A.M.T.A. Gunaratne et al. / Forest Ecology and Management 262 (2011) 229–236
grasses in degraded human-induced grasslands unless supplemen-
highest survival in the presence of root competition, Symplocos
cochinchinensis, had a lower maximum relative growth rate in the
absence of root competition. Our study did not investigate the
traits that determine this trade-off, but it supports the suggestion
that species that use nutrients and water relatively conserva-
tively, would be a more suitable choice for restoration plantings
Baraloto et al., 2006; Craven et al., 2007; Dalling and Burslem,
4.2. Implications for restoration of degraded land
cal Asia, has identiﬁed that intensive mechanical site preparation
and/or fertilization of grasslands are required to promote tree
seedling emergence, survival and growth (
Gunaratne et al., 2010;
Hau and Corlett, 2003; Otsamo et al., 1995
). Our results conﬁrm
that these interventions are required because root competition
from grasses inhibits tree seedling establishment. However, trench-
ing tree seedlings individually is likely to be impractical and too
costly to consider as a large-scale tool for catalysing forest restora-
tion. An alternative approach is to plant tree seedlings or living
stakes of competition-insensitive species at low density in order
to establish a cover that would suppress the grasses sufﬁciently
to facilitate colonisation by trees (
). As well as sup-
pressing the grass sward, these shade trees can provide perches for
seed-dispersing birds and bats, enhance the local nutrient status
through inputs of litter and ameliorate harsh microclimatic con-
Florentine and Westbrooke, 2004; Guevara and Laborde,
1993; Kellman, 1985; Martinez-Garza and Howe, 2003; Rhoades
et al., 1998; Toh et al., 1999
). Seed dispersers may be attracted
to ﬂeshy-fruited trees growing in grassland even when they are
Slocum and Horvitz, 2000
) and to trees with wide
canopies irrespective of their dispersal syndrome (
Jones et al.,
Our research has identiﬁed two promising native tree species for
use in this context in upland central Sri Lanka, although we propose
that they would be planted for different purposes. In the presence
of root competition, seedlings of Symplocos cochinchinensis had the
highest survival among the four species we tested, and their growth
rates were not signiﬁcantly different to those of the species with
the highest potential growth rates, Macaranga indica. We recom-
mend the use of Symplocos in the earliest stages of restoring natural
forests on grasslands to provide a cover of shade and reduce the
vigour of the grass sward. Although Symplocos has sugar-rich pur-
ple fruits, they are not as attractive to bird dispersers in the area
as the Macaranga fruits (personnel observation). Therefore, Sym-
plocos is less likely to facilitate the natural colonisation of other
plant species in the vicinity of Symplocos trees through bird dis-
persal, compared to Macaranga. Hence we propose that Macaranga
seedlings should be planted in gaps between the Symplocos saplings
once the density of grasses has diminished sufﬁciently to allow the
Macaranga seedlings to survive. Although the established Symplo-
cos canopy would reduce irradiance relative to open conditions, our
results showed that transplanted Macaranga seedlings are capa-
ble of maintaining high survival and growth rates under a light
canopy, as long as competition with grasses has been eliminated. A
mixed plantation of Symplocos and Macaranga would initiate the
early stages of converting these degraded lands into productive
secondary forests with greater potential to enhance the capacity
of the landscape to retain biodiversity and deliver ecosystem ser-
vices. We advocate further research to reﬁne this strategy for forest
restoration in upland central Sri Lanka, including trials of additional
species from the native tree ﬂora.
We thank the Forest Department of Sri Lanka for granting per-
mission to carry out research in the Knuckles Forest Reserve and the
EU-Asia link programme for funding. We are grateful to the private
landowners (Mr. D.H.C. Manatunga, Mr. S.A. Welgama, Mr. C. Rat-
watta and members of Eco-friends Lanka) who lent their land for
research and to Mr. and Mrs. A. Jayawardena for allowing us to use
climate data collected at their bungalow. Professor Ian Alexander
provided helpful comments on an earlier version of the manuscript.
Appendix A, B, C, D and E. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at
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