Can Eucalyptus
Plantations Provide a Suitable Habitat for Epigeic Forest Insects
of the Atlantic Forest, Minas Gerais, Brazil
Tania Bird
INTRODUCTION
- Eucalyptus plantations have become
increasingly popular in Brazil, providing wood for the timber,
pulp and fuel industries.
- Many farmers have begun planting Eucalyptus
as an alternative to traditional crops such as coffee or sugar
cane both of which are known to be particularly destructive to
natural ecosystems (Eyre 1967)
- It can be argued that in comparison to these
traditional crops, Eucalyptus plantations may be the most
ecologically beneficial alternative although no definitive
evidence has yet to be produced.
- However, many studies have shown that plant
diversity is directly associated with insect diversity (Gaston
& Lawton 1988, Andow 1991, Goncalves-Alvim & Fernandes
2001) and the preservation of habitat heterogeneity should
therefore be a priority in conservation strategies
(Romero-Alcaraz & Avila 2000).
- Nevertheless, few studies have assessed the
impact of growing Eucalyptus monocultures on the indigenous
invertebrate fauna of Brazilian forests.
OBJECTIVE
To examine the
effect of different forest types: degenerated Atlantic Forest
(forest that was selectively logged but never clear cut),
regenerated secondary forest (forested area that was once clear
cut for agricultural purposes) and Eucalyptus grandis and
E. citriodora plantations on patterns of epigeic insect
richness, abundance and diversity in the state of Minas Gerais,
Brazil.
METHODOLOGY
The study was conducted over an eight-day period
beginning on July 31 st 2000. For each different forest type,
three separate sites were randomly chosen and then nine pitfall
traps were set in each for a total of eighty-one traps. Insect
samples were collected after 96 hours, dried and identified to
species. ANOVA and Chi 2 statistical analysis was then performed
on the collected data.
RESULTS
1450 individual insects in 151 different species
and 10 orders were found after 96 hours. Overall, diversity,
richness, evenness and abundance differences showed no significant
difference between habitats, although patterns varied according to
species, order and habitat.
DISCUSSION
The results
do not support the hypothesis that Eucalyptus plantations support
a less diverse epigeic insect community than natural forests due
to the fact that they have lower flora diversity. However, more
singleton species were caught in the degraded forest, which
suggests that this habitat is potentially more diverse although
further research is needed to prove this postulation.
The contribution of each order to the overall
species composition in each habitat suggests that all three forest
types supported a similar community. These results indicate that
cultivation of E. grandis and E. citriodora near
fragments of remaining or regenerated forest allows the settlement
of epigeic arthropod communities that can be as abundant and
diverse as in their natural environment.
This is encouraging for future conservation
action that combines the socio-economic benefits of commercial
plantations, with the ecological benefits of biodiversity. It is
important to realize that the ability of these plantations to
support forest fauna is substantially enhanced by proper forest
management, introduction of native vegetation under the
plantations and by the connecting of plantations to remnants of
native forest.
REFERENCES
Andow D.A., 1991. Vegetational Diversity and
Arthropod Population Response. Annu. Rev. Entomol.
36 :561-86
Eyre S.R. 1967. Vegetation and Soil: a world
picture. 2 nd Ed. Edward Arnold Ltd.
Gaston K.J.m., Lawton J.H., 1988, Feb 25.
Patterns in the distribution and abundance of insect populations. Nature. 331: 789-811
Gonclaves-Alvim S.J., Fernandes G.W., 2001.
Biodiversity of galling insects: historical, community and habitat
effects in four neotropical savannas. Biodivers. Conserv.
10(1): 79-98
Romero-Alcaraz E., Avila J.M., 2000. Landscape
heterogeneity in relation to variation in epigaeic beetle
diversity of a Mediterranean ecosystem. Implications for
conservation. Biodivers. Conserv. 9(7):
985-1005
