Botanic Gardens Trust, Sydney, Australia

Plant info




Ecology

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 (Lastriopsis spp.) and Umbrella Fern (Sticherus flabellatus).

Population parameters

  • 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

Growth

A remarkable aspect of the Wollemi Pine's ecology is that it is able to produce viable seed with no detectable genetic variation in its population.

Over 200 seedlings have been counted. 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 then they put more of their energy into the bulk of their trunks and root systems. Their stem to diameter growth rate is a binomial rather than a linear relationship.

Coppicing

Through the millions of years of population decline, the Wollemi Pine has maintained its fitness for sexual reproduction but has adopted a secondary reproductive strategy - that of self-coppicing (see Characteristics).

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 creekbeds and into cracks in the sandstone cliffs.

Disturbance

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. 

The main threat to the survival of the Wollemi Pine is visitation by humans - see protecting it. They may trample the seedlings, compact the soil and risk introducing the deadly root pathogen Phytophthora cinnamomii - see fungal associations & pathogens - which could wipe out the wild population of the Wollemi Pine.

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?

Tagging and measuring Wollemi Pines
All Wollemi Pine trees have been tagged and the height and diameter of each coppice stem has been measured so changes can be tracked over time.

Surveying plants
Scientists surveying and measuring Wollemi Pine plants.

Tagged seedling
Wollemi Pine seedlings are being counted, tagged and monitored for survival and growth rates.

Rock fall
Wollemi Pines are subject to disturbance events, such as rock falls.