Synthesis of Research Into the Long-term Outlook for Sierra Nevada Forests Following the Current Bark Beetle Epidemic PDF Download
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Category :
Languages : en
Pages : 27
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This paper summarizes the 2012-2017 bark beetle epidemic in the Sierra Nevada and its implications for long-term changes in tree species composition and forest structure. Preliminary plot and landscape-scale data are reviewed, showing higher levels of mortality for pine species and greater impacts in the southern Sierra Nevada compared to the northern portions of the range. The federal government owns approximately three quarters of the forested area impacted by high levels of tree morality, with the remainder of the land controlled by nonindustrial (18%) and industrial (6%) ownerships. The accumulation of dead and downed fuel and standing dead trees is expected to increase fire intensity and severity, and pose significant hazards for fire control efforts. Potential long-term changes in Sierra Nevada forest composition were explored with a GIS analysis conducted for the Sierra National Forest, located in the southern Sierra. GIS layers included very high fire threat, aspect, high tree mortality, topographic position classification, and climatic exposure. A factor of one was assigned to each parameter (i.e., no weighting for any of the variables). The modeling showed that 4% of the Sierra National Forest is at very high risk for type conversion from mixed conifer to shrublands, and 12% is at high risk. This information can inform landowners regarding the general locations where successful reforestation will be most challenging, as well as illustrate the scale of concern for one national forest in the southern Sierra Nevada. Changes to disturbance regimes, continuing land use changes, and climate change with associated species shifts pose significant challenges for maintaining healthy and resilient forests in the Sierra Nevada. Significant unknowns exist regarding the future species composition for vast portions of this region, but type conversions from mixed conifer to shrublands or oak/grass/woodland appear likely for some areas. Recommended best management practices focus on reducing tree densities, achieving successful reforestation, and using adaptive management in the face of currently unknown future changes in growing conditions. With the exception of the bark beetle epidemic in southern California in the early 2000s, lessons learned from other locations in western North America that have had sustained bark beetle epidemics in the past decade are not directly applicable to Sierra Nevada, with its Mediterranean climate, complex topography, and mixed-conifer forests. For these reasons, ongoing research efforts to characterize and understand tree mortality drivers and changes in forest structure and composition in the Sierra Nevada are extremely important.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 27
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Book Description
This paper summarizes the 2012-2017 bark beetle epidemic in the Sierra Nevada and its implications for long-term changes in tree species composition and forest structure. Preliminary plot and landscape-scale data are reviewed, showing higher levels of mortality for pine species and greater impacts in the southern Sierra Nevada compared to the northern portions of the range. The federal government owns approximately three quarters of the forested area impacted by high levels of tree morality, with the remainder of the land controlled by nonindustrial (18%) and industrial (6%) ownerships. The accumulation of dead and downed fuel and standing dead trees is expected to increase fire intensity and severity, and pose significant hazards for fire control efforts. Potential long-term changes in Sierra Nevada forest composition were explored with a GIS analysis conducted for the Sierra National Forest, located in the southern Sierra. GIS layers included very high fire threat, aspect, high tree mortality, topographic position classification, and climatic exposure. A factor of one was assigned to each parameter (i.e., no weighting for any of the variables). The modeling showed that 4% of the Sierra National Forest is at very high risk for type conversion from mixed conifer to shrublands, and 12% is at high risk. This information can inform landowners regarding the general locations where successful reforestation will be most challenging, as well as illustrate the scale of concern for one national forest in the southern Sierra Nevada. Changes to disturbance regimes, continuing land use changes, and climate change with associated species shifts pose significant challenges for maintaining healthy and resilient forests in the Sierra Nevada. Significant unknowns exist regarding the future species composition for vast portions of this region, but type conversions from mixed conifer to shrublands or oak/grass/woodland appear likely for some areas. Recommended best management practices focus on reducing tree densities, achieving successful reforestation, and using adaptive management in the face of currently unknown future changes in growing conditions. With the exception of the bark beetle epidemic in southern California in the early 2000s, lessons learned from other locations in western North America that have had sustained bark beetle epidemics in the past decade are not directly applicable to Sierra Nevada, with its Mediterranean climate, complex topography, and mixed-conifer forests. For these reasons, ongoing research efforts to characterize and understand tree mortality drivers and changes in forest structure and composition in the Sierra Nevada are extremely important.
Author: Alexis Bernal
Publisher:
ISBN:
Category : Bark beetles
Languages : en
Pages : 96
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Long-term trends of tree mortality have increased over the last several decades, coinciding with above-average temperatures, high climatic water deficits, and bark beetle outbreaks. With the anticipation that drought and bark beetles may increase with climate change, uncertainty exists over the appropriate treatments that could ensure the future sustainability of forest resources and the ecosystem services that forests provide. Conventional thinning treatments are used to reduce stand density, with the assumption that reductions in competition can alleviate drought stress and enable trees to resist bark beetle attack. Alternative thinning treatments may also reduce stand density, but have a greater focus on increasing spatial heterogeneity. Variable density thinning is a management method intended to mimic the spatial heterogeneity that was present in mixed-conifer forests prior to logging and fire exclusion. Although the added benefits of increasing spatial heterogeneity include biodiversity, wildlife, recreation, and restoration, information is lacking on the effects that these treatments have on tree resistance to disturbances. Since 2012, the Sierra Nevada experienced widespread tree mortality coinciding with severe drought conditions and bark beetle outbreak. This provided a unique opportunity to explore the mechanisms driving bark beetle-associated mortality following variable density thinning treatments in the central Sierra Nevada. Using dendrochronological methods, we modeled the relationship between drought resistance and bark beetle-associated mortality to evaluate if reductions in competition enhance tree resistance to bark beetles. We also determined if structural elements within variable density thinning treatments influenced the level and spatial pattern of bark beetle-associated mortality. By exploring these relationships, our findings could provide a greater understanding on the underlying mechanisms that drive mortality to disturbances and also provide information to help develop prescriptions for enhancing resistance to drought and bark beetles.
Author: Pablo Gregorini
Publisher: Frontiers Media SA
ISBN: 288976463X
Category : Technology & Engineering
Languages : en
Pages : 649
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This Research Topic is hosted in partnership with the "Grazing in Future Multi-Scapes" international workshop. The workshop will be held online, 30th May - 5th June 2021. Throughout different landscapes of the world, “grazing” herbivores fulfill essential roles in ecology, agriculture, economies and cultures including: families, farms, and communities. Not only do livestock provide food and wealth, they also deliver ecosystem services through the roles they play in environmental composition, structure and dynamics. Grazing, as a descriptive adjective, locates herbivores within a spatial and temporal pastoral context where they naturally graze or are grazed by farmers, ranchers, shepherds etc. In many cases, however, pastoralism with the single objective of maximizing animal production and/or profit has transformed landscapes, diminishing biodiversity, reducing water and air quality, accelerating loss of soil and plant biomass, and displacing indigenous animals and people. These degenerative landscape transformations have jeopardized present and future ecosystem and societal services, breaking the natural integration of land, water, air, health, society and culture. Land-users, policy makers and societies are calling for alternative approaches to pastoral systems; a call for diversified-adaptive and integrative agro-ecological and food-pastoral-systems designs that operate across multiple scales and ‘scapes’ (e.g. thought-, social-, land-, food-, health-, wild-scapes), simultaneously. There needs to be a paradigm shift in pastoral production systems and how grazing herbivores are managed –grazed- within them, derived initially from a change in perception of how they provide wealth. The thoughtscapes will include paradigm shifts where grazers move away from the actual archetype of pastoralism, future landscapes are re-imagined, and regenerative and sustainable management paradigms are put in place to achieve these visions. From this will come a change in collective thinking of how communities and cultures (socialscapes) perceive their relationships with pastoral lands. The landscapes are the biotic and abiotic four-dimensional domains or environments in need of nurture. Landscapes are the tables where humans and herbivores gain their nourishment, i.e. foodscapes. Foodscapes and dietary perceptions, dictate actions and reactions that are changing as developed countries grapple with diseases related to obesity, and people starve in developing countries. Societies are demanding healthscapes and nutraceutical foodscapes, and paradoxically, some are moving away from animal products. While indigenous species of animals, including humans (wildscapes), have been displaced from many of their lands by monotonic pastoralism, multifunctional pastoral systems can be designed in view of dynamic multi-scapes of the future. The purpose of this Research Topic is to influence future mental and practical models of pastoralism in continually evolving multi-scapes. We seek a collection of papers that will cultivate such a shift in thinking towards future models of sustainable multipurpose pastoralism. The contributions will be synthesized to establish how multifunctional pastoral systems can be re-imagined and then designed in view of the integrative dynamics of sustainable future multi-scapes.
Author: United States. Forest Health Protection
Publisher:
ISBN:
Category : Bark beetles
Languages : en
Pages : 60
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 318
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Author: U.s. Forest Service
Publisher: Createspace Independent Pub
ISBN: 9781479314997
Category : Nature
Languages : en
Pages : 24
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The Western Bark Beetle Strategy identifies how the Forest Service is responding to and will respond to the western bark beetle epidemic over the next five years. The extent of the epidemic requires prioritization of treatments, first providing for human safety in areas threatened by standing dead hazard trees, and second, addressing dead and down trees that create hazardous fuels conditions adjacent to high value areas. After the priority of safety, forested areas with severe mortality will be reforested with the appropriate species (Recovery). Forests will also be thinned to reduce the number of trees per acre and create more diverse stand structures to minimize extensive epidemic bark beetle areas (resiliency). This is a modest strategy that reflects current budget realities, but focuses our resources in the most important places that we can make a big difference to the safety of the American public. This strategy covers Fiscal Year (FY) 2011 through 2016. The western United States is experiencing the largest bark beetle outbreak in recorded history. Although western forests have experienced regular infestations throughout their history, the current epidemic is notable for its intensity, extensive geographic range, and simultaneous occurrence in multiple ecosystems. Since 1997, infestations of bark beetle species have escalated resulting in more than 41.7 million acres across all ownerships sustaining some level of conifer tree mortality. The past decade's epidemic is unprecedented in its environmental and social impacts. Various parts of the west experienced bark beetle population peaks at different times over the past 14 years. The Forest Service and the Natural Resources Conservation Service undertook a focused safety and recovery effort that was supported by approximately $138 million in agency and supplemental appropriations. From 2000 through 2009, the intermountain west experienced bark beetle caused mortality over an estimated 21.7 million acres across all ownerships, 17.7 million acres on national forests. The situation is further complicated by the fact that more and more people live and recreate in areas affected by the epidemic. This strategy incorporates our current understanding of available scientific research and presents a science-based path forward. The strategy will be achieved through well-defined goals, objectives, and action items, to address each of the three prongs of the bark beetle problem: human safety, forest recovery, and long-term forest resiliency. A successful approach to mitigating the impact of bark beetle must address actions for all three goals. While safety of human communities and infrastructure protection is paramount, there is also a critical need to restore the function and structure of our forests. Bark beetle is a natural part of our forests and as such will regularly impact our forests and the adjacent communities. Conducting resiliency treatments now and in the future will help minimize the potential for new outbreaks of bark beetles or make future outbreaks less intense. Although there has been much work accomplished to date for bark beetle management, this report focuses on the future. Honing our continuing response will seek to integrate various vegetation management activities across all jurisdictions to address bark beetle concerns in prioritized areas. Now is the time to act. Forest Service resources are in a position in which they can effectively respond and address this issue with increased effort. Public safety and economic impacts and costs will only increase if we delay.
Author: Jacob M. Griffin
Publisher:
ISBN:
Category : Fire
Languages : en
Pages : 12
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The extent and severity of recent native bark beetle (Dendroctonae) outbreaks in western North America have created a pressing need for forest managers to understand potential consequences of post-disturbance management. For example, post-outbreak timber harvest (i.e., salvage harvest) could alter future forest development, productivity and susceptibility to subsequent disturbance. To assess the potential for such consequences, we measured first-year effects of post-outbreak timber harvest on tree regeneration, soil nitrogen (N) availability and fuels by using a paired and replicated before?after-control-impact (BACI) experimental design with eight pairs of 0.25-ha plots in beetle-killed lodgepole pine (Pinus contorta var. latifolia) in Greater Yellowstone (Wyoming, USA). Post-outbreak timber harvest reduced total (live + dead) lodgepole pine basal area by 90%. Total sapling density (advance regeneration) declined by about 50% following harvest, with tall (30?140 cm) saplings declining most, but mean post-harvest sapling density still exceeded 1600 stems ha^?1. Relative species density was unaffected and remained dominated by lodgepole pine. Soil temperature at the litter?soil interface was warmer during summer in harvested stands, and soil View the MathML source concentration increased with harvest relative to untreated plots. Soil View the MathML source concentration and resin bag N accumulation increased through time in all beetle-killed plots and were not affected by harvest. Following harvest, dead woody surface fuels in all size categories doubled, and canopy fuel load and canopy bulk density both were reduced; dead fuel depth, duff depth, and canopy base height did not differ between untreated and harvested plots. Harvest did reduce canopy fuels, but the natural progression of needle shedding after beetle-kill accounted for 25?40% of this total canopy fuel reduction. Salvage harvest seems unlikely to alter post-outbreak successional trajectories in these lodgepole pine forests. However, the altered fuel complex (immediate increase in dead woody surface fuels and expected long-term reduction in large-diameter fuels) in harvested plots could cause subsequent fire behavior and effects to differ between harvested and untreated stands.
Author: Philip Cornwell Johnson
Publisher:
ISBN:
Category : Bark beetles
Languages : en
Pages : 8
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The boles of 71 mature ponderosa pine trees killed by Dendroctonus brevicomis LeConte (Coleoptera: Scolytidae) were analyzed to determine the distribution of the attacks by endemic populations of this bark beetle and those of several phloem -feeding associates. The longitudinal -circumferential distribution of the attacks fitted dia- grammatically into four distinguishable bole infestation patterns. The characteristics of the patterns and similarities with comparable ?attacks of D. brevicomis in northeastern California are discussed.
Author: Heather Kathryn Mehl
Publisher:
ISBN: 9781267400604
Category :
Languages : en
Pages :
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The effects of forest management on pathogen dynamics in Sierra Nevada forests are examined in two distinct systems in this thesis. The first chapter focuses on the causes of forest canopy gaps in Yosemite Valley, where the frequency of disease centers initiated by two native root disease fungi (Heterobasidion irregulare and Armillaria mellea) have increased as an unintended consequence of land management practices implemented decades to over a century ago. Ground surveys were conducted in 1999 and 2011, and photographs from 1972 were used to examine long-term changes in gap causes, frequencies, and sizes. Native root diseases, in conjunction with pine bark beetles, were the most frequent agents of gap initiation. Other gap initiating agents included additional species of bark beetles and heart and butt rotting fungi. Specific mortality agents did not affect the forest in the same way; organisms differed in their influences on gap size, selectivity of tree species removed from the forest, and their response to altered stand conditions. Over the past thirty-nine years, the number and sizes of canopy gaps in the Valley have continually increased, resulting in the loss of roughly one-third of the forest canopy in the west end of Yosemite Valley by 2011, largely as a consequence of the persistence and expansion of root disease-associated gaps over time. This study demonstrates how previous land management (e.g., tree removal, fire suppression) can impact vegetation dynamics over extended time scales, and highlights the importance of considering land-use legacies when interpreting current landscape patterns and processes, and planning future conservation and management objectives. The study presented in the second chapter examines forests dominated by true fir (Abies spp.) infected with dwarf mistletoes (Arceuthobium spp.) throughout the Sierra Nevada. Often, when fir stands are managed for timber, understory trees are left on site following harvest for stand re-stocking. With this type of management, dwarf mistletoe infection on residual firs is a frequent concern. This study examined the effects of dwarf mistletoe infection on developing red (A. magnifica) and white (A. concolor) fir and the efficacy of pre-commercial thinning for reducing losses associated with dwarf mistletoe infection. Radial growth and dwarf mistletoe infection severity were monitored for 20 years, and mortality for 25 years. Fir survival and radial growth decreased with increasing dwarf mistletoe infection severity, and thinning increased survival times and radial growth rates. However, the intensification of dwarf mistletoe on individual trees and spread to previously uninfected trees was greater in thinned than unthinned stands. The results of this study suggest that pre-commercial thinning may help compensate for growth and mortality losses; however, the impact of dwarf mistletoe infection on true firs has been minimal over the course of this study, and so the benefits of thinning may not justify the expense of applying treatments for dwarf mistletoe control in these stands.
Author: Boyd E. Wickman
Publisher:
ISBN:
Category : Bark beetles
Languages : en
Pages : 44
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