areas: Germany, Laos, Thailand, Vietnam
Excursions: Australia, China, Germany, Hungary
Research sites in NW Thailand: Bor Krai, Huai Bong, Mae Sa Mai
Soils of NW-Thailand: (a) Major Soils: Acrisols, Alisols, Cambisols; (b) Minor Soils: Anthrosols, Ferralsols, Fluvisols, Gleysols, Leptsols, Luvisols, Plinthosols, Regosols, Technosols, Umbrisols; (c) Exotic Soils: Chernozems, Histosols, Stagnosols, Vertisols
NW Thailand is characterised by mountain ranges, generally trending in a north-south direction with slight curves (see Figure below).
Research area in NW Thailand. Full extend.
"Doi Inthanon", the highest mountain in Thailand, with an elevation of 2565m above mean sea level is an integral part of Northern Thailand. Between the main mountain ranges several basins exist, like the ones at Chiang Mai, Pai or Fang. "Morphogenetically, the landforms of Northern Thailand range from stable and largely flat relief of old content blocks to young mobile alpine mountain chains" (Kubiniok 1999).
Northern Thailand is divided in two different climate types concerning elevation ranges. The lower elevations with a temperature of the coolest month over 18°C belong to the tropical humid climate, "Aw"-type (A = tropical rainy climate; w = dry during the period of low sun angle and wet during the period of high sun angle). The higher elevations with an average temperature in the coolest month below 18°C belong to the humid mesothermal climate zone, "Caw"-type (C = humid mesothermal; aw = dry winters) (Köppen, 1923, Trewarta 1968, Landon 1991).
Three different seasons can be distinguished in Northern Thailand. The rainy season begins with the onset of the southwestern monsoon in May or June and continues until mid-October. Approximately 90% of the total annual precipitation falls during this period. During the rainy season the southwest – to west monsoon transports warmhumid air masses from the Indian and Pacific Ocean, while a low pressure cell is dominating the Asian landmass, causing heavy convective rain showers. In this period the intertropical convergence zone is moving northwards over Thailand in May and southwards in September (Eelaart 1974).
In the following cool dry season lasting from November until February, the Asian landmass is under the influence of a high pressure cell. During this period, the northeast monsoon brings cool dry air masses which cause night time and early morning temperatures occasionally to drop to the freezing point at high elevations (>2000m asl). During this season very little rainfall occurs, while air humidity remains relatively high. In the following cool dry season lasting from November until February, the Asian landmass is under the influence of a high pressure cell.
During this period, the northeast monsoon brings cool dry air masses which cause night
time and early morning temperatures occasionally to drop to the freezing point at high
elevations (>2000m asl). During this season very little rainfall occurs, while air humidity remains relatively high.
The hot and dry season usually begins approximately in February and continues until May delivering warm winds from the south causing a temperature increase. During this time, precipitation is quite rare, as Thailand and especially its northern part are located in the “rain shadow” of western mountain ranges (Eelaart 1974). Intermittent rain showers may arrive approximately end of April lasting until the start of the monsoon season (Hendricks 1981).
For more than 75% of the soils clay illuviation was identified as the major soil forming process. Accordingly, soils were mainly classified as Alisols and Acrisols. Less frequent soil types were Cambisols, Umbrisols and Regosols. The remaining soil types mapped (Anthrosols, Chernozems, Ferralsols, Fluvisols, Gleysols, Leptosols, and Technosols) represent less than 2% of all soils (see Figure below).
WRB Soil map of NW Thailand.
Eelaart, A. L. J. van, 1974. Climate and crops in Thailand. Soil Survey Div. (DLD), Report SSR 96: 41p., Bangkok, Thailand.
Köppen, W. S., 1923. Die Klimate der Erde. Walter der Gruyter, Berlin.
Kubiniok, J., 1999. Reliefentwicklung, Pedogenese und geoökologische Probleme agrarischer Nutzung eines tropischen Berglandes – das Beispiel Nordthailand. Zeitschrift für Geomorphologie. Neue Folge. Supplementband 117, Borntraeger, Berlin, Stuttgart.
Landon, J., 1991. Booker tropical soil manual. A handbook for soil survey and agricultural land evaluation in the tropics and subtropics. Longman Scientific and Technical, England.
Schuler, U., 2008. Towards regionalisation of soils in Northern Thailand and consequences for mapping approaches and upscaling procedures. Hohenheimer Bodenkundliche Hefte 89: 1-308.
Schuler, U., Erbe, P., Bock, M., Willer, J., Ingwersen, J., Stahr, K., Herrmann, L., 2012. Comparison of medium scale and scale independent soil mapping procedures in northern Thailand for soil data generation in a development oriented context. In: Schreinemachers, P., Fröhlich, H., Clemens, G., Stahr, K., (editors), 2012. From challenges to sustainable solutions in mountain development. Springer. (accepted).
Trewartha, G.T., 1968. An introduction to climate. Fourth edition. McGraw-Hill, New York, USA.
|© Ulrich Schuler