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The thermal balance of forests is the result of complex land–atmosphere interactions. Different climate regimes and plant functional types can have contrasting energy budgets, but little is known about the influence of forest structure and functional traits. Here, we combined spaceborne measurements of surface temperature from ECOSTRESS with ground‐based meteorological data to estimate the thermal balance at the surface (∆Tcan−air) during four summers (2018–2021), at the Mediterranean–temperate ecotone in the NE Iberian Peninsula. We analyzed the spatiotemporal drivers of ∆Tcan−air by quantifying the effects of meteorology, forest structure (stand density, tree height) and ecophysiology (hydraulic traits), during normal days and hot spells. Canopy temperatures (Tcan) fluctuated according to changes in air temperature (Tair) but were on average 4.2 K warmer. During hot spells, ∆Tcan−air was smaller than during normal periods. We attribute this decrease to the advection of hot and dry air masses from the Saharan region resulting in a sudden increase in Tair relative to Tcan. Vapor pressure deficit (VPD) was negatively correlated with ∆Tcan−air, since the highest VPD values coincided with peaks in heat advection. Nonetheless, Tcan increased with VPD due to decreased transpiration (following stomatal closure), even though sufficient soil water availability enabled some degree of evaporative cooling. Our findings demonstrate that plot‐scale forest structural and hydraulic traits are key determinants for the forest thermal balance. The integration of functional traits and forest structure over relevant spatial scales would improve our ability to understand and model land–atmosphere feedbacks in forested regions. Plain Language Summary: Forests exchange energy with the atmosphere. Different types of forests may result in substantially different energy exchanges, but it is not clear which are the ecological factors causing these differences. This is relevant because during hot spells, the way by which the surface dissipates heat can either intensify or mitigate the air temperature increase. Here, we assessed how canopies exchange heat with the atmosphere depending on the characteristics of the forest cover, in a region densely covered by forests, with great ecological and climatic diversity, in the transition zone between the Mediterranean and the temperate ecotone. We show that recent hot spells were not aggravated by tree energy dissipation into the atmosphere. Instead, we argue that incoming hot air masses, often traveling from northern Africa, reduced the exchange of energy between the surface and the atmosphere, and so, the warming from below was not critical for the aggravation of these hot spells. Yet, we found that there was high variability in the thermal balance of forests along the ecoclimatic gradients of the study region that could not be explained by broad forest type classifications. Instead, differences in the thermal balance and its influence on air temperature were better explained by forests functional and structural characteristics, such as tree height or functional type of the dominant species. Key Points: The thermal balance of forests is estimated at the plot‐scale using ECOSTRESS‐derived canopy temperaturesHot spells are mostly driven by advection rather than by land–atmosphere feedbacksForest structure and species‐specific differences in plant water use correlate with heat dissipation mechanisms [ABSTRACT FROM AUTHOR]

Global warming is raising concerns about the acclimatory capacity of trees and forests, especially in Mediterranean-type ecosystems. The sensitivity of photosynthesis to temperature is a key uncertainty for projecting the magnitude of terrestrial feedbacks on future climate change. While boreal, temperate and tropical species have been comparatively well investigated, our study provides the first comprehensive overview of the seasonal acclimatory responses of photosynthesis and its component processes to temperature in four Mediterranean climax species under natural conditions. We quantified seasonal changes in the responses of net photosynthesis (A net), stomatal conductance (g s), mesophyllic conductance (g m) and electron-transport rate (J cf), and investigated their sensitivity to drought and temperature stress in sunlit and shaded leaves of four Mediterranean tree species (Quercus ilex L. , Pinus halepensis Mill. , Arbutus unedo L. and Quercus pubescens Willd.). Sunlit leaves, but not shaded leaves, showed a pronounced seasonality in the temperature responses of A net, g s, g m and J cf. All four species and variables showed a remarkably dynamic and consistent acclimation of the thermal optimum (T opt), reaching peaks in summer ~29–32 °C. Changes in the shape of the response curves were, however, highly species-specific. Under severe drought, T opt of all variables were on average 22–29% lower. This was accompanied by narrower response curves above all in P. halepensis , reducing the optimal range for photosynthesis to the cooler morning or evening periods. Wider temperature-response curves and less strict stomatal control under severe drought were accompanied by wilting and drought-induced leaf shedding in Q. ilex and Q. pubescens and by additional branch dieback in A. unedo. Mild winter conditions led to a high T opt (~19.1–22.2 °C), benefitting the evergreen species, especially P. halepensis. Seasonal acclimation of A net was explained better by g s and g m being less pronounced in J cf. Drought was thus a key factor, in addition to growth temperature, to explain seasonal acclimation of photosynthesis. Severe drought periods may exceed more frequently the high acclimatory capacity of Mediterranean trees to high ambient temperatures, which could lead to reduced growth, increased leaf shedding and, for some species such as A. unedo , increased mortality risk. [ABSTRACT FROM AUTHOR]

Background: In the POISE‐2 (PeriOperative ISchemic Evaluation 2) trial, perioperative aspirin did not reduce cardiovascular events, but increased major bleeding. There remains uncertainty regarding the effect of perioperative aspirin in patients undergoing vascular surgery. The aim of this substudy was to determine whether there is a subgroup effect of initiating or continuing aspirin in patients undergoing vascular surgery. Methods: POISE‐2 was a blinded, randomized trial of patients having non‐cardiac surgery. Patients were assigned to perioperative aspirin or placebo. The primary outcome was a composite of death or myocardial infarction at 30 days. Secondary outcomes included: vascular occlusive complications (a composite of amputation and peripheral arterial thrombosis) and major or life‐threatening bleeding. Results: Of 10 010 patients in POISE‐2, 603 underwent vascular surgery, 319 in the continuation and 284 in the initiation stratum. Some 272 patients had vascular surgery for occlusive disease and 265 had aneurysm surgery. The primary outcome occurred in 13·7 per cent of patients having aneurysm repair allocated to aspirin and 9·0 per cent who had placebo (hazard ratio (HR) 1·48, 95 per cent c.i. 0·71 to 3·09). Among patients who had surgery for occlusive vascular disease, 15·8 per cent allocated to aspirin and 13·6 per cent on placebo had the primary outcome (HR 1·16, 0·62 to 2·17). There was no interaction with the primary outcome for type of surgery (P = 0·294) or aspirin stratum (P = 0·623). There was no interaction for vascular occlusive complications (P = 0·413) or bleeding (P = 0·900) for vascular compared with non‐vascular surgery. Conclusion: This study suggests that the overall POISE‐2 results apply to vascular surgery. Perioperative withdrawal of chronic aspirin therapy did not increase cardiovascular or vascular occlusive complications. Registration number: NCT01082874 (http://www.clinicaltrials.gov). No evidence to start or stop aspirin [ABSTRACT FROM AUTHOR]

Cynodon dactylon (bermudagrass) is the most important weed in sugarcane crops in Tucumán. The aim of this study was to evaluate the weed control efficacy (CE) of topramezone alone and in a tank-mix with atrazine on bermudagrass plants obtained from a single-node stem cutting, simulating the condition of the weeds after a mechanical control. The effect of different doses used in a sugarcane crop was also evaluated. Topramezone (33.6 g a.i./ha) + atrazine (0.9 kg a.i./ha) was the treatment with the best CE on bermudagrass, lower aboveground dry weight of the weed at 43 days after treatment, and absence of shoots. This treatment did not decrease crop yield when compared to the control. The efficient control of bermudagrass, as well as the absence of crop injury, permits the use of topramezone, in combination with atrazine, as a new chemical alternative for the post-emergent control for this and other weeds. [ABSTRACT FROM AUTHOR]

Terrestrial carbon exchange is a key process of the global carbon cycle consisting of a delicate balance between photosynthetic carbon uptake and respiratory release. We have, however, a limited understanding how long-term decreases in precipitation induced by climate change affect the boundaries and mechanisms of photosynthesis and respiration. We examined the seasonality of photosynthetic and respiratory traits and evaluated the adaptive mechanism of the foliar carbon balance of Quercus ilex L. experiencing a long-term rainfall-exclusion experiment. Day respiration (Rd) but not night respiration (Rn) was generally higher in the drought treatment leading to an increased Rd/Rn ratio. The limitation of mesophyll conductance (gm) on photosynthesis was generally stronger than stomatal limitation (gs) in the drought treatment, reflected in a lower gm/gs ratio. The peak photosynthetic activity in the drought treatment occurred in an atypical favourable summer in parallel with lower Rd/Rn and higher gm/gs ratios. The plant carbon balance was thus strongly improved through: (i) higher photosynthetic rates induced by gm; and (ii) decreased carbon losses mediated by Rd. Interestingly, photosynthetic potentials (Vc,max, Jmax, and TPU) were not affected by the drought treatment, suggesting a dampening effect on the biochemical level in the long term. In summary, the trees experiencing a 14-year-long drought treatment adapted through higher plasticity in photosynthetic and respiratory traits, so that eventually the atypical favourable growth period was exploited more efficiently. [ABSTRACT FROM AUTHOR]

The Mediterranean region is a hot spot of climate change vulnerable to increased droughts and heat waves. Scaling carbon fluxes from leaf to landscape levels is particularly challenging under drought conditions. We aimed to improve the mechanistic understanding of the seasonal acclimation of photosynthesis and morphology in sunlit and shaded leaves of four Mediterranean trees (Quercus ilex L., Pinus halepensis Mill., Arbutus unedo L. and Quercus pubescens Willd.) under natural conditions. Vc,max and Jmax were not constant, and mesophyll conductance was not infinite, as assumed in most terrestrial biosphere models, but varied significantly between seasons, tree species and leaf position. Favourable conditions in winter led to photosynthetic recovery and growth in the evergreens. Under moderate drought, adjustments in the photo/biochemistry and stomatal/mesophyllic diffusion behaviour effectively protected the photosynthetic machineries. Severe drought, however, induced early leaf senescence mostly in A. unedo and Q. pubescens, and significantly increased leaf mass per area in Q. ilex and P. halepensis. Shaded leaves had lower photosynthetic potentials but cushioned negative effects during stress periods. Species-specificity, seasonal variations and leaf position are key factors to explain vegetation responses to abiotic stress and hold great potential to reduce uncertainties in terrestrial biosphere models especially under drought conditions. [ABSTRACT FROM AUTHOR]

Integrated cross-sectoral impact assessments facilitate a comprehensive understanding of interdependencies and potential synergies, conflicts, and trade-offs between sectors under changing conditions. This paper presents a sensitivity analysis of a European integrated assessment model, the CLIMSAVE integrated assessment platform (IAP). The IAP incorporates important cross-sectoral linkages between six key European land- and water-based sectors: agriculture, biodiversity, flooding, forests, urban, and water. Using the IAP, we investigate the direct and indirect implications of a wide range of climatic and socio-economic drivers to identify: (1) those sectors and regions most sensitive to future changes, (2) the mechanisms and directions of sensitivity (direct/indirect and positive/negative), (3) the form and magnitudes of sensitivity (linear/non-linear and strong/weak/insignificant), and (4) the relative importance of the key drivers across sectors and regions. The results are complex. Most sectors are either directly or indirectly sensitive to a large number of drivers (more than 18 out of 24 drivers considered). Over twelve of these drivers have indirect impacts on biodiversity, forests, land use diversity, and water, while only four drivers have indirect effects on flooding. In contrast, for the urban sector all the drivers are direct. Moreover, most of the driver-indicator relationships are non-linear, and hence there is the potential for 'surprises'. This highlights the importance of considering cross-sectoral interactions in future impact assessments. Such systematic analysis provides improved information for decision-makers to formulate appropriate adaptation policies to maximise benefits and minimise unintended consequences. [ABSTRACT FROM AUTHOR]

Evergreen trees in the Mediterranean region must cope with a wide range of environmental stresses from summer drought to winter cold. The mildness of Mediterranean winters can periodically lead to favourable environmental conditions above the threshold for a positive carbon balance, benefitting evergreen woody species more than deciduous ones. The comparatively lower solar energy input in winter decreases the foliar light saturation point. This leads to a higher susceptibility to photoinhibitory stress especially when chilly (< 12 ℃) or freezing temperatures (< 0 ℃) coincide with clear skies and relatively high solar irradiances. Nonetheless, the advantage of evergreen species that are able to photosynthesize all year round where a significant fraction can be attributed to winter months, compensates for the lower carbon uptake during spring and summer in comparison to deciduous species. We investigated the ecophysiological behaviour of three co-occurring mature evergreen tree species (Quercus ilex L., Pinus halepensis Mill., and Arbutus unedo L.). Therefore, we collected twigs from the field during a period of mild winter conditions and after a sudden cold period. After both periods, the state of the photosynthetic machinery was tested in the laboratory by estimating the foliar photosynthetic potential with CO2 response curves in parallel with chlorophyll fluorescence measurements. The studied evergreen tree species benefited strongly from mild winter conditions by exhibiting extraordinarily high photosynthetic potentials. A sudden period of frost, however, negatively affected the photosynthetic apparatus, leading to significant decreases in key physiological parameters such as the maximum carboxylation velocity (Vc,max), the maximum photosynthetic electron transport rate (Jmax), and the optimal fluorometric quantum yield of photosystem II (Fv/Fm). The responses of Vc,max and Jmax were highly species specific, with Q. ilex exhibiting the highest and P. halepensis the lowest reductions. In contrast, the optimal fluorometric quantum yield of photosystem II (Fv/Fm) was significantly lower in A. unedo after the cold period. The leaf position played an important role in Q. ilex showing a stronger winter effect on sunlit leaves in comparison to shaded leaves. Our results generally agreed with the previous classifications of photoinhibition-tolerant (P. halepensis) and photoinhibitionavoiding (Q. ilex) species on the basis of their susceptibility to dynamic photoinhibition, whereas A. unedo was the least tolerant to photoinhibition, which was chronic in this species. Q. ilex and P. halepensis seem to follow contrasting photoprotective strategies. However, they seemed equally successful under the prevailing conditions exhibiting an adaptive advantage over A. unedo. These results show that our understanding of the dynamics of interspecific competition in Mediterranean ecosystems requires consideration of the physiological behaviour during winter which may have important implications for long-term carbon budgets and growth trends. [ABSTRACT FROM AUTHOR]

Evergreen trees in the Mediterranean region must cope with a wide range of environmental stresses from summer drought to winter cold. The mildness of Mediterranean winters can periodically lead to favourable environmental conditions above the threshold for a positive carbon balance, benefitting evergreen woody species more than deciduous ones. The comparatively lower solar energy input in winter decreases the foliar light saturation point. This leads to a higher susceptibility to photoinhibitory stress especially when chilly (<12°C) or freezing temperatures (<0°C) coincide with clear skies and relatively high solar irradiances. Nonetheless, the advantage of evergreen species that are able to photosynthesize all year round where a significant fraction can be attributed to winter months, compensates for the lower carbon uptake during spring and summer in comparison to deciduous species. We investigated the ecophysiological behaviour of three co-occurring mature evergreen tree species (Quercus ilex L., Pinus halepensis Mill., and Arbutus unedo L.) during a period of mild winter conditions and their responses to a sudden cold period. The state of the photosynthetic machinery in both periods was thus tested by estimating the foliar photosynthetic potential with CO2 response curves in parallel with chlorophyll fluorescence measurements. The studied evergreen tree species benefited strongly from mild winter conditions by exhibiting extraordinarily high photosynthetic potentials similar to those under spring conditions. A sudden period of frost, however, negatively affected the photosynthetic apparatus, leading to significant decreases in key physiological parameters such as the maximum carboxylation velocity (Vc, max), the maximum photosynthetic electron transport rate (Jmax), and the optimal fluorometric quantum yield of photosystem II (Fv/Fm). This change persisted for several weeks after the cold period despite the recovery of the temperature to the conditions previous to the frost event. The responses of Vc, max and Jmax were highly species-specific, where Q. ilex exhibited the highest and P. halepensis the lowest reductions. In contrast, the optimal fluorometric quantum yield of photosystem II (Fv/Fm) was significantly lower in A. unedo after the cold period. The leaf position played an important role in Q. ilex showing a comparatively stronger winter effect on sunlit leaves. Our results generally agreed with the previous classifications of photoinhibition-avoiding (P. halepensis) and photoinhibition-tolerant (Q. ilex) species on the basis of their susceptibility to dynamic photoinhibition, whereas A. unedo was the least tolerant to photoinhibition, which was chronic in this species. Q. ilex and P. halepensis seem to follow contrasting photoprotective strategies which are, however, equally successful under the prevailing conditions exhibiting an adaptive advantage over A. unedo in our study site. These results show that our understanding of the dynamics of interspecific competition in Mediterranean ecosystems requires consideration of the physiological behaviour during winter which may have important implications for long-term carbon budgets and growth trends. [ABSTRACT FROM AUTHOR]

Drought-induced decline is affecting Pinus sylvestris populations in southern Europe, with very little impact on the more drought-tolerant Quercus pubescens. Although multiple studies have investigated interspecific differences in water use and growth strategies, the link between these two processes and how they vary within drought-exposed populations remains poorly understood. Here, we analysed tree ring and sap flow data from P. sylvestris and Q. pubescens stands in the Pyrenees in order to (1) evaluate differences in climate-growth responses among species, (2) disentangle the role of past growth trends and water use strategies in individual trees drought sensitivity and (3) assess whether such intraspecific patterns vary between species. Both species have suffered recent climatic constraints related to increased aridity. However, the effects of past growth trends and current water use traits on drought sensitivity varied among them. Initially, fast-growing 'drought-sensitive' pines displayed a higher gas exchange potential but were more sensitive to evaporative demand and soil moisture. They also showed lower water use efficiency for growth (WUE) and current growth decline. In contrast, initially, slow-growing 'drought-tolerant' pines showed the opposite water use traits and currently maintain the highest growth rates. In comparison, neither current WUE nor recent growth trends varied across Q. pubescens climate-growth groups. Nonetheless, 'drought-sensitive' oaks showed the lowest gas exchange potential and the highest growth rates under milder conditions. Our results show a strong effect of past growth trends and current water use strategies on tree resilience to increased aridity, which is more evident in P. sylvestris. [ABSTRACT FROM AUTHOR]

The presence of Salmonella spp. and levels of Enterobacteriaceae and aerobic plate count were determined in 300 bovine carcasses randomly collected in an industrial cattle slaughterhouse in Catalonia ( Spain) as part of a control programme to validate good slaughter practices according to Commission Regulation No 2073/2005. The verotoxigenic Escherichia coli O157 ( VTEC O157), although not currently legislated, was also investigated in the same carcasses due to the importance of bovines as a reservoir for this micro-organism. Virulence genes ( vtx1, vtx2 and eae), the presence of fli CH7 and antimicrobial susceptibility were studied in E. coli O157 isolates. Levels of Enterobacteriaceae and aerobic colonies and the presence of Salmonella were within the admissible range stipulated by current legislation. However, VTEC O157 was detected in 14·7% of carcasses. Among the VTEC O157 strains tested for antimicrobial susceptibility, 65% were multiresistant. Overall, the results of this study indicate that even with good manufacturing practices, contamination with VTEC O157 can occur and cattle meat can pose a risk to human health. These results confirm the need for a review of the appropriateness of introducing antimicrobial treatments in the processing of cattle carcasses in Europe. Significance and Impact of the Study This study describes the prevalence of verotoxigenic and multidrug-resistant E. coli O157 strains in bovine carcasses. These results suggest that despite the good manufacturing practices used in the slaughterhouse studied (the largest in Catalonia slaughtering over 81 000 cattle per year), the absence of verotoxigenic E. coli O157 in bovine carcasses cannot be guaranteed. [ABSTRACT FROM AUTHOR]

To evaluate the effects of carbonic fertilization and apical brushing (brushing of shoot apices to induce a negative thigmonastic response) on Prunus avium growth under nursery, carbon dioxide (CO2) was fed to cherry trees. Later, carbonic fertilization was withdrawn and apical brushing was applied. Finally, the original conditions were reinstated. Height and trunk diameter, allometric relations with plant biomass and relative growth rate were followed. Contrary to expectations, apical brushing resulted in increased trunk diameter and, hence, growth rate. Carbonic fertilization did not produce differences in the initial growth, probably owing to the deciduous characteristics of the species. Continuous application of carbonic fertilization maintained growth rate, whereas no fertilization or its withdrawal reduced the growth rate, but acclimation of the CO2-fed plants appeared by the end of the growing period. No differences in root growth potential at the end of the assay were observed between treatments. In conclusion, owing to the observed acclimation, carbonic fertilization is not advised throughout the complete period of growth. The tested treatments did not help to adapt supply of plant material of this species to the demand for revegetation. However, growth-slowing treatments may be applied to P. avium without any negative effects on potential root growth. [ABSTRACT FROM AUTHOR]

Fundamentally, El Niño Southern Oscillation (ENSO) is a climatic and oceanographic phenomenon, but it has profound effects on terrestrial ecosystems. Although the ecological effects of ENSO are becoming increasingly known from a wide range of terrestrial ecosystems (Holmgren et al., 2001), their impacts have been more intensively studied in arid and semiarid systems. In this brief communication, we summarize the main conclusions of a recent symposium on the effects of ENSO in these ecosystems, which was convened as part of the First Alexander von Humboldt International Conference on the El Niño Phenomenon and its Global Impact, in Guayaquil, Ecuador, from 16-20 May 2005. Participants in the symposium shared results and perspectives from research conducted in North and South America and Australia, regions where the ecological effects of ENSO have been studied in depth. Although the reports covered a wide array of organisms and ecological systems (Fig. 1), a recurring theme was the strong increase in rainfall associated with ENSO events in dry ecosystems (during the El Niño phase of the oscillation in the Americas and the La Niña phase in Australia). Because inter-annual variability in precipitation is such a strong determinant of productivity in arid and semiarid ecosystems, increased ENSO rainfall is crucial for plant recruitment, productivity and diversity in these ecosystems. Several long-term studies show that this pulse in primary productivity causes a subsequent increase in herbivores, followed by an increase in carnivores, with consequences for changes in ecosystem structure and functioning that can be quite complex. Much of the work presented at the symposium represents research that was or will be published elsewhere. However, we take this opportunity to summarize some of the main points that emerged from our presentations and the resulting discussion on the general effects of ENSO on arid and semiarid ecosystems. [ABSTRACT FROM AUTHOR]

Summary: • Fine‐root longevity and phenology were studied in a Quercus ilex (holm oak) forest in Prades (NE Spain). Differences were investigated among roots that had appeared in different seasons and at different depth intervals, differentiating between white and brown roots.• Using minirhizotrons installed in March 1994, 1211 roots were monitored every 3 wk from June 1994 to March 1997.• Mean and median fine‐root longevity were 125 ± 4 d and 67 d, respectively. Longevity of summer and winter roots was greater than that of spring and autumn roots. Although roots appeared and disappeared throughout the year, the rate of appearance was greatest in spring. Maximum longevity occurred at a soil depth of 20–30 cm. Differences among 10‐cm depth intervals were due to the number of days that roots were brown, since roots remained white for a similar number of days, independent of soil depth.• Temperate soil temperatures and lignotubers permitted the appearance of roots throughout the year. Holm oak fine roots might be more efficient during the first 50 d of their life before the white roots become less efficient brown roots. [ABSTRACT FROM AUTHOR]

Summary • Fine-root longevity and phenology were studied in a Quercus ilex (holm oak) forest in Prades (NE Spain). Differences were investigated among roots that had appeared in different seasons and at different depth intervals, differentiating between white and brown roots. • Using minirhizotrons installed in March 1994, 1211 roots were monitored every 3 wk from June 1994 to March 1997. • Mean and median fine-root longevity were 125 ± 4 d and 67 d, respectively. Longevity of summer and winter roots was greater than that of spring and autumn roots. Although roots appeared and disappeared throughout the year, the rate of appearance was greatest in spring. Maximum longevity occurred at a soil depth of 20–30 cm. Differences among 10-cm depth intervals were due to the number of days that roots were brown, since roots remained white for a similar number of days, independent of soil depth. • Temperate soil temperatures and lignotubers permitted the appearance of roots throughout the year. Holm oak fine roots might be more efficient during the first 50 d of their life before the white roots become less efficient brown roots. [ABSTRACT FROM AUTHOR]

We used minirhizotrons to determine the vertical distribution of fine roots in a holm oak (Quercus ilex L.) forest in a typical Mediterranean area over a 3-year period (June 1994–March 1997). We measured fine root density (number of roots per unit area), fine root length density (length of roots per unit area), fine root area index (area of roots per unit area) and fine root mean diameter. Variables were pooled for each 10-cm depth interval to a depth of 60 cm. Fine roots tended to decrease with increasing depth except between 0 and 10 cm, where the values of all fine root variables were less than in the 10-cm stratum below. Fine root vertical distribution was compared with soil water content and soil temperature at different depths in the soil profile. [ABSTRACT FROM PUBLISHER]