The origin and successional status of anthropogenic dwarf shrub heath in Newfoundland

There are 1.2 × 10⁶ ha of heath vegetation on the island of Newfoundland. Some of this heath is of climatic or edaphic origin, but most of it has originated because of increasing frequency of fire and cutting following settlement of the area by European man since discovery in 1497. Modern fire suppression has been successful in reducing the size and frequency of fires in the last 40–50 years, however, natural forest regeneration is still not apparent in the anthropogenic heath.The ecotone between the forest-heath appears to have stabilized following an initial influx of trees up to 10 m from the forest margin. Analysis of the age structure of the invading trees demonstrates that after a period of 10 years new tree establishment is reduced to less than 5 percent of the total establishment. This decreased establishment over time is correlated with a coincidental increase in dwarf shrub heath vegetation that creates undesirable germination conditions for tree seed entering the heath. Even with ideal seedbed conditions for germination, the short distance of seed dispersal (10–20 m) and the excessively slow growth rates of trees, limit forest encroachment to a rate of 10 cm per year. At this rate more than a thousand years would be required for successional encroachement of even 2–3 ha of heathland. The successional status of the heath vegetation is considered to be permanent even though traditional concepts of secondary succession and chronosequence would predict the recovery of a climax forest vegetation.