Centre for Plant & Water Science - Central Queensland University

Centre for Plant & Water Science 2008 Annual Report
NATIVE GROUND COVER SPECIES FOR REVEGETATION UNDER
HIGH VOLTAGE POWERLINES IN QUEENSLAND
SUMMARY
The practice of using tubestock in revegetation programs is becoming very popular.
However, records of very low plant survival have been reported in such revegetation
programs. Survival of plants in revegetated sites largely depends on how well the potting
mix allows the water to enter into the root zone during establishment stage. This character
is determined by the physical and chemical properties of potting media used in raising the
seedlings. Forty one commercially available potting media that were sold in the markets
were therefore tested along with two soil samples for their lack of ability to attract water
from surrounding environment, the hydrophobicity. By using the Water Droplet Penetration
Test (WDPT), hydrophobicity of those media was determined and the media categorised into
five classes. Out of 43 media tested 28% of the media were classified as extreme, 35% as
severe, 21% as strong, 11% as slight and 5% as non-hydrophobic.
Construction of powerlines in Queensland is increasing at the rate of 3.4% per annum, to
service increasing demand of electricity for various developmental activities such as mining,
agriculture, industries, beef production, smelting and tourism. Extending the powerlines
means more tree clearing or disturbance of already existing and adapted vegetation in the
extended areas. The clearance of the existing plant communities greatly accelerates the
process of soil erosion, loss of biodiversity and the rate of spread of invasive weeds. For
revegetation of such degraded landscapes, a few exotic species have been used at high costs.
Due to their invasive nature these species have gradually replaced valuable native
biodiversity. As these powerlines pass through diverse bioregions of Queensland, use of
exotic species in revegetation will not be a meaningful solution. Therefore, the proposed
project will identify native ground cover species for successful revegetation of land under
high voltage powerlines. The study will also develop suitable agronomic practices for
survival and long term sustainability of established species.
The most critical stage in revegetation program is the establishment phase. Use of nursery
raised seedlings has become very popular in revegetation programs. Seedlings are mostly
established in the rainy season with or without irrigation. Plant survival rate in such
activities is very low and has negatively affected the revegetation program significantly. In
nurseries, seedlings are raised in different potting media. The nature of potting media used in
the nursery affects the ability of plants to extract available moisture from the surrounding
soil once they are transplanted in the field. To determine the hydrophobic properties of
media, we purchased 41 commercial media from shops in Rockhampton. Two soils (black
and red) were also used as controls. By using the Water Droplet Penetration Test (WDPT),
the degree of hydrophobicity of collected media was determined. Three drops of deionised
water were placed on top of potting media at 1 cm apart (Fig 1). The time taken (in seconds)
for the water drop to penetrate the media was recorded (Lal and Shukla 2004). Based on this
time, the media were categorised into the following groups.
36000 seconds: extremely hydrophobic
Results (Fig 2) show that all potting media were hydrophobic to some degree, and the only
two media that had no hydrophobicity were the two soils (black and red) that were used as
controls (5% of the tested media). More than 50% of the media tested were severely to
Page 51