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Author:
Publisher:
ISBN:
Category : Forest declines
Languages : en
Pages : 0
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Book Description
Climate change is projected to bring more frequent and prolonged droughts, causing widespread forest die-off. Identifying tree mortality over large spatial extents in response to the most recent California drought will help forest managers and conservationists understand where there may be a greater likelihood of future die-offs. In order to find more at-risk areas, this study evaluated how interacting site-specific topographic, climate, substrate, and stand characteristics mediated tree mortality in the Central Sierra Nevada during the 2012-2016 drought. The author used lidar and hyperspectral imagery provided by the National Ecological Observatory Network to identify individual dead trees using the Random Forest classification method and created a Random Forest Regression model to assess site-specific environmental variables that had a greater influence on tree mortality. The results show that the most influential variables were tree height, density, and elevation. Results also found higher mortality rates in pines and oaks, meaning further widespread die-off of these trees could reduce forest productivity, increase fire hazard risk, and drive a shift in community composition over the long-term. This study provides a finer resolution mapping of tree mortality over the research area than was reported by the USFS Aerial Detection Survey. Due to the confounding evidence regarding the relative influence of environmental factors on tree mortality during droughts, these results provide robust information to help maintain these changing forests in a climate-informed manner. Because this study is site-specific, more research is needed to assess how environmental factors mediate drought-induced mortality in other regions also projected to have more intense droughts as a result of climate change.
Author:
Publisher:
ISBN:
Category : Forest declines
Languages : en
Pages : 0
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Book Description
Climate change is projected to bring more frequent and prolonged droughts, causing widespread forest die-off. Identifying tree mortality over large spatial extents in response to the most recent California drought will help forest managers and conservationists understand where there may be a greater likelihood of future die-offs. In order to find more at-risk areas, this study evaluated how interacting site-specific topographic, climate, substrate, and stand characteristics mediated tree mortality in the Central Sierra Nevada during the 2012-2016 drought. The author used lidar and hyperspectral imagery provided by the National Ecological Observatory Network to identify individual dead trees using the Random Forest classification method and created a Random Forest Regression model to assess site-specific environmental variables that had a greater influence on tree mortality. The results show that the most influential variables were tree height, density, and elevation. Results also found higher mortality rates in pines and oaks, meaning further widespread die-off of these trees could reduce forest productivity, increase fire hazard risk, and drive a shift in community composition over the long-term. This study provides a finer resolution mapping of tree mortality over the research area than was reported by the USFS Aerial Detection Survey. Due to the confounding evidence regarding the relative influence of environmental factors on tree mortality during droughts, these results provide robust information to help maintain these changing forests in a climate-informed manner. Because this study is site-specific, more research is needed to assess how environmental factors mediate drought-induced mortality in other regions also projected to have more intense droughts as a result of climate change.
Author: Alisha
Publisher:
ISBN: 9783384262271
Category :
Languages : en
Pages : 0
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Author:
Publisher:
ISBN: 9781267767363
Category :
Languages : en
Pages : 198
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Book Description
Themontane mixed-conifer forests of San Diego County are currently experiencing extensive tree mortality, which is defined as dieback where whole stands are affected. This mortality is likely the result of the complex interaction of many variables, such as altered fire regimes, climatic conditions such as drought, as well as forest pathogens and past management strategies. Conifer tree mortality and its spatial pattern and change over time were examined in three components. In component 1, two remote sensing approaches were compared for their effectiveness in delineating dead trees, a spatial contextual approach and an OBIA (object based image analysis) approach, utilizing various dates and spatial resolutions of airborne image data.For each approach transforms and masking techniques were explored, which were found to improve classifications, and an object-based assessment approach was tested. In component 2, dead tree maps produced by the most effective techniques derived from component 1 were utilized for point pattern and vector analyses to further understand spatio-temporal changes in tree mortality for the years 1997, 2000, 2002, and 2005 for three study areas: Palomar, Volcan and Laguna mountains. Plot-based fieldwork was conducted to further assess mortality patterns. Results indicate that conifer mortality was significantly clustered, increased substantially between 2002 and 2005, and was non-random with respect to tree species and diameter class sizes. In component 3, multiple environmental variables were used in Generalized Linear Model (GLM-logistic regression) and decision tree classifier model development, revealing the importance of climate and topographic factors such as precipitation and elevation, in being able to predict areas of high risk for tree mortality. The results from this study highlight the importance of multi-scale spatial as well as temporal analyses, in order to understand mixed-conifer forest structure, dynamics, and processes of decline, which can lead to more sustainable management of forests with continued natural and anthropogenic disturbance.
Author: Seth Richard Gorelik
Publisher:
ISBN: 9781392023969
Category : Droughts
Languages : en
Pages : 0
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Book Description
In the early 2000s, severe drought and beetle outbreaks brought on by climate change led to extensive pinon pine mortality in northern New Mexico. Mapping pinon mortality is critical for understanding and monitoring impacts to ecosystem services. I used Landsat imagery, finer-resolution reference data, and statistical modeling to predict absolute within-pixel percent tree mortality (PTM). I found that a balanced random forest model had the highest accuracy. I applied the model to a time series and assessed spatial and temporal patterns of the estimated tree mortality. Pixels within the study area experienced a mean of 42.3% tree mortality, a mean duration of 3 years, and a mean rate of mortality of 22% per year. From 1987 to 2009, cumulative tree mortality reached 67,190 ha, or 19.8% of the woodland area, the equivalent of 48.9 million pinons. These results demonstrate the capability of mapping drought-induced PTM using a Landsat time series.
Author: Alison Kelly Macalady
Publisher:
ISBN:
Category : Global warming
Languages : en
Pages : 212
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Book Description
Forests play an important role in the earth system, regulating climate, maintaining biodiversity, and provisioning human communities with water, food and fuel. Interactions between climate and forest dynamics are not well constrained, and high uncertainty characterizes projections of global warming impacts on forests and associated ecosystem services. Recently observed tree mortality and forest die-off forewarn an acceleration of forest change with rising temperature and increased drought. However, the processes leading to tree death during drought are poorly understood, limiting our ability to anticipate future forest dynamics. The objective of this dissertation was to improve understanding of drought-associated tree mortality through literature synthesis and tree-ring studies on trees that survived and died during droughts in the southwestern USA. Specifically, this dissertation 1) documented global tree mortality patterns and identified emerging trends and research gaps; 2) quantified relationships between growth, climate, competition and mortality of piñon pine during droughts in New Mexico; 3) investigated tree defense anatomy as a potentially key element in piñon avoidance of death; and, 4) characterized the climate sensitivity of piñon resin ducts in order to gain insight into potential trends in tree defenses with climate variability and change. There has been an increase in studies reporting tree mortality linked to drought, heat, and the associated activity of insects and pathogens. Cases span the forested continents and occurred in water, light and temperature-limited forests. We hypothesized that increased tree mortality may be an emerging global phenomenon related to rising temperatures and drought (Appendix A). Recent radial growth was 53% higher on average in piñon that survived versus died during two episodes of drought-associated mortality, and statistical models of mortality risk based on average growth, growth variability, and abrupt growth changes correctly classified the status of ~70% of trees. Climate responses and competitive interactions partly explained growth differences between dying and surviving trees, with muted response to wet/cool conditions and enhanced sensitivity to competition from congeners linked to growth patterns associated with death. Discrimination and validation of models of mortality risk varied widely across sites and drought events, indicating shifting growth-mortality relationships and differences in mortality processes across space and time (Appendix B). Pre-formed defense anatomy is strongly associated with piñon survivorship over a range of sites and stand conditions. Models of mortality risk that account for both growth and resin duct attributes had≈1019 more support than models that contained only growth. The greatest improvement in classification was among trees from the 2000s drought, suggesting an enhanced role for tree defense allocation and/or bark beetle activity during recent warm versus historic cool drought. Accounting for defense characteristics and growth-defense allocation is likely to be important for improving representation of drought-associated mortality (Appendix C). Piñon resin duct chronologies contain climate responses that are coherent and distinct from those of radial growth. Growth responds positively and strongly to previous fall and current winter precipitation, and negatively to late spring and early summer temperature. A relatively equal positive resin duct response to winter precipitation and positive response to mid-to-late summer drought suggests that changes in climate will affect tree defense anatomy in complex ways, with the outcome determined by seasonal changes in precipitation and temperature (Appendix D).
Author: R. Tognetti
Publisher:
ISBN: 9788303080769
Category : Forests and forestry
Languages : en
Pages : 0
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This open access book offers a cross-sectoral reference for both managers and scientists interested in climate-smart forestry, focusing on mountain regions. It provides a comprehensive analysis on forest issues, facilitating the implementation of climate objectives. This book includes structured summaries of each chapter. Funded by the EU's Horizon 2020 programme, CLIMO has brought together scientists and experts in continental and regional focus assessments through a cross-sectoral approach, facilitating the implementation of climate objectives. CLIMO has provided scientific analysis on issues including criteria and indicators, growth dynamics, management prescriptions, long-term perspectives, monitoring technologies, economic impacts, and governance tools.
Author: Henry L. Short
Publisher:
ISBN:
Category : Forest management
Languages : en
Pages : 16
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Book Description
Author: National Academies of Sciences, Engineering, and Medicine
Publisher: National Academies Press
ISBN: 0309492432
Category : Science
Languages : en
Pages : 29
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Book Description
We live on a dynamic Earth shaped by both natural processes and the impacts of humans on their environment. It is in our collective interest to observe and understand our planet, and to predict future behavior to the extent possible, in order to effectively manage resources, successfully respond to threats from natural and human-induced environmental change, and capitalize on the opportunities â€" social, economic, security, and more â€" that such knowledge can bring. By continuously monitoring and exploring Earth, developing a deep understanding of its evolving behavior, and characterizing the processes that shape and reshape the environment in which we live, we not only advance knowledge and basic discovery about our planet, but we further develop the foundation upon which benefits to society are built. Thriving on Our Changing Planet: A Decadal Strategy for Earth Observation from Space (National Academies Press, 2018) provides detailed guidance on how relevant federal agencies can ensure that the United States receives the maximum benefit from its investments in Earth observations from space, while operating within realistic cost constraints. This short booklet, designed to be accessible to the general public, provides a summary of the key ideas and recommendations from the full decadal survey report.
Author: Brian D. Wardlow
Publisher: CRC Press
ISBN: 1439835578
Category : Science
Languages : en
Pages : 487
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Book Description
Remote Sensing of Drought: Innovative Monitoring Approaches presents emerging remote sensing-based tools and techniques that can be applied to operational drought monitoring and early warning around the world. The first book to focus on remote sensing and drought monitoring, it brings together a wealth of information that has been scattered throughout the literature and across many disciplines. Featuring contributions by leading scientists, it assembles a cross-section of globally applicable techniques that are currently operational or have potential to be operational in the near future. The book explores a range of applications for monitoring four critical components of the hydrological cycle related to drought: vegetation health, evapotranspiration, soil moisture and groundwater, and precipitation. These applications use remotely sensed optical, thermal, microwave, radar, and gravity data from instruments such as AMSR-E, GOES, GRACE, MERIS, MODIS, and Landsat and implement several advanced modeling and data assimilation techniques. Examples show how to integrate this information into routine drought products. The book also examines the role of satellite remote sensing within traditional drought monitoring, as well as current challenges and future prospects. Improving drought monitoring is becoming increasingly important in addressing a wide range of societal issues, from food security and water scarcity to human health, ecosystem services, and energy production. This unique book surveys innovative remote sensing approaches to provide you with new perspectives on large-area drought monitoring and early warning.
Author: Lalit Kumar
Publisher: MDPI
ISBN: 3039212095
Category : Science
Languages : en
Pages : 264
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Book Description
Above ground biomass has been listed by the Intergovernmental Panel on Climate Change as one of the five most prominent, visible, and dynamic terrestrial carbon pools. The increased awareness of the impacts of climate change has seen a burgeoning need to consistently assess carbon stocks to combat carbon sequestration. An accurate estimation of carbon stocks and an understanding of the carbon sources and sinks can aid the improvement and accuracy of carbon flux models, an important pre-requisite of climate change impact projections. Based on 15 research topics, this book demonstrates the role of remote sensing in quantifying above ground biomass (forest, grass, woodlands) across varying spatial and temporal scales. The innovative application areas of the book include algorithm development and implementation, accuracy assessment, scaling issues (local–regional–global biomass mapping), and the integration of microwaves (i.e. LiDAR), along with optical sensors, forest biomass mapping, rangeland productivity and abundance (grass biomass, density, cover), bush encroachment biomass, and seasonal and long-term biomass monitoring.
