Percorrer por autor "Fernandes, Paulo M."
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- Natural establishment of Eucalyptus globulus Labill. in burnt stands in PortugalPublication . Águas, Ana; Ferreira, António; Maia, Paula; Fernandes, Paulo M.; Roxo, Luís; Keizer, Jan; Silva, Joaquim S.; Rego, Francisco C.; Moreira, FranciscoExotic tree species are increasingly common in many regions of the world and at least some species are becoming naturalized in the regions where they were introduced. Disturbances like fire may be at the origin or accelerate the naturalization of these species. Portugal holds one of the largest areas of exotic Eucalyptus globulus plantations in the world and is one of the countries most affected by forest fires. These two facts have triggered the present research. This study aimed at characterising medium-term natural establishment of E. globulus plants originated from seeds under natural conditions in burnt planted forests (pure E. globulus stands, pure Pinus pinaster stands, and mixed stands of both species), and at analysing factors associated with this establishment. Occurrence, abundance and height of naturally established E. globulus plants were characterized in 284 sites distributed in burnt areas, across Central and Northern Portugal, 5–7 years after wildfire. Generalized linear models were used to assess the influence of stand type, regional productivity potential, and post-fire management practices on occurrence probability, density, and median height of sampled E. globulus individuals. The influence of these explanatory variables on the structure (in terms of size class distribution) of naturally established E. globulus cohort was examined using analysis of similarity and non-metric multidimensional scaling. Naturally established E. globulus plants were present in 93.1%, 19.0% and 98.6% of samples in pure E. globulus, pure P. pinaster and mixed stands, respectively. Cohort median density was 0.20 plants m−2 and maximum density was 4.55 plants m−2. Median height of plants was 2.0 m and 95.3% of them had h >1.30 m and DBH ⩽5 cm. Establishment probability, density and median height were highest in the most productive regions. Three post-fire management operations had a significant influence on the response variables: (i) salvage logging was associated with a higher density; (ii) tillage was associated with a lower density and a smaller median height; (iii) understorey removal was associated with a lower occurrence probability. Tillage was the only studied factor influencing the size structure of spontaneously established cohort, eliminating larger plants. This study showed that stand type, productivity region and post-fire management operations might have significantly influenced the natural establishment of E. globulus in burnt areas, and consequently the species naturalization process in Portugal. The implications of these findings for management are discussed.
- A Near-Real-Time Operational Live Fuel Moisture Content (LFMC) Product to Support Decision-Making at the National LevelPublication . Benali, Akli; Baldassarre, Giuseppe; Loureiro, Carlos; Briquemont, Florian; Fernandes, Paulo M.; Rossa, Carlos; Figueira, RuiLive fuel moisture content (LFMC) significantly influences fire activity and behavior over different spatial and temporal scales. The ability to estimate LFMC is important to improve our capability to predict when and where large wildfires may occur. Currently, there is a gap in providing reliable near-real-time LFMC estimates which can contribute to better operational decision-making. The objective of this work was to develop near-real-time LFMC estimates for operational purposes in Portugal. We modelled LFMC using Random Forests for Portugal using a large set of potential predictor variables. We validated the model and analyzed the relationships between estimated LFMC and both fire size and behavior. The model predicted LFMC with an R2 of 0.78 and an RMSE of 12.82%, and combined six variables: drought code, day-of-year and satellite vegetation indices. The model predicted well the temporal LFMC variability across most of the sampling sites. A clear relationship between LFMC and fire size was observed: 98% of the wildfires larger than 500 ha occurred with LFMC lower than 100%. Further analysis showed that 90% of these wildfires occurred for dead and live fuel moisture content lower than 10% and 100%, respectively. Fast-spreading wildfires were coincident with lower LFMC conditions: 92% of fires with rate of spread larger than 1000 m/h occurred with LFMC lower than 100%. The availability of spatial and temporal LFMC information for Portugal will be relevant for better fire management decision-making and will allow a better understanding of the drivers of large wildfires.
- Survival of prescribed burning treatments to wildfire in PortugalPublication . Davim, David A.; Rossa, Carlos G.; Fernandes, Paulo M.Adoption of prescribed burning is increasing as the treatment chosen to decrease fuel hazard in southern Europe but little is known about how it affects wildfire activity. We assessed the effectiveness of prescribed burning treatments by analysing the survival of treatment units to wildfire in mainland Portugal (2005–2017). We examined the time-dependency of treatment-wildfire encounters through survival analysis, and evaluated treatment effectiveness as the intersection outcome in terms of the unburned fraction of the treatment. Generalized linear modelling supplemented by regression tree analysis was used to attain the second objective. Prescribed fire treatments were frequently (42% of the total number of units) intersected by wildfire, which occurs soon after treatment: the probability of an encounter peaked 2 years after treatment and its cumulative value grew at a diminishing rate with fuel age. Of all treated units, 58% burned entirely upon encounter and the median unburned fraction was 0.01 owing to the prevalence of intersections with large and presumably fast spreading and high intensity wildfires. Larger treatments burned less in area but the effect of wildfire characteristics was largely prevalent over the effect of treatment size. The unburned fraction of treated units seldom responded to fuel age, which we discuss based on biophysical influences, treatment effort, and fire suppression strategy. The high encounter rate but low effectiveness in decreasing burned area within treatments and, seemingly, nil effect for practical purposes on wildfire size indicates that prescribed burning is not impacting wildfire extent in Portugal. Our findings indicate the need to scale-up prescribed burning activity to effectively contribute to decrease wildfire size, but also improvements in fire management planning and operations in general.