predicting nitrogen fertilizer response in douglas-fir plantations kim littke rob harrison
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![Page 1: Predicting Nitrogen Fertilizer Response in Douglas-fir Plantations Kim Littke Rob Harrison](https://reader035.vdocument.in/reader035/viewer/2022062421/56649d2f5503460f94a07128/html5/thumbnails/1.jpg)
Predicting Nitrogen Fertilizer Response in
Douglas-fir Plantations
Kim LittkeRob Harrison
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Introduction
Nitrogen fertilization is a common practice in forests of the Pacific Northwest
The Regional Forest Nutrition Research Project was implemented in the 1960s to study the effect of N fertilization over western Washington and Oregon
However, growth response to N fertilization was widely variable
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Introduction
Growth response appears to be related to forest N pools and fluxes
Large N pools and fluxes will probably be unresponsive to N fertilization
Small N pools and fluxes should be responsive– Unless water or other nutrients are limiting
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Hypotheses
Soil nitrogen content down to one meter is the biggest predictor of growth response to N fertilization
Low soil water availability hinders growth response in stands that should otherwise respond to N fertilization
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Sites
15-25 year old Douglas-fir stands in British Columbia, Oregon, and Washington
Located in Sitka spruce and western hemlock vegetation zones
Range of landform, elevation, and position on slope
Sedimentary, igneous, and glacial parent materials
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Paired Tree Installations
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Add Beyond Nitrogen Installations
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Plot Treatment Design
10 meters
15 meters
542 3 6
11108 9 12
171614 15 18
232220 21 24
1
7
13
19
25 292826 27 30
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Materials and Methods
Measure height, DBH, height to live crown, and known environmental gradients
Pair trees by most similar DBH and crown height
Fertilize one tree of each pair with 224 kg N/ha
Determine LAI, elevation, slope, aspect, and slope shape
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Sampling Methods
Background Measure precipitation using rain gauges Measure soil moisture and temperature Determine soil N and C content to one
meter Determine C and N content of litter
Post-fertilization Sample soil under trees for input of N Collect current foliage
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Nutrient Analysis
Determine soil bulk density and rock content
Soil and litter will be analyzed for nutrient concentrations
Total nutrients estimated to one meter
Foliar weight and nutrition will be determined
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Tree Pairings
6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.015.0
25.0
35.0
45.0
55.0
65.0
Steel Creek
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
DBH (in)
Cro
wn
He
igh
t (f
t)
1
3
4
5
2
6
15
9
14
17
18
7
8
10
11
12
13
16
19
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Soil PitsArmstrong JanickiSand
Clarks Creek DFClay
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Sensor Installation
Soil moisture and temperature sensors placed horizontally at 5 and 50 cm
Air temperature and humidity at 15 cm above the forest floor
Rain gauge 25 cm above forest floor
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Soil Moisture
11/3/08 12/23/08 2/11/09 4/2/09 5/22/090.000
0.050
0.100
0.150
0.200
0.250
0.300
0.350
0.400
Clayey 5 cmClayey 50 cmSandy 5 cmSandy 50 cm
Date
Soil M
ois
ture
(m
3/m
3)
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Field Capacity vs. Wilting Point
0 5 10 15 20 25 30 35 400
5
10
15
20
25
30
35
40f(x) = 0.916796224319822 x + 7.47159911160467R² = 0.779803775528582
AllLinear (All)ClayLoamySandySandy loam
Wilting Point (m3/m3)
Fie
ld C
ap
aci
ty (
m3
/m3
)
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Soil Nitrogen to 1 Meter
0
5000
10000
15000
20000
25000
30000
Nit
rog
en
Co
nte
nt
(kg
N/h
a)
GlacialNorth to South
Sedimentary Igneous
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0
100
200
300
400
500
Carb
on
C
on
ten
t (M
g C
/ha)
Soil Carbon to 1 Meter
GlacialNorth to South
Sedimentary Igneous
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Statistics
Sedimentary soils significantly greater soil C and N content (p=0.025 and 0.001).
Glacial soils significantly greater soil CN ratio (p=0.003)
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Current Work
34 installations fertilized since spring 2009
56 total installationsSoil sampled and sensors at 53
installationsTwo year measurements this fall
for 6 installations
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Future work
Develop model to predict which stands will respond to N fertilization
Range of background N and water availability
Previous growth– PAI– Earlywood to latewood ratio
Foliage size and weight– Differences over water and N availability– Change after fertilization
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Questions?