1. Understanding Site-Specific Factors Affecting the Nutrient Demands and Response to Fertilizer by Douglas-fir Center for Advanced Forestry Systems 2010 Meeting Kim Littke Rob Harrison David Briggs University of Washington

2. Rationale Nitrogen fertilization is a common practice in Douglas-fir forests of the Pacific Northwest The Regional Forest Nutrition Research Project studied the effect of N fertilization over western Washington and Oregon However, growth response to N fertilization was widely variable No site and soil factors have been confirmed as response predictors for Douglas-fir Center for Advanced Forestry Systems 2010 Meeting

3. Objectives Test soil variables including bulk density, nutrient pools, temperature, and moisture Record non-soil variables such as site index, LAI, elevation, slope, precipitation, air temperature, and relative humidity Determine which factors can predict N fertilizer response Focus on variables that are easily obtained Center for Advanced Forestry Systems 2010 Meeting

4. Experimental Plan 15-30 year-old Douglas-fir stands in British Columbia, Oregon, and Washington Range of landform, elevation, and slope Measure DBH, height, and crown height of 48 dominant Douglas-fir Pair trees according to the best matches for DBH and crown height Fertilize one tree per pair with 224 kg N/ha Select up to 20 pairs per installation Center for Advanced Forestry Systems 2010 Meeting

5. Paired Tree Design Center for Advanced Forestry Systems 2010 Meeting

6. Paired Tree Installations Center for Advanced Forestry Systems 2010 Meeting Red Markers – Glacial parent material Green Markers – Sedimentary parent material Blue Markers – Igneous parent material

7. Progress 60 Douglas-fir installations  2 ponderosa pine  25 glacial  19 sedimentary  18 igneous 59 installations have soil sampled and weather stations installed Complete weather station data for one growing season for 31 installations Six installations with two-year growth data Center for Advanced Forestry Systems 2010 Meeting

8. Site Quality Center for Advanced Forestry Systems 2010 Meeting

9. Soil Nitrogen to 1 Meter Center for Advanced Forestry Systems 2010 Meeting Glacial North to South Sedimentary

10. Basal Area Growth Percent Center for Advanced Forestry Systems 2010 Meeting

11. Height Growth Percent Center for Advanced Forestry Systems 2010 Meeting

12. Volume Growth Percent Center for Advanced Forestry Systems 2010 Meeting

13. Foliage Area after fertilization Center for Advanced Forestry Systems 2010 Meeting ControlFertilized

14. Foliar N Concentration Center for Advanced Forestry Systems 2010 Meeting

15. Basal Area Growth Response Center for Advanced Forestry Systems 2010 Meeting

16. Height Growth Response Center for Advanced Forestry Systems 2010 Meeting

17. Timeline Two-year growth data for 28 installations fall 2010  Foliage, forest floor, and soil sampling  26 installations will be measured fall 2011 Four-year growth data to be measured 2011, 2012, and 2013 Background soil samples to be finished spring 2010 Weather stations maintained twice yearly Center for Advanced Forestry Systems 2010 Meeting

18. Deliverables and Budget Establishment of Paired Tree Installations throughout the Pacific Northwest Derive a model to predict fertilizer response based on site and soil factors $20,000 for the next year Other support from:  Stand Management Cooperative  Agenda 2020 Center for Advanced Forestry Systems 2010 Meeting

19. total funding $195,078

20. Center for Advanced Forestry Systems 2010 Meeting