Percorrer por autor "Miguel, Luis"
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- Herbaceous plant diversity across fire created edges in continental holm oak woodlandsPublication . Azevedo, João; Fernández-Núñez, Esther; Miguel, Luis; Amado, Anabela; Possacos, Anabela; Aguiar, CarlosWe analyzed herbaceous plants distribution across edges of holm oak (Quercus rotundifolia) woodlands created and maintained by fire in order to describe plant community structure across edges and to evaluate the role of fire in the patterning of plant diversity at the patch scale. We recorded abundance in twelve 60 m long sampling lines placed perpendicularly to the woodlands boundary at 1, 5, 10, and 20m outside and 0, 1, 5, 10, 20, and 40m inside the woodlands, using the line intercept method (2 x 10 m line parallel to the boundary). In the same locations, we measured tree and shrub cover, height and density and recorded time since last fire disturbance. Data was analysed graphically and statistically using multivariate ordination analysis techniques, namely CCA. Results indicated that, on average, herbaceous species richness was higher outside than inside the woodlands and peaked 1m outside the boundary. Time since last fire in adjacent shrublands affected richness patterns across edges. Richness was higher outside than inside in young adjacent shurblands, higher inside than outside in old shrublands and peaked 1m outside in intermediate age shrublands, interior, exterior and edge (1m outside the boundary) species and locations were well correlated with explanatory variables reflecting the interior exterior woodland gradient sampled and shrub recovery after fire.
- The role of holm oak edges in the control of disturbance and conservation of plant diversity in fire-prone landscapesPublication . Azevedo, João; Possacos, Anabela; Aguiar, Carlos; Amado, Anabela; Miguel, Luis; Dias, Rui; Loureiro, Carlos; Fernandes, Paulo M.Holm oak (Quercus rotundifolia) woodlands have been able to persist in fire-prone landscapes in northern Portugal where they seem to play a relevant role in community and landscape level patterns and processes, namely in the control of disturbance events and in the maintenance of biodiversity. In this research we tested the following hypotheses: (i) holm oak woodlands affect fire behavior, mainly by disrupting and delaying fire spread; (ii) disruption and delaying of fire spread is due to fire extinction at the edge of woodlands; and (iii) plant diversity is favored by frequent low-intensity fires as a result of the control of fire spread by holm oak woodland edges. We sampled herbaceous, shrub and tree structure and herbaceous plant composition across edges of holm oak woodlands with known recent contact with fire. Using BehavePlus we converted structural data into fuel models and simulated fire behavior for the locations sampled along the exterior–interior gradient of the woodlands. Our results indicate that holm oak woodlands play a relevant role in the control of fire spread and in the maintenance of plant diversity. We found differences in simulated maximum rate of fire spread (ROS) and fireline intensity (FLI) between outside and inside woodlands as well as a 100% probability of fire extinction when fuel moisture was >12% and wind speed at 10 m aboveground was <40 km h 1, supporting the self-extinction hypothesis. We found also that richness and abundance of herbaceous plants varied between the interior and exterior of the woodland, with higher values outside the woodland, and that plant composition along the interior–exterior gradient had distinct patterns. These variables and the pattern of plant distribution were also significantly affected by time since last fire event. We conclude that holm oak woodlands affect fire behavior by interrupting fire spread at the edge zone and that fire-created edges affect herbaceous plant species richness, abundance and distribution by maintaining habitat diversity, which increased plant diversity at patch and landscape levels. Based on our results and other evidence, we developed a conceptual model of the dynamics of fire, landscape structure, and plant diversity in fire-prone landscapes where holm oak patches persist.