Les pinedes de pi blanc. En: Manuals de gestió d’hàbitats.

Arnan X, Gràcia M, Molowny Horas R, Ordoñez JL, Retana J et al. (2010) Les pinedes de pi blanc. En: Manuals de gestió d’hàbitats. Diputació de Barcelona.

Forest management conditioning ground ant community structure and composition in temperate conifer forests in the Pyrenees Mountains

Arnan X., Gracia M., Comas L., Retana J. (2009) Forest management conditioning ground ant community structure and composition in temperate conifer forests in the Pyrenees Mountains. Forest Ecology and Management. 258: 51-59.
Enllaç
Doi: 10.1016/j.foreco.2009.03.029

Resum:

The search for indicators to monitor management impact on biodiversity is a crucial question because management practices promote changes in community structure and composition of different animal groups. This study explores the effect of widely conducted management practices (forest logging and livestock) in Pinus uncinata forests in the Pyrenees range (NE Spain) on the structure and composition of ground ant communities compared to those of old-growth stands. Forest structure clearly differed in stands with different forest managements. These stands managed for different uses also showed marked differences in structure and composition of ground ant communities. There was a great dominance of a single species, Formica lugubris, which accounted for 99% of ants collected in pitfall traps. Rarefaction curves indicated that species richness was highest in old-growth stands and lowest in even-aged ones, with woodland pasture stands showing an intermediate value. Classification methods allowed us to identify two groups of species: six species related to old-growth plots and three species (including F. lugubris) associated to managed stands. Habitat structure played an important role in determining the structure of ant communities: forests with high tree density but low basal area were the most favourable forest type for F. lugubris, while the abundance of the remaining ant species was negatively affected by the abundance of F. lugubris and by tree cover. © 2009.

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L’edat de les oliveres monumentals i singulars del Montsià.

Martínez-Vilalta J, Claramunt B, Arnan X, Estorach M, Poyatos R (2009) L’edat de les oliveres monumentals i singulars del Montsià. Raïls 25: 208-221.

Climatic drivers of hemispheric asymmetry in global patterns of ant species richness

Dunn R.R., Agosti D., Andersen A.N., Arnan X., Bruhl C.A., Cerdá X., Ellison A.M., Fisher B.L., Fitzpatrick M.C., Gibb H., Gotelli N.J., Gove A.D., Guenard B., Janda M., Kaspari M., Laurent E.J., Lessard J.-P., Longino J.T., Majer J.D., Menke S.B., McGlynn T.P., Parr C.L., Philpott S.M., Pfeiffer M., Retana J., Suarez A.V., Vasconcelos H.L., Weiser M.D., Sanders N.J. (2009) Climatic drivers of hemispheric asymmetry in global patterns of ant species richness. Ecology Letters. 12: 324-333.
Enllaç
Doi: 10.1111/j.1461-0248.2009.01291.x

Resum:

Although many taxa show a latitudinal gradient in richness, the relationship between latitude and species richness is often asymmetrical between the northern and southern hemispheres. Here we examine the latitudinal pattern of species richness across 1003 local ant assemblages. We find latitudinal asymmetry, with southern hemisphere sites being more diverse than northern hemisphere sites. Most of this asymmetry could be explained statistically by differences in contemporary climate. Local ant species richness was positively associated with temperature, but negatively (although weakly) associated with temperature range and precipitation. After contemporary climate was accounted for, a modest difference in diversity between hemispheres persisted, suggesting that factors other than contemporary climate contributed to the hemispherical asymmetry. The most parsimonious explanation for this remaining asymmetry is that greater climate change since the Eocene in the northern than in the southern hemisphere has led to more extinctions in the northern hemisphere with consequent effects on local ant species richness. © 2009 Blackwell Publishing Ltd/CNRS.

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Avaluació ecològica de diferents tractaments silvícoles de millora de la regeneració natural en zones afectades per incendi i sequeres extremes. En: Models silvícoles en boscos privats mediterranis.

Espelta JM, Arnan X, Verkaik I, Guitart L (2008) Avaluació ecològica de diferents tractaments silvícoles de millora de la regeneració natural en zones afectades per incendi i sequeres extremes. En: Models silvícoles en boscos privats mediterranis. Col.lecció: Documents de Treball, Serie Territori 5:153-181. Diputació de Barcelona.

Uncoupling the effects of shade and food resources of vegetation on Mediterranean ants: An experimental approach at the community level

Arnan X., Rodrigo A., Retana J. (2007) Uncoupling the effects of shade and food resources of vegetation on Mediterranean ants: An experimental approach at the community level. Ecography. 30: 161-172.
Enllaç
Doi: 10.1111/j.2006.0906-7590.04796.x

Resum:

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. Copyright © Ecography 2007.

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Post-fire regeneration of Mediterranean plant communities at a regional scale is dependent on vegetation type and dryness

Arnan X., Rodrigo A., Retana J. (2007) Post-fire regeneration of Mediterranean plant communities at a regional scale is dependent on vegetation type and dryness. Journal of Vegetation Science. 18: 111-122.
Enllaç
Doi: 10.1658/1100-9233(2007)18[111:PROMPC]2.0.CO;2

Resum:

Question: We tested whether (1) the change in composition and structure of whole plant communities after fire is directly related to regeneration of the dominant tree species in the canopy; (2) the change in structure and composition of plant communities several years after fire decreases with the proportion of obligate seeders and (3) the proportion of obligate seeders in plant communities increases with the dryness gradient. Location: Catalonia (NE Spain). Methods: We measured floristic differences between burned and long-since burned sites in eight vegetation types across a climate gradient. We compared 22 sites burnt in 1994 in paired plots with 22 sites that had not been burnt since the 1940s. In each site we placed plots in burned and long-since burned areas, where we identified the presence and abundance of all plant species. Results: When the tree canopy recovers, structure and composition of the vegetation also return to the long-since burned community; when tree canopy does not recover, composition of the post-fire community varies compared to the long-since burned one. A higher proportion of obligate seeders in the pre-fire community promotes quicker regeneration of the original community. The proportion of obligate seeders increased along the dryness gradient. Conclusions: Regeneration of plant communities after fire depends on the vegetation type before the fire. Regeneration increases when the dominant tree or shrub species persists after fire and with a higher proportion of obligate seeders in the pre-fire community. The proportion of obligate seeders varies along the dryness gradient, which suggests that vegetation in drier areas (when seeders are more abundant) recovers earlier than in moister areas. © IAVS; Opulus Press.

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Post-fire recovery of Mediterranean ground ant communities follows vegetation and dryness gradients

Arnan X., Rodrigo A., Retana J. (2006) Post-fire recovery of Mediterranean ground ant communities follows vegetation and dryness gradients. Journal of Biogeography. 33: 1246-1258.
Enllaç
Doi: 10.1111/j.1365-2699.2006.01506.x

Resum:

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. © 2006 The Authors.

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Efectes dels incendis forestals sobre les comunitats de formigues.

Boet O, Arnan X, Rodrigo A (2003) Efectes dels incendis forestals sobre les comunitats de formigues. Monografies del Montseny 18:145-161.

Ant functional responses along environmental gradients

Arnan X., Cerda X., Retana J. (0) Ant functional responses along environmental gradients. Journal of Animal Ecology. 83: 1398-1408.
Enllaç
Doi: 10.1111/1365-2656.12227

Resum:

Understanding species distributions and diversity gradients is a central challenge in ecology and requires prior knowledge of the functional traits mediating species' survival under particular environmental conditions. While the functional ecology of plants has been reasonably well explored, much less is known about that of animals. Ants are among the most diverse, abundant and ecologically significant organisms on earth, and they perform a great variety of ecological functions. In this study, we analyse how the functional species traits present in ant communities vary along broad gradients in climate, productivity and vegetation type in the south-western Mediterranean. To this end, we compiled one of the largest animal databases to date: it contains information on 211 local ant communities (including eight climate variables, productivity, and vegetation type) and 124 ant species, for which 10 functional traits are described. We used traits that characterize different dimensions of the ant functional niche with respect to morphology, life history and behaviour at both individual and colony level. We calculated two complementary functional trait community indices ('trait average' and 'trait dissimilarity') for each trait, and we analysed how they varied along the three different gradients using generalized least squares models that accounted for spatial autocorrelation. Our results show that productivity, vegetation type and, to a lesser extent, each climate variable per se might play an important role in shaping the occurrence of functional species traits in ant communities. Among the climate variables, temperature and precipitation seasonality had a much higher influence on functional responses than their mean values, whose effects were almost lacking. Our results suggest that strong relationships might exist between the abiotic environment and the distribution of functional traits among south-western Mediterranean ant communities. This finding indicates that functional traits may modulate the responses of ant species to the environment. Since these traits act as the link between species distributions and the environment, they could potentially be used to predict community changes under future global change scenarios.

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