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Organic soils on Mt. Sprent, south west Tasmania : an analysis of correlations with local climate, microtopography and vegetation

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Bridle, Kerry Lynn (1992) Organic soils on Mt. Sprent, south west Tasmania : an analysis of correlations with local climate, microtopography and vegetation. Unspecified thesis, University of Tasmania.

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Abstract

Limited data are available pertaining to the peat soils on south west
Tasmanian mountains or on the variability of peat soils over the lowland
to alpine environmental gradient. This thesis describes organic soils on
Mt. Sprent, a 'typical' mountain, in south west Tasmania and analyses
their relationships with climate, vegetation and topography.
Climate data were collected using data loggers which recorded maximum
and minimum air and surface temperatures, and relative humidity over
a 30 month period. Rain gauges were located close to the data loggers.
The climatic equipment was at four sites, at different altitudes ranging
from 509 m to 1059 m.
Vegetation data were collected along altitudinal and topographic
gradients, using a cover/abundance measure for 25 m 2 quadrats. The
altitudinal data were collected for every 10 m increase in altitude, while
the topographic data were collected along a grid system of transects laid
out at four sites on the mountain.
Soils data were collected along the same topographic transects as the
vegetation data. Soil depths were determined in the field, while physical
properties were determined in the field and the laboratory.
Other environmental data were collected along the altitudinal and the
topographic gradients. A total of 34 water table wells were located on the
mountain, at each of the four topographic study sites and at the climatic
stations.
Peat soils in south west Tasmania are shallow, with an average depth of
30 cm. Three types of peat were recognised: fibrous, intermediate and
muck. These vary in their moisture content, organic content, degree of
humification and depth. Where more than one peat type was found in a
profile, shallow fibrous peats overlaid intermediate which in turn
overlaid deeper muck peats.
Peat depth, moisture content and organic content decrease with altitude
inferring climatic influences on the processes of peat formation and
decay. Rainfall and relative humidity were found to be more than adequate to support peat accumulation. The temperatures at the base of
the mountain were higher than those reported in the literature for
optimum peat formation. However, these temperatures were offset by
very high rainfall and relative humidity values. By using evaporation
data from a nearby village (12 km to the north east) and solar radiation
values for the summit, evaporation rates for the mountain during
summer were estimated. When compared to rainfall for the same period
there was a moisture deficit at each station for February.
Vegetation varies with altitude and along topographic gradients.
Buttongrass moorland, alpine heathland and alpine sedgeland occur in
an altitudinal sequence. The deepest soils are found under the lowland
buttongrass moorland vegetation, and the shallowest soils occur under
the alpine vegetation. The four vegetation groups coincided with the
four soil groups.
The amount of organic matter in the surface horizon was significantly
related to vegetation type at two of the four sites, while soil depth related
to vegetation type at three sites. Slope is an important correlate of peat
depth at two of the four sites, while rock cover is important at three sites.
The mean and modal water table depths are correlated with plant
community distributions and the pH of the surface and lower soil
horizons.
Factors affecting peat formation viz, depth and physical properties are
interrelated to such an extent that it is difficult to determine the affects of
a single factor. On the mountain, deeper peats occur at lower altitudes, in
waterlogged conditions, and under buttongrass moorland vegetation.
Fibrous peats are found under moorland, woody and alpine vegetation
types in relatively well-drained areas. Reddish-brown fibrous peats occur
under woody vegetation while buttongrass tends to produce black fibrous
peats. Muck peats are found in areas of impeded drainage.
Higher temperatures experienced at lower altitudes may be offset to some
extent by higher rainfall. A decrease in peat depth with altitude infers
that climate affects the process of peat formation by affecting peat
accumulation rates. A precipitation deficit during the summer months
may be responsible for the shallow nature of the peats. Alternatively fire
history and the relatively low productivity of the vegetation may also
account for the shallow soils.

Item Type: Thesis (Unspecified)
Keywords: Soils, Peat soils
Copyright Holders: The Author
Copyright Information:

Copyright 1992 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.Env.St.)--University of Tasmania, 1994. Includes bibliographical references (leaves 130-140)

Date Deposited: 25 Nov 2014 00:44
Last Modified: 21 Jun 2016 01:32
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