1. Effects of Organic Retention and Management on Nitrogen Flux in a Coarse, Glacial Outwash Soil at Matlock, WA. A.B. Adams, Rob Harrison, Cindy Flint (Uni. of Washington), Stephen Schoenhultz (Oregon State Uni.), Tim Harrington (USDA Forest Service PNWRS – Olympia), Randall Greggs (Green Diamond Resource Co.), and Mike Mosman and Jeff Madsen (Port Blakely Tree Farms, LP) A COLLABORATIVE STUDY

2. INTRODUCTION One of 3 sites that can be treated as independent studies: –Fall River (soil N pool > 13,000 kg/ha) –Molalla (~ 6000 kg/ha N) –Matlock (~3000 kg/ha N) Three levels of woody debris manipulation with or without competing vegetation control (3 x 2 design) Treatments applied to 0.3 ha plots (50 x 60 m)

3. OBJECTIVES OF STUDY To quantify effects of logging debris levels & competing vegetation on flux (nutrients, toxins, etc.) and its impact on ground water quality. To determine if differences in flux explains differences in Doug-fir growth rates (e.g., mineralization of organic N into forms favorable to tree assimilation).

4. RESIDUAL O HORIZONS SMALL A Bw C GROVE SOIL SERIES COARSE, GLACIAL OUTWASH

5. WEATHER DATA IS COLLECTED ON-SITE; FOR EVAPOTRANSPIRATION USE AIR TEMP. @ 25cm & DAILY PPT. FROM TIPPING BUCKET AVERAGED MONTHLY A FENCE WAS BUILT AROUND THE STUDY AREA

6. LTSP MATLOCK PLOTMAP

7. MANAGEMENT TREATMENTS SECOND GROWTH DOUG-FIR FOREST (FOREST) STEM ONLY–NO VEGETATION CONTROL (BO-NVC) STEM ONLY–VEGETATION CONTROL (BO-VC) WHOLE-TREE–NO VEGETATION CONTROL (WT-NVC) WHOLE-TREE – VEGETATION CONTROL (WT-VC)

8. ADJACENT SECOND GROWTH FOREST WAS LEFT STANDING AND SERVED AS A CONTROL 4 FOREST PLOTS HERE

9. BOLES (STEMS) ONLY WERE REMOVED WITH NO VEGETATION CONTROL (BO-NVC)

10. WHOLE TREES WERE REMOVED WITH NO VEGETATION CONTROL (WT-NVC)

11. WHOLE TREES WERE REMOVED (DISTANT PLOT) OR BOLES ONLY HARVESTED WITH VEGETATION CONTROL AT BOTH (WT-VC & BO-VC) WT-VC BO-VC

12. GROVE SOIL SERIES Two lysimeters (20 cm & 100 cm) negative tension lysimeters were installed at each plot to measure flux of dissolved nitrogen and carbon in the soil water. Lysimeters are offset to avoid 20 cm lysimeter interferring with flow of water to 100 cm ceramic cup.

13. BASIS FOR LYSIMETER DEPTHS 20 cm is depth at which plants absorb nutrients. 100 cm is depth at which solutes are considered leached from system.

14. NO 3 NH 4 Dissolved Organic Nitrogen (DON) Total N Dissolved Organic Carbon (DOC) Water samples are taken to our soilslab and analyzed for (milligrams/L):

15. EVAPOTRANSPIRATION MODEL IS USED TO CALCULATE FLUX

16. NO3-N CONCENTRATIONS AT 20 cm

17. NO3-N CONCENTRATIONS AT 100 cm

18. We measure concentration (mg/L) of water sample, but concentration is not very meaningful unless we know the volume (cm/month) of water that is flowing through the soil. Concentration and volume are used to calulate flux (kg/ha). Flux values allow comparison between nutrient pools. Can use flux to compare leaching differences with WT vs. BO vs. Forest and NVC with VC.

19. NO3-N FLUX AT 20 cm

20. NO3-N FLUX AT 100cm

21. 13 month NO3-N flux (kg/ha) Treatment-20 cm-100 cm BO-VC2820.5 WT-VC1313.5 WT-NVC1.514 BO-NVC21 FOREST21.5

23. INTERPRETATION OF RESULTS NO3 is the major N component leached BO-VC is highest because there are no plants to absorb NO3 and some mineralization of debris WT-VCis second highest because there are no plants to absorb NO3 WT-NVC is low at 20 cm because of plant absorption, but high at 100 cm for unknown reasons (unsettled lysimeters) BO-NVC and Forest have low leaching rates due to plant uptake

24. SUMMARY 1)STUDY ALLOWS US TO CALCULATE THE VARIOUS LEVELS OF NUTRIENTS AND THEIR STABILITY IN DIFFERENT ECOSYSTEM COMPARTMENTS 2) RESULTS WILL ALLOW MANAGERS TO CONSIDER THE EFFECT OF DIFFERENT LEVELS OF LOGGING ON NUTRIENT POOLS AND PRODUCTIVITY 3) RESULTS CAN BE COMPARED WITH FALL RIVER AND MOLALLA