Retana J, Arnan X, Arianoutsou M, Barbati A, Kazanis D, Rodrigo A (2011) Post-fire Management of non-serotinous pine forests. In: Post-fire management and restoration of southern European forests (Moreira F, Arianoutsou M, Corona P & De las Heras J eds). Managing Forest Ecosystems Series, Vol. 24. Springer, pp. 329. ISBN 978-94-007-2207-1.
Arnan X., Retana J., Rodrigo A., Cerdá X. (2010) Foraging behaviour of harvesting ants determines seed removal and dispersal. Insectes Sociaux. 57: 421-430.EnllaçDoi: 10.1007/s00040-010-0100-7
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).
Arnan X., Rodrigo A., Molowny-Horas R., Retana J. (2010) Ant-mediated expansion of an obligate seeder species during the first years after fire. Plant Biology. 12: 842-852.EnllaçDoi: 10.1111/j.1438-8677.2009.00294.x
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. © 2009 German Botanical Society and The Royal Botanical Society of the Netherlands.
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.EnllaçDoi: 10.1111/j.2006.0906-7590.04796.x
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.
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.EnllaçDoi: 10.1658/1100-9233(2007)18[111:PROMPC]2.0.CO;2
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.
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.EnllaçDoi: 10.1111/j.1365-2699.2006.01506.x
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.
Boet O, Arnan X, Rodrigo A (2003) Efectes dels incendis forestals sobre les comunitats de formigues. Monografies del Montseny 18:145-161.
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