Regeneration of potential laurel forest under a native canopy vs. exotic canopy, Tenerife (Canary Islands)

Jose Ramon Arevalo,J D Delgado,J M Fernandez-Palacios

doi:10.5424/fs/2011202-10921

Abstract

Exotic tree monocultures adversely affect native ecosystems through competition and alteration of nutrient availability and dynamics. However, there is evidence of some tree plantations facilitating a more rapid recovery of the native plant communities by providing shelter-wood for the plants below and attracting seed dispersers. The results either way are specific to the plantation species and to the native forest type. In this study we analysed the differences in regeneration of native woody species in two stands of exotic species, Pinus radiata and Eucaliptus globulus, occupying native laurel forest ground, and also examined the regeneration in adjacent native forest stands to reveal if the effects of the exotic plants are negatively affecting the recovery of the native plant community. The native stands differed from the exotic stands in tree species richness, basal area and density. However, regeneration was very similar between alien and native stands, and advanced regeneration can be inferred from the results. Differences were quantitatively important, but species composition of the regenerating community was similar. Also, these planted areas have recovered their canopy very fast as long as P. radiata and E. globulus have rapid growth in comparison with native laurel forest species. These rapid recover of the canopy has prevented deeper erosion damage and has to some extent facilitated the regeneration of native species. The results indicate that a progressive elimination of the exotic stands would favor the establishment and growth of native species. The role of some exotic tree species in the restoration of laurel forest areas should not be systematically regarded as negative.

Highlights

Because of conflicting evidence, it is not yet known whether exotic monocultures exert a predominantly negative or positive effect on the regeneration of the native forest beneath their canopies
We aim to evaluate the effect of plantations with exotic species on the regeneration of native woody species of laurel forest in Canary Islands, following the general hypothesis of a catalytic effect of the canopy created by exotic planted species on the recovery of the native forest
All the plots of the four classified stands were in the potential area of laurel forest in Tenerife, with a northerly dominant aspect and an altitude between 700-1,100 m (Table 1)

Summary

Introduction

It is not yet known whether exotic monocultures exert a predominantly negative or positive effect on the regeneration of the native forest beneath their canopies. Many exotic tree monocultures adversely affect native ecosystems through competition and alteration of nutrient cycles (Attiwill and Leeper, 1987; Jurgensen et al, 1986; Fimbel and Fimbel, 1996). Evidence suggests that some tree plantations facilitate a more rapid restoration of the plant forest community by providing shelter to the plants below and by attracting seed dispersers (Arévalo and Fernández-Palacios, 2005; Arévalo et al, 2005; Powers et al, 1997). Coniferous species have been used as nurse trees. This practice requires subsequent transformation of these evenaged forests into uneven-aged continuous forest (Schütz, 2001). The results are specific to the plantation species and the native forest type (Haggar et al, 1997; Parotta 1995; Parotta et al, 1997)

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