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Species assemblages and their interactions vary through space, generating diversity patterns at different spatial scales. Here, we study the local‐scale spatial variation of a cavity‐nesting bee and wasp community (hosts), their nest associates (parasitoids), and the resulting antagonistic network over a continuous and homogeneous habitat. To obtain bee/wasp nests, we placed trap‐nests at 25 sites over a 32 km2 area. We obtained 1,541 nests (4,954 cells) belonging to 40 host species and containing 27 parasitoid species. The most abundant host species tended to have higher parasitism rate. Community composition dissimilarity was relatively high for both hosts and parasitoids, and the main component of this variability was species turnover, with a very minor contribution of ordered species loss (nestedness). That is, local species richness tended to be similar across the study area and community composition tended to differ between sites. Interestingly, the spatial matching between host and parasitoid composition was low. Host β‐diversity was weakly (positively) but significantly related to geographic distance. On the other hand, parasitoid and host‐parasitoid interaction β‐diversities were not significantly related to geographic distance. Interaction β‐diversity was even higher than host and parasitoid β‐diversity, and mostly due to species turnover. Interaction rewiring between plots and between local webs and the regional metaweb was very low. In sum, species composition was rather idiosyncratic to each site causing a relevant mismatch between hosts and parasitoid composition. However, pairs of host and parasitoid species tended to interact similarly wherever they co‐occurred. Our results additionally show that interaction β‐diversity is better explained by parasitoid than by host β‐diversity. We discuss the importance of identifying the sources of variation to understand the drivers of the observed heterogeneity., We demonstrate that communities of mobile organisms and their interactions vary at a local scale (~500 m) even in a continuous and homogeneous habitat. Parasitoid, rather than host, spatial turnover is the major driver of the observed spatial heterogeneity in host‐parasitoid interactions. Nonetheless, interactions are also subjected to their own intrinsic variability.

Larger geographical areas contain more species—an observation raised to a law in ecology. Less explored is whether biodiversity changes are accompanied by a modification of interaction networks. We use data from 32 spatial interaction networks from different ecosystems to analyse how network structure changes with area. We find that basic community structure descriptors (number of species, links and links per species) increase with area following a power law. Yet, the distribution of links per species varies little with area, indicating that the fundamental organization of interactions within networks is conserved. Our null model analyses suggest that the spatial scaling of network structure is determined by factors beyond species richness and the number of links. We demonstrate that biodiversity–area relationships can be extended from species counts to higher levels of network complexity. Therefore, the consequences of anthropogenic habitat destruction may extend from species loss to wider simplification of natural communities., This work was supported by the TULIP Laboratory of Excellence (ANR-10-LABX-41 and 394 ANR-11-IDEX-002-02) to J.M.M., by a Region Midi-Pyrenees project (CNRS 121090) to J.M.M., and by the FRAGCLIM Consolidator Grant (726176) to J.M.M. from the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program. The study was also supported by Spanish MICINN projects CGL2009-12646, CSD2008-0040 and CGL2013-41856 to J.B. and A.R. C.E. was funded through the São Paulo Research Foundation (FAPESP 2015/15172-7). V.A.G.B. was funded by National Funds through FCT—Foundation for Science and Technology under the Project UIDB/05183/2020. W.T. received funding from the ERA-Net BiodivERsA—Belmont Forum, with the national funder Agence National pour la Recherche (FutureWeb: ANR-18-EBI4–0009 and BearConnect: ANR-16-EBI3-0003).

Data available via the Dryad Digital Repository https://doi.org/10.5061/dryad.63xsj3v39 (Roquer-Beni et al., 2021)., Functional traits mediate the response of communities to disturbances (response traits) and their contribution to ecosystem functions (effect traits). To predict how anthropogenic disturbances influence ecosystem services requires a dual approach including both trait concepts. Here, we used a response–effect trait conceptual framework to understand how local and landscape features affect pollinator functional diversity and pollination services in apple orchards. We worked in 110 apple orchards across four European regions. Orchards differed in management practices. Low-intensity (LI) orchards were certified organic or followed close-to-organic practices. High-intensity (HI) orchards followed integrated pest management practices. Within each management type, orchards encompassed a range of local (flower diversity, agri-environmental structures) and landscape features (orchard and pollinator-friendly habitat cover). We measured pollinator visitation rates and calculated trait composition metrics based on 10 pollinator traits. We used initial fruit set as a measure of pollination service. Some pollinator traits (body size and hairiness) were negatively related to orchard cover and positively affected by pollinator-friendly habitat cover. Bee functional diversity was lower in HI orchards and decreased with increased landscape orchard cover. Pollination service was not associated with any particular trait but increased with pollinator trait diversity in LI orchards. As a result, LI orchards with high pollinator trait diversity reached levels of pollination service similar to those of HI orchards. Synthesis and applications. Pollinator functional diversity enables pollinator communities to respond to agricultural intensification and to increase pollination function. Our results show that efforts to promote biodiversity provide greater returns in low-intensity than in high-intensity orchards. The fact that low-intensity orchards with high pollinator functional diversity reach levels of pollination services similar to those of high-intensity orchards provides a compelling argument for the conversion of high-intensity into low-intensity farms., This research (EcoFruit project) was funded through the 2013–2014 BiodivERsA/FACCE-JPI joint call (2014-74), Spanish MinECo (PCIN-2014-145-C02), German BMBF (PT-DLR/BMBF, 01LC1403) and Swedish Research Council Formas (2014-1784) by Formas (2013-934 to M.T.), Stiftelsen Lantbruksforskning (H1256150 to M.P.), INIA (RTA2013-00039-C03-00 to G.A. and M.M.), MinECo/FEDER (CGL2015-68963-C2-2-R to D.G.), FI-AGAUR (to L.R.-B.) and MinECo (RYC-2015-18448 to X.A.).

Hairiness is a salient trait of insect pollinators that has been linked to thermoregulation, pollen uptake and transportation, and pollination success. Despite its potential importance in pollination ecology, hairiness is rarely included in pollinator trait analyses. This is likely due to the lack of standardized and efficient methods to measure hairiness. We describe a novel methodology that uses a stereomicroscope equipped with a live measurement module software to quantitatively measure two components of hairiness: hair density and hair length. We took measures of the two hairiness components in 109 insect pollinator species (including 52 bee species). We analyzed the relationship between hair density and length and between these two components and body size. We combined hair density and length measures to calculate a hairiness index and tested whether hairiness differed between major pollinator groups and bee genera. Body size was strongly and positively correlated to hair length and weakly and negatively correlated to hair density. The correlation between the two hairiness components was weak and negative. According to our hairiness index, butterflies and moths were the hairiest pollinator group, followed by bees, hoverflies, beetles, and other flies. Among bees, bumblebees (Bombus) and mason bees (Osmia) were the hairiest taxa, followed by digger bees (Anthophorinae), sand bees (Andrena), and sweat bees (Halictini). Our methodology provides an effective and standardized measure of the two components of hairiness (hair density and length), thus allowing for a meaningful interpretation of hairiness. We provide a detailed protocol of our methodology, which we hope will contribute to improve our understanding of pollination effectiveness, thermal biology, and responses to climate change in insects., Hairiness is a fundamental functional trait in pollinator ecology related to thermoregulation and pollination effectiveness. Surprisingly, there is a lack of standard methods to measure this trait. We provide an effective method to quantitatively measure hairiness to contribute to filling an important gap in pollinator data bases and to improve our understanding of the ecology and evolution of a threatened group of organisms that provide an essential ecosystem service.

Ecological communities are dynamic entities subjected to extinction/colonization events. Because species are connected through complex interaction networks, the arrival of a new species is likely to affect various species across the community, as observed in plant biological invasions. However, plant invasions usually represent extreme scenarios in which the community is strongly dominated by the alien species, confounding the effects of a change in species composition with a massive increase in floral resource availability. Our study addresses changes in plant community composition involving native species, a common phenomenon under the current climate change scenario in which plants are modifying their distribution ranges. We experimentally manipulated patches of a natural scrubland community by introducing a native plant (henceforth colonizing plant). To avoid introducing a disproportionate amount of floral resources we adjusted the number of flowers of the colonizing plant to the amount of floral resources locally available in each patch. We had two objectives: (1) to analyse the effects of the arrival of a new plant on the pollinator community, the rearrangement of plant-pollinator interactions and the structure of the plant-pollinator network; (2) to evaluate potential consequences for pollination and the reproductive success of resident plant species. The colonizing plant acted as a magnet species, attracting bumble bees and facilitating interactions to other plants through spill-over. The introduction of the colonizing plant also affected the structure of plant-pollinator networks (colonized networks were more generalized and more nested than control networks) and modified the arrangement of plant and pollinator species into modules. Ultimately, these changes resulted in higher heterospecific (but not conspecific) pollen deposition and had contrasting effects on the reproductive success of two resident plant species (higher fruit set and lower seed set, respectively). Our study shows that relationships between plants and pollinators are rapidly rearranged in response to novel situations (even when the new plant is not overly dominant), with important functional consequences on pollination and plant reproductive success. Our study establishes a link between network structure and pollination and plant reproductive success, which may be mediated by differences among pollinator species in foraging behavior.

Large-scale spatial variability in plant-pollinator communities (e.g. along geographic gradients, across different landscapes) is relatively well understood. However, we know much less about how these communities vary at small scales within a uniform landscape. Plants are sessile and highly sensitive to microhabitat conditions, whereas pollinators are highly mobile and, for the most part, display generalist feeding habits. Therefore, we expect plants to show greater spatial variability than pollinators. We analysed the spatial heterogeneity of a community of flowering plants and their pollinators in 40 plots across a 40-km(2) area within an uninterrupted Mediterranean scrubland. We recorded 3577 pollinator visits to 49 plant species. The pollinator community (170 species) was strongly dominated by honey bees (71.8% of the visits recorded). Flower and pollinator communities showed similar beta-diversity, indicating that spatial variability was similar in the two groups. We used path analysis to establish the direct and indirect effects of flower community distribution and honey bee visitation rate (a measure of the use of floral resources by this species) on the spatial distribution of the pollinator community. Wild pollinator abundance was positively related to flower abundance. Wild pollinator visitation rate was negatively related to flower abundance, suggesting that floral resources were not limiting. Pollinator and flower richness were positively related. Pollinator species composition was weakly related to flower species composition, reflecting the generalist nature of flower-pollinator interactions and the opportunistic nature of pollinator flower choices. Honey bee visitation rate did not affect the distribution of the wild pollinator community. Overall, we show that, in spite of the apparent physiognomic uniformity, both flowers and pollinators display high levels of heterogeneity, resulting in a mosaic of idiosyncratic local communities. Our results provide a measure of the background of intrinsic heterogeneity within a uniform habitat, with potential consequences on low-scale ecosystem function and microevolutionary patterns.

Understanding how ecological networks are assembled is important because network structure reflects ecosystem functioning and stability. Quantitative network analysis incorporates measures of interaction strength as an estimate of the magnitude of the effect of interaction partners on one another. Most plant-pollinator network studies use frequency of interaction between individual pollinators and individual plants (encounter) as a surrogate of interaction strength. However, the number of flowers visited per encounter may strongly vary among pollinator and plant species, and therefore not all encounters are quantitatively equivalent. We sampled plant-pollinator interactions in a Mediterranean scrubland and tested whether using a measure of interaction strength based on the number of flowers visited resulted in changes in species (species strength, interaction species asymmetry, specialization) and network descriptors (nestedness, H2', interaction evenness, plant generality, pollinator generality) compared to the encounter-based measure. Several species (including some of the most abundant ones) showed important changes in species descriptors, notably in specialization. These changes were especially important in plant species with large floral displays, which became less specialized with the visit-based measure of interaction strength. At the network level we found significant changes in all properties analysed. With the encounter-based approach plant generality was much higher than pollinator generality (high specialization asymmetry between trophic levels). However, with the visit-based approach plant generality was greatly reduced so that plants and pollinators had similar levels of generalization. Interaction evenness also decreased strongly with the visit-based approach. We conclude that accounting for the number of flowers visited per encounter provides a more ecologically relevant measure of interaction strength. Our results have important implications for the stability of pollination networks and the evolution of plant-pollinator interactions. The use of a visit-based approach is especially important in studies relating interaction network structure and ecosystem function (pollination and/or exploitation of floral resources).

The research was part of the EcoFruit project funded through the 2013-2014 BiodivERsA/FACCEJPI joint call(agreement BiodivERsA-FACCE2014-74),with the national funders German Federal Ministry of Education and Research(PT-DLR/BMBF) (grant 01LC1403), the Spanish Ministerio de Economía y Competitividad (MinECo) (project PCIN-2014-145-C02)and Swedish Research Council Formas(grant2014-1784).There search was also funded by Formas(grant2013-934 to MT),Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (project RTA2013-00039-C03-00 to GA and MM;FPI-INIA fellow ship to RMS),MinECo/FEDER (project CGL2015-68963-C2-2-R to DG) and FI fellowship(Generalitat de Catalunya) to LRB, Happe, A.-K., Alins, G., Blüthgen, N., Boreux, V., Bosch, J., García, D., Hambäck, P.A., Klein, A.-M., Martínez-Sastre, R., Miñarro, M., Müller, A.-K., Porcel, M., Rodrigo, A., Roquer-Beni, L., Samnegård, U., Tasin, M., Mody, K.

Natural and semi-natural habitats within agricultural landscapes provide food and nesting resources for wild bees, thus promoting crop pollination services. In central Spain, a large network of drove roads (DRs) crosses extensive areas of intensive agricultural fields. DRs are tracks (20⿿75 m wide) with semi-natural vegetation, protected for their priority function of transhumant livestock herding. In this study, we analyse the bee community of one of the main Spanish DRs, and evaluate its effects on flower visitation and seed set in adjacent sunflower fields. We used pan traps to assess bee abundance and richness at 13 sites along the DR and in adjacent sunflower fields at 10, 75 and 150 m from the DR. We also conducted visual counts to assess visitation rates to sunflower heads and measured seed set. Wild bee abundance and richness were significantly higher in the DR than in sunflower fields; but there were no significant differences among distances within sunflower fields. Honey bee abundance did not differ between the DR and sunflower fields. Wild bee visitation to sunflower heads was higher at 10 m compared to 75 and 150 m from the DR, but differences in honey bee visitation were non-significant. Sunflower seed set was significantly higher at 10 m compared to 75 and 150 m, and was associated with wild bee abundance, but not with honey bee abundance. Our results show that livestock DRs act as reservoirs of wild bee diversity within intensive agricultural matrices, enhancing wild bee visitation and seed set in adjacent sunflower crops.

The importance of storm frequency as well as the groundwater and hyporheic inputs on nitrate (NO3-N) and ammonium (NH4-N) levels in stream water were studied in a small perennial Mediterranean catchment, Riera Major, in northeast Spain. NO3-N concentrations ranged from 0.15 to 1.9 mg l-1. Discharge explained 47% of the annual NO3-N concentration variance, but this percentage increased to 97% when single floods were analysed. The rate of change in nitrate concentration with respect to flow, ΔNO3-N/ΔQ, ranged widely from 0 to 20 μg NO3-N s l-2. The ΔNO3-N/ΔQ values fitted to a non linear model with respect to the storm flow magnitude (ΔQ) (r2=0.48, d.f.=22, P3-N/ΔQ occurred at intermediate ΔQ values, whereas low ΔNO3-N/ΔQ values occurred during severe storms (ΔQ > 400 l s-1). N3-N concentrations exhibit anticlockwise hysteresis patterns with changing flow and the patterns observed for autumnal and winter storms indicated that groundwater was the main N3-N source for stream and hyporheic water. At baseflow, NO3-N concentration in groundwater was higher (t=4.75, d.f.=29, P>0.001) and co-varied with concentrations in the stream (r=0.91, d.f.=28, P3-N concentration in hyporheic water was identical to that in stream water. The role of the hyporheic zone as source or sink for ammonium was studied hyporheic was studied comparing its concentrations in stream and hyporheic zone before and after a major storm occurred in October 1994 that removed particulate organic matter stored in sediments. Results showed high ammonium concentrations (75±28 s.d. μg NH4-N l-1) before the storm flow in the hyporheic zone. After the storm, the ammonium concentration in the hyporheic dropped by 80% (13.6±8 μg N4-N l-1) and approached to the level found in stream water (11±8 μg NH4-N l-1) indicating that indisturbed hyporheic sediments act as a source for ammonium. After the storm, the ammonium concentrations in the stream, hyporheic and groundwater zones were very similar suggesting that stream ammonium concentrations are sustained mainly by input from groundwater. The present study provides evidence that storm flow magnitude is an important source of variability of nitrate concentration and fluxes in Mediterranean streams subjected to an irregular precipitation regime with prolonged dry periods. Keywords: nitrate, discharge regime, hyporheic zone, groundwater, Mediterranean, stream, Riera Major

Fire weather indices predict fire extent from meteorological conditions assuming a monotonic function; this approach is frequently used to predict future fire patterns under climate change scenarios using linear extrapolation. However, the relationship between weather and fire extent may potentially depend on the existence of fuel humidity thresholds above which this relationship changes dramatically, challenging this statistical approach. Here we combine the continuous and the threshold approaches to analyze satellite-detected fires in Europe during 2001–2010 in relation to meteorological conditions, showing that fire size response to increasing dryness follows a ramp function, i.e. with two plateaus separated by a phase of monotonic increase. This study confirms that at a continental and a high-resolution temporal scales, large fires are very unlikely to occur under moist conditions, but it also reveals that fire size stops to be controlled by fuel humidity above a given threshold of dryness. Thus, fuel humidity control only applies when fire is not limited by other factors such as fuel load, as large fires are virtually absent in dry regions with less than 500 mm of average annual rainfall, i.e. where fuel amount is insufficient. In regions with sufficient fuel, other factors such as fire suppression or fuel discontinuity can impede large fires even under very dry weather conditions. These findings are relevant under current climatic trends in which the fire season length, in terms of number of days with DC (drought code) values above the observed thresholds (break points), is increasing in many parts of the Mediterranean, while it is decreasing in Eastern Europe and remains unchanged in Central Europe.

Species flower production and flowering phenology vary from year to year due to extrinsic factors. Inter-annual variability in flowering patterns may have important consequences for attractiveness to pollinators, and ultimately, plant reproductive output. To understand the consequences of flowering pattern variability, a community approach is necessary because pollinator flower choice is highly dependent on flower context. Our objectives were: 1) To quantify yearly variability in flower density and phenology; 2) To evaluate whether changes in flowering patterns result in significant changes in pollen/nectar composition. We monitored weekly flowering patterns in a Mediterranean scrubland community (23 species) over 8 years. Floral resource availability was estimated based on field measures of pollen and nectar production per flower. We analysed inter-annual variation in flowering phenology (duration and date of peak bloom) and flower production, and inter-annual and monthly variability in flower, pollen and nectar species composition. We also investigated potential phylogenetic effects on inter-annual variability of flowering patterns. We found dramatic variation in yearly flower production both at the species and community levels. There was also substantial variation in flowering phenology. Importantly, yearly fluctuations were far from synchronous across species, and resulted in significant changes in floral resources availability and composition at the community level. Changes were especially pronounced late in the season, at a time when flowers are scarce and pollinator visitation rates are particularly high. We discuss the consequences of our findings for pollinator visitation and plant reproductive success in the current scenario of climate change.

In Mediterranean ecosystems, post-fire forestry management practices are often used to improve forest structure and to reduce the risk of fire in coppices of resprouting species. Such practices enhance tree growth (i.e., height), probably because they release resources. On the one hand, resource release may stimulate reproduction. On the other hand, tree species that are regenerating after a fire may already face a delay in reproduction, and this delay may be lengthened if species mainly invest these additional resources in growth. Within this theoretical framework, it is poorly understood how different forest management practices affect the reproductive abilities of forest species. In this study, we analyzed the effect of two post-fire forestry treatments (selective thinning of resprouts and selective thinning of resprouts plus understory clearing) on a Mediterranean coppice dominated by the resprouter species Arbutus unedo L.; in particular, we examined how the treatments affected this species’ reproductive ability (flower and fruit production at the tree and stand level, as well as fruit characteristics). Our results show that the treatments had no effects on the number of flowers and mature fruits per individual. Meanwhile, mature fruit dry mass and seed set were greater in plots that had been both thinned and cleared than in control plots and plots that had only been thinned. This pattern was reversed for seed abortion rate: it was lower in plots that had been thinned and cleared. The dry mass of developed seeds did not differ among treatments. At the stand level, the percentage of strawberry trees that flowered, the percentage of strawberry trees that bore fruit, the dry biomass of mature fruits per hectare, and the number of developed seeds per hectare were not affected by these treatments. Other studies have shown that these two forest management practices can improve the vertical and horizontal structure of A. unedo coppices that are regenerating post fire; this study demonstrates that selective thinning does not modify the species’ reproductive success and, such practice when combined with understory clearing might enhance it. Consequently, these forestry practices might ensure the natural regeneration of populations of this species, as well as the availability of food for local fauna. It is thus highly recommended that such practices be used to manage coppices dominated by resprouter species following fire, especially in situations where the growth of the forest canopy has stagnated and/or reproduction of forest species has been delayed.

Climate change, alteration of atmospheric composition, land abandonment in some areas and land use intensification in others, wildfires and biological invasions threaten forests, shrublands and pastures all over the world. However, the impacts of the combinations between global change factors are not well understood despite its pressing importance. Here we posit that reviewing global change factors combination in an exemplary region can highlight the necessary aspects in order to better understand the challenges we face, warning about the consequences, and showing the challenges ahead of us. The forests, shrublands and pastures of the Mediterranean Basin are an ideal scenario for the study of these combinations due to its spatial and temporal heterogeneity, increasing and diverse human population and the historical legacy of land use transformations. The combination of multiple global change factors in the Basin shows different ecological effects. Some interactions alter the effects of a single factor, as drought enhances or decreases the effects of atmospheric components on plant ecophysiology. Several interactions generate new impacts: drought and land use changes, among others, alter water resources and lead to land degradation, vegetation regeneration decline, and expansion of forest diseases. Finally, different factors can occur alone or simultaneously leading to further increases in the risk of fires and biological invasions. The transitional nature of the Basin between temperate and arid climates involves a risk of irreversible ecosystem change towards more arid states. However, combinations between factors lead to unpredictable ecosystem alteration that goes beyond the particular consequences of drought. Complex global change scenarios should be studied in the Mediterranean and other regions of the world, including interregional studies. Here we show the inherent uncertainty of this complexity, which should be included in any management strategy., The present review is an outcome of the research project MONTESConsolider (CSD2008-00040), funded by the Spanish Ministry of Economy and Competitiveness.

Gynodioecy is a dimorphic breeding system in which female individuals coexist with hermaphroditic individuals in the same population. Females only contribute to the next generation via ovules, and many studies have shown that they are usually less attractive than hermaphrodites to pollinators. Several mechanisms have been proposed to explain how females manage to persist in populations despite these disadvantages. The ‘resource reallocation hypothesis’ (RRH) states that females channel resources not invested in pollen production and floral advertisement towards the production of more and/or larger seeds. We investigated pollination patterns and tested the RRH in a population of Thymus vulgaris. We measured flower display, flower size, nectar production, visitation rates, pollinator constancy and flower lifespan in the two morphs. In addition, we measured experimentally the effects of pollen and resource addition on female reproductive success (fruit set, seed set, seed weight) of the two morphs. Despite lower investment in floral advertisement, female individuals were no less attractive to pollinators than hermaphrodites on a per flower basis. Other measures of pollinator behaviour (number of flowers visited per plant, morph preference and morph constancy) also showed that pollinators did not discriminate against female flowers. In addition, stigma receptivity was longer in female flowers. Accordingly, and contrary to most studies on gynodioecious species, reproductive success of females was not pollen limited. Instead, seed production was pollen limited in hermaphrodites, suggesting low levels of cross-pollination in hermaphrodites. Seed production was resource limited in hermaphrodites, but not in females, thus providing support for the RRH. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 175, 395–408.

Fire weather indices predict fire extent from meteorological conditions assuming a monotonic function; this approach is frequently used to predict future fire patterns under climate change scenarios using linear extrapolation. However, the relationship between weather and fire extent may potentially depend on the existence of fuel moisture content thresholds above which this relationship changes dramatically, challenging this statistical approach. Here, we combine the continuous and the threshold approaches to analyze satellite-detected fires in Europe during 2001–2010 in relation to meteorological conditions, showing that fire size response to decreasing fuel moisture content follows a ramp function, i.e., with two plateaus separated by a phase of monotonic increase. This study confirms that at continental and high-resolution temporal scales, large fires are very unlikely to occur under moist conditions, but it also reveals that fire size stops to be controlled by fuel moisture content above a given threshold of dryness. Thus, fuel moisture content control only applies when fire is not limited by other factors such as fuel load, as large fires were virtually absent during the considered period in dry regions with less than 500 mm of average annual precipitation, i.e., low-productive areas where fuel amount would be scarce and discontinuous. In regions with sufficient fuel, other factors such as fire suppression or fuel discontinuity can impede large fires even under very dry weather conditions. These findings are relevant under current climatic trends in which the fire season length, in terms of number of days with drought code values above the observed thresholds (break points), is increasing in many parts of the Mediterranean, while it is decreasing in eastern Europe and remains unchanged in central Europe.

Summary This work explored the invasion patterns of Conyza species in Mediterranean pine forests after fire and identified their main correlates through a temporal study approach. We hypothesised that wildfires might favour Conyza spp. invasion in these forests, but only transiently and depending on fire regime. We recorded Conyza spp. invasion and subsequent extinction in plots from species' occurrence and cover in vegetation surveys. We also explored the association of Conyza spp. presence and cover with a set of climatic, landscape and local (plot) factors using GLZ and GLM. We assessed changes in significant factors over time with a Wilcoxon test for paired samples. Evidence for Conyza spp. establishment was found in two-thirds of the study plots, with an invasion peak 2 years after fire. Local factors related to resource availability, including high fire severity, low soil stoniness and total vegetation cover and high herbaceous cover, were significantly correlated with Conyza occurrence in plots at the invasion peak. However, Conyza cover was always low (≤6%) and populations did not persist more than several years, thus becoming rarer as plant cover increased. Landscape and climatic factors showed no association with Conyza occurrence. In conclusion, wildfires favour transient invasion of European Mediterranean pine forests by Conyza spp. Invasion is mostly enhanced by local fire severity and constrained by subsequent vegetation recovery, while it is poorly explained by climate and landscape, either current or historical.

In recent years, several Mediterranean forests subject to fire are becoming increasingly dominated by the resprouter species Arbutus unedo L. (strawberry tree). However, there is little information available about the management of these areas, and it is not clear if the approaches utilized for other, more abundant Mediterranean resprouter species such as Quercus ilex and Quercus cerrioides would produce similar results for A. unedo. In this study, performed in the NE Iberian Peninsula, we analyzed the effect of two post-fire treatment types, selective thinning and selective thinning plus understory clearing, on the growth of retained A. unedo resprouts and the new resprouting induced by the treatment itself. Treatment effects were analyzed at both the individual and plot level. Our results showed that, in the short term, retained resprouts on treated trees grew more in height and diameter (absolute and relative) than those on control trees, with no differences seen between treatment types. In the intermediate term, all the strawberry trees occurring on treated plots grew longer, and this growth was greater in plots that had been both thinned and cleared. New, induced resprouts were unaffected by the type of treatment applied. In contrast to other studies, we failed to find a negative relationship between the degree of induced resprouting and retained resprout growth We therefore conclude that, irrespective of understory clearing, the selective thinning of A. unedo improves coppice vertical structure. Retained resprouts grow more in diameter and will thus more rapidly become exploitable as firewood and timber. Also, the tree is kept free of dead fuel, reducing the risk of spreading fire.

Anna Eklöf et al., How many dimensions (trait-axes) are required to predict whether two species interact? This unanswered question originated with the idea of ecological niches, and yet bears relevance today for understanding what determines network structure. Here, we analyse a set of 200 ecological networks, including food webs, antagonistic and mutualistic networks, and find that the number of dimensions needed to completely explain all interactions is small (< 10), with model selection favouring less than five. Using 18 high-quality webs including several species traits, we identify which traits contribute the most to explaining network structure. We show that accounting for a few traits dramatically improves our understanding of the structure of ecological networks. Matching traits for resources and consumers, for example, fruit size and bill gape, are the most successful combinations. These results link ecologically important species attributes to large-scale community structure. © 2013 Blackwell Publishing Ltd/CNRS., AE and JCK supported by NSF EF # 0827493. AE also by SOEB. SA supported by DEB #1148867. BD supported by Carlsberg foundation and the Danish Council for Independent research. AMMG supported by Spanish Ministry of Education, BVA-2010-0845. PRG supported by FAPESP. MAP supported by CNPq. JMT supported by a Rutherford Discovery Fellowship, RSNZ. RCU, NPC, SBL and DPV supported by CONICET (PIP 2781 and 6564), FONCyT (PICT 1471 and 20805) and BBVA Foundation (BIOCON03-162). JB and AR supported by Spanish MICNN (CICYT CGL2005-00491) and CONSOLIDER (csd2008-0040)

Here we report how fire recurrence increases the distribution of a scarce forest type in NE Spain that is dominated by the resprouter tree species Arbutus unedo. We used a combination of GIS and field surveys to determine the effect of fire and pre-fire vegetation on the appearance of A. unedo forests. In the field, we also analyzed the factors that promote fire and lead to the appearance of A. unedo forests. Our results reveal an increased occurrence of A. unedo forests in NE Spain in recent years; this phenomenon was strongly related to fire recurrence and the vegetation type present prior to fire. Most Pinus halepensis forests that burned more than once gave rise to A. unedo forests. Our results indicate that these conversions were related to a reduction in pine density coupled with increases in the density and size of A. unedo trees due to recurrent fires. Given that fires are increasing in number and magnitude in the Mediterranean, we predict a major change in landscape structure and composition at the regional scale.

Land use changes and shifts in disturbance regimes (e.g. wildfires) are recognized worldwide as two of the major drivers of the current global change in terrestrial ecosystems. We expect that, in areas with large-scale land use changes, legacies from previous land uses persist and affect current ecosystem responses to climate-associated disturbances like fire. This study analyses whether post-fire vegetation dynamics may differ according to specific historical land use histories in a Mediterranean forest landscape of about 60,000 ha that was burnt by extensive fires. For that, we assessed land use history of the whole area through the second half of the XXth century, and evaluated the post-fire regeneration success in terms of: (i) forest cover and (ii) tree species composition (biotic-dispersed, resprouter species, Quercus spp. vs. wind-dispersed species with or without fire-resistant seed bank, Pinus spp.). Results showed that stable forest areas exhibited a higher post-fire recovery than younger forests. Furthermore, the longer since crop abandonment translates into a faster post-fire recovery. Results highlight that to anticipate the impacts of disturbances on ecosystems, historical land trajectories should be taken into account. Collaborative work was facilitated by the Consolider-Ingenio Montes CSD2008-00040 project by Spanish Ministry of Science and Innovation. Postdoctoral and predoctoral fellowships to CPP (EX2009-0703) and BSH (FPU) were provides by Spanish Ministry of Education.

We study compartmentalization in a Mediterranean pollination network using three different analytical approaches: unipartite modularity (UM), bipartite modularity (BM) and the group model (GM). Our objectives are to compare compartments obtained with these three approaches and to explore the role of several species attributes related to pollination syndromes, species phenology, abundance and connectivity in structuring compartmentalization. BM could not identify compartments in our network. By contrast, UM revealed four modules composed of plants and pollinators, and GM four groups of plants and five of pollinators. Phenology had a major influence on compartmentalization, and compartments (both UM and GM) had distinct phenophases. Compartments were also strongly characterized by species degree (number of connections) and betweenness centrality. These two attributes were highly related to each other and to phenophase duration. Differences among compartments in abundance were only apparent with GM. We attribute this to the fact that abundance is strongly correlated with Degree, and the GM algorithm is particularly powerful at discriminating species based on degree. On the other hand, the role of pollination syndrome-related features in compartmentalization mostly emerged with UM. Only UM compartments differed in corolla length and pollen production. Both UM and GM compartments differed in their pollinator spectra. We found inconsistent reciprocity between plant attributes and pollinator spectra, thus it is difficult to conclude compartments follow clear-cut syndromes. Also, both UM and GM identified a compartment composed of pollinators with long activity periods that acted as connectors, linking all compartments providing cohesiveness to the network.

Aim Forest ecosystems dominated by fire-sensitive species could suffer shifts in composition under altered crown fire regimes mediated by climate change. The aims of this study were to: (1) study the spatio-temporal patterns and the climatic distribution of fires in Scots pine (Pinus sylvestris) forests during the last 31 years in north-eastern Spain, (2) evaluate the climatic vulnerability to fire of these forests in Spain, (3) analyse the regeneration of Scots pine after fire, and (4) predict the mid-term maintenance or replacement of Scots pine in burned areas. Location Catalonia (north-eastern Spain): the southern distribution limit of Scots pine. Methods We characterized the spatio-temporal and the climatic distribution of fires that occurred in Catalonia between 1979 and 2009. We used a generalized linear model to characterize the climatic vulnerability to fire of Scots pine in the whole of Spain. We assessed the regeneration of the species after crown fires in nine burned areas in Catalonia. The resulting data were integrated into a stochastic matrix model to predict the mid-term maintenance or replacement of Scots pine in burned areas. Results During the last three decades, Scots pine forests distributed in dry sites were most affected by fire. Our assessment of the vulnerability to fire of Scots pine forests in Spain as a whole, based on climatic and topographical variables, showed that 32% of these forests are vulnerable to fire, and that this proportion could increase to 66% under a conservative climate change scenario. Field data showed almost no regeneration of Scots pine after crown fires, and a limited capacity to recolonize from unburned edges, even in relatively old fires, with 90% of recruits located in the first 25 m from the edge. This process could be delayed by the elapsed time for new recruits to achieve reproductive maturity, which we estimated to be c. 15 years. Finally, our matrix model predicted the replacement of burned Scots pine forests by oak (Quercus sp.) forests, shrublands or mixed resprouter forests. Main conclusions Increased vulnerability to fire of Scots pine forests under future, warmer conditions may result in vegetation shifts at the southern edge of the distribution of the species.

Harvesting ants can affect the regeneration of plants through at least two different processes: seed removal and seed dispersal. We analyse the role of different foraging strategies of ants on patterns of seed removal and dispersal by three Messor species with considerable differences in their foraging systems. Messor capitatus workers rarely leave the nest in well-formed columns, while the other two species form foraging trails, with M. bouvieri forming temporary trails and M. barbarus foraging on a stable system of permanent foraging trails. Overall seed intake of M. capitatus colonies is considerably less than that of the two group-foraging species. There are also differences in the size of seeds collected: M. barbarus and M. capitatus harvest similar amounts of large and small seeds, while M. bouvieri harvests small seeds more intensely than large ones, due to the smaller size of the worker caste. The three Messor species differ in the percent of seed dropping of the different seed type and in the seed dispersal distance. Moreover, M. bouvieri and M. capitatus redistributed dropped seeds preferentially in bare soil and low sparse vegetation habitats, while M. barbarus redistributed seeds mainly in the high vegetation habitat. These results show that the foraging systems of these harvesting ants determine different patterns of seed removal and dispersal and, thus, affect the abundance and redistribution of seeds in the area. © 2010 International Union for the Study of Social Insects (IUSSI).

Most obligate seeder species build up a soil seed bank that is associated with massive seed germination in the year immediately after a fire. These species are also shade-intolerant and disappear when vegetation cover closes, creating unsuitable conditions for seedling recruitment. The only way for these plants to expand their populations is when habitats suitable for seedling recruitment arise (i.e. in years immediately after a fire). However, short primary seed dispersal of obligate seeders does not allow these plants to colonise the suitable habitats, and these habitats can only be colonised by secondary seed dispersion. We hypothesised that Fumana ericoides, an obligate-seeding small shrub, not only establishes abundantly in the first year after fire, but also expands its local range in the following years due to secondary dispersal by ants while suitable habitats are still available. We tested this hypothesis using experimental studies and a simulation model of potential population expansion in a recently burned area. Results showed that F. ericoides not only established prolifically in the year immediately after fire, but was also able to recruit new individuals and expand its population in the years following the fire, despite a low germination rate and short primary seed dispersal. Ant-mediated seed dispersal and availability of suitable habitats were key factors in this phenomenon: ants redistributed seeds in suitable habitats while they were available, which accelerated the expansion of F. ericoides because new plants established far away from the core population.

This study analyzes the effect of fire on the composition and abundance of ground beetles in Pinus nigra forests. We used pitfall traps to sample beetles in burned P. nigra forests in Catalonia (Spain). Since fire dramatically alters forest structure and composition and beetles follow vegetation changes, we expected drastic changes in beetle composition and abundance immediately after fire. Because P. nigra forests do not recover after fire, we also expected beetles in burned and unburned areas to differ along a chronosequence. Beetle abundance per plot increased in canopy-fire–burned areas, but per plot species richness, diversity, and dominance were not affected by fire. Species composition varied depending on fire intensity. Some species were associated with canopy fire and low vegetation cover. Other species were associated with shrub cover and time since fire. Finally, some species were not dependent on fire or vegetation cover. Beetle abundance in burned areas was independent of time since ...

Vegetation is one of the main factors affecting the composition and structure of ant communities. The effect of vegetation is both by offering food resources and by modifying the proportion of ground cover exposed to shade conditions. However, it is difficult in field studies to uncouple the effects of food resources and shade on animal communities. The goal of this study was to analyze experimentally the effects of vegetation through food and shade supply on the structure and composition of a Mediterranean ant community. We have crossed these two factors in a factorial design where we have eliminated vegetation in experimental treatments and we have simulated the effects of vegetation by manipulating separately the supply of food resources and shade. The expected decrease in ant abundance and richness in plots without food resources but with shade was only partially confirmed by the results, because there was a decrease in the number of ant species but not a significant decrease in overall ant abundance in plots without food resources. We did not confirm the second hypothesis that the decrease in shade while maintaining food resources resulted in an increase of heat-tolerant, subordinate species and, consequently, ant richness. Species composition differed in the different experimental treatments. Stress-tolerant species were abundant in areas without shade and without food resources. Heat-tolerant species were mainly present in plots without shade but with food resources. Finally, species with high requirements of shade and/or food resources were associated to control plots with both shade and food resources from vegetation. Overall, this study provides an experiment that uncouples experimentally shade and food resources and dissects their effects on the whole ant community, and shows that the effects of the two factors are independent and affect different components of ant community structure and composition.

This study analyzes the recovery of Pinus pinea in forested areas that have burned in the last 30 years. The main objectives of the study were (i) to analyze the success of the regeneration of P. pinea in areas with the presence or absence of surviving adult trees and (ii) to investigate whether or not the post-fire response of P. pinea may affect its present distribution. We analyzed the survival of adult P. pinea trees and the regeneration of P. pinea seedlings in 8 areas burned by wildfires in Catalonia (northeast Spain) between 1979 and 2001. This study shows that the inability of seedlings to establish after fire, together with the short seed dispersal distance of this species and the low level of seedling survival, renders the natural regeneration of P. pinea in burned areas difficult. A comparison of the presence of P. pinea in plots located in burned and unburned areas throughout its distribution area in Catalonia indicates that its presence at the regional level is clearly reduced after ...

Due to the contribution of honey bees (Apis mellifera) to wild flower and crop pollination, beekeeping has traditionally been considered a sustainable practice. However, high honey bee densities may have an impact on local pollen and nectar availability, which in turn may negatively affect other pollinators. This is exacerbated by the ability of honey bees to recruit foragers to highly rewarding flower patches. We measured floral resource consumption in rosemary (Rosmarinus officinalis) and thyme (Thymus vulgaris) in 21 plots located at different distances from apiaries in the scrubland of Garraf Natural Park (Barcelona), and related these measures to visitation rates of honey bees, bumblebees (Bombus terrestris) and other pollinators. In the same plots, we measured flower density, and used pan traps to characterize the wild bee community. Flower resource consumption was largely explained by honey bee visitation and marginally by bumblebee visitation. After accounting for flower density, plots close to apiaries had lower wild bee biomass. This was due to a lower abundance of large bee species, those more likely to be affected by honey bee competition. We conclude that honey bees are the main contributors to pollen/nectar consumption of the two main flowering plants in the scrubland, and that at the densities currently occurring in the park (3.5 hives/km2) the wild bee community is being affected. Our study supports the hypothesis that high honey bee densities may have an impact on other pollinators via competition for flower resources. Wegen des Beitrages der Honigbiene (Apis mellifera) bei der Bestäubung von Wildblumen und Nutzpflanzen wurde die Bienenhaltung traditionell als eine nachhaltige Aktivität angesehen. Indessen können hohe Honigbienendichten Auswirkungen auf die lokale Verfügbarkeit von Nektar und Pollen haben, was wiederum andere Bestäuber negativ beeinflussen könnte. Dies wird verstärkt durch die Fähigkeit der Honigbiene, Sammlerinnen zu lohnenden Sammelstellen zu dirigieren. Im Buschland des Garraf-Naturparks bei Barcelona maßen wir den Verbrauch von Blütenressourcen an Rosmarin (Rosmarinus officinalis) und Thymian (Thymus vulgaris) an 21 Standorten, die unterschiedlich weit von Bienenständen entfernt lagen, und setzten diese Werte in Bezug zu den Besuchsraten von Honigbienen, Hummeln (Bombus terrestris) und sonstigen Bestäubern. An den gleichen Standorten bestimmten wir die Blütendichte und setzten Farbschalen ein, um die Wildbienengemeinschaft zu erfassen. Die Nutzung der Blüt enressou wurde weitgehend durch die Besuchsraten der Honigbiene erklärt und in geringfügigem Maße durch Hummelbesuch. Nach Berücksichtigung der Blütendichte wiesen Standorte in der Nähe von Bienenständen eine geringere Wildbienen-Biomasse auf. Dies war auf eine geringere Abundanz der großen Wildbienenarten zurückzuführen, also der Arten, die wahrscheinlich durch die Konkurrenz der Honigbiene beeinträchtigt werden. Wir schließen, dass Honigbienen den größten Beitrag zum Pollen- bzw. Nektarverbrauch bei den beiden wichtigsten Blütenpflanzen des Gebietes leisten und dass die Wildbienengemeinschaft bei den gegenwärtigen Honigbienendichten im Park (3.5 Völker/km2) beeinflusst wird. Unsere Untersuchung unterstützt die Hypothese, dass hohe Honigbienendichten durch Konkurrenz um Blütenressourcen einen Einfluss auf andere Bestäuber haben könnten.

Aim In the Mediterranean Basin, the main forest communities vary in their ability to recover after fire. In this study we analyse the effects of fire on ant communities occurring in various vegetation types distributed along a geographical gradient in the western Mediterranean region. Location The study was carried out in burned and unburned habitats of 22 sites corresponding to eight vegetation types distributed along a gradient of dryness throughout Catalonia (north-east Spain). Methods We placed five pairs of plots (one plot located in the burned area and the second one placed in the unburned margin) per site. We compared ant communities in these unburned and burned plot types 8 years after fire using pitfall traps. Traps were set out in mid-May and mid-July. We analysed the structure and composition of ant communities in the burned and unburned areas of these vegetation types using anova tests, correspondence analysis (CA) and linear regression. Results The resilience of ant communities varies with vegetation type. Ant communities in forests with high resilience also recover rapidly after fire, while those in forests that do not recover after fire show the lowest resilience. Species richness does not depend on burning or vegetation type. The resilience of these Mediterranean ant communities to fire is related to the environmental characteristics of the region where they live. Accordingly, differences between burned and unburned habitats are smaller for ant communities in areas with higher water deficit in summer than for those in moister ones. Main conclusions The structure and composition of ant communities after fire depends on the level of direct mortality caused by the fire. It affects ant species differently, as determined by the habitats used for nesting and foraging. The reestablishment of vegetation cover depends on forest composition before the fire. As vegetation cover determines resource and microhabitat availability and competitive relationships among species, forest composition before the fire also affects post-fire recovery of ant communities to the medium-term. Finally, ant communities living in drier areas recover more quickly after fire than those living in moister ones. This pattern might be because in areas with higher water deficit there are more species characteristic of open environments, which are habitats similar to those generated after fire.

This study analyzes the variations in the structure and composition of ant communities in burned Pinus nigra forests in central Catalonia (NE Spain). Pinus nigra forests do not recover after fire, changing to shrublands and oak coppices. For this reason, we suggest that ant communities of burned P. nigra forests will change after fire, because the post-fire scenario, in particular with the increase of open areas, is different to the unburned one, and more favourable for some species than for others. In four locations previously occupied by P. nigra forests where different fires occurred 1, 5, 13 and 19 yr before the sampling, we sampled the structure and composition of ant communities with pitfall traps, tree traps and net sweeping in unburned plots and in plots affected by canopy and understory fire. The results obtained suggest that canopy and understory fire had little effect on the structure of ant communities. Thus, many variables concerning ant communities were not modified either by fire type (understory or canopy fire) or by time since fire. However, a number of particular species were affected, either positively or negatively, by canopy fire: three species characteristic of forest habitats decreased after fire, while eight species characteristic of open habitats increased in areas affected by canopy fire, especially in the first few years after fire. These differences in ant community composition between burned and unburned plots imply that the maximum richness is achieved when there is a mixture of unburned forests and areas burned with canopy fire. Moreover, as canopy cover in P. nigra forests burned with canopy fire is not completed in the period of time studied, the presence of the species that are characteristic of burned areas remains along the chronosequence studied, while the species that disappear after fire do not recover in the period of time considered. Overall, the results obtained indicate that there is a persistent replacement of ant species in burned P. nigra forests, as is also the case with vegetation.

Quercus ilex and Pinus halepensis are two of the most common tree species of the western Mediterranean basin. Both species regenerate reliably after fire: P. halepensis colonizes recently disturbed areas by effective seedling recruitment, while Q. ilex resprouts vigorously after disturbances. For this reason, the natural regeneration of these species after fire should ensure the re-establishment of a forest similar to that which existed before the fire. This study analyzes with a simple simulation model whether or not the relative abundance of monospecific and mixed forests of these species in the landscape is altered by fire. We also analyze the topographic factors and the forest structure before the fire that determine the changes in forest composition after fire. This study has been carried out in a large fire that occurred in NE Spain. Overall, 33% of plots changed to another community type, but this probability of change varied considerably among community types before the fire. Monospecific forests of P. halepensis or Q. ilex had a high probability of remaining in their original composition after the fire, whereas the resilience of mixed forests of these two species was quite low. Mixed forests changed for the most part to monospecific P. halepensis or Q. ilex forests. Analysis of several factors determining these changes indicated that only elevation as a significant topographical variable. The effect of fire was to increase the altitudinal differentiation between the two species. P. halepensis forests that changed to mixed or Q. ilex forests were those of highest elevation, while the mixed and Q. ilex plots that changed to P. halepensis forests were those located at the lowest elevations. Concerning structural variables before fire, density of Q. ilex trees before the fire showed a much greater effect than P. halepensis density in determining the post-fire community. Finally, burn severity also influenced the changes observed. For both P. halepensis and Q. ilex forests, plots that changed to another forest type were mainly those that burned more severely. In the case of mixed forests, even low fire severities involved high probabilities of change to monospecific forests.

Ants have been traditionally considered either as predators or dispersers of seeds, but not both. That is, ant dispersal is restricted to myrmecochorous seeds, while almost all seeds removed by seed-harvesting ants are eaten. However, harvesting ants might be simultaneously antagonistic and mutualistic towards seeds. This study analyzes the predation dispersal relationship between seed-harvesting ants and seeds of Lobularia maritima, a non-myrmechorous perennial herb, in order to disentangle the dual role of ants as dispersers and predators of L. maritima seeds. The results obtained confirm the role of harvesting ants as both predators and dispersers of the non-myrmechorous seeds of L. maritima. The removal activity of Messor bouvieri on L. maritima seeds is very important, particularly in autumn, which is the flowering and fruiting peak of this plant. It can be estimated that harvesting ants collect more than 85% of seeds, and almost 70% of them are effectively lost to predation. However, these granivorous ants also have drawbacks as seed dispersers. There is a relatively small percent of seeds collected by ants that escape predation, either because they are dropped on the way to the nest (16.4% of seeds harvested), or because they are mistakenly rejected on the refuse pile (0.9%). Abiotic dispersal of L. maritima seeds in the absence of ants occurs over very short distances from the plant stem. As seeds dispersed by ants reach a considerably greater distance than that obtained by gravity, this might represent a real advantage for the species, because it reduces intraspecific adult competition for seedlings, which directly influences seedling survivorship. These results challenge the generalization that seed removal by ants generally leads to successful seed dispersal if done by legitimate seed dispensers, or seed loss if done by seed consumers that eat them, and confirm that harvesting ants might have a dual role as both predators and dispersers of nonmyrmechorous seeds.

We compare here the bulk deposition, throughfall and stemflow fluxes of dissolved trace metals in two holm oak ( Quercus ilex L.) forests in the Montseny Mountains (NE Spain) with the aim of: (1) applying different methods to distinguish between dry deposition and canopy leaching and (2) to add to the almost non-existing deposition measurements for dissolved Cu, Pb, Mn, V, Zn, Ni and Cd in two Spanish forests differentially exposed to the urban and industrial environment. No significant differences in mean bulk deposition concentrations or fluxes were found between sites, indicating little differential effect of the urban/industrial environment on bulk precipitation chemistry. At both sites, throughfall and stemflow fluxes increased relative to bulk deposition for all elements, except for Zn and Cd. The relative contribution of leaching and dry deposition was evaluated through: (1) the seasonal variability of throughfall, (2) regressions of element fluxes on water flux in net throughfall, (3) washing branches and metacrylate plates, and (4) the sequential washing of branches. Results indicated that leaching was the main enrichment process for Mn. For Ni, except the sequential washings, all other evidences also pointed to leaching. For Cu, Pb, Zn, Cd and V there was ample evidence for dry deposition. The fact that Zn and Cd had negative net throughfall fluxes indicated that canopy uptake was greater than deposition (wet plus dry). Net throughfall fluxes pointed to higher dry deposition onto the canopies in the more exposed site, but the occurrence of uptake impeached quantification. Therefore, dry deposition was estimated from the recovered quantities from experimental washings of foliage, taken to represent the impaction of small particles onto the canopy. The foliage-wash fluxes were, for Zn, Cu and Pb, respectively, 407, 25 and 16 g ha −1 yr −1 at the sheltered site and 423, 38 and 26 g ha −1 yr −1 at the exposed site. Deposition in bulk precipitation (wet deposition+an unknown fraction of dry deposition mostly accounted by coarse particles settling gravitationally) was lower: 222, 6.3 and 6.5 g ha −1 yr −1 for Zn, Cu and Pb, respectively, averaged for the two sites.

Trace metal deposition in precipitation was not significantly different in two holm oak forests with contrasted exposure to pollution in the area around Barcelona (Northeastern Spain), but dry deposition was higher at the more exposed site. Rain events of European origin had higher concentrations of Cu, Pb, Zn and Cd than those from African, Atlantic Ocean and Local provenances. Estimated from the recovered quantities in artificial plates, dry deposition was, for Zn, Cu and Pb: 342, 25 and 20 g ha -1 yr -1 , respectively at the exposed site, and 254, 13 and 15 g ha -1 yr -1 at the sheltered one. Deposition in bulk precipitation was lower than dry deposition: 221, 6. 2 and 6.4 g ha -1 yr -1 for Zn, Cu and Pb, respectively (average of the two sties).

The fluxes recovered from washing branches and surrogatesurfaces were compared for two holm oak (Quercus ilex L.)forests in the Montseny mountains (NE Spain) differentiallyexposed to pollution. For 5 periods in May and June 1996 afterexposures ranging between 68–189 hr, 6 metacrylate plates and 8branches were extracted with distilled water. Also, a sequentialwashing of branches was undertaken, with 5 min separationsbetween the 3 initial washes, one hour between the 3rd and the4th, and 6 hr between the 4th and the last one. The compositionwas analysed for PO4 3-, SO4 2-,NO3 -, Cl, F, NH4 +,Ca2+, Mg2+, Na+, K+, Cu, Pb, Mn, Co, Ni and Zn. The applied techniques were consistent in that dry deposition would accountfor the throughfall fluxes of NO3 -, Cl-,Cu and Zn. Potassium and Mn would derive mostly from leaching and their fluxes were strongly related with the holm oak flower growth. ForMg2+ and SO4 2- either leaching or impaction of small particles or gases (for SO4 2-) could account forthe recovered fluxes. Also for Na+ and Ca2+ the experiments did not produce conclusive results. Ammonium, F, Pb,Co, and Na were under the detection limit of analyticaltechniques in the plate-wash. The exposed site presented higherleaf-wash and plate-wash fluxes for all elements. This wasattributed to its higher exposure to pollutants, and forleaching-derived elements, to its higher site fertility.

International audience; & Context In the Mediterranean area, different post-fire man-agement strategies are used for coppices of resprouting spe-cies to promote a more regular forest structure, enhance plant growth, and reduce fire risk. However, the effects of these management treatments on forest-associated fauna are un-known, which in turn could be limiting their beneficial effects. & Aims The aim of this work was to determine whether forest management of a recently burned area dominated by a vigor-ous resprouting tree species (Arbutus unedo L.) affects ant communities. & Methods Ant communities, sampled using pitfall traps, were examined from unmanaged and selective thinning cop-pices of A. unedo. Ants are here used as bioindicators of ecosystem health and surrogates for other animal groups. & Results Very limited effects of these post-fire management strategies on the structure and composition of ant communities were found. The lack of effects could be due to the reported small changes in physical conditions among treatments; or either, the most sensitive ant species to these post-fire man-agement treatments might be the same ones affected by fire and, consequently, the ant species that would potentially be affected most were no longer in the study area. & Conclusion The lack of any significant effects caused by these post-fire management practices on the associated fauna of A. unedo coppices points out the suitability of these treat-ments in these circumstances.