Since I have succeed in reinstalling the equipment, I set three goals for field trip this time:

(1) Check data of sap flow, band dendrometer and soil moisture.

(2) Measure tree heights and DBHs in Block 2 and 3.

(3) Measuring photosynthesis by Li-cor 6400 XT.

Before going to the field, I checked the condition of Li-cor 6400 XT, and was glad to find that it worked well, though it has not been in use since November last year. I also charge the batteries of Li-cor 6400 XT.

Adam, Dr. Wu and I went to the field  on June, 14, 2017.  It was a sunny day, not cold nor hot. On arrival, I brought my laptop and download the data, while Adam and Dr. Wu measured tree heights and DBHs in Block 2 and 3.

I was so sad to find that the No.3 tree did not give any sap flow signals, indicating a disconnection between tree No.3 and the datalogger. So I  checked mainline of datalogger, the connectors were all connected. Then I went to B1T2 site where the No.3 tree was, to check the connection between sap flow probe and the extension line. It was connected, indicating that there might be broken in the middle of the wire.

The way to find out where was broken was very tough, because there were a bunch of wires connecting sap flow probes, band dendrometers and soil moisture from various trees, and to various extension cables in three plots . Identify the specific broken wire and the position needed at least two people, use electricity meter, section by section at those wires. Adam and Dr. Wu were all at Block 2 which is at least 30 meter away at that time, so I decided to put aside, and check for the other data.

Tree No. 1, 10 and 15 showed a wired sap flux pattern, though the data were in a normal range and shape. It seemed that the three trees has no any sap flowing through trunk at the day time, but transpired at the midnight. However, compared with other trees under the same treatment, the shape and the range were all similar. Thus, I did not think that there were connection problems in the three trees. Rather, I supposed that either trees responded abnormally, or the probes were dis-functional. I could not solve either of them, so I put them aside as well.

Only one band dendrometer worked well (Tree. No. 13). Then, I found that most problems came from a bad connection in the connector. This was the top lesson I learn at this field trip: DO NOT TRY TO DO SOMETHING BEYOND WHAT YOU HAVE MASTERED IN A IMPORTANT EVENT. The field experiment this year is so important to me, I will not be able to afford any failure. But I used a novel detachable connector which I just got to know one day before my field installation. I could not handle them well, but I applied them in all my band dendrometers connection. In fact, installing this novel connector consumed more time than that of an ordinary one.  I should not use them at all until I mastered them.  How stupid I was!!! Anyway, I cut the connectors off, and replace it with the ordinary ones and junction boxes.

Fig. 1 replacing detachable connectors with ordinary ones and junction boxes

So it took me double time to install the band dendrometers, let alone the expenses on them. I felt so sad… 🙁

Besides, one soil moisture sensor which is located at B1C at the depth of 40 cm gave negative value. After excluding the connection problems in the wire connecting to the datalogger, I thought it was a disconnection at the multiplexer inside the datalogger, by observing an apparent disconnected wire tip in it. However, I did not where channel should I put the tip into, so I took a photo and would ask Antonio for help.

Measure tree DBH and heights was time-consuming, too. Adam and Dr. Wu spent four hours on it. At around 2:30 pm, they came back and asked me about the connection. I was almost finishing replacing the connectors of band dendrometer. So I told them about the disconnection of tree No.3. To my surprise, they suggested to look at the probes first, by disengaging all the foil and foam isolations around it. This suggestion was really good! We found the wire of probe of tree No.3 was broken, as a result of pulling the short wire so hard in order to connect it to the mainline. So we tried our best to re-connect it. However, we failed.

                 Fig. 2 Broken sap flow probe in tree No.3

By the end of that day, we went home with pity. The only achievement today is that tree heights and DBHs in Block 2 and 3 were measured, and all connectors of band dendrometers were replaced. I did not measure photosynthesis as I planed. I hope that field trip next week could be better!

Extra bonus: Blue eggs turned into nesting. Do you know who they are?