Transcript Estimating Response of Douglas

Estimating Response of
Douglas-fir to Urea in Western
Oregon & Washington
By: Eric Sucre
M.S. Thesis Defense
Outline
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Fertilization History and Background
Research Objectives
Locations of Study Sites
Site Descriptives
Brief Description of Experimental Design & Sampling
Methodology
Soil & Site Properties Examined
Statistical Model for Calculating % Response
Significant Chemical And Physical Soil Property Differences
Regression Models
Conclusions
Background
•Regional Forest Nutrition Research Project-RFNRP
•Lake Shawnigan Study in British Columbia
•Stand Management Cooperative (SMC)
•>55 hectares of forests fertilized annually
•Fertilizers Typically Used:
1) Urea ([NH2 ]2CO)
2) Ammonium Nitrate (NH4NO3)
3) Biosolids
Background cont……
•Nitrogen Pools in Pacific Northwest Soils
•Total Nitrogen vs. Available Nitrogen
•Mineralization Rates
•Potential Negative Effects of N Fertilization
•Response Time for Douglas-fir Varies
•Predictors for Douglas-fir Response to N Fertilization:
1) C:N ratio & Total N
2) Foliar SO4-S
3) Genotypes
4) Site Index
An Example in the PNW
•2000-4000 kg ha-1 of Total N
•1-2% Mineralization Rate
•20 to 80 kg ha-1 of Available N per year
• Fertilizer Rate of 224 to 448 kg ha-1
•Approximately 25% of total goes to Biomass Increment
•Typically 10% to 20% of Added Fertilizer Enters Trees
•Where does the remaining fertilizer go?
Forest Nitrogen Cycling Process Representing
Major Fates and Effects of N Fertilization
(Nason and Myrold, 1992)
Factors Influencing Timing of Fertilization
1) Time of Year
2) Temperature
3) Wind Speeds
4) Precipitation Patterns
Project Objectives
1. Assess Relative % Response for Total
Volume and 4-year PAI
2. Test for differences between site, stand
and soil variables
3. Examine relationships between
%Response and site, stand and soil
variables
Locations of SMC Type I Fertilized Research Installations
Site Descriptives
Experimental Design
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Six 0.4 hectare Douglas-fir plots per installation were
examined for this study.
• 3 pairs of fertilized and non-fertilized plots with different
initial stocking levels were compared to each other.
1) ISPHA Fertilized vs. ISPHA Non-fertilized
2) ISPHA/2 Fertilized vs. ISPHA/2 Non-fertilized
3) ISPHA/4 Fertilized vs. ISPHA/4 Non-fertilized
ISPHA
ISPHA/2
ISPHA/4
Pretreatment Conditions
Density Management Regimes for Plots
Examined within Each Installation
{
{
{
ISPHA, Repeated thinning: RD55->RD35, RD55->RD40,
subsequent RD60->RD40
ISPHA, Repeated thinning: RD55->RD35, RD55->RD40, subsequent
RD60->RD40, fertilized with 224 kg N ha-1 as urea every 4 years
ISPHA/2, Minimal thinning: RD55->RD35, no further thinning
ISPHA/2, Minimal thinning: RD55->RD35, no further thinning,
fertilized with 224 kg N ha-1 as urea every 4 years
ISPHA/4, No further thinning
ISPHA/4, No further thinning, fertilized 224 kg N ha-1 as urea every 4
years
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 Forest Floor
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▪ Mineral Soil
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Sampling points for soil and forest floor in SMC Type 1 plots.
Soil & Site Properties Used in Stepwise
Regression Analysis
• Mean Annual Precipitation
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Elevation
% Slope
Relative Density (RD)
Quadratic Mean Diameter (QMD)
bulk density (Db)
• pH
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Total C & N
%C & %N
C:N ratio
cation exchange capacity (CEC)*
Inorganic nitrogen (NO3- and NH4+)*
*Mineral Soil only
Statistical Model
• yijk = µ + αi + γj + αγij + β1x1ijk + β2x2ijk + β3x3ijk + єijk
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yijk
µ
αi
γj
αγij
β
x1ijk
x2ijk
x3ijk
= is total volume & 4-yr PAI for the fertilization level i, thinning j
= is overall average of D.F. volume
= is the fixed effect of the i-th fertilizer regime
= is the fixed effect of j-th thinning regime
= is the interaction effect of the i-th fertilizer & j-th thinning regime
= is the slope of volume vs. various covariates
= is Site Index for given plot/installation
= is ISPHA before treatment
= is Breast Height Age of plot before treatment
Total Volume & 4-yr PAI relative response for each Density Management
Regime 4-yrs following the 1st Treatment
Total Volume & 4-yr PAI relative response for each Density Management
Regime 4-yrs following the 2nd Treatment
Total Volume & 4-yr PAI relative response for each Density Management
Regime 4-yrs following the 3rd Treatment
ANCOVA by Treatment Intervals
H.L. Allen, 2002
Significant Chemical And Physical
Soil Property Differences
Unstandardized Residuals (Observed - Predicted)
of 4-yr PAI (m3 ha-1 yr-1)
Best related independent soil variable in regards to fertilization
response after the third treatment interval for the ISPHA plots.
80
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40
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-20
-40
-60
5
10
15
20
NH4+ concentration (mg kg-1)
Adj. R2= .622
Y= -57.066 +.001(NH4+ (30-50cm))
p < .001
25
30
Unstandardized Residuals (Observed - Predicted)
of total volume (m3 ha-1)
Best related independent stand variable in regards to fertilization
response after the third treatment interval for the ISPHA/2 plots.
120
100
80
60
40
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-20
-40
-60
-80
-100
4.0
4.5
5.0
5.5
6.0
6.5
RD (BA QMD-1/2)
Adj. R2= .712
Y= -238.22 +41.24RD
p = <.001
7.0
7.5
8.0
Conclusions
• Thinning effects were significant across all
treatment intervals.
• 4-yr PAI was significant during the first 2
treatment intervals, but insignificant during the
latest interval
• Longer Fertilization Periods (8 years)
• RD most influential variable
• Significant contribution of soil variables to
regression equations
Acknowledgements
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Committee Members
SMC Cooperative Members for Funding
Fellow Soil Grad Students
Dongsen Xue
SMC Staff
Questions/Comments
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