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Estimation of Leaf Area Index & Evapotranspiration Simulation in Douglas-Fir Forests

Investigating methods to estimate leaf area index (LAI) & simulate evapotranspiration (ET) in Douglas-fir forests. Study compares LAI estimation techniques & validates simulated ET using soil moisture data.

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Estimation of Leaf Area Index & Evapotranspiration Simulation in Douglas-Fir Forests

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  1. Estimation of Leaf Area Index and Simulation of Evapotranspiration for Intensively Managed Douglas-fir Forests Nicole Rogers Department of Forest Engineering, Resources & Management Oregon State University Western Mensurationists Meeting 2013

  2. Background • Productive forests • Douglas-fir • Site index and basal area • What improves/constrains productivity estimates?

  3. Where Our Research Fits • Evapotranspiration • Provides a link between water use and photosynthesis • Study individual components of ET equations • LAI • Validate with soil moisture

  4. Objectives • Objective 1: Compare methods for estimating Leaf Area Index • Objective 2: Simulate evapotranspiration • Penman-Monteith •  Objective 3: Validate simulated ET • Soil moisture drawdown

  5. Study Site Panther Creek Watershed • 2580 ha • 37 soil plots- NRCS data • Plot and watershed weather stations

  6. Objective 1: LAI Comparisons • LI-COR 2200 Plant Canopy Analyzer • Sapwood area allometrics • Foliage mass

  7. Methods: Statistical Analysis • Conversion of sapwood area to leaf area at crown base • Model branch and tree level foliage mass • Literature and Panther Creek specific

  8. Results: Sapwood Area Waring Ratio : 0.54 Panther Creek Ratio : 0.66 Plot

  9. Results: Foliage Mass

  10. Results: Foliage Mass

  11. Results: Methods Comparison

  12. Summary Regional estimates from destructive sampling provide the most accurate estimate of LAI

  13. Objective 3: Soil Moisture Water Water ET Dry Soil Dry Soil Soil Soil Early Summer Late Summer

  14. Data: Climate

  15. Data: Soils

  16. Methods: Statistical Analysis • Daily linear regression VWC= f(Depth) • Average soil moisture • Growing season water loss

  17. Results: Daily Regression July September

  18. Results: Water Loss

  19. Results: Water Loss

  20. Summary Wide spectrum in soil moisture and water loss over the growing season by plot

  21. Next Steps • Compare Penman-Monteith forms • Compare estimated ET against soil moisture ET • Predict drawdown as a function of PM variables

  22. Conclusions • ET factors into Douglas-fir productivity • ET and it’s components are dynamic • Site specific processes into productivity

  23. Thank you! • Doug Maguire • Doug Mainwaring • Maguire staff • David Marshall • Robin Rose • Panther Creek collaborators • Peavy106

  24. Equations

  25. Foliage Mass Parameter Est.

  26. Plot Attributes

  27. Methods: Li-Cor • Soil research plots • Douglas-fir BA 80% or greater • A and B readings

  28. Methods: Sapwood Allometrics • 15 to 20 trees at each plot • DBH and sapwood thickness • Convert to sapwood area • Sapwood area crown base to leaf area • Leaf area to LAI

  29. Methods: Destructive Sampling • 22 trees • Approximately 10th, 50th, and 90th percentile by DBH • Branch and tree level foliage mass to LA • Measurements of sapwood area crown base

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