Forests under pressure: The need for interdisciplinary approaches to address forest vulnerability to tree mortality in response to drought PDF Download
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Author: Angelo Rita
Publisher: Frontiers Media SA
ISBN: 2832510914
Category : Science
Languages : en
Pages : 131
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Author: Angelo Rita
Publisher: Frontiers Media SA
ISBN: 2832510914
Category : Science
Languages : en
Pages : 131
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Author: Giovanna Battipaglia
Publisher: Frontiers Media SA
ISBN: 288963860X
Category :
Languages : en
Pages : 240
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Author: Sarah Ann Byer
Publisher:
ISBN: 9780355461763
Category :
Languages : en
Pages :
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A five-year drought in California has led to a significant increase in tree mortality in the Sierra Nevada forests from 2012 to 2016. Landscape level monitoring of forest health and tree dieback is critical for vegetation and disaster management strategies. We examined the capability of multispectral imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) in detecting and explaining the impacts of the recent severe drought in Sierra Nevada forests. Remote sensing metrics were developed to represent baseline forest health conditions and drought stress using time series of MODIS vegetation indices (VIs) and a water index. We used Random Forest algorithms, trained with forest aerial detection surveys data, to detect tree mortality based on the remote sensing metrics and topographical variables. Map estimates of tree mortality demonstrated that our two-stage Random Forest models were capable of detecting the spatial patterns and severity of tree mortality, with an overall producer’s accuracy of 96.3% for the classification Random Forest (CRF) and a RMSE of 7.19 dead trees per acre for the regression Random Forest (RRF). The overall omission errors of the CRF ranged from 19% for the severe mortality class to 27% for the low mortality class. Interpretations of the models revealed that forests with higher productivity preceding the onset of drought were more vulnerable to drought stress and, consequently, more likely to express tree mortality. This method highlights the importance of incorporating baseline forest health data and measurements of drought stress in understanding forest response to severe drought.
Author: Achim Bräuning
Publisher: Frontiers Media SA
ISBN: 2889451925
Category :
Languages : en
Pages : 468
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Book Description
Trees are among the longest-living organisms. They are sensitive to extreme climatic events and document the effects of environmental changes in form of structural modifications of their tissues. These modifications represent an integrated signal of complex biological responses enforced by the environment. For example, temporal change in stem increment integrates multiple information of tree performance, and wood anatomical traits may be altered by climatic extremes or environmental stress. Recent developments in preparative tools and computational image analysis enable to quantify changes in wood anatomical features, like vessel density or vessel size. Thus, impacts on their functioning can be related to climatic forcing factors. Similarly, new developments in monitoring (cambial) phenology and mechanistic modelling are enlightening the interrelationships between environmental factors, wood formation and tree performance and mortality. Quantitative wood anatomy is a reliable indicator of drought occurrence during the growing season, and therefore has been studied intensively in recent years. The variability in wood anatomy not only alters the biological and hydraulic functioning of a tree, but may also influence the technological properties of wood, with substantial impacts in forestry. On a larger scale, alterations of sapwood and phloem area and their ratios to other functional traits provide measures to detect changes in a tree’s life functions, and increasing risk of drought-induced mortality with possible impacts on hydrological processes and species composition of plant communities. Genetic variability within and across populations is assumed to be crucial for species survival in an unpredictable future world. The magnitude of genetic variation and heritability of adaptive traits might define the ability to adapt to climate change. Is there a relation between genetic variability and resilience to climate change? Is it possible to link genetic expression and climate change to obtain deeper knowledge of functional genetics? To derive precise estimates of genetic determinism it is important to define adaptive traits in wood properties and on a whole-tree scale. Understanding the mechanisms ruling these processes is fundamental to assess the impact of extreme climate events on forest ecosystems, and to provide realistic scenarios of tree responses to changing climates. Wood is also a major carbon sink with a long-term residence, impacting the global carbon cycle. How well do we understand the link between wood growth dynamics, wood carbon allocation and the global carbon cycle? Papers contribution to this Research Topic will cover a wide range of ecosystems. However, special relevance will be given to Mediterranean-type areas. These involve coastal regions of four continents, making Mediterranean-type ecosystems extremely interesting for investigating the potential impacts of global change on growth and for studying responses of woody plants under extreme environmental conditions. For example, the ongoing trend towards warmer temperatures and reduced precipitation can increase the susceptibility to fire and pests. The EU-funded COST Action STREeSS (Studying Tree Responses to extreme Events: a SynthesiS) addresses such crucial tree biological and forest ecological issues by providing a collection of important methodological and scientific insights, about the current state of knowledge, and by opinions for future research needs.
Author: Jeffrey Lauder
Publisher:
ISBN:
Category :
Languages : en
Pages : 334
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Book Description
Climate change is expected to drive shifts in forest species distribution to track ideal climatic conditions. The relative capacity for a tree species to persist under climatic stress is dependent on life history traits, such as growth, survival, and reproduction. Trees that produce large amounts of seed may be better able to colonize newly suitable habitats, while those that survive stress at current locations may persist longer than nearby competitors. These traits each represent distinct resource sinks, however. What remains unknown is how physiological modification in response to drought influences both survival and reproductive capacity. I analyzed growth, tree ring anatomy, and reproductive capacity in Pinus ponderosa and P. jeffreyi in the Sierra Nevada mountains of California, where the unprecedented 2012-2016 drought led to large-scale forest mortality. I found that trees that died during drought unexpectedly exhibited anatomical traits thought to confer drought tolerance, such as thicker walls in water-conducting xylem cells. Under drought, trees close stomata (pores in their leaf surface involved in gas exchange) to limit water loss, but at the expense of carbon (C) uptake. This leads to a theoretical expectation of C depletion in drought-stressed trees, particularly during prolonged (i.e., multi-year) drought. While direct evidence of this "C-starvation" has not been recorded in nature, my results point to a potential mechanism of the impact of C depletion on mortality. The sampled trees also experienced a high level of bark beetle (Dendroctonus spp.) attack, which is typically defended against in trees via the production of C-rich resin and other chemical defenses. Drought appears to have weakened sampled trees, and excessive allocation of available resources to drought defense may have depleted reserves necessary for fending off beetle attack. To quantify potential tradeoffs between drought defense and reproduction, I developed a novel technique to measure total lignin (a C-expensive material involved in xylem cell wall thickening) in tree rings, and found that trees that died had higher lignin content than living trees. To further explore these patterns, I modeled likelihood of tree mortality as a function of tree ring width (growth), xylem anatomy, competition, and climate. I first compared multiple commonly used drought metrics with ring widths from>800 trees from across the Sierra Nevada and found that drought metric choice influences interpretation of drought impacts. I then showed that trees that grew not only thicker-walled xylem cells, but also more variable growth rings and variable cells between years were more likely to die. Trees that grew the same amount each year, or grew rings with relatively constant xylem cell diameters and wall thicknesses, were more likely to survive drought, counter to hypothesized tradeoffs between growth and reproduction during drought. Finally, cone counts of measured trees show that ring width (growth) was the primary determinant of reproductive capacity, with trees that grew more producing more cones. These results demonstrate that tree response to drought is a function of variation in xylem anatomy and ring width, with the mechanism of mortality being associated with C depletion. Trees that are less responsive to climate and maintain fairly constant growth appear to be most likely to survive prolonged drought, and trees that grow large rings (with low variance between years) are more likely to reproduce. These results improve our understanding of whole-forest response to future climate change by demonstrating the importance of both cellular scale (xylem anatomy) and forest-scale (drought metrics and competition) variation in influencing drought-induced forest mortality
Author: Riikka Linnakoski
Publisher: Frontiers Media SA
ISBN: 2889633071
Category :
Languages : en
Pages : 174
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Author: James M. Vose
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 302
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Book Description
This assessment provides input to the reauthorized National Integrated Drought Information System (NIDIS) and the National Climate Assessment (NCA), and it establishes the scientific foundation needed to manage for drought resilience and adaptation. Focal areas include drought characterization; drought impacts on forest processes and disturbances such as insect outbreaks and wildfire; and consequences for forest and rangeland values. Drought can be a severe natural disaster with substantial social and economic consequences. Drought becomes most obvious when large-scale changes are observed; however, even moderate drought can have long-lasting impacts on the structure and function of forests and rangelands without these obvious large-scale changes. Large, stand-level impacts of drought are already underway in the West, but all U.S. forests are vulnerable to drought. Drought-associated forest disturbances are expected to increase with climatic change. Management actions can either mitigate or exacerbate the effects of drought. A first principal for increasing resilience and adaptation is to avoid management actions that exacerbate the effects of current or future drought. Options to mitigate drought include altering structural or functional components of vegetation, minimizing drought-mediated disturbance such as wildfire or insect outbreaks, and managing for reliable flow of water.
Author: Derek Eamus
Publisher: Cambridge University Press
ISBN: 1316666549
Category : Science
Languages : en
Pages :
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Book Description
Understanding ecosystem structure and function requires familiarity with the techniques, knowledge and concepts of the three disciplines of plant physiology, remote sensing and modelling. This is the first textbook to provide the fundamentals of these three domains in a single volume. It then applies cross-disciplinary insights to multiple case studies in vegetation and landscape science. A key feature of these case studies is an examination of relationships among climate, vegetation structure and vegetation function, to address fundamental research questions. This book is for advanced students and researchers who need to understand and apply knowledge from the disciplines of plant physiology, remote sensing and modelling. It allows readers to integrate and synthesise knowledge to produce a holistic understanding of the structure, function and behaviour of forests, woodlands and grasslands.
Author: Food and Agriculture Organization of the United Nations
Publisher: Food & Agriculture Org.
ISBN: 9251311382
Category : Technology & Engineering
Languages : en
Pages : 84
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Book Description
Until recently, considerably more attention was paid to using forests to mitigate climate change, through the absorption of carbon dioxide (CO2) from the atmosphere, than there was on considering the need to adapt forests to avoid the worst effects that climate change could have on them. The switch from a mitigation-heavy approach to one that considers adaptation in a more balanced manner underscores the need to have approaches to assess the vulnerability of forests to climate change. One reason for this more balanced focus may be due to the realization by the broader public, governmental organizations and the forest science community that the climate change that has already occurred is permanent in human terms, because it takes centuries for much of the CO2 emitted from fossil fuel sources to be removed from the atmosphere. There are already substantial impacts that are being seen in the world’s forests. These impacts are certain to continue increasing until CO2 emissions drop to lower levels. For that reason, adaptation of the world’s forests requires attention. The approaches to assessing vulnerability can be categorized according to the focus they each provide. Contextual vulnerability addresses current issues of climate and is usually evaluated using participatory techniques with people who live in, or work with, forests. Outcome vulnerability looks at the biophysical vulnerability of forests; it is often used to assess the cause-and-effect of climate change on a biological system. Vulnerability assessments can be highly technical and quantitative, using advanced computer programs and geographic information systems, or they can be based on social science approaches to obtaining qualitative information from people.
Author: Andrea Ghirardo
Publisher: Frontiers Media SA
ISBN: 2889744876
Category : Science
Languages : en
Pages : 136
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