A Supplemental HCVF Assessment on the Sumatran Tiger ...

FINAL REPORT Tiger <strong>HCVF</strong> <strong>Supplemental</strong> <strong>Assessment</strong> – Serapung FMU
2.3 Ecology of Peat Swamp Forests around the FMU
The SmartWood <strong>HCVF</strong> report describes in detail the ecological characteristics and
associated flora and fauna of the major habitat types found in the Siak-Pelalawan
block. Five habitats are recognised in this landscape - tall PSF, mixed PSF, short PSF,
secondary habitats, and mangrove/coastal habitats. Only short PSF was found to be
absent from the FMU.
Coastal peat-swamp forest, where peat accumulates on top of marine sediments
(Reiley, Ahmad-Shah & Brady 1996), is predominant within the FMU – presenting as
Tall PSF across the majority of the FMU area. The FMU PSF abuts tidal rivers and
coastline, providing an accumulation of freshwater in the peat soil which maintains
sufficient hydrostatic pressure to repel tidal saltwater incursions into the inland soil
profile.
Relatively little terrestrial wildlife research has been carried out within PSF ecotypes in
general, with most previous PSF wildlife studies limited to investigation of arboreal and
aquatic animal species. This lack of ecological context has presented a challenge to
the interpretation of results obtained during this assessment.
Despite this paucity of data regarding terrestrial animals, some inferences can be made
from general ecological studies within the PSF ecosystem. Low nutrient levels of soils
in mature PSF almost certainly limit primary production. In such a habitat plants are
expected to defend their leaves and other edible parts as fiercely as possible against
potential herbivores (Whitten et al. 2000). Consistent with low productivity ecosystems,
a number of studies have indicated that the density of primates is lower in PSF than in
dry lowland systems (Galdikas 1978, Marsh and Wilson 1981, Mackinnon 1983) which
decreases further still with increasing distance from rivers (MacKinnon et al. 1996).
Many species of mammals and birds inhabiting PSF are the same as those in other
lowland tropical rainforest (Medway 1977, Davies and Payne 1982; MacKinnon 1983;
Wells 1985) although, for at least terrestrial mammals, these are found to live at much
lower densities in PSF (Merton 1962, Janzen 1974). Extrapolated to the typical prey
species of the tiger, PSF would be expected to have a lower carrying capacity and
hence its habitat potential for tigers would be less optimal when compared to other
lowland forest ecotypes.
Other research has suggested that PSF has ecological attributes that increase its
conservation value. While PSF is generally considered to have a relatively low floristic
diversity (MacKinnon et al. 1996), recent studies have shown that tree diversity can be
comparable to, and sometimes even greater than, that of forests on mineral soils
(Hanum & Leprun 1999). PSF also provides a habitat for a number of endemic and rare
tree species (Ibrahim 1997).
Similarly, of the 57 mammal and 237 bird species recorded in PSF of peninsular
Malaysia, 51% and 27% respectively are listed as globally threatened species
(Sebastian 2002). In Sumatra, PSF constitutes the largest remaining area of low-level
forest habitat and, as such, now represents a vital refuge for not only peat swamp
specialists, but also a wider range of lowland specialist species (Sebastian 2002).
2.3.1 Habitat Modification of Peat Swamp Forest by Logging
The Siak-Pelalawan forest block represents a modified PSF ecosystem due to
logging activities. The entire forest block has, in the recent past, been managed
and exploited under HPH logging concessions (Figure 4). Inspection of satellite
imagery (Landsat 2001, 2002 and SPOT 2004) reveals logging rails have been
used widely across the forest block, and that severe degradation of forest is
associated with the more accessible areas.
Sumatran Tiger Conservation Program Pg 13/68