Effects of land use conversion on selected physico-chemical properties of peat in the Leyte Sab-a Basin Peatland, Philippines

Tropical peatlands are unique wetland ecosystems which provide various ecosystem services such as carbon storage and nutrient cycling. However, they have been substantially altered and transformed by land use conversion. The present study investigated the effects of land use conversion on the physico-chemical properties of peat in the Leyte Sab-a Basin Peatland, a tropical peatland on Leyte Island, Philippines. Peat core samples (1 m long) were collected from peat swamp forest, grassland and cultivation areas. Samples were analysed for gravimetric water content, volumetric water content, dry bulk density, porosity, pH, organic matter, total nitrogen and total phosphorus. Notably, conversion of peat swamp forest to other land uses (grassland and cultivation) has resulted in changes in peat physical properties such as reduced water content and porosity, and increased bulk density. A reduction in peat water content can be a direct consequence of peatland drainage while an increase in peat bulk density with reduced porosity reflects compaction owing to the passage of agricultural equipment and peat decomposition. Land use conversion altered chemical properties characterised by reduced organic matter and nutrients (total nitrogen and total phosphorus) in grassland or cultivation, indicating peat decomposition and mineralisation. In addition, decrease in peat water content due to drainage and increase in bulk density can be accompanied by losses of organic matter and nutrients. Finally, changes in peat physico-chemical properties as a consequence of land use conversion serve as important indicators of peat soil degradation.