Field Notes

When: Oct 02, 2002 D275 Wed.
Where: Tonzi/Vaira Ranches
Who: Liukang Xu
Weather Sunny, temperature lower 70s

Trip Purpose: Predawn water potential measurement, check 3 flux systems and download data, soil moisture probe reading, dendrometer reading, A/C_i curve for oak leaf at Tonzi Ranch.

Overall: All the flux systems were running great. The trees are in the middle of senescence phase. Overall about 50% of leaves are brown, but the variability is large.

Problems: The fences at floor and Vaira failed. No cows break into at floor system. But at Vaira site, fence wire was broken, clear sign of cows getting into. Fortunately, there is no damage for instruments. The communications between all the dataloggers and the laptop still good. After I replaced the battery with a fully charged one and fixed the wire, the fence works fine. We need discuss this problem, and find out why this happen. It happened three times since the electric fence was installed. Twice cows got into the fence.

Tonzi Ranch: arrived at 5:30 am. Clear sky, little windy temperature mid 40s.

Predawn water potential measurements. This is the last measurement of the season. See below for the seasonal trend.

Dendrometer reading:

Tower system: fence OK. PV reading 12.7, 10.5 and 1.9 at 10:30. After downloaded data, reboot PC, w, u, v, Tsonic, q and CO2 outputs on scale.

Floor system: flux systen running good. Fence was down. I can barely feel the electric pulse only when the sunlight hitting on the solar panel. PV reading 13.7, 14.0 and 1.9 around 10:50.

Jianwu’s CO2 sensor works Ok, with reading 410, 480 and 650 ppm, around 11:45 am.

Vaira ranch: arrived around 7:30, flux system running good. Fence down, fence wire broke. I replaced the battery and fixed wire, the fence works fine. Don’t know what caused the failure. PV reading 12.4, 2.1 and 1.4 at 7:50. All communication with data loggers is good. The fan for the T/RH sensor was not running. Download data and soil moisture reading.

Soil moisture reading.

A/Ci curves for the Oak leaves. Due to the little wind and water stressed condition, the leaf petiole is easily broken. I got two leaf petiole broken in the mid of their A/Ci curves. But I managed somehow to finished two “A/C_i curves”, with C_a ranging only from 50 to 360 ppm. We can still get a good estimation on V_cmax based on, but not for the Jmax.