Rainfall In May Research Articles

Calendar and degree-day requirements for emergence of adult wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae) in Saskatchewan, Canada

Insect/host plant phenologies are particularly important in the management of wheat midge in western Canada. Emergence of adult wheat midge, Sitodiplosis mosellana (Géhin), was evaluated at 19 sites in Saskatchewan in 1991–2000. Emergence was assessed in relation to calendar days and accumulated degree-days above five base air temperatures. Three sites that received less than 20 mm rainfall in May were deleted from the analysis because emergence was erratic and delayed. Males emerged 2–3 days before females. Calendar dates for 10%, 50% and 90% emergence of both sexes were July 11 ± 5.9 days, July 18 ± 5.4 days and July 25 ± 5.9 days, respectively. Deviations between observed and expected emergence dates at most sites related to degree-day accumulations between March 1 and July 31. Emergence was 2–8 days earlier than expected at sites with the highest degree-day accumulation and 4–10 days later than expected at sites with the lowest accumulation. Degree-day requirements for emergence declined as the base air temperature increased. In most instances, accumulated degree-days above 5 °C provided the most accurate estimates of emergence. With a 5 °C base temperature, accumulated degree-days (DD) for 10%, 50% and 90% emergence of both sexes averaged 693 DD ± 2.8 days, 784 DD ± 2.5 days and 874 DD ± 3.2 days, respectively. Deviations between observed and expected emergence dates at most sites related to precipitation in May and June. Emergence was 1–7 days earlier than expected at sites receiving 20–30 mm rain in May. Conversely, emergence was 2–8 days later than expected at sites receiving more than 145 mm rain in May and June. Adult emergence was re-assessed in 2008. Dates for 10%, 50% and 90% emergence of both sexes differed from expected values by one day or less. Accumulated degree-days above 5 °C for 10%, 50% and 90% emergence differed from expected values by 8–35 DD. The merits of using calendar dates and degree-days to predict emergence of adult wheat midge are discussed.

Available water and wheat grain yield relations in a Mediterranean climate

Wheat ( Triticum aestivum L.) is the principle crop grown in many Mediterranean climate zones around the world, including the 3.35 million hectare dryland cropping region of the Inland Pacific Northwest (PNW) of the United States. Farmers in the low- and intermediate-precipitation areas of the region are often reluctant to plant spring wheat (SW) because grain yields are highly variable compared to winter wheat (WW) after summer fallow (SF). Our objectives were to: (i) assess available water and wheat grain yield relations from well-fertilized dryland field experiments conducted from 1953 to 1957 versus related studies from 1993 to 2005, (ii) compare and compartmentalize available water-use efficiency of WW compared to SW during the 1993–2005 period, and (iii) provide a tool to allow farmers to predict SW grain yield based on stored soil water at time of planting plus expected spring (April, May, June) rainfall. Simple linear regression showed that 10.1 cm of available water was required just for vegetative growth (before wheat reproductive development begins) in the 1953–1957 study ( n = 90 replicated treatments), whereas only 5.9 cm of available water was needed in the 1993–2005 experiment ( n = 175 replicated treatments). In addition to water required for vegetative growth, multiple regression analysis showed that from 1953 to 1957 each centimeter of available stored soil water and spring rainfall (SR) produced 140 and 183 kg grain ha −1, respectively, compared to 150 and 174 kg grain ha −1, respectively, for the 1993–2005 study. Multiple regression further demonstrated in the 1993–2005 studies that April rainfall contributed much less to grain yield than rainfall in May and June for both SW and WW. Winter wheat always produced more grain per unit of available water compared to SW. Data reveal that modern semi-dwarf wheat cultivars begin grain production with 4.2 cm less available water than standard-height cultivars of the 1950s. This, along with improved agronomic management, is a major contributor to ever increasing wheat grain yields during the past 50 years.

Effect of seasonal rainfall, N fertilizer and tillage on N utilization by dryland wheat in a semi-arid environment

Crop yield and N uptake in semi-arid environments are typically limited by available water and/or N. Since remobilization of shoot N is a major source of grain N, an understanding of how it is influenced by soil N and water supply, and tillage, is required. In 2003, 2005 and 2006, we determined the influence of N supply (0 or 60 kg fertilizer N ha−1) and tillage [no tillage (NT) or conventional tillage (CT)] on N translocation and N use efficiency of wheat (Triticum aestivum L.) at Scott, Saskatchewan, Canada. Wheat production and N use, and their response to N fertilizer or tillage, were largely influenced by water availability. Wheat N uptake and remobilization were strongly correlated with normalized rainfall in May and June (r = 0.985 and 0.935, respectively, both significant at the P = 0.01 level). In a moisture-stressed year (2003), grain yield was higher under NT than CT, and fertilizer N was ineffective due to low N demand. Nitrogen application increased shoot dry matter (DM), and N uptake and remobilization only in 2006, a year with near-average precipitation. In a wet and cool year (2005), wheat showed no response to tillage or fertilizer N as available soil N was high. Root DM and N content varied slightly only with year or treatment. When N uptake at heading was substantially greater than 100 kg ha−1, N loss occurred during plant senescence, and it was higher with N fertilization: in 2005 and 2006, N-fertilized wheat lost 33–35 kg N ha−1. Nitrogen use efficiency was: (1) higher under NT than CT, due to higher N utilization efficiency, (2) higher with no added N due to higher uptake and utilization efficiencies, and (3) low when water availability was low or excessive. Tillage system had little effect on the uptake, remobilization or loss of N. Fertilizer N application in a year with average rainfall increased wheat production, N accumulation and remobilization, and N loss during senescence.

Fluctuations in annual cycles and inter-seasonal memory in West Africa: rainfall, soil moisture and heat fluxes

Annual cycle and inter-seasonal persistence of surface-atmosphere water and heat fluxes are analyzed at a 5-day time step over the West African Monsoon (WAM) through observational precipitation estimates (CMAP), model datasets (NCEP/DOE level 2 reanalyses) and a Soil Water Index (SWI) from the ERS scatterometer. Coherent fluctuations (30–90 days) distinct from supra-synoptic variability (10–25 day periods) are first detected in the WAM precipitation and heat fluxes over the period 1979–2001. During all the northward excursion of the WAM rain band, a succession of four active phases (abrupt rainfall increases) occurs. They are centered in the first days of March, mid-April, the second half of May and from the last week of June to mid-July (the Sahelian onset). A simple statistical approach shows that the Spring to Summer installation of the monsoon tends to be sensitive to these short periods. Other analyses suggest the existence of lagged relationship between rainfall amounts registered in successive Fall, Spring (active periods) and Summer (top of the rainy season) implying land surface conditions. The spatial extension of the generated soil moisture anomalies reaches one maximum in March, mainly at the Guinean latitudes and over the Sahelian belt where the signal can persist until the next monsoon onset. Typically after abnormal wet conditions in September–October two signals are observed: (1) more marked fluctuations in Spring with less (more) Sahelian rainfall in May (June and after) at the Sahelian-Sudanian latitudes; (2) wetter rainy seasons along the Guinean coast (in Spring and Summer with an advance in the mean date of the ‘little dry season’). The reverse arises after abnormal dry conditions in autumn.

Recent yield results and trends over time with conservation tillage on morainic loam soil in southeast Norway

Results for 1998–2004 are reported from four long-term (25–28 years) tillage trials, comparing conventional autumn ploughing with reduced tillage, normally spring harrowing only. Plant residues were retained during the period studied. The weather was somewhat wetter than the 1961–1990 normal. Results with reduced tillage were mostly similar to those seen in earlier trial periods. In Trial 1, mean grain yield was 95% with spring harrowing only versus autumn ploughing, 96% when harrowing in autumn was performed as well and 97% when the soil was ploughed every third year. In Trial 2 positive crop rotation effects were found both with and without ploughing, and reduced tillage gave 5% lower grain yield also in this trial. In Trial 3, tillage system did not affect yields of cereals grown in rotation with potatoes, but reduced tillage gave 12% lower potato yield than ploughing. Little difference in response to N fertilizer was found. In Trial 4, reduced tillage on large-scale (0.7 ha) plots gave 11% lower grain yields than annual ploughing, partly due to shallow sowing depth. No long-term trend in yield responses to tillage was discernible in any trial, and between-year variability was similar with both ploughing and reduced tillage. Percentage yields with reduced tillage relative to annual ploughing correlated positively with rainfall in May and with mean air temperature in August. It is concluded that the reduced tillage systems studied are sustainable in terms of productivity, relative to labour, machinery and energy inputs. Likely benefits of such systems include higher levels of organic matter and aggregate stability in surface soil horizons, but a disadvantage is the need for frequent herbicide use to control perennial weeds.

Seasonal cambial activity and tree-ring formation of Pinus merkusii and Pinus kesiya in Northern Thailand in dependence on climate

This study is aimed at characterizing the cambial dynamics and its dependence on climate of two pine species native to Thailand, Pinus merkusii and Pinus kesiya and at describing their climatic response over 148 years. The samples for cambial activity analysis were taken monthly from March 2000 to February 2001, and the cambial activity was determined by counting the number of undifferentiated cell layers between mature xylem and phloem in transverse sections. Statistical analysis was done using Pearson's correlation. For the dendroclimatological analysis, samples were collected from the same sites in March 2004, and dendroclimatological standard techniques were applied. The results indicated that soil moisture influenced the cambial activity of P. merkusii and P. kesiya, however that rainfall and temperature had no significant effect on the cambial activity of both species. The response function described the relationship between tree-ring widths indices and monthly rainfall and temperature and revealed that the growth of P. merkusii at Hung Boung depended positively from rainfall in May. P. merkusii at Bao Kaew, however, had a positive correlation with rainfall from previous November to current July, whereas temperature in the preceding autumn and winter should be above-average and in the current spring and summer should be below-average. P. kesiya at Nong Kra Ting showed a slightly positive correlation with rainfall from February to June, but a strong dependence on rainfall in September. It can be concluded that the study of cambial activity could support our understanding of intra-annual variations and duration of tree-ring development, whereas the response function could help explain the average response of tree-growth to climate.

Seasonal influence of ENSO on the Atlantic ITCZ and equatorial South America

In late boreal spring, especially May, a strong relationship exists in observations among precipitation anomalies over equatorial South America and the Atlantic intertropical convergence zone (ITCZ), and eastern equatorial Pacific and central equatorial Atlantic sea surface temperature anomalies (SSTA). A chain of correlations of equatorial Pacific SSTA, western equatorial Atlantic wind stress (WEA), equatorial Atlantic SSTA, sea surface height, and precipitation supports a causal chain in which El Niño/Southern Oscillation (ENSO) induces WEA stress anomalies, which in turn affect Atlantic equatorial ocean dynamics. These correlations show strong seasonality, apparently arising within the atmospheric links of the chain. This pathway and the influence of equatorial Atlantic SSTA on South American rainfall in May appear independent of that of the northern tropical Atlantic. Brazil's Nordeste is affected by the northern tropical Atlantic. The equatorial influence lies further to the north over the eastern Amazon and the Guiana Highlands.

Comparison of Aerially-Applied Gypchek Strains Against Gypsy Moth (Lepidoptera: Lymantriidae) in the Presence of an Entomophaga maimaiga Epizootic

The standard strain (LDP-226) of Gypchek®, a nucleopolyhedrovirus product registered by the USDA Forest Service against the gypsy moth, Lymantria dispar (L.), was compared against a strain, LdMNPV-203NL (NL = nonliquefying), that was developed for production in cell culture. Both strains were applied by air to U.S. government property in Prince Georges Co., MD, in early May 2003 at the rate of 1 × 1012 occlusion bodies per ha. The two goals of the study were (1) to compare the first and second wave effects of the two strains against gypsy moth populations; and (2) to delineate the combined effects of the applied virus and the expected epizootic of the gypsy moth specialist fungal entomopathogen Entomophaga maimaiga Humber, Shimazu, and Soper. Heavy rainfall in May and June preceded a massive epizootic of E. maimaiga, whose effects did not mask the first wave of viral mortality. When the effect of application sequence was considered, it was concluded that the two strains were equivalent in their first-wave impacts. High fungal-induced mid and late-season gypsy moth larval mortality suppressed the second wave of virus at all evaluation sites. There were no obvious differences in the second waves engendered by the two LdNPV strains in the greatly reduced late-instar larval population.

Factors controlling the timing of major spring bloom events in an UK south coast estuary

Factors controlling the timing of major (>10 mg chlorophyll a m −3) spring bloom events in the estuarine waters of the Solent, on the south coast of the UK, have been investigated. Winter to summer variations in chlorophyll a concentration together with relevant meteorological and hydrographical data have been analysed for 5 years (1988, 1992, 2001, 2002 and 2003). Mean water column irradiance is demonstrated to be the main factor controlling the timing of the first major spring bloom event, usually dominated by large chain-forming diatoms. When chlorophyll a concentration first exceeds 10 mg m −3 in spring (usually in May) the mean water column photosynthetic active radiation (PAR) averaged for one week prior to the sampling date was always >380 W h m −2 d −1. Prior to the main spring bloom event surface incident radiation and water turbidity combine to limit chlorophyll a concentration to levels <10 mg m −3. Chlorophyll a concentrations >10 mg m −3 do not occur in the Solent until almost the entire 10 m water column is within the euphotic zone (i.e. above 1% light level) and light extinction coefficient ( k) is ca. ≤0.5 m −1. Statistically, river flow explains the largest percentage of the variations in k and the delayed bloom in June 2002 is due to increased cloud cover and high levels of rainfall in May, which caused a reduction in surface incident irradiance and increased turbidity. Chlorophyll a peaks during these major bloom events generally occur on spring tides when increased mixing rates favour net growth of diatoms.

04/00897 GIS-based methodology for Chernobyl contaminated land management through biomass conversion into energy — a case study for Polessie, Ukraine: Goor, F. et al. Biomass and Bioenergy, 2003, 25, (4), 409–421

We observed the relationship between present-day 137Cs surface activity and the rainfall in May 1986 to establish a relevant map of 137Cs deposition over eastern France. This study was performed in an area of the lower Rhône valley where clayey soils are assumed to trap caesium efficiently. Based on the rainwater/airborne activity ratio deduced from this relationship, we verified that present-day activities, measured in clayey soils of this type, are relatively representative of the initial depositions. The interlocked contaminated areas of the resulting map can be related to rainfall occurrences, as is the case for all countries affected by the Chernobyl fallout. This map can be reasonably compared with those obtained for countries bordering France in terms of both activity levels and extent of homogeneous activity areas. Lastly, we demonstrate that it would not be possible to produce a coherent map of initial fallout by extending the campaign over the whole of the eastern territory based on present-day soil activity measurements alone. Hence, only the relationship between 137Cs deposition and the rainfall of the first week of May 1986 can be used to construct a map depicting the Chernobyl fallout over eastern France.

Design of a Regional Climate Model for the Simulation of South China Summer Monsoon Rainfall

The objective of this study is to modify a regional climate model (RCM)—the Regional Climate Model of the National Climate Center of China—to simulate the summer monsoon rainfall over South China and the South China Sea. Such a modification is necessary because this RCM was designed for studying the climate over central and north China where precipitation processes are very different from those occurring further south so that simulations using the basic parameters of the original model give precipitation amounts much less than those observed.Using the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data, many sensitivity experiments have been carried out for the months of April to June 1998, which include modifying the cumulus parameterization scheme, the large-scale precipitation scheme, the radiation scheme, the surface exchange processes, and the size of the buffer zone. The design of all the experiments is either to enhance the moisture provision to the atmosphere over South China and the South China Sea, or to help the model atmosphere realize the moisture to form precipitation. It is found that indeed modifications to the various parameters can produce rainfall amounts much closer to those observed.Based on the results of these experiments, an “optimal” design of the RCM is reached and tested for its effectiveness using the NCEP reanalyses for two wet years (1994 and 1997) and two dry years (1996 and 1999) during which rainfall in May and June over South China were above/below normal respectively. The physical processes in this design include the Kuo scheme for convective precipitation, the Pal scheme for large-scale precipitation, the Holtslag scheme for the planetary boundary layer, the radiation transfer scheme of the NCAR Community Climate Model Version 3, and the Biosphere-Atmosphere Transfer Scheme for the land surface process. The width of the buffer zone is reduced and the effective cloud droplet radius is fixed at different values over land and ocean. The neutral drag coefficient is prescribed as a function of surface wind speed, and the heat and moisture exchange coefficients are set at values larger than that of momentum. The simulations based on this design for all the five years are found to be much closer to observations than those from the control.

Rendimento de grãos de trigo e sua relação com as doenças e variáveis climáticas em Capão Bonito de 1994 a 2001

A influência do ambiente no rendimento de grãos de genótipos de trigo e sua relação com as doenças causadas pelos fungos causadores da ferrugem-da-folha e das manchas foliares e suas relações com as variáveis climáticas foram avaliadas no período de 1994-2001, no município de Capão Bonito (SP), latitude 24º02' S, longitude 48º 22' W e altitude 702 m. A interação genótipos x anos foi altamente significativa revelando que diferenças climáticas anuais tiveram influência direta no rendimento de grãos. Em 1998, o rendimento médio de grãos foi o melhor do período e em 1994, o pior. Os genótipos IAPAR 60, IAC 60, IAC 120 e BR 18 apresentaram maior rendimento de grãos na média dos anos considerados. IAPAR 60 mostrou instabilidade no rendimento de grãos no período. Os genótipos Anahuac, IAC 120, IAC 356, IAC 342 e IAC 373 foram imunes às raças prevalentes do fungo causador da ferrugem-da-folha. Como as manchas foliares foram favorecidas pelas condições climáticas, sua ocorrência foi generalizada no período. As precipitações pluviais de maio foram as que melhor se correlacionaram com o desenvolvimento dessa doença.

Mapping of 137Cs deposition over eastern France 16 years after the Chernobyl accident

We observed the relationship between present-day 137Cs surface activity and the rainfall in May 1986 to establish a relevant map of 137Cs deposition over eastern France. This study was performed in an area of the lower Rhône valley where clayey soils are assumed to trap caesium efficiently. Based on the rainwater/airborne activity ratio deduced from this relationship, we verified that present-day activities, measured in clayey soils of this type, are relatively representative of the initial depositions. The interlocked contaminated areas of the resulting map can be related to rainfall occurrences, as is the case for all countries affected by the Chernobyl fallout. This map can be reasonably compared with those obtained for countries bordering France in terms of both activity levels and extent of homogeneous activity areas. Lastly, we demonstrate that it would not be possible to produce a coherent map of initial fallout by extending the campaign over the whole of the eastern territory based on present-day soil activity measurements alone. Hence, only the relationship between 137Cs deposition and the rainfall of the first week of May 1986 can be used to construct a map depicting the Chernobyl fallout over eastern France.

Influence of man-made cuts on the stability of pyroclastic covers (Campania, southern Italy): a numerical modelling approach

Intense rainfall in May 1998 and December 1999 caused disastrous landslides in the Sarno-Quindici and Cervinara areas (Campania, southern Italy). The landslides began with slips of the local pyroclastic covers mantling the carbonate relief and then evolved into debris flows/avalanches. The study discussed in this paper used a numerical modelling approach to assess the influence of man-made cuts on the stability conditions of pyroclastic covers. The model that was developed took into account initial failure conditions in order to better simulate the impact of man-made cuts along the slopes, with or without water seepage into the permeable pumiceous layers of the pyroclastic multilayer. Numerical analysis of stress-strain field clearly showed that tracks or geomorphological discontinuities had a negative impact on the multilayer stability conditions. Consequently, preservation of this vulnerable environment requires correct forest management practices.

Correlation of spring spore concentrations and meteorological conditions in Tulsa, Oklahoma.

Different spore types are abundant in the atmosphere depending on the weather conditions. Ascospores generally follow precipitation, while spore types such as Alternaria and Cladosporium are abundant in dry conditions. This project attempted to correlate fungal spore concentrations with meteorological data from Tulsa, Oklahoma during May 1998 and May 1999. Air samples were collected and analyzed by the 12-traverse method. The spore types included were Cladosporium, Alternaria, Epicoccum, Curvularia, Pithomyces, Drechslera, smut spores, ascospores, basidiospores, and other spores. Weather variables included precipitation levels, temperature, dew point, air pressure, wind speed, wind direction and wind gusts. There were over 242.57 mm of rainfall in May 1999 and only 64.01 mm in May 1998. The most abundant spore types during May 1998 and May 1999 were Cladosporium, ascospores, and basidiospores. Results showed that there were significant differences in the dry-air spora between May 1998 and May 1999. There were twice as many Cladosporium in May 1998 as in May 1999; both ascospores and basidiospores showed little change. Multiple regression analysis was used to determine which meteorological variables influenced spore concentrations. Results showed that there was no single model for all spore types. Different combinations of factors were predictors of concentration for the various fungi examined; however, temperature and dew point seemed to be the most important meteorological factors.

Geophysical variables and behavior: XCV. Annual January rainfall may modulate the incidence of luminous phenomena within the San Francisco Basin.

The role of precipitation as a modulator of processes that influence the numbers of reports of anomalous luminous phenomena was investigated within the San Francisco Basin for the years 1950 through 1969. More than 50% of the variance in the numbers of these reports was accommodated by the amount of rainfall during the months of January. The relationship was strongest for events within 100 km of the city. Years in which January rainfall exceeded 8.5 in. and the numbers of earthquakes within the basin increased were associated with the largest numbers of general reports within 400 km from the city, particularly if the previous year had been drier and displayed less seismic activity. Application of the equation to years 1970 through 1995 predicted that above average (z score > 1.5) numbers of luminous displays should have occurred during the years 1973, 1993, and 1995. The results support the corollary of the tectonic strain theory that fluid injection or hydrological loads, natural or man-made, can affect the processes of tectonic strain which facilitate the creation of unusual luminous phenomena.

Semi-volatile organic compounds in the campaspe river system (Victoria, Australia)

The levels of semi-volatile organic compounds (SVOCs) in the Campaspe River system, North Central Victoria, Australia, were monitored from January to September 1995, and the environmental trends and sources of these compounds were determined. The land use within particular catchments dictated the complexity of the SVOCs in run-off water. Run-off from native forest contained the greatest number of SVOCs. Soil and ground litter were shown to contain the greatest complexity of SVOCs, mostly terpenes. However, only a small proportion were leached by run-off with the remainder being tightly bound to the soil or volatilizing to the atmosphere. Under the prevailing drought of early 1995, the rivers contained no detectable SVOCs until the first catchment run-off after significant rainfall in May. The maximum complexity and concentration of the SVOCs coincided with extensive run-off after heavy rainfall in June, effecting a surge of SVOCs with the flood peak. Fatty acids, their amides and hydrocarbons made up the majority of the compounds identified and were in the 1-39μg/l concentration range. The levels then diminished as the catchment was flushed by continual run-off. These results support Lake's 1967 hypothesis that natural floodwaters contain a signature of SVOCs entering from the catchment. The downstream passage of these compounds was obstructed by a man–made storage, Lake Eppalock, with only low concentrations of SVOCs (1–3μg/l) in the outflow, displaying no correlation to run-off.

Crop canopy development and structure influence weed suppression

Weed suppression characteristics of different winter cereal species and cultivars were studied in two field experiments in two successive years. Two cultivars each of barley, oats and wheat were studied using the weed Galium aparine L. at a range of densities. Significant differences were found in the suppressive abilities of the crop species: oats being the most suppressive, followed by barley and then wheat. Percentage yield loss was related to G. aparine density using a rectangular hyperbolic model. In 1995–96, significant differences between the two wheat cultivars were found, with cv. Avalon being able to suppress G. aparine growth much more effectively than cv. Spark. However, in 1996–97, high rainfall in May, June and July enabled G. aparine to escape suppression by the cultivars. Cultivar competitive ability was associated with high overall leaf area, resistance to loss of tillers under competitive pressure, greater height, canopy structure and development. The oat cultivars were more competitive at early growth stages than could be accounted for by their canopy structure; the possible contribution of allelopathic exudates to their suppressive ability is discussed.

Early survival in roe deer: causes and consequences of cohort variation in two contrasted populations.

Time- and sex-specific summer survival of roe deer fawns was estimated using capture-mark-recapture methods in two enclosed populations living in contrasting conditions. The population of Trois Fontaines (eastern France) was roughly constant in size throughout the study period, while in Chizé (western France), the population experienced frequent summer droughts and numbers decreased continuously during the study. Early survival of fawns was low and highly variable over the years at both Chizé and Trois Fontaines, and demonstrated marked variations between cohorts that need to be taken into account when modelling roe deer population dynamics. In Trois Fontaines, fawn survival was positively correlated with early body growth and total rainfall in May and June. In Chizé, fawn survival decreased with increasing density and tended to increase with increasing rainfall in May and June and adult female body mass. These factors explained more than 75% of the variability in early survival observed in both populations. Variation between cohorts had different consequences for the two populations. At Trois Fontaines, cohort variation was limited to a numerical effect on early survival. However at Chizé, cohort variation was long-lasting and affected the phenotypic quality of survivors at later ages, and thereby future survival and breeding abilities (both numerical and quality effects). Male and female fawns had similar survival over their first summer in both populations. This result contrasts with the lower survival of young males often observed in ungulates. Two ultimate causes can be proposed to account for the low and variable survival of roe deer fawns over the first summer: the high energy expenditures incurred by does during each breeding attempt and/or the low absolute body size of newborn roe deer fawns.

An Outbreak of Hantavirus Pulmonary Syndrome in Western Paraguay

During an investigation of hantavirus pulmonary syndrome (HPS) in Paraguay in 1995, sera from persons with HPS-like illness, houshold contacts of confirmed HPS case-patients, and a sample of the area residents were analyzed by ELISA for antibodies to Sin Nombre virus (SNV). Rodent serosurveys and analysis of precipitation records were also conducted. Twenty-three of 24 available probable cases were SNV antibody-positive, 17 of whom were ill between July 1995 and January 1996. Four (14.8%) of 27 case-contacts and 44 (12.8%) of 345 community residents were also seropositive. Calomys laucha (vesper mouse) was the most common rodent species captured and the most frequently SNV-seropositive. Rainfall in May 1995 was 10-fold greater than that seen in May over the preceding 11 years. This 17 case-cluster represents the largest documented outbreak since HPS was first recognized in 1993. Calomys laucha is the likely primary rodent reservoir for a SNV-like hantavirus in western Paraguay. Fluctuations in monthly precipitation rates may have contributed to increased risk for HPS in this region.