Cattle and pastoralism: Survival and production in arid lands

Traditional subsistence pastoralists in East Africa tend to keep large herds, milk cattle in preference to eating them, and subject them to long foraging treks. Such practices are widely considered ill-suited to arid lands and are believed to arise because cattle are raised more for social prestige than food production. Whether this is true can only be judged by considering the responses of cattle to arid zones and, given the herder's goals and options, his management practices. In considering these factors, we show that indigenous East African cattle demonstrate energy-sparing capabilities during drought. Pastoralists can therefore herd cattle at great distances from water at little more cost than animals on the normal maintenance diet and watered more frequently. The physiological response of cattle to drought, the ecological constraints imposed by livestock and wildlife competition, and the energetic efficiency of mixed milk and meat pastoralism explain why herders traditionally select their characteristic management practices.     

Do photosynthetic limitations of evergreen Quercus ilex leaves change with long‐term increased drought severity?

Seasonal drought can severely impact leaf photosynthetic capacity. This is particularly important for Mediterranean forests, where precipitation is expected to decrease as a consequence of climate change. Impacts of increased drought on the photosynthetic capacity of the evergreen Quercus ilex were studied for two years in a mature forest submitted to long‐term throughfall exclusion. Gas exchange and chlorophyll fluorescence were measured on two successive leaf cohorts in a control and a dry plot. Exclusion significantly reduced leaf water potential in the dry treatment. In both treatments, light‐saturated net assimilation rate (A_max), stomatal conductance (g_s), maximum carboxylation rate (V_cmax), maximum rate of electron transport (J_max), mesophyll conductance to CO₂ (g_m) and nitrogen investment in photosynthesis decreased markedly with soil water limitation during summer. The relationships between leaf photosynthetic parameters and leaf water potential remained identical in the two treatments. Leaf and canopy acclimation to progressive, long‐term drought occurred through changes in leaf area index, leaf mass per area and leaf chemical composition, but not through modifications of physiological parameters.     

Seasonality and reproduction in aphids

Aphids are short-lived and occupy habitats which vary in quality in both time and space. They exploit their ephemerally nutritious habitats by rapidly producing many small offspring when conditions are good, and fewer, larger offspring when conditions are poor, at which time they also divert more of their resources into fat storage. Aphids of each of the generations which make up a life cycle have specific reproductive strategies adapted to the conditions they are most likely to encounter, that is they anticipate the predictable seasonal trends in habitat quality.     

Group A rotavirus and norovirus display sharply distinct seasonal profiles in Belém,northern Brazil

Several viruses have been associated with acute gastroenteritis (AGE), and groupA rotavirus (RVA) and nor-ovirus (NoV) are the most prevalent. This study aimedto assess their prevalence among children hospitalised for diarrhoea during athree-year surveillance study. From May 2008-April 2011, overall positivityrates of 21.6% (628/2904) and 35.4% (171/483) were observed for RVA and NoV,respectively. The seasonality observed indicated distinct patterns when bothviruses were compared. This finding may explain why hospitalisation for AGEremains constant throughout the year. Continuous AGE monitoring is needed tobetter assess the patterns of infection.     

Different growth responses of C3 and C4 grasses to seasonal water and nitrogen regimes and competition in a pot experiment

Understanding temporal niche separation between C₃ and C₄ species(e.g. C₃ species flourishing in a cool spring and autumn whileC₄ species being more active in a hot summer) is essential forexploring the mechanism for their co-existence. Two parallelpot experiments were conducted, with one focusing on water andthe other on nitrogen (N), to examine growth responses to wateror nitrogen (N) seasonality and competition of two co-existingspecies Leymus chinensis (C₃ grass) and Chloris virgata (C₄grass) in a grassland. The two species were planted in eithermonoculture (two individuals of one species per pot) or a mixture(two individuals including one L. chinensis and one C. virgataper pot) under three different water or N seasonality regimes,i.e. the average model (AM) with water or N evenly distributedover the growing season, the one-peak model (OPM) with morewater or N in the summer than in the spring and autumn, andthe two-peak model (TPM) with more water or N in the springand autumn than in the summer. Seasonal water regimes significantlyaffected biomass in L. chinensis but not in C. virgata, whileN seasonality impacted biomass and relative growth rate of bothspecies over the growing season. L. chinensis accumulated morebiomass under the AM and TPM than OPM water or N treatments.Final biomass of C. virgata was less impacted by water and Nseasonality than that of L. chinensis. Interspecific competitionsignificantly decreased final biomass in L. chinensis but notin C. virgata, suggesting an asymmetric competition betweenthe two species. The magnitude of interspecific competitionvaried with water and N seasonality. Changes in productivityand competition balance of L. chinensis and C. virgata undershifting seasonal water and N availabilities suggest a contributionof seasonal variability in precipitation and N to the temporalniche separation between C₃ and C₄ species. Key words: Chloris virgata, competition, growth, Leymus chinensis, nitrogen seasonality, water seasonality Received 19 November 2007; Revised 29 January 2008 Accepted 4 February 2008     

Short-term fluctuations in benthic diatom numbers on an intertidal sandflat in the Westerschelde estuary (Zeeland,The Netherlands)

During the period March–May 1991, sediment samples were taken every two or three days at one intertidal station in the brackish part of the Westerschelde estuary. Quantitative cell counts were made in order to investigate the short-term temporal changes in diatom numbers and assemblage structure.Throughout the whole sampling period, the diatom assemblage was dominated by epipsammic diatoms. Three species, Achnanthes delicatula, Opephora cf. perminuta and Catenula adhaerens on average accounted for almost 67% of all valves counted. The epipsammic diatom fraction showed no significant changes in absolute numbers; its species composition appeared relatively stable. In contrast, epipelic diatom densities significantly increased towards the end of the study period. Species composition within this fraction was less stable. Multivariate analysis (Principal Components Analysis), in combination with multiple regression, indicated that total sky irradiance (on the second and third day preceding sampling) and percentage organic matter were related to the short-term fluctuations of the epipelic diatom fraction.     

Seasonal occurrence of water-borne fungi in Konaje stream (Mangalore), India

The Konaje stream near Mangalore University Campus has been surveyed during 1980–1981 for the occurrence of water-borne fungi by using three methods: leaf litter observations, foam analysis and water filtration. A total of twenty species of fungi has been recorded. Three species of fungi, Lunulospora curvula, Triscelophorus monosporus and Triscelophorus sp. were found to occur throughout the year. In all three methods Lunulospora curvula occurred in highest frequency. The occurrence of different species was found to correlate with the rainfall and leaf deposition in this region and not with water temperature.     

Particulate phosphorus in the Humber estuary

The biogeochemical controls on particulate phosphorus distribution in the Humber estuary have been investigated with regard to salinity and season. Surveys of the Humber were conducted in August 1991 and January, March and June 1992. Samples were collected for particulate phosphorus, dissolved phosphorus, suspended load and salinity analysis. Particulate phosphorus forms 16 to 93% of the total phosphorus present in the water column of the Humber estuary. Total particulate phosphorus concentrations in the Humber ranged from 1 to 45 μmol l⁻¹. This range is comparable to that observed in similar sized industrialized estuaries of the U.S.A. and northern Europe. Flocculation at low salinities was found to be a major influence on particulate phosphorus concentrations. Highest concentrations of particulate phosphorus were found in reaches below a salinity of 5 and may result in phosphorus being trapped in the sediments of the estuary. There is evidence that this phosphorus may be released as oxygen concentrations decrease during the summer. Suspended load, adsorption/desorption equilibrium and external inputs were also found to influence the particulate phosphorus concentrations.     

Induction of Early Seasonal Sensitivity to Melatonin in Suffolk-Cross Ewes

Anoestrous Suffolk-Cross ewes can be induced into early seasonal ovarian activity by administration of melatonin at the appropriate time of day or by melatonin implants. This treatment is successful if commenced in June, but not earlier in April or May and suggests that a critical period of long days may be necessary before artificial short-day melatonin profiles act as winter time-cues. We have investigated whether the lack of sensitivity to melatonin in April could be overcome in ewes in which breeding activity had been artificially moved forward the previous season. The results indicate that this was indeed the case and that the breeding season in untreated ewes which also previously experienced an early induced breeding season reverted to the normal timing for the Suffolk-Cross breed.     

Effects of changing photoperiods in the life cycle regulation of the comma butterfly, Polygonia c-album (Nymphalidae)

Abstract. 1. Regulation of adult reproductive diapause and seasonal polyphenism was studied in two populations of the comma butterfly, Polygonia c-album (L.) (Nymphalidae), from Stockholm, Sweden, and Oxford, England.
2. In the univoltine Stockholm population short and long constant day-lengths (in the range 12–22 h) at 20°C were ineffective in averting the production of the dark, generally diapausing, morph, but the non-diapausing light morph could be produced if daylengths were increased during larval development. The procedure was especially effective with increases from 12 to 22 h, but the tendency was the same with a more realistic increase, from 18 to 20 h.
3. In the partially bivoltine English population a critical constant day-length for morph and diapause induction was found between 12 and 18 h. Decreasing daylengths above the critical daylength early or late in larval development resulted in production of the diapausing morph.
4. These results suggest a system for environmental control where day-lengths which increase throughout the larval period indicate an early date before summer solstice, meaning that there is sufficient time for a second generation of offspring to reach the hibernating adult stage before winter. The ecological significance of the results is discussed.     

Changes in marriage seasonality among some european rural populations

The preservation or the change of the population structure is often strictly related to the acquisition or loss of behavioural models: the choice of the wedding period is among them. Analysing the period in which people marry, it is possible to point out modifications in the economy, in the work calendar and it also can be helpful to determine the importance of religious traditions. In this work, the authors study the marriage seasonality of nine rural European populations in France, Spain and Italy and its evolution during the last two centuries. The research has allowed to point out three different patterns of marriage seasonality: the Autumn marriage, the Winter marriage and populations with no remarkable seasonal variations. The first distribution results from the combination of work calendar, harsh climate in winter and religious traditions (the month of May consacrated to Maria, the Lent and Advent period), while the second one is due mostly to summer migrations. The importance of these factors tend to reduce during the XX century, making the distributions more homogeneous.