Field Notes

Trip note On June 20 2003 (d171)
Who: Liukang, Tess, and Jianwu

Purposes: Predawn water potential measurement, instrument maintenance, swap all li-cor 7500, data downloading. Take 6 samples for grass aboveground biomass at Tonzi site (Liukang), and A_Ci curve measurement (Tess), soil and stem respiration measurement (Jianwu).

Weather; sunny, mild, temperature around 85^oF.

Tonzi site: 4:35 arrived, Tair=10^oC. Predawn water potential measurement.

Midday leaf water potential was around –2.5 to –3.0 MPa, as measured during the demonstration to Tess how to use the pressure chamber.

Dendrometer reading.

I also took 6 biomass samples at Tonzi site, tried to determine the grass NEP. (3 samples from inside fence closure and 3 from outside of the fence.

Floor system: Fence working good. Flux system was running good. PV reading 12.5, 0.0 and 2.6 at 5:50 am with fully charge battery. Replace licor 7500 sn 0073 came off and sn 0418 went on. Upload a new CO2 profile code to CR10X7, so that the licor 800 will be zeroed and spanned twice a day.

Reboot pc, six channels outputs are

Tower system: Fence OK, flux system running good. Missing some data, Ted: watchdog has problem again at tower system. It turned off the flux system on d167 at 4:30, but the system wasn’t back on until next day 5:00. Replaced licor 7500 sn 0041 came off and sn 0035 went on, changed the bandwidth setting to 5Hz for 0035. Need change this setting for all other 7500s. I couldn’t see any single spike from CO2 and q channels around 6:30, but in the afternoon, the system still spiking.

Soil moisture probe reading

Vaira site: arrived 12:10.

Fence OK, flux system running without missing a single 0.5 hr data. Replace li-cor 7500 sn 0065 camem off and sn 0042 went on. PV reading 13.6, 12.2 and 2.6, fully charged battery.

Soil moisture reading see above.

Here is Tess’s notes:

“I went out to Tonzi on June 20^th, 2003 for the purpose of taking A-Ci curves with Liukang. Arrived 9 am, weather was breezy. We selected a tree with large leaves east of the tower. Although we had trouble with wind, we managed to take two good A-Ci curves at ambient temperature. I am a bit concerned about variations in Leaf Mass per Unit Area (LMA) and corresponding variations in Vcmax with leaf area depth in the canopy. I am also concerned about the level of noise in my data, and the possibility of leaks. Liukang and I also reviewed predawn water potential measurements so that I can take over for him this summer.”

Jianwu’s notes:

Due to unknown reasons (not due to moisture as happened before), one CO2 probe (sn X1920002) in open areas has errors in reading. It was replaced with a good one sn ???? and take back for sending-back-to-factory re-calibration. The other probes worked well. The vertical CO2 concentration varied between 400ppm to 3000ppm.

The LiCor 6400 with a soil chamber has problems after it was used by Leda. I calibrated in the lab with no problem in zeroing and spanning but there are problems in measuring fluxes. I inspected it and found the problem may be come from the mixing fan. I will take back to the lab and check it again.

The diagram for the transect was redone for your information: