Hybrid modelling of plantation crops

1. Hybrid modelling of plantation crops Euan Mason University of Canterbury

2. Outline • Hybrid models • Current hybrid modelling projects at the School of Forestry • Stand level hybrid growth and yield • Hybrid initial growth models

3. Potential for hybrid models • Geographic Information Systems • More known about each site and stand • Variation in growth pattern from site to site • Less need for regional models • Variation in weather from year to year • Predicting the past • Variation in monthly climate offers monthly predictions • Climate change may affect growth patterns • Kyoto protocol • Carbon storage explicit in some models

4. An example “hybrid” model 3-PG Model (Landsberg & Waring 1997) Allocation varies with fertility

5. Application of 3-PG 25-year old experiment

6. Potential issues with 3-PG • Allocation of C is derived from allometry • Recursiveness, compounded errors • Over parametarisation • Fertility is inadequately represented • Stand and stem geometry are not modelled • Circularity • DBH->Carbon, Carbon->DBH • Measurement of LAI may partially solve this

7. Current HM projects at SoF • Physiological hybrid Initial Growth Model • Comparisons between hybrid and traditional G & Y models • Modelling effects of nutrition • Modelling effects of spacing and genotype on corewood properties • National hybrid model for P. radiata • Modelling clonal stands

8. Physiological hybrid IGM

9. Comparisons of hybrid models • Guy Pinjuv, PhD candidate • Canterbury estate, highly variable sites • Comparison of a range of hybrids • Traditional growth and yield • 3-PG • Several alternatives in between • Evaluate fit and utility • Two types of validation required

10. Modelling effects of nutrition • Horacio Bown, PhD candidate • Development of fertility modifier for hybrid models • Long-term goal • Controlled environment • Field experiments

11. Corewood stiffness vs actual stocking & clone – J.P. Lasserre

12. Modelling clonal stands • Rajesh Sharma • What changes are needed when modelling for clonal forest management? • Potential for hybrid modelling to provide genotype-specific models • Large plot clonal experiment - SPBL • 10 clones, pure and mixed clone blocks • Planted 1993 • Variation in growth, form, wood quality • Interchange in dominance • Competition with self or other genotypes • Local genotype-dependent individual tree model • Risk

13. National hybrid model for radiata pine • Postdoctoral Fellow • Dr Helge Dzierzon • Can hybrid modelling remove need for regions? • Are hybrids more effective that traditional methods within regions? • How much local sensitivity do we lose by adopting a national hybrid model? • PSP data from 13 companies • Monthly weather data from climate stations, with local offsets • Elevation and soils from GIS

14. Weather stations used • Reasonable data coverage from 1960 to 2005 • Stations over all New Zealand • Data availability for each station is heterogeneous

15. Landcare Research Soil Layer • Aim: Investigate growth patterns over New Zealand • Format: • ESRI polygon layer • 8 Soil Classes (NZSCORD) • 67 Subclasses (NZSC) covered by PSPs

16. Results for MTH using LCR Layer – the ultimate regional approach • Regression for SC: • MSE=2.03 • N: 3202 • N classes: 26 • Residuals for SC • From 20955 to 13182

17. Results for G using LCR Layer • Regression of SC: • MSE=9.70 • N: 3202 • N classes: 26 Residuals for SC • From 360825 to 302916 • Residuals of Simulation run • Mean: 356021 • Std: 9154

18. An idea among many • Time = accumulated light • Use 3-PG type quantum efficiency modifiers to accumulate potentiallyused light • Use sigmoidal difference equations as usual, fitted to PSP data • Avoids some of 3-PG’s problems • Compounded errors • Allocation of C • Overparametarisation • Lack of stand geometry

19. An idea among many • Estimate genetic components of seasonal variations in primary and secondary growth • Different radiation sums for primary and secondary growth

20. Seasonal growth in dbh (red), height (yellow) and 3-PG predictions (blue). (Tennent 1986)

21. An idea among many • Climatic variables as well as stocking and radiation sum estimates in mortality model • To what extent can temporal variation in climatic influences inform us about influences on crop growth and mortality of spatial variation in climate?

22. An idea among many • Compatible stand, distribution & individual tree projection systems • Models that represent height vs basal area growth as functions of site variables • Models that respond to climatic and local weather variation • Models specific to each site • Models that naturally provide growth estimates within years

23. Preliminary Example – P. radiata in Central North Island Von-Bertalanffy-Richards Daytime temp, VPD modifiers Schumacher, daytime temperature modifier

24. MTH: Results using light sum models - Dzierzon • Regression example • MSE: 1.40 • N: 2146 • Residuals: • From 4427.0 to 4118

25. G: Results using light sum models - Dzierzon • Regression Example • MSE: 5.05 • N: 2146 • Residuals: • From 57796 to 54822

26. Light sum initial growth model: Competition for light in R1835/2

27. Future directions • Two fertile strands for forest modelling research • Internal qualities of stems • Physiological hybrids • The University of Canterbury contributes to both • Challenge is to bring the two strands together

28. Future directions • Hybrids may obviate a regional approach to growth and yield • Hybrids may provide an alternative or be complementary to 300 (500) index/Site index approach • Climatic and silvicultural effects may be more easily integrated in hybrid models than in traditional G & Y models • Site conditions mediate use of light

29. Summary • Several key studies in hybrid modelling • Hybrid modelling • More sensitive to local site conditions • Seasonal (monthly) predictions • Reduced need for regions? • Better estimates of growth since last inventory? • Carbon sequestration explicit? • Linkages between mensuration, silviculture and physiology