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Sanya Tropical Rainforest Flux Observation Station is affiliated with Haikou Marine Geological Survey Center, China Geological Survey. The observation station is located within the Natural Resources and Ecological Restoration Base of Nandao, Sanya, established in 2019, with a total area of approximately 38.5 km². The region where the observation station is located belongs to the southern branch of the Wuzhi Mountain Range, predominantly characterized by low mountains. The overall terrain of the observation station slopes from southwest to northeast, with the highest peak located in the western part of the station and radiating towards the eastern part. The highest elevation is 562.4 meters, the lowest elevation is 430.3 meters, and the relative elevation difference is 132.1 meters, with slopes ranging from 10 to 20 degrees.The latitude and longitude coordinates for the Flux Observation Tower are 109°26'55" E, 18°25'48" N.


The observation station is located at low latitudes, belonging to the tropical maritime monsoon climate zone. It is characterized by abundant sunlight, a perpetual summer without a distinct winter, high temperatures, abundant rainfall, frequent typhoons, and indistinct seasons throughout the year.

The region has an annual average temperature of 25.3°C, with the average highest temperature in July reaching 28.79°C and the average lowest temperature in January being 21.4°C. The annual average sunlight duration is 2534 hours, and the annual precipitation ranges from 1400 to 1800 mm. The multi-year average relative humidity is between 78% and 93%. There is a distinct dry and wet season, with November to April of the following year being the dry season and July to October being the typhoon and heavy rainfall season. During the latter period, precipitation can account for 85% to 95% of the total annual precipitation. Due to the favorable terrain, the prevailing wind speed is generally less than 2 m/s, resulting in relatively mild typhoon impacts in the area.

Vegetation and soil

The main vegetation types in the area where the observation station is located are deciduous and evergreen seasonal rainforests, comprising both natural forest communities and artificial forest communities. Natural forest communities include associations such as the Mountain Wutong + Hainan Oak community, Lingnan Mountain Bamboo community, Yellow Catkin community, Yandou Ke + Lipo Ke community, Meiyecaidoushu + Yellow Catkin community, Yellow Catkin + Lingnan Mountain Bamboo community, Tray Blue Oak + Yellow Catkin community, Water Weng community, Hainan Oak community, Fine Child Dragon community, Fine Child Dragon + Narrow Leaf Half Maple Lotus community, Yellow Tong + Fine Child Dragon community, Hui Guo Anxi Xiang + Water Weng community, and others. Artificial forest communities include Rubber community, Betel Nut community, Large-leaved Mimosa community, Sinking Scented Sandalwood community, Slope Levee community, Soil Sinking Scented Sandalwood community, Sandalwood community, Red Flower Tianliaomu community, and others.

The understory vegetation type beneath the flux tower is characterized as evergreen seasonal rainforest, but the specific composition of the main community has not been identified yet.The canopy height of the understory vegetation is 10-15 meters.

The predominant soil type within the observation station's range is Andosol (volcanic ash soil) and Red Soil derived from basalt.The soil layer is approximately 15 meters deep, characterized as gravelly sandy loam. The soil is loose and porous, with a relatively high organic matter content. The humus layer can be more than 10cm thick, making it suitable for the growth of various plants.

Observation system

The observation station primarily conducts comprehensive monitoring of the tropical rainforest ecosystem, including continuous and fully automated observations of the gradient changes in forest meteorological elements, energy balance, carbon cycling, water flux, and more. The main observational equipment includes infrared analyzers and three-dimensional ultrasonic anemometers, CR6 data loggers, TRB3 temperature-humidity-pressure sensors, SM926 soil three-parameter sensors, CS106 atmospheric pressure sensors, W10 wind speed sensors, W20 wind direction sensors, negative ion sensors, TE525 rain gauges, and others.

The flux observation tower is approximately 30 meters high above the near-surface layer, and its main observation equipment includes: Wind speed sensors at 5 levels (0.2 meters, 1.5 meters, 6 meters, 15 meters, 30 meters). Wind direction sensor at 1 level (30 meters). Air temperature and humidity sensors at 5 levels (0.2 meters, 1.5 meters, 6 meters, 15 meters, 30 meters). Open-path eddy covariance observation system at 1 level (30 meters). Negative ion sensor set at 1 level (1.3 meters). Additionally, the tower is equipped with soil temperature, humidity, and salinity sensors at 5 levels (underground: -5 centimeters, -10 centimeters, -20 centimeters, -40 centimeters, -80 centimeters); soil lysimeter set (underground: -1.3 meters); tree sap flow meters (5 sets for measuring plant transpiration rate); and infrared analyzer with a three-dimensional ultrasonic anemometer at 10 meters.

The CR6 data logger has a measurement frequency of 125Hz (8ms) with a maximum multiplexed analog rate. The flux average time is 30 minutes.

Observations began in September 2022.

Principal Investigator

Wenjie Liu     E-mail:

Station director

Wenjie Liu

Assistant station director

Mengyang Fang

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