Promising native tree species for reforestation of degraded tropical peatlands

Tropical peat swamp forests (PSF) of South East Asia are biodiversity hotspots and carbon-rich ecosystems under severe degradation and threat of extinction. Almost yearly recurring fires progressively devastate clear-cut PSFs. The need for both conservation and active restoration together with the appropriate information on the techniques and species is urgent. The aim of this study was to find native PSF species that are suitable for reforestation in the open degraded peatlands. We established two planting experiments in degraded peat areas with 21 tree species to study the survival and growth in relation to environmental factors for 2 years. The study sites were located in Central Kalimantan, Indonesia in the degraded peatland of the Ex-Mega Rice area and along the degraded margins of the river Sabangau. Seed material collected from local forests was grown in a field nursery and planted 6-11 months later in the field. Growth and mortality of the seedlings and environmental variables (water table, temperature) were monitored frequently for two years. The effects of the environmental variables on growth were tested with mixed-effects models and on mortality with Cox regression. As a result, we could derive species-specific information of the seedlings' early stage ecology and suitability for restoration. The most promising species based on the analysis were Shorea balangeran, Adenanthera pavonina, Dacryodes rostrata and Lithocarpus dasystachys. The comparison of the two differing areas revealed contrasting challenges: the main obstacle for reforestation in the Ex-Mega Rice area was fire, whereas in the river margin extreme water table fluctuation limited the success of the seedlings.