School of Ecosystem and Forest Sciences - Theses

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    Soil physical and chemical properties under Casuarina cunninghamiana Miq. (river sheoak) shade trees in northern Victoria
    Bino, Bire ( 1994)
    Casuarina cunninghamiana Miq. (river sheoak) is an Australian native tree with a natural distribution throughout eastern Australia. It is one of the three Australian casuarinas being widely grown in many countries as an exotic multipurpose tree. This thesis reports on a study of soil physical and chemical properties under C. cunninghamiana shade trees in northern Victoria. The study aimed to assess whether the presence of the trees had any effect on soil properties (bulk density, organic matter and chemical properties) by comparing soil under the canopy with soil under the adjacent open pasture. The study was conducted at the Department of Agriculture Rutherglen research station which has a mean annual rainfall of 590 mm and moderately to strongly acid Rutherglen loam soil. The study involves two main treatments: under the tree canopy and under open pasture. The treatments were replicated in each quarter of the sample plot containing nine sample trees. Soil samples were collected only once for soil bulk density, organic matter and chemical properties. The results showed that the presence of C. cunninghamiana shade trees did not improve soil bulk density, organic matter content and chemical properties of the surface soil (0-15 cm depth) under the canopy. Soil bulk density and organic matter content under the canopy were not significantly different (1.12 g cm-3 and 4.44% respectively) compared with open pasture (1.19 g cm-3 and 4.07% respectively). Soil pH and total nitrogen were significantly less (pH 4.20 and 0.08% respectively) under the canopy compared with under the open pasture (pH 4.48 and 0.01% respectively). Available phosphorus and exchangeable potassium levels under the canopy (2.09 ?g/g and 4.22 cmol kg-1 respectively) were not significantly different compared with open pasture (0.773 .Lglg and 4.88 cmol kg- I respectively). The lack of improvement in soil bulk density and nutrients under the canopy is probably due to the inherent acidity of the soil. This may make conditions unsuitable for litter breakdown and nitrogen fixation. Low rainfall and seasonal flooding of the study site may also be influencing these soil properties. The results demonstrate that the potential of C. cunninghamiana to improve soil properties may be variable depending on the site conditions.