Historical Range of Variability and Current Landscape Condition Analysis: South Central Highlands Section
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See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/264884775 Historical Range of Variability and Current Landscape Condition Analysis: South Central Highlands Section... Article CITATIONS READS 38 120 10 authors, including: William H. Romme M. Lisa Floyd Colorado State University Prescott College 120 PUBLICATIONS 8,999 CITATIONS 34 PUBLICATIONS 2,146 CITATIONS SEE PROFILE SEE PROFILE Michele R. Crist Henri Grissino-Mayer Conservation Science Partners University of Tennessee 11 PUBLICATIONS 292 CITATIONS 148 PUBLICATIONS 4,811 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Lagoon Microbialites of the Gulf of Mexico View project Fire Disturbance in the Appalachian Mountains View project All content following this page was uploaded by Michele R. Crist on 11 September 2014. The user has requested enhancement of the downloaded file. Historical Range of Variability and Current Landscape Condition Analysis: South Central Highlands Section, Southwestern Colorado & Northwestern New Mexico William H. Romme, M. Lisa Floyd, David Hanna with contributions by Elisabeth J. Bartlett, Michele Crist, Dan Green, Henri D. Grissino-Mayer, J. Page Lindsey, Kevin McGarigal, & Jeffery S.Redders Produced by the Colorado Forest Restoration Institute at Colorado State University, and Region 2 of the U.S. Forest Service May 12, 2009 Table of Contents EXECUTIVE SUMMARY … p 5 AUTHORS’ AFFILIATIONS … p 16 ACKNOWLEDGEMENTS … p 16 CHAPTER I. INTRODUCTION A. Objectives and Organization of This Report … p 17 B. Overview of Physical Geography and Vegetation … p 19 C. Climate Variability in Space and Time … p 21 1. Geographic Patterns in Climate 2. Long-Term Variability in Climate D. Reference Conditions: Concept and Application … p 25 1. Historical Range of Variability (HRV) Concept 2. The Reference Period for this Analysis 3. Human Residents and Influences during the Reference Period E. Overview of Integrated Ecosystem Management … p 30 F. Literature Cited … p 34 CHAPTER II. PONDEROSA PINE FORESTS A. Vegetation Structure and Composition … p 39 B. Reference Conditions … p 40 1. Reference Period Fire Regimes 2. Other agents of disturbance 3. Pre-1870 stand structures C. Legacies of Euro-American Settlement and Current Conditions … p 67 1. Logging (“High-Grading”) in the Late 1800s and Early 1900s 2. Excessive Livestock Grazing in the Late 1800s and Early 1900s 3. Fire Exclusion Since the Late 1800s 4. Interactions: Logging, Grazing, Fire, Climate, and the Forests of Today D. Summary … p 83 E. Literature Cited … p 84 CHAPTER III. SPRUCE-FIR FORESTS A. Vegetation Structure and Composition … p 92 B. Reference Conditions … p 96 1. High-Elevation Fire Regimes: General 2. Fire History in Spruce-Fir Forests of the Western San Juan Mountains 3. Ancient Forests in the South Central Highlands Section 4. Insects and Diseases in High-Elevation Forests 5. Interactions Among Disturbances C. Legacies of Euro-American Settlement and Current Conditions … p 109 1. Effects of 20th Century Fire Suppression 2. Legacies of Logging and Road-Building 2 D. Summary … p 113 E. Literature Cited … p 115 CHAPTER IV. ASPEN FORESTS A. Vegetation Structure and Composition … p 121 1. Aspen Morphology, Population Structure, and Genetic Variability 2. Stable vs. Seral Aspen Communities 3. Aspen and Wildlife B. Reference Conditions … p 126 1. Effects of Fire in Aspen Forests 2. Fire History in Aspen Forests of the San Juan National Forest 3. Fire Behavior in Aspen Forests C. Legacies of Euro-American Settlement and Current Conditions … p 136 1. Stand-Level Effects of Logging in Aspen Forests 2. Effects of Livestock Grazing and Native Ungulate Browsing 3. Sudden Aspen Decline (SAD) 4. Is Aspen Declining in the South Central Highlands Section? D. Summary … p 142 E. Literature Cited … p 143 CHAPTER V. MIXED CONIFER FORESTS A. Vegetation Structure and Composition … p 150 B. Reference Conditions … p 154 1. Warm-Dry Mixed Conifer Forests 2. Cool-Moist or Cold-Wet Mixed Conifer Forests 3. Other Agents Of Disturbance In Mixed Conifer Forests 4. Alternative Successional Trajectories in Mixed Conifer Forests 5. Landscape Patterns in Mixed Conifer Forests of the Hermosa Unit C. Legacies of Euro-American Settlement and Current Conditions … p 167 1. Legacies of Grazing and Fire Exclusion 2. Legacies of Logging and Road Building D. Summary … p 169 E. Literature Cited … p 171 CHAPTER VI. OTHER VEGETATION TYPES A. Piñon-juniper Woodlands … p 174 1. Vegetation Structure and Composition 2. Reference Conditions in Piñon-Juniper Woodlands 3. Legacies of Euro-American Settlement and Current Conditions 4. Literature Cited B. Mountain Grasslands … p 184 1. Vegetation Structure and Composition 2. Reference Conditions in Mountain Grasslands 3. Legacies of Euro-American Settlement and Current Conditions 4. Literature Cited 3 C. Riparian Vegetation and Wetlands … p 191 1. Vegetation Structure and Composition 2. Reference Conditions in Riparian Vegetation 3. Legacies of Euro-American Settlement and Current Conditions 4. Literature Cited D. Alpine Ecosystems … p 202 1. Vegetation Structure and Composition 2. Reference Conditions in Mountain Grasslands 3. Legacies of Euro-American Settlement and Current Conditions 4. Literature Cited E. Mountain Shrublands … p 205 F. Lodgepole Pine Forests … p 208 G. Bristlecone Pine Forests … p 210 CHAPTER VII. MANAGEMENT CHALLENGES AND OPPORTUNITIES A. Challenges: Forest Fragmentation by Roads and Logging … p 212 1. General Ecological Impacts of Roads 2. Road Densities in Forests of the San Juan National Forest 3. Effects of Roads and Logging on a High-Elevation Landscape B. Challenges: Outdoor Recreation and Exurban Development … p 227 1. Ecological Impacts of Outdoor Recreation 2. Ecological Impacts of Exurban Development C. Challenges: Climate Change … p 230 D. Opportunities: Principles of Ecological Restoration … p 230 E. Opportunities: Passive Restoration of Fire and Sustainable Grazing … p 233 1. Restoring Natural Fire Regimes 2. Innovative Management of Livestock Grazing in Mountain Grasslands F. Opportunities: Active Restoration in Ponderosa Pine Forests … p 235 1. The Restoration Approach 2. Potential Pitfalls and Hazards G. Opportunities: Emulating Natural Disturbance Processes in Forests … p 244 H. Summary … p 248 I. Literature Cited … p 251 4 EXECUTIVE SUMMARY The South Central Highlands need to be evaluated individually for Section encompasses 11,475,000 acres each vegetation type. There is (46,000 km2) of the southern Rocky considerable risk in extrapolating from Mountains in southwestern Colorado and one vegetation type to another, because northwestern New Mexico, and includes some of the differences in ecology and all or a portion of the San Juan, Rio history are profound. Grande, Uncompahgre, Gunnison, A second major theme of this Carson, and Santa Fe National Forests. report is that we are not starting with a The purposes of this study were to (1) “blank slate” in terms of choices and characterize the range of variability in options in management, but that we have structure, composition, function, and several important legacies of past forest dynamics of the ecosystems of the south use and management that must be dealt central highlands section during an with in developing future management appropriate reference period, defined strategies. Some of these legacies, such here as the period of indigenous as over-cutting of mature ponderosa pine settlement prior to major impacts of in the early 1900s, may reduce our Euro-American settlement in the late management options today. In this 1800s, (2) assess the current state of paper we identify some of these major these ecosystems in terms of the extent legacies, and suggest ways of to which their structure, composition, compensating for what society may now function, and dynamics depart from that regard as poor choices in the past. In range of variability, (3) evaluate the some situations, this will entail ecological significance of specific restoration of ecological components and departures from the reference range of processes that have been lost. variability, i.e., identify any risks The third major idea underlying associated with current conditions, and this analysis is that our understanding of (4) suggest opportunities and challenges the ecology of the ecosystems in the related to restoring the altered structure, southern Rocky Mountains is still composition, function, or dynamics to inadequate to permit complete something more closely resembling the confidence in our management decisions reference period, in those situations today. We must acknowledge that we where this is a desired management are going to make some mistakes. objective. However, the seriousness of these Three important themes underlie mistakes can be reduced by placing all of what follows. First, the forest management into a consciously pronounced elevational and topographic experimental framework, by carefully variability of the South Central observing the system’s response to our Highlands Section has produced a great well-intentioned efforts -- e.g., testing variety of vegetation types, each with its explicit ecological hypotheses with each own distinctive landscape structure and timber sale, prescribed burn, or road disturbance regime. Therefore, issues closure -- and by modifying our actions related to natural ecological patterns and appropriately as we learn more about the processes, disturbance regimes, and the system