Soil pollution with heavy metals is an ever growing concern due to the potential threat to food safety and detrimental effects on human and animal health. The uptake of metals by plants and ingestion by humans depends on their bioavailability in soil. Since landuse has tremendous influence on soil properties, it can also affect the availability of heavy metals. In order to assess the effect of changing landuse on bioavailability of Cu, Mn, Fe and Zn, a total of 116 surface soil samples were collected from three landuses: rangeland (RL), needle leaf (NL) and broad leaf (BL) forest (all land uses were under rangeland before 1966). The available (DTPA extractable) and total Cu, Mn, Fe and Zn concentrations, pH, organic matter, calcium carbonate and soil texture were measured using standard methods. Statistical analyses (e.g. correlation and ANOVA) indicated a significant difference in available form of all heavy metal (Cu, Mn and Zn) concentrations except Fe among the landuses. Soil organic matter was greatly influenced by the landuse type. A positive correlation between available form of heavy metals (especially Zn) and organic matter was also observed. Spatial distribution (determined using geostatistical methods) of available Cu and Mn was very similar within the region. Availability of these two elements was mainly affected by the amount of calcium carbonate present within the region. In contrast, available Zn showed a different spatial distribution and its availability was mostly under the influence of soil organic matter. Availability of Fe was affected by the amount of calcium carbonate and soil organic matter present within the study area. Information on the spatial distribution of heavy metals as influenced by soil properties which in turn controlled by landuses is important in understanding the extent and severity of soil pollution and its potential impacts in the converted parklands.

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