Field Notes

Trip note On May 21 2003 (d141)
Who: Liukang Xu & Jainwu Tang
Weather; Sunny, Temperature around 90s

Problem: When I got our Vaira site yesterday, I found the flux system was running, but outputs from CO₂ and humidity channels of licor 7500 0073 was zero. After I disconnected the licor from the system, then reconnected, I got the correct outputs from the licor. So I guess it was due to bad connection somewhere. This morning after I looked the data, we lost about 11 days flux data, started around d130, 1330 (May 10).

Tonzi site: arrived around 9:10. The grass under the tree is still green, has not shown any senescence. While in the open space, grass was already in the middle of senescent phase.

A/Ci Curve: Temperature response for V_cmax of oak leaf. Finished 5 A/Ci curve at the temperature range 23-35^oC. The shape of each A/Ci curve looks pretty good, hopefully V_cmax response to temperature is also good. Need look the data when Tess got back from the field.

Tower system: Fence and flux system was working. But we are still missing two-day data last week. Talked Ted about the problem yesterday at the site.

Reboot pc, outputs from Gillsonic were all in the right range.

Floor system: Fence and flux system was working, all data loggers communicate well with pc. PV reading 13.3, 7.5 and 2.3 with fully charged battery. Reboot pc, w u v Ts, q, and CO2 channels are good.

At Tonzi site, I also took 3 LAI samples and measured grass height (28.8±7.9cm, n=30).

Dendrometer reading:

Vaira site: arrived around 11:20. Grass is in the middle of senescence, clover looks much greener than other species. Fence OK and flux system was running. But outputs from q and CO2 channel were zero. I guess it was due to bad connection somewhere. After I disconnected everything, then reconnected and reboot laptop, the licor work fine. Grass was much higher (71.7±30.3cm, n=15) inside the fence as compared with outside (54.4±14.7cm, n=25). Also took 3 LAI samples. PV reading was 13.3, 7.5, and 2.3 with fully charged battery. Reboot pc all channels are good.

Soil moisture probe reading

Jianwu’s note:

The soil CO2 profile system works well, as the soil is getting dry. The gradient is clear from 2000ppm to 15,000ppm. The understory CO2 efflux is as high as 7-8 micro mol, while in the open space CO2 efflux is 2-3. CO2 flux from the tree stem is 1-2.

I installed another metal sheet in soils. Now we have two small plots with sheets surrounded. I also installed a soil collar for chamber measurement in each of the plot. I will use these plots in August, about 3 months after installation, to minimize any disturbance.