Forty-five acid sulfatc topsoil samples (depth < 0.5 m) from 15 soil coreswere collected from 11 locations along the New South Wales coast, Australia. There was an overalltrend for the concentration of the HCl-extr...Forty-five acid sulfatc topsoil samples (depth < 0.5 m) from 15 soil coreswere collected from 11 locations along the New South Wales coast, Australia. There was an overalltrend for the concentration of the HCl-extractable P to increase along with increasing amounts oforganic C and the HCl-extractable trivalent metals in the topsoils of some less-disturbed acidsulfate soils (pH < 4.5). This suggests that inorganic P in these soils probably accumulated viabiological cycling and was retained by complexation with trivalent metals or their oxides andhydroxides. While there was no clear correlation between pH and the water-extractable P, theconcentration of the water-extractable P tended to increase with increasing amounts of theHCl-extractable P. This disagrees with some established models which suggest that the concentrationof solution P in acid soils is independent of total P and decreases with increasing acidity. Thehigh concentration of sulfate present in acid sulfate soils appeared to affect the chemical behaviorof P in these soil systems. Comparison was made between a less disturbed wetland acid sulfate soiland a more intensively disturbed sugarcane acid sulfate soil. The results show that reclamation ofwetland acid sulfate soils for sugarcane production caused a significant decrease in theHCl-extractable P in the topsoil layer as a result of the reduced bio-cycling of phosphorusfollowing sugarcane farming. Simulation experiment shows that addition of hydrated lime had noeffects on the immobilization of retained P in an acid sulfate soil sample within a pH range3.5～4.6. When the pH was raised to above 4.6, soluble P in the soil extracts had a tendency toincrease with increasing pH until the 15th extraction (pH 5.13). This, in combination with the poorpH-soluble P relationship observed from the less-disturbed acid sulfate soils, suggests that solubleP was not clearly pH-dependent in acid sulfate soils with pH < 4.5.展开更多
Soil macroinvertebrates play an important role in sustaining production and biodiversity in Australia＇ s tropical savannas. For example, termites, through their foraging and nesting activities, recycle nutrients and ...Soil macroinvertebrates play an important role in sustaining production and biodiversity in Australia＇ s tropical savannas. For example, termites, through their foraging and nesting activities, recycle nutrients and carbon and produce soil pores that facilitate water infiltration. The challenge ahead is to quantitatively understand the relationships and processes that drive this. What roles do different species and functional groups of macroinvertebrates play in various landscape processes？ What are the effects of different land management practices （e.g., domestic cattle grazing, fire） on these relationships, and the consequences for landscape health？ This paper presents preliminary results from studies in northern Australia, that examine the effects of land condition and domestic cattle grazing on soil macroinvertebrates, and the potential for termites to be used as a tool to restore soil function in degraded areas. In northern Australia, increased degradation seems to be associated with declines in the diversity and activity of macroinvertebrates. Termites appear to be one of the most resilient groups, with some species capable of maintaining activity in degraded landscapes.展开更多
文摘Forty-five acid sulfatc topsoil samples (depth < 0.5 m) from 15 soil coreswere collected from 11 locations along the New South Wales coast, Australia. There was an overalltrend for the concentration of the HCl-extractable P to increase along with increasing amounts oforganic C and the HCl-extractable trivalent metals in the topsoils of some less-disturbed acidsulfate soils (pH < 4.5). This suggests that inorganic P in these soils probably accumulated viabiological cycling and was retained by complexation with trivalent metals or their oxides andhydroxides. While there was no clear correlation between pH and the water-extractable P, theconcentration of the water-extractable P tended to increase with increasing amounts of theHCl-extractable P. This disagrees with some established models which suggest that the concentrationof solution P in acid soils is independent of total P and decreases with increasing acidity. Thehigh concentration of sulfate present in acid sulfate soils appeared to affect the chemical behaviorof P in these soil systems. Comparison was made between a less disturbed wetland acid sulfate soiland a more intensively disturbed sugarcane acid sulfate soil. The results show that reclamation ofwetland acid sulfate soils for sugarcane production caused a significant decrease in theHCl-extractable P in the topsoil layer as a result of the reduced bio-cycling of phosphorusfollowing sugarcane farming. Simulation experiment shows that addition of hydrated lime had noeffects on the immobilization of retained P in an acid sulfate soil sample within a pH range3.5～4.6. When the pH was raised to above 4.6, soluble P in the soil extracts had a tendency toincrease with increasing pH until the 15th extraction (pH 5.13). This, in combination with the poorpH-soluble P relationship observed from the less-disturbed acid sulfate soils, suggests that solubleP was not clearly pH-dependent in acid sulfate soils with pH < 4.5.
文摘Soil macroinvertebrates play an important role in sustaining production and biodiversity in Australia＇ s tropical savannas. For example, termites, through their foraging and nesting activities, recycle nutrients and carbon and produce soil pores that facilitate water infiltration. The challenge ahead is to quantitatively understand the relationships and processes that drive this. What roles do different species and functional groups of macroinvertebrates play in various landscape processes？ What are the effects of different land management practices （e.g., domestic cattle grazing, fire） on these relationships, and the consequences for landscape health？ This paper presents preliminary results from studies in northern Australia, that examine the effects of land condition and domestic cattle grazing on soil macroinvertebrates, and the potential for termites to be used as a tool to restore soil function in degraded areas. In northern Australia, increased degradation seems to be associated with declines in the diversity and activity of macroinvertebrates. Termites appear to be one of the most resilient groups, with some species capable of maintaining activity in degraded landscapes.
