Fire in California's Ecosystems

Fire in California’s Ecosystems describes fire in detail—both as an integral natural process in the California landscape and as a growing threat to urban and suburban developments in the state. Written by many of the foremost authorities on the subject, this comprehensive volume is an ideal authoritative reference tool and the foremost synthesis of knowledge on the science, ecology, and management of fire in California. Part One introduces the basics of fire ecology, including overviews of historical fires, vegetation, climate, weather, fire as a physical and ecological process, and fire regimes, and reviews the interactions between fire and the physical, plant, and animal components of the environment. Part Two explores the history and ecology of fire in each of California's nine bioregions. Part Three examines fire management in California during Native American and post-Euro-American settlement and also current issues related to fire policy such as fuel management, watershed management, air quality, invasive plant species, at-risk species, climate change, social dynamics, and the future of fire management. This edition includes critical scientific and management updates and four new chapters on fire weather, fire regimes, climate change, and social dynamics.

ISBN-13: 9780520286832

Media Type: Hardcover

Publisher: University of California Press

Publication Date: 06-08-2018

Pages: 568

Product Dimensions: 8.40(w) x 11.00(h) x 1.60(d)

Jan W. van Wagtendonk is Research Forester Emeritus with the National Park Service, Yosemite National Park. Neil G. Sugihara is Program Coordinator, Wildfire Training and Education, at Northern Arizona University. Scott L. Stephens is Professor of Fire Science, Department of Environmental Science, Policy, and Management, at the University of California, Berkeley. Andrea E. Thode is Professor of Fire Ecology and Management, School of Forestry, at Northern Arizona University. Kevin E. Shaffer is Fisheries Chief at the California Department of Fish and Wildlife. Jo Ann Fites-Kaufman is a private consultant.

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CHAPTER 1

Introduction

Fire and California Vegetation

NEIL G. SUGIHARA, TODD KEELER-WOLF, AND MICHAEL G. BARBOUR

In California, vegetation is the meeting place of fire and ecosystems. The plants are the fuel and fire is the driver of vegetation change. Fire and vegetation are often so interactive that they can scarcely be considered separately from each other.

BARBOUR et al. (1993)

Fire is a vital, dynamic force of nature in California's ecosystems and shapes the composition and structure of its vegetation. For millennia, human interaction with fire has developed simultaneously around our need to protect ourselves from its harm and the opportunity to use it as a natural resource management tool. As we become more aware of what influences and controls fire, we are gaining an appreciation of the contribution that fire makes to ecosystem complexity and biological diversity. Previous notions that we can, and should, suppress all wildfires to provide for human safety and protect ecological resources are giving way to the realization that we don't have the ability to completely exclude fire, and that many valued attributes of California's ecosystems shouldn't be protected from fire, but actually require fire. To meet both protection and ecological objectives, we must manage wildland fire and adapt our own behavior to coexist with fire. Managing wildland fire is certainly one of the largest and most complex ecosystem management and restoration efforts ever undertaken, and understanding fire and the consequences of its patterns of occurrence and exclusion is essential. This complexity was underscored during the fall of 2017 when over 200,000 ha (500,000 ac) burned, over 9,000 structures destroyed, and over 40 people killed. These fires were driven by high winds under extremely hot and dry conditions into a mixture of development and wildlands.

This revised edition incorporates a better understanding of both fire variability within vegetation patterns and fire-adaptive or nonfire-adaptive life histories of plant species. Our continuously expanding information base is gained through individual studies and through the compilation of information such as the second edition of A Manual of California Vegetation (Sawyer and KeelerWolf 2009) and online databases (vegetation.cnps.org).

Fire as an Ecological Process

Much of California has a Mediterranean climate conducive to fire (Pyne et al. 1996) with long dry summers and periods of thunderstorms, low relative humidity, and strong winds. These patterns vary through an extremely wide range of climatic zones and complex topography.

Fire is a physical process, and both its direct and indirect effects are vitally important ecological processes. The heat it produces, the rate at which it spreads, and the effects it has on other ecosystem components are all part of that physical process. Human communities, watersheds, soils, air, plants, and animals are affected in one way or another by fire. Water quality and quantity, soil erosion, smoke, and plant and animal mortality are some of the more obvious effects. Other ecosystem effects are less obvious, but perhaps even more important. During the periods between fires, dead biomass accumulates in Mediterranean ecosystems because weather conditions are favorable for growth, but decomposition is active for only a relatively short moist part of the year. Fire complements decomposition in these systems by periodically removing debris through combustion. Fire has a differential effect on plant species mortality and regeneration, allowing those that are best adapted to fire to be perpetuated.

Pyrogenic vegetation has evolved with recurring fire and includes species that tolerate or even require fire in order to complete their life cycles. There is a continuous feedback loop between fire and vegetation. Fire feeds on vegetation as fuel and cannot reoccur without some minimum burnable, continuous biomass; and the vegetation cannot maintain its occupation of a site without recurring fire. Fire and vegetation are often so interactive that they can scarcely be considered separately from each other. Indeed, for a plant species to persist, the attributes of any fire regime — its seasonality, return interval, size, spatial complexity, intensity, severity, and type — elicit specific responses. We consider fire regimes and vegetation types to be mutually dependent with changes to either, facilitating changes to the other.

In California, animal populations and communities have developed in habitats where fire has been a primary dynamic process. The distribution of most animal species on landscapes has been driven by the patterns of fire and vegetation; controlled by climate, weather, and topography, over space and time. Perpetuation of California's biological diversity certainly requires fire to be present as a vital ecological process.

It is difficult to overstate the ecological importance of fire in California's ecosystems. A central theme to this book is that wildfire is a pervasive, natural, environmental factor throughout much of the state, and ignoring its role in ecosystems will seriously limit our ability to manage wildlands in a sustainable, ecologically appropriate, and responsible manner. To better understand the role of fire in California, it is useful to examine the evolution of its vegetation.

California's Floristic Provinces — Evolution of the Vegetation

The State of California is divided into three floristic provinces: California, Desert, and Great Basin (Baldwin et al. 2012). The California Floristic Province corresponds to the Humid Temperate Domain of Bailey (1996) and Miles and Goudey (1997) and comprises the portion of California west of the mountainous crest. Both the Great Basin Floristic Province and the Desert Floristic Province are in Bailey's Dry Domain. The vegetation in the provinces evolved from two different floras. These have been termed as the Arcto-Tertiary Flora (cool climate northern origins) and the Madro-Tertiary Flora (warm temperate-tropical Sierra Madre origins) (Axelrod 1958). The Acrto-Tertiary Flora dominates in the North Coast, Sierra Nevada, Klamath Mountains, and Southern Cascades bioregions. Species from the Madro-Tertiary Flora are most common in the Central Valley, Central Coast, Northeastern Plateaus, Southeastern Deserts, South Coast, and the east portion of the Sierra Nevada bioregions.

The modern array of bioregions is a product of millions of years of plant evolution, geologic upheavals, climate change, and plant community adaptation and migration. Millar (2012) provides a cogent modern perspective of the evolution of California's flora, which we summarize here. Fifty million years ago (Ma), in the Paleocene Epoch, California was low-lying. Increasing temperatures and humidity triggered significant floristic shifts toward tropical species with affinities to taxa now in rain forests of eastern Asia, southern Mexico, and Amazonia. Western California had diverse subtropical plant communities, while upland regions to the east (the proto — Great Basin) supported temperate-adapted species, including many conifers and associates now present in the modern flora.

About 33.5 Ma, abrupt changes in floristic composition and structure took place. Tropical woody angiosperm species disappeared and temperate-adapted species reappeared, especially broad-leaved deciduous trees and conifers. The new plant communities had affinities to modern communities with high geographic variance due to landscape diversity. Highly diverse assemblages with some taxa present in California today and others now native to warmer, and milder climates with year-round rainfall predominated up until about 23 Ma.

Global temperatures rose between 17 Ma and 15 Ma to the highest levels of the past 23 million years. Fossil floras throughout the West reflected adaptations and range shifts in response to these conditions, with increasing latitudinal gradients from coastal environments to inland mountains. Warm dry-adapted species occurred together, alongside now-exotic tropical-subtropical taxa. In the higher ranges of western Nevada and northeast California, fossil assemblages contained diverse conifers and hardwoods.

Fossil floras less than 7 Ma (Pliocene Epoch), showed a Mediterranean-type semiarid climate establishing at low elevations. Grasslands, chaparral, mixed evergreen sclerophyllous forest, and oak woodlands expanded. Elements of the warm-temperate (Madro-Tertiary) flora became dominant throughout low elevations, while cool-temperate Arcto-Tertiary taxa and vegetation retreated to high elevations, riparian areas, or the coastal strip. The Sierra Nevada, Klamath Mountains, and Transverse Ranges were thrust up to ever higher elevations, creating rain shadows to the east that deepened and expanded over time to become today's hot and cold deserts, dominated by drought-tolerant shrubs, succulent cacti, and short-lived ephemeral herbs.

By the end of the Tertiary (2.6 Ma), many vegetation types of modern California were in place. The beginning of the Quaternary Period brought climate variability and cooling leading to the ice ages. Ice-core records show over 40 cycles of glacial (cold) and interglacial (warm) intervals, each with smaller internal variations. The ice ages of the Pleistocene epoch ended about 10,000 years ago with the arrival of our recent warm epoch, the Holocene.

Quaternary glacial advance and retreat forced vegetation types with their associated fire regimes to migrate upslope and down-slope, or southward and northward. California's mountain chains are largely oriented north-to-south, montane taxa driven south were able to migrate back north during warmer interglacial periods, including the current period. The most recent glacial retreat was completed about 10,000 years ago, but cold and warm periods continue to alternate and short-term climate fluctuations continually affect the location of ecotones.

A cooling trend about 4,000 years ago distinguished the late Holocene from the warm middle Holocene (6,000 years to 4,000 years ago). Between 700 years and 1,100 years ago two major droughts occurred, each lasting more than a century. These caused many large lakes and rivers to dry, and salinities to increase in those that remained. Tree-ring records for the past several hundred years (Michaelsen et al. 1987) show continued fluctuation in temperature, precipitation, and interannual variation at the time scale of one-to-several decades.

Twelve thousand years ago, before humans arrived in California, vegetation type diversity and distribution were different than they are today or than they were at any time during the modern human eras. However, it is likely that fire regimes played a role in sustaining the same vegetation type in the past. Before the modern Anthropocene, fire regimes within a stable vegetation type probably did not change much over time.

Bioregions and the California Landscape

The diversity of the California landscape is well known; from the mist-shrouded mountains of the north coast to the searing heat of the Southeastern Deserts, and from the sun-drenched beaches of the South Coast to the high Sierra Nevada, the range of climate, geomorphology, and vegetation mirrors this diversity. Similarly, fire's role in each of these bioregions is equally diverse. To give structure to the discussion of fire complexity within these vast and diverse landscapes, we have divided California into a system of bioregions.

If we add up the areas of vegetation types generally regarded as fire-maintained, about 54% of California's 42 million ha (104 million ac) requires the repeated occurrence of fire to persist (Barbour et al. 2007). Fire-adapted in this case requiresmajor characteristic species of each unit to have adaptions for asexual or sexual regeneration supported by recurring fire. The totals in Table 1.1 are for approximately 55% of the state. A number of natural arid land vegetation types such as desert scrub, alkali desert scrub, Joshua tree woodland, and pinyon-juniper woodland are not well adapted to fire. A number of non-natural anthropogenic land covers such as urban, orchards, and other crops also make up a large proportion of the nonfire adapted land cover. Only some types of desert scrub, alpine tundra, subalpine woodland, and a few, less widespread, vegetation types are not fire-dependent. Even some wetlands — such as bulrush (Schoenoplectus spp.) marsh, riparian forest, and California fan palm (Washingtonia filifera) oases — are fire tolerant and experienced fires set both by indigenous human populations and lightning strikes (Anderson 2005). Knowledge of how fire operates as an ecological process within the State's various bioregions is part of the foundation for wise management and conservation of California's natural heritage.

A hierarchical ecosystem classification for ecosystems in the United States was developed based on climate, as affected by latitude, continental position, elevation, and landform (Bailey et al. 1994, Bailey 1996). Miles and Goudey (1997) divided California into 19 sections within Bailey's system (Table 1.2), and we combine these sections into nine bioregions based on relatively consistent patterns of vegetation and fire regimes (Maps 1.1 and 1.2).

The nine bioregions range from the humid northwest corner of the state to the arid southeast. In the North Coast bioregion, numerous valleys and steep coastal and interior mountains create moisture gradients in response to numerous winter storms. The Klamath Mountains bioregion is a complex group of mountain ranges and a diverse flora. Tall volcanoes and extensive lava flows characterize the Southern Cascades and Northeastern Plateau bioregions. Immediately south of the Cascades is the Sierra Nevada bioregion, extending nearly half the length of the state. The Sacramento and San Joaquin rivers flow through broad interior valleys with extensive, nearly flat alluvial floors that constitute the Central Valley bioregion. Coastal valleys and mountains and interior mountains are also typical of the Central Coast bioregion. Southern California with its coastal Valleys and the prominent Transverse and Peninsular Ranges make up the South Coast bioregion. The Mojave, Colorado, and Sonoran deserts along with intervening mountain ranges constitute the Southeastern Desert bioregion.

In Part II of this book, we will examine each bioregion in detail to see how the physical features of the bioregion influence the interactions among fire, vegetation, and other ecosystem components. But first we will take a statewide look at Californians and fire.

Californians and Fire

The arrival of humans in the area that we now know as California had profound influences on fire regimes and the character and distribution of the vegetation. Fire has often been the driving force behind human-induced vegetation change. Native American fire use resulted in many changes to California vegetation, but over several millennia, their activities provided a stabilizing influence for many fire regimes. Relatively speaking, the landscapes of California changed little prior to arrival of Euro-American settlers. Few plant species became extinct, the belts of vegetation in mountains remained nearly the same; the height of mountain peaks, the thickness of sediments beneath meadows and grasslands, the distribution of wetlands, the location of sea level, and the gradients of humidity and aridity from coastal west to interior east shifted little. In Part III of this book we describe how the succession of dominant human cultures that have lived in California view fire, use it, try to suppress it, and deal with its effects on biological and physical resources and on social and political issues.

Dramatic change has clearly occurred in the past two centuries due to nonnative and invasive plants, agriculture, fire exclusion, domesticated livestock, and human populations, which are reaching 100 times denser than that of pre-contact time (Barbour et al. 2007). Much of California's Central Valley and other fertile areas have been converted to agriculture or urbanized, areas of coastal sage scrub have converted to nonnative grasslands, and many mid-elevation conifer forests have been logged and regenerated with species compositions and stand densities that have little historic precedent.

It is not the occurrence of fire in an ecosystem that constitutes an ecological disturbance, but rather our actions that have led to changes to the characteristic fire regimes. Like vegetation, fire regimes have probably never been completely static, but the pace and magnitude of changes to Californian fire regimes accelerated with the arrival of humans from Asia 12,000+ years ago (Rosenthal and Fitzgerald 2012) and again with the arrival of large numbers of settlers of Euro-American origin with the Gold Rush in the mid-1800s. Despite intensive efforts to suppress wildland fires over the past century, fires have continued to burn.

(Continues…)

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Table of Contents

LIST OF CONTRIBUTORS ix

FOREWORD xi
JAMES K. AGEE

PREFACE xv

1 Introduction: Fire and California Vegetation / 1
NEIL G. SUGIHARA, TODD KEELER-WOLF, AND MICHAEL G. BARBOUR

PART ONE
Introduction to Fire Ecology

2 California Fire Climate / 11
RICHARD A. MINNICH
3 Fire Weather Principles / 27
BRENDA L. BELONGIA AND RICHARD A. MINNICH
4 Fire as a Physical Process / 39
JAN W. VAN WAGTENDONK
5 Fire as an Ecological Process / 57
NEIL G. SUGIHARA, JAN W. VAN WAGTENDONK, AND JO ANN FITES-KAUFMAN
6 Characterizing Fire Regimes / 71
BRANDON M. COLLINS, JAY D. MILLER, JEFFREY M. KANE, DANNY L. FRY, AND ANDREA E. THODE
7 Fire and Physical Environment Interactions: Soil, Water, and Air / 87
PETER M. WOHLGEMUTH, KEN R. HUBBERT, TRENT PROCTER, AND SURAJ AHUJA
8 Fire and Plant Interactions / 103
AMY G. MERRILL, ANDREA E. THODE, ALEXANDRA M. WEILL, JO ANN FITES-KAUFMAN, ANNE F. BRADLEY, AND TADASHI J. MOODY
9 Fire and Animal Interactions / 123
KEVIN E. SHAFFER, SHAULA J. HEDWALL, AND WILLIAM F. LAUDENSLAYER, JR.

PART TWO
The History and Ecology of Fire in California’s Ecosystems

10 North Coast Bioregion / 149
SCOTT L. STEPHENS, JEFFREY M. KANE, AND JOHN D. STUART
11 Klamath Mountains Bioregion / 173
CARL N. SKINNER, ALAN H. TAYLOR, JAMES K. AGEE, CHRISTY E. BRILES, AND CATHY L. WHITLOCK
12 Southern Cascades Bioregion / 197
CARL N. SKINNER AND ALAN H. TAYLOR
13 Northeastern Plateaus Bioregion / 221
GREGG M. RIEGEL, RICHARD F. MILLER, CARL N. SKINNER, SYDNEY E. SMITH, CALVIN A. FARRIS, AND KYLE E. MERRIAM
14 Sierra Nevada Bioregion / 251
JAN W. VAN WAGTENDONK, JO ANN FITES-KAUFMAN, HUGH D. SAFFORD, MALCOLM P. NORTH, AND BRANDON M. COLLINS
15 Central Valley Bioregion / 281
ROBIN WILLS
16 Central Coast Bioregion / 299
MARK I. BORCHERT AND FRANK W. DAVIS
17 South Coast Bioregion / 319
JON E. KEELEY AND ALEXANDRA D. SYPHARD
18 Southeastern Deserts Bioregion / 353
MATTHEW L. BROOKS, RICHARD A. MINNICH, AND JOHN R. MATCHETT

PART THREE
Fire Management Issues in California’s Ecosystems

19 The use of Fire by Native Americans in California / 381
M. KAT ANDERSON
20 Fire Management and Policy since European Settlement / 399
SCOTT L. STEPHENS AND NEIL G. SUGIHARA
21 Fire and Fuel Management / 411
SCOTT L. STEPHENS, SUE J. HUSARI, H. TOM NICHOLS, NEIL G. SUGIHARA, AND BRANDON M. COLLINS
22 Fire, Watershed Resources, and Aquatic Ecosystems / 427
JAN L. BEYERS, ANDREA E. THODE, JEFFREY L. KERSHNER, KEN B. ROBY, AND LYNN M. DECKER
23 Fire, Air Quality, and Greenhouse Gases / 439
SURAJ AHUJA AND TRENT PROCTER
24 Fire and Invasive Plants / 459
ROBERT. C. KLINGER, MATTHEW L. BROOKS, AND JOHN M. RANDALL
25 Fire and At-Risk Species / 477
KEVIN E. SHAFFER AND SHAULA J. HEDWALL
26 Fire and Climate Change / 493
CHRISTINA M. RESTAINO AND HUGH D. SAFFORD
27 Social Dynamics of Wildland Fire in California / 507
SARAH M. MCCAFFREY, GUY L. DUFFNER, AND LYNN M. DECKER
28 The Future of Fire in California’s Ecosystems / 517
NEIL G. SUGIHARA, JAN W. VAN WAGTENDONK, SCOTT L. STEPHENS, KEVIN E. SHAFFER, ANDREA E. THODE, AND JO ANN FITES-KAUFMAN

APPENDIX 1 523 Show More