Research area: Thailand

Research areas: Germany, Laos, Thailand, Vietnam
Research sites in NW Thailand: Bor Krai, Huai Bong, Mae Sa Mai

Mae Sa Mai (Chiang Mai Province)  

This area is located in Mae Rim district, Chiang Mai province, and covers 10.5km2. It extends from N 18 51’ 01’’ to 53’ 55’’ and from E 98 50’ 44’’ to 52’ 20’’.

Mae Sa watershed with the Mae Sa Mai research area. Full extend.

The area is characterised by steep slopes, which are dissected by V-shaped valleys.At middle slope position isolated hills occur, representing remnants of former crests. The elevation ranges from 616m asl up to 1540m asl. The lowest point is located at the north-eastern boundary of the area, where the Mae Sa Noi creek joins Mae Sa stream. The highest point is found on a mountain peak at the southern boundary. The average elevation of the area is approximately 1000m asl. The average annual precipitation measured for 2001/2002 and 2004 at 820m asl was 1419mm accompanied by an average mean temperature of 21.7C. For 2005 an average discharge of 11l s-1 km-2 was measured within the lower part of the Mae Sa Noi catchment (SFB 564 database – unpublished data) which corresponds to 347l m-2 a-1 runoff and percolation. Almost half of the area is covered with forest with the primary forest on the eastern side degraded, but  still intact. Deciduous trees and bamboo dominate the forest below 1000m asl; above it consists mainly of evergreen trees, some pine trees, and bamboo. Along the streams evergreen trees occur. There is no evidence about human activities in this area before 1965. The two Hmong villages Mae Sa Mai and Mae Sa Noi are situated in this subcatchment. Nowadays, the subcatchment is influenced by Hmong people in the upper part and by the activities of Thai  people (Queen Sirikit Botanical Garden and single households) in the lower part. The Hmong originated from the mountainous southern provinces of China. The movement of the Hmong into Northern Thailand has started 1885 (Cooper 1995). In 1965 the Hmong village in the study area was founded under the name Mae Sa Noi at a higher elevation than the present village. In 1975 the villagers moved to the present position due to water scarcity, and the name was changed to Mae Sa Mai (Maxwell personal communication). In 2004 the village was subdivided into Mae Sa Mai and Mae  Sa Noi. Nowadays both villages have together more than 2000 inhabitants (Sangkapitux et al. 1999). Traditionally, the Hmong farming system consisted of  swidden farming, mainly growing maize, opium, and upland rice. During the 1970s opium was cultivated as cash crop, maize for stock feed, and mainly rainfed rice for subsistence (Irwin 1976). Since the 1980s various cash crops were introduced. Nowadays lychee orchards dominate the cultivation area. Only a very small area is covered with mango, “Chinese” peach, or coffee plantations. The plantation of fruit trees went along with irrigation activities.

Mae Sa Mai research area.

Some areas have been reforested with pine trees and some Eucalyptus sp. during the 1990s and with native trees on ridges since 1998 (Maxwell personal communication). Due to pressure by the Royal Forest Department a protected forest area has been established in the south-eastern part of the subcatchment (Sangkapitux et al. 1999).  

The Mae Sa Mai area roughly consists of 90% migmatite, 9% marble, and to approximately 1% freshwater limestone. The predominant migmatite can be subdivided into a granite dominated migmatite (20% of the area) and a paragneiss dominated one (70% of the area). The paragneiss and granite were dated by the German Geological Mission (1979) as Precambrian and Palaeozoic, respectively. Within the paragneiss bodies of marble and (very small) quartzite were found. While the paragneiss dominates the central and northern part of the subcatchment, granite is merely found in the northern part. Paragneiss bodies of variable sizes are preserved within the granite. Paragneiss and granite have as common minerals microcline, muscovite, and orthoclase. Additionally, the granite contains albite and anorthite. The quartz content of the  paragneiss is around 6% higher than in the granite. This indicates reduced weathering rates for paragneiss in comparison to granite.
With respect to geomorphology the weak granites are found in valleys, like the Mae Sa valley in the north, while stronger  paragneiss builds up the surrounding mountain ranges. Granites are often covered with a thick and highly weathered regolith. Despite this, the regolith on paragneiss is mostly shallow and not so intensively weathered. Higher percolation rates for the upper part of granite can be assumed. The different clay mineral contents also show the different weathering intensities. Kaolinite and vermiculite were developed in paragneiss and gibbsite in granite.In the western part of the watershed marble was found in the paragneiss with body sizes ranging from little veins up to a thickness of more than 10 meters. This marble shows clear karst features such as karren and caves. At one site, freshwater limestone is precipitated below a karst spring in the paragneiss-marble contact. The Quaternary freshwater limestone also showed clear karst features in the form of a cave with speleothems. Many prints of leaves and branches are preserved in the freshwater limestone. The marble and freshwater limestone consists to more than 98% of calcite.
The soil cover in the Mae Sa Mai area is dominated by Acrisols covering about 70% of the surface, while the remaining 25% are represented by Cambisols,Anthrosols, Chernozems, Gleysols, Leptosols, and Regosols (see Figure below).  

soil map Mae Sa Mai
Soil map of the Mae Sa Mai area.

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 Ulrich Schuler 2008 -