The Wollemi Pine grows in a sandstone canyon in a ferny warm temperate rainforest. It grows on the steep lower slopes and ledges of the canyon on an acidic, sandy loam soil with pH of about 4.5. The main vascular associate plant species are Coachwood (Ceratopetalum apetalum), Sassafras (Doryphora sassafras), Lilly Pilly (Acmena smithii), Soft Treefern (Dicksonia antarctica), shield ferns (Lastreopsis spp.) and Umbrella Fern (Sticherus flabellatus).
- Fewer than 100 trees at several sites
- Average 4.7 stems per tree
- Average stem height is 11 m
- Average stem diameter is 118 mm
- Tallest tree is 38.5 m
- Widest stem is 0.67 m
The Wollemi Pine is bisexual (monoecious), with both male and female cones on the same tree. The round female cones produce the seeds, and the long male cones produce the pollen. The female and male cones start growing in mid-summer. In late spring the male cones release masses of pollen, which is carried by the wind, to fertilise the egg cells in the female cones. The female cones then take about 18 months to ripen, when the fertilised ovaries develop into seeds and they then fall apart high above the canyon floor, releasing winged seeds that float to the ground - research has been conducted into embryological (seed) development. If a seed falls in a suitable position and the weather is favourable it will germinate. Over time, if the light conditions are right, the small seedling may grow to become a majestic emergent rainforest tree.
Over 200 seedlings have been counted in the wild. Some of these are tagged and are being monitored for survival and growth rates. The seedlings grow on average only 1 cm per year and most are less than 30 cm high. Many of these seedlings will die unless there is a canopy opening that allows light in penetrate to the ground - thus providing energy for the seedlings to grow.
Given the right conditions the trees grow quickly for the first 15-20 metres until they reach the canopy, they then put more of their energy into the bulk of their trunks and root systems.
Through the millions of years of population decline, the Wollemi Pine has maintained its ability to sexually reproduce but has adopted a secondary reproductive strategy - that of self-coppicing.
Coppicing also helps the tree to survive disturbance. While tree ring analysis has revealed that trees with a diameter of 0.8 m may be 350+ years old, the coppice roots may be thousands of years old. The extensive root system of the Wollemi Pine may also explain how it has survived droughts - the roots penetrate into creek beds and into cracks in the sandstone cliffs.
All populations have been burnt or subjected to rock fall or windstorm damage. It is postulated that if these disturbance events happen too often they may reduce or eliminate the Wollemi Pine's population. On the other hand, if there is no disturbance the other rainforest plants may dominate the glades and prevent the Wollemi Pine's seedlings from growing into adult trees.
Some big ecological questions
The long-term aim of the ecological research into the Wollemi Pine is to track the survivorship of the trees and the seedlings. This may reveal some insight into how to manage disturbance such as wildfire at the sites.
- How old are the coppice trees and how long can they live?
- Could too-frequent wildfire destroy the stands?
- How frequent and what type of disturbance would ensure survival of the Wollemi Pine?
- How do we manage illegal visitation to minimise impacts?