BUKU ABSTRAK - Universiti Putra Malaysia

Comparison of Selected Chemical Properties of Peat Swamp Soil Before and After
Timber Harvesting in Sarawak
Dr. Seca Gandaseca
Muhamad Ismawi Salimin, Osumanu Haruna Ahmed and Nik Muhamad Ab. Majid
Faculty of Agriculture and Food Sciences, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8685 5473; secags@yahoo.com
Keywords: Peat swamp forest, chemical properties, timber harvesting, statistical analysis system
Effect of Precipitation Fluctuation on Soil Carbon Storage of a Tropical Peat
Swamp Forest in Sarawak
Dr. Seca Gandaseca
Anton Eko Satrio, Osumanu Haruna Ahmed and Nik Muhamad Ab. Majid
Faculty of Agriculture and Food Sciences, University Putra Malaysia,
43400 UPM Serdang, Selangor, Malaysia.
+603-8685 5473; secags@yahoo.com
Keywords: Peat swamp forest, rainfall, soil acidity, soil organic matter, soil carbon storage
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Forestry & Environment
The objective of this study was to compare the soil pH, cation exchange capacity, soil organic matter, total
carbon, total nitrogen, total phosphorus and exchangeable K of peat swamps soil, before and after harvesting
at Batang Igan forest in Sibu, Sarawak. This study compared selected chemical properties of a peat swamp soil
before and after timber harvesting. Peat soil samples were taken at 0-15 cm depth in 6 plots with 0.1 ha each
plot at Batang Igan forest at Sibu Sarawak, Malaysia. The soil samples were analyzed for selected soil chemical
properties. Data were analyzed by using Statistical Analysis System (SAS) version 9.2. The tropical peat swamp
forest indicated its specific natural state such as rich in soil pH KCl and except for C/N ratio, the selected chemical
properties such as soil pH water, cation exchange capacity, soil organic matter, total carbon, total nitrogen, total
phosphorus, and exchangeable potassium were significantly different between before and after timber harvesting.
Timber harvesting has significant effect on chemical properties of peat swamp.
The amount of rainfall varies markedly daily and annually in tropical region while temperature can be
constant. When the precipitation frequency is smaller, lowered water table occur and could increase substrate
availability for CO2 releasing decomposition processes. Therefore, rainfall may affect the soil carbon storage of
peat swamp forest. It was found different rainfall fluctuation on January and March 2008. Mean rainfall almost
doubled from 6.6 mm/day in January to 12.0 mm/day in March. Furthermore, rainfall in March was fluctuated
considerably than that in January. Thus, soil carbon storage under those extremely different rainfall conditions
was compared. Soil sampling was conducted in January and March 2008 on two different plots (0.3 hectare each
plot) to a depth of 15 cm. Mean rainfall on January was 6.6 mm/day while in March it was 12.0 mm/day. The
humic acid extraction was done and soil carbon storage values obtained by calculation. The calculation of soil
carbon storage was done by the bulk density method. Comparison between paired means of soil carbon storage
under the two different rainfall gradients were tested using paired t-test. Under higher rainfall, unstable carbon
tends to remain as stable carbon instead of CO2 evolution through decomposition. The high value of stable carbon
under higher rainfall suggests that this natural tropical peat swamp forest plays an important role as a sink rather
than a source of carbon. Inversely, this ecosystem has a role as a source of carbon under lower rainfall. It also
suggests that unstable carbon tends to decompose and releases CO2 by oxidation under lower rainfall. Anaerobic
environment is more prominent under higher rainfall and may facilitate high value of soil carbon storage (stable
carbon) in this peat swamp forest. Anaerobic environment (more additional water) plays an important role in
preserving soil carbon storage (stable carbon).