Mariann JohnstonSophie Harrison/Adam Wild

2014Brigid Farrell & ‘WolfPas’ 2015

Sap flow : Calcium, and what about N and P?

Background• Hubbard Brook whole-watershed transpiration

response to 1999 wollastonite (CaSiO3)

(M. Green, A. Bailey, S. Bailey, J. Battles, J. Campbell, C. Driscoll, T. Fahey, L. Lepine, G. Likens, S. Ollinger, P. Schaberg, 2013)

Background - MELNHE• 2011 – Extra (5th) plot receiving a one-time

CaSiO3 application was added to a subset of MELNHE sites (Green et al.)

• 2014 –Transpiration measurements on Control and CaSiO3 plots at Bartlett C8, Hubbard Brook (old), and Jeffers Brook (old) - YB, SM, BE

• 2015 – Measurements on five treatments (Con, N, P, NP, CaSiO3) at Bartlett C6 - WB

About measuring transpiration . . .• Granier method: reference probe 10 cm below a heated

probe, measures temperature difference (ΔT) (Granier, 1987)

• Measurements collected by data logger every 30 seconds, average recorded every 15 minutes

• ΔT converted to sapflux (Js, g x m2 x s-1) using BaseLiner software (Oren and Parashkevov, 2012)

Research Questions:• Does CaSiO3 addition increase

transpiration? – Expect that it does, possibly due to

increased xylem and fine root growth– 2014 data was 3 years post-

application; 2015 data is 4 years• Do N and P impact transpiration?• Does transpiration vary by species?

Field Methods• Install probes, hook up data logger

and batteries• Visit data logger routinely to

download and check data

Statistical Analysis• Three data sets• 2014 SM, YB on C8 (June), HB(July), JB

(Aug)• 2014 BE (pooled C8, HB)• 2015 WB on C6 (5 treatments)

• Mixed Model Analysis• Random: Time (curvilinear)• Explanatory: Weather covariates vs PET• Predictors: treatment, species

• 3 weather covariates was a better model fit

• Single PET covariate was an easier model fit

Results – YB-SM Treatment Effects (2014)

Type 3 fixed effectsSite p= 0.01Treatment p= 0.26Site*Trt*Time p= 0.03

Results – YB-SM Species Effects (2014)

Type 3 fixed effects Species p=0.09Species*time p=0.001Site*Sp*Time p= 0.001

Results – BE Treatment Effects (2014)

Type 3 fixed effects Treat p=0.42Treat * Time p=0.05

Results – WB Treatment Effects (2015)

Type 3 fixed effectsTreatment p=0.12Treatment*Time p= 0.01Treatment*Time2 p = 0.08

Results- Summary• 2014 (YB, SM, BE)– CaSiO3 increased transpiration over Con– YB had higher transpiration than SM (BE even higher)– YB-SM interacted with time and site/date

• 2015 (WB)– P decreased transpiration in WB – WB in mid-age stand had higher transpiration (except P!)

than anything in 2014• Thank you HB Sta 1 and Bartlett Flux Tower! – Explanatory effects were immensely important in being

able to detect effects of interest

Acknowledgements• Michele Pruyn!!!!!• Sophie Harrison• Adam Wild• Mark Green• NSRC • Ruth Yanai• Matt Vadeboncoeur• 2015 Shoestring Crew

Thank You To . . .