Native Plant Colonization of Eucalyptus Plantations in Farmscapes in Relation to Local, Landscape and Historical constraints: Implications for Ecological Restoration
No Thumbnail Available
Date
2016-12
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa Universty
Abstract
Agricultural expansion has caused much habitat loss across the world. Still there can be
substantial levels of biodiversity in such landscapes and we need to understand more about the
distribution of biodiversity in such landscapes. In some agricultural landscape there is a
reforestation or afforestation trend, often with exotic trees and with the aim of generating wood
products. To what extent plantations of exotic trees can harbor native biodiversity is an
important question. Generally, the capacity of plantations to contain native species depend both
on local, landscape and historical factors. The current study was conducted in a farmscape in
central Ethiopia characterized by scattered small Eucalyptus plantations located at different
distances from a remnant forest (Chilimo forest). The objectives of this study were to understand
to what extent local, landscape and historical factors constrain or foster native woody and herb
species regeneration in these Eucalyptus plantations. Additionally the roles of retained, isolated
trees of Podocarpus falcatus and Juniperus procera as propagule sources were investigated. All
native woody and herb species in 60 small (0.5-1.75ha) Eucalyptus plantations embedded in an
open farmscape ranging in distance from 0.1 to 12 km from the remnant continuous forest were
collected and identified. Presence/absence data on herbs was also collected in four 100 m x 50 m
plots in the Chilimo forest to be used for characterization of the forest herb flora. The ages of the
studied Eucalyptus plantations were estimated by using Aerial photosfrom1988-2014. The
location of remnant trees of P. falcatus and J. procera were recorded within a circular plot of
500 m radius around each Eucalyptus plantations. A total of 1571 individuals of native woody
plants belonging to 55 species were recorded in the plantations. The number of woody species in
a plantation increased significantly with the height of the grass sward indicating sensitivity to
grazing. Moreover, the number of woody species in the Eucalyptus plantations decreased
significantly with distance to the forest showing that they were dispersal limited. The likelihood
of presence of P. falcatus in Eucalyptus plantations increased with connectivity to retained
mature trees in the surrounding area, but not so for J. procera. For the herbs a total number of
92 species were recorded in the plantations, of which 47 were denoted forest species and 45 nonforest
species based on the comparison with the forest plot data. The number of forest herb
species in the Eucalyptus plantations decreased with distance from the forest why this not was
the case for the non-forest herb taxa. However, both the number of forest and non-forest herb
species increased with the height of grass swards illustrating sensitivity to grazing also for this
species groups. To conclude, sowing or planting native plants will be necessary in most
plantations across the country if biodiversity of the plantations should increase and more
resemble forest biodiversity, since only few remnant natural forests that could act as seed
sources occur across the Ethiopian highlands. Another main obstacle might be the prohibition of
selling timber of native trees, which indirectly discourage farmers from letting native trees
regenerate. Thus the increasing cover of Eucalyptus seen across the country will not
automatically foster a recovery of native woody plant biodiversity, even if it is managed to
optimize local environmental conditions.
Keywords: Chilimo forest, colonization, dispersal, farmscapes, native flora, restoration, smallscale
Eucalypts plantations
Description
Keywords
Chilimo forest, Colonization, Dispersal, Farmscapes, Native flora, Restoration, smallscale Eucalypts plantations