Abstract
Assessing impacts of management strategies may allow designing more resistant forests to wildfires. Planning-oriented models to predict the effect of stand structure and forest composition on mortality for supporting fire-smart management decisions, and allowing its inclusion in forest management optimization systems were developed. Post-fire mortality was modeled as a function of measurable forest inventory data and projections over time in 165 pure and 76 mixed forest stands in Portugal, collected by the 5th National Forest Inventory plots (NFI) plus other sample plots from ForFireS project, intercepted within 2006–2008 wildfire perimeters’ data. Presence and tree survival were obtained by examining 2450 trees from 16 species one year after the wildfire occurrence. A set of logistic regression models were developed under a three-stage modeling system: firstly multiple fixed-effects at stand-level that comprises a sub-model to predict mortality from wildfire; and another for the proportion of dead trees on stands killed by fire. At tree-level due to the nested structure of the data analyzed (trees within stands), a mixed-effect model was developed to estimate mortality among trees in a fire event. The results imply that the variation of tree mortality decreases when tree diameter at breast height increases. Moreover, the relative mortality increases with stand density, higher altitude and steeper slopes. In the same conditions, conifers are more prone to die than eucalyptus and broadleaves. Pure stands of broadleaves exhibit noticeably higher fire resistance than mixed stands of broadleaves and others species composition.
Highlights
Forests cover more than one third of Portugal (3.2 million of hectares), ranking eighth in Europe as highest country with forestlands, where the forest sector represents 3% of gross domestic product (GDP) and 12% of exports, and they are a key element in the Portuguese landscape pattern [1]
Post-fire mortality was modeled as a function of measurable forest inventory data and projections over time in 165 pure and 76 mixed forest stands in Portugal, collected by the 5th National Forest Inventory plots (NFI) plus other sample plots from ForFireS project, intercepted within 2006–2008 wildfire perimeters’ data
A set of logistic regression models were developed under a three-stage modeling system: firstly multiple fixed-effects at stand-level that comprises a sub-model to predict mortality from wildfire; and another for the proportion of dead trees on stands killed by fire
Summary
Forests cover more than one third of Portugal (3.2 million of hectares), ranking eighth in Europe as highest country with forestlands, where the forest sector represents 3% of gross domestic product (GDP) and 12% of exports, and they are a key element in the Portuguese landscape pattern [1]. In terms of the most affected areas nationwide, statistics (1996–2012) indicate that eucalyptus (Eucalyptus globulus Labill) and maritime pine (Pinus pinaster Ait) stands are flammable forest cover types that dominate northern and central Portugal, accounting 35.9% and 41.3% of forest burned, respectively. Limited effort has been devoted to promote mixed-species stands in Portugal as compared with the effort devoted to quantifying productivity on single-species stands [11]. This information could be an important tool for forest managers’ options
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