Seasonal variations in the conception rate of beef cattle in the seasonal—equatorial climate of southern nigeria

Seasonal variations in the frequency of conceptions were analysed from the records of 8,971 beef calves born over a period of ten years (1959–1968) in the Southern Guinea Savannah of Nigeria. Mean annual and monthly conception rates were 72 and 6%, respectively. Highly significant changes in conception rates were observed: the highest number of conceptions occurred in April (7.3%) and the lowest in October (4.4%). The cubic function of the curve depicting the monthly conception rate was highly significant (p < 0.001) and parallelled the change in photoperiod (r = +0.39, p < 0.01). Conception rate was not related to either temperature or precipitation. The evidence suggests a photoperiodic influence on conception rates.

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Zusammenfassung Saisonale Schwankungen in der Konzeptionsrate von Fleischrindern der Guineasavanne Südnigerias wurden anhand von 8.971 Kalbungen aus zehn Jahren (1959–1968) untersucht. Die durchschnittlichen jährlichen und monatlichen Konzeptionsraten betrugen 72 beziehungsweise 6%; jedoch wurden hochsignifikante Abweichungen (p < 0.001) von dem monatlichen Mittelwert festgestellt: die höchste Konzeptionsrate wurde mit 7,3% für April, die niedrigste mit 4,4% für Oktober errechnet. Die mathematische Funktion der Konzeptionsrate folgt einer Sinuskurve, welche der monatlichen Veränderung der Tageslichtlänge parallel läuft (r = +0,39, p < 0.01). Die Konzeptionsrate war nicht mit der Durchschnittstemperatur oder den Niederschlägen korreliert. Diese Ergebnisse lassen vermuten, dass die saisonalen Schwankungen in der Konzeptionsrate zumindest teilweise auf photoperiodische Veränderungen zurückzuführen sind.

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Resume Les variations saisonnières du taux de fécondité de bovins de la savanne du sud de la Guinée (Nigéria) ont été étudiées sur la base de 8971 mises bas ayant eu lieu durant une période de 10 ans. Le taux de fécondité moyen fut de 72% pour l'année et de 6% pour chaque mois. On constate pourtant des différences significatives entre les différents mois: le taux le plus élevé se trouve en avril (7,3%) et le plus bas en octobre (4,4%). La fonction du troisième degré du taux de fécondité est hautement significative (p < 0,001). Elle suit une courbe sinusöidale parallèle à celle de la longueur du jour (r = +0,39, p < 0,01). Il n'y a pas de relation entre le nombre de conceptions et la température ou les précipitations. Par conséquent, seul le photopériodisme semble influencer le nombre des conceptions.

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The permission of the Western Nigeria Development Corporation to analyse and publish their breeding records is gratefully acknowledged.     

What is the function of nitrogen catabolite repression in Saccharomyces cerevisiae?

In contrast to the previously held notion that nitrogen catabolite repression is primarily responsible for the ability of yeast cells to use good nitrogen sources in preference to poor ones, we demonstrate that this ability is probably the result of other control mechanisms, such as metabolite compartmentation. We suggest that nitrogen repression is functionally a long-term adaptation to changes in the nutritional environment of yeast cells.     

Vibrational distribution of nitrogen molecules in the C3Πu state in a near-surface microwave plasma in nitrogen at pressures of 1–5 Torr

The radiation of the second positive nitrogen system has been used to study the spatial dependence of the vibrational distribution of nitrogen molecules in the C³Π_u state in the near-surface plasma layer of an electrode microwave discharge in nitrogen at pressures of 1–5 Torr. It has been shown that the vibrational distribution changes at a scale of 100 μm. It has been concluded that this state is populated owing to the electron impact from the ground state. The possibility of using the local approximation for the electron energy distribution function to explain the experimental results has been analyzed.     

Determining the climate impact of food for use in a climate tax—design of a consistent and transparent model

The International Journal of Life Cycle Assessment - The aim of this study was to determine transparent food carbon footprint values for use in a climate tax, using a consistent methodology across...     

Temperature-sensitive photosynthesis-deficient mutants of the cyanobacteriumAnabœna variabilis impaired in nitrogen assimilation

Temperature-sensitive (Ts) mutants ofAnabœna variabilis exhibited differences in the rates of oxygen evolution at 28 and 40°C. They were unable to perform photosynthesis and nitrogen fixation at 40°C beyond a period of 3 d in a nitrogen-deficient medium. However, the addition of combined nitrogen sources enhanced the growth of all the Ts mutants at both temperatures. Studies on nitrate uptake ty Ts mutants revealed the existence of a low affinity system, whereK _m values were found to be lower than 1 mmol/L. The activity of nitrate reductase gradually increased with time at 28°C with the exception of Ts-161 where the activity decreased with time at 40°C. The rate of ammonia uptake byA. variabilis and its Ts mutants greatly differed and the results suggest the existence of a single phase of uptake. The activity of glutamate-ammonia ligase (GAL) of the parent and Ts mutants was slightly higher in cells from nitrogen-deficient medium when compared to nitrate grown cells at 28°C. At 40°C, the GAL activity decreased after 3 d. The inability of the Ts mutants to grow at 40°C appears to be due to an impairment in nitrogen asimilation.     

Role of school climate and personality in the development of Czech adolescents’ political self-efficacy

This study examined the effects of school climate (open classroom and positive student relationships) and personality dispositions (shyness and need for cognition) on adolescents’ political self-efficacy. Data were collected in 2014 from 1,954 Czech ninth- and tenth-graders (mean age?=?15.60). A multilevel analysis showed that school-level political self-efficacy predicted self-efficacy for local politics. However, schools and classrooms were rather homogeneous in terms of students’ mean political self-efficacy and students’ self-reported acquisition of civic skills at school. Hence, school characteristics had only limited associations with adolescents’ political self-efficacy. At the same time, students’ political efficacy had a considerable association with lower shyness and higher need for cognition. These results suggest that the development of political efficacy at school goes beyond simple general influences of school environment and individual differences between students must be considered.     

Inefficient nitrogen resorption in genets of the actinorhizal nitrogen fixing shrubComptonia peregrina: physiological ineptitude or evolutionary tradeoff?

Nutrient resorption was measured in an actinorhizal nitrogen-fixing shrub,Comptonia peregrina, for five years in the understory of a deciduous oak forest in Rhode Island, USA. Mean resorption of nitrogen was extremely inefficient (11%) compared to most deciduous species (50%+), yet resorption of phosphorus was efficient (53%) and comparable to other species. Of the seven additional nutrients studied, only copper (6%) and zinc (10%) were resorbed from senescing leaves. Resorption of nitrogen (5%–20%) and phosphorus (40%–71%) varied significantly among years. Copper was resorbed from leaves in three years and accreted into leaves in two years. Five-year resorption means differed among individual genets by as much as a factor of 2.5 for nitrogen, and 1.3 for phosphorus. Resorption of nitrogen, copper, and zinc were highly correlated, yet resorption of phosphorus remained autonomous from other nutrients. The ecophysiological tradeoffs inComptonia which have resulted in the cooccurence of actinorhizal nitrogen fixation, inefficient nitrogen resorption, and efficient phosphorus resorption suggest that plant nutrient status does have an impact on resorption efficiency and that the evolution of nutrient conservation strategies is nutrient-specific.     

Where did all the nitrogen go? Fate of nitrogen inputs to large watersheds in the northeastern U.S.A.

To assess the fate of the large amounts of nitrogen (N) brought into the environment by human activities, we constructed N budgets for sixteen large watersheds (475 to 70,189 km²) in the northeastern U.S.A. These watersheds are mainly forested (48–87%), but vary widely with respect to land use and population density. We combined published data and empirical and process models to set up a complete N budget for these sixteen watersheds. Atmospheric deposition, fertilizer application, net feed and food inputs, biological fixation, river discharge, wood accumulation and export, changes in soil N, and denitrification losses in the landscape and in rivers were considered for the period 1988 to 1992. For the whole area, on average 3420 kg of N is imported annually per km² of land. Atmospheric N deposition, N₂ fixation by plants, and N imported in commercial products (fertilizers, food and feed) contributed to the input in roughly equal contributions. We quantified the fate of these inputs by independent estimates of storage and loss terms, except for denitrification from land, which was estimated from the difference between all inputs and all other storage and loss terms. Of the total storage and losses in the watersheds, about half of the N is lost in gaseous form (51%, largely by denitrification). Additional N is lost in riverine export (20%), in food exports (6%), and in wood exports (5%). Change in storage of N in the watersheds in soil organic matter (9%) and wood (9%) accounts for the remainder of the sinks. The presence of appreciable changes in total N storage on land, which we probably under-rather than overestimated, shows that the N budget is not in steady state, so that drainage and denitrification exports of N may well increase further in the future.     

Sex-related,growth–climate association of Araucaria angustifolia in the neotropical ombrophilous woodlands of Argentina

Araucaria angustifolia is a dioecious dominant tree in araucaria forests in Brazil and Argentina, South America. The species is nowadays critically endangered by deforestation and global climate change. The goal of this study was to analyse the dynamics of radial growth in this species and its association with climatic variables, according to the sex, at its western range boundary in Argentina. Standard dendrochronological techniques were applied on stem disks from female and male trees. Xylem anatomical anomalies made the tree-ring dating process difficult. Female and male trees showed growth patterns that changed over time, not being significant in the 1950–1990 period and highly significant from the 1990s onwards (p < 0.1) when female trees had a higher growth rate. Female and male trees showed a different association with climatic variables. No significant effect of temperature and precipitation was identified on female trees. For male trees, rainfall had a positive effect in August, before the growing season, and a negative effect at the end of the growing season (March). Temperature had a negative effect on male trees, before and during the growing season (February and January, respectively). No effect of SOI was detected on both sexes. Results emphasised the usefulness of A. angustifolia for dendrochronological studies and the value of dioecious species for the study of sex-related growth–climate association.     

Are the patterns of regeneration in the endangered Eucalyptus gunnii ssp. divaricata shifting in response to climate?

Increasing drought frequency is a major driver of changes in forest structure and has been implicated in the decline of the endangered tree species, Eucalyptus gunnii ssp. divaricata (McAulay & Brett) in the Central Plateau region of Tasmania, Australia. In this study, we examined patterns of regeneration, aspects of the water relations of E. gunnii ssp. divaricata and its replacement Eucalyptus pauciflora and, whether shifts in stand dominance have occurred where the subspecies co‐occurs with E. pauciflora could be related to recent changes in climate. Successful E. gunnii ssp. divaricata seedling regeneration was restricted to micro‐sites with relatively deep soils within slight depressions. In contrast, poor E. gunnii ssp. divaricata regeneration and declining adult cohorts of this species all occurred on steeper, concave micro‐sites with shallow soils. This apparent shift in suitable regeneration micro‐site, from sites with shallow to deeper soils, may be linked to an observed 25% reduction in summer rainfall over the last 50 years. On slopes surrounding waterlogged depressions where E. gunnii ssp. divaricata co‐occurs with E. pauciflora, E. pauciflora was in higher abundance than E. gunnii ssp. divaricata in small adult and sapling size‐classes, compared with the adult cohorts (>30 cm d.b.h.), a trend consistent with a shift in stand dominance. Despite existing paradigms related to differential drought tolerance between these two species as a driver of this shift in stand dominance, there were no differences in predawn (Ψ_pd) water potentials between species. Furthermore, pressure–volume analysis showed that E. gunnii ssp. divaricata had lower values for osmotic potential at turgor loss point (?2.33 ± 0.06 MPa) than E. pauciflora (?2.13 ± 0.03 MPa), suggesting that E. gunnii ssp. divaricata may be more drought tolerant than E. pauciflora, in contrast to the prevailing paradigm that it is more susceptible to drought than E. pauciflora.     

Trends in atmospheric concentrations of weed pollen in the context of recent climate warming in Poznań (Western Poland)

A significant increase in summer temperatures has been observed for the period 1996–2011 in Poznań, Poland. The phenological response of four weed taxa, widely represented by anemophilous species (Artemisia spp., Rumex spp. and Poaceae and Urticaceae species) to this recent climate warming has been analysed in Poznań by examining the variations in the course of airborne pollen seasons. Pollen data were collected by 7-day Hirst-type volumetric trap. Trends in pollen seasons were determined using Mann–Kendall test and Sen’s slope estimator, whereas the relationships between meteorological and aerobiological data were established by Spearman’s rank correlation coefficient. Significant trends in pollen data were detected. The duration of pollen seasons of all analysed taxa increased (from +2.0 days/year for Urticaceae to +3.8 days/year for Rumex), which can be attributed to a delay in pollen season end dates rather than earlier start dates. In addition, the intensity of Artemisia pollen seasons significantly decreased and correlates with mean July–September daily minimum temperatures (r?=??0.644, p?Rumex pollen seasons. The results of this study show that observed shifts in weed pollen seasons in Poznań, i.e. longer duration and later end dates, might be caused by the recorded increase in summer temperature. This influence was the strongest in relation to Artemisia, which is the taxon that flowers latest in the year. The general lack of significant correlations between Rumex and Urticaceae pollen seasons and spring and/or summer temperature suggests that other factors, e.g. land use practices, could also be partially responsible for the observed shifts in pollen seasons.     

Dynamics of the ‘echo’ effect in a phytoplankton system with nitrogen fixation

Consideration of nitrogen fixation adds a positive nonlinear feedback to plankton ecosystem models. We investigate the consequences of this feedback for secondary phytoplankton blooms and the response of phytoplankton dynamics to physical forcing. The dynamics of phytoplankton, Trichodesmium (the nitrogen fixer), and nutrients is modeled with a system of three differential equations. The model includes two types of nonlinear interactions: the competition of phytoplankton and Trichodesmium for light, and the positive feedback resulting from Trichodesmium recycling. A typical simulation of the model in time, with forcing by a varying mixed-layer depth, reveals a clear successional sequence including a secondary or ‘echo’ bloom of the phytoplankton. We explain this sequence of events through the stability analysis of three different steady states of the model. Our analysis shows the existence of a critical biological parameter, the ratio of normalized growth rates, determining the occurrence of ‘echo’ blooms and the specific sequence of events following a physical perturbation. The interplay of positive and negative feedbacks appears essential to the timing and the type of events following such a perturbation.     

Wildfire occurrence in forests of the Altai–Sayan region under current climate changes

The dynamics of meteorological parameters in Siberia and the Altai–Sayan region in the 20^th–21^st centuries are analyzed. Significant trends characterizing the dynamics of the average temperature, precipitation, and standardized precipitation evapotranspiration index (SPEI) are revealed. Growing wildfire frequency in the area under study since the end of the 20^th century has been detected. The annual variation of wildfires has a phase coincidence with the dynamics of mean temperatures, positively correlates with climate dryness, and negatively correlates with averaged precipitation data. An abrupt increase in wildfire frequency has been observed in the late 20^th–early 21^st centuries. The spatial redistribution of wildfires in the Altai–Sayan region in the early 21^st century is revealed.     

Latitudinal shifts in the distribution of exploited fishes in Korean waters during the last 30 years: a consequence of climate change

Sea surface temperatures in Korean waters have increased by approximately 1 °C during the past 40 years, implying possible range shifts of marine fishes and invertebrates. We analyzed spatially explicit, commercial catch data for 12 major fish species collected from 1984 to 2010 in Korean waters to evaluate and project their range shifts based on climate-driven hydrographic changes simulated by a general circulation model under a climate change scenario. There were significant relationships between the mean latitude of the catch distribution and water temperature for seven of the 12 species examined. Our circulation model projected that temperature stratification in the Korea Strait will disappear by 2030, and our empirical relationships predicted that the ranges of five of the fish species examined will shift poleward by 19–71 km from the 2000s to the 2030s. Compared with studies of demersal fishes in the western North Atlantic and the North Sea, our estimated speeds of shift in mean latitude of fishes were, on average, slower by factors of 2.3 and 5.7, respectively. This suggests that the pattern of range shift of marine species can vary regionally, depending on oceanographic and geomorphologic conditions. International cooperative research among fisheries scientists from countries throughout the region, especially Japan and China, is required to more reliably and comprehensively assess and project the range shifts of fish species. This will provide a scientific basis for the development of fishery policies and their adaptation to climate change in the western North Pacific.     

A break in the nitrogen cycle in aridlands? Evidence from δp15N of soils

We examined the content and isotopic composition of nitrogen within soils of a juniper woodland and found that a cryptobiotic crust composed of cyanobacteria, lichens, and mosses was the predominant source of nitrogen for this ecosystem. Disturbance of the crust has resulted in considerable spatial variability in soil nitrogen content and isotopic composition; intercanopy soils were significantly depleted in nitrogen and had greater abundance of ¹⁵N compared to intra-canopy soils. Variations in the ¹⁵N/¹⁴N ratio for inter- and intra-canopy locations followed similar Rayleigh distillation curves, indicating that the greater ¹⁵N/¹⁴N ratios for inter-canopy soils were due to relatively greater net nitrogen loss. Coverage of cryptobiotic crusts has been reduced by anthropogenic activities during the past century, and our results suggest that destruction of the cryptobiotic crust may ultimately result in ecosystem degradation through elimination of the predominant source of nitrogen input.