Effects of Organic Retention and Management on Nitrogen Flux in a Coarse, Glacial Outwash Soil at Matlock, WA.

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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
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INTRODUCTION

• One of 3 sites that can be treated as independent
  studies
• Fall River (soil N pool gt 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)

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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).

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HORIZONS
RESIDUAL O
SMALL A
Bw
GROVE SOIL SERIES COARSE, GLACIAL OUTWASH
C
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WEATHER DATA IS COLLECTED ON-SITE FOR
EVAPOTRANSPIRATION USE AIR TEMP. _at_ 25cm DAILY
PPT. FROM TIPPING BUCKET AVERAGED MONTHLY
A FENCE WAS BUILT AROUND THE STUDY AREA
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LTSP MATLOCK PLOTMAP
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MANAGEMENT TREATMENTS

• SECOND GROWTH DOUG-FIR FOREST (FOREST)
• STEM ONLYNO VEGETATION CONTROL (BO-NVC)
• STEM ONLYVEGETATION CONTROL (BO-VC)
• WHOLE-TREENO VEGETATION CONTROL
• (WT-NVC)
• WHOLE-TREE VEGETATION CONTROL (WT-VC)

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4 FOREST PLOTS HERE
ADJACENT SECOND GROWTH FOREST WAS LEFT STANDING
AND SERVED AS A CONTROL
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BOLES (STEMS) ONLY WERE REMOVED WITH NO
VEGETATION CONTROL (BO-NVC)
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WHOLE TREES WERE REMOVED WITH NO VEGETATION
CONTROL (WT-NVC)
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WT-VC
BO-VC
WHOLE TREES WERE REMOVED (DISTANT PLOT) OR BOLES
ONLY HARVESTED WITH VEGETATION CONTROL AT BOTH
(WT-VC BO-VC)
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GROVE SOIL SERIES
Lysimeters are offset to avoid 20 cm lysimeter
interferring with flow of water to 100 cm ceramic
cup.
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.
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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.

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Water samples are taken to our soilslab and
analyzed for (milligrams/L)

• NO3
• NH4
• Dissolved Organic Nitrogen (DON)
• Total N
• Dissolved Organic Carbon (DOC)

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EVAPOTRANSPIRATION MODEL IS USED TO CALCULATE FLUX
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NO3-N CONCENTRATIONS AT 20 cm
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NO3-N CONCENTRATIONS AT 100 cm
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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.
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NO3-N FLUX AT 20 cm
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NO3-N FLUX AT 100cm
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13 month NO3-N flux (kg/ha)
Treatment -20 cm -100 cm
BO-VC 28 20.5
WT-VC 13 13.5
WT-NVC 1.5 14
BO-NVC 2 1
FOREST 2 1.5
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(No Transcript)
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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

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• SUMMARY
• 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