Fig trees (Ficus spp., Moraceae) are common in Asia. Northern Thailand has perhaps 25 species, which includes shrubs, treelets, trees, and woody climbers/creepers. Several species are found on Doi Lohn and some of these are present along the Nature Trail.
Ficus auriculata (tree #10) and Ficus benjamina (tree #125) are good examples to discuss here. Ficus auriculata is a free-standing tree, while Ficus benjamina is a “strangler”. All fig species produce a unique flowering and fruiting structure that is botanically known as a synconium. This is a structure in which many tiny, unisexual flowers are enclosed inside a usually globose “fig” which has a tiny hole at the tip. Most fig species produce figs in enormous quantities, all of which are relished by animals and even a few eaten by man.
Tiny wasps inside the figs are responsible for pollination. This is an intimate and specific relationship, a kind of obligate mutualism, where both parties are dependent on each other. This is another example showing that biodiversity is not only intricate, but also quite fragile; in this case loss of either the wasp or the fig results in the extinction of both.
Ficus auriculata has a single trunk, developing from ground level. It produces figs on short, stout branches from the trunk and main branches. This is called cauliflory (flowers from the trunk) and ramiflory (from branches) – uncommon situations in this region. There are also a few unrelated trees on Doi Lohn with this feature.
Ficus benjamina is what has been called a “strangling” tree. Birds eating figs of “stranglers” disperse seeds on the branches of canopy trees. These seeds germinate as epiphytes (growing on another plant) and grow adventitious (aerial) roots downwards which tend to clasp and eventually envelop the support (not host) tree. These adventitious roots eventually reach the ground and then the fig is able to grow much faster. In time, the fig crown becomes larger than that of the support tree – which eventually dies. Most likely a combination of the age of the support tree with shading and root competition, perhaps also the weight of the fig tree, cause the demise of the support tree. Some of these “stranglers” become enormous and develop adventitious prop roots over a metre in basal diameter.
In nature, “strangling” figs do not develop on the ground, thus they are an obligate epiphyte and always require a support tree to develop. Forest destruction, therefore, prevents natural conditions where these fig trees can develop. Fortunately recent innovations by FORRU (a reforestation research team in the Biology Department, Chiang Mai University) have shown that some “stranglers” can germinate and grow in nursery conditions. Trees grown this way have been successfully planted in cleared areas demolished by hill-tribe agriculture.
The Pang Soong Nature Tail has many examples where one plant grows on another living plant. This includes many ferns and orchids as well as less obvious fungi, algae, lichens, and bryophytes (mosses and liverworts). Epiphytes can be autotrophic (able to absorb their own moisture and produce their own food) or parasitic (taking water and/or nutrients from the host (which is also technically a support plant). Parasites are less common, but also present on Doi Lohn. These include several species of mistletoe (Loranthaceae and Viscaceae), which provide birds with edible fruits. These plants are green, but have root systems that penetrate the host’s tissue (i.e. hemi/semi-parasitic). Other parasites, a few of which can be found on Doi Lohn, are obligate parasites lacking chlorophyll and some of them lacking leaves. A recent and increasingly pervasive, introduced parasitic pest includes several kinds of Cuscuta (Convolvulaceae) which invade open disturbed places with dense growths of yellowish, spaghetti-like, leafless stems which damage and eventually kill native vegetation. This is becoming an increasingly dangerous problem in Mai Lai Village.
Saprophytes are fungi and plants that are usually unable to make their own food, lack chlorophyll (i.e. green colour), and live on dead matter. Decomposers of organic matter are a vital aspect of forest dynamics. Many fungi, slime moulds, as well as a few rare and inconspicuous flowering herbs in the soil are present on the mountain. Some are partially saprophytic (a few orchids) and require special niches for survival. Some others require a saprophytic or mycrorhizal association for germination and adult growth.
Bamboos are members of the grass family (Gramineae, Bambusoideae) and include several genera and c. 25 species in northern Thailand. Contrary to popular belief, most Thai species flower and fruit regularly each year and do not die after fruiting. Many Chinese species flower and fruit only once in their lives and then the entire plant dies (monocarpic). Many Thai species are partly monocarpic in that the individual culm (stem) flowers and fruits only once and then dies, but the rest of the plant remains alive. Bamboos in some lowland fire-prone areas are deciduous during the hot-dry season, but all species found above 1000 m elevation are evergreen. Lowland deciduous, teak-dominated, forested areas also include many bamboos as a natural component. These are called deciduous, seasonal, hardwood + bamboo forests (bb/df) and have been largely destroyed during the past century. Deciduous dipterocarp-oak forests (dof) do not have much bamboo and the species that occur in this habitat differ from those species found in bb/df.
The Mae Lai Valley has several different species of bamboo, all of which provide edible “shoots” (very immature culms) and many different kinds of construction and handicraft materials. Bamboo products are numerous and include house frames, cut floors, woven walls, various kinds of baskets, irrigation pipes, tobacco pipes, shingles etc.
The largest species in the valley, in fact throughout the region, is Dendrocalamus giganteus (Wall.) Munro, (Tree walk #55), in which the culms grow to over 20 m tall, with a basal diameter of 15-20 cm. The culm sheaths of this species are also used to make hats and in former times were used to write on. Dendrocalamus membranaceus Munro and Bambusa pallida Munro are somewhat smaller species, but are commonly used for many purposes. Dinochloa maclellandii (Munro) Kurz has a sprawling habit, that is the culms of 2-3 cm diameter are not erect and appear to have become bent because of a collapsed upper part. This species is monocarpic. Many individuals and even entire communities of this species flowered synchronously in late 1994 and produced fruits in early 1995 when most culms were leafless. Large areas where this species grew were barren throughout 1995, but were slowly recolonised by viable seeds. These areas regrew rapidly and within a few years appeared as they did before flowering. Another monocarpic event is imminent for this species.
In general, bamboos grow in disturbed, often open, and sometimes in regenerating hardwood-forested areas. The four species noted above are commonly found in disturbed, often periodically burned areas. Some areas of the Mae Lai valley are dominated by bamboo since the dense, fibrous root system of these plants can inhibit or even prevent the growth of seedling trees and woody climbers. Bamboos are excellent for soil erosion control and soil nutrient conservation. Bamboos are easily cultivated by planting pieces of their rhizomes. An alternative way is to cut the culms horizontally in halves and partially burying the outside in soil where roots will develop from the nodes and new culms opposite and above them.
click here for a list of trees in Pang Soong