Viu la terra

Durant aquest any 2008 coincideixen un conjunt d’esdeveniments de gran importància pel que fa a augmentar el coneixement que tenim del planeta que ens suporta. En primer lloc, se celebra el cinquantenari de l’Any geofísic internacional (1957-58). En segon lloc, estem de ple dins l’Any Polar Internacional, que s’estén des del març de 2007 fins el març de 2009, per tal d’incloure dos estius i dos hiverns de cada hemisferi. I, finalment, l’Organització de les Nacions Unides ha declarat aquest any (de fet, el trienni 2007-2009) com a Any Internacional del Planeta Terra, declaració que té com a objectiu promoure el desenvolupament sostenible de la societat global mitjançant el coneixement i la divulgació de les Ciències de la terra. Aquest triple marc de fets relacionats amb el coneixement del nostre planeta justifica sobradament la programació d’aquesta exposició

Ciències de la terra i societat : la recerca en geologia aplicada

Aquest article pretén presentar les línies de treball del grup de recerca de l'Àrea de Geodinàmica Externa del Departament de Ciències Ambientals de la Facultat de Ciències de la UdG (Universitat de Girona)com a mostra dels camps d'aplicació més comuns del treball dels geòlegs

Building wood debris piles benefits avian seed dispersers in burned and logged Mediterranean pine forests

Salvage logging is a common practice carried out in burned forests worldwide, and intended to mitigate the economic losses caused by wildfires. Logging implies an additional disturbance occurring shortly after fire, although its ecological effects can be somewhat mitigated by leaving wood debris on site. The composition of the bird community and its capacity to provide ecosystem services such as seed dispersal of fleshy-fruited plants have been shown to be affected by postfire logging. We assessed the effects of the habitat structure resulting from different postfire management practices on the bird community, in three burned pine forests in Catalonia (western Mediterranean). For this purpose, we focused on the group of species that is responsible for seed dispersal, a process which takes place primarily during the winter in the Mediterranean basin. In addition, we assessed microhabitat selection by seed disperser birds in such environments in relation to management practices. Our results showed a significant, positive relationship between the density of wood debris piles and the abundance of seed disperser birds. Furthermore, such piles were the preferred microhabitat of these species. This reveals an important effect of forest management on seed disperser birds, which is likely to affect the dynamics of bird-dependent seed dispersal. Thus, building wood debris piles can be a useful practice for the conservation of both the species and their ecosystem services, while also being compatible with timber harvesting

Can salvage logging affect seed dispersal by birds into burned forests?

The recovery of vegetation in Mediterranean ecosystems after wildfire is mostly a result of direct regeneration, since the same species existing before the fire regenerate on-site by seeding or resprouting. However, the possibility of plant colonization by dispersal of seeds from unburned areas remains poorly studied. We addressed the role of the frugivorous, bird-dependent seed dispersal (seed rain) of fleshy-fruited plants in a burned and managed forest in the second winter after a fire, before on-site fruit production had begun. We also assessed the effect on seed rain of different microhabitats resulting from salvage logging (erosion barriers, standing snags, open areas), as well as the microhabitats of unlogged patches and an unburned control forest, taking account of the importance of perches as seed rain sites. We found considerable seed rain by birds in the burned area. Seeds, mostly from Olive trees Olea europaea and Evergreen pistaches Pistacia lentiscus, belonged to plants fruiting only in surrounding unburned areas. Seed rain was heterogeneous, and depended on microhabitat, with the highest seed density in the unburned control forest but closely followed by the wood piles of erosion barriers. In contrast, very low densities were found under perches of standing snags. Furthermore, frugivorous bird richness seemed to be higher in the erosion barriers than elsewhere. Our results highlight the importance of this specific post-fire management in bird-dependent seed rain and also may suggest a consequent heterogeneous distribution of fleshy-fruited plants in burned and managed areas. However, there needs to be more study of the establishment success of dispersed seeds before an accurate assessment can be made of the role of bird-mediated seed dispersal in post-fire regeneration

Morfogènesi de pilars de terra (earth Pillars, hoodoos). Exemples de la Riera de Gaià (Vallès Occidental, Barcelona) i del Bernal de Yátor (Las Alpujarras, Granada)

The origin and the primary features of the erosive earth pillar-like formations that develop in the Riera de Gaià (Barcelona) and in the Bernal de Yátor (Granada) are described. They are dynamic formations typical of areas subjected to strong water erosion