4.1 Macro-level Land Resource Utilization Assessment: Thailand

Thailand is located in the central part of the Indochina Peninsula. Thailand is one among the most developed and wealthiest country in Southeast Asia. The total area of the country is about 513,115 sq. km. The total population of Thailand is about 58.34 million (Ongsomwang, 1995) with a population density of 113.7 persons per sq. km. Due to its diversified topographic characteristics, the country has been divided into six physiographic divisions viz. Central plain, Southeast coast, Northeast plateau, Central highlands, North and West continental highlands and Peninsular Thailand.

Thailand is well endowed with natural resources such as forests, agricultural land, waterbodies, marshland, swamp, beach and pasture land. Both evergreen and deciduous forests are abundantly found in various parts of the country. Both freshwater and mangrove swamp forests are found in various parts of the country. From the analysis of multi-temporal/multi-seasonal NOAA AVHRR data, it was found that the forest cover of Thailand is approximately 30.17% of the total land area. This includes evergreen, deciduous and mangrove forests. Cropland is the most dominant land cover type that occupies more than 56% of the total area. Waterbodies, which include dams, rivers, lakes and water depressions cover less than 1 % of the total area.

The change in land use/land cover types in Thailand is characterized mainly by the change of forest areas to non-forest areas. Although forest concession was banned in January 1989, about 0.24 million hectares of forest area have been depleted during 1985/86 to 1992/93. The major causes of the forest area depletion are encroachment, shifting cultivation, commercial logging and forest fire. Encroachment of forest lands for other land uses due to intense population pressure is one of the principal cause of deforestation. The reasons for the mangrove forest destruction, in particular, is due to shrimp farming, salt farming, expansion of agricultural land and mining activities in the coastal areas.

Realizing the rapid pace of deforestation, a number of efforts have been taken by the Royal Thai Government to conserve the forests and forest biodiversity of Thailand. In 1985, the National Forest Policy was formulated which emphasized on interagency co-operation, involvement of the private sector, improved and flexible administration. In 1987, the Royal Forestry Department classified the mangrove land use zone and established the urgent strategic management measures for the mangrove forests and coastal resources including coral reefs. Protected areas in Thailand are relatively well represented. Law enforcement on logging, encroachment, collecting and hunting inside the parks needs to be improved. After the establishment of Thailand's first national park in 1962, the growth of national parks has been increasing.

4.2 Study Area Location

Loei is one of the 17 provinces (Changwat) of the Northeastern (Isan) Region of Thailand, which is about 520 km from Bangkok. The province is boardered with Lao P.D.R. in the north, Udonthani and Nongkhai provinces in the east, Khon Kaen and Phetchabun provinces in the south and Phitsanulok province in the west (Fig. 4.1).

The climate of Loei province is relatively warm in the summer and cool in the winter. This is the only place in Thailand where temperature drops below 0⁰ C. The general climate of the province has been classified as "Tropical" with the seasonal variation of temperature and rainfall. From November to February, cold and dry air flows into the region from China and from May to October, the southwest monsoon brings a stream of warm moist from the ocean. The southwest monsoon causes considerable rainfall over much part of the province.

Administratively, Loei has been divided into 12 districts (Amphoe), 89 communes (Tambon), 784 villages and 1 municipal area (Statistical Report of Cgangwat, 1994). The total population of the province is 574,956 persons with a population density of 503.30 persons per square kilometers (Statistical Report of Changwat, 1994).

The province is characterized by numerous hill and mountains that resembles with the Northern Region of Thailand. It also consists of valleys running along the rivers. Soils of Loei province are composed of the following types.

a. Soils of recent alluvial plains of variable width along the rivers. They occur only in the valleys of the northern mountains.
b. Soils of nearly level low terraces of semi-recent alluvium. They are widespread in the basins and valleys of the northern mountains
c. Soils of undulating to rolling old alluvial terraces and fans. They are also widespread in the basins and valleys occurring in higher positions than the low terraces of semi-recent alluvium.
d. Soils of undulating to hilly areas derived from erosion of surface and lava flows, occurring mostly in form of hills and mountains, bordering the alluvial plains and,
e. Soils on the hills and mountains that make up the greater part of the region. The soil condition in this area is relatively poor.

The total forest area of the province is 7,062.89 square kilometer. There are five national parks, 1 wildlife sanctuary and 20 reserve areas. From the management point of view, forest area has been classified into three broad categories as follows.

• Reserve Area - Resource use is prohibited;
• Economic Area - Allowed to harvest the selected economic products and;
• Agricultural Area - Allowed to cultivate agricultural crops.

Transplanted rice is the predominant crop in the river basin and in the valleys. Some part of the paddy cultivated areas composed of recent or semi-recent alluvium with

abundant moisture are being used for the cultivation of soybean, sugarcane, tobacco, maize, peanuts, vegetables and fruit trees including longan and mandarin oranges. Shifting cultivation is common in the areas which is being practiced on the old alluvium terraces and fans for cultivation of upland rice, maize, groundnut, beans, and cassava.

4.3 Datasets and Methodology Used

4.3.1 Datasets

Remote sensing and GIS technology was used for the data analysis. SPOT multispectral satellite data acquired on March 21, 1996 was used as the principal source of information to derive present status of land use/land cover in the study area. A False Color Composite of SPOT XS data is presented in Fig. 4.2. One Landsat scene of 19 December, 1985 was acquired to carry out the change analysis. Other secondary information such as topographic maps, soil map, district and provincial boundary map, geological map, land use map, main transportation network and main river & canal network map, etc. were collected from various sources and used in the present analysis.

4.3.2 Methodology

An intensive field trip of six days was conducted on November 1995 approximately three months prior to the date of acquisition of the satellite data used. Representative samples of the study area consisting of a number of sample plots were inumerated. In each sample plot, information such as agricultural crops, cropping patterns, management regimes, dominant vegetation types, topography, soil type, slope, accessibility etc. were collected. Global Positioning Systems (GPS) was used to position ourselves in the satellite imagery. Unstructured interviews with the villagers were also conducted to gain understanding on the various aspects of agricultural practices.

The SPOT XS image was spatially georeferenced to a Universal Transverse Mercator (UTM) map projection using a non-linear polynomial and resampled with nearest neighbor algorithm. Ground Control Points (GCPs) were selected from the 1:50,000 scale topographic maps. A RMS (Root Mean Square) error of ±1 pixel (±20 m) was accepted during the non-linear rectification.

A hybrid approach of supervised and unsupervised classification was deployed in the study. Isodata clustering and iterative labeling was used during the unsupervised classification. Training areas based on the field observation were utilized for the supervised classification. ERDAS Imagine, an image processing software, was used for the analysis. The information obtained from the unsupervised clustering was used during the supervised classification. The classified map was converted to vector format for further GIS analysis using ARC/INFO 7.0.3 software.

The flow-chart of the methodology used is shown in the figure 4.3.

For the change analysis, Landsat MSS data acquired on 19^th December, 1985 was used. The image was georeferenced to UTM projection with a RMS error of ± 1 pixel. Later it was resampled to 20 meter resolution to make it consistent with SPOT XS resolution. Visual comparison was performed for both Landsat and SPOT imageries.

GIS database was created for different biophysical parameters. The database is in vector format. Spatial analysis was performed using ARC/INFO GIS interface.