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Water use efficiency (WUE) is a quantitative measurement which improvement is a major issue in the context of global warming and restrictions in water availability for agriculture. In this study, we aimed at studying the variation and genetic control of WUE and the respective role of its components (plant biomass and transpiration) in a perennial fruit crop. We explored an INRA apple core collection grown in a phenotyping platform to screen one-year-old scions for their accumulated biomass, transpiration and WUE under optimal growing conditions. Plant biomass was decompose into morphological components related to either growth or organ expansion. For each trait, nine mixed models were evaluated to account for the genetic effect and spatial heterogeneity inside the platform. The Best Linear Unbiased Predictors of genetic values were estimated after model selection. Mean broad-sense heritabilities were calculated from variance estimates. Heritability values indicated that biomass (0.76) and WUE (0.73) were under genetic control. This genetic control was lower in plant transpiration with an heritability of 0.54. Across the collection, biomass accounted for 70% of the WUE variability. A Hierarchical Ascendant Classification of the core collection indicated the existence of six groups of genotypes with contrasting morphology and WUE. Differences between morphotypes were interpreted as resulting from differences in the main processes responsible for plant growth: cell division leading to the generation of new organs and cell elongation leading to organ dimension. Although further studies will be necessary on mature trees with more complex architecture and multiple sinks such as fruits, this study is a first step for improving apple plant material for the use of water.

Large-scale climate processes influence many aspects of ecology including breeding phenology, reproductive success and survival across a wide range of taxa. Some effects are direct, for example, in temperate-zone birds, ambient temperature is an important cue enabling breeding effort to coincide with maximum food availability, and earlier breeding in response to warmer springs has been documented in many species. In other cases, time-lags of up to several years in ecological responses have been reported, with effects mediated through biotic mechanisms such as growth rates or abundance of food supplies. Here we use 23 years of data for a temperate woodland bird species, the great tit (Parus major), breeding in deciduous woodland in eastern England to demonstrate a time-lagged linear relationship between the on-set of egg laying and the winter index of the North Atlantic Oscillation such that timing can be predicted from the winter index for the previous year. Thus the timing of bird breeding (and, by inference, the timing of spring events in general) can be predicted one year in advance. We also show that the relationship with the winter index appears to arise through an abiotic time-lag with local spring warmth in our study area. Examining this link between local conditions and larger-scale processes in the longer-term showed that, in the past, significant relationships with the immediately preceding winter index were more common than those with the time-lagged index, and especially so from the late 1930s to the early 1970s. However, from the mid 1970s onwards, the time-lagged relationship has become the most significant, suggesting a recent change in climate patterns. The strength of the current time-lagged relationship suggests that it might have relevance for other temperature-dependent ecological relationships.

The earth is warming at an alarming rate, especially in the Arctic, where a marked decline in sea ice cover may have far-ranging consequences for endemic species. Little auks, endemic Arctic seabirds, are key bioindicators as they forage in the marginal ice zone and feed preferentially on lipid-rich Arctic copepods and ice-associated amphipods sensitive to the consequences of global warming. We tested how little auks cope with an ice-free foraging environment during the breeding season. To this end, we took advantage of natural variation in sea ice concentration along the east coast of Greenland. We compared foraging and diving behaviour, chick diet and growth and adult body condition between two years, in the presence versus nearby absence of sea ice in the vicinity of their breeding site. Moreover, we sampled zooplankton at sea when sea ice was absent to evaluate prey location and little auk dietary preferences. Little auks foraged in the same areas both years, irrespective of sea ice presence/concentration, and targeted the shelf break and the continental shelf. We confirmed that breeding little auks showed a clear preference for larger copepod species to feed their chick, but caught smaller copepods and nearly no ice-associated amphipod when sea ice was absent. Nevertheless, these dietary changes had no impact on chick growth and adult body condition. Our findings demonstrate the importance of bathymetry for profitable little auk foraging, whatever the sea-ice conditions. Our investigations, along with recent studies, also confirm more flexibility than previously predicted for this key species in a warming Arctic.

Coastal systems are increasingly threatened by multiple local anthropogenic and global climatic stressors. With the difficulties in remediating global stressors, management requires alternative approaches that focus on local scales. We used manipulative experiments to test whether reducing local stressors (sediment load and nutrient concentrations) can improve the resilience of foundation species (canopy algae along temperate rocky coastlines) to future projected global climate stressors (high wave exposure, increasing sea surface temperature), which are less amenable to management actions. We focused on Fucoids (Cystoseira barbata) along the north-western Adriatic coast in the Mediterranean Sea because of their ecological relevance, sensitivity to a variety of human impacts, and declared conservation priority. At current levels of sediment and nutrients, C. barbata showed negative responses to the simulated future scenarios of high wave exposure and increased sea surface temperature. However, reducing the sediment load increased the survival of C. barbata recruits by 90.24% at high wave exposure while reducing nutrient concentrations resulted in a 20.14% increase in the survival and enhanced the growth of recruited juveniles at high temperature. We conclude that improving water quality by reducing nutrient concentrations, and particularly the sediment load, would significantly increase the resilience of C. barbata populations to projected increases in climate stressors. Developing and applying appropriate targets for specific local anthropogenic stressors could be an effective management action to halt the severe and ongoing loss of key marine habitats.

The response of trees to a changing climate can be affected by transgenerational phenotypic plasticity, i.e. phenotypic variation that is conserved and transferred to the offspring. Transgenerational plasticity that is influenced by epigenetics (heritable changes in gene function that do not result from changes in DNA sequence) during both sexual and asexual reproduction are of major relevance for adaptation of plants to climate change. To understand the transgenerational effects on the responses of vegetatively propagated poplar (Populus deltoides and P. trichocarpa) ramets (cuttings) to a changing environment, we tested whether the temperature and photoperiod experienced by the mother trees (genets) persistently affects the phenology of the cuttings grown in a common environment. We weekly monitored the bud phenology of the cuttings collected from the parent trees that have been growing across Europe along a >2100 km latitudinal gradient for at least 18 years. In addition, we asked whether there was variation in DNA methylation as measured by Methylation Sensitive Amplified Fragment Length Polymorphism (MSAPs) in the clones due to the different environmental conditions experienced by the parent trees. Our results indicate a transgenerational effect on bud phenology in the asexually reproduced offspring (vegetative cuttings). The temperatures experienced by the parent tree clones (from different geographic regions) altered the bud flush of the cuttings in the common garden. However, no significant epigenetic variation was detected in the cuttings of the parent trees within single genotypes growing under different climates. In sum, our results show that trees have the potential to respond to rapid climate change but the mechanism behind these changes needs to be further investigated by more powerful molecular methods like whole-genome bisulphite sequencing techniques.

Bien que l'on sache beaucoup de choses sur les facteurs qui contrôlent chaque composante du cycle terrestre de l'azote (N), il est moins clair comment ces facteurs affectent la disponibilité totale de l'azote, la somme des formes organiques et inorganiques potentiellement disponibles pour les micro-organismes et les plantes. Cela est particulièrement vrai pour les écosystèmes pauvres en N tels que les terres arides, qui sont très sensibles au changement climatique et aux processus de désertification pouvant entraîner la perte de nutriments du sol tels que N. Nous avons évalué la corrélation entre différents facteurs climatiques, abiotiques, végétaux et liés aux nutriments et la disponibilité de N dans les prairies semi-arides de Stipa tenacissima le long d'un large gradient d'aridité allant de l'Espagne à la Tunisie. L'aridité avait la relation la plus forte avec la disponibilité de l'azote, suggérant l'importance des contrôles abiotiques sur le cycle de l'azote dans les terres arides. L'aridité semble moduler les effets du pH, de la couverture végétale et du C organique (CO) sur la disponibilité de l'azote. Nos résultats suggèrent que les taux de transformation de l'azote, qui sont largement influencés par les variations de l'humidité du sol, ne sont pas les moteurs directs de la disponibilité de l'azote dans les prairies étudiées. Au contraire, la forte relation entre l'aridité et la disponibilité de l'azote pourrait être motivée par des effets indirects qui opèrent sur de longues échelles de temps (des décennies à des millénaires), y compris à la fois biotiques (par exemple, la couverture végétale) et abiotiques (par exemple, le CO et le pH du sol). Si ces facteurs sont en fait plus importants que les effets à court terme des précipitations sur les taux de transformation de l'azote, alors nous pourrions nous attendre à observer une diminution décalée de la disponibilité de l'azote en réponse à l'augmentation de l'aridité. Néanmoins, nos résultats suggèrent que l'augmentation de l'aridité prévue avec le changement climatique en cours réduira la disponibilité de l'azote dans le bassin méditerranéen, affectant l'absorption des nutriments végétaux et la production primaire nette dans les prairies semi-arides de cette région. Si bien se sabe mucho sobre los factores que controlan cada componente del ciclo del nitrógeno (N) terrestre, está menos claro cómo estos factores afectan la disponibilidad total de N, la suma de formas orgánicas e inorgánicas potencialmente disponibles para microorganismos y plantas. Esto es particularmente cierto para los ecosistemas pobres en N, como las tierras secas, que son altamente sensibles al cambio climático y los procesos de desertificación que pueden conducir a la pérdida de nutrientes del suelo, como N. Evaluamos cómo los diferentes factores climáticos, abióticos, vegetales y relacionados con los nutrientes se correlacionan con la disponibilidad de N en los pastizales semiáridos de Stipa tenacissima a lo largo de un amplio gradiente de aridez desde España hasta Túnez. La aridez tuvo la relación más fuerte con la disponibilidad de N, lo que sugiere la importancia de los controles abióticos en el ciclo de N en las tierras secas. La aridez pareció modular los efectos del pH, la cobertura vegetal y el C orgánico (OC) sobre la disponibilidad de N. Nuestros resultados sugieren que las tasas de transformación de N, que son impulsadas en gran medida por las variaciones en la humedad del suelo, no son los impulsores directos de la disponibilidad de N en los pastizales estudiados. Más bien, la fuerte relación entre la aridez y la disponibilidad de N podría ser impulsada por efectos indirectos que operan en escalas de tiempo largas (décadas a milenios), incluyendo tanto bióticos (por ejemplo, cobertura vegetal) como abióticos (por ejemplo, OC y pH del suelo). Si estos factores son de hecho más importantes que los efectos a corto plazo de la precipitación en las tasas de transformación de N, entonces podríamos esperar observar una disminución retardada en la disponibilidad de N en respuesta al aumento de la aridez. Sin embargo, nuestros resultados sugieren que el aumento de la aridez predicho con el cambio climático en curso reducirá la disponibilidad de N en la cuenca mediterránea, lo que afectará la absorción de nutrientes de las plantas y la producción primaria neta en los pastizales semiáridos en toda esta región. While much is known about the factors that control each component of the terrestrial nitrogen (N) cycle, it is less clear how these factors affect total N availability, the sum of organic and inorganic forms potentially available to microorganisms and plants. This is particularly true for N-poor ecosystems such as drylands, which are highly sensitive to climate change and desertification processes that can lead to the loss of soil nutrients such as N. We evaluated how different climatic, abiotic, plant and nutrient related factors correlate with N availability in semiarid Stipa tenacissima grasslands along a broad aridity gradient from Spain to Tunisia. Aridity had the strongest relationship with N availability, suggesting the importance of abiotic controls on the N cycle in drylands. Aridity appeared to modulate the effects of pH, plant cover and organic C (OC) on N availability. Our results suggest that N transformation rates, which are largely driven by variations in soil moisture, are not the direct drivers of N availability in the studied grasslands. Rather, the strong relationship between aridity and N availability could be driven by indirect effects that operate over long time scales (decades to millennia), including both biotic (e.g. plant cover) and abiotic (e.g. soil OC and pH). If these factors are in fact more important than short-term effects of precipitation on N transformation rates, then we might expect to observe a lagged decrease in N availability in response to increasing aridity. Nevertheless, our results suggest that the increase in aridity predicted with ongoing climate change will reduce N availability in the Mediterranean basin, impacting plant nutrient uptake and net primary production in semiarid grasslands throughout this region. في حين أن الكثير معروف عن العوامل التي تتحكم في كل مكون من مكونات دورة النيتروجين الأرضية (N)، إلا أنه من غير الواضح كيف تؤثر هذه العوامل على إجمالي توافر N، وهو مجموع الأشكال العضوية وغير العضوية التي يحتمل أن تكون متاحة للكائنات الحية الدقيقة والنباتات. وينطبق هذا بشكل خاص على النظم الإيكولوجية التي تعاني من فقر النيتروجين مثل الأراضي الجافة، وهي حساسة للغاية لتغير المناخ وعمليات التصحر التي يمكن أن تؤدي إلى فقدان مغذيات التربة مثل النيتروجين. قمنا بتقييم كيفية ارتباط العوامل المناخية واللاأحيائية والنباتية والمغذيات المختلفة بتوافر النيتروجين في المراعي شبه القاحلة على طول تدرج جفاف واسع من إسبانيا إلى تونس. كان للجفاف أقوى علاقة بتوافر النيتروجين، مما يشير إلى أهمية الضوابط اللاأحيائية في دورة النيتروجين في الأراضي الجافة. يبدو أن الجفاف يعدل تأثيرات الأس الهيدروجيني والغطاء النباتي و C العضوي (OC) على توافر N. تشير نتائجنا إلى أن معدلات تحول N، التي تحركها إلى حد كبير الاختلافات في رطوبة التربة، ليست هي الدوافع المباشرة لتوافر N في الأراضي العشبية المدروسة. بدلاً من ذلك، يمكن أن تكون العلاقة القوية بين الجفاف وتوافر N مدفوعة بالتأثيرات غير المباشرة التي تعمل على نطاقات زمنية طويلة (من عقود إلى آلاف السنين)، بما في ذلك كل من الحيوية (مثل الغطاء النباتي) واللاأحيائية (مثل OC التربة ودرجة الحموضة). إذا كانت هذه العوامل في الواقع أكثر أهمية من الآثار قصيرة الأجل لهطول الأمطار على معدلات تحول N، فقد نتوقع ملاحظة انخفاض متأخر في توافر N استجابة لزيادة الجفاف. ومع ذلك، تشير نتائجنا إلى أن الزيادة في القحولة المتوقعة مع تغير المناخ المستمر ستقلل من توافر N في حوض البحر الأبيض المتوسط، مما يؤثر على امتصاص المغذيات النباتية وصافي الإنتاج الأولي في المراعي شبه القاحلة في جميع أنحاء هذه المنطقة.