Modelling Forest Growth and Carbon Dynamics: TRIPLEX Model Development and Applications Changhui Peng (www.crc.uqam.ca) Université du Quebec à Montreal (UQAM) Laboratoire de modélisation écologique et de science du carbone (Eco-MSC) Ecological Modelling and Carbon Science Laboratory (Eco-MCS)
OUTLINE Overview of TRIPLEX model TRIPLEX development and testing -TRIPLEX1.0 -TRIPLEX-Flux Challenges Ahead for TRIPLEX model family development
Major Challenges for Sustainable Forest Management Sustaining forest ecosystem productivity Mitigating and/or adapting to the effects of global change Improving carbon sequestration potential of forests
Forest Simulation Models Empirical Models Mechanistic Models Growth and Yield Models Succession Models Process Models Hybrid Models Increasing ability to predict growth under changed future conditions Increasing model simulation options and flexibilities Description moving towards Explanation (Peng, 2000)
TRIPLEX: A generic hybrid model for predicting forest growth and carbon and nitrogen dynamics Developed based on well-established models: 3-PG (Landsberg and Waring, 1997) TREEDYN3.0 (Bossel, 1996) CENTURY4.0 (Parton et al., 1987, 1993) Bridges the gap between forest growth and yield and process-based C balance models Can be used for: 1) Making forest management decisions (e.g., G&Y prediction) 2) Quantifying forest carbon budgets (Peng et al. 2002, Ecol. Model) 3) Assessing the effects of climate change on forest ecosystems
Key Features of TRIPLEX1.0: Driving variables (main inputs): Monthly climate data; tree & stand variables, LAI, soil texture, geo-location Mass balances: C, N, and water pools and fluxes fully balanced Time step: Monthly C flux and allocation calculation; annual tree growth, C, N, and water budget Outputs: H, DBH, BA, volume, NPP, biomass, soil C, N, and water dynamics Modelling strategy: OOP (objective-oriented programming - C++) and model reuse approaches
TRIPLEX1.0 Framework Pool: Process: Precipitation Atmospheric CO2 Solar radiation Moisture N limitation GPP N Store C Allocation Increment C Leafs N Roots Wood C N C N Height Diameter Soil water Temperature Litter fall C N Volume Basal Area Structure Metabolic Disturbance N mineralization C N C N Mortality Active (C, N) Thinning Runoff Decomposition (C, N) Slow (C, N) Harvesting Tree number Leaching Passive (C, N) Wood production
One Case Study Location: Longlac (Kimberly Clark Ltd.) Forest type: Jack pine ( Pinus banksiana Lamb.) SA BO Longlac Ontario 12 PSP (0.08ha each) MT CT BO: Boreal; CT: Cool Temperate; MT: Moderate Temperate; SA: Subartic
Calibration and Validation for TRIPLEX Model We have 6 consecutive measurements (every 5 yr) for DBH, H, tree density (1952-1982) Use first measurements (1952) to calibrate the TRIPLEX model Use the other 5 measurements to validate (1957-1982)
Comparison of Simulations and Observations (solid diagonal is the 1:1 line; N=60)
Simulated Relative Errors for Stand Age (=[simulation - observation]/observation) ±10% ±15% ±20% ±25%
Study area: Lake Abitibi Model Forest Ontario Canada Longitude and Latitude : -80.7, 48.8 Temperature: 1.2 o C Precipitation: 814.8 mm
Method Simulation Model TRIPLEX model Outputs Dynamics Biomass NPP Soil C & N DBH Height Volume C N Spatial Distribution... GIS ArcView
Model validation 40 (a) Height Observation (m) Observation (cm) 30 20 10 0 40 30 20 10 y = 0.9041x + 0.7511 r 2 = 0.92, n = 49 0 10 20 30 40 Simulation (m) (b) DBH y = 0.9931x - 0.2171 r 2 = 0.95, n = 49 32 black spruce, 9 jack pine, 8 trembling aspen plots (measured in 1995) 0 0 10 20 30 40 Simulation (cm) TRIPLEX vs. Forest Inventory TRIPLEX vs. PSP
Total Height (m) DBH (cm) 2000
Simulated Basal Area (m2/ha) Simulated Total Volume (m3/ha) 2000
Simulated Biomass (t ha -1 ) in 2000 Simulated NPP (tc ha -1 yr -1 ) in 2000
C update: 3.0 C release: 1.0 Harvesting C About 0.1 Biomass C pool: 55.5 Aboveground: 42.2 Belowground: 13.3 Unit: Mt C Litter and Soil C pool: 83.7 LAMF forest ecosystem C budget of LAMF forest ecosystem in 2000: Net carbon balance (NCB) = 2.0 Mt C
New TRIPLEX-Flux Model Development TRIPLEX1.0 (big leaf, monthly) TRIPLEX-Flux (two leaves, daily) CO2 Stoma Cell O2 CO2 Energy Light reactions Calvin cycle H2O Sugar C N Shaded leaf Sunlit leaf Water
Model Testing for 2 Flux tower sites 110 yrs black spruce 75 yrs mixedwood (Fluxnet-Canada)
Model Validation OBS Flux Tower g C m -2 30 min -1 0.4 0.3 0.2 0.1 0.0-0.1-0.2-0.3 Field data from NSA-OBS-FLXTR in Jul 1996 NEP Simulated NEP (gc /m 2 /30m in) 0.4 0.2 0-0.2 R 2 = 0.7304-0.4-0.4-0.2 0.0 0.2 0.4-0.4 Observed NEP (gc /m 2 /30min) 183 184 185 186 187 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 214 Day of year Daily Simulation using TRIPLEX-flux (Zhou et al, 2008)
Boreal Mixedwood Site (Ontario) 0.4 0.3 0.2 0.1 0 R 2 = 0.77-0.1-0.2-0.2-0.1 0.0 0.1 0.2 0.3 0.4 (Sun et al., 2008) Observed NEE (gc m -2 30m in -1 ) 0.40 May Ontario station in 2004 EC (O M W ) Sim ulated NEE 0.20 0.00-0.20 122 123 125 127 129 130 132 134 136 137 139 141 143 144 146 148 150 151 Day of ye ar NEE (g C m -2 30min -1 ) Simulated NEE (gc m -2 30min -1 )
Challenges for TRIPLEX Development Continued testing of the model s ability to simulate NPP, belowground biomass, soil C, N and water (BOREAS sites as well as Canada-Fluxnet) Developing submodels (TRIPLEX-Fire, TRIPLEX-DOC, TRIPLEX-harvest) to include the effects of CO 2 fertilization, ecosystem disturbances (fire, harvesting, insects, disease), land use, and forest management planning Scaling up linking TRIPLEX with remote sensing and GIS (estimated PAR, LAI through NDVI, etc )
TRIPLEX-Management Pool: Process: Precipitation Atmospheric CO2 Solar radiation Moisture N limitation GPP N Store C Allocation Increment C Leafs N Roots Wood C N C N Height Diameter Soil water Temperature Litter fall C N Volume Basal Area Structure Metabolic Disturbance N mineralization C N C N Mortality Active (C, N) Thinning Runoff Decomposition (C, N) Slow (C, N) Harvesting Tree number Leaching Passive (C, N) Wood production
Looking for new MS, or Ph.D. or PDF students Please contact: Dr. Changhui Peng by E-mail: peng.changhui@uqam.ca 20008 NSERC Strategic Grant: Modelling the Impacts of Thinning on the Structure, Biomass, Carbon Sequestration and Economics Value of Jack Pine Stands ( Changhui Peng and Tony Zhang) 2008 FQRNT en Group: Effets interactifs des changements climatiques et des feux de forêts sur la croissance forestière, la succession, et le bilan de carbone dans les écosystèmes de la forêt boréale du Québec ( C. Peng, J.P. Blanchet, Y. Bergeron)
Uncertainty
Fire Module Developments FireStarter FireIntensity FireMortality TRIPLEX-Fire Model FireEmission
Acknowledgements Canada Research Chair Program Fluxnet-Canada Research Network (FCRN) Canadian Foundation for Climate and Atmospheric Science (CFCAS) Natural Science and Engineering Research Council (NSERC) Drs. Qinglai Dang, Jinxun Liu, Xiaolu Zhou, UQAM/ Lakehead University Mrs. Susan Parton, Lake Abitibi Model Forest
Challenge: Validation Validation is testing a model to see how well it predicts. (How well does the model capture the structure, controls, and dynamics of a real forest ecosystem). First questions is: what variable do we want to validate (test)? The second question is finding adequate data.
Data for Validating Forest Model Greenhouse or experimental data Tree growth plots (PSP, TSP) Forest inventory Flux tower (CO 2, NPP, NEP etc..) Remote Sensing (NDVI-NPP) Paleoecological data (tree-ring, pollen)
Comparison of Averaged Simulations and Observations - Aboveground Biomass (Hegyi, 1972)
Simulated Soil carbon (tc ha -1 ) in 2000 Soil texture
NPP Spatial Distribution at Landscape Level Fig. 4 The comparison between NPP (t C ha-1 yr-1) simulations at landscape (a) and remote sensing (b) levels for the LAMF in 1995. (a) was based on the TRIPLEX model simulation for 1995 (averaged 3.28 tc ha-1 yr-1, SD=0.79), and (b) was converted using spatial data from Liu et al. (2002) for 1994 (averaged 3.08 tc ha-1 yr-1, SD=1.15). The grid size is 3x3 km. (a) TRIPLEX (Zhou et al, 2005) (b) Remote Sensing (Liu et al, 2002) Kappa Statistic (k) = 0.55 Good agreement if 0.55<K<0.7
Problems of Applying Process Models in Forest Management Most Process models (FOEST-BGC, PnET, TEM, CENTURY etc..) are not designed to predict stand characteristic (such as BA, DBH, H and annual mortality), and thus the outputs are not directly useful in management planning too complex and require a large amount of information beyond what is readily available to forest managers lacking a user-friendly modeling interface and their documentation is insufficient, making them difficult for forest managers to use (Peng et al., 2002, Ecological Modelling)
One Solution: Hybrid Models The development of hybrid models, which combine physiological process models with more traditional growth and yield models, will be specially useful for integrating physiological processes with larger scale stand dynamics processes (Martin, Johnsen, and White, 2001. Forest Science, 47: 21-28)