Spatial and temporal modelling of pasture and plantation production for integrated catchment planning in south-eastern Australia

This paper describes an assessment of the Lachlan Catchment, in south-eastern Australia, undertaken to develop and apply methods for catchment planning. The GROWEST and Physiological Process for Predicting Growth (3-PG) models were used to model the spatial distribution of primary productivity for temperate pastures and forest plantations, respectively. For both models, spatial estimates of growth were obtained using long-term monthly climatic surfaces with a resolution of 0.01° of latitude and longitude. However, two different approaches were used to model temporal changes in productivity and to investigate the effects of climate variability on the reliability of production over time. Monthly climate surfaces for the period from 1950 to 1999 with a resolution of 0.25° were used to simulate growth for temperate pastures using GROWEST. Tree growth in plantations was simulated using 3-PG with 50 years of monthly climate data at 14 climate stations (sites) within the catchment. tion estimates were then used to examine the reliability of production for both systems and determine areas within the catchment that are most suited to perennial pasture production and those most suited to forest plantations for timber production. There are similarities in the spatial and temporal estimates produced from the different models, but production of temperate pastures is more constrained by low temperatures. While the majority of the catchment is capable of growing pasture, only a small area is capable of high growth rates that are required for commercial timber plantations. Forest plantations are also comparatively more reliable than temperate pastures in the more productive areas of the catchment. The study concludes that the methods for developing spatial and temporal estimates of growth are relevant for integrated catchment planning.