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Low Severity (low + severity)
Selected AbstractsEpidemiology of tomato yellow leaf curl begomovirus in the Fayium area, EgyptEPPO BULLETIN, Issue 2 2000A. E. Aboul-Ata Tomato yellow leaf curl begomovirus (TYLCV) severely invaded tomato plantations in Egypt (Lower and Middle Egypt) in 1989. This study aimed to discover the relationship between TYLCV and other epidemic-associated factors in the Fayium area. The rate of TYLCV infection was inspected visually for three successive years (1994/1996) in the Fayium area. During the same period, whiteflies were collected for virus detection using bait-plant and DNA hybridization techniques. DAS-ELISA was used to detect mixed virus infections in tomato plants. TYLCV infection was prevalent (60,68%) and severe (2.1,3.0) in the Fayium fields. Cucumber mosaic cucumovirus (CMV) was found in some fields (5,28%) with moderate severity (1.0,20). Potato Y potyvirus (PVY) and potato leaf roll polerovirus (PLRV) were found in few fields (5,19% and 5% respectively) at very low severity. There was a negative correlation between TYLCV occurrence and distance from the source of infection, and a positive correlation (98%) between TYLCV intensity and percentage of viruliferous whiteflies in 1994 and 1995. There was no positive correlation between TYLCV and the total population of whiteflies caught during the same period. Five percent of viruliferous whiteflies, as proved by cDNA hybridization, led to 46% TYLCV infection. The same percentage of whiteflies, as shown by bioassay, led to 68% TYLCV infection. Monitoring of viruliferous whiteflies could be used for early prediction of TYLCV infection. [source] Fire, flow and dynamic equilibrium in stream macroinvertebrate communitiesFRESHWATER BIOLOGY, Issue 2 2010ROBERT S. ARKLE Summary 1. The complex effects of disturbances on ecological communities can be further complicated by subsequent perturbations within an ecosystem. We investigated how wildfire interacts with annual variations in peak streamflow to affect the stability of stream macroinvertebrate communities in a central Idaho wilderness, USA. We conducted a 4-year retrospective analysis of unburned (n = 7) and burned (n = 6) catchments, using changes in reflectance values (,NBR) from satellite imagery to quantify the percentage of each catchment's riparian and upland vegetation that burned at high and low severity. 2. For this wildland fire complex, increasing riparian burn severity and extent were associated with greater year-to-year variation, rather than a perennial increase, in sediment loads, organic debris, large woody debris (LWD) and undercut bank structure. Temporal changes in these variables were correlated with yearly peak flow in burned catchments but not in unburned reference catchments, indicating that an interaction between fire and flow can result in decreased habitat stability in burned catchments. 3. Streams in more severely burned catchments exhibited increasingly dynamic macroinvertebrate communities and did not show increased similarity to reference streams over time. Annual variability in macroinvertebrates was attributed, predominantly, to the changing influence of sediment, LWD, riparian cover and organic debris, as quantities of these habitat components fluctuated annually depending on burn severity and annual peak streamflows. 4. These analyses suggest that interactions among fire, flow and stream habitat may increase inter-annual habitat variability and macroinvertebrate community dynamics for a duration approaching the length of the historic fire return interval of the study area. [source] Spatial and temporal variation of fire regimes in a mixed conifer forest landscape, Southern Cascades, California, USAJOURNAL OF BIOGEOGRAPHY, Issue 8 2001R. Matthew Beaty Aim In this study, we evaluated the fire-forest mosaic of a mixed conifer forest landscape by testing the hypothesis that pre-fire suppression fire regime parameters vary with species composition (tree species), and environment (i.e. slope aspect, slope position, elevation). Location Our study was conducted in the 1587 ha Cub Creek Research Natural Area (CCRNA), Lassen National Forest, CA, USA. Methods We quantified the return interval, seasonal occurrence, size, rotation period, and severity of fires using dendroecology. Results Slope aspect, potential soil moisture, forest composition, and fire regime parameters in our study area co-vary. Median composite and point fire return intervals (FRI) were longest on higher, cooler, more mesic, north-facing (NF) slopes covered with white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii),white fir, and red fir (A. magnifica),white fir forests, shortest on the dry, south-facing (SF) slopes covered with ponderosa pine (Pinus ponderosa),white fir forests and intermediate on west-facing slopes dominated by white fir,sugar pine (P. lambertiana),incense cedar (Libocedrus decurrens) forests. The spatial pattern for length of fire rotation (FR) was the same as that for FRI. Fires in CCRNA mixed conifer forests occurred mainly (90%) in the dormant season. Size of burns in CCRNA mixed conifer forests were generally small (mean=106 ha), however, during certain drought years widespread fires burned across fuel breaks and spread throughout the watershed. Fire severity was mainly high on upper slopes, low on lower slopes and moderate and low severity on middle slopes. Patterns of fire severity also varied with slope aspect. Fire frequency decreased dramatically in CCRNA after 1905. Conclusions In CCRNA, fire regime parameters [e.g. FRI, fire extent, FR, fire severity] varied widely with species composition, slope aspect and slope position. There was also temporal variation in fire extent with the most widespread fires occurring during drought years. The important contributions of topography and climate to variation in the fire regime indicates that exogenous factors play a key role in shaping the fire-forest structure mosaic and that the fire-forest structure mosaic is more variable, less predictable and less stable than previously thought. Finally, some characteristics of the fire regime (i.e. fire severity, season of burn) in CCRNA are different than those described for other mixed conifer forests and this suggests that there are geographical differences in mixed conifer fire regimes along the Pacific slope. [source] Hydrothermal processing of rice husks: effects of severity on product distributionJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2008Rodolfo Vegas Abstract BACKGROUND: Treatment in aqueous media (hydrothermal or autohydrolysis reactions) is an environmentally friendly technology for fractionating lignocellulosic materials. Rice husks were subjected to hydrothermal processing under a variety of operational conditions to cause the selective breakdown of xylan chains, in order to assess the effects of reaction severity on the distribution of reaction products. RESULTS: The effects of severity (measured by the severity factor, R0) on the concentrations of the major autohydrolysis products (monosaccharides, xylo- and glucooligosaccharides, xylooligosaccharide substituents, acetic acid, acid-soluble lignin and elemental nitrogen) were assessed. The interrelationship between the severity of treatment and molecular weight distribution was established by high-performance size-exclusion chromatography. Selected samples were subjected to refining treatments as ethyl acetate extraction and ion exchange for refining purposes, and the concentrates were assayed by high-performance anion-exchange chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. CONCLUSIONS The protein equivalent of the products present in liquors accounted for 43 to 51% of the protein present in the raw rice husks. The concentrations of glucose (derived from starchy material) and arabinose (split from the xylan backbone) were fairly constant with severity. Even in treatments at low severity, high molecular weight compounds derived from xylan accounted for a limited part of the stoichiometric amount. Operating under harsh conditions, about 50% of the total xylan-derived compounds corresponded to fractions with a degree of polymerization (DP) < 9. After refining, saccharides accounted for more than 90% of the non-volatile components of the sample. The refined products showed a series of xylose oligomers up to about DP 13, and a series of acetylated xylose oligomers up to about DP 15. Copyright © 2008 Society of Chemical Industry [source] Ecological effects of changes in fire regimes in Pinus ponderosa ecosystems in the Colorado Front RangeJOURNAL OF VEGETATION SCIENCE, Issue 6 2006Rosemary L. Sherriff Abstract Question: What is the relative importance of low- and high-severity fires in shaping forest structure across the range of Pinus ponderosa in northern Colorado? Location: Colorado Front Range, USA. Methods: To assess severities of historic fires, 24 sites were sampled across an elevation range of 1800 to 2800 m for fire scars, tree establishment dates, tree mortality, and changes in tree-ring growth. Results: Below 1950 m, the high number of fire scars, scarcity of large post-fire cohorts, and lack of synchronous tree mortality or growth releases, indicate that historic fires were of low severity. In contrast, above 2200 m, fire severity was greater but frequency of widespread fires was substantially less. At 18 sites above 1950 m, 34 to 80% of the live trees date from establishment associated with the last moderate- to high-severity fire. In these 18 sites, only 2 to 52% of the living trees pre-date these fires suggesting that fire severities prior to any effects of fire suppression were sufficient to kill many trees. Conclusions: These findings for the P. ponderosa zone above ca. 2200 m (i.e. most of the zone) contradict the widespread perception that fire exclusion, at least at the stand scale of tens to hundreds of hectares, has resulted in unnaturally high stand densities or in an atypical abundance of shade-tolerant species. At relatively mesic sites (e.g. higher elevation, north-facing), the historic fire regime consisted of a variable-severity regime, but forest structure was shaped primarily by severe fires rather than by surface fires. [source] Public Opinion of Teen, Classroom, and Formal Court StylesJUVENILE AND FAMILY COURT JOURNAL, Issue 2 2003MARK G. HARMON B.A. ABSTRACT The present research examined the views of a community sample regarding teen court, classroom court, and formal/traditional court. Participants read vignettes of teen offenders who had committed crimes of high or low severity and were given relatively severe or mild sentences through one of the three courts. Results revealed stronger support for teen court than the other courts, a general preference for harsh sentences, and a preference for match between crime and punishment. The results of this study indicate that teen courts are seen as providing an appropriate means to sentence juvenile offenders and are likely to receive public support for their continued operation. [source] Acute occupational pesticide-related illness in the US, 1998,1999: Surveillance findings from the SENSOR-pesticides program,,AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 1 2004Geoffrey M. Calvert MD Abstract Background Concern about the adverse public health and environmental effects of pesticide use is persistent. Recognizing the importance of surveillance for acute occupational pesticide-related illness, we report on surveillance for this condition across multiple states. Methods Survey data collected between 1998 and 1999 were obtained from the seven states that conduct acute occupational pesticide-related illness surveillance as part of the Sentinel Event Notification System for Occupational Risks (SENSOR) program. Data were collected by these state programs in a standardized manner and analyzed. Acute occupational pesticide-related illness incidence rates for those employed in agriculture and those employed in non-agricultural industries were also calculated. Results Between 1998 and 1999, a total of 1,009 individuals with acute occupational pesticide-related illness were identified by states participating in the SENSOR-pesticides program. The mean age was 36 years, and incidence rates peaked among 20,24 year-old workers. The overall incidence rate was 1.17 per 100,000 full time equivalents (FTEs). The incidence rate among those employed in agriculture was higher (18.2/100,000 FTEs) compared to those employed in non-agricultural industries (0.53/100,000 FTEs). Most of the illnesses were of low severity (69.7%). Severity was moderate in 29.6% of the cases, and high in four cases (0.4%). Three fatalities were identified. Insecticides were responsible for 49% of all illnesses. Conclusions Surveillance is an important tool to assess acute pesticide-related illness, and to identify associated risk factors. Our findings suggest that these illnesses continue to be an important occupational health problem, especially in agriculture. As such, greater efforts are needed to prevent acute occupational pesticide-related illness. Am. J. Ind. Med. 45:14,23, 2004. Published 2003 Wiley-Liss, Inc. [source] | ||||||||||