A review of the combination among global change factors in forests, shrublands and pastures of the Mediterranean Region: Beyond drought effects

Doblas-Miranda, E., Alonso, R., Arnan, X., Bermejo, V., Brotons, L., de las Heras, J., Estiarte, M., Hódar, J.A., Llorens, P., Lloret, F., López-Serrano, F.R., Martínez-Vilalta, J., Moya, D., Peñuelas, J., Pino, J., Rodrigo, A., Roura-Pascual, N., Valladares, F., Vilà, M., Zamora, R., Retana, J. (2017) A review of the combination among global change factors in forests, shrublands and pastures of the Mediterranean Region: Beyond drought effects. Global and Planetary Change. 148: 42-54.
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Doi: 10.1016/j.gloplacha.2016.11.012

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Response of ant functional composition to fire

Arnan X., Cerda X., Rodrigo A., Retana J. (2013) Response of ant functional composition to fire. Ecography. 36: 1182-1192.
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Doi: 10.1111/j.1600-0587.2013.00155.x

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Little is known about the impact of disturbances on functional diversity and the long-term provisioning of ecosystem services, especially in animals. In this work we analyze the effect of wildfire on the functional composition of Mediterranean ant communities. In particular, we asked whether a) fire changes functional composition (mean and dissimilarity of trait values) at the community level; and b) such fire-induced functional modification is driven by changes in the relative abundance-dominance of species or by a replacement of species with different traits. We sampled ant communities in burned and unburned plots along 22 sites in a western Mediterranean region, and we computed two complementary functional trait composition indices ('trait average' and 'trait dissimilarity') for 12 functional traits (related to resource exploitation, social structure and reproduction) and with two different datasets varying in the way species abundance is considered (i.e. abundance and occurrence data). Our results suggest a set of functional responses that seem to be related to direct mortality by fire as well as to indirect fire-induced modifications in environmental conditions relevant for ants. Trait average of colony size, worker size, worker polymorphism and the ratio between queen and worker size, as well as the trait dissimilarity of the proportion of behaviorally dominant species and of liquid food consumption, and overall functional diversity, were higher in burned than in unburned areas. Interestingly, different patterns arise when comparing results from abundance and occurrence data. While the response to fire in trait averages is quite similar, in the case of trait dissimilarity, the higher values in response to fire are much more marked when considering occurrence rather than abundance data. Our results suggest that changes in trait average are driven at the same time by replacement of species with different traits and by changes in the relative abundance-dominance of species, while fire promotes a higher diversity of functions that is primarily driven by rare species that are functionally unique. Overall, we observed major fire-induced changes in functional composition in Mediterranean ant communities that might have relevant consequences for ecosystem processes and services. © 2013 The Authors.

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Post-fire invasion and subsequent extinction of Conyza spp. in Mediterranean forests is mostly explained by local factors

Pino J., Arnan X., Rodrigo A., Retana J. (2013) Post-fire invasion and subsequent extinction of Conyza spp. in Mediterranean forests is mostly explained by local factors. Weed Research. 53: 470-478.
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Doi: 10.1111/wre.12040

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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. © 2013 European Weed Research Society.

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Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics

Arnan X., Molowny-Horas R., Rodrigo A., Retana J. (2012) Uncoupling the effects of seed predation and seed dispersal by granivorous ants on plant population dynamics. PLoS ONE. 7: 0-0.
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Doi: 10.1371/journal.pone.0042869

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Secondary seed dispersal is an important plant-animal interaction, which is central to understanding plant population and community dynamics. Very little information is still available on the effects of dispersal on plant demography and, particularly, for ant-seed dispersal interactions. As many other interactions, seed dispersal by animals involves costs (seed predation) and benefits (seed dispersal), the balance of which determines the outcome of the interaction. Separate quantification of each of them is essential in order to understand the effects of this interaction. To address this issue, we have successfully separated and analyzed the costs and benefits of seed dispersal by seed-harvesting ants on the plant population dynamics of three shrub species with different traits. To that aim a stochastic, spatially-explicit individually-based simulation model has been implemented based on actual data sets. The results from our simulation model agree with theoretical models of plant response dependent on seed dispersal, for one plant species, and ant-mediated seed predation, for another one. In these cases, model predictions were close to the observed values at field. Nonetheless, these ecological processes did not affect in anyway a third species, for which the model predictions were far from the observed values. This indicates that the balance between costs and benefits associated to secondary seed dispersal is clearly related to specific traits. This study is one of the first works that analyze tradeoffs of secondary seed dispersal on plant population dynamics, by disentangling the effects of related costs and benefits. We suggest analyzing the effects of interactions on population dynamics as opposed to merely analyzing the partners and their interaction strength. © 2012 Arnan et al.

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Post-fire Management of non-serotinous pine forests.

Retana J, Arnan X, Arianoutsou M, Barbati A, Kazanis D, Rodrigo A (2012) Post-fire Management of non-serotinous pine forests. In: (Moreira F, Arianoutsou M, Corona P & De las Heras J Eds) Post-fire management and restoration of southern European forests. Managing Forest Ecosystems Series, Vol. 24. Springer. ISBN 978-94-007-2207-1. pp. 151-170.

Relevance of soil seed bank and seed rain to immediate seed supply after a large wildfire

Rodrigo A., Arnan X., Retana J. (2012) Relevance of soil seed bank and seed rain to immediate seed supply after a large wildfire. International Journal of Wildland Fire. 21: 449-458.
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Doi: 10.1071/WF11058

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We examined the density and composition of the immediate seed supply (i.e. instant potential post-fire germination from soil seed bank and off-site seed rain) after a large wildfire in a sub-Mediterranean pine forest. We also tested the effects of fire severity and distance from unburned edges on the density and composition of the seed bank and the immediate off-site seed rain. Our results showed that although seed density did not differ between them, their composition was markedly different. The soil seed bank was dominated by species from the Fabaceae family with limited dispersal mechanisms such as autochory and barochory, whereas the seed rain was mainly composed of species from the Asteraceae family with wind-dispersed seeds. These patterns were not affected either by fire severity or distance from the fire edge. The main conclusion of the study is that both the soil seed bank and the seed rain play an important role in providing seeds for immediate regeneration after a large wildfire throughout the burned area. We suggest that the role of seed rain on immediate post-fire recovery of Mediterranean plant communities might be more important than has previously been thought. However, the effective role of this group of species on the longer term should be evaluated. © IAWF 2012.

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Lack of regeneration and climatic vulnerability to fire of Scots pine may induce vegetation shifts at the southern edge of its distribution

Vilà-Cabrera A., Rodrigo A., Martínez-Vilalta J., Retana J. (2012) Lack of regeneration and climatic vulnerability to fire of Scots pine may induce vegetation shifts at the southern edge of its distribution. Journal of Biogeography. 39: 488-496.
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Doi: 10.1111/j.1365-2699.2011.02615.x

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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 31years 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 25m 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.15years. 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. © 2011 Blackwell Publishing Ltd.

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És homogènia la recuperació, després del foc, de les comunitats de plantes i de formigues dels boscos de Catalunya?

 

Rodrigo A., Arnan X., Retana J. (2011). És homogènia la recuperació, després del foc, de les comunitats de plantes i de formigues dels boscos de Catalunya?. Treballs de la Societat Catalana de Geografia, 71-72 (115-136).

What are the consequences of ant-seed interactions on the abundance of two dry-fruited shrubs in a Mediterranean scrub?

Arnan X., Rodrigo A., Retana J. (2011) What are the consequences of ant-seed interactions on the abundance of two dry-fruited shrubs in a Mediterranean scrub?. Oecologia. 167: 1027-1039.
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Doi: 10.1007/s00442-011-2034-9

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Strong interactions between dry-fruited shrubs and seed-harvesting ants are expected in early successional scrubs, where both groups have a major presence. We have analysed the implications of the seed characteristics of two dry-fruited shrub species (Coronilla minima and Dorycnium pentaphyllum) on seed predation and dispersal mediated by harvester ants and the consequences of these processes on spatio-temporal patterns of plant abundance in a heterogeneous environment. We found that large C. minima seeds were collected much more (39%) than small D. pentaphyllum seeds (2%). However, not all of the removed seeds of these plant species were consumed, and 12.8% of the seeds were lost along the trails, which increased dispersal distances compared with abiotic dispersal alone. Seed dropping occurred among all microhabitats of the two plant species, but especially in open microhabitats, which are the most suitable ones for plant establishment. The two plant species increased their presence in the study area during the study period: C. minima in open microhabitats and D. pentaphyllum in high vegetation. The large size of C. minima seeds probably limited the primary seed dispersal of this species, but may have allowed strong interaction with ants. Thus, seed dispersal by ants resulted in C. minima seeds reaching more suitable microhabitats by means of increasing dispersal distance and redistribution among microhabitats. In contrast, the smaller size of D. pentaphyllum seeds arguably allows abiotic seed dispersal over longer distances and colonization of all types of microhabitats, although it probably also limits their interaction with ants and, consequently, their redistribution in suitable microhabitats. We suggest that dyszoochory could contribute to the success of plant species with different seed characteristics in scrub habitats where seeds are abundantly collected by seed-harvesting ants. © 2011 Springer-Verlag.

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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).

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.

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