Field Notes

When: May 9, 2002, d129 Thu
Where: Tonzi/Vaira Ranches
Who: Liukang Xu
Weather Sunny, temperature middle 70’s

Trip Purpose: Predawn water potential measurement, check 3 flux systems, soil moisture point sensor reading, grass height measurement, dendrometer reading, A/Ci curve for oak leaf at Tonzi Ranch, swap li-cor 7500 at Floor and Vaira.

Overall: all flux systems were running great last week, except the one at Vaira (we are missing about half-day’s data). All instruments work fine. The grasses at both sites are dying. I start to feel crunch when walk in the field, indicating the dryness of soil surface.

Tonzi Ranch: Arrived at 4:30am, clear sky, chilly. Predawn water potential measurement; results show that water potential drops about 1-2 bar from last measurement (3 wks ago on Apr 18).

Dendrometer reading:

Surprisingly, most of trees are still expanding. Due to growth (not likely I guess) or due to continuously improving water status? I don’t know !

Vaira Ranch: 7:30 am arrived at Vaira, no cows around. Grass turn to yellow, grass seed start to fall off. Fence working, flux system working. Swapped li-cor 7500s sn 0042 came off and sn 0065 went on. Power plug for 0065 seems have bad connection sometimes.

Sonic output before and after swap and reboot pc.

PV reading; 12.5V, 4.0A and 2.7A, battery half full (at 8:05am), moisture point sensor reading, result see below.

Left a fully charged battery at Vaira, in case we need it.

Grass height measurement (n=30, m=50.2 cm, and std=14.2 cm)

Back to Tonzi Ranch around 9:20am, start A/Ci curve on oak leaf. Finished 3 curves. I can not download the data out from li-cor 6400 using window FX. Sometimes I had the same problem last year, I have to take the instrument to Dr. Hsiao’s lab to get the data out by using DOS FX. I should contact li-cor Inc about this problem.

Soil moisture probe reading

Tower flux system: Fence work good, flux system running good. PV reading at 9:50am are 13.6V, 9.2A, and 2.4A, battery half full.

Sonic out put after reboot the PC.

Floor Flux system: Fence working, flux system running and communicating with all the dataloggers. Swapped li-cor 7500s sn 0035 came off and sn 0073 went on. PV readings 14.4V, 16.9A and 1.7A.

Sonic outputs after swapped li-cor and reboot pc;

Grass height measurement (n=30, m=26.8cm, std=9.8cm). Left one fully charged battery at floor met station.

I start copy all the data to the new computer H205-3.