Quinones De Magalhaes, Rita Margarida , Schwilk, Dylan .
Leaf traits and litter flammability: Understanding multi-species mixtures.
Leaf traits vary greatly across species and they are an indication of a species' ecological and "economic" growth strategy. In some cases, these traits may have ecosystem effects even after leaf senescence. For example, leaf traits greatly influence the rate of leaf litter decomposition. Leaf traits,therefore, are likely to influence the flammability of leaf litter. However, we currently lack a sound mechanistic view of litter flammability. A more mechanistic perspective is particularly important as researchers attempt to understand and predict fire in plant communities that are changing. Although past work has pointed to potentially important traits affecting litter flammability, one current gap in understanding is how such traits interact in multi-species mixtures. If there are interactions among species, the effect of a species on community flammability may be disproportionate to its contribution to the leaf litter mix. Understanding such possible non-additive effects is essential for predicting flammability of novel species combinations.This work addresses three questions: 1) How do eight species common in a temperate mixed conifer forest differ in their litter flammability?; 2) What leaf traits are associated with various flammability components?; and 3) Do individual species measurements predict multi-species combinations or are there non additive effects? Leaf litter was collected in Sequoia and Kings Canyon National Parks, in the Sierra Nevada Mountains, California, from eight common co-occurring tree species: Pinus jeffreyi, P.lambertiana, P. ponderosa, Abies concolor, A. magnifica, Calocedrus decurrens,Quercus kelloggii and Sequoiadendrongiganteum. The flammability tests were performed on monospecific litter beds and on litter beds composed of mixtures of litter from three different species. We measured flammability parameters (ignitability,sustainability, spread rate, maximum flame height, consumability and heat release) on a 150 cm long burn table that approximated the conditions of a natural litter fire. We tested for non-additive effects in multi-species mixtures against a null model in which the predicted value of each flammability component was the weighted average the three individual species flammabilities. We found consistent flammability differences across species and we demonstrate that flammability parameters related to fireline intensity are driven by leaf size. Most importantly, we found consistent non-additive mixture effects:multi-species mixtures have faster flame spread rates and higher flame heights than predicted from individual species trials. In this forest ecosystem, non-additivity may strengthen positive feedback effects as long-leaved pines are favored by the higher fire intensities to which they disproportionately contribute.
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1 - Texas Tech University, Biological Sciences, Flint And Main, Lubbock, TX, 79409-3131, USA
2 - Texas Tech University, Biological Sciences, Flint and Main, Lubbock, TEXAS, 79401, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Union B/Hyatt
Date: Tuesday, July 10th, 2012
Time: 2:45 PM