Veterinary Science Collected Works - Theses
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ItemResponses of tree roots to post-planting waterlogging and soil compaction( 1997)Plants growing in urban soils are frequently subject to waterlogging and changes in soil strength due to compaction and fluctuations in watertables, and variations in texture and bulk density due to the disturbed nature of urban soils. A waterlogging trial was set up to test the ability of recently planted trees to grow new roots under waterlogged conditions and to recover from this period of waterlogging. Corymbia maculata, Lophostemon confertus, Platanus orientalis and Platanus X acerifolia were subjected to a period of waterlogging and then a recovery phase after waterlogging had ceased. Root length was measured at the end of the waterlogging phase, and at the end of the recovery phase. The different species were found to vary considerably in their ability to tolerate and recover from a period of waterlogging. Waterlogging suppressed shoot and root growth in all species trialed. Corymbia maculata, and Platanus orientalis were able to initiate new roots under waterlogged conditions. Platanus X acerifolia and Lophostemon confertus were not able to do this. Compaction trials were set up to test the hypothesis that trees which are able to establish in urban soils will have a higher than average tolerance to soil compaction and to the higher mechanical impedance and soil strength in dry compacted soils. Compaction Trial A tested the ability of the roots of Corymbia maculata, Lophostemon confertus, Corymbia ficifolia and Agonis flexuosa seedlings to penetrate soil cores compacted to bulk density 1.4 and 1.8 Mg/m3 at 13 % gravimetric moisture content. While roots of all species were able to penetrate the soil at the higher bulk density, total root penetration depth was reduced by 60 % across all the species. Compaction Trial B tested the ability of Corymbia maculata and Corymbia ficifolia to penetrate soil compacted at bulk densities 1.4, 1.6 and 1.8 Mg/m3 at two moisture levels, 7 and 10 % gravimetric moisture. At 7 % moisture, both species were able to penetrate soil compacted to 1.4 and i .6 Mg/m3, but neither species was able to successfully penetrate soil compacted to 1.8 Mg/m3. At 10 % moisture, both species were able to penetrate soil compacted to 1.4 and 1.6 Mg/m3. They were also able to successfully penetrate soil compacted to 1.8 Mg/m3, although with significantly less depth of penetration.