BIOL3701 Lecture Notes - Lecture 7: Myrmecochory, Serotiny, Seed Bank
26 Jun 2018
School
Department
Course
Professor
Fire and Restoration
History of Fire in Australia
Progressive aridification during Pleistocene (2.6 million – 12,000 y.a.)
oWith higher charcoal levels corresponding to glacial (more arid) periods
Difficult to establish cause and effect among climate change, human
occupation and fire
oALTHOUGH there is an association between charcoal peaks and
vegetation changes in northern Australia
At a time of relative climatic stability ca. 35,000 years ago
Increased burning and more open vegetation for last 40,000 years
Holocene (last 10,000 years):
oPeak in burning in the early phase of European occupation
But burning is now below the average of the Holocene
Fire weather is monitored with the Forest Fire Danger Index
oHas increased throughout the years
Fire Regimes
The typical sequence of fires in a given area
oFire intensity
oCanopy or ground
oFire frequency
oSeasonality
Types of Fires
Wildfires
oDifficult to predict
oCan vary markedly in intensity and scale
oAffected by:
Climate, topography, season, vegetation type etc.
Prescribed
oHazard reduction
oImportant and widely-applied tool used in the management of fire-
prone ecosystems
oPenman et al. (2011):
Prescribed burning is commonly used to achieve 2 outcomes:
1. A reduction in fuel loads to mitigate the severity of
unplanned wildfires fuel reduction
2. A manipulation, protection or restoration of the status
and composition of ecosystems ecological burning
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Coping with Fire
Plants
oThick bark
oEpicormic shoots
Ability of some trees to regrow
oLignotuber
Woody swelling of the root crown to protect itself
oMyrmecochory
Seed dispersal by ants
oSerotiny
Release of seeds following fire or another cue
oGermination (sprouting of a seedling)
Stimulated by fire-related cues (heat and smoke)
Compounds “KARRIKINS” in smoke stimulate germination
Germination After a Fire
Why is it beneficial?
oIncreased nutrients (the ‘ash bed’ effect)
oRemoval of leaf litter that suppresses seedlings
As well as of competing plants
oIncreased light
oFewer predators (e.g. seed-eating ants)
Applying Fire Treatment
Trailing burns at different seasons
Effects of hot and cool burns
Large replicated experiment with Control, Hot burn and Cool burn
oAt each site
Fire and Seedbanks
Rawson et al. (2012)
oInvestigated effect of fire-related treatments in a controlled glasshouse
To help inform the design of prescribed burning programs in the
field
oInvestigated:
Germination responses of the seed back of the narrow-leaved
mallee community to:
Smoke, heat and a combined smoke and heat treatment
Ten roadside sites that had been ungrazed for >20 years:
oSoil samples from each plot were mixed and then sub-divided into four
lots all allocated at random to four treatment groups:
Control
Heat
Smoke
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Progressive aridification during pleistocene (2. 6 million 12,000 y. a. : with higher charcoal levels corresponding to glacial (more arid) periods. Difficult to establish cause and effect among climate change, human occupation and fire: although there is an association between charcoal peaks and vegetation changes in northern australia. At a time of relative climatic stability ca. Increased burning and more open vegetation for last 40,000 years. Holocene (last 10,000 years): peak in burning in the early phase of european occupation. But burning is now below the average of the holocene. Fire weather is monitored with the forest fire danger index: has increased throughout the years. The typical sequence of fires in a given area: fire intensity, canopy or ground, fire frequency, seasonality. Wildfires: difficult to predict, can vary markedly in intensity and scale, affected by: Prescribed: hazard reduction, important and widely-applied tool used in the management of fire- prone ecosystems, penman et al. (2011): Prescribed burning is commonly used to achieve 2 outcomes:
