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Warmer Months (warmer + month)
Selected AbstractsSeasonal and management influences on bacterial community structure in an upland grassland soilFEMS MICROBIOLOGY ECOLOGY, Issue 3 2005Nabla M. Kennedy Abstract Floristically diverse Nardo,Galion upland grasslands are common in Ireland and the UK and are valuable in agricultural, environmental and ecological terms. Under improvement (inputs of lime, fertiliser and re-seeding), they convert to mesotrophic grassland containing very few plant species. The effects of upland grassland improvement and seasonality on soil microbial communities were investigated at an upland site. Samples were taken at five times in one year in order to observe seasonal trends, and bacterial community structure was monitored using automated ribosomal intergenic spacer analysis (ARISA), a DNA-fingerprinting approach. Differences in soil chemistry and bacterial community structure between unimproved and improved grassland soils were noted. Season was also found to cause mild fluctuations in bacterial community structure, with soil samples from colder months (October and December) more correlated with change in ribotype profiles than samples from warmer months. However, for the majority of seasons clear differences in bacterial community structures from unimproved and improved soils could be seen, indicating seasonal influences did not obscure effects associated with improvement. [source] Spatial and temporal patterns of microcrustacean assemblage structure and secondary production in a wetland ecosystemFRESHWATER BIOLOGY, Issue 7 2009A. MARIA LEMKE Summary 1. In contrast to extensive studies of zooplankton in lakes, the role of microcrustaceans in wetlands is not well studied. In this study, spatial and temporal patterns of microcrustacean assemblage structure and secondary production were quantified over a 2-year period in a southeastern U.S.A. wetland. 2. Thirty-two species, including 19 cladocerans, 10 copepods and three ostracods, generated different temporal patterns of density and production between vegetated (Nymphaea) and non-vegetated (open-water) zones reflecting species-specific differences in life histories. 3. Summer assemblages were dominated by small, planktonic filter-feeders, typified by high annual production/biomass (P/B) and daily production. In contrast, winter assemblages were dominated by larger, epibenthic detritivores with low P/B and high biomass. Seasonal shifts in the relative importance of planktonic species in the warmer months to benthic and epiphytic species in the cooler months suggest that energy flow pathways through microcrustaceans may vary seasonally. 4. Total annual production was higher during both years in the Nymphaea zone (13.0 g and 13.6 g DM m,2 year,1) than the open-water (8.2 and 6.3 g DM m,2 year,1), and was similar between years for the entire wetland pond (12.3 and 12.2 g DM m,2 year,1). 5. Although wetland ecosystems have been the subject of considerable ecological research in the past 20 years, our study is one of the few to demonstrate a highly diverse and relatively productive microcrustacean assemblage. Such comprehensive production studies can be used to quantify the ecological importance of microcrustaceans in freshwater wetland ecosystems. [source] Environmental control of fine root dynamics in a northern hardwood forestGLOBAL CHANGE BIOLOGY, Issue 5 2003GERALDINE L. TIERNEY Abstract Understanding how exogenous and endogenous factors control the distribution, production and mortality of fine roots is fundamental to assessing the implications of global change, yet our knowledge of control over fine root dynamics remains rudimentary. To improve understanding of these processes, the present study developed regression relationships between environmental variables and fine root dynamics within a northern hardwood forest in New Hampshire, USA, which was experimentally manipulated with a snow removal treatment. Fine roots (< 1 mm diameter) were observed using minirhizotrons for 2 years in sugar maple and yellow birch stands and analyzed in relation to temperature, water and nutrient availability. Fine root dynamics at this site fluctuated seasonally, with growth and mortality peaking during warmer months. Monthly fine root production was strongly associated with mean monthly air temperature and neither soil moisture nor nutrient availability added additional predictive power to this relationship. This relationship exhibited a seasonal temperature hysteresis, which was altered by snow removal treatment. These results suggest that both exogenous and endogenous cues may be important in controlling fine root growth in this system. Proportional fine root mortality was directly associated with mean monthly soil temperature, and proportional fine root mortality during the over-winter interval was strongly related to whether the soil froze. The strong relationship between fine root production and air temperature reported herein contrasts with findings from some hardwood forest sites and indicates that controls on fine root dynamics vary geographically. Future research must more clearly distinguish between endogenous and exogenous control over fine root dynamics in various ecosystems. [source] Seasonality trends of Pediculosis capitis and Phthirus pubis in a young adult population: follow-up of 20 yearsJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 3 2002D Mimouni Abstract Background It is not mandatory to report Pediculosis capitis and Phthirus pubis in most countries; therefore, little is known about the seasonality of these infestations. Methods We analysed the data based on routine and mandatory reporting of every case of Pediculosis capitis and Phthirus pubis to the Army Health Branch Epidemiology Department, Israel, over the last two decades. Results The average 20-year incidence of Pediculosis capitis shows a significant rise during the warmer months (R2 = 0.692, P < 0.05) with a parallel significant decrease in the cooler months (R2 = 0.893, P < 0.05). The results for Phthirus pubis show a significantly higher person-time incidence in the winter (P < 0.001). Sensitivity analysis to investigate possible sources of heterogeneity during this time indicated that no single year was an important source of heterogeneity. ConclusionsPediculosis capitis is more frequent in the warmer months, whereas Phthirus pubis is more dominant in the cooler months. [source] Population Ecology of the Riparian Frog Eleutherodactylus cuneatus in CubaBIOTROPICA, Issue 3 2010Ansel Fong G. ABSTRACT A population of the poorly known riparian frog Eleutherodactylus cuneatus was studied for 1 yr along a mountain stream in eastern Cuba. We examined population structure, seasonal and daily activity, growth, and habitat use using mark-recapture and call-point counts. Juveniles were observed during all survey periods with a spike in March. Higher numbers of adults were present in May,July, associated with longer day length, warmer temperatures, and the onset of the rainy season. This was coincident with higher calling activity away from the stream, suggesting an increase in both reproductive and nonreproductive activity in the warmer months between May and September. The number of individuals peaked at 2000,2200 h, but high numbers of individuals were visible throughout the night. Lower activity levels were observed throughout the day. Population size estimates were 84,131 adults and 124,304 juveniles, with averages of 110 and 236 individuals, survival rates were high but capture probabilities were low for a 5-d period in March 2004. Growth rate was negatively related to the size of recaptured individuals, although decreases in growth rate were slight. Frogs were found either in the water (49.7%), or in the banks and on the ground adjacent to the stream where most individuals were found on the ground under the cover of rocks, leaf litter, or large palm fronds. These results provide baseline knowledge of E. cuneatus population dynamics and ecology needed for a rapid detection of any decline this population may undergo in the future. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp [source] A stable isotope record from freshwater lake shells of the eastern Tibetan Plateau, China, during the past two centuriesBOREAS, Issue 1 2007JINGLU WU Wu, J. L., Schleser, G. H., Lücke, A. & Li, S. 2007 (January): A stable isotope record from freshwater lake shells of the eastern Tibetan Plateau, China, during the past two centuries. Boreas, Vol. 36, pp. 38,46. Oslo. ISSN 0300,9483. Lake Xingcuo is a small, closed, hardwater lake situated in the eastern Tibetan Plateau. Stable isotope data (,18O and ,13C) from the freshwater snail Gyraulus sibirica (Dunker) in a 34-cm-long, radioactive isotope-dated sediment core represent the past 200 years of Lake Xingcuo environmental history. Carbon and oxygen isotope ratios in the shells of the snail yield information on the isotopic composition of the water in which the shell was formed, which in turn relates to climatic conditions prevailing during the snail's life-span. Living and fossil shells from Lake Xingcuo were collected. ,18O values in the living shells from Lake Xingcuo are in equilibrium with ambient waters, while ,13C values may trace snail dietary carbon. On comparing ,18O and ,13C in the shell of Gyraulus sibirica with monitored data for the period 1954,1995, we found that the ,18O composition in the shell is an efficient proxy revealing air temperature during the warmer months from April to September. There is a positive correlation between the ,18O in the shells of Gyraulus sibirica and the running average temperature of the warmer months. Climatic variability in the eastern Tibetan Plateau for the past two centuries has been inferred from the ,18O record from the freshwater snails in the sediments of Lake Xingcuo. As such, the last 200 years' palaeoclimatic record for this region can be separated into three periods representing oscillations between warm and cool conditions consistent with the Guliya ice record in the Tibetan Plateau. [source] | ||||||||||