ForestStand 300 kg N /ha ForestFloor 104 kg N /ha ForestFloor 243 kg N /ha Soil 9800 kg N /ha Litterfall 9.7 kg N /ha/yr U ptake 5.3 kg N /ha/yr Leaching 5.1 kg N /ha/yr U ptake 24.1 kg N /ha/yr Leaching 21.4 kg N /ha/yr Litterfall 29.4 kg N /ha/yr Responsive Stand U nresponsive Stand Soil 1960 kg N /ha Hypotheses: •Soil nitrogen content is negatively correlated with N fertilizer response (Figure 1). •Sites where soil moisture is low enough to limit transpiration will not be able to utilize N fertilization. •Sites with high LAI will not respond to N fertilization. Predicting Nitrogen Fertilizer Response in Douglas-fir Plantations Kim Littke SMC , Rob Harrison SMC , Dave Briggs SMC , Scott Holub WY , Doug Maguire OSU , Darlene Zabowski UW Materials and Methods: •Select 48 circular plots (80 m^2) in a stand with uniform slope and aspect (Figure 3). •Pair trees according to the best matches for the DBH and live crown height. •Fertilize one tree of each pair with 227 kg N/ha. •Determine LAI, elevation, slope, aspect, and slope shape. •Collect precipitation using rain gauges. •Measure soil moisture and temperature at different temperatures. •Sample soil for bulk density and nutrient content to 1 meter. Sites: •15-25 year old Douglas- fir stands in British Columbia, Oregon, and Washington (Figure 2). •Located in Sitka spruce and western hemlock vegetation zones. •Range of landform, elevation, and position on slope. •Range of parent materials. 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. •This study will attempt to determine soil and non- soil factors that best predict N fertilization response. Figure 2. Current Paired Tree Study locations in the Pacific Northwest. Parent materials are labeled as follows: Glacial, Sedimentary, Igneous. Soil Nitrogen Content (kg/ha) by Installation Air Temperature by Installation Figure 3. Paired Tree Treatment Plots on a 15 m Grid Figure 1. Nitrogen Cycles in Stands Expected to be Responsive and Unresponsive to N Fertilization 5 4 2 3 6 11 10 8 9 12 17 16 14 15 18 23 22 20 21 24 1 7 13 19 25 29 28 26 27 30 10 m eters 15 m eters Preliminary Results: Determining Differences between Installations Relative Humidity by Installation DBH (cm) Range by Installation Soil Moisture Content (m 3 /m 3 ) at 5 cm by Installation Soil Moisture Content (m 3 /m 3 ) at 30 cm by Installation 35 30 25 20 15 10 DBH 8 4 0 Frequency 8 4 0 8 4 0 8 4 0 8 4 0 8 4 0 8 4 0 35 30 25 20 15 10 8 4 0 829 828 826 825 824 823 822 821 Installation

Hypotheses: Soil nitrogen content is negatively correlated with N fertilizer response (Figure 1)

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Predicting Nitrogen Fertilizer Response in Douglas-fir Plantations. Kim Littke SMC , Rob Harrison SMC , Dave Briggs SMC , Scott Holub WY , Doug Maguire OSU , Darlene Zabowski UW. Sites: 15-25 year old Douglas-fir stands in British Columbia, Oregon, and Washington (Figure 2). - PowerPoint PPT Presentation

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Page 1: Hypotheses: Soil nitrogen content is negatively correlated with N fertilizer response (Figure 1)

Forest Stand300 kg N/ha

Forest Floor104 kg N/ha

Forest Floor243 kg N/ha

Soil9800 kg N/ha

Litterfall9.7 kg N/ha/yr

Uptake5.3 kg N/ha/yr

Leaching5.1 kg N/ha/yr

Uptake24.1 kg N/ha/yr

Leaching21.4 kg N/ha/yr

Litterfall29.4 kg N/ha/yr

Responsive Stand Unresponsive Stand

Soil1960 kg N/ha

Hypotheses:

•Soil nitrogen content is negatively correlated with N fertilizer response (Figure 1).

•Sites where soil moisture is low enough to limit transpiration will not be able to utilize N fertilization.

•Sites with high LAI will not respond to N fertilization.

•.

Predicting Nitrogen Fertilizer Response in Douglas-fir Plantations

Kim LittkeSMC, Rob HarrisonSMC, Dave BriggsSMC, Scott HolubWY, Doug MaguireOSU, Darlene ZabowskiUW

Materials and Methods:

•Select 48 circular plots (80 m^2) in a stand with uniform slope and aspect (Figure 3).

•Pair trees according to the best matches for the DBH and live crown height.

•Fertilize one tree of each pair with 227 kg N/ha.

•Determine LAI, elevation, slope, aspect, and slope shape.

•Collect precipitation using rain gauges.

•Measure soil moisture and temperature at different temperatures.

•Sample soil for bulk density and nutrient content to 1 meter.

•Sample known area of forest floor.

•Use a pole pruner to collect terminal flush and all current year lateral branches.

Sites:

•15-25 year old Douglas-fir stands in British Columbia, Oregon, and Washington (Figure 2).

•Located in Sitka spruce and western hemlock vegetation zones.

•Range of landform, elevation, and position on slope.

•Range of parent materials.

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.

•This study will attempt to determine soil and non-soil factors that best predict N fertilization response.

Figure 2. Current Paired Tree Study locations in the Pacific Northwest. Parent materials are labeled as follows: Glacial, Sedimentary, Igneous.

Soil Nitrogen Content (kg/ha) by Installation

Air Temperature by Installation

Figure 3. Paired Tree Treatment Plots on a 15 m Grid

Figure 1. Nitrogen Cycles in Stands Expected to be Responsive and Unresponsive to N Fertilization

542 3 6

11108 9 12

171614 15 18

232220 21 24

25 292826 27 30