Abstract

Development of agriculture and economic sector has become a subject to the current deforestation of tropical wetland region. The aim of the present study was to investigate the effect of deforestation on secondary tropical peat swamp forest (TPSF) by comparing macro-nutrients and others selected peat soil chemical properties of secondary TPSF and deforested secondary TPSF site. Peat soil samples were collected from two different plots at Batang Igan, Sibu, Sarawak, Malaysia. The plots were secondary TPSF where this area has been logged, but has not been cleared, while the other plot was clearing area where the forest has been cleared for agriculture. Sixteen soil samples were taken in each plot at a depth of 0 to 15 cm. All samples were taken randomly using peat auger. The samples were air dried and ground to pass through a 2 mm sieve. Soil pH was determined in water and potassium chloride (KCl) at ratio 1:2.5 using a pH meter. The loss on ignition method was used to determine soil organic matter and total carbon. Soil cation-exchange capacity(CEC) was determined by the leaching method. Total nitrogen was determined by the Kjeldahl method.  The total phosphorus (TP) and total potassium (TK) were extracted by the aqua regia method followed by the blue method to determine TP, and TK was measured using atomic absorption spectrophotometer. pH_water, soil CEC, soil organic matter, total C, total P, total K and C/N ratio were significantly higher in secondary TPSF when compared with deforested secondary TPSF, while the pH_KCl and C/P ratio content was statistically higher for deforested secondary TPSF. Deforestation of secondary TPSF significantly decreased soil pH_water, CEC, SOM, total C, total N, total P, total K and C/N ratio, but significantly increased soil pH_KCl and C/P ratio.

Key words: Peat swamp forest, soil acidity, soil organic matter, total carbon, total nitrogen, total phosphorus, total potassium, C/N and C/P ratio.