Research Update Coastal Douglas-fir Fertilization Ian R. Cameron, RPF Kamloops BC Eleanor R.G. McWilliams, RPF North Vancouver BC

History Overview Experiments Model Development Current Work Data clean-up, consolidation Mixed effects modeling Specific Questions Repeat Fertilizer Applications Response on High Sites Next Steps Outline

Experiments EP703 Shawnigan Lake Klinka / Carter RFNRP SMC

TASS Fd Fertilizer Module Developed in late 1980’s, very few changes made since. Stone, J TASS fertilization module. Working draft. Ministry of Forests, Research Branch unpublished report.

TASS Fd Fertilizer Module Coefficients were derived to modify crown foliar volume, mimicking increases in photosynthetic efficiency and foliage biomass as observed at Shawnigan Lake by Holger Brix. Brix, H Effects of thinning and nitrogen fertilization on Douglas-fir: Relative contribution of foliage quantity and efficiency. Can.J.For.Res. 13:

Physiology of the Response Unfertilized Fertilized

TASS Fd Fertilizer Module Other functions modelled increase in height growth. Predicted increases in foliar volume and height translate into increases in bole volume. Magnitude of simulated responses were calibrated to conform to stand-level stats observed in research trials, primarily EP703.

TASS Fd Fertilizer Module Relative response varies with initial density Initial Trees/ha m 3 /ha% 10, , , , , , Total Volume Responses for SI 30 fertilized at 10 m top height.

TASS Fd Fertilizer Module Multiple fertilizer applications are treated as independent events.

TIPSY Fd Fertilizer Module TIPSY fertilization responses are generated in a different manner than most other silviculture treatment responses. Not obtained by interpolating between TASS output tables. Based on percentage responses generated from research and TASS projections of 1200 trees/ha initial density.

TIPSY Fd Fertilizer Module TIPSY % response used for all initial densities for SI 30 fertilized at 10 m top height Initial Trees/ha m 3 /ha% 10, , , , , , TASS Total Volume Responses for SI 30 fertilized at 10 m top height.

TIPSY Fd Fertilizer Module Like TASS multiple fertilizations are treated as independent events. This does not mean, however, that two consecutive applications will have the same level of response.

TIPSY – Two Fertilizer Treatments – Gain dependent on stand age

Stone Site specific differences in fertilization response are not included. Site index is only a surrogate for determining how a site will respond to nitrogen fertilization. Response prediction may increase with knowledge of soil nutrient and moisture regimes.

Stone Limited data for calibration. Responses estimates were based primarily on EP703, which resulted in limited data for calibration of the module on higher sites.

Stone Response predictions are based on a single application of 225 kg N / ha. Multiple applications are implemented as independent events in both TASS and TIPSY. Data from multiple applications of fertilizer was limited and has not been used in module calibration.

Almost 20 years later, it is time for some improvements! Especially with 40 years + of measurements. Shawnigan Lake 1977

What is new? Combining data from Canada and US Consistent compilation –Height-dbh curves –Volume equations –Plot summaries Modelling the complete growth trend of each plot instead of just two points in time.

What is new? Using more of the EP703 data set –Previous analyses used a subset of installations with complete designs Focusing the analysis on what the modellers need to improve TASS / TIPSY Using mixed-effects modelling which explicitly recognizes the hierarchical organization of the data.

Current Work Clean, compile and summarize data from all available sources. –EP703 –Shawnigan –SMC / RFNRP –Misc US trials

Data Available

Current Work Use mixed-effects modelling to estimate heights Historically not all heights measured. In many instances only measured heights of dominant or site trees.

Height-Dbh curves

Specific Questions Response to multiple fertilizations Response on high sites

Multiple Fertilizations Published results based on RFNRP and SMC data indicate diminished responses with each additional fertilizer application. Sucre, E.B., Harrison, R.B., Turnblom, E.C., Briggs, D.G The use of various soil and site variables for estimating growth response of Douglas-fir to multiple applications of urea and determining potential long-term effects on soil properties. Can. J. For. Res. 38:

Multiple Fertilizations The US data contains several installations with plots that have been fertilized up to 4 times. These have been measured up to 8 years after the 4 th fertilization.

Shawnigan Lake 1 st fert 2 nd fert 3 rd fert

Shawnigan Lake 1 st fert 2 nd fert 3 rd fert

TASS / TIPSY Multiple fertilizer applications are currently modelled as independent events.

Response on High Sites EP703 has few high sites. Shawnigan is SI 25. Klinka / Carter trials found some significant gains on SI > 35. These sites were characterized by: –Absence of growing season water deficits –Relatively low foliar N –Adequate foliar P

Response on High Sites Models developed in the US based on RFNRP results show fertilizer responses on SI as high as 42. Wide range of predicted responses. Going to determine if soil moisture and nutrient regime can add any predictive power to the model.

Next Steps Complete analysis of fertilizer response in unthinned stands. Make initial recommendations for changes to TASS and TIPSY fertilizer modules. Complete analysis of fertilizer response in thinned stands. Make further recommendations for change to TASS and TIPSY fertilizer modules.

Questions?