Estimations of Phosphorus Loss Due to Logging of Douglas-fir in a 2nd Growth Temperate Forest in The Pacific Northwest

By: Dustin Miller and Jonathon TuckerEnvironmental Analysis 2014-2015

Image source: http://wak.infobaselearning.com/media/10114/OR-tree.jpg

Douglas-fir (Pseudotsuga menziesii)

• Keystone Species in Pacific Northwest temperate rainforests

• Economically valuable timber species in the PNW

• Large contiguous stands exist in TESC forest

Silviculture and Forest Management in the Pacific Northwest• The 1994 Northwest Forest Plan• Shift from focus on timber output to ecosystem

sustainability on public land • Clear-cut logging still dominant on private land• Previous studies have shown that continuous

management of forests can cause nutrient depletion and reduced productivity (Federer et al. 1989, Blanco 2012)

Phosphorus• Essential to life• Major limiting nutrient• Important role in

driving energy transfer

• Very slow rate of renewal

• Primary sources•Weathering• Dust deposition Image source:: http://

www.inorganicventures.com/element/phosphorus. 2013 Inorganic Ventures, Inc.

Site Description• 2nd growth temperate forest in the

Pacific Northwest• Sampling sites based on EEON plots

and PSME overstory abundance• Other major overstory species:

• Western red cedar (Thuja plicata)• Western hemlock (Tsuga

heterophylla)• Big-leaf maple (Acer

macrophyllum)• Major understory species:

• Salal (Gaultheria shallon)• Sword fern (Polystichum

munitum)• Oregon grape (Mahonia nervosa)

Field Methods• Needles

• Litter collected from beneath drip line

• Stem wood• 10-15cm core collected with an

increment borer• Stem bark

• Vertical incision with knife• Soil o-horizon

• Collected using a 45cm PVC soil corer 25cm from the base of the tree

• Mineral Soil• Collected at depths of 5, 15, 25,

50, and 100cm using a 5cm (r=2.04cm)

Sample Preparation • Oven-dried at 70°C for >24 hours• Homogenized using a ball mill• Wood tissue•Mortar and pestle• Knife

Chemical Analysis• Mineral soil samples•Mehlich-1 extraction (0.05 M HCL & 0.0125 M H2SO4)

• Organic tissue samples• EPA Method 3050b (Conc. HNO3 & 30% H2O2)

• Analyzed for total P using ICP-MS Organic tissue samples mid-digestion

Results of Previous Studies• Compton and Cole, 1998• Tissue (Kjeldahl,

Colorimetric)• 26ppm Stemwood• 171ppm Stembark• 1430ppm Needles

• Soil O-Horizon (Modified Kjeldahl, Colorimetric)• 1060ppm Soil• 240ppm Woody debris

• Mineral Soil Soil (Bray-P)• 154ppm 0-7cm• 10ppm 7-15cm• 6.2ppm 15-30cm• 2.5ppm 30-45cm

• Ponette et al. 2001• Tissue (Combustion,

ICP)• 35ppm Stemwood• 35ppm Stembark• 984ppm Needles

• Mineral Soil Soil (Dyer-P)• 200ppm 0-10cm• 44ppm 40-80cm

Biomass Estimation using Allometric Equations• Equations provided in Jenkins et al. 2003• Equation form 2:

• Equation form 4:

• “a”, “b”, “c”, and “d” are different equation parameters• Took the mean output of four different equations for each tissue type.

Results of Organic Tissue

Total P

(ppm)

 Standar

d

Deviatio

n

Mean

Estimated

Biomass

(kg/ha)

Mean Total P

(kg P/ha)

Stem wood  18.86  ±7.52  97055  1.83

Stem bark  71.14  ±18.18  27046  1.92

Foliage 1342.30  ±337.62  3204  6.93

Soil O-horizon  710.84  ±297.74  2518 17.90

Results of Mineral Soil Bioavailable P Analysis

 

Mean

Bioavailabl

e P (ppm)

Standard

Deviation

Estimated g

P/.02m3

5 cm  415.35 ±256.67  6.08

15 cm  322.47 ±448.04  4.12

25 cm  167.15 ±238.93  3.23

50 cm  63.99 ±69.71  2.11

100 cm  43.79 ±39.86  0.29

Results of Organic Tissue total P Analysis

Results show significant positive correlations between wood P and DBH (p=.0113) and bark P and DBH (p=.0200)

30 40 50 60 70 80 900

102030405060708090

100f(x) = 0.898561329485287 x + 16.0704162431007R² = 0.562020809542352

Bark P vs DBH

Bark P vs DBHLinear (Bark P vs DBH)

30 40 50 60 70 80 900

5

10

15

20

25

30f(x) = 0.387440635518504 x − 4.4692669866665R² = 0.572888996726864

Wood P vs DBH

Wood P vs DBHLinear (Wood P vs DBH)

Mineral Soil P Estimates

0.50.60.70.80.9 1 1.11.21.30

20406080

100120

f(x) = 154.581736205627 x − 97.6683497233521R² = 0.936977825969946

Mean Soil Density vs Depth

Mean Soil Density (g/cm^3) vs Depth (cm)Linear (Mean Soil Density (g/cm^3) vs Depth (cm))

Mean Soil Density (g/cm3)

Dep

th (

cm)

020406080

100120

f(x) = − 35.9219301018003 ln(x) + 217.619556662848R² = 0.865291468291576

f(x) = − 0.197737999678015 x + 79.0520282697609R² = 0.713716931692999

Mean P vs Depth

Mean P vs Depth

Depth (cm)

Mea

n Pl

ant

Avai

labl

e P

(ppm

)

0 100 200 300 400 500 6000

20406080

100120

Estimated Soil Plant AvailableP (ppm)

Dep

th (

cm)

-50 0 50 100 150 200 250 300 350 4000

20

40

60

80

100

120 Estimated Soil Plant AvailableP (ppm)

Dep

th (

cm)

Estimated Total = 1157kg/ha Estimated Total = 1343kg/ha

Discussion• Literature comparison

• Bark and needle concentrations very consistent with prior measurements• O-horizon concentrations lower than expected, possibly due to methodological

differences• Wood concentrations lower than expected

• Old-growth Douglas-fir forests and P sequestration• 3.7kg/ha, or 0.32% of estimated measured P pool, removed in a

stem-only clear-cut harvest.• These results are consistent with predictions made using computer modeling in

Blanco 2012.• Loss of P through slash decomposition and runoff• Further Studies

• Kjeldahl instead of EPA 3050b• K, Ca, Mg• Greater Sample Size• Use of an O2 DRC

Acknowlegments• We would like to thank Carri, Abir, and Clyde for

their guidance, feedback, and patience throughout the year.

• Special thanks to Jenna and Sina for all the help with methods, instrumentation, and equipment

• Kaile and the rest of the SSC staff

Citations• J. Jenkins, D. Chojnacky, L. Heath, R. Birdsey. 2003. Comprehensive

Database of Diameter-based Biomass Regression for North American Tree Species. USDA Forest Service, Northeastern Research Station. GTR-NE-319

• C. Federer, J. Hornbeck, L. Tritton, C. Martin, R. Pierce. 1989. Long-term depletion of calcium other nutrients in eastern US forests. Environmental Management 13(5), pp. 593-601

• J. Blanco. 2012. Forests may need centuries to recover their original productivity after continuous intensive management: An example from Douglas-fir stands. Science of the Total Environment 437, pp. 91-103

• Q. Ponette, J. Ranger, J. Ottorini, E. Ulrich. 2001. Aboveground biomass and nutrient content of five Douglas-fir stands in France. Forest Ecology and Management 142, pp. 109-127

• J. Compton, D. Cole. 1998. Phosphorus Cycling and Soil P Fractions in Douglas-Fir and Red Alder Stands. Forest Ecology and Management 110, pp. 101-112.