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We reconstruct the eruptive chronology of the Yucamane–Calientes compound volcano in southern Peru based on extensive fieldwork and a large dataset of geochronological (K-Ar, 40Ar/39Ar, U-Pb, and 14C) and geochemical (major and trace element) analyses. This compound volcano is composed of two edifices that have experienced discontinuous volcanic activity from the middle Pleistocene to the Holocene. The Calientes volcano has been constructed in four successive stages: Calientes I is composed of andesitic lava flows dated at ~500 ka. Subsequently, the Callazas ignimbrite (Calientes II stage) was emplaced ~160–190 ka, followed by the main cone-building stage (Calientes III) at ~130–100 ka. Finally, the Holocene Calientes domes were emplaced and represent the last eruptive products of this edifice. The Yucamane volcano has been constructed in three stages: Yucamane I consists of a succession of andesitic lava flows exposed at the base of the volcano that are older than 40 ka. Yucamane II (~36–30 ka) comprises a thick sequence of block-and-ash-flow deposits that represents an episode of dome growth predating the younger Yucamane cone (Yucamane III) built after 20–25 ka. During the Holocene, Yucamane vulcanian to sub-Plinian activity has emplaced tephra-fall and pyroclastic-density-current deposits. The most recent explosive eruptions occurred ca. 3000 BP and emplaced a tephra-fall and pumice-flow deposits. Most samples from Calientes volcano are andesites and dacites (60.1–67.7 wt% SiO2), while rocks from Yucamane volcano are basaltic-andesites to dacites (53.4–66.9 wt% SiO2). The rocks have a mineral assemblage of plagioclase, amphibole, biotite, orthopyroxene, clinopyroxene, olivine, and Fe-Ti oxides. The analyzed samples are categorized within a high-K, calc-alkaline series. Calientes volcano erupted mostly andesitic magmas, but its history is punctuated by rare eruptions of silica-rich magmas. In contrast, Yucamane volcano follows a different trend characterized by a gradual decrease in silica content through post-glacial time, from the large (VEI 3) sub-Plinian andesitic eruption of ~3 ka to moderate (VEI ≤ 2) vulcanian eruptions of basaltic-andesitic. On the basis of such recurrent and recent (Holocene), low-to-moderate explosive activity, Yucamane must be considered an active and potentially threatening volcano, which may affect the province of Candarave with ~8000 inhabitants.

Resorption is the active withdrawal of nutrients before leaf abscission. This mechanism represents an important strategy to maintain efficient nutrient cycling; however, resorption is poorly characterized in old‐growth tropical forests growing in nutrient‐poor soils. We investigated nutrient resorption from leaves in 39 tree species in two tropical forests on the Guiana Shield, French Guiana, to investigate whether resorption efficiencies varied with soil nutrient, seasonality, and species traits. The stocks of P in leaves, litter, and soil were low at both sites, indicating potential P limitation of the forests. Accordingly, mean resorption efficiencies were higher for P (35.9%) and potassium (K; 44.6%) than for nitrogen (N; 10.3%). K resorption was higher in the wet (70.2%) than in the dry (41.7%) season. P resorption increased slightly with decreasing total soil P; and N and P resorptions were positively related to their foliar concentrations. We conclude that nutrient resorption is a key plant nutrition strategy in these old‐growth tropical forests, that trees with high foliar nutrient concentration reabsorb more nutrient, and that nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level., Resorption is a key plant nutrition strategy in old‐growth tropical forests. Trees with high foliar nutrient concentration reabsorb more nutrients. Nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level.

Rubber trees (Hevea brasiliensis) are the main source of natural rubber, extracted from latex, which exudes from the trunk after tapping. Tapped trees require large amounts of carbon (C) to regenerate the latex after its collection. Knowing the contribution of C sources involved in latex biosynthesis will help in understanding how rubber trees face this additional C demand. Whole crown 13CO2 pulse labelling was performed on 4-year-old rubber trees in June, when latex production was low, and in October, when it was high. 13C content was quantified in the foliage, phloem sap, wood, and latex. In both labelling periods, 13C was recovered in latex just after labelling, indicating that part of the carbohydrate was directly allocated to latex. However, significant amounts of 13C were still recovered in latex after 100 d and the peak was reached significantly later than in phloem sap, demonstrating the contribution of a reserve pool as a source of latex C. The contribution of new photosynthates to latex regeneration was faster and higher when latex metabolism was well established, in October, than in June. An improved understanding of C dynamics and the source–sink relationship in rubber tree is crucial to adapt tapping system practices and ensure sustainable latex production.

International audience; South Africa is a large country of approximately 1.22 million km(2), made up of nine provinces with three climatic zones. Farming in the country is mostly defined by regional differences. Of the different organisms isolated from milk samples of dairy cows, Staphylococcus aureus poses a challenge to maintain udder health and wholesome dairy products for human consumption. Antibiotic resistant bacteria are therefore a potential health hazard. The objective of this study was to investigate the seasonal and regional relationships of antibiotic resistance of S. aureus, of which little is known. This study was undertaken to evaluate a data set of 3410 S. aureus isolates, taken from milk samples with a somatic cell count of > 400 000 cells/mL from commercial dairy herds. These isolates were tested for antimicrobial susceptibility using the Kirby Bauer method for ampicillin, cloxacillin, penicillin G, clindamycin, oxy-tetracycline, cephalexin, cefuroxime and tylosin. The samples were from 830 dairy herds, out of the estimated 2000 commercial dairy herds in South Africa. All the antibiotics tested, except for cephalosporins, showed a predicted prevalence of resistance of above 50% in most provinces, which is a concern. The lowest prevalence of resistance to the majority of the categories of antibiotics tested was present in KwaZulu-Natal during spring. The cephalosporins had the lowest levels of prevalence of bacterial resistance in Gauteng during winter. Resistance patterns of S. aureus to the eight antibiotics varied in the different seasons and provinces, possibly because of different weather conditions, and the action and spectrum of antibiotics.

International audience; Environmental conditions are known to influence corals and their associated communities of microorganisms. However, our insights into the impacts of seasonal changes in ultraviolet radiation (UVR) on both coral physiology and microbiome remain very limited. To address this challenge, we maintained the coral Acropora muricata shaded from UVR or under ambient UVR levels during two contrasting seasons, i.e. summer and winter, and assessed the impact of UVR on the coral holobiont at each season. To this end, we analyzed the physiology (e.g., calcification, protein content, photosynthesis-related parameters) and coral microbiota composition, as well as the abundance and composition of the microbial communities and organic matter contents of the surrounding seawater. Our results show major seasonal effects on coral phenotype: (1) a lower host biomass and photosynthesizing, but fast calcifying phenotype in summer, and (2) a higher host biomass and photosynthesizing, but slow calcifying phenotype in winter. UVR had only a significant impact on Symbiodinium functioning. Specifically, high UVR levels reduced photosynthesis efficiency in summer, but an increase in chlorophyll a content may have compensated for this effect. The coral microbiota, which was variable but generally dominated by Endozoicomonas, was not affected by UVR, but its composition differed between seasons. In contrast, UVR had a major, but differential impact on the seawater microbial communities at both seasons. Particularly in summer, bacteria from the Alteromonadaceae were significantly more abundant (15-fold; up to 75%) in seawater under ambient UVR levels. Overall, our study suggests that UVR has only a limited impact on coral holobiont composition and functioning, despite major fluctuations in the surrounding seawater microbiome; seasonal changes in the holobiont are thus mostly driven by other environmental factors.

Dans l’ouest du Burkina Faso, des laiteries se heurtent à un problème d’approvisionnement en lait local, car la production est faible, saisonnée, atomisée et coûteuse à collecter. Cette étude a eu pour objectif d’identifier des leviers pour augmenter la production et réduire la saisonnalité. Elle a été réalisée chez 18 polyculteurs-éleveurs de la région des Hauts-Bassins impliqués dans la production de lait. Une analyse multivariée basée sur des variables de structures, de fonctionnement et de performance des exploitations a permis d’identifier cinq types de polyculteurs-éleveurs impliqués dans cette production : « les allaitants » à faible niveau d’intrants et à orientation pastorale à grands effectifs de vaches (T1), à effectifs moyens (T2) ; les allaitants à orientation agropastorale (T3) ; les laitiers spécialisés et à visée commerciale ayant peu recours aux fourrages verts (T4), ou à forte utilisation de fourrage vert (T5). Les types T1 et T2 se caractérisaient par une alimentation quasi exclusive au pâturage en toute saison, et un niveau de production de lait inférieur à deux litres par vache par jour au pic de lactation. Le lait issu de ces exploitations était faiblement commercialisé et rarement vendu aux laiteries. Les types T3 ont davantage eu recours aux fourrages secs et aux aliments, ce qui leur a permis d’améliorer leur production de lait commercialisée fréquemment en laiterie (env. 2 L/vache/jour au pic de lactation). Les types T4 et T5 se caractérisaient par un recours à des races améliorées, et une utilisation importante de fourrages et d’aliments achetés toute l’année, leur assurant une production de lait plus élevée (5–13 L/vache/jour au pic de lactation). Ces exploitations vendaient leur lait en totalité à la laiterie. Nos résultats soulignent que la production était fortement pénalisée par une alimentation trop pauvre en aliments et en fourrages de qualité, et que la saisonnalité des mises bas aggravait la chute de production en fin de saison sèche.

Made available in DSpace on 2018-12-11T17:17:46Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-03-01 Key message: Inter-specific interactions with eucalypts in mixed plantations increased N2fixation rate of acacia trees compared to monocultures. N2fixation was higher during the wet summer than during the dry winter both in acacia monocultures and in mixed plantations. Context: Introducing N-fixing trees in fast-growing tropical plantations may contribute to reducing the long-term requirements of N fertilizers. Management practices established in forest monocultures should be revisited in mixed-species plantations. Aims: This field experiment aimed to compare N2 fixation rates of Acacia mangium Wild in monospecific stands and in mixed-species stands with Eucalyptus grandis W. Hill ex Maiden. A secondary objective was to gain insight into the seasonal variations of N2 fixation. Methods: 15N was applied to acacia and eucalypt monocultures and mixed-species with a 1:1 ratio at mid rotation. Leaves were collected in autumn, winter, spring, and summer to determine the foliar N concentrations and 15N atom fraction. The N content in the above-ground biomass was estimated as well as the percentage of N derived from atmospheric N2 (%Ndfa) using eucalypts in monoculture as reference plants. Results: %Ndfa values averaged over the year were 14% in monoculture and 44% in mixed-species stands. While the stocking density of acacia trees was twice as high in monoculture as in mixture, the amounts of N fixed in above-ground biomass of acacia trees were close (35–39 kg N ha−1) at 39 months after planting. %Ndfa values were higher during the wet summer than the dry winter both in acacia monocultures and in mixed plantations. Conclusion: The stocking density of acacia trees can be reduced in mixed plantations with eucalypts in comparison to acacia monocultures with a low influence on the input of N to soil through biological fixation. USP ESALQ Departamento de Ciências Florestais, Av. Pádua Dias, 11, Piracicaba UFES Departamento de Ciências Florestais e da Madeira, Av. Governador Carlos Lindemberg, 316, Jerônimo Monteiro Eco&Sols INRA CIRAD IRD Montpellier SupAgro University of Montpellier USP CENA Divisão de Desenvolvimento de Técnicas Analíticas e Nucleares, Av. Centenário, 303, Piracicaba Embrapa Solos, Rua Jardim Botânico, 1024 UNESP Departamento de Solos e Recursos Ambientais, Rua José Barbosa de Barros, 1780, Botucatu UNESP Departamento de Solos e Recursos Ambientais, Rua José Barbosa de Barros, 1780, Botucatu

Leucocytes are typically considered as a whole in studies examining telomere dynamics in mammals. Such an approach may be precarious, as leucocytes represent the only nucleated blood cells in mammals, their composition varies temporally, and telomere length differs between leucocyte types. To highlight this limitation, we examined here whether seasonal variation in leucocyte composition was related to variation in telomere length in free‐ranging mandrills (Mandrilllus sphinx). We found that the leucocyte profile of mandrills varied seasonally, with lower lymphocyte proportion being observed during the long dry season presumably because of the combined effects of high nematode infection and stress at that time of the year. Interestingly, this low lymphocyte proportion during the long dry season was associated with shorter telomeres. Accordingly, based on longitudinal data, we found that seasonal changes in lymphocyte proportion were reflected by corresponding seasonal variation in telomere length. Overall, these results suggest that variation in lymphocyte proportion in blood can significantly affect telomere measurements in mammals. However, lymphocyte proportion did not entirely explain variation in telomere length. For instance, a lower lymphocyte proportion with age could not fully explain shorter telomeres in older individuals. Overall, our results show that telomere length and leucocyte profile are strongly although imperfectly intertwined, which may obscure the relationship between telomere dynamics and ageing processes in mammals.

Simulation of enteric methane emissions from individual beef cattle in tropical pastures of improving quality: a case study with the model RUMINANT

Living organisms show seasonality in a wide array of functions such as reproduction, fattening, hibernation and migration. At temperate latitudes, changes in photoperiod maintain the alignment of annual rhythms with predictable changes in the environment. The appropriate physiological response to changing photoperiod in mammals requires retinal detection of light and pineal secretion of melatonin, but extraretinal detection of light occurs in birds. A common mechanism across all vertebrates is that these photoperiod-regulated systems alter hypothalamic thyroid hormone conversion. Here we review the evidence that a circadian clock within the pars tuberalis of the adenohypophysis links photoperiod decoding to local changes of thyroid hormone signalling within the medio-basal hypothalamus through a conserved thyrotropin/deiodinase axis. We also focus on recent findings which indicate that, beyond the photoperiodic control of its conversion, thyroid hormone might also be involved in longer term timing processes of seasonal programs. Finally, we examine the potential implication of kisspeptin and RFRP3, two RF-amide peptides expressed within the medio-basal hypothalamus, in seasonal rhythmicity.

Photoperiodic treatments and reproduction in farm animals. Farm animal productions are frequently tied to the seasons, which explain the seasonal variations in availability of fresh animal products (meat, milk, cheese and eggs). Among farmed species, fishes and birds are generally considered as more directly sensitive to external factors (mainly temperature in fish and photoperiod in birds). Artificial photoperiodic treatments are widely used in numerous species including mammals ; they consist in providing extra-light during natural short days (chickens, turkeys, guinea fowl, sheep and goats), or in the administration of melatonin during long days (goats, sheep). These measures help adjust the breeding season to the requirements of the breeder and/ or cancel completely seasonal variations of sperm production in semen production centres (mammals) as well as in poultry and fish farms. Additionally, pure light treatments (without melatonin), especially when there is outside access, are non invasive and preserve the animals’ integrity and welfare., Les productions issues d’animaux d’élevage sont fréquemment rythmées sur les saisons, avec pour conséquence une disponibilité saisonnière en produits frais sur les marchés (viandes, lait et fromages, oeufs). Parmi les espèces d’intérêt en production animale, les poissons et les oiseaux sont généralement considérés comme plus directement sensibles aux facteurs externes, essentiellement les variations de la température pour les poissons et de la durée de la phase claire du jour, ou photopériode, pour les oiseaux. Chez de nombreuses espèces incluant des mammifères, nous utilisons largement des traitements photopériodiques artificiels qui consistent en un éclairement supplémentaire pendant les jours courts naturels (chez le poulet, la dinde, la pintade, le mouton et la chèvre) ou en l’administration de mélatonine pendant les jours longs (chez le mouton et la chèvre) ; ils permettent d’ajuster la période de reproduction aux souhaits de l’éleveur et/ ou d’abolir complètement les variations saisonnières de la production spermatique dans les centres producteurs de semence destinée à l’insémination artificielle (mammifères), et dans les élevages (volailles, poissons). Par ailleurs, des traitements photopériodiques «purs» (sans mélatonine), en particulier lorsqu’ils sont appliqués en bâtiments ouverts, sont non invasifs et donc respectent l’intégrité et le bien-être des animaux., Chemineau Philippe, Malpaux Benoît, Brillard Jean-Pierre, Fostier Alexis. Traitements photopériodiques et reproduction chez les animaux d'élevage. In: Bulletin de l'Académie Vétérinaire de France tome 163 n°1, 2010. pp. 19-26.

The production of aboveground soft tissue represents an important share of total net primary production in tropical rain forests. Here we draw from a large number of published and unpublished datasets (n=81 sites) to assess the determinants of litterfall variation across South American tropical forests. We show that across old-growth tropical rainforests, litterfall averages 8.61±1.91 Mg ha−1 yr−1 (mean ± standard deviation, in dry mass units). Secondary forests have a lower annual litterfall than old-growth tropical forests with a mean of 8.01±3.41 Mg ha−1 yr−1. Annual litterfall shows no significant variation with total annual rainfall, either globally or within forest types. It does not vary consistently with soil type, except in the poorest soils (white sand soils), where litterfall is significantly lower than in other soil types (5.42±1.91 Mg ha−1 yr−1). We also study the determinants of litterfall seasonality, and find that it does not depend on annual rainfall or on soil type. However, litterfall seasonality is significantly positively correlated with rainfall seasonality. Finally, we assess how much carbon is stored in reproductive organs relative to photosynthetic organs. Mean leaf fall is 5.74±1.83 Mg ha−1 yr−1 (71% of total litterfall). Mean allocation into reproductive organs is 0.69±0.40 Mg ha−1 yr−1 (9% of total litterfall). The investment into reproductive organs divided by leaf litterfall increases with soil fertility, suggesting that on poor soils, the allocation to photosynthetic organs is prioritized over that to reproduction. Finally, we discuss the ecological and biogeochemical implications of these results.

International audience; This work was designed to determine whether melatonin treatment at the spring equinox can induce reproductive activity in goats without separation from males (separation being the normal practice in Spanish farming systems) and whether this treatment modifies the onset of the natural breeding season. Twenty-nine entire does were distributed into two groups (Group M, n = 14; Group C, n = 15). A third group of ovariectomized, estradiol-treated goats (OVX group, n = 5) was used to study the effect of melatonin on reproductive activity. On March 18, Groups M and OVX received a subcutaneous melatonin implant. In entire females, estrus was tested daily using entire aproned males, and ovulation rate was assessed after identification of estrus. Plasma progesterone in entire goats, plasma luteinizing hormone (LH) in the OVX group, and live weight and body condition score for all animals were recorded once a week. In entire goats, a clear treatment by time interaction was observed for progesterone concentrations (P < 0.001), with a period of high progesterone concentrations during the natural seasonal anestrus in Group M. A similar period of high LH concentrations was observed in the OVX group. Whereas all females of Group M presented ovarian activity during this period, no female of Group C did. The resumption of the natural breeding season was retarded in Group M in comparison with that in Group C (P < 0.05). We can conclude that in Mediterranean goats, melatonin implants can induce reproductive activity without separation from males, and it causes a small retardation in the reactivation of reproductive activity in the natural breeding season. (C) 2009 Elsevier Inc. All rights reserved.

At least 18 taxa and "categories " of remains, mainly carbonised, were identified in the analysis of the non-wood plant macro-remains from the multi-phase Epipalaeolithic site of Öküzini (16560 ±180 uncal BP [18200-17400 cal ВС] to 12130 ±100 uncal BP [14400-11800 cal ВС]) and Karain В (ca 15000 uncal BP). The importance of plants in the diet and their role in determining patterns of mobility have been evaluated with quantitative and qualitative data. Nuts (principally Amygdalus, wild almond), fruits (principally Pyrus, wild pear), bulbs, roots or tubers seem to have occupied a particularly important place in these societies during all Epipalaeolithic phases, at the expense of small-seeded plants. The food plants attested in these samples would have provided carbohydrates, lipids and micronutrients, complementing meat in the diet. For the most part they were predictable and easy to gather and process. The almonds, rich in fats, could represent a vital seasonal resource that justified the additional work required for their detoxification. Judging from the seasonality indices of the plants and ungulate fauna at Öküzini, the cave could have been inhabited in all seasons periodically, but particularly in spring and autumn., Au moins 18 taxa et « catégories » de restes, pour la plupart carbonisés, ont été identifiés lors des analyses des macro-restes botaniques (charbons de bois exclus) du site Epipaléolithique multi-phase de Öküzini (16560 ±180 uncal BP [18200-17400 cal ВС] à 12130 ±100 uncal BP [14400-1 1 800 cal ВС]) et Karain В (env. 15000 uncal В P). L'importance et le rôle des plantes - en particulier dans l'alimentation et pour la détermination de la mobilité - ont été évalués à l'aide de données quantitatives et qualitatives. Les noix (principalement Amygdalus, amande sauvage) , fruits (essentiellement Pyrus, poire sauvage), bulbes, racines ou rhizomes semblent avoir occupé une place particulière dans ces sociétés pendant toutes les phases de l'Epipaléolithique, au détriment des plantes à petites graines. Les plantes alimentaires attestées fournissaient des hydrates de carbone, lipides et micronutriments complétant bien l'alimentation carnée et représentaient pour la plupart des ressources prédictibles, faciles à cueillir et à préparer. Les amandes, par leur richesse en graisse, pouvaient représenter une ressource saisonnière vitale, justifiant l 'addition de travail requis pour enlever leur toxicité. Selon les indices de saisonnalité des plantes et de la faune ongulée de Öküzini, la grotte pourrait en toutes saisons avoir été occupée de façon périodique mais plus particulièrement au printemps et en automne., Martinoli Danièle. Food plant use, temporal changes and site seasonality at Epipalaeolithic Öküzini and Karain B caves, southwest Anatolia, Turkey. In: Paléorient, 2004, vol. 30, n°2. pp. 61-80.

The Middle Palaeolithic site of Abric Romani (North Eastern Spain) was selected to test the hypothesis that seasonal behaviour of Neanderthal groups will induce differences in the faunal assemblages. The site has a long stratigraphical sequence representing a short chronology, but we focused on levels K, L, and M. The study of seasonality in ungulates indicates that the game was hunted at different periods of the year in each level. Combina-tion of zooarchaeological analyses shows that in all levels the pattern of game procurement and transport to the shelter is similar. In the same way, there is no significant difference related to animal processing. The carcasses introduced into the shelter are used in an exhaustive and systematic way. Although seasonality in the occupation are changing, there are no significant differences in the activities of the Neanderthal groups in the three levels. We conclude that the presence of Neanderthals at Abric Romani is highly seasonal and their displacements are strongly conditioned by the presence of game preys in the territory. Le site pléistocène moyen de l'Abric Romani (Nord-Est de l'Espagne) a été choisi pour tester l'hypothèse qu'un comportement saisonnier des Néanderthaliens se traduit par des différences dans les associations fauniques. Le gisement recèle une longue séquence stratigraphique qui représente une courte période chronologique, mais nous comparerons les données des niveaux K, L, et M. L'étude de la saisonnalité d'occupation à partir des ongulés indique que le gibier a été chassé à différentes époques de l'année dans chaque niveau. La combinaison des analyses archéozoologiques montrent que le mode d'acquisition du gibier et de son transport au gisement est le même dans les trois niveaux. De même, il n'y a pas de différence dans le traitement des carcasses, elles sont utilisées de manière exhaustive et systématique. Même si la saison d'occupation du site varie dans les trois ensembles considérés, il n'apparaît pas de différence significative au niveau des activités des groupes humains. La présence des Néandertaliens à l'Abric Romani est saisonnière et leurs déplacements sont fortement conditionnés par la présence de gibier sur leur territoire.

International audience; BACKGROUND: Cyclic rodent population dynamics are subjected to both intrinsic regulatory processes such as density-dependence and extrinsic environmental forcing. Among extrinsic factors, seasonal environmental variation is understood to facilitate cycles. In rodents, these processes have been studied mostly independently and their relative importance for population dynamics is poorly known. RESULTS: We performed a detailed analysis of common vole (Microtus arvalis) reproduction in a cyclic population using a spatially extensive data set over 17 years in central-western France. Environmental seasonality was the main source of explained variation in common vole reproduction. Additionally, inter-annual variation in the environment explained a smaller part of the variance in reproduction in spring and summer than in winter, whereas the effect of density was only found in autumn and winter. In particular, we detected a strong impact of plant productivity on fecundity during the breeding season, with low vegetation productivity being able to bring vole reproduction nearly to a halt. In contrast, vole reproduction during autumn and winter was mainly shaped by intrinsic factors, with only the longer and heavier females being able to reproduce. The effect of population density on reproduction was negative, mediated by direct negative effects on the proportion of breeders in autumn and winter during outbreak years and by a delayed negative effect on litter size the following year. CONCLUSIONS: During the main breeding season, variability of female vole reproduction is predominantly shaped by food resources, suggesting that only highly productive environment may induce vole outbreaks. During fall and winter, variability of female vole reproduction is mainly controlled by intrinsic factors, with high population density suppressing reproduction. This suggests, in this cyclic population, that negative direct density dependence on reproduction could explain winter declines after outbreaks.