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Long-term Record (long-term + record)
Selected AbstractsHabitat Characteristics of Eurytemora lacustris(Poppe, 1887) (Copepoda, Calanoida): The Role of Lake Depth, Temperature,Oxygen Concentration and Light IntensityINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2005Peter Kasprzak Abstract Field observations, laboratory experiments and a literature survey were conducted to evaluate the habitat characteristics of Eurytemoralacustris (Poppe 1887), a freshwater calanoid copepod species. Combined effects of temperature and oxygen concentration in the deep water of thermally stratifying lakes seem to be the ultimate factors governing the occurrence of the species throughout its home-territory. E. lacustris is largely restricted to relatively deep lakes (>30 m) providing a hypolimnetic refuge characterised by low temperatures (<,10 °C) and oxygenated water during summer. Therefore, although the species is spread over much of Europe it was only found in a small number of lakes. Long-term records in different lakes revealed E. lacustris to be perennial with relatively high biomasses occurring from May to September. During thermal stratification on average 87% of the nauplii and 72% of the copepodite biomass was found in hypolimnetic waters colder than 10 °C. Diurnal vertical migration was observed for the copepodid stages, but the migration amplitude clearly decreased from May to September. The migration amplitude was significantly related to light intensity. According to its special habitat requirements, E. lacustris might be considered a glacial relict sensitive to temperature increase and oxygen depletion. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Climate drivers of red wine quality in four contrasting Australian wine regionsAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2 2008C.J. SOAR Abstract Background and Aims: The understanding of the links between weather and wine quality is fragmented and often qualitative. This study quantified and integrated key weather variables during ripening, and their influence in red wine quality in the Hunter Valley, Margaret River, Coonawarra and Barossa Valley. Methods and Results: Long-term records of published vintage scores were used as an indicator of wine quality. A ,2 analysis was used to compare good (top 25%) versus poor (bottom 25%) vintages in relation to the frequency of defined weather conditions. Using maximum temperature as an example, better quality was associated with temperatures above 34°C throughout most of ripening in the Hunter, below 28°C in early January in the Margaret River, 28,33.9°C towards harvest in Coonawarra, and below 21.9°C in late January and early February and 28,30.9°C towards harvest in the Barossa. Conclusion: Our quantitative assessment allows for the timing and magnitude of weather influences on wine quality on a regional basis. Significance of the Study: The improved specificity of the links between weather and wine quality will help in the development of a risk analysis framework for wine quality across Australia. [source] Climatic influence on the inter-annual variability of late-Holocene minerogenic sediment supply in a boreal forest catchmentEARTH SURFACE PROCESSES AND LANDFORMS, Issue 4 2010Gunilla Petterson Abstract Processes controlling sediment yield vary over a range of timescales, although most process-based observations are extremely short. Lake sediments, however, can be used to extend the observational timescale and are particularly useful when annually laminated (varved) sediment is present. The sediment record at Kassjön (N. Sweden) consists of ,6400 varves, each 0·5,1 mm thick. Image analysis was used to determine grey-scale variation and varve thickness from which annual minerogenic accumulation rate (MinAR) (mg cm,2 year,1) was inferred for the period 4486 BC , AD 1900. MinAR varies on annual to centennial scales and mainly reflects channel bank erosion by the inflow streams. The mineral input reflects the intensity of the spring run-off, which is dependent on the amount of snow accumulated during the winter, and hence MinAR is a long-term record of variability in past winter climate; other factors will be a variable response to catchment uplift, vegetation succession and pedogenesis. A major shift from low to high MinAR occurred ,250 BC, and peaks occurred around AD 250, 600, 1000, 1350 and 1650. Wavelet power spectrum analysis (confirmed by Fourier analyses) indicated significantly different periodicities throughout the period 4000 BC , AD 1700, including 275 years for the period 4000 BC , 2900 BC, 567 years for the period 2901 BC , 1201 BC, and 350 and 725 years for the period 1200 BC , AD 1700. The long-term, centennial scale variability (,350 years) may reflect solar forcing (cf the 385-year peak in tree-ring calibrated 14C activity) but interestingly, there is no obvious link to high frequency forcing, such as the North Atlantic Oscillation. The high resolution component of the record highlights the relevance of varved lake sediment records for understanding erosion dynamics in undisturbed forested catchments and their link to long-term climate dynamics and future climate change. Copyright © 2010 John Wiley & Sons, Ltd. [source] Do phytoplankton communities correctly track trophic changes?FRESHWATER BIOLOGY, Issue 10 2005An assessment using directly measured, palaeolimnological data Summary 1. Measurements of total phosphorus (TP) concentrations since 1975 and a 50-year time series of phytoplankton biovolume and species composition from Lake Mondsee (Austria) were combined with palaeolimnological information on diatom composition and reconstructed TP-levels to describe the response of phytoplankton communities to changing nutrient conditions. 2. Four phases were identified in the long-term record. Phase I was the pre-eutrophication period characterised by TP-levels of about 6 ,g L,1 and diatom dominance. Phase II began in 1966 with an increase in TP concentration followed by the invasion of Planktothrix rubescens in 1968, characterising mesotrophic conditions. Phase III, from 1976 to 1979, had the highest annual mean TP concentrations (up to 36 ,g L,1) and phytoplankton biovolumes (3.57 mm3 L,1), although reductions in external nutrient loading started in 1974. Phases II and III saw an expansion of species characteristic of higher nutrient levels as reflected in the diatom stratigraphy. Oligotrophication (phase IV) began in 1980 when annual average TP concentration, Secchi depth and algal biovolume began to decline, accompanied by increasing concentrations of soluble reactive silica. 3. The period from 1981 to 1986 was characterised by asynchronous trends. Annual mean and maximum total phytoplankton biovolume initially continued to increase after TP concentration began to decline. Reductions in phytoplankton biovolume were delayed by about 5 years. Several phytoplankton species differed in the timing of their responses to changing nutrient conditions. For example, while P. rubescens declined concomitantly with the decline in TP concentration, other species indicative of higher phosphorus concentrations, such as Tabellaria flocculosa var. asterionelloides, tended to increase further. 4. These data therefore do not support the hypotheses that a reduction in TP concentration is accompanied by (i) an immediate decline in total phytoplankton biovolume and (ii) persistence of the species composition characterising the phytoplankton community before nutrient reduction. [source] Satellite rainfall climatology: a reviewINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 9 2001C. Kidd Abstract The monitoring of the world's climate using conventional means is well established, incorporating numerous historical data sets to ensure a long-term record. Parameters such as temperature have been quite accurately recorded over the last 200 years or so, but other parameters such as rainfall are less well recorded. This paper introduces satellite rainfall climatology and why it is important, not only from the longer term study of rainfall, but also for the future monitoring and estimation of rainfall. A summary of the range of satellites and their instruments is reviewed to provide a background to the techniques. These are discussed and their relative merits explored. Finally, examples of the techniques are shown, illustrating the applications to which the satellite-derived data sets may be put. Copyright © 2001 Royal Meteorological Society [source] A long-term record of Quercus decline, logging and fires in a southern Swedish Fagus - Picea forestJOURNAL OF VEGETATION SCIENCE, Issue 6 2002Mats Niklasson Tutin et al. (1964,1976) Abstract. We reconstructed forest development and disturbance events (fire and logging) during the last 1000 yr with tree-ring data, pollen and charcoal analysis from a semi-natural Fagus sylvatica-Picea abies forest (ca. 1 km2) in the hemiboreal zone. According to pollen analysis, Quercus robur together with Pinus sylvestris was abundant in the forest until the turn of the 18th/19th centuries when these species disappeared completely (Quercus) or nearly completely (Pinus) and were replaced by Fagus and Picea. The disappearance of Quercus was corroborated by the remarkable discovery of a single Quercus stump that had been cut in the 18th century and had become overgrown and preserved by a very old Picea. In total 11 fires were dated from 1555 to 1748 from fire scars in several Pinus stumps cut 100 - 200 yr ago. Since the last fire in 1748, no Quercus or Pinus have regenerated in the core of the reserve apart from single pines in neighbouring managed forest (80 yr ago). During the period of documented fires Fagus was protected from fires in a refuge made up of large boulders. Picea colonized the region at the time when the fires ceased 250 yr ago. We hypothesize that most of the fires were probably of human origin because of their patchiness and high frequency compared to the natural background levels of lightning ignitions in the region. On a 300-yr time scale, logging and fire suppression seem to strongly overshadow the effect of climate change on forest composition and dynamics. [source] A long-term record of Nothofagus dominance in the southern Andes, ChileAUSTRAL ECOLOGY, Issue 1 2005William Pollmann Abstract The general model of regeneration dynamics in Nothofagus forests of southern South America could have value in community ecology if predictive relationships between disturbance history, functional traits and site attributes could be identified. Examined here is the proposal that on favourable sites shade-intolerant Nothofagus are likely not to survive in competition with shade-tolerant, broad-leaved evergreen taxa of temperate rain forests, and persistence, thus, is dependent on periodic coarse-scale disturbance. Comparison of stand dynamics of three old-growth Nothofagus forests at different elevations in the southern Andes, Chile where deciduous Nothofagus alpina dominates the upper canopy, and examination of the life history trade-offs of this variation were made. Stem density of all stems ,5.0 cm d.b.h. was 233,303 stems per hectare, and basal area was 123.9,171.0 m2ha,1. Maximum lifespan of N. alpina was found to be greater than ca 640 years, exceeding all previously reported ages for this species in the region. Forests had a stable canopy composition for this long-term, but some appeared to lack effective regeneration of N. alpina in recent years. Regeneration of N. alpina was generally greater in disturbed stands and higher elevation than in undisturbed stands and at lower elevation. Recruitment emerged to be strongly affected by competitive over- and understorey associates. There was a gradient of increasing dependence of N. alpina on disturbance towards the more productive end of the environment gradients, and hence less dependence of N. alpina on disturbance for its regeneration towards higher elevation. The study confirms that changes in forest composition may be explained by processes occurring in accordance with the predictions of the existing model of Nothofagus regeneration dynamics, providing stronger evidence specifically directed at mid-tolerant N. alpina, and by factoring out regeneration dynamics on favourable sites. Thus, for N. alpina, trait differences probably contribute to the competitive advantage over its associates in productive habitats, and may be linked to small-to-intermediate-sized disturbances which inevitably occur as older trees die, enabling N. alpina to persist in forests and therefore maintain species coexistence for the long-term. [source] Rapid morphological change in stream beetle museum specimens correlates with climate changeECOLOGICAL ENTOMOLOGY, Issue 5 2008JENNIFER BABIN-FENSKE Abstract 1.,Climate change has been occurring at unprecedented rates and its impacts on biological populations is beginning to be well documented in the literature. For many species, however, long-term records are not available, and trends have not been documented. 2.,Using museum specimens from southern USA, we show that the stream-dwelling beetle Gyretes sinuatus has shown an 8% increase in body size and change in body shape (fineness ratio) from 1928 to 1988. Any directional morphological change observed over time could be an indicator of a microevolutionary response. 3.,During these 60 years, there have also been changes in temperature, precipitation, and location of collection sites. Unlike the global trend, mean annual temperature in the region has decreased, and furthermore, total annual precipitation has increased. By investigating how these various ecological and geographical variables may affect body size and shape, we can examine which pressures may promote larger and/or thinner beetles. 4.,Results indicate that mean annual temperature was the most predictive variable for the change in size and shape. We suggest there is an adaptive role for temperature on body size and shape of stream dwelling organisms. 5.,We found that museum specimens can be invaluable resources of information when collection date and location information is available. We promote the use of such specimens for future studies of the morphological response to climate change. [source] An analysis of Icelandic climate since the nineteenth centuryINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2004Edward Hanna Abstract New, long monthly series of Icelandic air pressure, temperature, precipitation and sunshine data are presented and analysed to determine possible evidence of recent climatic changes in Iceland. Climatic series are compared with the North Atlantic oscillation (NAO) indices; Icelandic temperature and precipitation are moderately but significantly correlated with the NAO. An updated south,north Iceland temperature index is discussed in relation to 20th century reductions in sea-ice coverage. Net warming over Iceland occurred over all long-term records from the mid19th century to the present, consistent with observed global warming trends, but superimposed on this was a marked cooling between the 1940s and early 1980s; Icelandic warming resumed around 1985. The mid,late 20th century cooling is in agreement with observed cooling in southern Greenland, suggesting that large-scale changes in atmospheric circulation were probably responsible. The 1930s was the warmest decade of the 20th century in Iceland, in contrast to the Northern Hemisphere land average. There was a distinct 20th century dipole in temperatures between Iceland and northwestern Europe, with 1941 serving as an extreme year, i.e. cold Europe and warm Iceland and Greenland. There are also signs of a precipitation increase since the late 19th century, although this is significant for only one out of three stations. Moreover, precipitation rates exhibit a positive correlation with temperature. There were no statistically significant overall long-term changes in pressure or sunshine duration. However, there are statistically significant negative correlations of precipitation with the sunshine data. There is evidence of possible solar forcing of Icelandic temperature and pressure. Results from the analysis aid our understanding of recent and ongoing changes in Icelandic and North Atlantic climate. The results should help us interpret these changes in the context of larger scale atmospheric/subpolar variability and future climate-change predictions. Copyright © 2004 Royal Meteorological Society [source] | |||||||||||||