understanding site-specific factors affecting the nutrient demands and response to fertilizer by...

Understanding Site-Specific Factors Affecting the Nutrient

Demands and Response to Fertilizer by Douglas-fir

Center for Advanced Forestry Systems 2010 Meeting

Kim LittkeRob HarrisonDavid Briggs

University of Washington

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


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


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


Paired Tree Design


Paired Tree Installations


Red Markers – Glacial parent material

Green Markers – Sedimentary parent material

Blue Markers – Igneous parent material

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 dataCenter for Advanced Forestry Systems

2010 Meeting

10 12 14 16 18 20 22 24 26 2830

35

40

45

50

55

60

65

70

75

80

f(x) = 2.3010285625884 x + 17.095698104463R² = 0.612644140939803

Age at Breast Height

Heig

ht (ft

)

Adna 2

Adna 1

Arrowhead Lake

Oppelt Rd

Cherry Grove 1 Cherry Grove 2

Site Quality


Soil Nitrogen to 1 Meter


0

5000

10000

15000

20000

25000

30000

Arrowhead Lake

Oppelt RdAdna 1Adna 2

Cherry Grove 1

Cherry Grove 2

Soil

Nitr

ogen

Con

tent

(kg

N/h

a)

IgneousGlacialNorth to South

Sedimentary

Basal Area Growth Percent


Cherry Grove 1 Cherry Grove 2 Adna 1 Adna 2 Arrowhead Lake

Oppelt Rd0

5

10

15

20

25

30

35

a

b

Control 224 kg N/haInstallation

Basa

l Are

a Gr

owth

(%)

Height Growth Percent


Oppelt Rd0

2

4

6

8

10

12

14

16

ab

Control 224 kg N/ha

Installation

Heig

ht G

row

th (%

)


Volume Growth Percent



Oppelt Rd0

5

10

15

20

25

30

35

40

45

50a

b

Control 224 kg N/haInstallation

Volu

me

Grow

th (%

)

Foliage Area after fertilization


Control Fertilized

Foliar N Concentration


Control Fertilized1

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

Adna 1Adna 2Arrowhead LakeCherry Grove 1Cherry Grove 2Oppelt Rd

Folia

r Nitr

ogen

Con

cent

ratio

n (%

)

Basal Area Growth Response


8000 9000 10000 11000 12000 13000 14000 15000 16000 17000 18000

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

R² = 0.486277867911935

Soil Nitrogen Content (kg N/ha)

Basa

l Are

a Gr

owth

Res

pons

e (%

)

Height Growth Response


1.25 1.30 1.35 1.40 1.45 1.50 1.55

-0.5

0.0

0.5

1.0

1.5

2.0

R² = 0.736267779847595

Foliar N concentration – Control (%)

Heig

ht G

row

th R

espo

nse

(%)

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


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


total funding $195,078

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