Experimental watershed of evergreen forest

cited from Kabeya et al., (2008)

Experimental watershed of evergreen forest

We measure the runoff at four points, O Toek Loork (OTL), O Thom I (OT1), O Thom II (OT2) and Stung Chinit (CT) as shown in felt figure. And, we carry out the measurements of the rainfall at Kbal Domrey (KD), Kampub Ambel (KA), tower site (TS) and Bak Sner (BS) (Kabeya, et al., 2008).

O Toek Loork (OTL): Latitude: 13°03′N, Longitude: 105°23′E; Elevation: 89-142 m, Area of the watershed: 4 km²
O Thom I (OT1): Latitude: 12°36′N, Longitude: 105°28′E; Elevation: 46-273 m, Area of the watershed: 137 km²
O Thom II (OT2): Latitude: 12°37′N, Longitude: 105°17′E; Elevation: 19-74 m, Area of the watershed: 126 km²
Stung Chinit (CT): Latitude: 12°32′N, Longitude: 105°17′E; Elevation: 19-653 m, Area of the watershed: 3659 km²

Forest canopy of the evergreen experimental forest

Forest canopy comprises three layers of subcanopies. Details of the overstory trees are as follows (Shimizu et al., 2007; Nobuhiro et al., 2007).

Main species: Myristicaceae iners., Anisoptera costana,Dipterocarpus costatus, Vatica odorata, Calophyllum inophyllum
Stand density: 1600 trees/ha
Mean diameter at breast height: 39.6 cm
Mean tree height: 27.2 m
LAI: 4 - 5

	60-m-high tower for measuring evapotranspiration (12°44′N, 105°28′E) We measure the evapotranspiration by the energy balance and bowen ratio method and the bandpass eddy covariance method and general factors of micrometeorology (Nobuhiro et al., 2007; Shimizu et al., 2011). Main equipments Open-path infrared gas analyzer, ultrasonic anemo-thermometer, ventilated psychrometer, capacitance hygrometer, net radiometer, pyranometer, pyrgeometer, quantum sensor, three-cups anemometer, wind vane, and rainfall gauge
	Measurement plot for rainfall interception in the evergreen forest site We evaluate the interception loss near the tower (Nobuhiro et al., 2006). Sap flow measurements by Granier method are carried out to estimate the amount of transpiration (Iida et al., 2010, Iida et al., 2013b).
	Deep soil profile to observe soil layers of Acrisols We dig a deep soil profile 9.4 m in depth by human power. As shown in left photo, the bottom of the trench is too deep to recognize by eyes. The right-upper picture was taken in March 2006, when it was the dry season. We did additional digging and found the groundwater table below the bottom of the soil profile. In contrast, at the end of the rainy season in October 2006, the groundwater level was 2 m below the soil surface (right-lower picture).
cited fron Ohnuki et al. (2008b)	The vertical profile of root density and soil water content The left and right figures show the vertical profiles of the root density and the soil water content of the deep soil profile. We found the root density of more than 20 roots/1m2 above the depth of around 4 m. The uptake of the soil water by the deep root system conduce the decrease of soil water content. The climate of Cambodia is characterized by the Asian monsoon. Although Cambodia has distinct the dry season during which there is little rainfall, the evergreen forests are distributed in Kampong Thom province, central Cambodia. Measurements of the root density and the soil water content on the deep soil profile revealed that trees uptake the soil water by very deep root system to survive the severe soil water condition during the dry season (Ohnuki et al., 2008b).

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