Estimating Response of Douglas-fir to Urea in Western Oregon & Washington

1. Estimating Response of Douglas-fir to Urea in Western Oregon & Washington By: Eric Sucre M.S. Thesis Defense

2. Outline • Fertilization History and Background • Research Objectives • Locations of Study Sites • Site Descriptives • Brief Description of Experimental Design & Sampling Methodology • Soil & Site Properties Examined • Statistical Model for Calculating % Response • Significant Chemical And Physical Soil Property Differences • Regression Models • Conclusions

3. Background • Regional Forest Nutrition Research Project-RFNRP • Lake Shawnigan Study in British Columbia • Stand Management Cooperative (SMC) • >55 hectares of forests fertilized annually • Fertilizers Typically Used: • 1) Urea ([NH2 ]2CO) • 2) Ammonium Nitrate (NH4NO3) • 3) Biosolids

4. Background cont…… • Nitrogen Pools in Pacific Northwest Soils • Total Nitrogen vs. Available Nitrogen • Mineralization Rates • Potential Negative Effects of N Fertilization • Response Time for Douglas-fir Varies • Predictors for Douglas-fir Response to N Fertilization: • 1) C:N ratio & Total N • 2) Foliar SO4-S • 3) Genotypes • 4) Site Index

5. An Example in the PNW • 2000-4000 kg ha-1 of Total N • 1-2% Mineralization Rate • 20 to 80 kg ha-1 of Available N per year • Fertilizer Rate of 224 to 448 kg ha-1 • Approximately 25% of total goes to Biomass Increment • Typically 10% to 20% of Added Fertilizer Enters Trees • Where does the remaining fertilizer go?

6. Forest Nitrogen Cycling Process Representing Major Fates and Effects of N Fertilization (Nason and Myrold, 1992)

7. Factors Influencing Timing of Fertilization 1) Time of Year 2) Temperature 3) Wind Speeds 4) Precipitation Patterns

8. Project Objectives • Assess Relative % Response for Total Volume and 4-year PAI • Test for differences between site, stand and soil variables • Examine relationships between %Response and site, stand and soil variables

9. Locations of SMC Type I Fertilized Research Installations

10. Site Descriptives

11. Experimental Design • Six 0.4 hectare Douglas-fir plots per installation were examined for this study. • 3 pairs of fertilized and non-fertilized plots with different initial stocking levels were compared to each other. 1) ISPHA Fertilized vs. ISPHA Non-fertilized 2) ISPHA/2 Fertilized vs. ISPHA/2 Non-fertilized 3) ISPHA/4 Fertilized vs. ISPHA/4 Non-fertilized

12. ISPHA

13. ISPHA/2

14. ISPHA/4

15. Pretreatment Conditions

16. Density Management Regimes for Plots Examined within Each Installation • ISPHA, Repeated thinning: RD55->RD35, RD55->RD40, • subsequent RD60->RD40 • ISPHA, Repeated thinning: RD55->RD35, RD55->RD40, subsequent • RD60->RD40, fertilized with 224 kg N ha-1 as urea every 4 years • ISPHA/2, Minimal thinning: RD55->RD35, no further thinning • ISPHA/2, Minimal thinning: RD55->RD35, no further thinning, • fertilized with 224 kg N ha-1 as urea every 4 years • ISPHA/4, No further thinning • ISPHA/4, No further thinning, fertilized 224 kg N ha-1 as urea every 4 years { { {

17. Sampling points for soil and forest floor in SMC Type 1 plots.

18. Soil & Site Properties Used in Stepwise Regression Analysis • Mean Annual Precipitation • Elevation • % Slope • Relative Density (RD) • Quadratic Mean Diameter (QMD) • bulk density (Db) • pH • Total C & N • %C & %N • C:N ratio • cation exchange capacity (CEC)* • Inorganic nitrogen (NO3- and NH4+)* *Mineral Soil only

19. Statistical Model • yijk = µ + αi + γj + αγij + β1x1ijk + β2x2ijk+ β3x3ijk + єijk • yijk = is total volume & 4-yr PAI for the fertilization level i, thinning j • µ = is overall average of D.F. volume • αi = is the fixed effect of the i-th fertilizer regime • γj = is the fixed effect of j-th thinning regime • αγij = is the interaction effect of the i-th fertilizer & j-th thinning regime • β = is the slope of volume vs. various covariates • x1ijk = is Site Index for given plot/installation • x2ijk = is ISPHA before treatment • x3ijk = is Breast Height Age of plot before treatment

20. Total Volume & 4-yr PAI relative response for each Density Management Regime 4-yrs following the 1st Treatment

21. Total Volume & 4-yr PAI relative response for each Density Management Regime 4-yrs following the 2nd Treatment

22. Total Volume & 4-yr PAI relative response for each Density Management Regime 4-yrs following the 3rd Treatment

23. ANCOVA by Treatment Intervals

24. H.L. Allen, 2002

25. Significant Chemical And Physical Soil Property Differences

26. Adj. R2= .622 Y= -57.066 +.001(NH4+ (30-50cm)) p < .001

27. Adj. R2= .712 Y= -238.22 +41.24RD p = <.001

29. Conclusions • Thinning effects were significant across all treatment intervals. • 4-yr PAI was significant during the first 2 treatment intervals, but insignificant during the latest interval • Longer Fertilization Periods (8 years) • RD most influential variable • Significant contribution of soil variables to regression equations

30. Acknowledgements • Committee Members • SMC Cooperative Members for Funding • Fellow Soil Grad Students • Dongsen Xue • SMC Staff

31. Questions/Comments ??????