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5.Differentiation and dynamics of land-use systems in a mountainvalley environment: a area, case study of new colonization areas in the Upper Mae Nam Pa Sak Catchment Thailand

Development of land-use systems

Agricultural production conditions in the study area
Land clearance and emergence of present land-use systems
Problems and potential avenues of development of present land use

Land-use development in the Scarp-Valley zone

The traditional land-use system
Clearance of the Scarp Zone and intensification of farming in the Valley Zone



Robert Riethmuller

Development of land-use systems

Agricultural production conditions in the study area

Forest clearing and pioneer settlement in Thailand is a rather multifaceted process. This is expressed in a wide variety of natural agricultural production conditions (soil quality, agroclimate) and in the many different social groups concerned. A rather heterogeneous case study area with regard to physical environment and social groupings should be selected in order to study the various aspects of this process. Accordingly, the area studied and described here incorporates a wide variety of physical and socio-economic conditions which have influenced the process of land clearing. Questions to be asked are, What social groups have developed what types of land-use system in what specific natural setting? Finally, the question is raised as to the degree of economic and ecological stability of the different systems.

The area studied constitutes part of the Thai maize belt, which occupies an almost closed area stretching from Phitsanulok in the north down to the province of Nakhon Ratchasima in the south (fig. 1). The topographic character of this area is mountainous in the east whereas the western and southern regions show low undulating plains interrupted by craggy limestone ridges and buttes. With the exception of the Pa Sak river valley, there are hardly any natural areas suitable for wetrice cultivation. This has meant that the zone, located in a fringe position between the two main regions of the Mae Nam lowlands and the Khorat plateau, was not settled and remained forest until recently. Its peripheral location correspondingly resulted in a fringe position in terms of economic and historical importance.

FIG. 1. Maize growing areas in Thailand, 1978/1979 (Ministry of Agriculture and Co-operatives. Agricultural statistics No. 108)

However, the rapid changes taking place in Thai agriculture over the last 30 years have meant that this area now has to be seen in a totally different light. The almost complete clearance of forest for commercial dry-land cultivation (maize) has converted the area into the most important district of cohesive new settlement, representing one of the leading agricultural production zones of the country. Average farm incomes in the maize belt are for the most part considerably higher than the national average, and the gross provincial products of cash crop provinces such as Lop Buri, Sara Buri, and Phetchabun show above average growth rates (World Bank 1980), a development that is reflected in the prospering district towns (e.g. district centres situated along the Sara Buri-Lomsak highway in the Phetchabun valley).

The important factors resulting in the rapid expansion of agricultural land into forest areas have been:

-the development of transport facilities, for example, the construction of main highways, followed by the development of feeder roads;
-commercial dry-land cultivation, which was encouraged by a strong foreign market demand (and was able to establish itself based on the following factor);
-the development of efficient marketing and supply structures and an effective system of partial mechanization (e.g. contract ploughing).

The province of Phetchabun has particularly profited from the above-mentioned processes. Phetchabun produces approximately 20 per cent of the national maize crop as well as a variety of other agricultural products for the national and international markets.

Phetchabun was able to profit greatly from the commercialization of agriculture, because it is an area of low population pressure; there was plenty of space for agricultural expansion (not only in the mountain areas but also on the high terraces of the Pa Sak river valley); and, third, the natural conditions and, most particularly, the fertile soils in Phetchabun favour agricultural production.

The Phetchabun mountains form a contact zone between the Khorat plateau and the depression of central Thailand. The Mesozoic orogenic processes caused numerous extrusions of volcanic rock, such as basalt, andesite, and rhyolite. Thus, soils developed in this area on parent material rich in mineral nutrients. This is true not only for soils which have developed on residual or colluvial material in the scarp and foothill locations but also for the alluvial soils in the flood zone of the valley bottom. The soils in the upper Pa Sak valley rank among the best alluvial rice soils in Thailand (Moormann and Rojanasoonthon 1972).

The agro-climatic situation varies substantially according to relief, exposure, and altitude. The average annual rainfall for the Phetchabun valley, which is located in the rain shadow of the western Phetchabun mountain ridge, is only 1,100 mm. The rainfall is much higher at the exposed higher altitudes. At a height of 750 m, on the Camp Son plateau, an average annual rainfall of 1,750 mm has been recorded for a 15year period; rainfall is distributed over a longer rainy season (from April to November rather than from May to October, as is the case in the valley). The lower temperatures are a decisive factor for many vegetable crops grown at the high altitudes of the Camp Son plateau.

The study area is approximately 2,000 km2 (fig. 2). It was selected because it contains the most important geomorphological units to be found in the northern part of Phetchabun province and also includes both traditional and pioneer settlement areas. The eastern part of the study area (I) includes a 50 km section of the north-western Phetchabun valley ranging from the district town of Lom Kao in the north to the provincial capital of Phetchabun in the south. The Phetchabun valley (with its rather narrow alluvial flood plain and broad, high terrace surfaces) represents the classic habitat for Thai wet-rice farming culture. The western part of the study area contains mainly pioneer settlement. It is mountainous and divided into:

-the scarp zone facing the Phetchabun valley (II);
-a high plateau (the Camp Son plateau) topped by a 1,700-m-high sandstone table (III); and
-the adjoining mountain zone gradually decreases in height in the west towards the Nan river in the upper central plain. This area is almost identical to the Thung Saleng Luang National Park and is the sole area to remain largely covered in forest.

Land clearance and emergence of present land-use systems

Information and details concerning the process of land clearance in the study area are essentially based on interviews and aerial photographs. Background information, such as on the social groups participating in the settlement process or innovations which had a decisive influence on developments at any one time, was gleaned from a survey.

Interpretation of aerial photographs, on the other hand, provided details about the spatial pattern of the expansion of agriculture. Photographs are available dating from the period 1953 to 1955 and 1967 (scale approx. 1: 50,000) and, of excellent quality, for 1975 and 1984 (scale approx. 1 :15,000).

Comparison of the aerial photographs and information given by locals enables us to determine the chronological sequence of changes of land use in both the Phetchabun valley (I) and the mountain zone (II-IV) as follows.

1955. Large scrub and secondary forest areas on higher terraces still surround the traditional alluvial wet-rice areas in the valley zone. The scarp zone and adjoining foothills are totally covered by primary forest. In the mountain zone (III) the typical pattern of shifting cultivation can he identified-Hmong farmers grow mountain rice and opium (sold to state-licensed opium dens).

FIG. 2. Lomsak-Khao Khor study area

Three small Thai hamlets (settlers from Dan Sai, Loei Province) with a small wet-rice area are already established on the Camp Son plateau. There is supplementary dry-rice cultivation and gathering of forest products.

1960. Completion of two strategic highways: Phitsanulok-Lomsak-(Loei), construction period 1955-1959. Slightly later upgrading of the Sara Buri-Lomsak highway through the Phetchabun valley and the road from Phetchabun via Chon Daen to the railhead of Tapan Hin (previously old ox-cart tracks). This meant that a good road transport network was established for the first time, linking the Phetchabun valley with the central plain and making the difficult transport by river barges and ox-carts superfluous and allowing for a sharp reduction in transport costs.

After the completion of road construction, a large number of road workers settled in the area of the Camp Son plateau (which owes its name to the location of a road construction camp). Additionally, large areas fell into the hands of influential absentee landlords, mainly from military and business circles in Bangkok, as also happened along the Friendship Highway. However, attempts to establish American-type large-scale cattle ranching proved unsuccessful after some years. In the mid-1960s these lands were already being cultivated by small-scale maize farmers.

Maize cultivation expanded along a corridor on both sides of the highway and around the older Thai hamlets. It was also beginning in the terrace and scarp foot zone in the Pa Sak valley.

1970s. The 1970s are characterized by:

-a considerable expansion of maize cultivation into the scarp zone (II);
-the crop pattern being diversified and intensified in the valley zone (I). Double cropping is becoming established in the wet-rice areas. Innovations: dug and tube wells, pump irrigation. Replacement of animal traction by single axle tractors. New crops: tobacco (burley variety) from 1972 onwards as a high input/high return crop, besides vegetables, mung beans, peanuts, and soya beans;
-market gardening: at high altitudes on the plateau.

1970 onwards:

-extensive expansion of maize cultivation as a result of high maize prices and the establishment of ploughing by contractors. Numerous new settlers from the neighbouring Phetchabun valley and also from the maize cultivation area around Pak Chong;
-the scarp zone (II) for the first time also becomes the target of clearance measures and in the course of the next 15 years will become almost completely opened up for maize cultivation. The area is being cleared by farmers mainly from the adjacent wet-rice villages who incorporated dry-land cultivation in the wet-land farm system. The scarp zone has already been opened up by forest concessions (lumber tracks).

1973-1975. Introduction and "booming" expansion of market gardening (cabbage) on the Camp Son plateau. After the influx of maize farmers, a second wave of settlers (mainly from areas of commercialized agriculture, e.g. Phitsanulok, Phichit, Nakhon Sawan provinces) and seasonal labourers (from poor rice subsistence areas, e.g. Khon Khaen, Chaiyaphum provinces) move into the study area and specialize in market gardening. Agricultural production is intensified along perennial streams and around the market village of Huai Phai; the Camp Son plateau becomes the most important cabbagegrowing area in the country (supplying the Bangkok market). The increase in permanent and seasonal population encourages growth in the market village, resulting in a sharp increase in shops and services.

1975-1976. High-altitude market gardening suffers set-backs due to exceptional frost (December 1975) and flooding (April 1975). A large part of the cabbage crop is lost; most growers and their traders lose their invested capital and are obliged to give up in debt. Fifty to seventy per cent of the vegetable growers leave the area: many move to Pak Chong, on the Friendship Highway, which is to take over from Camp Son in the late 1970s as the most important cabbage-producing area. Diminishing local purchasing power results in many shops closing down in the market village.

1980-1984. Consolidation of vegetable cultivation land on a lower level, diversification of vegetable crops cultivated (peas, broccoli, onions, carrots).

The southern part of the study area is characterized by a unique development. Between 1967 and 1981 communist Thai insurgents were able to erect a chain of strategic strongholds in the inaccessible heights of the western Phetchabun range by winning over as allies some of the resident Hmong hill tribes, who were largely neglected by the central government. The southernmost point of these strongholds (securing the supply line to Laos) consisted of the area around the 1,175 m Khao Khor mountain peak. The government troops' successive attempts to drive back the insurgents proved unsuccessful because of the mountainous, densely forested terrain. Thus, the area controlled by the army was largely restricted to the bigger roads (e.g. PhitsanulokLomsak Highway) and the surrounding cleared areas. As far as the army was concerned, forest clearance by pioneer settlers meant a welcome increase in areas easy to control and a decrease in areas giving strategic advantages to the guerillas. Therefore, forest clearance was partly backed by the army, or at least happily tolerated, in sharp contrast to some other government agencies, in particular the Forest Department.

From 1979 onwards the army populated areas where they had gained control with farmers voluntarily settled in strategic hamlets. Military efforts to eliminate the Khao Khor guerilla stronghold finally succeeded in spring 1981 with a largescale military operation. The concept of "strategic hamlets" was later applied to the whole area formerly under the control of communist insurgents in order to prevent their reinfiltration. A total of 35 villages with 50 families each were set up at even distances along the only road through the area. The settlers came from neighbouring provinces and were selected mainly according to the criterion of landlessness, priority being given to former soldiers. Due to this planned settlement project, land clearing has been pushed into the forested mountain zone (IV), where the soil conditions (red-yellow podsolic soils on sandstone poor in mineral nutrients) are not nearly as favourable as in the other zones. This presents a problem particularly since the settlers are only allotted a 20-rai (3.2 ha) plot of land. The settlement project is suffering from the inflexible approach used by the military planners to determine the location and lay out differences in soils, relief, and access to streams as a necessity for irrigated vegetable cultivation.

1984. The administrative status of the area is upgarded when it is declared an independent district (King Amphoe), going hand in hand with a noticeable improvement in infrastructure (roads, schools, health centres). The district incorporates the older spontaneously settled area of the Camp Son plateau and the area of the settlement project formerly controlled by the communist insurgents. The new district, "Khao Khor," has an area of 610 km2 and a registered population of 21,500, of whom 8,000 live in the settlement project.

1985. The forests in the area studied have largely been cleared, with the exception of the more than 1,000-m-high sections of hill evergreen forest in the north (which is a reserve for Hmong shifting cultivation), small, extremely steep parts of the upper scarp zone (although there is constant pressure on the part of the farmers to clear these areas), and large areas in the south of the project area (which is still under strict control of the authorities).

The regional pattern of land-use systems and farm types shows a general eastwest differentiation, corresponding to geomorphological zonation (zones I-IV). Furthermore, a marked north-south differentiation can be found in the plateau zone (III) which is due to the different settlement processes (spontaneous versus planned settlement).

Table 1 indicates the sequence of land-use systems and farm types that can be observed, beginning from the valley floor.

Problems and potential avenues of development of present land use

The dominant land-use system of permanent rain-fed agriculture practiced in the study area exhibits all the signs of a system endangering and exhausting resources ("soil mining"). It is characterized by:

-maize monoculture with high nutrient consumption and without the use of fertilizers, either mineral or organic;
-the practice of tractor ploughing on steep slopes (25-35 per cent), downhill only; no ploughing along contours.

The oldest areas constantly tilled in this manner for the last 25 years are situated near the market village of Huai Phai along the Phitsanulok-Lomsak highway (Ill). The soils are impoverished to a large degree (the colour has changed from dark brown to greyish yellow) and the hilltop and upper slope soils have become extremely shallow. Maize cultivation has been abandoned during the last five years and is no longer profitable even with the application of mineral fertilizer. The farmers have changed to intensive vegetable cultivation, although the maize farmers generally tend to postpone the decision to switch to the capital-intensive farm system of market gardening (high input of pesticides and fertilizers, motor pumps).

TABLE 1. Sequence of land-use systems and farm types

Location Land use Farm type
Middle part of valley, flood plain of the Pa Sak river, line of older Thai rice villages on river levees Wet-rice areas and labour- intensive vegetable cultivation in the dry season in rotation with legumes Generally rice, vegetable farms; no large animal hus bandry
Scarp and adjoining valley zone, line of younger Thai rice villages located at mountain stream outlets Wet-rice cultivation with second crop of tobacco, mung beans, peanuts; maize cultiva- tion (mung beans as catch crop) in the scarp area Generally combined wet/ dry land farms; no large animal husbandry
Mountain zone, divided from north to south:    
(a) Altitude more than 1,000 m, at present still areas of ever- green forest Shifting cultivation of Hmong; fallow system in transition to permanent upland cultivation Mountain rice; maize farms(maize as cash crop)
(b) Camp Son plateau 700-800 m Maize cultivation, market gardening, highly specialized orchards (with cut flowers) Maize farms; specialized vegetable farms; capital and labour-intensive large tree-crop farms present but not typical
(c) Khao Khor, settlement area 700-1,000 m, edaphic conditions varying greatly Previously shifting cultivation areas in part, in part primary forest; at present, maize cul tivation dotted with irrigated vegetable cultivation 20-rai (3.2 ha) settler farm in project area

Fallow areas (covered with Imperata cylindrica) have greatly increased, but a four-year crop rotation system of vegetable-maize-fallow-fallow seems to be developing, made possible by a more intensive type of cultivation along streams where irrigated vegetables (e.g. cabbage, broccoli, carrots, onions, peas) can be grown all year round.

In the remaining area of the plateau zone, where maize cultivation is still profitable despite decreasing yields and increasing input costs (tractor ploughing), the differentiation between maize farms and specialized vegetable farms is still typical. The vegetable-growing areas are rotated to avoid pests, and the maize crop following the highly fertilized vegetable crop is able to benefit from unused nutrients in the soil. Maize and vegetable cultivation complement each other in a near symbiotic form, which is also reflected in the low rents the normally landless vegetable farmer pays to the owning maize farmer. The tendency of land use in this zone is to expand vegetable cultivation, which is also becoming more diversified. Generally areas with access to water will see an intensification of land use (four to five vegetable crops per year), whereas cultivation on the impoverished upper hill areas will become more extensive with intermediate fallow periods.

It may be that land-use conflicts will become more prominent in the north of the study area, where the demand for land is high in the Hmong shifting cultivation areas, as well as in the southern state-implemented settlement project area, where the farm size of 20 rai (3.2 ha) cannot provide a sufficient family income in those areas with red-yellow podsolic soils (zone IV). The foresters of the adjoining Thung Saleng Luang National Park are very much concerned that settlers will look for additional farm land within the park boundaries as soon as the present strict supervision by settlement authorities slackens.

However, the most endangered zone in ecological terms is the steep scarp (II) facing the Phetchabun valley, forming an ecologically sensitive upper catchment area for the whole valley region. The developments in this zone have not received much attention from official bodies up to now, since the authorities are mainly concerned with the development of the settlement project in zone III.

The second part of this paper will, therefore, concentrate on this zone and investigate in more detail the process of land clearing, the emergence of the present land-use system, and its repercussions on the sensitive scarp-valley ecosystem.

Land-use development in the Scarp-Valley zone

The traditional land-use system

The changes taking place in the scarp-valley zone were examined, taking the Ban Bung Nam Tao community as an example (see fig. 1). This community consists of nine villages with a total of 905 families and 4,924 inhabitants (figures from 1984). The division into nine villages is merely an administrative one and in fact the villages have split from one and the same historical core and even today appear as a single closed community stretching along a small stream surrounded by its wet-rice fields. The historical core is about 100 to 150 years old and lies in the middle of what is now Ban Bung Nam Tao, surrounded by the most fertile wet-rice lands and easily identifiable by the stands of dense and tall fruit trees on the farmhouse plots. The village has expanded in both directions along the stream. The most recent growth took place in the direction of the Lomsak-Sara Buri highway, which bypasses the village to the south. The growth of the community has been a result of a natural increase in population; inmigration from other areas has remained slight.

Bung Nam Tao can be considered as a typical village for the second line of traditional wet-rice settlements in the upper Pa Sak valley. These villages are all situated at points where streams flowing down from the scarp enter the valley zone and leave fertile alluvial fans between the older terrace areas. The topography and soils here are well suited to simple gravity irrigation systems such as those typical in the intramontane basins in the north of Thailand. Fertile alluvial soils and plenty of space for the expansion of agricultural land have meant that the villages along the scarp zone have always been well provided with natural resources, making surplus production possible even from the earliest times. However, marketing and transport restrictions formerly inhibited increases in surplus production. Traditional market crops were tobacco and chill) in limited quantities and small surplus productions of brown sugar. In addition, cattle and water buffalo were kept and traded in considerable quantities.

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