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AbstractAimFuture climate change threatens marine forests across the world, potentially disrupting ecosystem function and services. Nonetheless, the direction and intensity of climate‐induced changes in kelp forest biodiversity remain unknown, precluding well‐informed conservation and management practices.LocationGlobal.MethodsWe use machine‐learning models to forecast global changes in species richness and community composition of 105 kelp forest species under contrasting Shared Socioeconomic Pathway (SSP) scenarios of climate change (decade 2090–2100): one aligned with the Paris Agreement and another of substantially higher emissions.ResultsA poleward and depth shift in species distributions is forecasted, translating into ~15% less area in the extent of the global biome, coupled with marked regional biodiversity changes. Community composition changes are mostly projected in the Arctic, the Northern Pacific and Atlantic, and Australasia, owing to poleward range expansions and wide low latitude losses.Main ConclusionsBy surpassing the Paris Agreement expectations, species reshuffling may simplify and impair ecosystem services in numerous temperate regions of Australasia, Southern Africa, Southern America and the Northern Atlantic, and in the tropical Pacific, where complete species losses were projected without replacement. These estimates, flagging threatened regions and species, as well as refugial areas of population persistence, can now inform conservation, management and restoration practices considering future climate change.

Climate change and fragmentation are major threats to world forests. Understanding how functional traits related to drought tolerance change across small-scale, pronounced moisture gradients in fragmented forests is important to predict species' responses to these threats. In the case of Aextoxicon punctatum, a dominant canopy tree in fog-dependent rain forest patches in semiarid Chile, we explored how the magnitude, variability and correlation patterns of leaf and xylem vessel traits and hydraulic conductivity varied across soil moisture (SM) gradients established within and among forest patches of different size, which are associated with differences in tree establishment and mortality patterns. Leaf traits varied across soil-moisture gradients produced by fog interception. Trees growing at drier leeward edges showed higher leaf mass per area, trichome and stomatal density than trees from the wetter core and windward zones. In contrast, xylem vessel traits (vessels diameter and density) did not vary producing loss of hydraulic conductivity at drier leeward edges. We also detected higher levels of phenotypic integration and variability at leeward edges. The ability of A. punctatum to modify leaf traits in response to differences in SM availability established over short distances (<500 m) facilitates its persistence in contrasting microhabitats within forest patches. However, xylem anatomy showed limited plasticity, which increases cavitation risk at leeward edges. Greater patch fragmentation, together with fluctuations in irradiance and SM in small patches, could result in higher risk of drought-related tree mortality, with profound impacts on hydrological balances at the ecosystem scale.

Fire danger indices are descriptors of fire potential in a large area, and combine a few variables that affect the initiation, spread and control of forest fires. The Canadian Fire Weather Index (FWI) is one of the most widely used fire danger indices in the world, and it is built upon instantaneous values of temperature, relative humidity and wind velocity at noon, together with 24 hourly accumulated precipitation. However, the scarcity of appropriate data has motivated the use of daily mean values as surrogates of the instantaneous ones in several studies that aimed to assess the impact of global warming on fire. In this paper we test the sensitivity of FWI values to both instantaneous and daily mean values, analyzing their effect on mean seasonal fire danger (seasonal severity rating, SSR) and extreme fire danger conditions (90th percentile, FWI90, and FWI>30, FOT30), with a special focus on its influence in climate change impact studies. To this aim, we analyzed reanalysis and regional climate model (RCM) simulations, and compared the resulting instantaneous and daily mean versions both in the present climate and in a future scenario. In particular, we were interested in determining the effect of these datasets on the projected changes obtained for the mean and extreme seasonal fire danger conditions in future climate scenarios, as given by a RCM. Overall, our results warn against the use of daily mean data for the computation of present and future fire danger conditions. Daily mean data lead to systematic negative biases of fire danger calculations. Although the mean seasonal fire danger indices might be corrected to compensate for this bias, fire danger extremes (FWI90 and specially FOT30) cannot be reliably transformed to accommodate the spatial pattern and magnitude of their respective instantaneous versions, leading to inconsistent results when projected into the future. As a result, we advocate caution when using daily mean data and strongly recommend the application of the standard definition for its calculation as closely as possible. Threshold-dependent indices derived from FWI are not reliably represented by the daily mean version and thus can neither be applied for the estimation of future fire danger season length and severity, nor for the estimation of future extreme events. The research leading to these results has received funding from the European Union's Seventh Framework Programme (FP7/2007-2013) under grant agreement 243888 (FUME Project). J.F. acknowledges nancial support from the Spanish R&D&I programme through grant CGL2010-22158-C02 (CORWES project). The ESCENA project (200800050084265) of the Spanish \Strategic action on energy and climate change" provided the WRF RCM simulation used in this study. We acknowledge three anonymous referees for their useful comments that helped to improve the original manuscript.

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.

This paper analyzes the role of natural geography for explaining local population change patterns. Using spatially detailed data for Spain from 1960 to 2011, the estimation results indicated that natural geography variables relate to about half of the population growth variation of rural areas and more than a third of the population growth variation of urban areas during this period. Local differences in climate, topography, and soil and rock formation as well as distance to aquifers and the coast contribute to variations in local population growth patterns. Although, over time, local population change became less related to differences in natural geography, natural geography is still significantly related to nearly a third of the variation in local population change in rural areas and the contribution of temperature range and precipitation seasonality has even increased. For urban areas, weather continues to matter too, with growth being higher in warmer places.

[EN] Short-legged, small, robust frogs of the family Craugastoridae present a remarkable beta-diversity in the high Andes, their distributions being characterized by a very high degree of micro-endemism to specific valleys. We used dataloggers to study the temperature and humidity conditions of microhabitats of several species of the genus Microkayla at three elevation belts: Below, within, and above the altitudinal range of their distribution in Bolivia. We also conducted thermal physiology experiments on a limited number of individuals of one of these species. Our aim was to infer on factors that may limit the distribution of anurans in a biological hotspot that is threatened by climate warming. We found an unexpected thermal heterogeneity within the slopes at three different Andean valleys that explained the specific distribution of species of Microkayla at each site. Species distribution was associated to elevation belts with the highest ambient relative humidity, and there was high variability in thermal preference when individuals were experimentally exposed to a thermal gradient. Critical thermal maxima compared to the temperatures that frogs confront in nature, as well as thermal performance trials, revealed that the studied species has a broad physiological tolerance to temperature. These results point to moisture, and not temperature, as the limiting climatic factor determining the occurrence of these species in high Andean slopes, but further experimental work on water balance is needed. The predicted desertification of the Andes in future climate change scenarios poses a potentially serious threat to this highly diverse group of amphibians. [ES] Las pequeñas ranas robustas y de patas cortas de la familia Craugastoridae presentan una alta diversidad beta en la región altoandina, donde la distribución de las distintas especies se caracteriza por un alto grado de endemismo, restringiéndose a valles concretos. Utilizamos “dataloggers” para estudiar las condiciones de temperatura y humedad en los microhábitats de algunas especies de Microkayla en tres franjas a distinta elevación: por debajo de su rango altitudinal de distribución, dentro de dicho rango, y por encima. Además, realizamos experimentos de fisiología térmica con un limitado número de ejemplares de una especie de Microkayla. Nuestro objetivo era averiguar los factores que pueden limitar la distribución de los anuros en un punto caliente de biodiversidad amenazado por el calentamiento climático. Encontramos una sorprendente heterogeneidad térmica en las laderas de tres valles andinos diferentes, que explican la distribución de las especies de Microkayla en cada sitio. La distribución de las especies está asociada a las franjas altitudinales de humedad ambiental más alta, y se observa una alta variabilidad en las preferencias térmicas cuando los individuos son sometidos experimentalmente a gradientes de temperatura. Las temperaturas críticas máximas, comparadas con las temperaturas que las ranas confrontan en la naturaleza, así como los experimentos de desempeño térmico realizados, revelan que la especie estudiada tiene una amplia tolerancia térmica. Estos resultados apuntan a la humedad, y no la temperatura, como el factor climático limitante que determina la existencia de estas especies en las laderas altoandinas, aunque se necesita más trabajo experimental en balance hídrico para comprobar esto. La previsible desertificación de los Andes bajo escenarios de cambio climático futuros, supone por tanto una seria amenaza potencial para este grupo tan diverso de anfibios. This research was supported by Project CG2014-56160-P of the Spanish Government.