Abstract
The on-going destruction of old-growth forests puts tropical forest species under great pressure because of the resulting loss of habitat. An important biotic component of these forests are vascular epiphytes, which structurally depend on trees. In human-modified landscapes potential hosts may still be present, e.g. in the form of isolated remnant trees, small groups of planted trees, in patches of secondary forests, or in plantations. For this study, we assessed the potential of timber monocultures and secondary forest patches to function as refuges for vascular epiphytes. We studied epiphyte assemblages in teak and pine plantations and secondary forest patches of unknown age along a rainfall gradient (1100 – 4200 mm) at the Pacific coast of western Panama and also in a few oil palm plantations. Invariably, rainfall had the expected positive influence on epiphyte diversity and abundance. Individual-based rarefaction curves showed that species richness was significantly lower in timber and oil palm plantations compared to secondary forest patches, which in turn hosted less species-rich epiphyte assemblages than (cultivated and wild grown) pasture trees from the same study region. Our results suggest that the value of timber and oil palm plantations as refuges for vascular epiphytes in human-modified landscapes is limited. Secondary forest patches were more promising in that regard.
Highlights
Individual-based rarefaction curves showed that species richness was significantly lower in timber and oil palm plantations compared to secondary forest patches, which in turn hosted less species-rich epiphyte assemblages than pasture trees from the same study region
Data sampling We studied epiphyte assemblages in three types of plantations and secondary forest patches, which were selected along the rainfall gradient of the study region in seven secondary forest patches, six teak plantations (Tectona grandis L.f.), and three pine plantations (Pinus caribaea Morelet)
In the oil palm plantations species richness was low with just 5 species, but abundance was high with a total of 1529 individuals
Summary
Tree plantations are gaining economic importance. Between 2005 and 2010 the total area they covered increased by some 5 million hectares a year [1]. Tree plantations are far less complex than most natural forests, and are of less ecological value. Epiphytes are diverse and important elements of tropical forests, but depend mechanically on their host trees and are highly vulnerable when deforestation occurs [e.g. 3-6]. Continuous destruction of their natural habitat [1] leaves a fragmented matrix in which plantations may be one possible refuge. Older plantations are structurally more complex than younger plantations [7] and support more diverse assemblages of forest species of diverse ecological groups [2 and references therein]. Kanowski et al [7] point out that this effect correlates inversely with management intensity
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