GIS-based tool for planning applications of herbicide/nutrient to minimize export to waterways, Queensland, Australia

Abstract

Best management practice for Pinus plantations requires controlled use of introduced chemicals at key stages of forest development. Of specific concern is the potential impact on waterways and hence, there is a need for optimum timing of such treatments. Hydrological processes such as overland flow are significant within plantations as they can trigger the mobilization of soil additives such as herbicides or nutrients, especially during high rainfall events.

Preliminary investigations show that a GIS-based approach can be an effective tool in planning such treatments. The site selected for the assessment is a small catchment located in tropical north Queensland. The area which was previously grazing land was covered in tropical pasture grass and treated with simazine in preparation for plantation. The GIS approach incorporated morphological features (elevation and slope of the terrain), drainage system features and characteristics of soil (erodability, profiles and depth to the restrictive layer). The model was a multiple criteria evaluation (MCE) of weighted parameters and provided guidance in relation to the vulnerability of forestry compartments to water logging and consequently, to overland flow and export of soil additives. The findings of the model were supported by field-based observations and water quality measurements.

The topographical and pedological data used in this analysis are now routinely collected from an area which is being prepared for plantation, so this MCE method can be applied to new logging areas. In addition, the approach can be adapted to assess any other environmentally significant forestry activities and/or represent a precursor for localized hydrological modeling.