Fuel manipulation with herbicide treatments to reduce fire hazard in young pine (Pinus elliottii × P. caribaea) plantations in south-east Queensland, Australia

Abstract

Fuel manipulation with herbicide treatments to reduce fire hazard in young pine (Pinus elliottii 3 P. caribaea) plantations in south-east Queensland, Australia Abstract. Wildfire represents a major risk to pine plantations. This risk is particularly great for young plantations (generally less than 10 m in height) where prescribed fire cannot be used to manipulate fuel biomass, and where flammable grasses are abundant in the understorey. We report results from a replicated field experiment designed to determine the effects of two rates of glyphosate (450 g L À1 ) application, two extents of application (inter-row only and inter-row and row) with applications being applied once or twice, on understorey fine fuel biomass, fuel structure and composition in south-east Queensland, Australia. Two herbicide applications (,9 months apart) were more effective than a once-off treatment for reducing standing biomass, grass continuity, grass height, percentage grass dry weight and the density of shrubs. In addition, the 6-L ha À1 rate of application was more effective than the 3-L ha À1 rate of application in periodically reducing grass continuity and shrub density in the inter-rows and in reducing standing biomass in the tree rows, and application in the inter-rows and rows significantly reduced shrub density relative to the inter-row-only application. Herbicide treatment in the inter-rows and rows is likely to be useful for managing fuels before prescribed fire in young pine plantations because such treatment minimised tree scorch height during prescribed burns. Further, herbicide treatments had no adverse effects on plantation trees, and in some cases tree growth was enhanced by treatments. However, the effectiveness of herbicide treatments in reducing the risk of tree damage or mortality under wildfire conditions remains untested.

A New Approach to Estimate Fuel Budget and Wildfire Hazard Assessment in Commercial Plantations Using Drone-Based Photogrammetry and Image Analysis

“…In response, the agroforestry industry has expanded to meet the growing commercial demand for a plantation product that is deemed to be sustainable and the result of responsible environmental practices [3,4]. In south-east Queensland, plantation trees can take up to 25 years to reach commercial maturity [5], and consequently, large amounts of capital are invested in an agricultural industry that is slow to produce returns on investment. During this time, the crop faces a myriad of potential threats including drought, floods, pests and fire, any of which could lead to a total loss of monies invested [6].…”

“…Consequently, there is an increased need for intervention to reduce the risk of intense wildfires developing from ignition events occurring during fire-favourable weather conditions by reducing the available ground-level fuels [30,31]. Fuel load reductions primarily using controlled hazard reduction burns have long been used as the primary method of mitigating this risk [32,33], but in commercial forestry, fuel load management can also be in the form of chemical or mechanical reduction [5,34]. Fuel reduction burns to reduce the amount of available understory fuel by burning during the cooler seasons, with the aim being to reduce understory volume and alter the understory structure without damaging the tree crowns of taller vegetation.…”