Radial growth of the endemic species Nothomyrcia fernandeziana (Hook. & Arn.) Kausel and the invasive species Aristotelia chilensis (Molina) Stuntz in Robinson Crusoe Island, Juan Fernandez Archipelago, Chile

Abstract

Nothomyrcia fernandeziana (Hook. & Arn.) Kausel is an endemic tree species from Robinson Crusoe Island (RC), Juan Fernández Archipelago, Chile. Aristotelia chilensis (Molina) Stuntz, is an invasive species introduced in the island since the mid XIX century that compete with endemic species and threatens their conservation. Radial growth patterns can reveal biological strategies of woody plants, such as longevity, shade tolerance and competitive capacity, which are of special relevance for conservation programmes. The objectives of this work were to characterize the tree rings of both species and to study their radial growth patterns, in order to obtain basic knowledge for the conservation of endemic forests in RC. We studied wood anatomy and dendrochronology for stem cross sections of both species in RC, and also of A. chilensis within its natural distribution range in continental Chile. The wood of both species exhibited well-differentiated tree rings. N. fernandeziana showed reduced juvenile growth rates, long-lived trees and high capacity to release its growth (increase greater than 100% of the average ring-width for the 10 years before the event). A. chilensis, by contrast, showed large growth rates during their complete lifespan but reduced longevity, a typical behaviour of a pioneer species, as well as in their natural range. Based on these results, it is suggested to promote the establishment of N. fernandeziana under the canopy of A. chilensis, favouring the gradual replacement of the invasive species by the endemic species in Robinson Crusoe.