Regeneration of tropical acacia species in response to fire

Congdon, Robert, Williams, Paul, and Parsons, Mark (2011) Regeneration of tropical acacia species in response to fire. In: Abstract Book of XVIII International Botanical Congress, pp. 374-375. From: IBC2011 XVIII International Botanical Congress, 23-30 July 2011, Melbourne, VIC, Australia.

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Abstract

Most acacias are well known to regenerate prolifically from the soil seed bank following fire, however some species have been observed to resprout from the base. This study examines the germination and resprouting behaviour of 8 species - A. cincinnata, A. crassicarpa, A. flavescens, and A. mangium from tropical coastal woodlands and forests, and A. elachantha, A. hyaloneura, A. platycarpa, and A. ramiflora from the inland woodlands of White Mountains National Park in north Queensland.

Seeds of each species were subjected to dry heat at 40, 60, 80, 100 and 120°C and in water at 60 and 80°C for 5 minutes, and then incubated at 28°C. Highest germination percentages were found for most species after treatment with 80 or 100°C dry heat or 80°C wet heat. Some 49% of seeds across treatments germinated over the first 140 days, whilst 10% of the remaining seeds germinated over a further 614 days, with one third of seeds remaining potentially viable after this time.

In a pot study of resource allocation, eight individuals of A. cincinnata, A. crassicarpa, A. flavescens, A. mangium, A. platycarpa and A.ramiflora, 6 individuals of A. hyaloneura, and 3 A. elachantha were grown in 200 mm pots for 18 months. After harvesting the above-ground biomass, all of the wattles resprouted from the base, except A. hyaloneura and A. mangium.

To further examine resprouting behaviour, nine 12 m x 12 m plots, separated by 4 m fire breaks, were established. Acacias were planted at a spacing of 1.5 m x 3 m. Three replicates were allocated randomly to the three treatments – control, burnt and clipped. Seedlings were planted between October and December 2003, most by the end of November. Ten individuals of A. crassicarpa, A. flavescens, A. ramiflora and 8 of A. elachantha were planted in each plot, alternating between species. Fewer individuals of A. mangium (10), A. platycarpa (9), A. cincinnata (10) and A. hyaloneura (2) were available, and these were planted in even numbers across plots. Three plots were burnt on August 2004. In 3 plots, the wattles were cut 3 cm from the base on September 2004. Surviving plants were measured in September 2004 and September 2005. Only one individual each of A. crassicarpa and A. mangium survived the fire treatment, while 3 individuals of A. crassicarpa, and one individual of A. ramiflora, A. elachantha and A. mangium survived the clipping treatment. Hence, survival was low, probably due to the competition from a high biomass of Guinea Grass (Megathyrsus maximus), and the intensity of the fire fuelled by the high fuel load.

The results indicate that germination of most species is favoured by a heat shock at 80°C for 5 minutes. All species but A. hyaloneura showed some ability to resprout, but few resprouted following an intense fire. For management purposes, low intensity fire may promote resprouting of many of these species, but high fuel loads, such as result from invasive grasses, will not favour resprouting.

Item ID: 19953
Item Type: Conference Item (Poster)
Date Deposited: 07 Mar 2012 23:22
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050205 Environmental Management @ 30%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060207 Population Ecology @ 70%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960599 Ecosystem Assessment and Management not elsewhere classified @ 50%
96 ENVIRONMENT > 9613 Remnant Vegetation and Protected Conservation Areas > 961306 Remnant Vegetation and Protected Conservation Areas in Forest and Woodlands Environments @ 50%
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