Inventory (formerly Terrestrial Ecosystem Survey) references plant associations (Winthers et al. 2005, USFS 1986) but is usually associated with the subseries level of potential natural vegetation classification, which is often more practical for mapping. Ecological Response Units (ERUs) are coarser than Terrestrial Ecological Units (TEUs) and reflect broad ecosystem types of similar site potential and fire regime and represent groupings of either TEUs or plant associations. The ERUs are most useful for landscape-scale analysis and management purposes. The finer scale of habitat types (associations) best informs development and implementation of site-specific management treatments.

These habitat type classifications have been in use in Arizona and New Mexico for over three decades; during this time, managers have observed that similar responses to disturbances and vegetation development can be expected on different site locations sharing the same or closely associated habitat type classifications. As a result, this classification system has become a valuable and trusted tool for management planning and implementation of vegetation treatments in forests and woodlands in the Southwestern United States.

This publication describes the known plant associations for forests and woodlands in Arizona and New Mexico. Many sources were utilized to compile these descriptions, but the primary sources for this edition are updates to edition 3, which was derived from three regional habitat typing guides developed by the Forest Service in 1986 and 1987. This book is divided into three parts. The introductory material will provide background information on interpreting the descriptions, recent nomenclature changes for plants, and a key to the plant associations.

The second and largest section is the descriptions for each plant association. The appendices include a bibliography, a synonymy list of plant name changes, and a list of plants mentioned in the descriptions.

A companion document titled “Plant Associations of Arizona and New Mexico Volume 3: Potential Vegetation, Ecological Linkages, and Tools for Management Planning” has been developed as a reference to document ecological linkages to other classification systems, historical conditions, and inferences for management planning.

Plant associations, or habitat types, have been used for classification throughout the west. The concept was first developed in western Washington by R. F. Daubenmire. Habitat types for Arizona and New Mexico were described by many researchers, primarily in the late 1970’s and through the mid 1980’s. Plant associations are still being recognized and described today, and conceivably there will be stands that will not fit any of the descriptions in this guidebook.

Although this classification system of plant association descriptions is based on climax or very late successional stand conditions, frequently the stands being classified are often in early or mid-successional stages.

Additionally, one should recognize that there are often different climax conditions for a plant association which are influenced by the stand’s history. The fire exclusion disclimax that many of the plant associations are based on, may not be the historic reference condition, or the desired future condition that the manager is hoping to develop or maintain. It is helpful to think of the plant association as a “name” representing development potential, rather than a goal for stand conditions.

Another important guideline when matching these descriptions to specific forest or woodland stands is to expect variation. The descriptions are based on the “typic” expression of the associations, although “ecotones” between associations are frequently encountered in the field. Descriptions also cover broad geographic areas, and usually all the plants listed will not actually occur in any given stand. Some habitat types occur on limited or singular soil types, while others occur on a variety of soils; therefore, expressing subtle differences in plant composition. Other factors such as variances in elevation, precipitation, and management history can influence expressed plant composition.

The information presented may not be consistent from association to association. For example, stating that one association has high aesthetic value does not imply that others do not. Rather it implies that literature or comments on aesthetic value were not available for associations that omit this information.

Notes about Plants and Plant Names The names of plants can be confounding. Common names tend to vary by geography and culture and are often applied to more than one plant.

Scientific names, though follow specific naming rules, can change for individual plants based on better information and understanding of the species. Since the publishing of Regional Forest and Woodland Habitat Type (Plant Association) guides in 1986 and 1987, and the Plant Associations of Arizona and New Mexico (Volumes 1 & 2) in 1997, many of the scientific names of the plants have since changed.

Additionally, new information is emerging on hybridization and evolution, changing our understanding of various species.

The PLANTS database was used during the summer of 2021 as a source for genus and species names, codes, and standardized common names presented here. It is maintained by the USDA Natural Resources Conservation Service and presently considered the appropriate authority recording and abbreviating scientific and common plant names. A synonymy section is included in each Plant Association description to familiarize the user with name changes however these lists are not comprehensive.

Here are some important thoughts on plants and plant names within the context of Southwestern Plant Associations:

• The editors are endorsing the use of PLANTS database for this document to avoid confusion but are not discouraging the use of additional and geographically important common names, nor the use of different naming rules (such as no possessive punctuation for plant names). Users are encouraged to know many names for plants including indigenous and local names where appropriate.

• The scientific name for subalpine fir used in the 1997 version of the guides was Abies bifolia. The correct name is now back to the original Abies lasiocarpa. Although corkbark fir is the more dominant variety of subalpine fir in the Southwest, the PLANTS database only uses the common name ‘corkbark fir’ when the variety is identified. In keeping with this conformity, we are using the common name “subalpine fir’ because the research data list the tree as Abies lasiocarpa.

• Although the PLANTS database tends to follow conventions more common in naming animals by giving a possessive voice to a proper name, it was decided to follow this database for consistency, so “Gambel oak” would become “Gambel’s oak”; Thurber fescue – Thurber’s fescue, and so forth. However, the PLANTS database is not consistent on this.

• The single-needle pinyon pine in central Arizona was referred to as Pinus fallax in Edition 3 of the guides to avoid confusing plant associations in Arizona with plant associations in Utah. With efforts to develop the National Vegetation Classification System, the name has been corrected to Pinus monophyla, and the NVC will insure having unique nomenclature for each plant community. Similarly, the common name has changed from Arizona pinyon to singleleaf pinyon as standardized by the NRCS.

• Kristin Waring, NAU School of Forestry provides the following information: “Southwestern white pine (Pinus strobiformis) and limber pine (Pinus flexilis) are known to hybridize readily across Region 3. While populations or individual trees of either species may exist, it more likely to encounter hybrids (Menon et al. 2018). The proportion of each parent species varies systematically from south to north across a latitudinal gradient, with pure P. strobiformis found near the Mexican border, and pure P. flexilis found in trees in southwestern Colorado (Menon et al. 2018). In between, increasing amounts of P. flexilis are found in trees moving from south to north, but generally less than 50% in Region 3 (Menon et al. 2018).

Hybridization may provide advantages in the future as both species are further challenged by climate change and white pine blister rust (Menon et al. 2020, 2021).” For the purposes of this plant association classification, P. strobiformis refers to trees in the southern areas;

while P. flexilis refers to the trees in the northern areas. Use best judgement based on associated plants to determine the appropriate plant association for areas in between.

• Several woodland plant associations reference Yucca schottii.

PLANTS Database recognizes Yucca X schottii and Yucca madrensis as formerly being Yucca schottii. In this guide, Y. schottii was systematically changed to Y. madrensis. Bob Sivinski offers this:

Yuccas are taxonomically problematic. The species often grade into one another over large geographic regions and the variations are endless. Y. madrensis extends across the Sierra Madre in Chihuahua/Sonora up to the Chiricahua and Peloncino Mts in the US. There is quite a bit of variation in stature, leaf width and color, and solitary vs colonial growth form including spindly understory shade forms in Mexico that haven’t been seen in the US. A recommendation is to call it all Y. madrensis. To retain the distinctions of the variations, the solitary, caulesent plants with non-filamentous leaf margins on bluish leaves are Y. madrensis and the plants with colonial bunches of stems are Y. x schottii.

• The PLANTS Database lists gray oak (Quercus grisea) and Arizona white oak (Q. arizonica) as different species. Landrum (1994) has combined both as Q. grisea, but for the purposes of this plant association classification system, they are treated as separate species.

• There were 39 species with name changes from the 1986-87 edition to the 1997 edition. There are now approximately ~135 species with name changes from the 1986-87 and 1997 editions to this edition.

Some changes represent going back and forth between the same two names, while many are novel changes. Spelling corrections and adding possessive name punctuation are generally not listed in the synonymy section. A list highlighting some of key indicator and important plant name changes in this guide can be found on page 27 A more complete list can be found in Appendix A.

Some Essential Terms and Concepts Vegetation Coverage terms refer to the area covered by the canopy of the plant.

Scarce - less than 1% cover, versus common - greater than 1% cover.

Poorly represented - less than 5% cover, versus well-represented -greater than 5% cover.

Abundant - greater than 25% cover.

Luxuriant - greater than 50% cover.

Absent - cannot be found in the stand, versus present - can be found in the stand.

Accidental - individuals infrequent, occasional, or limited to special microsites.

Dominant - Density or cover is as great as, or greater than, any other species of the same life form (two or more species can be dominant, i.e.

codominant).

Regeneration - understory trees as established seedlings, saplings, or small poles (DBH <10 inches).

Life History Traits - indication of trees’ role (major or minor component) at most dominant successional stage (seral or climax)

Seral - early and mid-stages of succession Climax - late and advanced stages of succession

Other related documents Plant Associations of Arizona and New Mexico, Volume 1: Forests.

Plant Associations of Arizona and New Mexico, Volume 2: Woodlands.

Plant Associations of Arizona and New Mexico, Volume 3: Ecological Response Units of the Southwestern United States

Plant Associations and Future Climate The Forest Service acknowledges that seasonal change, warming, and increased aridity (IPCC 2014) will affect both site potential and disturbance regimes, and that plant associations based on potential natural vegetation form a reasonable baseline from which to assess past variation ((Barrett et al. 2010, Comer et al. 2003)), current departure and loss of ecological integrity (Keane et al. 2018), the future range of variation (Somodi et al. 2012), and to consider adaptation options. Plant associations based on potential natural vegetation will remain a valuable concept for understanding basic land capability. The Southwestern Region and partners have developed vulnerability assessments (e.g., Hand et al. 2018) and tools to address changing climate and fire regimes (e.g., Bagne et al. 2011, Friggens et al. 2019). The Forest Service also understands that shifts in site potential from climate forcing may already be ongoing and should be addressed in an adaptation strategy (Muldavin and Triepke 2019, Triepke et al. 2019).

Format Notes for Plant Association Descriptions Explanations of each of the subheadings found in the plant association descriptions follow.

Plant Association Identification Names for each plant association are found at the beginning of each description. Each association is usually named for the most shade tolerant tree successfully regenerating, and for an understory species (shrub or herb) which is most diagnostic of the site. The plant association abbreviation code is found at the top of the page. Plants that occur in the US are assigned this code by the Natural Resources Conservation Service Plants Database. The code is usually the first two letters of the genus and the first two letters of the species. An additional letter may be added to clarify a variety or subspecies. Where different species have the same codes, numbers are assigned to provide a unique abbreviation for each species. The plant association code includes the most shade tolerant tree (NOT the most common tree) and an indicator plant that is most unique to the plant community. Photos of some associations are included in the final section of the handbook.

The common name of the plant association is also in bold at the top, followed by the scientific name. If the plant association was known by a different name in the regional guides mentioned above, this name is also included in the heading as “formerly ....”. Often when plant associations, habitat types, or community types are referred to in publications, the name of the plant community is followed by an abbreviation to indicate the type. We have only included these initials if the plant community is not a habitat type or plant association. For example, PIPO/ARPU c.t. refers to the ponderosa pine/Manzanita community type. If there are no initials, the description of the plant association refers to a reference condition considered to be late successional under fire exclusion within the state-and-transition model for that plant association.

The vegetation code is used by the U.S. Forest Service and other agencies and organizations for data storage. The first digit recognizes the form, the next two digits delineate the series, the following two digits are for the specific plant association (habitat type), and the last digit, if present, is a phase designator. For example, the code for ponderosa pine/Arizona fescue, Gambel oak phase is 0 11 09 3. The first ‘0’ designates a forest, the ‘11’ ponderosa pine, the ‘09’ identifies the association, and the ‘3’ is the phase indicator.

If the plant association has been labeled by other researchers using dif-ferent species to name the type, these alternate names have been included in the synonym field, along with a reference to the publication in which these alternate names appear.

Ecological Response Unit Each association falls within an Ecological Response Unit (ERU), a general ecosystem type representing both site potential and the characteristic disturbance regime that is similar thematically to other landscape stratifications including LANDFIRE Biophysical Settings and Ecological Systems (Barrett et al. 2010, Comer et al. 2003). The ERU framework for the Southwestern Region of the Forest Service represents all major ecosystem types of the region including over 50 terrestrial types and subclasses and over 30 riparian types and subclasses. On Forest Service lands, each ERU is a technical grouping of Terretrial Ecological Units (Winthers et al. 2005) that are similar in site potential (PNV subseries), ecosystem dynamics and disturbance, and that have similar plant species dominants. Since the ERU construct is one of both site potential and disturbance, two sites with similar site potential but significantly different disturbance regimes would be classified and mapped as different ERUs. By this approach it is possible for a given association to occur within more than one ERU depending on the disparity in historic disturbance regime and/or phase; however, in this guide the primary ERU, the ERU of greatest frequency, is identified by name and code for each association at the beginning of the description and is described in detail in the ERU companion guide.

Determining the corresponding ERU for a given association is an interpretation, sometimes resulting in the least objectionable alternative, and subject to reinterpretation with new information and subsequent revisions to this guide or to the ERU framework.

National Vegetation Classification Group Within this guide each association has a corresponding Group class within the National Vegetation Classification (NVC) (Jennings et al.

2009). Groups are a mid-level unit of the NVC, each Group falling within a Macrogroup, and each containing one or more Alliances that, in turn, contain one or more NVC Associations. An example of the classification hierarchy using the NVC Association Ponderosa Pine / Blue Grama Woodland:

Formation Class -Forest & Woodland Formation Subclass - Temperate & Boreal Forest & Woodland

Formation - Cool Temperate Forest & Woodland Division - Rocky Mtn Forest & Woodland

Macrogroup - Southern Rocky Mtn Lower Montane Forest

Group - Southern Rocky Mtn Ponderosa Pine Open Woodland

Alliance - Southern Rocky Mtn Ponderosa Pine / Grass Open Woodland

Association – Ponderosa Pine / Blue Grama Woodland

For the most part, the plant associations of this guide have already been adopted into the NVC as late seral forested expressions and sometimes with nearly identical naming, as with the Ponderosa Pine / Blue Grama Woodland Association and the original Pinus ponderosa/Bouteloua gracilis habitat type (Hanks et al. 1983). Though only the principal NVC Group is listed with each plant association description, most associations can be represented by more than one NVC Group since potential vegetation types represent all seral conditions and cover types (Arno et al. 1985). For example, the Pinus ponderosa/Quercus gambelii habitat type (Alexander et al. 1984a) can be represented by the NVC Southern Rocky Mountain Ponderosa Pine Forest & Woodland Group (tree-dominated), the Southern Rocky Mountain Gambel Oak - Mixed Montane Shrubland Group (shrub-dominated), or the Southern Rocky Mountain Montane-Subalpine Grassland Group (herb-dominated). But for purposes here the Group of greatest frequency is the one listed at the beginning of each association.

Key criteria The key criteria section is a brief snapshot description of the plant association highlighting features that separate it from similar plant associations. This usually includes a discussion of the overstory—as well as what is absent from the overstory and may also provide limited geographical information.

Structure This discussion includes information on tree site indices, forage rating values, and other structure and productivity information when available.

In general, tree site index information is sketchy and not very reliable.

There is probably a wide variance in site indices within most associations.

Often a stockability factor is given. Stockability is an estimate of the stocking potential of a given site; a fully stocked site has factor of 1.0.

For example, a factor of 0.5 indicates that the site is capable of supporting only 50 percent of timber species of “normal” stocking as indicated in yield tables. The stockability factors are subjectively assigned to each association, and not necessarily determined from extensive data.

Location This section gives geographical information on several scales, but specific to Arizona and New Mexico. General ranges, often including place names, are provided, as well as specific site information such as elevation, slope, aspect and/or soil characteristics. Elevations are given in feet and meters and are determined from research and observational data. Expect these elevational ranges to be narrower than what may actually be encountered throughout the region. Where determined, precipitation and soil temperature data are also included.

Adjacent habitat types Landscape patterns of plant associations are discussed here.

Also see This section provides suggested references to check to help clarify this plant association identification, or if the description isn’t quite right, to find a better description.

Important and key plants from research plots Plant associations are classified by collecting all of the vegetation information in a specific plot design including species and coverage. A cluster analysis on the data suggests similar plots which is then field check by the researchers to verify similarities. The plants that are listed for this section are organized by trees, shrubs, herbs, and cryptogams.

Herbs includes both graminoids (grasses and grass-like plants) and forbs.

Trees & life history traits For each phase or geographic region, trees are listed by common name (scientific name) and a letter code indicating the general role that species assumes in the plant association. Where capital letters are utilized, the tree species has the potential to be dominant for that successional state. Conversely, for small letters the species is generally a minor part of of that successional state. Capital C stands for major climax, a species which is clearly regenerating successfully and surviving to maturity in late and advanced stages of succession. The species is also present in all (or nearly all) stands. Capital S stands for major seral tree, a species which is clearly regenerating successfully and surviving to maturity only in early and mid-stages of succession, although mature trees often persist as overstory in later stages. The species is also present or potential in all (or nearly all) stands. Small c stands for minor climax, and include species that meet the major climax definition, except they may not be present in all stands. Small s stands for minor seral and includes species that meet the major seral definition, except the species may not occur (now or as potential) in all (or most) stands. Trees that are accidental are referred to in the “Key Criteria” section. Only those trees referred to in the research are listed here. Trees not listed or mentioned generally do not occur in the association (however, see notes on aspen in PIPO/MUMO).

Shrubs and herbs plant list Shrubs and herbs are listed in separate categories. For each category, the typical canopy coverage is given using defined terminology such as common (>1%), scarce (<1%), well (>5%) or poorly (<5%) represented, abundant (>25%), and luxuriant (>50%). Species that are diagnostic to the association are in bold face and indicated with an asterisk (*). Spe-cies are ordered according to overall importance throughout the range of the plant association, but the occurence of individual species will vary geographically. Usually, individual stands will not include all the species in an association species list.

Cryptogams This section includes notes on mosses and lichens which have been associated with the plant association. If none are listed, this may mean we have no information on cryptogams for that plant association, rather than implying that there are no cryptogams in the association.

Brief plant ID notes The brief plant identification notes are intended to serve as reminders to key characteristics of indicator plants, and not to be used as a single source for plant identification. A synonymy list includes any recent scientific names and a few other common names for plants mentioned in the description.

Terrestrial Ecological Unit attributes Three values indicating the typical TES climate class are given. The first value is the life zone class. These codes are:

4 (woodlands) 5 (ponderosa pine forest) 6 (mixed conifer forest) 7 (subalpine forest)

The second value indicates a temperature and moisture phase within each life zone class. These codes are:

-1 = warm-dry;

0 = typical or modal;

+1 = cool-moist.

The third code indicates the climate class which consists of two parts.

The first two words refer to the season in which the majority of the precipitation on the site occurs. High sun refers to a summer precipitation-dominated climate, and low sun refers to an area that is winter precipitation-dominated. The second part of the climate class refers to temperature regime, either mild (including warm-temperate and subtropical) or cold (cold temperate). Therefore, the four possible climate class codes are Low Sun Cold (LSC), Low Sun Mild (LSM), High Sun Cold (HSC), and High Sun Mild (HSM).

Phases This section includes information on variations between phases and any specific comments related to a phase.

Fire ecology Fire ecology information may include known fire regime information such as fire return intervals, severity, etc., or specific plant responses to fire. When possible, we have tried to distinguish between presettlement and current fire conditions. We have tried to include information on fire behavior specific to the habitat type, observations on successional trends following fire, and information on the use of and responses to prescribed fire.

Reforestation This section includes information on natural regeneration, artificial regeneration, and timber harvesting activities. The focus of this discussion is on the regeneration of timber species.

Revegetation considerations This discussion refers to site responses following disturbances of any site component but focuses on early seral species.

Comments This discussion may include specific wildlife, recreation, or range com-ments, potential opportunities for firewood or other resource products, ecological observations on successional pathways not already mentioned, insect or disease concerns associated with a plant association, or any other comments.

Reference(s) The author and date of documents used to develop the description of this plant association are listed here. For full citations, refer to the bibliography.

Photos of some associations are included in the final section of the handbook.

Keys to Plant Associations of Southwestern Forests and Woodlands These keys have been developed to help identify plant associations for forests and woodlands for the Southwestern Region (Arizona and New Mexico). These keys (and the accompanying plant association descriptions) do not cover non-forested environments, including alpine tundra, chaparral, shrublands, grasslands, meadows, etc. In addition, this key does not provide information on mountainous riparian areas at the plant association level, although some series are addressed, nor are lower elevation forests along rivers (i.e., bosque) included. This key primarily has been derived from 3 keys (USFS 1987a, 1987b, 1986) that cover 3 geographic regions of this area.

Using the Keys These keys work best in stands where disturbances have been minimal.

Stands in early to mid-seral stages of succession generally will not key directly to their association. In young or recently disturbed stands, the association must be inferred from site factors, indicator species, tree successional relationships or from known successional stages.

Fortunately, later successional (near climax) conditions can usually be inferred from the most shade tolerant tree species that is successfully reproducing. When trying to key any early seral stand, look for patterns on the local landscape. Find the most mature stand on a similar site in the local landscape and apply the keys to that stand.

To use the key, determine the combination of potential climax tree species by noting especially the proportions of trees in young, regenerating sizes. This helps determine the series, which is generally based on the most shade tolerant species regenerating in the stand.

Always start in the first key, the Series Key to Forests and Woodlands. There are exceptions to every rule which guides this classification system, and only by using the keys can the proper series be determined. Keys A through J are the keys for each series or group of similar series. In these keys, it is necessary to identify certain understory shrubs and herbs (indicator species) and to note their canopy coverage.

Coverage classes are defined in the terms below.

Proceed through the key making careful observations required at each decision couplet. When the decision of which part of the couplet to follow is difficult, try both options. Validate the determination against the plant association description which best fits your observations.

Check your observations if descriptions do not agree. No stand will fit the description perfectly.

When a site has been disturbed, the keys may not work at that site. To identify the plant association, find a less disturbed site with similar land position, soils, aspect, etc. to key out. Compare the answer with clues within the stand you are working with. Also look for historic documentation if it exists.

If the stand does not key out, consider if the type is unique and has not yet been described. In this case, notify the Regional Silviculturist or Vegetation Ecologist at the Southwest Region Office (USFS).

Essential Terms

Scarce - less than 1% cover, versus common - greater than 1% cover.

Poorly represented - less than 5% cover, versus well represented -greater than 5% cover.

Abundant - greater than 25% cover.

Luxuriant - greater than 50% cover.

Absent - cannot be found in the stand, versus present - can be found in the stand.

Accidental - individuals infrequent, occasional, or limited to special microsites.

Dominant - Density or cover is as great as, or greater than, any other species of the same lifeform (two or more species can be dominant, i.e. codominant).

Regeneration - understory trees as established seedlings, saplings, or small poles (DBH <10 inches).

Important Name Changes Some of the terminology and many of the plant names have changed since the regional keys were published in the mid-1980’s and the mid

1990’s. Here is a short list of some of those changes you may encounter in these keys (See Appendix A for a long list).

Name changes for key indicator plants:

Trees:

subalpine fir (Abies lasiocarpa = A. arizonica = A. bifolia) aka corkbark fir Arizona cypress (Hesperocyparis arizonica = Cupressus arizonica) redberry juniper (Juniperus coahuilensis = J. erythrocarpa var.

coahulensis) border pinyon (Pinus discolor = Pinus cembroides) = Mexican pinyon singleleaf pinyon (Pinus monophylla = Pinus fallax = P.

californiarum) aka Arizona pinyon

Shrubs:

black sagebrush (Artemisia nova) = low sagebrush (A. arbuscula var. nova) alderleaf mountain mahogany (Cercocarpus montanus) = true mountain mahoganyrubber rabbitbrush (Ericameria nauseosa = Chrysothamnus nauseosus) creeping barberry (Mahonia repens = Berberis repens) aka Oregongrape wavyleaf oak (Quercus X pauciloba = Q. undulata) Stansbury cliffrose (Purshia stansburiana = Cowania stansburiana = C. mexicana)

Graminoids:

Indian ricegrass (Achnatherum hymenoides = Oryzopsis hymenoides) dryspike sedge (Carex siccata = C. foenea) = fony sedge beardless wildrye (Leymus triticoides = Elymus triticoides) screwleaf muhly (Muhlenbergia straminea = M. virescens) tobosagrass (Pleuraphis mutica = Hilaria mutica)

Forbs and other herbs:

sprucefir fleabane (Erigeron eximius) = forest fleabane (E.

superbus)

Nevada pea (Lathyrus lanszwertii var leucanthus = L. lanszwertii var arizonica = L. arizonica) aka Arizona peavine bittercress ragwort (Packera cardamine = Senecio cardamine) = cardamine groundsel burnet ragwort (Packera sanguisorboides = Senecio sanguisorboides)

Series Key to Forests and Woodlands

1. Streamside environments with riparian obligate trees such as cottonwood (Populus fremontii, P. deltoides, or P. angustifolia), alder (Alnus tenuifolia or A. oblongifolia), willow (Salix spp.), sycamore (Platanus wrightii), or boxelder (Acer negundo). (Note: Arizona walnut (Juglans major) does not qualify as a riparian obligate tree since it also occurs in dry or intermittent drainages)...Key G, Riparian Forests, page 34.

1. Other environments without riparian obligate plants

2. Dominant (density or cover is as great as, or greater than, any other species of the same lifeform) trees species regenerating include subalpine fir (Abies lasiocarpa), Engelmann spruce (Picea engelmannii), bristlecone pine (Pinus aristata), blue spruce (Picea pungens), white fir (Abies concolor), limber pine (Pinus flexilis), Douglas-fir (Pseudotsuga menziesii), ponderosa pine (Pinus ponderosa), Apache pine (Pinus engelmannii), or Chihuahua pine (Pinus leiophylla)

2. Dominant trees species regenerating include species of pinyon pine (Pinus edulis, P. discolor, or P. fallax), juniper (Juniperus monosperma, J. deppeana, J. osteosperma, or J. coahuilensis), Arizona cypress (Cupressus arizonica), or oak (Quercus grisea, Q. oblongifolia, Q.

emoryii, Q. hypoleucoides, or Q. arizonica)

3. Forests of talus or debris slopes with fragmental soils (cobbles or stones >90% of soil volume)....Scree Forests, Volume 1, page 427.

3. Forests of other environments

4. Subalpine fir (Abies lasiocarpa) and/or Engelmann spruce (Picea engelmannii) and/or bristlecone pine (Pinus aristata) is dominant or reproducing successfully, clearly not accidental....Key A: Engelmann Spruce, Subalpine Fir & Bristlecone Pine Series, page 21.

4. Subalpine fir (Abies lasiocarpa) and/or Engelmann spruce (Picea engelmannii) and/or bristlecone pine (Pinus aristata) is absent or accidental (or present in seral stages only)

5. Blue spruce (Picea pungens), white fir (Abies concolor), limber pine (Pinus flexilis), or Douglas-fir (Pseudotsuga menziesii) dominant or reproducing successfully, clearly not accidental

5. Blue spruce (Picea pungens), white fir (Abies concolor), limber pine (Pinus flexilis), or Douglas-fir (Pseudotsuga menziesii) absent or accidental

6. Blue spruce is common, clearly not accidental...Key B: Blue Spruce Series, page 25.

6. Blue spruce is absent or accidental

7. White fir is dominant or reproducing successfully, clearly not accidental....Key C: White Fir Series, page 26.

7. White fir is absent or accidental....Key D: Douglas Fir & Limber Pine Series, page 28.

8. Ponderosa pine dominant without presence of additional Madrean pines.... Key E: Ponderosa Pine Series, page 30.

8. Madrean pines including Apache pine (Pinus engelmannii), Chihuahuan pine (Pinus leiophylla), and Arizona pine (Pinus arizonica) are common, clearly not accidental, location SE Arizona or SW New Mexico...Key F: Apache Pine and Chihuahuan Pine Series, page 33.

9. Arizona cypress (Cupressus arizonica) present, not accidental...13

9. Arizona cypress (Cupressus arizonica) absent or accidental ... 10

10. Woodlands of slopes >40% and rocky or bouldery soils with much rock outcrop or bare rock soils...Scarp Woodland, Vol. 2 page 249.

10. Woodlands of slopes <40% or soils not as described above...11

11. Evergreen oaks (Quercus grisea, Q. oblongifolia, Q. emoryii, Q.

hypoleucoides, Q. arizonica) are well represented (>5% cover) to abundant (>25% cover) in the tallest stratum, geographic locations in southern Arizona or southern New Mexico....Key H: Madrean Oak Woodlands, page 35.

11. Evergreen oaks are poorly-represented in the tallest stratum

12. Pinyon pine (Pinus edulis, P. discolor, or P. fallax) is dominant or reproducing successfully, clearly not accidental ....Key I: Pinyon Pine Series, page 37.

12. Pinyon pine (Pinus edulis, P. discolor, or P. fallax) is absent or accidental, juniper (Juniperus monosperma, J. deppeana, J. osteosperma,

or. coahuilensis) is dominant and reproducing successfully.....Key J:

Juniper Woodlands, page 42.

13. Silverleaf oak (Quercus hypoleucoides) common .......HEAR22/QUHY, Vol. 2, page 45.

13. Silverleaf oak (Quercus hypoleucoides) absent or accidental .....HEAR22/QUTU2, Vol. 2, page 49.

Key A: Engelmann Spruce, Subalpine Fir & Bristlecone Pine Series (All page numbers refer to Volume 1: Forests)

1. Bristlecone pine (Pinus aristata) is dominant at climax (northern NM or northern AZ)

1. Bristlecone pine (Pinus aristata) is absent or not dominant at climax

2. Currants (Ribes) common, grasses poorly represented..PIAR/RIMO2, page 140.

2. Currants (Ribes) scarce, grasses usually well represented...3

3. Thurber’s fescue (Festuca thurberi) common....PIAR/FETH, page 135.

3. Thurber’s fescue (Festuca thurberi) absent or scarce....PIAR/FEAR2, page 131.

4. Herbs and shrubs are scarce

4. Herbs and shrubs are at least common

5. Subalpine fir (Abies lasiocarpa) is codominant, reproducing successfully.... ABLA/moss, page 111.

5. Subalpine fir (Abies lasiocarpa) is absent, or not reproducing successfully... PIEN/moss, page 63.

6. Saturated soils.....ABLA/MECI3, page 107.

6. Soils otherwise

7. Beardless wildrye (Leymus triticoides) is common (known from Capitan Mtns, southern NM).....PIEN/LETR5, page 59.

7. Beardless wildrye (Leymus triticoides) is scarce or absent, or geographic location is other

8. Regeneration of subalpine fir (Abies lasiocarpa ) is absent, accidental, or minor

8. Regeneration of subalpine fir (Abies lasiocarpa ) is present, clearly not accidental or minor

9. Nearly pure stands of Engelmann spruce (Picea engelmannii) (bristlecone pine (Pinus aristata) may be present)

9. Engelmann spruce (Picea engelmannii) in association other mixed conifer trees such as blue spruce (Picea pungens), white fir (Abies concolor), or Douglas-fir(Pseudotsuga menzensii); but subalpine fir (Abies lasiocarpa) is minor, if present

10. Whortleberry…