1 - Overview
2 - Introduction to the area
3 - Geology & Climate
Granite
Climate
4 - Vegetation
5 - Forest Types
Vegetation
Tea/Miang Plantations
Forrest Conservation
6 - The Pang Soong Treewalk
7 - Treespecies
Fig Trees
Epiphytes
Saprophytes
Bamboo
Click here for full tree list
8 - Forest Fires

9 - Birds
Observing Birds
10 - Bird Trail Walk
11 - Mammals
Mammals of Northern Thailand
Mammals of Pang Soong
12 - Insects
Introduction
13 - Projects
Observing Birds & Mammals
Watching Birds, makung use of Observations
Identification
Behaviour
Mammals
14 - Biographies of contributing experts

The entire mountain is composed of Triassic granite that was formed c. 200 million years ago (Baum et. al. 1982). This was originally a plutonic (underground) formation of magma, which subsequently cooled.
The mountain began to be uplifted due to the Himalayan orogeny, which started c. 50 million years ago and is still continuing. Millions of years of slow uplift, earthquakes, and erosion have created the present landscape of steep slopes, watercourses, cliffs, boulders, and drainage. The present forest cover is much more recent, perhaps a few thousand years old. Previous vegetation consisted of ancient, now extinct components. The past million years have included extant plants which, because of climatic fluctuations, have often included more pine facies than now.

GRANITE

Doi Lohn is composed entirely of granite bedrock. Granite consists of three minerals, which vary in concentration, size and sometimes colour. The granite on Doi Lohn is quite uniform and consists of three crystalline minerals: Quartz (SiO2), which is whitish to white, two kinds of mica (muscovite – white mica, KAl2(A1 Si3O10 (OH, F)2 and biotyte – black mica K(Mg, Fe)A1Si3O10 and in thin layers), and feldspar (KAlSi3O8 being whitish). This rock is typically hard, fractures irregularly and has obvious particles of the three minerals throughout.

Quartz, the hardest of the three components, is melted to make glass and fine particles (sand) are used in concrete construction. Feldspar, almost as hard as quartz, is used as a matrix and glaze in the ceramics industry, and mica, the softest mineral, is a common ingredient in cosmetics and lucite (a reflecting surface enamel).

Eons of chemical (mainly rain) and physical weathering (e.g. wind, earthquakes) have eroded much of the bedrock where many outcrops are visible. The presence of gravel and large boulders is also evidence of this eternal process. Granite weathers in a unique manner that results in smooth, rounded surfaces. This exfoliation is caused by the chemical decomposition of feldspar that causes the granite to crack in onion-like layers and break off. Repeated breaking of granite ultimately results in isolated pieces of quartz and flakes of mica, which are easily seen on eroded slopes and in streambeds along with sand. Feldspar may also be isolated, but mostly it has decomposed into clay, (specifically kaolinite and illite), which is a basic component of soil. Biological activity producing nitrogen and carbon compounds combined with clay has produced soil, enabling vegetation to grow. The geological cycle has resulted in the development and evolution of land life. Severe erosion of soil reverses this process so that nitrogen and organic matter are washed away or volatilised (especially during fires) and clay to be similarly removed by water or aggregated into infertile laterite.

Doi Lohn is also known to have scattered deposits of cassiterite (SnO2), a source of tin, especially in streams. This mineral has been deposited long after the original granite has been hardened and been cracked by earthquakes, thus allowing the mineral to be intruded into the rock.

CLIMATE

The climate of northern Thailand is distinctly seasonal (monsoonal) with three seasons. There is a hot-dry period from March to May, a rainy season from May to October and the cool-dry period from November to February. Daytime peak temperatures in April commonly reach 35°- 40ºC in the lowlands (350 m at Chiang Mai), while the overnight temperature in December-February can drop to 10º. Mae Lai Village, because of its elevation and forest cover, is considerably cooler than the lowlands.
Mountains above 2000 m elevation frequently have frost at night during the cool-dry season.

Rainfall is most abundant from July to September, and sometimes there is none during the hot dry season. Maximum precipitation is 325 - 400 mm per month during the rainy season, (based on 30 years of rainfall data from Doi Suthep, the mountain on the west side of the Ping River basin). The annual average rainfall at Mae Lai Village is c. 1700 mm and over 2000 mm on the summit of Doi Lohn.