Nutrient Limitations to Growth of Westside Douglas-fir Forests: A Look Beyond Nitrogen Doug Maguire Department of Forest Science Oregon State University Oregon State University Steve Perakis FRESC USGS USGS Rick Fletcher Department of Forest Resources Oregon State University Doug Mainwaring Department of Forest Science Oregon State University

Background Trials originally of interest to members of the Swiss needle cast cooperative Trials originally of interest to members of the Swiss needle cast cooperative –Fertilization has been investigated as one of the tools to combat SNC –Previous SNC fert studies have generally included N, either as single-nutrient treatments or blends: Menasha trials Menasha trials Plum Creek trials Plum Creek trials VMRC trials VMRC trials Balanced Fertilizer trials Balanced Fertilizer trials

Background Studies suggest that nitrogen may be problematic in SNC-infected stands Studies suggest that nitrogen may be problematic in SNC-infected stands –Lack of response to N in previous fert trials –Negative correlation between foliage retention and foliar N –N from fertilization was found to be directly responsible for increased the fungal nitrogen levels and fungal fruiting, and thus, disease severity

Background Studies suggest that nitrogen may be problematic in SNC-infected stands Studies suggest that nitrogen may be problematic in SNC-infected stands –Lack of response to N in previous fert trials –Negative correlation between foliage retention and foliar N –N from fertilization was found to be directly responsible for increased the fungal nitrogen levels and fungal fruiting, and thus, disease severity

Background Proposed study went through several iterations to meet the needs of participants Proposed study went through several iterations to meet the needs of participants –How to include non-SNC Coop members –Fixed area vs. individual tree plots –Treatments

Fertilization Trials 16 locations, 12 landowners Cascade Timber Giustina Green Diamond (2) Hampton (2) Lone Rock Menasha (2) ODF OSU Port Blakely Starker West Fork Timber Weyerhaeuser (2)

Study design Individual tree plots (1/40 th acre) 10 plots per treatment 5, 7, or 8 treatments per site 50, 70, or 80 plots per site 18.6 ft

Target stands –20 yrs of age (+/- 5 yrs) –300 tpa (+/- 100 tpa) –No pct or fertilization in last 8 years –< 20% salal cover – Good road access – Relatively flat – Limited brush cover – Nearby donut source

Target stands –20 yrs of age (+/- 5 yrs) –300 tpa (+/- 100 tpa) –No pct or fertilization in last 8 years –< 20% salal cover

Treatments TreatmentFormAmountReason for inclusion Control - - Statistical reference for treatments NUrea224 kg N / haStandard approach, examine effects of adding N to N-rich sites LimeCaCO kg Ca / haElevates pH, reduces Al, adds Ca: compare to Ca-only treatment CaCaCl kg Ca / haLow soil and foliar Ca is common at our sites, attributable to high soil N PNaH 2 PO kg P / haCan limit growth in highly weathered soils, some sites have P-fixing soils KinseyBlendSite specificScientific and industry interest in overall nutritional limits to productivity FennBlendSite specificScientific and industry interest in overall nutritional limits to productivity

Treatments, Kinsey Values given in lbs/acre

Treatments, Fenn Values given in lbs/acre

Installation Choose appropriate dom/codom measure tree on 1 chain grid Subject tree measurements: Dbh Ht Hllb Sapwood width 5.5 m Fifth-whorl foliage retention

1/40-ac plots centered on measure tree (radius=18.6 ft) Installation Plot-level measurements: Dbh of all trees within plot

Installation Treatment-level data (composite from 10 plots): Foliage (needles from current shoots) Soil (from 2 soil cores) Each treatment randomly assigned to 10 plots

Schedule –Install and measure plots –Sample soil and foliage –Fertilize (February-March) –Sample soil and foliage –Apply lime to Kinsey treatments –Measure plots –Sample soil and foliage –Measure plots