Abstract
Abstract This paper examines the effects of seedling size and age on fire tolerance of Allosyncarpia ternata (Myrtaceae), a dominant tree in patches of monsoon rainforest of the wet‐dry tropics in the Northern Territory, Australia. We address the following questions: how large does a seedling have to be to tolerate fire; how old does it have to be to reach this fire‐tolerant size; and how can land‐management authorities best manage fire regimes to maintain Allosyncarpia forest? In a field experiment, shadehouse‐grown seedlings aged from 8 months to 5 years were subjected to low‐ and high‐intensity fires in September 1994. Among 5‐year‐old seedlings, mortality was independent of fire intensity. However, mortality of young (8‐month‐old) seedlings was significantly higher in the high‐intensity fire. Three‐year‐old seedlings behaved in an intermediate manner; their survivorship and growth were marginally favoured by low‐intensity fire, rather than high‐intensity fire or no fire at all, and were dependent on pre‐treatment seedling height. Thus, the critical age that distinguishes fire‐tolerant from fire‐sensitive seedlings is somewhat more than 3 years for relatively short seedlings and somewhat less than 3 years for taller seedlings. In August 1993, a wildfire penetrated several hundred metres into Allosyncarpia forest growing on a steep, rocky escarpment, where it caused severe damage to A. ternata seedlings. More than three‐quarters of the ≥ 3.5‐year‐old seedlings (including some that had suffered the total loss of above‐ground parts) recovered during the following wet season and showed higher growth rates than their unburned neighbours. New growth was also promoted in those tall seedlings and saplings that had sustained only partial leaf scorch. In contrast, all 18‐month‐old seedlings were killed by the fire. Measurements of leaf‐scorch height in burned Allosyncarpia forest on the escarpment indicated a general uphill decrease in fire intensity, matching trends in increasing site rockiness and decreasing fuel density. An important implication for land management is that a fire‐free interval of at least 3 years following a seed‐fall event is required for a new generation of A. ternata germinants to progress into the cohort of established seedlings.
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Claims 12
Claim · model-written summary
Fire intensity did not alter mortality among five-year-old seedlings.
- Organ / stage
- 5‐year‐old seedlingse0
- Treatment
- fire intensitye0
- Outcome
- mortalitye0
- Direction
- independente0
Not reportedTaxon
Verbatim
e0“Among 5‐year‐old seedlings, mortality was independent of fire intensity”
t0“Allosyncarpia ternata”
Claim · model-written summary
Young seedlings had significantly greater mortality under high-intensity fire.
Not reportedTaxonComparator
Verbatim
e0“mortality of young (8‐month‐old) seedlings was significantly higher in the high‐intensity fire”
t0“Allosyncarpia ternata”
Claim · model-written summary
Three-year-old seedling survival and growth were marginally favored by low-intensity fire.
- Treatment
- low‐intensity firee0
- Outcome
- survivorship and growthe0
- Direction
- favourede0
- Comparator
- high‐intensity fire or no fire at alle0
Not reportedTaxon
Verbatim
e0“their survivorship and growth were marginally favoured by low‐intensity fire, rather than high‐intensity fire or no fire at all”
t0“Allosyncarpia ternata”
Claim · model-written summary
Three-year-old seedling survival and growth depended on pretreatment height.
Not reportedTaxonDirection
Verbatim
e0“their survivorship and growth were marginally favoured by low‐intensity fire, rather than high‐intensity fire or no fire at all, and were dependent on pre‐treatment seedling height”
t0“Allosyncarpia ternata”
Claim · model-written summary
Fire tolerance threshold was above three years for short seedlings and below three years for taller seedlings.
Not reportedTaxon
Verbatim
e0“critical age that distinguishes fire‐tolerant from fire‐sensitive seedlings is somewhat more than 3 years for relatively short seedlings and somewhat less than 3 years for taller seedlings”
t0“Allosyncarpia ternata”
Claim · model-written summary
Wildfire caused severe damage to seedlings.
- Taxon
- A. ternata
Allosyncarpia ternatae0 - Outcome
- severe damage to A. ternata seedlingse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it caused severe damage to A. ternata seedlings”
Claim · model-written summary
More than three-quarters of older seedlings recovered after wildfire.
Not reportedTaxon
Verbatim
e0“More than three‐quarters of the ≥ 3.5‐year‐old seedlings (including some that had suffered the total loss of above‐ground parts) recovered during the following wet season”
t0“Allosyncarpia ternata”
Claim · model-written summary
Recovered older seedlings grew faster than unburned neighbors.
Not reportedTaxon
Verbatim
e0“showed higher growth rates than their unburned neighbours”
t0“Allosyncarpia ternata”
Claim · model-written summary
Partial leaf scorch promoted new growth in tall seedlings and saplings.
Not reportedTaxon
Verbatim
e0“New growth was also promoted in those tall seedlings and saplings that had sustained only partial leaf scorch”
t0“Allosyncarpia ternata”
Claim · model-written summary
The wildfire killed all 18-month-old seedlings.
- Outcome
- 18‐month‐old seedlings were killede0
Not reportedTaxon
Verbatim
e0“all 18‐month‐old seedlings were killed by the fire”
t0“Allosyncarpia ternata”
Claim · model-written summary
Fire intensity decreased uphill with increasing rockiness and decreasing fuel density.
- Outcome
- fire intensitye0
- Direction
- decreasee0
- Qualifier
- increasing site rockiness and decreasing fuel densitye0
- Setting
- uphille0
Not reportedTaxon
Verbatim
e0“a general uphill decrease in fire intensity, matching trends in increasing site rockiness and decreasing fuel density”
t0“Allosyncarpia ternata”
Claim · model-written summary
The authors recommend at least three fire-free years after seed fall for seedling establishment.
- Taxon
- A. ternataAllosyncarpia ternatae0
- Outcome
- a fire‐free interval of at least 3 years following a seed‐fall evente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a fire‐free interval of at least 3 years following a seed‐fall event is required for a new generation of A. ternata germinants to progress into the cohort of established seedlings”