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Moisture absorption and drying alter nonadditive litter flammability in a mixed conifer forest
Author(s) -
Magalhães Rita Quis,
Schwilk Dylan W.
Publication year - 2021
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1111/1365-2745.13467
Subject(s) - litter , flammability , moisture , water content , environmental science , chemistry , ecology , biology , organic chemistry , geotechnical engineering , engineering
Moisture content is a strong determinant of forest fuel flammability. However, little is known about the mechanisms by which species‐specific litter traits influence litter moisture absorption and retention. Characterizing how litter fuels retain moisture through time and how fuels from multiple species interact are key steps to adding taxon‐specific information to fire behaviour prediction. To fill these gaps in knowledge, we determined moisture absorption and retention characteristics of the litter from multiple tree species, investigated what litter traits influenced these processes and tested for nonadditive moisture dynamics and nonadditive flammability in multi‐species mixtures. The litter from eight tree species of a mixed conifer forest was saturated and allowed to dry to determine moisture absorption capacity and drying rates. Burn trials were performed in litter beds of single species and of mixtures to establish flammability response to the dry‐down process and to species interactions. Litter mixtures exhibited nonadditivity in flame spread rate and in fuel consumption. This nonadditivity became more positive with fuel drying. Moisture dynamics varied across species with higher specific leaf area being associated with higher maximum absorption and lower litter bulk density being associated with faster drying rates. We found that these differing moisture dynamics resulted in time since wetting having strongly differing effects on flammability across the major litter types typified by different tree taxa. Synthesis . This study is the first to examine ecologically relevant drying rates and their interaction with nonadditive mixture effects on flammability. We find that taxon specific patterns of moisture absorption and drying change flammability rankings under moist compared with dry fuels because traits that increase flame spread rate increase water absorption. Litter mixtures generally burn with fire behaviour more similar to that of the most flammable constituent species and this effect increases as fuels dry.