Mariann JohnstonSophie Harrison

Sap flow 2014: Does CaSiO3 enhance water use?

Background• Hubbard Brook whole-watershed transpiration

response to 1999 wollastonite (CaSiO3) addition

(Green et al. 2013)

Background• 2011 - A CaSiO3 treatment was added to a

subset of MELNHE sites (Green et al.) A 5th plot was added with a one-time CaSiO3

treatment i(1.2 metric tonnes ac-1) Included ‘old cohort’ sites: Bartlett C8, Hubbard

Brook (old), and Jeffers Brook (old)

• 2013 –Transpiration measurements attempted on Control and CaSiO3 plots at all three ‘old cohort’ sites concurrently, growing season But . . .

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)

Back to the Background• 2013 efforts suggested increased transpiration

in CaSiO3 treatment at HB-old (Zahor 2013 w/ M.Pruyn)• This despite technical difficulties that impeded more

comprehensive analysis -• 2014 effort redesigned to focus on one site at a

time, full battery power, frequent monitoring– We instrumented Control and CaSiO3 plots – Selected 3 trees each of 3 species (sugar maple,

American beech, yellow birch) totaling 9 per plot• Sophie Harrison presented some preliminary

results at last year’s meeting

Research Questions: What impacts transpiration rate?• Does CaSiO3 addition increase transpiration?

– Expect that it does, possibly due to increased xylem and fine root growth

– These data are now 3 years post-application• Does transpiration rate vary between tree

species?

Field Methods 2014• A total of 47 trees were

measured across the three sites

• Measurements collected for ~5 days per stand

Statistical Methods• Data analyzed as diurnal curves

from 5:00 am to 10:00 pm• Mixed model approach to repeated

measures analysis • Can handle missing values and

unbalanced design• Covariates were vapor pressure

deficit, wind speed, and radiation (Hubbard Brook Weather Station 1)

• Predictors were treatment, species• Block effect for site/date

Photos from www.hubbardbrook.org, watershed-6-tour

Results - Species

Results - Treatment

Also of interest-• Atmospheric covariates (radiation, vapor

pressure deficit, wind speed) were all significant, and explained 22% of the residual variation in the data.

• Covariates were added to the model before examining for predictor effects.

Results- Summary• Species (p=0.0165) and Species * Time (p=0.0174)

were significant.– Species varied in mean transpiration rate and in

transpiration pattern over the course of a day– Explained 18% of between-tree variance

• Treatment effect of CaSiO3 was significant (p=0.0219)– Treatment effect is still apparent (higher) in the 3rd

season after application– Explained 11.5% of between-tree variance

References & Acknowledgements• Granier, A. (1987). Evaluation of transpiration in a Douglas-fir stand by means of sap

flow measurements. Tree Physiology 3: 309-320.• Green, M.B., et al. (2013). Decreased water flowing from a forest amended with

calcium silicate. Proceedings of the National Academy of Sciences 110(15):5999-6003.

• Oren, Parashkevov, & Duke University. (2012). BaseLiner (Version 2.4.2) http://ch2oecology.env.duke.edu/orenlab/sofware.html

• Michele Pruyn!!!!!• Adam Wild• Mark Green

• NSRC • Sophie Harrison• Ruth Yanai• Matt Vadaboncoeur• 2014 Shoestring Crew

Thank You To . . .