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The ecology and management of lumbricid earthworms in the Midlands of Tasmania


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Garnsey, R(Roger) 1994 , 'The ecology and management of lumbricid earthworms in the Midlands of Tasmania', Research Master thesis, University of Tasmania.

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Earthworms have the ability to impart substantial physical, chemical and
biological effects on the soil through their burrowing and casting activities.
Earthworm communities are distributed throughout Tasmania's agricultural soils,
however in the low rainfall region of the Midlands of Tasmania ( < 600 mm
p.a.), earthworm density and species diversity is low. This may be restricting
potential gains in pasture production in the region. The purpose of this study
was to examine the ecology and management of earthworms in the Midlands,
and their effect on pasture production during 1991-1993. The earthworm
Aporrectodea longa was also introduced at two sites in the Midlands to
determine its effects on pasture production. This knowledge can then be utilised
to increase earthworm activity and hence, pasture productivity in the Midlands. Earthworm population dynamics were studied at 14 sites in the Midlands during
1992-1993. Earthworm number and biomass was recorded monthly and found
to be significantly correlated with soil moisture; maximum earthworm activity in
the surface soil was evident during the wetter months of winter and early spring,
followed by an aestivation in the surface and sub-soils during the drier summer
months. The two most abundant earthworm species found in the Midlands were
Aporrectodea caliginosa (maximum of 174.8/m2 or 55.06 g/m2) and A.
trapezoides (86/m2 or 52.03 g/m2), with Octolasion cyaneum (22/m2 or 13.0
g/m2) and Lumbricus rubellus (31/m2 or 13.58 g/m2) combined constituting <
15 % of the total population. However, the behaviour of A. caliginosa to
rainfall and soil texture was contrary to that of A. trapezoides in this study. A.
caliginosa was particularly dependent upon rainfall in the Midlands: population
density, cocoon production and adult development of A. caliginosa was reduced
under low rainfall. The number and biomass of A. caliginosa also tended to be
lower on the sandy soil in this study. In contrast, the density and biomass of A.
trapezoides was unaffected by rainfall between 425-600 mm p.a.; cocoon
production and adult development continued unabated at low rainfall. Density
and biomass of A. trapezoides was similar on all soil types.
The depth of earthworm aestivation was examined during the summers of 1992-
1994 from the same sites used to examine earthworm population dynamics.
Aestivation behaviour of earthworms was similar in each year. Most individuals
were in aestivation at a depth of 150-200 mm, regardless of species, soil
moisture or texture. Smaller aestivating individuals were located nearer the soil
surface, shown by an increase in mean mass of aestivating individuals with
depth. There was a high mortality of up to 60 % for juvenile, and 63 % for adult earthworms associated with summer aestivation in 1993 in the Midlands.
Cocoons did not survive during the summers of 1992 or 1994, but were
recovered in 1993, possibly due to the influence of rainfall during late winter
and early spring.
The influence of ivermectin on earthworm growth and cocoon production was
investigated. The growth and cocoon production of four pasture earthworm
species provided with dung from sheep treated with ivermectin were not
significantly impeded over a five week laboratory study.
Pastures at Oatlands and Perth were chosen in the Midlands to determine the
effects of lime (L), nitrogen (N), organic matter (0) and fertilisers (F), and the
introduction of A. longa, on earthworm numbers and pasture growth. Treatment
application and introduction of A. longa produced contrasting results at Oatlands
and Perth. A. longa increased pasture production at Perth within seven months
by up to 17 %, but had no effect at Oatlands. Application of F and L at
Oatlands increased pasture growth, whilst 0 and L initially decreased pasture
growth at both sites. Numbers of A. trapezoides and A. longa were increased at
Oatlands by L and 0, whilst F increased numbers of A. trapezoides and L.
rubellus. The increase in earthworm numbers in response to treatments appears
to be an indirect response to greater amounts of high N food reserves in the soil.
In contrast, the initially low population density of earthworms at Perth were
further reduced by N and F. The differences in response at Perth and Oatlands
to treatment application and A. longa introduction is discussed in terms of
differences in climate, soil type and pasture composition between sites.

Item Type: Thesis - Research Master
Authors/Creators:Garnsey, R(Roger)
Keywords: Lumbricidae, Earthworms, Lumbricidae, Earthworms
Copyright Holders: The Author
Copyright Information:

Copyright 1994 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Agr.Sc.)--University of Tasmania, 1995. Includes bibliographical references (leaves 113-134)

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