Hill and montane forests occur at elevations of 1,000 meters above sea level, and can be found across almost all of Indonesia’s largest islands: Sumatra, Indonesian Borneo (Kalimantan), Java, Sulawesi, Nusa Tenggara, Maluku and Papua. In Borneo, highland forests grow mainly in the north and are dominated by dipterocarp tree species.
Highland forests contain a greater diversity of dipterocarp trees than other forest type. There are currently about 371 species recorded in Indonesia, and more than 50% of these can be found on the island of Borneo (LIPI, 2014).
The Unique of Dipterocarps of Borneo’s Highlands
Dipterocarpaceae is a family of tall trees that can grow up to 60 metres high, between altitudes of 0-1,000 metres above sea level. Meranti (Shorea spp.), keruing (Dipterocarpus spp.), and kamper (Drybalapnos spp.) are all examples of this family that are common to parts of Borneo’s highlands.
The towering height of dipterocarp trees give highland forests their unique character. Moreover, dipterocarps within a certain area will flower en-masse every 2-10 years (depending on various factors), followed by a mass fruiting season. This irregular cycle is known as masting, and paints the forest in brilliant colours for 3-4 months when the trees are in flower (Appanah, 1993).
See also: The Beauty of Masting
Barito Ulu: Pristine Forest Dominated by Dipterocarps
Barito Ulu is one of just a few pristine highland forests left in Borneo and, like many such forests, is dominated by dipterocarp species. Located at the rocky Heart of Borneo, along the majestic Barito River, Barito Ulu features mountains, cliffs, valleys and white-water rapids.
Many elements of local Dayak culture are closely connected to the forest and Barito River. Furthermore, due to the region’s remoteness, as well as the landscape’s unique geographical features, Barito Ulu is rich in biodiversity.
See also: Creeping on the Onerous Cliff
Research suggests that two species of gibbon coexist in Barito Ulu; namely, Bornean white-bearded gibbon (Hylobates alibibarbis) and Müller’s gibbon (Hylobates muelleri). There is even evidence of a hybrid population (H. alibibarbis x H. muelleri) in a zone between the Joloi, Busang and Murung rivers (Bodmer, 1997).
Recent camera trap data from the Centre for Conservation and Natural Resources of Central Kalimantan and the Borneo Nature Foundation indicates the presence of several charismatic and threatened species in Barito Ulu. Among them, the Endangered and rarely seen Borneo bay cat, and the striking great argus pheasant (Argusianus argus). The great argus, in particular, is highly regarded by many Dayak communities living along the Barito River.
Written by Desi Natalia, Communications Manager