Non-additive effects of leaf and twig mixtures from different tree species on experimental litter-bed flammability
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Tree species can affect litter flammability through leaf size and shape. Larger, simpler-shaped leaf litters form better-ventilated, more flammable litter-beds. However, leaves are generally mixed with twigs in the forest litter layer and together they likely contribute most to surface fire behavior. Here we ask: “Do leaf-twig mixtures have non-additive effects on litter-bed flammability?”
Using laboratory fires, we tested the direction and magnitude of non-additivity of inter- and intra-specific leaf-twig mixtures on litter-bed flammability for four tree species contrasted in leaf size and shape and widespread in fire-prone temperate-boreal forests.
Across species, small needles reduced mixture fuel-bed ignitibility through filling the space between twigs and inhibiting ventilation. Within the small broad-leaved species, the thin, frequently branched and open spaced twigs were too loosely packed to be flammable, while in mixtures the small broad leaves connected these twigs to produce flammable fuel-beds. Once ignited, across species flame spread rate in mixtures was driven by leaves, while fire sustainability was predicted by fuel mass. Fuel-bed flammability was driven more by leaves at larger leaf-to-twig ratio.
For the first time, we demonstrated the existence and mechanisms of non-additive effects of leaf-twig mixtures on experimental litter-bed flammability.
KeywordsFlammability Leaf Litter mixing Non-additivity Plant traits Surface fire behavior Twig
We are grateful to the Chinese Scholarship Council for funding WWZ through a 4-year fellowship to study at VU University Amsterdam. The setup of the FLARE laboratory greatly benefitted from grant 047.018.003 by the Netherlands Organization for Scientific Research (NWO) to JHCC. This work was supported by National Key R&D Program of China (grant: 2016YFC0503100) and National Natural Science Foundation of China (grants: 31670429). JHCC and WWZ benefitted from Grant CEP-12CDP007 by the Royal Netherlands Academy of Arts and Sciences (KNAW).
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Conflict of interest
The authors declare that they have no conflict of interest.
- Martin RE, Gordon DA, Gutierrez M, Lee D, Molina DM, Schroeder RA … Stephens S L. (1994) Assessing the flammability of domestic and wildland vegetation. In Proceedings of the 2nd International Fire and Forest Meteorology Conference (pp. 130–137). Jekyll Island, GAGoogle Scholar
- Plucinski M, Catchpole W (2001) Predicting ignition thresholds in litter layers. In: Ghassemi F, Post DA, Sivapalan M, Vertessy R (eds) MODSIM 2001 International Congress on Modelling and Simulation, December 2001, Canberra, Australia, vol 1. Modelling and Simulation Society of Australia and New Zealand, pp 967–971Google Scholar
- R Core Team (2013) R: a language and environment for statistical computing. R Foundation for Statistical Computing, ViennaGoogle Scholar
- Rothermel RC (1972) A mathematical model for predicting fire spread in wildland fuels. Research Paper INT-115. US Department of Agriculture, Forest Service, OgdenGoogle Scholar
- Scott JH, Burgan RE (2005) Standard fire behavior fuel models: a comprehensive set for use with Rothermel's surface fire spread model. USDA Forest Service, Rocky Mountain Research Station, General Technical Report RMRS-GTR-153, 72 pp.Google Scholar
- van Altena C, van Logtestijn RSP, Cornwell WK, Cornelissen JHC (2012) Species composition and fire: non-additive mixture effects on ground fuel flammability. Front Plant Sci 3:63Google Scholar