Influence of disturbances and environmental changes on albedo in tropical peat ecosystems

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Tropical peat swamp forests have been experiencing drastic disturbances, such as deforestation, drainage, and fire. We examined how such disturbances influence albedo, which regulates radiative energy exchange between the terrestrial surface and the atmosphere. We conducted continuous field observations at three sites: undrained forest (UF), drained forest (DF), and drained burned ex-forest (DB), in Central Kalimantan, Indonesia, for over 13 years.Observed albedo was strongly influenced by haze caused by fire because the haze layer covering the canopy has a relatively high reflectance. Under severe haze conditions in October 2015, apparent albedo increased to 0.156, 0.162, and 0.183 at the UF, DF, and DB sites respectively. Mean monthly albedos excluding fire periods were 0.094 ± 0.005, 0.092 ± 0.006, and 0.099 ± 0.017 (mean ± 1 standard deviation) at the UF, DF, and DB sites respectively. Seasonal fluctuation in albedo at the DB site, where ferns were dominant, was greater than at the UF and DF sites.Albedo at the DF site was significantly lower than that at the UF site from February to August (p < 0.05). At the forest sites the albedo increased as groundwater level decreased. Albedo was higher under high vapor pressure deficit at all sites. At the DB site albedo decreased when the soil surface was water-saturated and patched with puddles, potentially due to the low albedo of open water. The albedo at the DB site was lower than that at the forest sites at the beginning of the observation period. Subsequently, the albedo increased and exceeded those at the UF and DF sites immediately after fire damage in 2009. This could be explained by the expansion of bright-colored ferns and sedges over dark-colored peat soil. According to our results, haze, groundwater level, and vegetation cover significantly influence albedo in tropical peat swamp forests.