Land-Use Change and the Structural Dynamics of Pinus kesiya in a Hill Evergreen Forest in Northern...

Land-Use Change and the Structural Dynamics of Pinus kesiya in a Hill Evergreen Forest inNorthern ThailandAuthor(s): Melissa SavageSource: Mountain Research and Development, Vol. 14, No. 3 (Aug., 1994), pp. 245-250Published by: International Mountain SocietyStable URL: http://www.jstor.org/stable/3673775 .

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MOUNTAIN RESEARCH AND DEVELOPMENT, VOL. 14, No. 3, 1994, PP. 245-250

LAND-USE CHANGE AND THE STRUCTURAL DYNAMICS OF PINUS KESIYA IN A HILL EVERGREEN FOREST IN NORTHERN THAILAND

MELISSA SAVAGE

Department of Geography University of California, Los Angeles

Los Angeles, CA 90024-1524

ABSTRACT This study describes changes occurring in a stand of Pinus kesiya in hill evergreen forest adjacent to a new settlement of tribal people in the Doi Inthanon mountain region of northern Thailand. These forests are increasingly experiencing chronic human impacts as tribal people are settled permanently at one site by government programs which encourage the cultivation of cash crops in place of opium. Results from age stand structure analysis suggest that two factors, human-set fires and kindling stick harvesting, are now severely affecting the age distribution of Pinus kesiya in the mixed pine and evergreen hardwood forest.

RESUME Changement d'utilisation des terres et dynamique structurelle d'une une fornt de pin montagnarde de la Thailande septentrionale. Cette 6tude d6crit les changements qui ont affecte un peuplement de Pinus kesiya situb dans une foret sempervirente adjacente a une nouvelle collectivit6 tribale 6tablie dans la r6gion montagneuse de Doi Inthanon, en Thailande septentrionale. Ces for&ts sont de plus en plus sujettes a des impacts humains chroniques au fur et i mesure que des collectivites tribales s'6tablissent en permanence sur certains sites, dans le cadre de programmes gouvernementaux encourageant la culture de denrees commerciales plut6t que de l'opium. Les r6sultats d'une analyse structurale du peuplement de pins suggerent que deux facteurs, les feux de foret allumes par les habitants et la collecte du petit bois de chauffage, affectent enormement la distribution par age de Pinus kesiya dans la foret sempervirente mixte de bois durs.

ZUSAMMENFASSUNG Landnutzungsiinderungen und strukturelle Dynamik eines Kiefernwaldes im Gebige von Nordthailand. Diese Studie beschreibt Verinderungen in einem Kiefernwald in der Doi Inthanon Gebirgsregion von Nordthailand, an den eine neue Siedlung mit einheimischen Bewohnern angrenzt. Diese Waldflichen sind mehr und mehr menschlichen Dauerbelastungen ausgesetzt, da die einheimische Bev61kerung durch Regierungsprogramme ermutigt wird, sich an einem Ort fest anzusiedeln, um Gartenfrfichte statt Opium anzubauen. Einige Kiefernstinde in diesem Gebiet haben als gleichaltrige Gruppen den bestandszerst6renden Einflfissen widerstanden. Eine Analyse dieser Bestinde deutet darauf hin, daB zwei Faktoren die Altersverteilung der "Pinus kesiya" gravierend beeintrichtigen: Von Menschenhand verursachte Feuer und die Feuerholzgewinnung. Versiumte Aufforstung der Kiefernwiilder und die geringere Feuerempfindlichkeit von breitblattrigen Arten deuten auf den Trend, daB in der Zukunft Kiefernwalder durch breitblattrige Baumarten ersetzt werden.

INTRODUCTION

Change in the forest landscape of the hills of northern Thailand has been profound in recent decades. Two anthropogenic factors have played a role in this landscape change, spontaneous settlement of the region by mountain tribal people, and the response of the Thai government to this migration by instituting a series of development projects. These projects are a result of concern about environmental damage and forest clearance by hill tribes, many of whom historically raised the opium poppy in a shifting mode of agriculture known as swiddening. While there is a wide variety of serious socioeconomic as well as environmental problems in the northern mountains, the majority of governmental mitigation efforts have been directed at the clearing of montane forests. Researchers have chiefly pursued studies that use remote sensing data to characterize the reduction of forested area (e.g., Pandee and Chapman, 1983). By contrast, changes in the conditions and structure of remaining natural forests have been little studied.

Thailand is in the midst of a deforestation crisis. In recent years, it has had the highest deforestation rate of any Southeast Asian country (Hirsch, 1990). By one account, total percentage of the country under forest declined from 53% in 1963 to 15% in 1986 (Hirsch, 1987). In 1989 the Thai government banned logging entirely. Although there is a broad historical pattern of logging, beginning with teak timbering in the 19th century, and continuing illegal logging and widespread clearing of forests for expanded agriculture, the government has recently chosen to focus on environmental problems of hill tribe agriculture and forest clearing. Underlying this concern have been broader political objectives, such as the elimination of the cultivation of opium, made illegal in 1959.

Foremost among development projects has been the crop substitution program, which sought to replace opium with other crops such as coffee, flowers, and temperate zone fruits and vegetables. While meant to

? International Mountain Society and United Nations University



246 / MOUNTAIN RESEARCH AND DEVELOPMENT

accomplish in one stroke the elimination of opium, the reduction of forest clearing by ending shifting cultivation, and the settling of nomadic hill tribes, crop substitution programs have not been notably successful. The Royal Forest Department has also initiated reforestation projects to replant abandoned swidden areas and Imperata (Imperata cylindrica (L.) Beauv.) grasslands, primarily with the native three-needled pine Pinus kesiya. Pine planta- tions, it was hoped, would reduce erosion and provide a source of timber and fuelwood.

The study reported here investigates changes occurring in a natural forest adjacent to a new settlement, Ban Bah Gluay, established by migrating Hmong tribal people in the Doi Inthanon range in 1973. The village is now part of Obluang National Park. The Hmong villagers at first raised opium in the region, moving frequently to clear small areas for slash-and-bumrn cultivation. Persuaded to change from opium to cabbages as a cash crop, the

Hmong are now settled on the site and cultivate two crops of market vegetables a year, with intense use of pesticides and fertilizers. The Hmong still have a mixed economy, however, and not only raise some subsistence crops, but also use the nearby forest to graze cattle and gather fuel. Whereas in former times, they used the natural forests adjacent to villages only as long as the land would support an opium crop, now the local hill people use the forest on a more continuous basis.

The objective of the present study is to investigate the effect of Ban Bah Gluay villagers on stands of Pinus kesiya in a mixed pine and evergreen hardwood forest. The condition of the pine stands is characterized through stand age structure and an assessment of damage to living trees. Results suggest that the structure of pine popula- tions under anthropogenic disturbance is dynamic, and that the relationship of the local villagers to their forests is not stable.

HMONG MIGRATION

The shifting demographies of hill tribes in recent times are the result of both in-migration across national bor- ders and a high birth rate. The Hmong began to appear in northern Thailand at the end of the nineteenth century, as a territorial expansion out of their homeland in southern China and Myanmar (Burma) initiated a southern migration prompted by political unrest. They now constitute the second largest tribe in the region, after the Karen, and represent about 11% of highland minorities (Santisuk, 1988). The Hmong population is growing rapidly. The natural growth rate is high, generally doubling in each generation, and in-migration has increased since the 1970s, particularly from Laos (Kun- stadter and Chapman, 1978).

The Hmong tended to settle spontaneously at relatively high elevations in the Thai mountains, generally above 1,000 m because the opium poppy could be grown at this elevation. Newly cleared fields are usually small, and are used to raise poppies until soil fertility declines. Succes- sion is often to a secondary forest (Elliott, per. comm.). Because of the cost to soil nutrients, traditional methods

of opium cultivation have been considered by some to be a damaging form of swiddening (Kunstadter and Chapman, 1978).

The mountain ranges extending into Thailand from China became the home of many Hmong in this century. Opium and maize were long traditional crops for the Hmong, but they were well positioned to participate in the boom in Thai opium production and trade which peaked in the late-1970s. Intense government efforts to reduce opium production began in the 1970s and had largely succeeded by the mid-1980s. The Doi Inthanon region, which includes several national parks, was the target of numerous government mitigation programs. Crop substitution programs settled the Hmong permanently in the hill forests, where they began to exert chronic pressure on nearby forests. Among other activities, they harvested resin-inpregnated kindling sticks from pine trees for sale in lowland markets and, using the traditional tool of swiddeners, fire, ignited the forests in the dry season to produce a tender ground flora for their cattle.

MONTANE VEGETATION

Pinus kesiya has a relatively limited distribution in this region. It is found in mixed evergreen hill forests and can dominate stands on the well-drained narrow ridges and steep slopes that descend from mountain ranges (Smiti- nand et al., 1978). The species is widely distributed, from India and southern Xinjiang through Myanmar to parts of Thailand, Laos, and Vietnam, and grows in patches, generally between 850 and 1400 m elevation (Mirov, 1967). P. kesiya is found in open stands growing with many broadleaf hardwoods, such as Castanopsis argyrophylla, Lithocarpus acuminatissima, Anneslea fragrans, and Engel- hardtia spicata and grass and forb ground cover (Kuchler and Sawyer, 1967; Maxwell, 1988).

Above the zone where pines occur on Doi Inthanon is a moist evergreen forest, with a closed canopy evergreen forest above about 1,800 m, often wrapped in a prevailing mist. The mixed evergreen and deciduous forests on the lower slopes, however, have been the site of extensive historical logging and slash-and-burn agriculture. Uncontrolled human-set fires now occur every year in much of the forest. Seedlings of both pine and broadleaf evergreen trees are killed by fire, and with increased burning frequency, forest stands become more and more open. Santisuk (1988) suggests that increased fire frequency may favor Imperata grass meadows, highly resistant to fire and invasion by woody species.



M. SAVAGE / 247

1000

C-

0 .5 1.0 Miles 5 I. l I

0 .5 1.0 Kilometers

FIGURE 1. Map of the Ban Bah Gluay study area, showing loca- tion of sampling transects (1-8).

STUDY SITE

The study area is located on the Mae Soi Ridge, at about 980 30' E. and 180 15' N., on the southeast flanks of the largest mountain massif in northern Thailand, Doi Inthanon (2,565 m). A typical monsoon climate prevails (Figure 1). The geologic structure of Doi Inthanon is primarily granitic, and the soils are mainly slightly acidic red and yellow podzols (Banijibatana, 1978).

The village of Ban Bah Gluay was established in 1973 by Hmong migrants on a ridge about 1,400 m in eleva-

tion. The study site is located in the nearest grove of native three-needle pine, P. kesiya, about one km away and 100-300 m lower in elevation than the village. A well- traveled unpaved road runs along the center of the main ridge, and virtually all secondary ridges have foot trails. Scattered cattle wander through the forest grazing on grass and tree foliage, and the sound of wood chopping and gun shots are common.

METHODS

Samples were taken from forest trees on a south-facing slope near the top of a pine-dominated ridge. Eight transects, ranging in length from 80 to 300 m, were located along secondary ridges which descend from the main ridge, from around 1,050 to 1,350 m (Figure 2). At points 20 m apart, the distance from the point and the diameter at breast height (dbh) of the nearest 4 adult pine trees (? 6 cm dbh), saplings (> 1.4 m in height but < 6 cm dbh), or seedlings (< 1.4 m in height) were recorded, using the point-centered quarter method (Cot- tam and Curtis, 1956). No individual was recorded if there was not a pine within 50 m. No first year seedlings were counted, since these are very vulnerable to fire mortality, and their fate is uncertain.

In addition, cores were taken from each live adult pine tree at 30 cm above the ground in order to construct stand age structure. Although these forests are sub- tropical, there is strong evidence that the severity of the dry season creates a clear annual ring growth. The ring count of cores taken from two P kesiya in the Doi Sutep- Pui National Park near Chiang Mai correlate closely with known dates of planting. The annual nature of rings in

0C (4-4) 22.40C 1343.2 mm 200

50- -100 40- -80

30 -60

20- -40

10- -20

J'F 'M' A M'J 'J

I

A' S IO'N' D

FIGURE 2. Climate diagram for the Mae Chaem Watershed Research Station, at 1,140 m and approximately 18 km from the study area. (Werner, 1993)




pines of the region is discussed by Werner (1993). Sample cores were mounted and sanded, and annual rings counted under a stereomicroscope, following the methods of Stokes and Smiley (1968). Ages of adult pines were expressed in a histogram of five-year age classes. In addition, twelve pine seedlings (~30 cm tall) were harvested and rings counted to obtain an average age for seedlings. Since average age of seedlings reflected rapid growth (X = 4 years), seedlings were placed in the 0-5 year class, and saplings in the 6-10 year class of the histogram.

In each point-centered quarter, the presence and size of any non-pine species occurring closer than the nearest pine were also noted. Average aspect and slope were recorded for each transect.

The condition of pine trunks was also recorded, as many tree trunks were damaged in several ways. Frequent anthropogenic fires have left varying degrees of char on tree trunks and roots. As an indication of fire presence in the stand, the percentage of samnle trees with soot was noted. Serious damage to trunks is caused by villagers' collection of splinters of kindling, which are bundled and brought to lowland markets. Trunks and roots are first chopped with an ax in order to cause resin flow into the wound (Figure 3). Resin-impregnated splinters of wood are then chopped off in successive visits until the trunk is so weakened that the tree falls. Damage from splintering was recorded as more than % or more than % of the trunk diameter removed, and as damage to exposed roots.

RESULTS

Data were recorded on 274 pine trees, including 251 adults. Ninety-one percent (229 trees) of the sampled adult trees were successfully aged. The distribution of age structure in the histogram (Figure 4) reveals that the remaining trees are extremely young. [The largest pine trees are usually taken for house building when settle- ments are newly established (S. Elliott, pers. comm.)] The oldest tree age obtained was 61 years, and the peak of regeneration occurred about 35-45 years ago. The stand is open with little understory and sparse regeneration, either of pine or other species (Figure 5). The density of P. kesiya, based on distance from transect point dis- tances, is somewhat sparse at 284 trees/ha. Pine cover, expressed as basal area, is also low, (X = .096 m2), at 27 m2/ha, reflecting the small size of pine trees. Many species of pines are opportunistic and will colonize disturbed sites. If this stand of Pinus kesiya regenerated as a cohort after some natural disturbance, then canopy shade may now be inhibiting pine recruitment, and encouraging more shade-tolerant species.

Damage to the pine stands from human activities appears to be severe, particularly in the youngest and oldest age classes. Although there are abundant first year seedlings several centimeters tall, there is a marked lack of survival into older seedling or sapling classes. Only 10 seedlings older than one year and 12 saplings of pine were found. P kesiya is generally resistant to fire only above = 3 m tall (Whitmore, 1984), and the fires that are now as often as annual appear to result in virtually 100% mortality of these first year seedlings. Seedlings of broadleaf woody species also appear to suffer similar levels of mortality, and young broadleaf plants may in fact be coppicing after fires (S. Elliott, pers. comm.). Charred bark or roots in 78% of all adult trees provides evidence of frequent fire. Charring from flames reaches as high as 3 m on trunks.

Attrition in the oldest age classes from human impacts is equally severe. Thirty-nine percent of all adult pine trees, 99 trees, showed some marks of chopping. Of these, 28% had more than % and up to / of the stem removed, 34% had more than %4 of the stem removed, and 23% had

their roots chopped.- The largest trees attract the most sustained splintering. Nearly 80% of pine trees with more than a quarter of the trunk removed were larger than 30

aa

- ~

r~s.

oo i 4L

Ix I?

? " qV,

FIGURE 3. Pine tree trunks are severely damaged by hacking of resin-imbued splinters by local hill people for sale as fire-starters in the market.



M. SAVAGE / 249 5 0 . . .................... ........................ ............

Pinus kesyia n = 251

4 0 ) . ................................................ ........... . . . . . . . . . . . . . . . . .

%40.-

0 . w L- c

- .. . . ... 20-

E o z 10- .I

S Age 0lassesL(ye0 rs

((b -(b b -a Cq N COJ CO) v v tn

Age Classes (years) FIGURE 4. Frequency of Pinus kesiya, seedlings, saplings and adults (> 1.4 m tall and > 6 cm dbh) in sample transects, in 5-year age classes. N = 251 trees aged by ring count, plus 12 seedlings and 10 saplings (Patterned bar). First year seedlings are not included.

I . 4.

m i,:,,% .... ,,,

.... .- ,,,

FIGURE 5. Pine stands near Ban Bah Gluay are very open and regeneration is relatively low.

cm in diameter. Chopped trees eventually fall and remain lying on the forest floor or are cut up for firewood.

Broad-leaved species form a sparse understory below the pine canopy. Non-pine species sampled include deciduous species Dalberigiafusca Pierre, Annesleafragrans Wall., Dipterocarpus tuberculatus Roxb. var. tuberculatus, and Buchanania latifolia Roxb., and evergreen species such as Quercus kerrii Craib. var. kerrii, Lithocarpus elegans (Bl.) Hatus ex Soep., and Castanopsis tribuloides (Sm.) A. DC. These species are normally found at lower elevations, and have followed frequent fire to this site (J. E Maxwell, pers. comm.). Ninety-four broad-leaved individuals were closer to the transect point than the closest pine at over half the transect points (37). The average basal area of these non-pine species was .057 m2, about half that of the pine basal area. Within the radius of sampled pine trees, 145 seedlings older than one year and 36 saplings of broad-leaved species were also counted.

The age structure of the pine forest, a young cohort which peaked in regeneration about 40 years ago, could reflect two histories. Either the forest regenerated after a disturbance, and recruitment is now tapering off

low

41,

vw i

Ar"!

FIGURE 6. Buddhist monks "ordain" large pine trees, hoping to deter cutting for fuelwood.




because of density, or the forest has been continually developing over time, and mortality in youngest and oldest age classes has caused an unbalanced age distribution. Whether or not the stand developed after a natural

disturbance, anthropogenic disturbances, including those that preceded the Hmong settlement, have created an unbalanced age structure.

DISCUSSION

The age structure in P kesiya stands near the village of Ban Bah Gluay suggests that a major shift in the forest landscape is occurring. In particular, the structure reflects the pressure of human agency in both the youngest and the oldest classes of trees. Recruitment of young pines at this site is adversely affected by either or both natural and anthropogenic factors. Recruitment is discouraged by the frequency of human set fires, while the oldest trees are seriously damaged by kindling harvesting. Attrition continues from both directions, leaving a mixed pine and evergreen forest that is increasingly sparse (Figure 5).

The use of the nearby forests by the local villagers will continue to alter the structure and composition of the pine forest landscape. The impulse for the conservation of forest resources, however, often begins with local people. In the pine forest near Ban Bah Gluay, for example, there is an annual Buddhist protection ritual that "ordains" large pine trees to protect them from the ax (Figure 6). As others have suggested (e.g., Ives, 1983), stable resource use often depends less on technical solutions than on local initiative such as this. Government programs in the mountains of northern Thailand have sought to solve a complex situation by focusing narrowly on the search for "the right crops". Social and cultural changes initiated by such programs not only change the

agricultural base for villagers, but also their relationship to an entire suite of natural resources. These broad changes are not easily addressed by narrow reforms.

Urban et al. (1987) point out that humans can influ- ence the pattern of the forest landscape in several ways, 1) by rescaling natural disturbances, and 2) by introduc- ing novel disturbances. Fire is often rescaled by human activities, as in this case, where the traditional cultural practice of frequent fire for swiddening is now used in the forest at large rather than as an agricultural tool. This, together with the novel disturbance of kindling splintering, has created an unstable structure in the forest near a Hmong village, and ongoing and drastic changes in the local forest landscape.

ACKNOWLEDGEMENTS

The author is grateful to the Dhammanat Foundation for Conservation and Rural Development and Mrs. Smansnid Svasti for permission to conduct research, and to Dr. Steven Elliott and Dr. J. E Maxwell of Chiang Mai University for species identification and numerous help- ful comments.

REFERENCES Banijibatana, D., 1978: Forest policy in northern Thailand. In

Kunstadter, P., Chapman, E. C., and Sabhasri, S. (eds.), Farmers in the Forest. University Press of Hawaii, Honolulu, pp. 54-60.

Cottam, G. and Curtis,J. T., 1956: The use of distance measures in phytosociological sampling. Ecology, 37: 451-460.

Hirsch, P., 1987: Deforestation and development in Thailand. Singapore Journal of Tropical Geography, 8:129-138.

, 1990: Forests, forest reserves, and forest land in Thai- land. The Geographical Journal, 156: 166-174.

Ives, J. D., 1983: Preface. Natural resource development and environmental stability in the highlands of northern Thailand. Mountain Research and Development, 3(4): 309-311.

Kuchler, A. W and Sawyer, J. 0., 1967: A study of the vegetation near Chiang Mai, Thailand. Transactions Kansas Academy of Science, 70: 281-348.

Kundstadter, P. and Chapman, E. C., 1978: Problems of shifting agriculture and economic development in northern Thailand. In Kunstadter, P., Chapman, E. C., and Sabhasri, S. (eds.), Farmers in the Forest. University Press of Hawaii, Honolulu, pp. 3-23.

Maxwell, J. E 1988: The vegetation of Doi Sutep-Pui National Park, Chiang Mai Province, Thailand. Tigerpaper 15: 6-14.

Mirov, N. T., 1967: The Genus Pinus. The Ronald Press Co., New York. 602 pp.

Pandee, P. and Chapman, E.C., 1983: Recent changes in land use and land cover at Huai Thung Choa. Mountain Research and Development, 3(4): 346-352.

Santisuk, T., 1988: An account of the vegetation of Northern Thailand. In Schweinfurth, U. (ed.), Geoecological Research. Vol. 5. Franz Steiner Verlag Wiesbaden Gmbh., Stuttgart, 61 pp.

Smitinand, T., Sabhasri, S., and Kundstadter, P., 1978: The environment of Northern Thailand. In Kunstadter, P., Chap- man, E. C., and Sabhasri, S. (eds.), Farmers in the Forest. University Press of Hawaii, Honolulu, pp. 25-40.

Stokes, M. A. and Smiley, T. L., 1968: An Introduction to Tree-ning Dating. University of Chicago Press, Chicago. 73 pp.

Urban, D. L., O'Neill, R. V., and Shugart, H. H., 1987: Land- scape ecology. Bioscience, 37: 119-127.

Werner, W. L., 1993: Pinus in Thailand. Franz Steiner Verlag, Stuttgart. 286 pp.

Whitmore, T. C., 1984: Tropical Rain Forests of the Far East. Clarendon Press, Oxford. 282 pp.



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