Origins of Abrupt Change? Postfire Subalpine Conifer Regeneration Declines Nonlinearly with Warming and Drying PDF Download
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Author: Winslow D. Hansen
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 21
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Book Description
Robust tree regeneration following high-severity wildfire is key to the resilience of subalpine and boreal forests, and 21st century climate could initiate abrupt change in forests if postfire temperature and soil moisture become less suitable for tree seedling establishment. Using two widespread conifer species, lodgepole pine (Pinus contorta var. latifolia) and Douglas-fir (Pseudotsuga menziesii var. glauca), we conducted complementary experiments to ask (1) How will projected early- to mid-21st-century warming and drying affect postfire tree seedling establishment and mortality? (2) How does early seedling growth differ between species and vary with warming and drying? With a four-year in situ seed-planting experiment and a one growing season controlled-environment experiment, we explored effects of climate on tree seedling establishment, growth, and survival and identified nonlinear responses to temperature and soil moisture. In our field experiment, warmer and drier conditions, consistent with mid21st-century projections, led to a 92% and 76% reduction in establishment of lodgepole pine and Douglas-fir. Within three years, all seedlings that established under warmer conditions died, as might be expected at lower elevations and lower latitudes of species? ranges. Seedling establishment and mortality also varied with aspect; approximately 1.7 times more seedlings established on mesic vs. xeric aspects, and fewer seedlings died. In the controlled-environment experiment, soil temperatures were 2.0°?5.5°C cooler than the field experiment, and warming led to increased tree seedling establishment, as might be expected at upper treeline or higher latitudes. Lodgepole pine grew taller than Douglas-fir and produced more needles with warming. Douglas-fir grew longer roots relative to shoots, compared with lodgepole pine, particularly in dry soils. Differences in early growth between species may mediate climate change effects on competitive interactions, successional trajectories, and species distributions. This study demonstrates that climate following high-severity fire exerts strong control over postfire tree regeneration in subalpine conifer forests. Climate change experiments, such as those reported here, hold great potential for identifying mechanisms that could underpinfundamental ecological change in 21st-century ecosystems.
Author: Winslow D. Hansen
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 21
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Book Description
Robust tree regeneration following high-severity wildfire is key to the resilience of subalpine and boreal forests, and 21st century climate could initiate abrupt change in forests if postfire temperature and soil moisture become less suitable for tree seedling establishment. Using two widespread conifer species, lodgepole pine (Pinus contorta var. latifolia) and Douglas-fir (Pseudotsuga menziesii var. glauca), we conducted complementary experiments to ask (1) How will projected early- to mid-21st-century warming and drying affect postfire tree seedling establishment and mortality? (2) How does early seedling growth differ between species and vary with warming and drying? With a four-year in situ seed-planting experiment and a one growing season controlled-environment experiment, we explored effects of climate on tree seedling establishment, growth, and survival and identified nonlinear responses to temperature and soil moisture. In our field experiment, warmer and drier conditions, consistent with mid21st-century projections, led to a 92% and 76% reduction in establishment of lodgepole pine and Douglas-fir. Within three years, all seedlings that established under warmer conditions died, as might be expected at lower elevations and lower latitudes of species? ranges. Seedling establishment and mortality also varied with aspect; approximately 1.7 times more seedlings established on mesic vs. xeric aspects, and fewer seedlings died. In the controlled-environment experiment, soil temperatures were 2.0°?5.5°C cooler than the field experiment, and warming led to increased tree seedling establishment, as might be expected at upper treeline or higher latitudes. Lodgepole pine grew taller than Douglas-fir and produced more needles with warming. Douglas-fir grew longer roots relative to shoots, compared with lodgepole pine, particularly in dry soils. Differences in early growth between species may mediate climate change effects on competitive interactions, successional trajectories, and species distributions. This study demonstrates that climate following high-severity fire exerts strong control over postfire tree regeneration in subalpine conifer forests. Climate change experiments, such as those reported here, hold great potential for identifying mechanisms that could underpinfundamental ecological change in 21st-century ecosystems.
Author: Cathryn H. Greenberg
Publisher: Springer Nature
ISBN: 3030732673
Category : Science
Languages : en
Pages : 513
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Book Description
This edited volume presents original scientific research and knowledge synthesis covering the past, present, and potential future fire ecology of major US forest types, with implications for forest management in a changing climate. The editors and authors highlight broad patterns among ecoregions and forest types, as well as detailed information for individual ecoregions, for fire frequencies and severities, fire effects on tree mortality and regeneration, and levels of fire-dependency by plant and animal communities. The foreword addresses emerging ecological and fire management challenges for forests, in relation to sustainable development goals as highlighted in recent government reports. An introductory chapter highlights patterns of variation in frequencies, severities, scales, and spatial patterns of fire across ecoregions and among forested ecosystems across the US in relation to climate, fuels, topography and soils, ignition sources (lightning or anthropogenic), and vegetation. Separate chapters by respected experts delve into the fire ecology of major forest types within US ecoregions, with a focus on the level of plant and animal fire-dependency, and the role of fire in maintaining forest composition and structure. The regional chapters also include discussion of historic natural (lightning-ignited) and anthropogenic (Native American; settlers) fire regimes, current fire regimes as influenced by recent decades of fire suppression and land use history, and fire management in relation to ecosystem integrity and restoration, wildfire threat, and climate change. The summary chapter combines the major points of each chapter, in a synthesis of US-wide fire ecology and forest management into the future. This book provides current, organized, readily accessible information for the conservation community, land managers, scientists, students and educators, and others interested in how fire behavior and effects on structure and composition differ among ecoregions and forest types, and what that means for forest management today and in the future.
Author: Edward Struzik
Publisher: McGill-Queen's Press - MQUP
ISBN: 0228013488
Category : Nature
Languages : en
Pages : 304
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Book Description
The catastrophic runaway wildfires advancing through North America and other parts of the world are not unprecedented. Fires loomed large once human activity began to warm the climate in the 1820s, leading to an aggressive firefighting strategy that has left many of the continent’s forests too old and vulnerable to the fires that many tree species need to regenerate. Dark Days at Noon provides a broad history of wildfire in North America, from before European contact to the present, in the hopes that we may learn from how we managed fire in the past, and apply those lessons in the future. As people continue to move into forested landscapes to work, play, live, and ignite fires – intentionally or unintentionally – fire has begun to take its toll, burning entire towns, knocking out utilities, closing roads, and forcing the evacuation of hundreds of thousands of people. Fire management in North America requires attention and cooperation from both sides of the border, and many of the most significant fires have taken place at the boundary line. Despite a clear lack of urgency among political leaders, Edward Struzik argues that wildfire science needs to guide the future of fire management, and that those same leaders need to shape public perception accordingly. By explaining how society’s misguided response to fire has led to our current situation, Dark Days at Noon warns of what may happen in the future if we do not learn to live with fire as the continent’s Indigenous Peoples once did.
Author: Daniel Mathews
Publisher: Catapult
ISBN: 1640094660
Category : Nature
Languages : en
Pages : 293
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Book Description
A troubling story of the devastating and compounding effects of climate change in the Western and Rocky Mountain states, told through in–depth reportage and conversations with ecologists, professional forest managers, park service scientists, burn boss, activists, and more. Climate change manifests in many ways across North America, but few as dramatic as the attacks on our western pine forests. In Trees in Trouble, Daniel Mathews tells the urgent story of this loss, accompanying burn crews and forest ecologists as they study the myriad risk factors and refine techniques for saving this important, limited resource. Mathews transports the reader from the exquisitely aromatic haze of ponderosa and Jeffrey pine groves to the fantastic gnarls and whorls of five–thousand–year–old bristlecone pines, from genetic test nurseries where white pine seedlings are deliberately infected with their mortal enemy to the hottest megafire sites and neighborhoods leveled by fire tornadoes or ember blizzards. Scrupulously researched, Trees in Trouble not only explores the devastating ripple effects of climate change, but also introduces us to the people devoting their lives to saving our forests. Mathews also offers hope: a new approach to managing western pine forests is underway. Trees in Trouble explores how we might succeed in sustaining our forests through the challenging transition to a new environment.
Author: Winslow D. Hansen
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 12
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Book Description
Environmental change is accelerating in the 21st century, but how multiple drivers may interact to alter forest resilience remains uncertain. In forests affected by large high-severity disturbances, tree regeneration is a resilience linchpin that shapes successional trajectories for decades. We modeled stands of two widespread western U.S. conifers, Douglas-fir (Pseudotsuga menziesii var. glauca), and lodgepole pine (Pinus contorta var. latifolia), in Yellowstone National Park (Wyoming, USA) to ask (1) What combinations of distance to seed source, fire return interval, and warming-drying conditions cause postfire tree-regeneration failure? (2) If postfire tree regeneration was successful, how does early tree density differ under future climate relative to historical climate? We conducted a stand-level (1 ha) factorial simulation experiment using the individual-based forest process model iLand to identify combinations of fire return interval (11?100 yr), distance to seed source (50?1,000 m), and climate (historical, mid-21st century, late-21st century) where trees failed to regenerate by 30-yr postfire. If regeneration was successful, we compared stand densities between climate periods. Simulated postfire regeneration were surprisingly resilient to changing climate and fire drivers. Douglas-fir regeneration failed more frequently (55%) than lodgepole pine (28% and 16% for nonserotinous and serotinous stands, respectively). Distance to seed source was an important driver of regeneration failure for Douglas-fir and non-serotinous lodgepole pine; regeneration never failed when stands were 50 m from a seed source and nearly always failed when stands were 1 km away. Regeneration of serotinous lodgepole pine only failed when fire return intervals were ?20 yr and stands were far (1 km) from a seed source. Warming climate increased regeneration success for Douglas-fir but did not affect lodgepole pine. If regeneration was successful, postfire density varied with climate. Douglasfir and serotinous lodgepole pine regeneration density both increased under 21st-century climate but in response to different climate variables (growing season length vs. cold limitation). Results suggest that, given a warmer future with larger and more frequent fires, a greater number of stands that fail to regenerate after fires combined with increasing density in stands where regeneration is successful could produce a more coarse-grained forest landscape.
Author: Michael J. Yochim
Publisher: University of New Mexico Press
ISBN: 082636344X
Category : Travel
Languages : en
Pages : 178
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Book Description
In his enthusiastic explorations and fervent writing, Michael J. Yochim “was to Yellowstone what Muir was to Yosemite. . . . Other times, his writing is like that of Edward Abbey, full of passion for the natural world and anger at those who are abusing it,” writes foreword contributor William R. Lowry. In 2013 Yochim was diagnosed with ALS (Lou Gehrig’s disease). While fighting the disease, he wrote Requiem for America’s Best Idea. The book establishes a unique parallel between Yochim’s personal struggle with a terminal illness and the impact climate change is having on the national parks—the treasured wilderness that he loved and to which he dedicated his life. Yochim explains how climate change is already impacting the vegetation, wildlife, and the natural conditions in Olympic, Grand Canyon, Glacier, Yellowstone, and Yosemite National Parks. A poignant and thought-provoking work, Requiem for America’s Best Idea investigates the interactions between people and nature and the world that can inspire and destroy them.
Author: Winslow D. Hansen
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Climate and disturbance regimes are rapidly changing in earth's forests, and these trends are expected to continue through the 21st century. It remains unresolved whether and where forests will absorb increased perturbations without changing qualitatively and where forest resilience might erode. This dissertation provides a foundation to begin addressing these uncertainties. I combined field observation, experiments, and process-based simulation to study effects of changing climate and wildfire on postfire tree regeneration and forest resilience in Yellowstone National Park, the largest intact wildland area of the contiguous United States. Chapter 1 quantifies effects of ecological filters on a colonizing cohort of aspen. These aspen trees established from seed after the 1988 fires and survived at higher elevations than their prefire distribution. I then conducted a long-term field experiment and shorter controlled-environment experiment to determine how temperature and soil moisture consistent with 21st-century projections may alter postfire seedling establishment of two widespread conifers (Chapter 2). In chapters 3 and 4, I used a forest simulation model to test multiple mechanisms of regeneration failure and to explore how suppression may alter 21st-century fire and forests. Long-term study of colonizing aspen demonstrated how wildfire can catalyze rapid shifts in tree-species distributions. Aspen seedlings were initially favored at lower elevations close to their prefire distribution. By 25yrs postfire, aspen was favored to survive at higher elevations, likely due to warming. From the experiments, it appears postfire drought may be a powerful force for change in subalpine forests because regeneration was drastically reduced under hotter-drier conditions. Simulations, where multiple climate-fire drivers could be considered over longer periods, however, indicate the potential for remarkable resilience. Regeneration failure was the exception, not the rule. Suppression of fire also had little impact on 21st-century fire or forests. Collectively, this research demonstrates that multiple streams of quantitative inquiry are necessary to better resolve how changing climate and disturbance will alter forests. Management steps could be taken to bolster vulnerable forests (e.g. reseeding after fires), if mechanisms of change are understood. However, forest-management strategies should not discount the inherent resilience of the system.
Author: Tyler John Hoecker
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Wildfires shaped subalpine forests in the northern US Rocky Mountains for millennia. However, recent climate-driven increases in fire frequency and severity are constraining postfire tree regeneration in forests dominated by fire-sensitive obligate-seeder conifers via reduced propagule pressure and in xeric areas via elevated aridity. Changes in tree regeneration are projected to drive large-scale shifts in the extent and character of future forests, which will cascade to effect critical ecosystem services. This dissertation explored controls on tree regeneration in diverse subalpine forest settings and disturbance contexts and implications for future ecosystem function. I investigated (i) effects of interactions between short-interval fires and topographic position on postfire regeneration using a seed-planting experiment in the Greater Yellowstone Ecosystem (GYE); (ii) consequences of future landscape change for three wildlife species in the GYE using the simulation model iLand and the Maxent algorithm; and (ii) shifts in forest composition and structure after recent fires in Glacier National Park using a field study. Postfire conifer regeneration was low on south-facing aspects affected by high-severity fires at short intervals (30 yrs). Soils on south-facing slopes were 2℗ʻC warmer and >20% drier than north-facing slopes after short-interval burns, and residual fire-killed trees after long-interval fires (>150 yrs) provided microclimate buffering of a similar magnitude. Distribution modeling from 2017-2100 revealed extensive loss of old forest in climate scenarios with substantial warming (RCP 8.5) and drying (HadGEM2-ES). Habitat for three vertebrates (Picoides arcticus, Martes caurina, Tamiasciurus hudsonicus) depended on spatial overlap of persistent forest with suitable climate, which were frequently mismatched. Mesic forests in Glacier remain resilient to fire, but short-interval fire reduced stand density and simplified composition. Postfire regeneration after long-interval fires is dominated by fire-adapted conifers; a second fire erodes the ability of fire-sensitive species to establish. If these shifts persist, the range of mesic conifers is likely to be reduced. Findings indicate climate- and fire-catalyzed changes in forest ecosystems are already emerging in the northern Rockies. Managing forests to preserve historical structure and composition will be increasingly difficult, requiring approaches that direct change toward desired outcomes where possible and accept alternatives where change is unavoidable.
Author: Kerry B. Kemp
Publisher:
ISBN: 9781339321660
Category : Conifers
Languages : en
Pages : 362
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Book Description
As disturbances continue to become more frequent and extensive with climate change, increasing concern is mounting about the ability of dry-mixed conifer forests to recover after wildfire. This concern stems in part from past management strategies, which have impacted the resilience of these forests. As such, future actions that managers propose to deal with climate change impacts will inevitably affect future resilience of these forests. My dissertation examined how climate, disturbance, and landscape variables influenced tree regeneration in dry mixed-conifer forests of the northern Rocky Mountains, using field data combined with downscaled climate data and satellite-derived burn severity data to characterize post-fire seedling regeneration across environmental gradients. Additionally, I examined how forest managers are thinking about climate change impacts and the adaptation measures they are considering to deal with these changes using a combination of breakout group discussions during workshops, interviews and surveys. Distance to a live seed source was one of the most important variables influencing the potential of post-fire regeneration after recent fires. The heterogeneity of the burned mosaic insures that most (> 80%) of the burned landscape is within a distance to live trees for successful regeneration, suggesting high resilience of these forests to recent fire. As climate continue to warm, however, temperature may outweigh the influence of seed source availability on seedling regeneration and the post-fire environment may no longer be favorable for regeneration in much (80%) of the existing dry mixed-conifer zone. Managers desire local climate change predictions that will help them identify thresholds for species resistance or resilience to propose effective management actions. These types of data will help managers move from using current management strategies to using more novel and appropriate techniques to help forests remain resilient to a variety of uncertain future changes. Understanding the diverse and interacting ecological and social factors that influence the recovery or decline of dry mixed-conifer forests will increasingly improve predictions about the future impacts of disturbance, climate change, and management.
Author: Derek Jon Nies Young
Publisher:
ISBN: 9780355969122
Category :
Languages : en
Pages :
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Book Description
Yellow pine and mixed-conifer (YPMC) forests in California are subject to multiple anthropogenic pressures, including fire suppression and climate change. Although YPMC forests historically experienced a high-frequency, low-severity fire regime, fire suppression has resulted in increased fuel loads and has therefore increased the severity of the fires that do occur. Some of the historically dominant tree species in YPMC forests, particularly pines (Pinus spp.), establish primarily following wildfire. However, the increasing extent of severely-burned areas with few nearby seed sources for conifer regeneration has resulted in poor post-fire tree recruitment across large areas. Climate change has the potential to further substantially alter post-fire regeneration patterns. When post-fire tree regeneration is poor, managers often plant tree seedlings in order to speed forest recovery. However, little is known about (a) how natural post-fire tree regeneration patterns may change as climate changes and (b) how appropriate seed sources for post-fire tree seedling plantings should be selected. Further, despite the fact that most studies of climate change impacts rely on modeled climate variables when examining the relationship between climate and vegetation, there has been little critical evaluation of several important climate variables that are increasingly used in ecological analyses. I address these knowledge gaps in this dissertation. In Chapter 1, I evaluate some central assumptions that are made when modeling climatic water balance variables including actual evapotranspiration (AET) and climatic water deficit (CWD). I find that the assumptions can substantially affect both the absolute and relative values of modeled AET and CWD across landscapes—as well as the inferences drawn from ecological analyses that apply the variables—despite the fact that there is no practical means for avoiding the need to make assumptions. Representing the hydrological climate using simple precipitation variables may introduce less bias than using AET and CWD. In Chapter 2, I use recent interannual variation in precipitation to evaluate the sensitivity of post-fire tree recruitment to changes in precipitation patterns. I find that while post-fire recruitment of some conifer species is reduced—and recruitment of shrubs increased—under post-fire drought, the response of post-fire tree seedling species composition to weather variation is constrained by the species composition of the surrounding unburned forest. Forest tree community composition thus may not rapidly shift as climate changes. Finally, in Chapter 3, I test the application of assisted gene flow—the managed relocation of genotypes within the species’ range—in large-scale post-fire restoration plantings. I find that in the short term, under anomalously hot and dry conditions, trees grown from seed collected at elevations below the planting site generally perform as well as, if not significantly better than, trees grown from seed collected near the planting site. However, challenges specific to large-scale restoration projects—in particular, the use of seed collections that are not geographically precise—can complicate selection of appropriate provenances and lead to unexpected results. Overall, the work in this dissertation contributes to increased potential to understand and predict the natural response of forest ecosystems to climate change and to update management practices in response to changes in climate.
