Field Notes

When: Dec 23, 2002 D357 Mon.
Where: Tonzi/Vaira Ranches
Who: Liukang Xu & Jianwu Tang
Weather Cloudy, temperature below 10^oC

Just before the Christmas, on Dec 23, I and Jianwu went to our field site for bunch of tasks. Here is the detail of the trip notes.

Trip Purpose: check 3 flux systems, replace all the li-cor 7500, and download data, soil moisture probe reading, dendrometer reading, grass height measurement, LAI sample at Vaira and Tonzi, Jianwu installed another set of soil CO2 probes underneath the big tree.

Went to Ione to pick up 2 batteries and 3 battery boxes and a set of wrench for Jianwu and Ted.

Vaira ranch: 12:15 arrived. The 4 solar panels Ted just installed last month was on the ground due to the storm and the electric fence wire was broken. Fortunately no cow seems getting in. I was able to raise the solar panels. We need re-strengthen supporting frame for these solar panels. Two 6-inch nails cannot hold 4 solar panels, especially in the middle of the raining season. Also fixed the fence wire. Fence battery voltage was around 11.6V, should be OK

Flux system was running. PV reading 13.2, 13.2, 2.2 at 1:07 pm. Replaced licor 7500 sn 0418 came off and sn 0065 went on. Download data. Many keys of laptop are not working, the problem getting worse and worse. Delete 2001 raw data files. Soil moisture reading (see below), grass height measurement (n=17, mean=4.9 cm std=1.3 cm) and took 3 LAI samples. Old grass from previous season still hang there, cover about 1/3 of the ground.

Restart PC , the output of gillsonic was on scales.

1. We missed lot of data due to the raining. After roughly looked the raw data, I found only about 43% of the time the flux system was running. The floor and tower system seems to be little better with 82% and 63% of the time running.

Soil moisture reading: the whole soil profile is almost saturated after the big storm.

Floor system: around 2:20 pm. flux system and fence working well. PVC reading 13.9, 13.8, and 1.9. Battery fully charged. HD 1.94 GB left after I deleted *.raw in the 2001 folder. All data loggers communicated with pc. Replaced li-7500 sn 0073 came off and sn 0041 went on. After reboot laptop, flux program running properly.

Soil moisture reading (see above). Grass height measurements (n=15, mean=2.8cm, and std=1.1 cm), also took 4 LAI samples.

Tower system: fence OK. PV reading 14.0, 6.9 and 1.2 at 3:50. Battery fully charged. Fan for T/RH sensor at the tower not working, need replace it. HD has 2.2 GB left after deleted 2001 raw data. Replaced li-cor 7500 sn 0035 came off and sn 0042 went on. Downloaded data, reboot PC, w, u, v, Tsonic, q and CO2 outputs on scale.

Dendrometer reading. Tree trunks keep expanding as we can see from the following data.

Jianwu’s Notes

I installed another soil CO2 profile measurement system under the tree that Liukang measured photosynthesis. A solar panel was installed to power the batteries. The signal wire was connected to the same datalogger that we measured soil CO2 in the bare soil. I will run the system in the next visit.

The CO2 concentration in the soil reached as high as 4000-5000ppm. The difference between different depths is not as high as in the dry seasons.

I also measured CO2 efflux as well. Under trees the reading was as high as 2-3mmol s-1 m-2, but in the bare soil it was only 0.6-1. The stem respiration is about 0.4-0.7.