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- Selection of trees for rubbing by red and roe deer in forest plantationsPublication . Ramos, Jaime; Bugalho, Miguel; Cortez, José Paulo; Iason, GlennAntler rubbing is a form of behaviour by which deer may damage and ultimately induce mortality of trees. Understanding factors affecting selection of trees for rubbing may contribute to mitigation of negative effects of such behaviour in plantations or woodlands. We analysed characteristics of trees rubbed by red and roe deer along transects established in plantations of Pinus pinaster (Aiton), Pseudotsuga menziesii (Mirbel) Franco, Betula alba L. and Quercus robur L. in Northeast Portugal. Transects were walked during five sampling periods covering mating seasons of red and roe deer. Red deer preferentially rubbed trees adjacent to the edge of plantations and large clearings whilst roe deer selected those inside plantations within small clearings. There was seasonal segregation in the number of trees rubbed by each deer species with red deer rubbing trees mainly between September and February and roe deer mainly between December and June. Both red and roe deer selected trees with smaller diameter than those of available trees although trees selected by red deer had larger diameters than those selected by roe deer. Roe, but not red deer, tended to avoid trees protected by shrubs. Overall, the selection of trees for rubbing was site-dependent suggesting that generalizations across sites should be made with caution. Mitigating measures, such as deer control, tree protection or provision of alternative rubbing posts should target stands of particular tree species, location of trees in relation to stand clearings and tree size classes.
- Utilização e impacto dos cervídeos na vegetação lenhosaPublication . Cortez, José Paulo; Ramos, Jaime; Rego, FranciscoNo Nordeste de Portugal, o Corço (Capreolus capreolus) e o Veado (Cervus elaphus) coexistem, sendo pouco conhecido o efeito sobre as plantas mediterrânicas. Com o objectivo de avaliar a forma como estas duas espécies de cervídeos afectam a vegetação lenhosa, avaliamos: 1)a importância da componente da vegetação lenhosa na sua dieta ao longo de dois anos, 2) o efeito dos cervídeos sobre a marcação de árvores, 3) a resposta de três espécies lenhosas ao consumo por herbivoros através de um ensaio de simulação e 4) o efeito dos cervídeos na regeneração de Azinheira usando parcelas de exclusão. O Veado consumiu mais gramíneas na Primavera, em contraste com o Verão, onde as lenhosas representaram cerca de 80% da dieta. O Corço manteve, ao longo de todo o ano, um maior consumo de lenhosas e a sua dieta foi mais diversa. A distribuição das marcações de árvores no espaço florestal revelou preferência dos Veados pela orla das plantações florestais, enquanto os corços marcaram mais árvores no interior das plantações florestais. A simulação de pastoreio para avaliar a resposta de Azinheira (Quercus rotundifolia), Esteva (Cistus ladanifer) e Carqueja (Pterospartum tridentatum) ao consumo por herbivoros revelou que a Carqueja respondeu com aumento do diâmetro do sistema radicular, bem como de biomassa, a Azinheira respondeu aumentando os diâmetros de copa, enquanto a Esteva revelou uma redução da biomassa total com o pastoreio. As parcelas de exclusão de cervídeos, revelaram forte tendência para redução da mortalidade de plântulas de Azinheira no interior das parcelas.
- Rewiring of experimentally disturbed seed dispersal networks might lead to unexpected network configurationsPublication . Costa, José M.; Ramos, Jaime; Silva, Luís P. da; Timóteo, Sérgio; Andrade, Pedro; Araújo, Pedro M.; Carneiro, Camilo; Correia, Edna; Cortez, José Paulo; Felgueiras, Marcial; Godinho, Carlos; Lopes, Ricardo Jorge; Matos, Cláudia; Norte, Ana Cláudia; Pereira, Pedro F.; Rosa, António; Heleno, Ruben H.The consequences of species extinctions in ecological communities may be buffered through the rearrangement (rewiring) of the interactions between the remaining species. The structural and functional consequences of such extinctions can be explored by means of computer simulations that try to predict secondary extinctions and the degradation of ecosystem services. However, to improve the accuracy of these simulations, it is pivotal to evaluate their performance in predicting changes observed in natural communities. In this study, we first described the avian seed dispersal networks in 17 sites throughout Portugal, and found that blackberry (Rubus ulmifolius) was the most dispersed species in 13 out of the 17 sites. Second, we performed a manipulative experiment to evaluate the effect of removing the most dispersed plant species and compared the observed outcome in the structure of the network with computer simulations with and without rewiring. Observed changes were consistent with some rapid network rewiring, with dispersers shifting to alternative fruit species. Although the observed network topology after the experimental removal was not accurately predicted, the extinction simulation with rewiring performed considerably better than that without rewiring. Individual species roles were even harder to predict than emergent network properties on both types of models. We show that incorporating rewiring rules can considerably increase the accuracy of species extinction models, however, the functional consequences of losing important resources might not be easily anticipated, and rewiring might occur in unexpected directions.
- Nest-site selection by roseate terns breeding on arlde island, SeychellesPublication . Cortez, José Paulo; Patacho, Domingos; Ramos, Jaime