Location
Changwu Agro-ecosystem station (CWA) is located in Wangdong village Hongjia town, Changwu county, Xiangyang Shaanxi Province. Its geographical coordinate is 35° 14' N and 107° 41' E with an elevation of 1220 m. CWA belongs to the Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources. There is a flux observation tower in the supplement observation field of CWA. The geographical coordinate of the flux observation tower is 35° 14' 31.54" N, 107° 40' 55.90" E. The elevation of the tower base is 1220 m. The flux observation footprint represents a typical winter wheat in the Tableland of the Loess Plateau.
Climatic
CWA belongs to semi-humid region of warm temperate zone. Precipitation in the region is rare with irregular distribution between years and months. It falls down mainly from May to September, accounting for around 80 % total precipitation in a year. Its prevailing wind is at southeast-northwest direction.The average precipitation is 584 mm, annual average temperature is 9.1℃, and frost-free period is 171 d.
Vegetation and soil
Winter wheat, spring maize and apple are the main plants in the region. Plant community composition is single crop population.
Soil particle composition for 0-20 cm depth is 23-26% of clay, 42-53% of silt, and 22-38% of sand. Soil organic matter is 10.4 g/kg, total nitrogen is 0.62 g/kg, alkali hydrolysable nitrogen is 37.0 mg/kg, rapid available phosphorus is 3.0 mg/kg, rapid available potassium is 129.1 mg/kg. Soil pH is 8.3. Soil depth is around 50-100 m.
Observation system
The flux measurement system consists of three-dimensional sonic anemometers (CSAT3, Campbell) and an open-path infrared gas analyzer (LI-7500A, LI-COR).The height of flux tower is 2 m. Ultrasonic anemometer is at a height of 1.8 m, temperature and humidity meters are at a height of 1.8 m. Radiometers are mounted at a height of 2.2 m. Soil temperature and moisture probes are set at the depths of 5 cm, 10 cm, 20 cm, 40 cm and 100 cm.
Data sampling frequent is 10 Hz, flux average time is 30 min.And time begining the observation is Sep,2006.
Principal Investigator
Wenzhao Liu
E-mail: wzliu@ms.iswc.ac.cn