Ecoregional Assessment of Biological Diversity in East Kalimantan

East Kalimantan Ecoregional Assessment: Chapter 2 – Target Ecological Systems
• Fire
Fire is one of the major threats to Lowland rainforests and many other forests in East
Kalimantan. In 1997-1998 over 50,000 km 2 of East Kalimantan burned, and some
23,000 km 2 of natural forest concessions were affected- mostly in the lowlands. This is
nearly one-quarter (24%) of the area of all natural forest concessions in the province and
included 90% of the important Lowland Rainforest within Kutai National Park
(Hoffmann et al. 1999).
Nieuwstadt et al. (2002) and Slik et al. (2002) examined the aftermath of these fires in
East Kalimantan in the vicinity of the Wain River and from Mt. Beratus in the south to
several locations between Balikpapan and Samarinda. Mark van Niewstadt (pers. com.)
considers that these forests appear to have a greater recovery potential than expected,
mainly due to the resprouting capacity of small stems in the forest undergrowth, which
allows for the relatively rapid recovery of populations of shade-tolerant trees. On the
other hand, it is clear that repeated disturbances (such as logging in burned forest, or
repeated fire) do cause greater damage than one would expect, because the already
limited recovery capacity is seriously further reduced. In particular, Nieuwstadt et al.
(2002) suggests that if future fires and other key disturbances, largely related to salvage
felling of timber after fires, and further cycles of cutting of the forest, could be
contained, then there would be good prospects of these forests regenerating. This would
be particularly so if the exotic grass, known locally as Alang-alang (Imperata cylindrica)
could be prevented from invading.
Nieuwstadt et al. (2000) states that the recovery capacity of forest vegetation after fire
and other disturbances involves four main processes: tree survival; resprouting of
damaged trees; germination of seeds in the seed bank; and the seed rain from mature
surviving trees. Directly after the low intensity ground fire in the Wain River area, which
burned accidentally in March 1998 after several months of drought, observers noted that
survival of trees larger than 30cm dbh (diameter at breast height) was about 45%, with a
range from 20% to 95% among species. This compares well with survival 6 months after
fire in unlogged forest in Kutai National Park, East Kalimantan, which was about 25%
(Leighton and Wirawan 1986). Sprouting after fire is important for forest regeneration
and appears to play an important role in the persistence of many primary forest species
in East Kalimantan (Nieuwstadt et al. 2002, Leighton and Wirawan 1986).
Interestingly, Leighton and Wirawan also found that, while fires killed most of the seeds
lying dormant in the litter layer and in the upper 1.5 cm of the soil, seeds in deeper layers
of the soil were unaffected. Because of the high mortality and the high germination
incidence soon after the fire, the density of viable seeds remaining in the soil is greatly
reduced. Under these circumstances the local seed bank has little potential for further
regrowth. These areas, if further damaged, risk invasion by wind-dispersed species,
including Imperata cylindrica (Alang-alang grass), Pteridium caudatum (Bracken fern),
and Dinochloa sp. (Bamboo). It has previously been shown in East Kalimantan that
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