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Season Rainfall (season + rainfall)
Selected AbstractsRainfall in arid zones: possible effects of climate change on the population ecology of blue cranesFUNCTIONAL ECOLOGY, Issue 5 2009Res Altwegg Summary 1.,Understanding the demographic mechanisms through which climate affects population dynamics is critical for predicting climate change impacts on biodiversity. In arid habitats, rainfall is the most important forcing climatic factor. Rainfall in arid zones is typically variable and unpredictable, and we therefore hypothesise that its seasonality and variability may be as important for the population ecology of arid zone animals as its total amount. 2.,Here we examine the effect of these aspects of rainfall on reproduction and age specific survival of blue cranes (Anthropoides paradiseus Lichtenstein) in the semi-arid eastern Nama Karoo, South Africa. We then use our results to predict the effect of changes in rainfall at the population level. 3.,Using combined capture-mark-resighting and dead-recovery models, we estimated average survival of cranes to be 0·53 in their first year, 0·73 in their second and third year, and 0·96 for older birds. 4.,We distinguished between three seasons, based on the blue cranes' breeding phenology: early breeding season, late breeding season and nonbreeding season. Cranes survived better with increasing rainfall during the late but not early breeding season. Based on road counts and success of monitored nests, reproduction was positively associated with rainfall during the early but not late breeding season. 5.,A matrix population model predicted that population growth rate would increase with increasing rainfall. A stochastic analysis showed that variation in early breeding season rainfall increased population growth slightly due to the nonlinear relationship between rainfall and reproduction. This effect was opposed by the effect of variation in late breeding season rainfall on survival and overall, variation in rainfall had a negligible effect on population growth. 6.,Our results allow predictions to be made for a range of climate-change scenarios. For example, a shift in seasonality with drier springs but wetter summers would likely decrease reproduction but increase survival, with little overall effect on population growth. [source] Changing Fire Management in the Pastoral Lands of Cape York Peninsula of northeast Australia, 1623 to 1996GEOGRAPHICAL RESEARCH, Issue 1 2000G.M. Crowley Accounts of European explorers between 1623 and 1880 indicate that fires were lit by Aboriginal people on Cape York Peninsula in northeast Australia throughout the dry season (May,October). Diaries kept by three generations of pastoralists in the Musgrave area (1913,1952, 1953,1974 and 1976,1992) show that burning activities were largely confined to a two to six week period between May and early August. The timing of burning depended on the amount and date of cessation of wet season rainfall. More rarely, ,storm-burning', burning under hot conditions within a few days of the first heavy rains of the wet season, was undertaken. Long-term pastoralists felt a responsibility to use fire wisely and had a detailed knowledge of the role of fire in land management. Their decisions to burn were based on the extent of grass curing, and soil and weather conditions, all of which affected the extent of each burn. They used early dry season fires mainly to maintain forage and control cattle movements. Storm-burns were reputed to control woody weeds, but were used infrequently because of difficulty in controlling their spread and uncertainty as to when the next rains would stimulate new grass growth. [source] Implications of future climate and atmospheric CO2 content for regional biogeochemistry, biogeography and ecosystem services across East AfricaGLOBAL CHANGE BIOLOGY, Issue 2 2010RUTH M. DOHERTY Abstract We model future changes in land biogeochemistry and biogeography across East Africa. East Africa is one of few tropical regions where general circulation model (GCM) future climate projections exhibit a robust response of strong future warming and general annual-mean rainfall increases. Eighteen future climate projections from nine GCMs participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment were used as input to the LPJ dynamic global vegetation model (DGVM), which predicted vegetation patterns and carbon storage in agreement with satellite observations and forest inventory data under the present-day climate. All simulations showed future increases in tropical woody vegetation over the region at the expense of grasslands. Regional increases in net primary productivity (NPP) (18,36%) and total carbon storage (3,13%) by 2080,2099 compared with the present-day were common to all simulations. Despite decreases in soil carbon after 2050, seven out of nine simulations continued to show an annual net land carbon sink in the final decades of the 21st century because vegetation biomass continued to increase. The seasonal cycles of rainfall and soil moisture show future increases in wet season rainfall across the GCMs with generally little change in dry season rainfall. Based on the simulated present-day climate and its future trends, the GCMs can be grouped into four broad categories. Overall, our model results suggest that East Africa, a populous and economically poor region, is likely to experience some ecosystem service benefits through increased precipitation, river runoff and fresh water availability. Resulting enhancements in NPP may lead to improved crop yields in some areas. Our results stand in partial contradiction to other studies that suggest possible negative consequences for agriculture, biodiversity and other ecosystem services caused by temperature increases. [source] Increased rainfall variability and reduced rainfall amount decreases soil CO2 flux in a grassland ecosystemGLOBAL CHANGE BIOLOGY, Issue 2 2005Christopher W. Harper Abstract Predicted climate changes in the US Central Plains include altered precipitation regimes with increased occurrence of growing season droughts and higher frequencies of extreme rainfall events. Changes in the amounts and timing of rainfall events will likely affect ecosystem processes, including those that control C cycling and storage. Soil carbon dioxide (CO2) flux is an important component of C cycling in terrestrial ecosystems, and is strongly influenced by climate. While many studies have assessed the influence of soil water content on soil CO2 flux, few have included experimental manipulation of rainfall amounts in intact ecosystems, and we know of no studies that have explicitly addressed the influence of the timing of rainfall events. In order to determine the responses of soil CO2 flux to altered rainfall timing and amounts, we manipulated rainfall inputs to plots of native tallgrass prairie (Konza Prairie, Kansas, USA) over four growing seasons (1998,2001). Specifically, we altered the amounts and/or timing of growing season rainfall in a factorial combination that included two levels of rainfall amount (100% or 70% of naturally occurring rainfall quantity) and two temporal patterns of rain events (ambient timing or a 50% increase in length of dry intervals between events). The size of individual rain events in the altered timing treatment was adjusted so that the quantity of total growing season rainfall in the ambient and altered timing treatments was the same (i.e. fewer, but larger rainfall events characterized the altered timing treatment). Seasonal mean soil CO2 flux decreased by 8% under reduced rainfall amounts, by 13% under altered rainfall timing, and by 20% when both were combined (P<0.01). These changes in soil CO2 flux were consistent with observed changes in plant productivity, which was also reduced by both reduced rainfall quantity and altered rainfall timing. Soil CO2 flux was related to both soil temperature and soil water content in regression analyses; together they explained as much as 64% of the variability in CO2 flux across dates under ambient rainfall timing, but only 38,48% of the variability under altered rainfall timing, suggesting that other factors (e.g. substrate availability, plant or microbial stress) may limit CO2 flux under a climate regime that includes fewer, larger rainfall events. An analysis of the temperature sensitivity of soil CO2 flux indicated that temperature had a reduced effect (lower correlation and lower Q10 values) under the reduced quantity and altered timing treatments. Recognition that changes in the timing of rainfall events may be as, or more, important than changes in rainfall amount in affecting soil CO2 flux and other components of the carbon cycle highlights the complex nature of ecosystem responses to climate change in North American grasslands. [source] Connections of Siberian snow onset dates to the following summer's monsoon conditions over Southeast AsiaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 12 2005Hengchun Ye Abstract This is an exploratory study of possible links between the conditions of early season Eurasian snowfall and the following year's Southeast Asian summer monsoon. Forty years (1950,1995) of historical records are used to examine the statistical connections between early season snow cover onset dates over northern Eurasia and the following year's summer monsoon over Southeast Asia. We found that the time of snow onset is significantly associated with warm season rainfall over Southeast Asia. The most persistent connection is between northeastern Siberian snow onsets and summer monsoon strength over India and northeastern China. This connection seems to be more clearly shown during the mature stage and monsoon withdrawal and is reflected in all three aspects of monsoon characteristics. In other words, the earlier snow cover onset (more snow cover during the early season) over northeastern Siberia, the more precipitation and moisture convergence, the higher prevalence of a southwesterly monsoon wind, and the later monsoon withdrawal over Southeast Asia. The revealed connection is likely through atmospheric circulation associated with early season land surface snow cover processes independent of El Ñino conditions. The authors suggest that more studies are needed to fully understand the circuitous connections between Eurasian snowfall and the Southeastern Asian monsoon. Copyright © 2005 Royal Meteorological Society. [source] Management history and climate as key factors driving natterjack toad population trends in BritainANIMAL CONSERVATION, Issue 5 2010A. L. McGrath Abstract Along with other amphibian populations in Europe and elsewhere, natterjack toad Bufo calamita populations in Britain have declined since at least 1960. Conservation management since the 1970s has aimed to halt the decline and maintain viable populations at key sites throughout the species' recent historical range. Here, we assess population trends from 1985 to 2006 at 20 British B. calamita sites and evaluate the role of active management in maintaining good conservation status. We investigated the effects of 25 climatic, site-characteristic and conservation management variables on population trends using general linear models. In single-variable analyses, rainfall variables showed negative relationships with population trends. Among the site characteristics, being located at the very edge of the species' range (northern Irish Sea coast) and occurrence of common toad (B. bufo) were negatively related to B. calamita population trends. Management history (populations established via translocation as opposed to native populations) had a significant positive effect; as had sites that received greater translocation releases, undergone Species Recovery Programme management, and where common toad was absent. In multiple-variable analyses, the combined effects of management history and average pre-breeding season rainfall accounted for inter-site variation in population trends. The rainfall effects in single- and multiple-variable analyses were strongly influenced by three sites with very high rainfall whilst no clear effect was apparent for the remaining sites. This study highlights the role of climatic factors in population decline, and the importance of conservation management in stabilizing population trends. Climate change over the next 50,100 years is predicted to have limited impacts on most B. calamita populations in Britain, but strongly positive impacts on the most threatened populations located at the very edge of species' range that will benefit from reduced precipitation. A need for active conservation management will remain for the foreseeable future. [source] | ||||||||||