Muñoz A., Bonal R., Espelta J.M. (2012) Responses of a scatter-hoarding rodent to seed morphology: Links between seed choices and seed variability. Animal Behaviour. 84: 1435-1442.LinkDoi: 10.1016/j.anbehav.2012.09.011
Seed preferences of scatter-hoarding granivores may influence the evolution of seed traits in plants. However, there is little evidence linking the granivores' responses to specific seed traits to the variability of seeds in a single plant species. This information is essential for understanding how the decisions of granivores can shape plant life histories. We analysed how seed morphology (size and shape) of the Holm oak, Quercus ilex, influences seed choices of the seed-disperser, the Algerian mouse, Mus spretus. We studied the seed variability of the oak and whether the frequency of seed phenotypes matched the seed choices of the disperser. The probabilities of seed removal decreased as the seeds became larger and more bullet-shaped, so that seeds that were simultaneously large and bullet-shaped had the lowest probabilities of being dispersed. These seeds are probably refused by rodents because they impose higher handling and transport costs. The size and shape of the Holm oak seeds were highly variable between trees, but extraordinarily consistent within a single tree over different years. However, the analysis of seed variability revealed a disproportionately low frequency of large bullet-shaped phenotypes, which are those barely removed by rodents. Seed preferences of dispersers of species with high seed variability between trees can lead to differences in the chances of seeds produced by different trees being dispersed. Those seed phenotypes preferred by dispersers could make a higher contribution to the next generation, which could influence the evolution and variability of seeds in a plant species. © 2012 The Association for the Study of Animal Behaviour.
Ortiz O., Ojeda G., Espelta J.M., Alcañiz J.M. (2012) Improving substrate fertility to enhance growth and reproductive ability of a Pinus halepensis Mill. afforestation in a restored limestone quarry. New Forests. 43: 365-381.LinkDoi: 10.1007/s11056-011-9286-4
We have evaluated the effects of improving substrate fertility on the growth and reproduction of a P. halepensis plantation in a restored limestone quarry on a stony calcareous regolith (R plots). The natural substrate was supplemented by adding a 0.2 m layer of a fine textured soil (RS plots) or a sewage sludge amended soil (RSS plots). The treatments were performed when the pines were 7 years old, and tree growth (height and trunk and canopy diameter) was monitored over the subsequent 12 years. The reproductive status of the trees was also measured when the pines were 20 years old. Tree growth was proportional to the amount of soil nutrients: 12 years after treatment the mean height of the R, RS and RSS trees was 1.5, 3.1 and 6.2 m respectively and growth increases over the baseline were 76, 264 and 632%. The treatment also affected the age of onset of reproduction (15, 11 and 9 years, respectively), the average number of cones per tree (12, 43 and 61), and the amount of seeds per cone (37, 52 and 72), but did not modify the germination percentage of pine seeds (ca 71.5%). Soil organic carbon increased proportionally to the vegetation development, contributing to carbon sequestration. These results suggest that improving the nutritional status of the soil not only improves the growth of trees, but it also ameliorates their reproductive ability (earlier reproduction onset and larger seed crop size). Implications for soil restoration through afforestation are also discussed. © 2011 Springer Science+Business Media B.V.
Navàs F, Rosell C, Fernández-Bou M, Sunyer P, Muñoz A, Espelta JM, Ániz M (2012) Efectos del jabalí en los hábitats alpinos del Parque Nacional de Aigüestortes i Estany de Sant Maurici. III REUNIÓN SOBRE UNGULADOS SILVESTRES IBÉRICOS Gerona. (comunicación oral).
Andrés P, Tarrasón D, Ravera F, Espelta JM, López K, Urrutia, JT, Rocha J (2012) La construcción de conocimiento complejo para la restauración de territorios económica y ambientalmente degradados. Un caso de aplicación a áreas ganaderas del trópico seco. (Ponencia por invitación) En: Simposio Internacional de Restauración Ecológica. Retos y Estrategias de Restauración en el Caribe Colombiano. Universidad del Atlántico. Barranquilla (Colombia). 25-27 de julio de 2012.
Puerta-Piñero C., Espelta J.M., Sánchez-Humanes B., Rodrigo A., Coll L., Brotons L. (2012) History matters: Previous land use changes determine post-fire vegetation recovery in forested Mediterranean landscapes. Forest Ecology and Management. 279: 121-127.LinkDoi: 10.1016/j.foreco.2012.05.020
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. © 2012 Elsevier Ltd.
Andrés P., Salgado C., Espelta J.M. (2011) Optimizing nursery and plantation methods to grow Cedrela odorata seedlings in tropical dry agroecosystems. Agroforestry Systems. 83: 225-234.LinkDoi: 10.1007/s10457-011-9404-5
Cedrela odorata (Spanish cedar) is a valuable multi-purpose tree which Central American rural communities and farmers give priority to introducing in pastures and home gardens. In order to propose realistic methods for C. odorata production in local nurseries in the dry tropical region of Nicaragua, we studied: (a) the ability of locally collected C. odorata seeds to germinate, (b) seed response to storage under ambient conditions or under cold storage, (c) the effects of irradiance and watering during cultivation on seedling morphology and post-transplantation survival, and (d) the effects of competition from grasses on C. odorata seedlings transplanted to pastures. Seed germination ranged from 55 to 66% and remained constant after 6 months of storage under ambient conditions or cold storage. C. odorata seedling morphology was sensitive to irradiation and watering in the nursery growing period. Deep shade reduced seedling biomass and leafiness and increased specific leaf area and root-to-shoot ratio. Water shortage increased root mass ratio and root-to-shoot ratio and decreased leaf mass ratio. Post-transplantation success was favored by weeding, and was the highest for seedlings grown under deep shade and water restrictions. © 2011 Springer Science+Business Media B.V.
Bonal R., Espelta J.M., Vogler A.P. (2011) Complex selection on life-history traits and the maintenance of variation in exaggerated rostrum length in acorn weevils. Oecologia. 167: 1053-1061.LinkDoi: 10.1007/s00442-011-2036-7
Trophic interactions can trigger the development of exaggerated specialized characters and promote morphological diversification. For example, acorn weevils (genus Curculio) present strikingly long rostrums, which are used by females to perforate oviposition holes through the seed coat. Species exhibiting longer rostrums are known to exploit larger acorns, and therefore rostrum length is thought to be subject to selection to match the preferred acorn type. However, rostrum length is strongly correlated with body size, and morphological divergence could result from either selection on rostrum length for optimal food exploitation or from other pressures acting on body size. We collected infested acorns at oak forests where the large Curculio elephas and the small-bodied Curculio glandium co-occur. There were no interspecific differences in adult female body size to rostrum length allometric relationships, and rostrum length is equally correlated with body size in either species. MtDNA-based species identification showed that C. glandium larvae were present within acorns of all sizes, whereas C. elephas larvae were restricted to acorns above a minimum size, irrespective of oak species. Hence, exploitation of large acorns can hardly have triggered rostrum enlargement, as the small sized C. glandium adults (with short rostrums) could perforate and oviposit in both small and large acorns. Rather, increased rostrum length is probably a by-product of the larger body sizes of individuals emerging from bigger acorns, which allow increased larval size and enhance larval survival likelihood. Summarizing, when exaggerated feeding traits co-vary with other body features, interspecific morphological variability may result from contrasting selective pressures acting on these correlated characters. © 2011 Springer-Verlag.
Espelta J.M., Arnan X., Rodrigo A. (2011) Non-fire induced seed release ina weakly serotinous pine: Climatic factors, maintenance costs or both?. Oikos. 120: 1752-1760.LinkDoi: 10.1111/j.1600-0706.2011.19570.x
The advantages of canopy seed retention (serotiny) for plants inhabiting fire-prone ecosystems are well documented. However, very few species are completely serotinous and non-fire induced opening of serotinous fruits is commonly observed (weak serotiny). Two non-mutually exclusive causes are envisaged to contribute to this process: mechanical changes in serotinous fruits mediated by climatic conditions (e.g. drought) or the costs of maintenance for the plant of these long-lasting structures. However, their relative contribution to the spontaneous opening of serotinous fruits remains elusive as well as the consequences for the build-up of the canopy seed bank and inter-individual differences in serotiny. In this study we monitored the dynamics of cone production and cone opening in the weakly serotinous Pinus halepensis for five years (2004-2008), including two severe drought episodes (2005, 2006). Drought decreased the production of conelets, increased the abortion of immature cones, reduced the seed quality in the cohorts of cones produced during these years, and increased the opening of serotinous cones. During the first drought episode, a higher proportion of serotinous cones opened in those pines bearing a larger crop of younger cones. This suggests that not only passive changes induced by drought but also competition among cones for resources (e.g. water) might be involved in this process. The opening of serotinous cones in pines bearing more cones made inter-individual differences in the size of the canopy cone bank to narrow or even to reverse from 2004 to 2008. These results may help to understand the decrease in serotiny when pines grow and accumulate more cones and the large inter-individual variability in the degree of serotiny observed in P. halepensis forests. In addition, the negative effects of drought episodes for the size of the canopy cone bank and the seeds contained can be an unexplored cause of post-fire regeneration constraint. © 2011 The Authors.
Espelta JM (2011) Forest Fires.at the crossroad between devastation and landscape improvement. PAISEA 16: 101-105.
Peguero G., Espelta J.M. (2011) Disturbance intensity and seasonality affect the resprouting ability of the neotropical dry-forest tree Acacia pennatula: Do resources stored below-ground matter?. Journal of Tropical Ecology. 27: 539-546.LinkDoi: 10.1017/S0266467411000290
Many plant species in tropical dry forests partly base their ability to persist after disturbance on resprouting. Yet little is known if this ability can be affected by the intensity and seasonality of disturbance and whether the amount of resources (starch, N, P) stored in the taproot may constrain this response. We investigated resprouting after experimental clipping or burning, applied before or after the dry season and repeatedly in Acacia pennatula individuals in wooded rangelands of North-West Nicaragua. Each treatment was applied to 12 trees and replicated in six plots. One year after the onset of the experiment, survival and biomass recovery were significantly lower in burned than in clipped individuals (78% ± 4% and 75.3 ± 8.0 g vs. 94% ± 2% and 79.1 ± 6.8 g; mean ± SE). Whatever the disturbance applied, trees disturbed after the dry season significantly showed the lowest survival, growth and concentration of N and P. These results suggest that resprouting in dry tropical species may be constrained by intense disturbances (e.g. burning) but especially if they occur towards the end of the dry season. This phenological constraint could be due to the reduced availability of N and P as this dry season progresses. © 2011 Cambridge University Press.
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