Fourie, AB, Tibbett, M, Worthington, T & King, AE 2008, 'Quantifying the Effect of Substrate Compaction on Root Development in Cover Systems', in AB Fourie, M Tibbett, I Weiersbye & P Dye (eds), Proceedings of the Third International Seminar on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 27-34.
Vegetation is understandably an integral component of the cover systems used on most tailings and waste
rock disposal facilities. The soil in these covers is usually placed and spread using earthmoving equipment
such as trucks, scrapers, dozers and front-end loaders. Trafficking of this equipment can easily result in a
high degree of compaction of the cover soil, which may compromise the ability of roots to develop laterals or
penetrate to adequate depth. Poor root development may curtail the vegetation survival and growth, and
thus reduce the effectiveness of the cover system.
Soil was collected from the stockpile of a candidate cover soil at a tailings storage site in Western Australia.
The soil was compacted according to the relevant Australian Standard in 50 cm long, 10 cm diameter PVC
growth columns. Three compaction configurations were used, namely high, low and stratified, in a
replicated root penetration experiment. Pre-germinated seeds of Acacia celastrifolia were planted into each
column and grown in a temperature regulated glasshouse facility. At 40 days and 60 days after detection of
first growth, soil was extruded from the cylinders and the root architecture defined using a WinRHIZO
scanner and software.
The paper illustrates that the (limited) available literature on the effect of compaction density on root
development is simplistic and can be unnecessarily restrictive if adhered to blindly. The importance of
working within a framework that contextualizes the degree of compaction, such as is used in engineering
earthworks, is shown to be a key factor in interpreting the results of this type of study.
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