Tall Trees Experiment

Aim

To gather sapflow and environmental meteorological data from Sequoia sempervirens specimens to study biophysical limits to tree height.

Method

Data logging field stations were installed in 15 specimens of Sequoia sempervirens. Sensor clusters were placed at 3 heights on each tree: near the crown, bottom of crown and at the base of the tree.

The following illustrates an installation example.

Sensor Model	Description	Number Installed
Top of Crown
SR2	Solar radiation	1
HT1	Ambient Temperature & Relative Humidity single sensor, radiation shield	1
RG2	Rain gauge	1
AN2	Anemometer	1
LW2	Leaf Wetness	2
HRM	Heat Ratio Method Sapflow	4
Stem Hygrometer	Plant Water Potential	1
Bottom of Crown
HRM	Heat Ratio Method Sapflow	4
Base of Tree
HRM	Heat Ratio Method Sapflow	4
Stem Hygrometer	Plant Water Potential	1

Results

Sapflow
November through February
up to 1069 liters H₂O transpired per day
up to 297 liters H₂O absorbed by leaves per day

Graph of sapflow over time compared to rain over time.

Graph of sapflow by the hour over 24 hours, comparing dry season and wet seasons.

Conclusions

During periods of rain, a negative sapflow was observed.