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Author: Wallis L. Robinson
Publisher:
ISBN:
Category : Conifers
Languages : en
Pages : 102
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Book Description
California is experiencing increasingly severe and prolonged droughts, which are contributing to changes in tree stress and forest mortality. Many factors affect a tree’s drought response, including competition, climate, and site and tree characteristics. Northern California provides a suitable venue to explore the effects of these factors, as it spans a variety of site conditions and includes habitat for conifers with different adaptations and requirements. This study used annual 13C discrimination and growth metrics to assess differences in drought resistance and resilience in conifers adapted to coastal and montane ranges at both wet and dry sites, as well as differences in environmental factors that affect species-level drought responses. Coastal species (Sitka spruce and western hemlock) were more sensitive to drought than montane species (Shasta fir, Brewer spruce, sugar pine, and western white pine). Coastal trees were more sensitive to drought at dry sites than wet sites. Montane species exhibited smaller differences in drought resistance between wet and dry conditions, but varied in factors contributing to physiological response among species. This study suggests that in most situations, conifers in northern California weathered the 2012 – 2016 drought with reasonably high resistance and resilience. However, many of these trees may be at risk for increased stress and mortality in the event of longer and/or more frequent, severe drought. Management strategies for conifers in one region may not be suitable for the same species in another region, and the effects of competition and community composition on drought resistance and resilience must be carefully considered.
Author: Wallis L. Robinson
Publisher:
ISBN:
Category : Conifers
Languages : en
Pages : 102
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Book Description
California is experiencing increasingly severe and prolonged droughts, which are contributing to changes in tree stress and forest mortality. Many factors affect a tree’s drought response, including competition, climate, and site and tree characteristics. Northern California provides a suitable venue to explore the effects of these factors, as it spans a variety of site conditions and includes habitat for conifers with different adaptations and requirements. This study used annual 13C discrimination and growth metrics to assess differences in drought resistance and resilience in conifers adapted to coastal and montane ranges at both wet and dry sites, as well as differences in environmental factors that affect species-level drought responses. Coastal species (Sitka spruce and western hemlock) were more sensitive to drought than montane species (Shasta fir, Brewer spruce, sugar pine, and western white pine). Coastal trees were more sensitive to drought at dry sites than wet sites. Montane species exhibited smaller differences in drought resistance between wet and dry conditions, but varied in factors contributing to physiological response among species. This study suggests that in most situations, conifers in northern California weathered the 2012 – 2016 drought with reasonably high resistance and resilience. However, many of these trees may be at risk for increased stress and mortality in the event of longer and/or more frequent, severe drought. Management strategies for conifers in one region may not be suitable for the same species in another region, and the effects of competition and community composition on drought resistance and resilience must be carefully considered.
Author: Gabriel J. Roletti
Publisher:
ISBN:
Category : Conifers
Languages : en
Pages : 0
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Book Description
Frequent and intense drought events are rapidly altering stand dynamics in western North American forests. Climate, competition, and site characteristics can affect the growth responses of individual trees to drought stress. The ecological and geographical diversity of northern California provides a unique opportunity to measure these responses across species, habitat types, and levels of competitive pressure. This study used dendrochronological techniques and linear mixed-effects models to assess growth responses to drought in four montane and two coastal conifer species across 54 study sites (nine sites per species and 540 trees total) in northern California. Growth was evaluated from 2002-2018 and the drought period was from 2013-2015. There were significant differences among species and environments (coastal or montane) in growth, drought resistance and resilience, and annual latewood proportion. Growth in montane species was generally positively correlated with moisture availability (Palmer Drought Severity Index) and negatively correlated with competitive pressure. The four montane species maintained relatively stable drought resistance, resilience, and latewood proportion across the study period. In contrast, growth in the two coastal species was influenced more by tree size and crown ratio than moisture availability or competition. As the 2013-2015 drought proceeded, coastal species showed marked reductions in drought resistance and resilience and increases in latewood proportion. The six focal species endured this drought in northern California with reasonably high resistance and resilience. However, the lower resistance observed in coastal species suggests that they may be at risk for increased stress and mortality in the event of more severe, prolonged, and/or frequent droughts.
Author: Zachary J. Wenderott
Publisher:
ISBN:
Category : Abies concolor
Languages : en
Pages : 54
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Book Description
Forests throughout much of the western United States are experiencing increasing climatic variability, often resulting in decreased forest productivity and elevated likelihood of tree mortality. Severe drought, such California’s recent 2012-2015 drought, are projected to increase in intensity, frequency, and severity throughout much of this region in coming years. Forest management has long relied on prescribed fire and mechanical thinning to reduce fuel loads and ameliorate potential fire hazards. These treatments may also have the ability to reduce stand density, alleviate competitive pressures, and allow residual trees access to critical resources during periods of extreme stress. Utilizing a long-term National Park Service fire monitoring program allowed us to analyze the effects of prescribed fire treatments on radial growth response in a mixed-conifer forest of northern California. Tree core samples were collected and analyzed from 136 yellow pine (ponderosa pine (Pinus ponderosa) and Jeffrey pine (Pinus jeffreyi)) and 136 white fir (Abies concolor) trees within Lassen Volcanic National Park. Tree-ring data was used to describe factors that influenced tree growth during the locally identified low moisture period (2007 - 2015), as well the potential ability of treatments to improve tree drought resistance and subsequent recovery. Radial growth was positively associated with crown ratio and annual precipitation totals, and negatively associated with localized competitive pressures. Within treatment sites, where stand density was effectively reduced, trees showed improved annual radial growth rates. This appeared to be generally driven by overall treatment intensity and its ability to alter forest density. White fir exhibited a stronger growth response to competitive pressures compared to yellow pine; however, radial growth rates were generally driven by the same factors. Drought resistance did not appear to be strongly correlated with competitive pressures, though drought recovery was slightly associated with increased competitive levels. Findings suggests future forest management techniques, such as prescribed fire and thinning, may be beneficial in terms of reducing competitive pressures and improving radial tree growth among residual trees during future more severe drought.
Author: Michael J. Vernon
Publisher:
ISBN:
Category : Douglas fir
Languages : en
Pages : 33
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Book Description
Climate change is predicted to increase the frequency, duration, and severity of drought events across many bioregions. Forest managers have two active management techniques to promote resistance and resilience to drought: prescribed fire and mechanical thinning. Generally applied to reduce fuels and fire hazard, treated areas may also reduce competition for resources that may improve tree-growth during drought and reduce mortality. The recent severe and prolonged drought in California allowed me to investigate the effects of climate stress and fuel treatments on tree growth responses in a dry mixed-conifer forest ecosystem. To assess tree-growth responses to fuel treatments during severe drought I collected and analyzed tree core samples from 300 ponderosa pine (Pinus ponderosa) and Douglas-fir (Pseudotsuga menziesii) trees in the mixed-conifer forests of Whiskeytown National Recreation Area in northern California. Tree-ring data was used to investigate factors that influenced tree-growth during the study period (2008-2015). Growth was positively associated with crown ratio and negatively associated with local competition and climate water deficit (1-yr lag). Douglas-fir generally had higher annual growth than ponderosa pine, though factors affecting growth were the same for both species. Overall, trees in thinning treatments had higher drought resistance compared to untreated stands. Drought resistance was significantly higher in treated stands compared to untreated stands during both years of extreme drought (2014-2015) for ponderosa pine but only one year (2014) for Douglas-fir. This information can help land managers decide on forest management practices that may enhance forest resistance to future drought events.
Author: Christina (Naomi) Tague
Publisher: Frontiers Media SA
ISBN: 2889668614
Category : Science
Languages : en
Pages : 185
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Book Description
Author: Chance C. Callahan
Publisher:
ISBN:
Category : Conifers
Languages : en
Pages : 48
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Book Description
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.
Author: Harold Mooney
Publisher: Univ of California Press
ISBN: 0520278801
Category : Nature
Languages : en
Pages : 1008
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Book Description
This long-anticipated reference and sourcebook for CaliforniaÕs remarkable ecological abundance provides an integrated assessment of each major ecosystem typeÑits distribution, structure, function, and management. A comprehensive synthesis of our knowledge about this biologically diverse state, Ecosystems of California covers the state from oceans to mountaintops using multiple lenses: past and present, flora and fauna, aquatic and terrestrial, natural and managed. Each chapter evaluates natural processes for a specific ecosystem, describes drivers of change, and discusses how that ecosystem may be altered in the future. This book also explores the drivers of CaliforniaÕs ecological patterns and the history of the stateÕs various ecosystems, outlining how the challenges of climate change and invasive species and opportunities for regulation and stewardship could potentially affect the stateÕs ecosystems. The text explicitly incorporates both human impacts and conservation and restoration efforts and shows how ecosystems support human well-being. Edited by two esteemed ecosystem ecologists and with overviews by leading experts on each ecosystem, this definitive work will be indispensable for natural resource management and conservation professionals as well as for undergraduate or graduate students of CaliforniaÕs environment and curious naturalists.
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: Susan G. Conard
Publisher:
ISBN:
Category : Vegetation management
Languages : en
Pages : 16
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Book Description
Author: Ellen Hanak
Publisher: Public Policy Instit. of CA
ISBN: 1582131414
Category : Business & Economics
Languages : en
Pages : 500
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Book Description
