Drainage effects on leaf traits of trees in tropical peat swamp forests in Central Kalimantan, Indonesia

Abstract

Large areas of the tropical peat swamp forests in Central Kalimantan were drained to be converted into rice fields and then abandoned. A change in the soil water level due to drainage in the forests must have had a big impact on the ecology and ecophysiology of the trees in the drained remnant forests. The leaf traits of these trees in particular may have been directly or indirectly affected by drainage because of their high sensitivity to environmental change. To understand the influence of drainage on leaf traits, we investigated leaf morphological and physiological differences between intact and drained peat swamp forests in Palangka Raya, Indonesia, using 14 species distributed over both types of forests. We compared the leaf mass per unit area (LMA), leaf toughness, leaf area- and mass-based nitrogen content (N_area and N_mass), carbon/nitrogen ratio, total phenolics, condensed tannin and lignin content and carbon isotope ratio (δ¹³C) of both types of forest trees. In the drained forest, trees had higher values in LMA, N_area, and δ¹³C than in the intact forest, suggesting that such trees adjust themselves to dry conditions to increase photosynthetic ability with high water use efficiency compared with those in intact forests. We also found an increase in condensed tannin content in drained forest trees, which may offset the drainage-induced acceleration of leaf decomposition to some extent.