I have arrived in Basel for some professional development related to my PhD . Travelling time was almost 40 hours with three stops. I felt quite good despite the 11 hour time difference between Auckland and Basel. As I wrote previously I am learning some new techniques for my work. I will also be giving a talk on my mangrove work at the Botanical Institute of Basel. In preparation for the talk (and a poster for a conference) I put together some figures of a three day time-series of some data we have collected. Being a newish R user I found it highly frustrating at times, particularly getting around the way that R deals with time. After many hours of trial and error, and the patient assistance of some colleagues, I finally got what the figures pretty close to how I wanted them.
It depicts three environmental/climatic variables and three plant water-use measures. There is a really nice tight coupling between all of the variables that can be explained within current understanding of tree physiology. During the day (white areas) when it is warm, humidity is low and the sun is shining, sap-flow is elevated, tree stems shrink and leaves lose turgor. Heat, dry air and sunlight promote transpiration which results in the observed sap-flow rates. At the same time, water stored in the stem is transpired which causes the stems to shrink. Leaves lose turgor, or become flaccid, because they are losing water to the atmosphere (transpiring). At night time (shaded areas) when it is cool, humid and dark transpiration very low or non-existent. Therefore, there are depressed sap-flow rates, an expansion of the stem and increased leaf turgidity.