A field method for statewide ground-truthing of a spatial pasture growth model

Abstract

This paper describes an innovative method, commonly referred to as ‘spider mapping’, that allows pasture biomass and related data to be collected over large areas in a timely and efficient manner. Spider mapping was developed initially to collect data to allow calibration and validation of a spatial and temporal pasture growth model operating across Queensland on a 5 km grid basis. Two field officers made over 220 000 estimates and collected about 1300 samples of pasture biomass between January 1994 and August 1995. A number of selected biomass samples were analysed for nitrogen, phosphorus and carbon content. In addition, data were also collected on foliage projective cover and tree basal area for a range of woodland communities and both variables compared with mean long-term Normalised Difference Vegetation Index values derived from a time series of National Oceanographic and Atmospheric Administration satellite imagery. Both variables were strongly related to the satellite data with overstorey foliage projective cover having the strongest non-linear correlation (r2 = 0.91). The method described here is currently being used in related work in the rangelands of New South Wales, South Australia, Western Australia and the Northern Territory.

AUSLEM (AUStralian Land Erodibility Model): A tool for identifying wind erosion hazard in Australia

“…Aussie-GRASS produces 5 × 5 km spatial simulations of the GRASP (grass production) pasture growth model (Hasset et al, 2000). The model uses daily inputs of climatic conditions (rainfall, temperature, solar radiation, evaporation, etc.…”

Stand biomass estimation method by canopy coverage for application to remote sensing in an arid area of Western Australia

“…In a pasture area in Queensland, Australia, a relatively high correlation between vegetation cover or canopy cover and vegetation indices with a coefficient of determination in excess of 0.9 has been reported (Hassett et al, 2000). This report utilized time series of satellite images and adopted the spider mapping method.…”

Interacting effects of vegetation, soils and management on the sensitivity of Australian savanna rangelands to climate change

“…Tree Basal Area (m 2 ha −1 ) 0 -12 Hassett et al 2000). For the exclosure studies, GRASP was shown to account for a high proportion (r 2 =0.84 to 0.97) of both within-year and between-year variation in pasture yields over 5 years across five sites near Gayndah ( Fig.…”