Download or read book Plant Community Response to Thinning and Repeated Fire in a Sierra Nevada Mixed conifer Forest Understory written by Maxwell Odland and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fire suppression in the western United States has significantly altered forest composition and structure, resulting in higher risk from fire and large-scale drought and bark beetle events. Mechanical thinning and prescribed fire are common treatments designed to reduce high-severity fire risk, but few studies have tracked long-term understory plant community response with repeated fire application that emulates historic fire regimes. We evaluate changes in understory plant community diversity and composition and environmental characteristics over two decades following a factorial field experiment that crosses thinning and two applications of prescribed fire at the Teakettle Experimental Forest (TEF) in the southern Sierra Nevada. We compare experimental fuels treatments against nearby old-growth, mixed-conifer forests with frequent, low severity fire regimes in Yosemite and Kings Canyon National Parks. This study points to key differences in how thinning and prescribed fire treatments affect plant understory diversity. Although local understory plant richness initially increased most following thinning combined with prescribed fire, this treatment did not generate understory communities similar to those in reference forests; Intense shrub growth resulted in low understory evenness and beta diversity over time, which a secondary burn treatment did not alter. Burning without thinning retained a more heterogeneous understory over time and, at least in the two years following the second burn treatment, with high understory richness and evenness similar to reference forest understories. Our results suggest management treatments may need to focus on creating heterogeneity in burn effects and environmental conditions to foster diverse forest understories and limit post-treatment shrub cover.

Download or read book Climate Fire and Forest Management in the Sierra Nevada written by Jens Turner Stevens and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Montane coniferous forests in western North America are experiencing rapid environmental change, due in part to increasing fire severity and decreasing winter snowpack. Many of these forests experienced frequent low-severity fires prior to intensive logging and fire suppression during the nineteenth and twentieth centuries, which have led to increased fuel loads and increased dominance by fire-sensitive, shade-tolerant tree species. Forest managers seeking to mitigate increases in fire size and severity are increasingly implementing fuel-reduction treatments, which target small trees and surface fuels for removal. However, the ecological effects of these treatments on subsequent wildfire behavior, forest resilience, understory plant community dynamics, and plant invasions have not been well documented. In Chapter 1, I utilized a large-scale natural experiment to investigate the effects of recent fuel treatments on subsequent wildfire severity and structural resilience, in twelve different yellow pine and mixed-conifer forest sites in the mountains of eastern California. By quantifying forest structure in treated and adjacent untreated stands, both after wildfire and without wildfire, I demonstrated that treatments reduced the amount of structural change caused by wildfire, as a result of their moderating effect on fire severity. Two years post-wildfire, treated stands resembled pre-wildfire stands, in that they had greater tree litter cover, more tree seedling regeneration, less shrub cover and recruitment, and less bare soil relative to untreated stands, which generally burned at very high severity. In Chapter 2, I used the same network of twelve sites to test whether the gradient of disturbance severity, from untreated and unburned stands to high-severity wildfire stands, generated predictable patterns of understory plant community composition and diversity. I incorporated information on the evolutionary history of the native flora to show that increasing disturbance severity favored understory species with southern biogeographic affinity. Analysis of leaf functional traits indicated that increases in microclimatic water deficit in high-severity stands favored species with reduced specific leaf area relative to their leaf Nitrogen concentration. Native plant diversity at the stand scale was greatest in treated stands that subsequently burned in a wildfire, however this diversity peak was due to increased plot-scale alpha diversity relative to undisturbed stands, and increased between-plot beta diversity relative to high-severity wildfire stands. Conversely, exotic plant diversity peaked in high-severity wildfire stands that had not been previously treated. In Chapter 3, I investigated the population-level response of non-native species to interactions between forest harvesting strategies, prescribed fire, and winter snowpack depth using a transplant experiment with two non-native shrubs: Scotch broom (Cytisus scoparius L. (Link)) and Spanish broom (Spartium junceum L.). Both species had the strongest positive population growth responses to canopy thinning, rather than clearcuts or dense canopies. Despite positive effects of prescribed fire on seed germination, frequent prescribed fire was shown to decrease population growth rates for both species. However, experimental snowpack reductions led to increased winter survival by both species, which translated into strong positive effects on population growth rates. Under a future climate scenario where winter snowpack levels increase in elevation, middle-elevation forests that experience fuel treatments may therefore be at increased risk of invasion by non-native plants due to synergies between climate and management regimes.

Download or read book Effects of Thinning and Prescribed Burning on Tree Resistance to Extreme Drought in a Sierra Nevada Mixed conifer Forest California USA written by Chance C. Callahan and published by . This book was released on 2019 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drought-induced tree mortality can drastically alter forest composition, structure, carbon dynamics, and ecosystem function. Increasingly, forest policy and management focuses on how to improve forest resistance and resilience to drought stress. This study used tree ring data at Teakettle Experimental Forest (TEF), a historically frequent fire mixed-conifer forest in the California Sierra Nevada, to quantify how prescribed fire and mechanical thinning conducted in 2001-2002 influenced stand and tree-level growth responses to the extreme California drought of 2012-2016. Overstory thinning and understory thinning significantly enhanced growth responses to treatments alone and treatments during the drought at the stand-level. In each year of the drought, distinct tree species were the only significant predictors of drought resistance at the stand-level. As drought persisted, shade-intolerant pine species yielded greater drought resistance values than shade-tolerant white fir and incense cedar. No prescribed burn effects were found, likely due low fire intensity. At the tree-level, tree diameter (DBH), tree height (HT), crown ratio (CRNR), topographic position index (TPI), and change in growing space over time (competition) were the most important predictors of growth responses to treatments and drought resistance. Mechanical thinning, in both understory and overstory thinning can enhance mixed-conifer forests ability to resist drought by reducing competition and increasing resource availability. This study suggests forest managers have flexibility in prescribing various thinning intensities to promote drought resistance. Prescribed burn effects were not found in this study, but further research is needed to understand long-term burn effects for promoting drought resistance in Sierra Nevada mixed-conifer forests.

Download or read book Initial Response of a Sierran Mixed conifer Understory Community to Burning and Thinning Restoration Treatments written by Rebecca Bewley Wayman and published by . This book was released on 2005 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Prescribed Fire on Understory Vegetation in Mixed conifer Forests of the Southern Sierra Nevada California written by Karen Webster and published by . This book was released on 2010 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Early Seral Mixed conifer Forest Structure and Composition Following a Wildfire Reburn in the Sierra Nevada written by Erin Alvey and published by . This book was released on 2016 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: Before the era of modern fire suppression, California's northern Sierra Nevada mixed-conifer and yellow pine forests were self-regulating; recurring short-interval, low-mixed severity wildfires maintained forest structure and composition, which in turn exerted bottom-up controls on subsequent wildfires. As a result of fire suppression, and coupled with the effects of climate warming and other anthropogenic disturbances, the fundamental structure of mixed-conifer and yellow pine forests has shifted. Wildfires may now be increasing in size, severity, and frequency across western North America. However, little is known about the post-fire impacts of repeat wildfire on a forest after a long era of suppression. In this study, I report findings regarding early successional vegetation of Sierra Nevada mixed conifer forests that experienced two large wildfires, the Storrie Fire (in 2000) and the Chips Fire (in 2012). These wildfires burned within the historic fire frequency window for this ecosystem, but much of the forest within their fire footprints had not burned for at least 100 years beforehand. I addressed three questions: (1) how does wildfire affect plant community structure and composition among yellow pine and mixed-conifer forests?; (2) do fire severity and fire frequency interact to influence post-fire vegetation conditions?; and (3) are post-fire responses similar between forests that have burned once, twice, or have not burned in the past century, or that have burned at high, moderate, or low severity? In 2014, I sampled 74 plots in the Plumas and Lassen National Forests. Of these plots, 50 plots were sampled from three fire severity classes and two fire frequencies in and around the Chips Fire (2012). A portion of the Chips Fire had reburned the Storrie Fire (2000), affording the opportunity to compare them to post-fire effects of a single burn on fire-suppressed forests at the same stage of post-fire succession. I also collected data in 24 unburned plots to contrast fire-suppressed plots with plots that experienced wildfire. Wildfire decreased tree density but also decreased available seed sources, which can limit tree regeneration in high severity fire or reburns. Increased tree mortality also produced greater fuel loading in reburns compared to single burns, though burned plots exhibited less fuel loading and fuel connectivity than unburned plots. I also observed that wildfire diversified species composition in single burns, increasing species richness, evenness, and diversity. However, reburning plots appeared to reduce species richness, causing reburns to exhibit richness similar to unburned plots. Still, reburn plots only shared about half of its species with unburned plots, and 13% of species were exclusive to reburns. My study was limited to a particular time (two years post-fire), and post-fire effects may become more pronounced as early seral communities continue to respond to the effects of the wildfire. Nonetheless, my results indicate that wildfire can produce forest structure and composition that is dramatically different from fire-suppressed mixed-conifer forests. Though it is unknown whether ecological processes can be restored by just one or two wildfire events within a short time-span in fire-suppressed landscapes, the post-fire conditions observed in my study have begun to resemble pre-suppression conditions by exhibiting reduced tree densities, lower fuel loads, and enhanced species diversity, especially at low to moderate fire severities. Because post-fire vegetation response is a stochastic and long-term process, understanding the effects of wildfire reintroduction and reburn will likely take multiple observations.

Download or read book Fire in California s Ecosystems written by Jan W. van Wagtendonk and published by Univ of California Press. This book was released on 2018-06-08 with total page 567 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Fire and Fire Surrogate Effects on Soil Properties in a Sierra Nevada Mixed conifer Forest written by Emily Eleanor Yukie Moghaddas and published by . This book was released on 2007 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Long term Effects of Fire Hazard Reduction Treatments in the Southern Cascades and Northern Sierra Nevada California written by Lindsay Aney Chiono and published by . This book was released on 2012 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: Historic fire regimes in the dry conifer forests of the southern Cascade and northern Sierra Nevada regions of California were characterized by relatively frequent fires of low and mixed severity. Human management practices since the mid-19th century have altered the disturbance role of fire in these dry yellow pine and mixed conifer forest ecosystems. Fire suppression, high-grade timber harvesting, and livestock grazing have reduced the frequency of burning and caused a shift in the structure and species composition of forest vegetation. These changes, including high levels of accumulated fuel and increased structural homogeneity and dominance of shade-tolerant tree species, combined with a warming climate, have rendered many stands susceptible to high-severity fire. In many forests of the western United States, wildfires are increasingly difficult and costly to control, and human communities are regularly threatened during the fire season. Treating wildland fuels to reduce wildfire hazards has become a primary focus of contemporary forest management, particularly in the wildland-urban interface. The specific objectives of treatment are diverse, but in general, treatments address accumulated surface fuels, the fuel ladders that carry fire into the forest canopy, and surface and canopy fuel continuity. These modifications to forest fuels can alleviate the severity of a future wildfire and support suppression activities through improved access and reduced fire intensity. While fuel reduction treatments are increasingly common in western forests, the long-term structural and ecological effects of treatment remain poorly understood. This dissertation uses a chronosequence of treated stands to examine the temporal influence of treatment on forest structure, the understory plant community, and wildfire hazard. The first chapter examines the effects of fuels reduction treatment on stand structure, overstory species composition, and ground and surface fuels. The stand structures and reduced surface fuel loads created by fuels modification are temporary, yet few studies have assessed the lifespan of treatment effects. The structural legacies of treatment were still present in the oldest treatment sites. Treatments reduced site occupancy (stand density and basal area) and increased quadratic mean diameter by approximately 50%. The contribution of shade-tolerant true firs to stand density was also reduced by treatment. Other stand characteristics, particularly timelag fuel loads, seedling density, and shrub cover, exhibited substantial variability, and differences between treatment age classes and between treatment and control groups were not statistically significant. The second chapter evaluates fuel treatment longevity based on potential wildfire behavior and effects on vegetation. Forest managers must divide scarce resources between fuel treatment maintenance, which is necessary to retain low hazard conditions in treated stands, and the construction of new treatments. Yet the most basic questions concerning the lifespan of treatment effectiveness have rarely been engaged in the literature. In this study, field-gathered fuels and vegetation data were used to aid fuel model selection and to parameterize a fire behavior and effects model, Fuels Management Analyst Plus. In addition, a semi-qualitative, semi-quantitative protocol was applied to assess ladder fuel hazard in field sampling plots. Untreated sites exhibited fire behavior that would challenge wildfire suppression efforts, and projected overstory mortality was considerable. In contrast, estimated fire behavior and severity were low to moderate in even the oldest fuel treatments, those sampled 8-26 years after treatment implementation. Findings indicate that in the forest types characteristic of the northern Sierra Nevada and southern Cascades, treatments for wildfire hazard reduction retain their effectiveness for more than 10-15 years and possibly beyond a quarter century. Fuel treatment activities disturb the forest floor, increase resource availability, and may introduce non-native plant propagules to forest stands. Non-native plant invasions can have profound consequences for ecosystem structure and function. For these reasons, there is concern that treatment for fire hazard reduction may promote invasion by exotic species. Several short-term studies have shown small increases in non-native abundance as a result of treatment, but the long-term effects have rarely been addressed in the literature. The final chapter examines treatment effects on the understory plant community and on cover of the forest floor, as mineral soil exposure has been linked to invasion. Regression tree analysis provided insights into the influence of treatment and site characteristics on these variables. Treatments increased forb and graminoid cover, but temporal trends in abundance were opposite. An initial increase in forb cover in the most recently treated sites was followed by a gradual decline, while mean graminoid cover was highest in the oldest treatments. Shrubs dominated live plant abundance. Shrub cover showed few temporal trends, but was negatively associated with canopy cover. Mineral soil exposure was increased by treatment and declined slowly over time, remaining elevated in the oldest treatments. Non-native plant species were very rare in the treatment sites sampled in this study. Despite the availability of bare mineral soil and the proximity of transportation corridors, a source of non-native propagules, non-natives were recorded in only 2% of sampling plots. This study suggests that forest disturbance associated with treatment for hazardous fuels reduction may not produce significant invasions in these forest types.

Download or read book Fire in Sierra Nevada Forests written by George E. Gruell and published by . This book was released on 2001 with total page 266 pages. Available in PDF, EPUB and Kindle. Book excerpt: In Fire in Sierra Nevada Forests, George Gruell examines the woodlands through repeat photography: rephotographing sites depicted in historical photographs to compare past vegetation to present. The book asks readers to study the evidence, then take an active part in current debates over prescribed fire, fuel buildup, logging, and the management of our national forests.

Download or read book Wildland Fire in Ecosystems written by and published by . This book was released on 1998 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Responses of Dry Forest Understory Diversity to Thinning Intensity and Burning written by Allison K. Rossman and published by . This book was released on 2017 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mechanical thinning and prescribed burning are commonly used to restore dry, mixed-conifer forests that historically experienced frequent fire. Although these treatments successfully reduce fuel loads, their ability to achieve ecological objectives, such as promoting native plant diversity, is less certain. My thesis research examined how temporal and spatial scales of observation and the approach to analyzing scale-dependent data influence our understanding of understory vegetation responses to thinning intensity and burning. I used long-term data on understory species richness from a restoration experiment in central Washington. I found no effect of thinning intensity alone and scale-dependent responses to burning. For example, annual richness increased over time in burned plots, particularly at small spatial scales, suggesting enhanced recruitment from early-established populations and little perennial expansion. I also found that the analytical approach used to address common challenges of large-scale, long-term experiments, such as variation in pre-treatment conditions and the loss of sample units over time, can affect the conclusions drawn from these experiments. However, careful specification of research questions and consideration of data limitations can yield insights into these conclusions. This research highlights long-term ecological benefits of prescribed burning and the need for measurements over time and among spatial scales, as well as the careful evaluation of analytical approaches, to clarify whether fuel-reduction treatments meet the ecological objectives of dry forest restoration.

Download or read book The Effects of Fire and Fuels Reduction Treatments on Fire Hazard and Soil Carbon Respiration in a Sierra Nevada Pine Plantation written by Leda Nikola Kobziar and published by . This book was released on 2006 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Throughout fire-adapted forests of the western US, and in the Sierra Nevada of California specifically, wildfire suppression has produced forest structures conducive to more severe, costly, and ecologically deleterious fires. Recent legislation has identified the necessity of management practices that manipulate forests towards less fire-hazardous structures. In the approximately 30 year old pine plantations of the Stanislaus National Forest, extensive fuels reduction procedures are being implemented. This dissertation addresses whether silvicultural and burning treatments are effective at reducing the intensity and severity of potential fire behavior, and how, along with wildfire, these treatments impact the evolution of carbon dioxide from the soil to the atmosphere. The first chapter addresses the relationships between soil respiration, tree injury, and forest floor characteristics in high and low severity wildfire burn sites in a salvage-logged mixed-conifer forest. The results indicate that fire severity influences soil CO2 efflux and should be considered in ecosystem carbon modeling. In the next chapter, fire models suggest that mechanical shredding of understory vegetation (mastication) is detrimental, and prescribed fire most effective in reducing potential fire behavior and severity in pine plantations. The third chapter documents the impact of alternative fuels treatments on soil carbon respiration patterns in the pine plantations, and shows that mastication produces short-term reductions in respiration rates and soil moisture. The final chapter further examines the relationships of fire-induced tree injuries, forest floor structure, and environmental factors to soil respiration response to fuels treatments. Each chapter is written as an independent manuscript; they collectively serve to expand the limited understanding of the effectiveness and ecological consequences of fire and fuels treatments in coniferous forests."--Abstract

Download or read book Patterns and Processes in Forest Landscapes written by Raffaele Lafortezza and published by Springer Science & Business Media. This book was released on 2008-08-30 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing evidence suggests that the composition and spatial configuration – the pattern – of forest landscapes affect many ecological processes, including the movement and persistence of particular species, the susceptibility and spread of disturbances such as fires or pest outbreaks, and the redistribution of matter and nutrients. Understanding these issues is key to the successful management of complex, multifunctional forest landscapes, and landscape ecology, based on a foundation of island bio-geography and meta-population dynamic theories, provides the rationale to deal with this pattern-to-process interaction at different spatial and temporal scales. This carefully edited volume represents a stimulating addition to the international literature on landscape ecology and resource management. It provides key insights into some of the applicable landscape ecological theories that underlie forest management, with a specific focus on how forest management can benefit from landscape ecology, and how landscape ecology can be advanced by tackling challenging problems in forest (landscape) management. It also presents a series of case studies from Europe, Asia, North America, Africa and Australia exploring the issues of disturbance, diversity, management, and scale, and with a specific focus on how human intervention affects forest landscapes and, in turn, how landscapes influence humans and their culture. An important reference for advanced students and researchers in landscape ecology, conservation biology, forest ecology, natural resource management and ecology across multiple scales, the book will also appeal to researchers and practitioners in reserve design, ecological restoration, forest management, landscape planning and landscape architecture.

Download or read book Terrestrial Vegetation of California 3rd Edition written by Michael Barbour and published by Univ of California Press. This book was released on 2007-07-17 with total page 732 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This completely new edition of Terrestrial Vegetation of California clearly documents the extraordinary complexity and richness of the plant communities and of the state and the forces that shape them. This volume is a storehouse of information of value to anyone concerned with meeting the challenge of understanding, managing or conserving these unique plant communities under the growing threats of climate change, biological invasions and development."—Harold Mooney, Professor of Environmental Biology, Stanford University "The plants of California are under threat like never before. Traditional pressures of development and invasive species have been joined by a newly-recognized threat: human-caused climate change. It is essential that we thoroughly understand current plant community dynamics in order to have a hope of conserving them. This book represents an important, well-timed advance in knowledge of the vegetation of this diverse state and is an essential resource for professionals, students, and the general public alike."—Brent Mishler, Director of the University & Jepson Herbaria and Professor of Integrative Biology, University of California, Berkeley

Download or read book California Agriculture written by and published by . This book was released on 2015 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fire induced Tree Mortality in the Mixed Conifer Forests of the Sierra Nevada California written by Phillip John Van Mantgem and published by . This book was released on 2001 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: