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Climate Zones (climate + zone)
Selected AbstractsInfluences of the vegetation mosaic on riparian and stream environments in a mixed forest-grassland landscape in "Mediterranean" northwestern CaliforniaECOGRAPHY, Issue 4 2005Hartwell H. Welsh We examined differences in riparian and aquatic environments within the three dominant vegetation patch types of the Mattole River watershed, a 789-km2 mixed conifer-deciduous (hardwood) forest and grassland-dominated landscape in northwestern California, USA. Riparian and aquatic environments, and particularly microclimates therein, influence the distributions of many vertebrate species, particularly the physiologically-restricted ectotherms , reptiles and amphibians (herpetofauna), and fishes. In addition to being a significant portion of the native biodiversity of a landscape, the presence and relative numbers of these more tractable small vertebrates can serve as useful metrics of its "ecological health." Our primary objective was to determine the range of available riparian and aquatic microclimatic regimes, and discern how these regimes relate to the dominant vegetations that comprise the landscape mosaic. A second objective, reported in a companion paper, was to examine relationships between available microclimatic regimes and herpetofaunal distributions. Here we examined differences in the composition, structure, and related environmental attributes of the three dominant vegetation types, both adjacent to and within the riparian corridors along 49 tributaries. Using automated dataloggers, we recorded hourly water and air temperatures and relative humidity throughout the summer at a representative subset of streams; providing us with daily means and amplitudes for these variables within riparian environments during the hottest period. Although the three vegetation types that dominate this landscape each had unique structural attributes, the overlap in plant species composition indicates that they represent a seral continuum. None-the-less, we found distinct microclimates in each type. Only riparian within late-seral forests contained summer water temperatures that could support cold-water-adapted species. We evaluated landscape-level variables to determine the best predictors of water temperature as represented by the maximum weekly maximum temperature (MWMT). The best model for predicting MWMT (adj. R2=0.69) consisted of catchment area, aspect, and the proportion of non-forested (grassland) patches. Our model provides a useful tool for management of cold-water fauna (e.g. salmonids, stream amphibians) throughout California's "Mediterranean" climate zone. [source] Europe's 2003 heat wave: a satellite view of impacts and land,atmosphere feedbacksINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 6 2006Benjamin F. Zaitchik Abstract A combination of satellite imagery, meteorological station data, and the NCEP/NCAR reanalysis has been used to explore the spatial and temporal evolution of the 2003 heat wave in France, with focus on understanding the impacts and feedbacks at the land surface. Vegetation was severely affected across the study area, especially in a swath across central France that corresponds to the Western European Broadleaf (WEB) Forests ecological zone. The remotely sensed surface temperature anomaly was also greatest in this zone, peaking at +15.4 °C in August. On a finer spatial scale, both the vegetation and surface temperature anomalies were greater for crops and pastures than for forested lands. The heat wave was also associated with an anomalous surface forcing of air temperature. Relative to other years in record, satellite-derived estimates of surface-sensible heat flux indicate an enhancement of 48,61% (24.0,30.5 W m,2) in WEB during the August heat wave maximum. Longwave radiative heating of the planetary boundary layer (PBL) was enhanced by 10.5 W m,2 in WEB for the same period. The magnitude and spatial structure of this local heating is consistent with models of the late twenty-first century climate in France, which predict a transitional climate zone that will become increasingly affected by summertime drought. Models of future climate also suggest that a soil-moisture feedback on the surface energy balance might exacerbate summertime drought, and these proposed feedback mechanisms were tested using satellite-derived heat budgets. Copyright © 2006 Royal Meteorological Society. [source] Cutaneous melanoma in a desert climate zone: a retrospective study of 125 casesINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 4 2010Zahra Rahnama MD Background, With increasing incidence over the last few decades, cutaneous malignant melanoma (CM) represents 3% of all skin tumors, and accounts for 75% of all deaths because of cutaneous malignancies. Little is known about the nature and epidemiology of CM in individuals with pigmented skin. Method, Data were collected from the records of four public and private histopathology laboratories of Kerman city from March 20, 1994 to March 20, 2004. Skin biopsies with a diagnosis of CM were reevaluated to confirm the diagnosis of CM. The medical records of the patients were also taken into consideration. Results, A total of 125 CMs were found. The male-to-female ratio was 1.08 : 1. The mean age at the time of diagnosis was 58.9 years; with a peak in the seventh decade of life. Acral-lentiginous melanoma (ALM) represented 28.8% and; nodular melanoma occurred in 20% of cases. Limbs were the site of occurrence in 44% of tumors; whereas 36% of tumors occurred in head and neck region. There was a significant correlation between age and ALM (P = 0.007) and also between gender and melanoma types (P = 0.024). Conclusions, This study indicates that some demographic and histopathologic features of CM in this population differ from those in the literature. More studies including cohort studies are needed to fully describe the nature and survival rate of CM in this area. [source] Variation in the impact of exotic grasses on native plant composition in relation to fire across an elevation gradient in HawaiiAUSTRAL ECOLOGY, Issue 5 2000Carla M. D'Antonio Abstract The impact that an exotic species can have on the composition of the community it enters is a function of its abundance, its particular species traits and characteristics of the recipient community. In this study we examined species composition in 14 sites burned in fires fuelled by non-indigenous C4 grasses in Hawaii Volcanoes National Park, Hawaii. We considered fire intensity, time since fire, climatic zone of site, unburned grass cover, unburned native cover and identity of the most abundant exotic grass in the adjacent unburned site as potential predictor variables of the impact of fire upon native species. We found that climatic zone was the single best variable for explaining variation in native cover among burned sites and between burned and unburned pairs. Fire in the eastern coastal lowlands had a very small effect on native plant cover and often stimulated native species regeneration, whereas fire in the seasonal submontane zone consistently caused a decline in native species cover and almost no species were fire tolerant. The dominant shrub, Styphelia tameiameia, in particular was fire intolerant. The number of years since fire, fire intensity and native cover in reference sites were not significantly correlated with native species cover in burned sites. The particular species of grass that carried the fire did however, have a significant effect on native species recovery. Where the African grass Melinis minutiflora was a dominant or codominant species, fire impacts were more severe than where it was absent regardless of climate zone. Overall, the impacts of exotic grass-fuelled fires on native species composition and cover in seasonally dry Hawaiian ecosystems was context specific. This specificity is best explained by differences between the climatic zones in which fire occurred. Elevation was the main physical variable that differed among the climatic zones and it alone could explain a large percentage of the variation in native cover among sites. Rainfall, by contrast, did not vary systematically with elevation. Elevation is associated with differences in composition of the native species assemblages. In the coastal lowlands, the native grass Heteropogon contortus, was largely responsible for positive changes in native cover after fire although other native species also increased. Like the exotic grasses, this species is a perennial C4 grass. It is lacking in the submontane zone and there are no comparable native species there and almost all native species in the submontane zone were reduced by fire. The lack of fire tolerant species in the submontane zone thus clearly contributes to the devastating impact of fire upon native cover there. [source] Modeled interactive effects of precipitation, temperature, and [CO2] on ecosystem carbon and water dynamics in different climatic zonesGLOBAL CHANGE BIOLOGY, Issue 9 2008YIQI LUO Abstract Interactive effects of multiple global change factors on ecosystem processes are complex. It is relatively expensive to explore those interactions in manipulative experiments. We conducted a modeling analysis to identify potentially important interactions and to stimulate hypothesis formulation for experimental research. Four models were used to quantify interactive effects of climate warming (T), altered precipitation amounts [doubled (DP) and halved (HP)] and seasonality (SP, moving precipitation in July and August to January and February to create summer drought), and elevated [CO2] (C) on net primary production (NPP), heterotrophic respiration (Rh), net ecosystem production (NEP), transpiration, and runoff. We examined those responses in seven ecosystems, including forests, grasslands, and heathlands in different climate zones. The modeling analysis showed that none of the three-way interactions among T, C, and altered precipitation was substantial for either carbon or water processes, nor consistent among the seven ecosystems. However, two-way interactive effects on NPP, Rh, and NEP were generally positive (i.e. amplification of one factor's effect by the other factor) between T and C or between T and DP. A negative interaction (i.e. depression of one factor's effect by the other factor) occurred for simulated NPP between T and HP. The interactive effects on runoff were positive between T and HP. Four pairs of two-way interactive effects on plant transpiration were positive and two pairs negative. In addition, wet sites generally had smaller relative changes in NPP, Rh, runoff, and transpiration but larger absolute changes in NEP than dry sites in response to the treatments. The modeling results suggest new hypotheses to be tested in multifactor global change experiments. Likewise, more experimental evidence is needed for the further improvement of ecosystem models in order to adequately simulate complex interactive processes. [source] Linking flux network measurements to continental scale simulations: ecosystem carbon dioxide exchange capacity under non-water-stressed conditionsGLOBAL CHANGE BIOLOGY, Issue 4 2007KATHERINE E. OWEN Abstract This paper examines long-term eddy covariance data from 18 European and 17 North American and Asian forest, wetland, tundra, grassland, and cropland sites under non-water-stressed conditions with an empirical rectangular hyperbolic light response model and a single layer two light-class carboxylase-based model. Relationships according to ecosystem functional type are demonstrated between empirical and physiological parameters, suggesting linkages between easily estimated parameters and those with greater potential for process interpretation. Relatively sparse documentation of leaf area index dynamics at flux tower sites is found to be a major difficulty in model inversion and flux interpretation. Therefore, a simplification of the physiological model is carried out for a subset of European network sites with extensive ancillary data. The results from these selected sites are used to derive a new parameter and means for comparing empirical and physiologically based methods across all sites, regardless of ancillary data. The results from the European analysis are then compared with results from the other Northern Hemisphere sites and similar relationships for the simplified process-based parameter were found to hold for European, North American, and Asian temperate and boreal climate zones. This parameter is useful for bridging between flux network observations and continental scale spatial simulations of vegetation/atmosphere carbon dioxide exchange. [source] Unequivocal morphological diagnosis of fungi in morphologically abnormal nailsHISTOPATHOLOGY, Issue 7 2006A Cabral Aims :,To analyse the prevalence of fungi in abnormal nails by morphological diagnosis. Prevalence studies of onychomycoses in temperate climate zones have yielded widely varying rates, possibly reflecting the confounding effects of referral bias, sampling specificity and intrinsic sensitivity of the diagnostic techniques employed. Methods and results :,The method employed to identify fungi in nails entailed primary fixation using a non-formaldehyde-based coagulative fixative (BoonFix®; Finetec, Japan) and microwave-enhanced processing to histology, followed by staining the paraffin sections with periodic acid,Schiff, using haematoxylin as a routine counterstain. The results of 990 nail samples were tabled for statistical analysis related to gender, patient age and diabetes mellitus status. In four of the 990 (< 1%) analysed cases the diagnosis was found to be equivocal using the method employed. These cases were jointly reviewed for definitive diagnosis. The overall prevalence of invasive hyphal structures was found to be 606/990 (, 61%). The relative risk for fungal infection in morphologically abnormal nails was found to be higher for persons <,20 years old or diabetic patients aged ,,71 years. Conclusions :,The 61% positivity rate for fungi found justifies systematic direct submission of samples from abnormal nails for histological confirmation in order to avoid unwarranted treatment. [source] Global analysis of runs of annual precipitation and runoff equal to or below the median: run lengthINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 7 2004Murray C. Peel Abstract The investigation of fluctuations of wet and dry years has a long history in the climatology and hydrology literature. In this, the first of two papers investigating runs of consecutive dry years, the lengths (persistence) of dry runs are investigated. In the second paper the magnitude/intensity and severity (length × magnitude) of dry runs will be investigated. Consecutive dry years are associated with drought, which is a significant physical and economic phenomenon that imposes great stress on ecosystems and societies. Run lengths of consecutive years equal to or below the median were analysed for 3863 precipitation and 1236 runoff stations from around the world. Run lengths were found to be similar across all continents and Köppen climate zones, expect for tropical and arid North Africa (Sahel), which showed a distinct bias toward longer run lengths than any other region of the world. Generally, the run length observed in annual runoff was found to be similar to that observed in annual precipitation for the same location. Both annual precipitation and runoff data were found to be well described by the lag-one autoregressive (AR(1)) model or by white noise. The influence of the El Niño,southern oscillation on run lengths was not observed to be significant. The presence of decadal and multi-decadal oscillations was weakly observed in the results of the precipitation runs analysis. The faintness of the decadal and multi-decadal oscillation signal may be due to the sample sizes not being long enough and/or the runs analysis not being sensitive enough to detect their presence. Copyright © 2004 Royal Meteorological Society [source] A review on energy, economical, and environmental benefits of the use of CHP systems for small commercial buildings for the North American climateINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 14 2009P. J. Mago Abstract The use of combined heating and power (CHP) systems to produce both electricity and heat is increasing rapidly due to their high potential of reducing primary energy consumption (PEC), cost, and emissions in domestic, commercial, and industrial applications. In addition to producing both electricity and heat, CHP systems can be coupled with vapor compression systems to provide cooling. This paper analyzes a natural gas engine CHP system together with a vapor compression system for different American climate zones. Performance is measured in terms of operational costs, PEC, and carbon dioxide emissions as a percent of a reference building. The objective of this paper is to compare the performance of a CHP system operating 24,h a day with a system that only operates during typical office hours. Furthermore, the system is optimized based on reducing PEC, minimizing costs, and reducing emissions. In addition, the benefits of CHP systems based on the Energy Star program and the Leadership in Energy and Environmental Design (LEED) program are presented. Results show that, in general, it is more beneficial to operate the CHP system during typical office hours than to operate the system 24,h a day. Also, the CHP system performance strongly depends on the location where it is installed. In addition to reductions in cost, primary energy, and emissions, CHP systems can help achieve the Energy Star label for commercial office buildings and help obtain LEED points that go toward achieving LEED certification status. Copyright © 2009 John Wiley & Sons, Ltd. [source] Gene movement and genetic association with regional climate gradients in California valley oak (Quercus lobata Née) in the face of climate changeMOLECULAR ECOLOGY, Issue 17 2010VICTORIA L. SORK Abstract Rapid climate change jeopardizes tree populations by shifting current climate zones. To avoid extinction, tree populations must tolerate, adapt, or migrate. Here we investigate geographic patterns of genetic variation in valley oak, Quercus lobata Née, to assess how underlying genetic structure of populations might influence this species' ability to survive climate change. First, to understand how genetic lineages shape spatial genetic patterns, we examine historical patterns of colonization. Second, we examine the correlation between multivariate nuclear genetic variation and climatic variation. Third, to illustrate how geographic genetic variation could interact with regional patterns of 21st Century climate change, we produce region-specific bioclimatic distributions of valley oak using Maximum Entropy (MAXENT) models based on downscaled historical (1971,2000) and future (2070,2100) climate grids. Future climatologies are based on a moderate-high (A2) carbon emission scenario and two different global climate models. Chloroplast markers indicate historical range-wide connectivity via colonization, especially in the north. Multivariate nuclear genotypes show a strong association with climate variation that provides opportunity for local adaptation to the conditions within their climatic envelope. Comparison of regional current and projected patterns of climate suitability indicates that valley oaks grow in distinctly different climate conditions in different parts of their range. Our models predict widely different regional outcomes from local displacement of a few kilometres to hundreds of kilometres. We conclude that the relative importance of migration, adaptation, and tolerance are likely to vary widely for populations among regions, and that late 21st Century conditions could lead to regional extinctions. [source] A long-term study of non-native-heartworm transmission among coyotes in a Mediterranean ecosystemOIKOS, Issue 3 2003Benjamin N. Sacks In Mediterranean ecosystems, abiotic factors are known to affect vertebrate population dynamics, but little is known about how these factors affect population dynamics of parasites. We conducted a 9-year investigation of the roles of temperature, precipitation, and vector abundance as determinants of transmission of the non-native canine heartworm (Dirofilaria immitis), a dangerous parasite of pets, among coyotes (Canis latrans), an important reservoir, in north-coastal California. Dates of heartworm transmission and total annual transmission were determined, respectively, from lengths and numbers of heartworms found in known-age coyotes. Vector host-seeking activity was assessed through weekly mosquito trapping. Within years, heartworm transmission occurred only when cumulative temperatures were sufficient to allow larval heartworms to develop to the infective stage (as predicted by an existing degree-day model), and when suitable vectors were available. Most (95%) heartworms infected their hosts between 1 July and 14 September. The onset of transmission periods always occurred after the peak in vector host-seeking activity and varied annually. Transmission periods ended before temperatures became limiting due to absence of vectors. The timing of host-seeking activity of the primary vector species, Ochlerotatus sierrensis, also was correlated with the onset of warming temperatures such that parasite and vector phenology were synchronized. For this reason (partly), the variation in timing of seasonal warming had no detectable effect on total annual transmission. Abundance of host-seeking Oc. sierrensis was positively correlated with annual precipitation, and annual heartworm transmission was positively correlated with abundance of host-seeking Oc. sierrensis. Annual transmission also was positively correlated with abundance of a less numerous vector species, Anopheles punctipennis, and was directly correlated with precipitation. This study demonstrates that multiannual variability in temperature, which affects seasonality of transmission, has little effect on annual transmission, but that precipitation is a driving force determining annual transmission. These findings imply that in California, and possibly other Mediterranean climate zones, it is especially important to preventively treat pets in summers following high-rainfall winters. [source] | |||||||||||||