Large‐scale rewetting and shading experiment reveals optimum conditions for tropical peat swamp forest restoration

Introduction Deforestation and fires have caused substantial loss of tropical peat swamp forests (PSF) in Southeast Asia. Substantial efforts have been undertaken to rewet and revegetate peatlands, but these restoration measures can lead to conflicting outcomes. Knowledge is needed on how to combine revegetation and rewetting approaches to effectively restore peatlands. Objectives Using a large‐scale field manipulation in Sumatra, Indonesia, on a former Acacia plantation on peat, the effects of water table depth (WTD) below the peat surface and shading conditions on planted tree species were tested. Methods WTD was manipulated through surface treatments by lowering the peat surface to differing depths (0, −0.25, and −0.50 m) and carried out shading manipulation across 72 plots with a complementary natural Acacia tree shading experiment in 12 plots. Individual tree survival and growth of 3124 seedlings from 16 species were monitored from 24 up to 36 months, alongside natural regeneration. Results Higher water tables with prolonged inundation inhibited seedling growth, survival, and natural regeneration. Full shade treatment with artificial netting increased seedling survival but reduced growth during the first 12 months. Similar effects were observed in the natural Acacia tree shading experiment. There were significant species differences in response to treatments and continuous WTD variation. Conclusions Our findings showcase that too much rewetting has the potential to negatively influence planted seedling growth and survival and highlight the importance of shading to ensure seedling survival. These insights provide a foundation for defining optimal WTD targets and species selection strategies for PSF restoration.