Ir. Fordyce et al., THE ROLE OF SEEDLING AGE AND SIZE IN THE RECOVERY OF ALLOSYNCARPIA-TERNATA FOLLOWING FIRE, Australian journal of ecology, 22(3), 1997, pp. 262-269
This paper examines the effects of seedling size and age on fire toler
ance 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 seed
ling 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 exper
iment, shadehouse-grown seedlings aged from 8 months to 5 years were s
ubjected to low-and high-intensity fires in September 1994. Among 5-ye
ar-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 int
ermediate manner; their survivorship and growth were marginally favour
ed by low intensity fire, rather than high-intensity fire or no fire a
t all, and were dependent on pre-treatment seedling height. Thus, the
critical age that distinguishes fire-tolerant from fire-sensitive seed
lings is somewhat more than 3 years for relatively short seedlings and
somewhat less than 3 years for taller seedlings. In August 1993, a wi
ldfire penetrated several hundred metres into Allosyncarpia forest gro
wing on a steep, rocky escarpment, where it caused severe damage to A.
ternata seedlings. More than three-quarters of the greater than or eq
ual to 3.5-year-old seedlings (including some that had suffered the to
tal loss of above-ground parts) recovered during the following wet sea
son and showed higher growth rates than their unburned neighbours. New
growth was also promoted in those tall seedlings and saplings that ha
d sustained only partial leaf scorch. In contrast, all 18-month-old se
edlings were killed by the fire. Measurements of leaf-scorch height in
burned Allosyncarpia forest on the escarpment indicated a general uph
ill decrease in fire intensity, matching trends in increasing site roc
kiness 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 germi
nants to progress into the cohort of established seedlings.