Fire season and intensity affect shrub recruitment in temperate sclerophyllous woodlands |
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Authors: | K J E Knox P J Clarke |
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Institution: | (1) Department for Environment and Heritage, 6/17 Lennon Street, Clare, SA, 5453, Australia;(2) Department of Botany, School of Environmental Sciences and Natural Resources Management, University of New England, Armidale, 2351, Australia |
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Abstract: | The season in which a fire occurs may regulate plant seedling recruitment because of: (1) the interaction of season and intensity
of fire and the temperature requirements for seed release, germination and growth; (2) post-fire rainfall and temperature
patterns affecting germination; (3) the interaction of post-fire germination conditions and competition from surrounding vegetation;
and (4) the interaction of post-fire germination conditions and seed predators and/or seedling herbivores. This study examined
the effects of different fire intensities and fire seasons on the emergence and survival of shrubs representing a range of
fire response syndromes from a summer rainfall cool climate region. Replicated experimental burns were conducted in two seasons
(spring and autumn) in 2 consecutive years and fuel loads were increased to examine the effects of fire intensity (low intensity
and moderate intensity). Post-fire watering treatments partitioned the effects of seasonal temperature from soil moisture.
Higher intensity fires resulted in enhanced seedling emergence for hard-seeded species but rarely influenced survival. Spring
fires enhanced seedling emergence across all functional groups. Reduced autumn recruitment was related to seasonal temperature
inhibiting germination rather than a lack of soil moisture or competition. In Mediterranean-type climate regions, seedling
emergence has been related to post-fire rainfall and exposure of seeds to seed predators. We think a similar model may operate
in temperate summer rainfall regions where cold-induced dormancy over winter exposes seeds to predators for a longer time
and subsequently results in recruitment failure. Our results support the theory that the effect of fire season is more predictable
where there are strong seasonal patterns in climate. In this study seasonal temperature rather than rainfall appears to be
more influential. |
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Keywords: | Fire regime Seedling emergence Seedling survival Grassy woodlands |
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