Predicting the water-use of Eucalyptus nitens plantations in ...

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5. Process Model Comparisons Even though the aim of this study was to develop a simple empirical model for water-use prediction, process models such as ProMod (Battaglia and Sands, 1997) and CABALA (Battaglia et al., 2004) can also be used to estimate both the basal area and water-use of plantations in different locations in Tasmania, and thus could possibly be used to test and refine the empirical relationship between these parameters for different regions. 5.1. ProMod ProMod is a simple model that predicts the growth of forest following canopy closure (Battaglia and Sands, 1997). ProMod also predicts water-use based on a crop factor which is a function of soil water content, and water-use efficiency which is a function of vapour pressure deficit. It requires information about plantation species, location, climate and soil. It tabulates results for growth, summarises information about site conditions and charts growth parameters against plantation age. ProMod was run for the Florentine and Forestier sites using the Forestry Tasmania Toolbox (Appendix 1). While ProMod gives annual basal area as an output, it does not give as an output annual water-use. Instead, water-use is given as an average annual rate for the plantation when aged greater than 3 years. Roberts (2011) showed that ProMod basal area estimates were consistent with measurements made in the Florentine Valley. ProMod underestimated basal area for Forestier (20-25 m 2 /ha versus 30 m 2 /ha), however the measurement plot at Forestier was in the most productive part of the plantation, and ProMod is describing the average condition of a plantation in that region. Overall, the estimates of basal area from ProMod appear to be representative of the growth occurring at Florentine and Forestier. This is reassuring given that the ProMod growth models are an important component of the FEM. However, the water-use estimates cannot be properly evaluated in their current form. 5.2. CABALA CABALA is a linked carbon, water and nutrient model designed to be a practical tool to aid forest managers with decision making (Battaglia et al., 2004). CABALA was designed for Eucalyptus globulus, but has been partially parameterised for E. nitens. CABALA was run using detailed regimes for each of the five research plots in the Florentine Valley – including accurate planting dates and local daily weather data (Roberts, 2011). Water-use and growth were over-predicted by CABALA. Even with the revised water-use results from the August 2011 report, CABALA continues to overestimate water-use (Figure 15). This is potentially because CABALA is overestimating the basal area of unthinned forests (Figure 14). Benyon et al. (2009) also found that CABALA overestimated water use in the Green Triangle – particularly for non-water-limited plantations. Roberts (2011) reported that CABALA showed promise for estimating E. nitens basal area and water-use in 22
the Florentine Valley, but that it does need further calibration. Data from the Florentine study were provided to the creators of CABALA in November 2011 to help facilitate further calibration. At this stage, therefore, neither CABALA nor ProMod can lend further value to the modelling of E. nitens water-use; however they both have the capacity to do so in the future by changing the output format (ProMod) or better calibrating the growth model (CABALA). Basal Area (m 2 /ha) 50 45 40 35 30 25 20 15 10 5 0 0 2 4 6 Age (years) 8 10 12 Figure 14. Plantation age and measured basal area (Florentine study, blue diamonds) or predicted basal area for each plot from CABALA. 23 Measured 20A 23C 21AT 21AC 22D
Page 1 and 2: RESOURCES PROJECT NUMBER: PNC143.08
Page 3 and 4: Publication: Predicting the water-u
Page 5 and 6: A simple empirical model (below) wa
Page 7 and 8: 1. Introduction Plantation developm
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Page 13 and 14: Water Use (mm/yr) 08 09 10 08 09 10
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Page 17 and 18: 3. Forestier Plantation Water-use A
Page 19 and 20: 3.2. Weather Station An automatic w
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Page 25 and 26: 4. Comparison of Florentine and For
Page 27: triangle), Florentine thinned (blue
Page 31 and 32: 6. Final water-use function The rec
Page 33 and 34: Wood Volume Standing Wood Volume Cu
Page 35 and 36: In addition to producing the charts
Page 37 and 38: Figure 20. FEM screenshot showing v
Page 39 and 40: Table 4. Schedule of activities tha
Page 41 and 42: single Forestier site of age 6 -7 y
Page 43 and 44: • FEMs represent the best availab
Page 45 and 46: 11. References Battaglia, M., and S
Page 47 and 48: Macfarlane, C., Bond, C., White, D.
Page 49 and 50: 12. Acknowledgements This research
Page 51 and 52: Site productivity FFT v4.158 Saved
Page 53 and 54: SQ is Site Quality Vol is the sum o
Page 55 and 56: Growth: Age MDH BA Vol MAI (yr) (m)

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