Productivity of sago palms on smallholder plantations after rewetting in previously drained peatland: a case study on Tebing Tinggi Island, Riau Province, Indonesia

Sustainable land use through rewetting is becoming increasingly important in drained peatlands. We assessed the recovery of productivity of smallholder paludiculture using sago palm (Metroxylon sagu) in a rewetted peatland on Tebing Tinggi Island, Riau Province, Indonesia, which had been drained and burned in 2014. Stand structure and productivity of sago palms in smallholder plantations were measured in December 2016, November 2017, and March 2020. The sago stands were divided into three stands structure groups (pre-harvest stands, mid- to post-harvest stands, and growing period stands) according to gaps in the harvesting cycle, which were distributed in a mosaic pattern. Only those sago palms that had reached their maximum size were harvested, and as a result the mosaic pattern varied over time (spatial variation). The estimated harvest trunk height after rewetting was 8.9 +/- 1.5 m (mean +/- SD), which was not significantly different from that before drainage (9.7 +/- 0.4 m). The average annual yield of sago was 26.8 trunks ha(-1), and there was large annual variation. Annual yield of paludiculture conducted after rewetting recovered to the same yield as that before drainage (26.0 trunks ha(-1)). Such size distribution patterns and large fluctuations in yield are characteristic of semi-traditional smallholder sago cultivation. Despite fluctuations in annual yield, harvesting only suitable individuals allows sago palms to be supplied every year. The findings obtained in this study will contribute to national and regional efforts to initiate paludiculture using sago palms.