Ecoregional Assessment of Biological Diversity in East Kalimantan

East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems
complete conversion of a primary forest to Imperata grassland can take place rapidly
after clearfelling and repeated burning (Kartawinata 1993).
Seedling establishment from the post-fire seed dispersal in the Wain River forest in 1997
was extensive, but it will take a long time before seedlings of primary species will have
established in numbers comparable to the post-fire density of resprouts. For that reason
the presence and performance of resprouts is a more important factor in the initial
restoration of the forest than is the density of tree seed sources. However, seed
production by trees that survive either as individuals in the burned area, or in pockets of
unburned forest, will ultimately be the main source of regeneration of many primary
forest tree species.
Slik et al. (2002) rather surprisingly found that species diversity of Macaranga trees was
higher after a year in burnt areas than was the case in selectively logged areas! After 5-
15 years, the number of trees per-surface-area recovered to predisturbance values in both
burned and selectively logged forest. There was a difference though, in the recovery of
number of tree species (biodiversity). In the case of burned forests, they have to be built
up largely from the seed rain and seed bank, whereas in selectively logged forests, a
large sapling and pole stand persists. However, much of the predisturbance tree species
diversity can be found in burned forest 15 years after a single fire. Slik et al. (2002) state
that “this renders them (Lowland Rainforest) still valuable for conservation, especially
since the studied forests were all heavily burned and tree species diversity is likely to be
higher in lightly burned forest”
• Spread of Alang alang (Imperata cylindrica).
Recently in East Kalimantan, Alang-alang grasslands have extended widely into
Lowland Rainforest areas. Alang-alang is a fire disclimax community, which prevents
natural rehabilitation of disturbed forest. It mainly results from conversion of forests to
plantations on infertile soils and not from slash and burn (swidden) agriculture widely
practiced by traditional people (Kiyono and Hastaniah 2000). The lack of regulations to
prevent clearing for one-crop rotation, after which land is permanently abandoned, is a
major factor in the spread of Alang-alang grassland and the permanent conversion of
Lowland Rainforests.
• Swidden agriculture.
MacKinnon et al. (1996) regard traditional swidden farming as causing little damage to
the environment. Fallow land from swidden farming usually becomes secondary forest
and ultimately develops into mixed dipterocarp forest after a fallow period longer than
70 years, if the seeds of primary forest species are provided (Okimori and Matius 2000).
However, new technologies, increased population pressures, and the need for traditional
farmers to plant cash crops have dramatically altered traditional swidden practices and
telescoped the fallow period (Jessup and Vayda 1988). There is a need to identify areas
of Lowland Rainforest where traditional swidden practices can be maintained and to
discourage other farming techniques that are inimical to maintenance of forest structure
and floristics.
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