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The role of seedling age and size in the recovery of Allosyncarpia ternata following fire
Author(s) -
FORDYCE I. R.,
EAMUS D.,
DUFF G. A.,
WILLIAMS R. J.
Publication year - 1997
Publication title -
australian journal of ecology
Language(s) - English
Resource type - Journals
eISSN - 1442-9993
pISSN - 0307-692X
DOI - 10.1111/j.1442-9993.1997.tb00671.x
Subject(s) - seedling , biology , rainforest , ecology , myrtaceae , horticulture
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.