Forest Resource

Overview
Cambodia is extensively forested, with almost 60 percent forest cover. Forest areas are almost evenly split between broadleaved evergreen forests and deciduous forests, with smaller areas of flooded forest around Tonle Sap Lake, and small areas of coastal mangroves. Forests in the west are mainly evergreen and the North-East is largely covered by deciduous forests. The southern and central parts of the country have less forest cover and face a shortage of wood, in particular for fuelwood. It is likely that logging has had its major impact along the international borders of Cambodia and in the coastal province of the Koh Kong. Illegal logging and cross-border log smuggling are significant problems for Cambodia. More than 20 percent of Cambodia´s land area is under some form of legal conservation protection.

Forest Types

Geographic Description
The Kingdom of Cambodia is located in south-east Asia between latitude 10° to 15° north and longitude 102° to 108° east. It covers a surface area of 181 035 km2. It is bordered on the north-east by Laos, on the east and south-east by Vietnam, on the south-west by the Gulf of Thailand, and on the west and north-west by Thailand. In the rough form of a rectangle, it is about 500 km long by 400 km wide.

The country has a large alluvial central plain, surrounded by mountains and plateaus except in the south-east and along part of the coast. Only a few points exceed 1 000 m in elevation. They are located primarily in the extreme north-east in the Cardamom Mountains and Elephant Mountain.

The highest point is Phnom Kchual (1 843 m). The area between 500 and 1 000 m constitutes only about 5 percent of the territory. The Mekong River crosses the country north to south and connects with a depression occupied by large lakes, the Tônlé Sap (Great Lake), the level and surface area of which varies (from 2 600 to 10 400 km2 in size) due to flooding during the rainy season.

The climate is typically tropical and subject to monsoons. The temperature at Phnom Penh averages about 29° C throughout the year. The dry season is defined by the number of months having less than 50 mm of rain. Phnom Penh gets around 1 000 to 1 500 mm of precipitation with 4 or 8 months of dry season. On the other hand, the coast on the gulf of Thailand is very wet, 3 000 to 4 000 mm of precipitation annually, with a short dry season of 1 to 2 months, while the area to the east of the Mekong, with 2 000 mm of precipitation and more, has a dry season of 4 to 5 months.

Resources Forest cover Vegetation

Natural Woody Vegetation Description

Introduction
Three main types of forest are found in Cambodia: relatively open deciduous forest; generally closed semi-deciduous forest; and evergreen closed forest. The first covers a larger area than the others, the second is the richest in timber, while the third represents an eco-floristic type, unique in Southeast Asia. The following descriptions are based mainly on Rollet (1972) and Legris (1972).

Closed Forests
Broadleaved

Closed deciduous forests are mostly found on basaltic and rocky brown soils onslopes. Deciduous forests and open forests are mixed in the north, and north-east of the Cardamoms; north of the lakes; and east of theekong. Such stands generally cover small areas and have an almost completely deciduous cover dominated by a number of species, mainly Lagerstroemia spp., Xylia dolabriformis, and some scattered associated species (Sindora cochinchinensis, Adina cordifolia, Vitex spp., Anogeissus pierrei, Grewia paniculata, Terminalia nigrovenulosa, Cratoxylon formosum, Ceiba pentandra, Pterocarpus pedatus, Schleichera trijuga, Pterospermum grewiaefolium, Irvingia oliveri, Eugenia spp. and Careya sphaerica). The undergrowth may be close and continuous, made up mainly of bamboos, or scattered in thick patches. There are many transitional forms, some tending toward open forest and some toward closed forest. There is also considerable variation in the floristic composition, although the typical bamboo is always russey rhley.

Closed semi-deciduous forests are edaphic-climatic formations that have grown up on constantly moist soils in regions where the average annual rainfall is over 1 200 mm, and where the dry season lasts from 3 to 5 months. They vary considerably in appearance and floristic composition and encompass a wide range of types, often including a large proportion of Lagerstroemia spp. A discontinuous emergent layer between 40 and 50 m tall dominates a uniform main storey. The emergent layer often contains voluminous and sometimes large-crowned trees belonging to Ficus spp., Heritiera javanica, Dipterocarpus alatus, D. costatus, Shorea vulgaris, Anisoptera cochinchinensis, Tetrameles nudiflora, Amoora gigantea, and sometimes shorter trees of Sandoricum indicum, Toona ciliata and Dysoxylum spp. Some of these trees, like Heritiera javanica and Tetrameles nudiflora, have huge, smooth buttresses, and their 1.5-m diameter, cylindrical trunks going straight up for 15 or 20 m give these forests a majestic aspect. The unbroken layer, which represents the main forest cover, is less clear-cut. It is on the whole fairly strong, thick and between 20 and 30 m tall, and no woody family is clearly predominant. At most, we can say that evergreen Guttiferae are usually present in good numbers, as well as various species of Ficus with very spreading foliage. Other frequent species are Irvingia malayana, Sindora cochinchinensis, Pterocarpus pedatus, Pahudia cochinchinensis, Diospyros spp., Adina cordifolia, Eugenia spp., etc. The undergrowth is usually not dense, but is rich in species belonging mainly to the Rubiaceae, Araliaceae, Annonaceae (Polyalthia spp., Xylopia spp., etc.) and Euphorbiaceae (Baccaurea spp., Cleistanthus spp.) families, while Graminaceae are rare. On the other hand, multi-stemmed palms (Licuala spinosa) may be common. In forest breaks and margins, large numbers of lianas (Calamus spp.) and many woody creepers, some of them voluminous (Melodorum thorelii, Ancistrocladus extensus), reach up to the highest foliage of the unbroken layer. Other much smaller, clinging creepers (Piper spp.) are confined to the undergrowth.

Closed semi-deciduous and deciduous forests are usually found side-by-side in patches. Comparison of their structure shows that they can only be transitory stages in the reconstitution of closed evergreen forest or localised edaphic-climatic formations.

 Forest Industry

Lowland (< 700 m) closed moist evergreen forest covers the southern face of the Elephant Range, the periphery of Kompong Som Bay, and Kas Rong and Kas Kong islands, and stretches north into Thailand. It almost reaches the sea at many points along the rocky coast. The soils are generally shallow and acid, and hence poor. The upper layer of this fully-grown evergreen forest is very irregular, sometimes being unbroken with the crowns of the trees more or less touching, and sometimes very open, and reaches an average height of 30 m. The higher branches are thickly leaved but relatively short, from 6 to 10 m. The trees have a classic habit, with long, straight, almost cylindrical trunks, without any branches to a height of at least 15 m. However, their diameter is often quite small (15 to 40 cm). Palaquium obovatum, with its great winged buttresses, is common among the emergent species. Dipterocarpaceae generally dominate in the highest layer, with five species almost always present: Shorea hypochra, Anisoptera costata, A. glabra, Dipterocarpus costatus and Hopea odorata. Parkia streptocarpa, Heritiera javanica, Swintonia pierrei and Syzygium cinereum are usually found in the upper cover. It is difficult to know whether one or two main storeys – between 10 and 20 m – should be counted above the undergrowth. The cover is not, however, particularly dense, so that light reaches right down to the ground. This in large part explains the great abundance of palms (Caryota urens and Oncosperma tigillarium), climbing shrubs (Spatholobus parviflorus, Entada phaseoloides, Urania rufa, Piper spp., etc.), and lianas (Calamus sp. and Daemonorops spp.), acaulous or not, both large and small. Hopea pierrei, Vatica odorata, Diospyros spp., Callophylum spp., Garcinia delpyana, Euphoria cinerea, Guioa squamosa, Nephelium spp., Pterospermum grewiaefolium and various Sterculia are common here. The Fagaceae family is present with the Lithocarpus and Castanopsis genera, as well as the Myrtaceae family (Syzygium zeylanicum, S. lineatum, and Tristania merguensis). There are also large numbers of aerial roots, raising the small trunks of Hopea pierrei, a common tree in the main storey, about 1 m off the ground. The undergrowth contains Euphorbiaceae (Antidesma cochinchinensis, A. ghaesembilla, Aporosa planchoniana, Croton spp.) and Myrsinaceae, together with the already listed palms and Pinanga duperreana, Areca triandra, Arenga pinnata, Licuala spinosa and Calamus spp. In the normal forest, the herbaceous vegetation is poor, while the epiphytic layer is rich.

The closed evergreen forest is literally riddled with patches of dwarf closed forest in ill-drained depressions. Conifers are present here in the main layer to a significant degree, and there are also often more palms in this layer. Such forest is, on average, no more than 12 m tall. Some evergreen-forest Dipterocarpaceae subsist here and there, particularly Hopea odorata and H. pierrei, accompanied by Syzygium zeylanicum, Tristania merguensis and various Garcinia, although such trees are only medium or small in size. They are mixed with Dacrydium pierrei and Podocarpus neriifolius, which are very common in some places. The main layers seem similar to those in the evergreen forest. Palms are the largest group, both numerically and in the number of species, which are the same as those listed in the previous paragraph. The herbaceous vegetation is sparse. Every possible transitional stage between dwarf forest and the surrounding evergreen forest is also found.

Medium-altitude (> 700 m) closed forest is found in the hilly country around the Gulf of Thailand and on the hills east of the Mekong. Fairly low winter temperatures, violent summer winds, often shallow and chemically poor soils, and a lack of sufficient sunlight due to frequent fog, mean that its growth is stunted and very irregular and its structure much simplified. The dominant layer, which can reach a height of 20 m, is rich in Fagaceae: Lithocarpus cambodiensis, L. guinieri, L. farinulenta, L. harmandii, Quercus cambodiensis, Castanopsis cambodiana, etc. Various Cinnamomum, Litsaea, Syzygium and Tristania species are locally frequent, as well as Hopea pierrei, Cedrela toona and Canarium spp., the last-named solely in the forests east of the Mekong. All the trunks are relatively short, buttresses are small or absent, and main and secondary branches are fairly distorted. Crowns with a hemispherical habit are sometimes frequent. There is an almost total absence of any Dipterocarpaceae. The undergrowth in these forests is very thick, closed in general by a tangle of Euphorbiaceae and Rubiaceae stems and shoots and mixed with a large number of tree and other ferns such as Cyathea spp., Oleandra spp., Cibotium barometz and, particularly east of the Mekong, Gnetum gnemon, palms (Pinanga cochinchinensis, Arenga pinnata) and Pandanus spp. The epiphytic layer is well developed in these moist forests.

Inland, periodically flooded forest is found mainly around the large lakes and in some depressions along the Mekong, although only scrubwood is usually left due to over-logging. The only areas still covered by proper forests of this type, – and even these are fairly limited in size, – are the lower reaches of the Stung Sen and Stung Sangkhé and the Tonlé Chhma region. The major phenomenon affecting the existence of such forests is the annual flooding, which lasts for about 6 months, from August to January or February. These formations have a very simple structure. In the best examples, they are low forests – about 15 m tall – ranging from partially closed to almost open, and made up of small-diameter (very seldom over 50 cm) trees. In a few places, they form clusters, with almost touching crowns, although there are always gaps. The most common trees are Cynometra spp., Mitragyna spp., Barringtonia acutangula, B. micrantha, Coccoceras anisopodum, Hydnocarpus anthelminthica, Albizia lebekkoides, Elaeocarpus madopetalus and E. griffithii. The floristic composition is complex and difficult to record with any precision, since selective logging and clearing have seriously affected the distribution of species and led to various secondary formations, often invaded by non-original species. Under the whole complex there may be a very close 3- to 4-m high thicket that is submerged at high water and is made up mostly of Coccoceras and Hymenocardia species with diameters between 3 and 10 cm. There are neither aerial roots nor pneumatophores, and no creepers, except along the rivers. The natural regeneration of the larger species is weak. An absence of palms is also to be noted. Today this periodically flooded forest is of considerable economic interest for natural fish farming.

Mangroves are only found around Veal Renh and Kompong Som Bays and north of Kas Kong up to the border with Thailand, and only in residual form as narrow, broken strips that may, however, continue fairly far up the water courses. The main species are Rhizophora conjugata, R. mucronata, Bruguiera gymnorhiza, B. sexangula, Ceriops tagal, C. decandra, Sonneratia alba, Lumnitzera littorea, L. racemosa and Carapa obovata. Phoenix paludosa, an elegant, short-stemmed (3 to 8 m) palm, gives the formation its typical aspect, and is often found in clumps. The trees average between 10 and 15 m tall, while the shrubs, which are much more numerous, are between 5 and 10 m. When the land rises fairly sharply so that it is very often above the flood water, the mangroves degenerate into a thicket, generally of Rhizophora conjugata between 2 and 3 m tall and with a thick tangle of aerial roots, and in certain places also Bruguiera gymnorhiza. There is no herbaceous layer, and the soil is blackish, very moist and criss-crossed by a mesh of fine roots. Mangroves continue to provide firewood and wood charcoal, but in smaller quantities than in the past.

Stands of Melaleuca leucadendron