Effects of high-severity fire drove the population collapse of the subalpine Tasmanian endemic coniferAthrotaxis cupressoides

2014 ◽  
Vol 21 (1) ◽  
pp. 445-458 ◽  
Author(s):  
Andrés Holz ◽  
Sam W. Wood ◽  
Thomas T. Veblen ◽  
David M.J.S. Bowman
Keyword(s):  
Population Collapse ◽  
High Severity ◽  
Tasmanian Endemic

scholarly journals Population collapse and retreat to fire refugia of the Tasmanian endemic conifer Athrotaxis selaginoides following the transition from Aboriginal to European fire management

2020 ◽  
Vol 26 (5) ◽  
pp. 3108-3121 ◽  
Author(s):  
Andrés Holz ◽  
Sam W. Wood ◽  
Carly Ward ◽  
Thomas T. Veblen ◽  
David M. J. S. Bowman
Keyword(s):  
Fire Management ◽  
Population Collapse ◽  
Tasmanian Endemic

Three Dimensional Simulation of High Severity Internally Finned Cracking Coils for Olefins Production

1996 ◽  
Vol 51 (2) ◽  
pp. 245-260 ◽  
Author(s):  
J. J. De Saegher ◽  
T. Detemmerman ◽  
G. F. Froment
Keyword(s):  
Three Dimensional ◽  
High Severity ◽  
Dimensional Simulation

scholarly journals Press-Pulse Odocoileus Virginianus Herbivory in Relict Tsuga Canadensis Stands in the Western Upper Peninsula of Michigan, USA

Forests ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 496
Author(s):  
Grace L. Parikh ◽  
Christopher R. Webster
Keyword(s):  
Odocoileus Virginianus ◽  
Polar Vortex ◽  
Tsuga Canadensis ◽  
Forest Community ◽  
Population Declines ◽  
Upper Peninsula ◽  
Deer Population ◽  
High Severity ◽  
Substantial Decline ◽  
Upper Peninsula Of Michigan

Ungulate herbivory occurring within a forest plant community’s natural range of variation may help maintain species diversity. However, acute or chronically elevated levels of herbivory can produce dramatic changes in forest communities. For example, chronically high levels of herbivory by white-tailed deer (Odocoileus virginianus Zimmerman) in regions of historically low abundance at northern latitudes have dramatically altered forest community composition. In eastern hemlock (Tsuga canadensis L. Carrière) stands where deer aggregate during winter, high deer use has been associated with a shift towards deciduous species (i.e., maples [Acer spp.]) dominating the regeneration layer. Especially harsh winters can lead to deer population declines, which could facilitate regeneration of species that have been suppressed by browsing, such as hemlock. To enhance our understanding of how fluctuations in herbivory influence regeneration dynamics, we surveyed regeneration and deer use in 15 relict hemlock stands in the western Upper Peninsula of Michigan in 2007 and again in 2015. With the exception of small seedlings (0.04–0.24 m height), primarily maples whose abundance increased significantly (p < 0.05), we observed widespread significant declines (p < 0.05) in the abundance of medium (0.25 ≤ 1.4 m height) and large regeneration (>1.4 m tall ≤ 4 cm diameter at breast height) over the study period. Midway through our study period, the region experienced a high severity winter (i.e., “polar vortex”) which resulted in a substantial decline in the white-tailed deer population. Given the dominance of maples and dearth of hemlock in the seedling layer, the decline in the deer population may fail to forestall or possibly hasten the trend towards maple dominance of the regeneration layer as these stands recover from pulses of acute herbivory associated with high-severity winters and the press of chronically high herbivory that precedes them.

scholarly journals Short- and long-term effects of ponderosa pine fuel treatments intersected by the Egley Fire Complex, Oregon, USA

Fire Ecology ◽  
2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Jessie M. Dodge ◽  
Eva K. Strand ◽  
Andrew T. Hudak ◽  
Benjamin C. Bright ◽  
Darcy H. Hammond ◽  
...  
Keyword(s):  
Prescribed Fire ◽  
Vegetation Cover ◽  
Tree Density ◽  
Tree Canopy ◽  
Fuel Treatments ◽  
Dead Tree ◽  
High Severity ◽  
Short And Long Term ◽  
One Year

Abstract Background Fuel treatments are widely used to alter fuels in forested ecosystems to mitigate wildfire behavior and effects. However, few studies have examined long-term ecological effects of interacting fuel treatments (commercial harvests, pre-commercial thinnings, pile and burning, and prescribed fire) and wildfire. Using annually fitted Landsat satellite-derived Normalized Burn Ratio (NBR) curves and paired pre-fire treated and untreated field sites, we tested changes in the differenced NBR (dNBR) and years since treatment as predictors of biophysical attributes one and nine years after the 2007 Egley Fire Complex in Oregon, USA. We also assessed short- and long-term fuel treatment impacts on field-measured attributes one and nine years post fire. Results One-year post-fire burn severity (dNBR) was lower in treated than in untreated sites across the Egley Fire Complex. Annual NBR trends showed that treated sites nearly recovered to pre-fire values four years post fire, while untreated sites had a slower recovery rate. Time since treatment and dNBR significantly predicted tree canopy and understory green vegetation cover in 2008, suggesting that tree canopy and understory vegetation cover increased in areas that were treated recently pre fire. Live tree density was more affected by severity than by pre-fire treatment in either year, as was dead tree density one year post fire. In 2008, neither treatment nor severity affected percent cover of functional groups (shrub, graminoid, forb, invasive, and moss–lichen–fungi); however, by 2016, shrub, graminoid, forb, and invasive cover were higher in high-severity burn sites than in low-severity burn sites. Total fuel loads nine years post fire were higher in untreated, high-severity burn sites than any other sites. Tree canopy cover and density of trees, saplings, and seedlings were lower nine years post fire than one year post fire across treatments and severity, whereas live and dead tree basal area, understory surface cover, and fuel loads increased. Conclusions Pre-fire fuel treatments effectively lowered the occurrence of high-severity wildfire, likely due to successful pre-fire tree and sapling density and surface fuels reduction. This study also quantified the changes in vegetation and fuels from one to nine years post fire. We suggest that low-severity wildfire can meet prescribed fire management objectives of lowering surface fuel accumulations while not increasing overstory tree mortality.

Lecanactis (Roccellaceae) in Tasmania, with the description of a new saxicolous species and a revised key for the genus in Australia

2021 ◽  
Vol 53 (1) ◽  
pp. 95-101
Author(s):  
Gintaras Kantvilas
Keyword(s):  
New Zealand ◽  
New South ◽  
First Record ◽  
New Taxon ◽  
European Species ◽  
Australian Species ◽  
South Wales ◽  
Distribution And Ecology ◽  
Tasmanian Endemic ◽  
First Time

AbstractThe lichen genus Lecanactis Körb. in Tasmania comprises six species: L. abietina (Ach.) Körb., which is widespread and pan-temperate; L. latispora Egea & Torrente and L. neozelandica Egea & Torrente, both shared with New Zealand and with the former recorded here from the Auckland Islands for the first time; L. mollis (Stirt.) Frisch & Ertz, shared with Victoria and New Zealand; L. aff. dilleniana (Ach.) Körb., a European species recorded provisionally for Tasmania on the basis of several sterile collections; L. scopulicola Kantvilas, which is described here as new to science and apparently a Tasmanian endemic. This new taxon occurs in rocky underhangs and is characterized by a thick, leprose thallus containing schizopeltic acid, and 3-septate ascospores, 19–30 × 4.5–6 μm. Short descriptions and a discussion of distribution and ecology are given for all species. A key for all 11 Australian species of the genus is provided, including L. subfarinosa (C. Knight) Hellb. and L. tibelliana Egea & Torrente, which are recorded for Australia for the first time, and L. platygraphoides (Müll.Arg.) Zahlbr., a first record for New South Wales. Lecanactis spermatospora Egea & Torrente and L. sulphurea Egea & Torrente are also included.

scholarly journals Regime shift tipping point in hare population collapse associated with climatic and agricultural change during the very early 20th century

2021 ◽  
Author(s):  
Neil Reid ◽  
Jon E. Brommer ◽  
Nils C. Stenseth ◽  
Ferdia Marnell ◽  
Robbie A. McDonald ◽  
...  
Keyword(s):  
20Th Century ◽  
Regime Shift ◽  
Tipping Point ◽  
Early 20Th Century ◽  
Agricultural Change ◽  
Population Collapse ◽  
Hare Population

scholarly journals Epiphytic macrolichen communities take decades to recover after high‐severity wildfire in chaparral shrublands

2021 ◽  
Author(s):  
Jesse E. D. Miller ◽  
Alexandra M. Weill ◽  
John Villella
Keyword(s):  
High Severity

scholarly journals Population collapse in Congo rainforest from 400 CE urges reassessment of the Bantu Expansion

2021 ◽  
Vol 7 (7) ◽  
pp. eabd8352
Author(s):  
Dirk Seidensticker ◽  
Wannes Hubau ◽  
Dirk Verschuren ◽  
Cesar Fortes-Lima ◽  
Pierre de Maret ◽  
...  
Keyword(s):  
Human Activity ◽  
Climatic Conditions ◽  
Radiocarbon Dates ◽  
Expansion Phase ◽  
Bantu Languages ◽  
Population Collapse ◽  
Early Stages ◽  
Linguistic Evidence ◽  
Spread Model ◽  
Migration Event

The present-day distribution of Bantu languages is commonly thought to reflect the early stages of the Bantu Expansion, the greatest migration event in African prehistory. Using 1149 radiocarbon dates linked to 115 pottery styles recovered from 726 sites throughout the Congo rainforest and adjacent areas, we show that this is not the case. Two periods of more intense human activity, each consisting of an expansion phase with widespread pottery styles and a regionalization phase with many more local pottery styles, are separated by a widespread population collapse between 400 and 600 CE followed by major resettlement centuries later. Coinciding with wetter climatic conditions, the collapse was possibly promoted by a prolonged epidemic. Comparison of our data with genetic and linguistic evidence further supports a spread-over-spread model for the dispersal of Bantu speakers and their languages.

Identifying children at high risk for infection-related decompensation using a predictive emergency department-based electronic assessment tool

Diagnosis ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Robert J. Sepanski ◽  
Arno L. Zaritsky ◽  
Sandip A. Godambe
Keyword(s):  
Emergency Department ◽  
High Risk ◽  
Positive Predictive Value ◽  
Firing Rate ◽  
Predictive Value ◽  
Assessment Tool ◽  
Predictive Tool ◽  
High Severity ◽  
Electronic Assessment ◽  
Ed Visits

AbstractObjectivesElectronic alert systems to identify potential sepsis in children presenting to the emergency department (ED) often either alert too frequently or fail to detect earlier stages of decompensation where timely treatment might prevent serious outcomes.MethodsWe created a predictive tool that continuously monitors our hospital’s electronic health record during ED visits. The tool incorporates new standards for normal/abnormal vital signs based on data from ∼1.2 million children at 169 hospitals. Eighty-two gold standard (GS) sepsis cases arising within 48 h were identified through retrospective chart review of cases sampled from 35,586 ED visits during 2012 and 2014–2015. An additional 1,027 cases with high severity of illness (SOI) based on 3 M’s All Patient Refined – Diagnosis-Related Groups (APR-DRG) were identified from these and 26,026 additional visits during 2017. An iterative process assigned weights to main factors and interactions significantly associated with GS cases, creating an overall “score” that maximized the sensitivity for GS cases and positive predictive value for high SOI outcomes.ResultsTool implementation began August 2017; subsequent improvements resulted in 77% sensitivity for identifying GS sepsis within 48 h, 22.5% positive predictive value for major/extreme SOI outcomes, and 2% overall firing rate of ED patients. The incidence of high-severity outcomes increased rapidly with tool score. Admitted alert positive patients were hospitalized nearly twice as long as alert negative patients.ConclusionsOur ED-based electronic tool combines high sensitivity in predicting GS sepsis, high predictive value for physiologic decompensation, and a low firing rate. The tool can help optimize critical treatments for these high-risk children.

Sign in / Sign up

Export Citation Format

Share Document