Shorea balangeran and Dyera polyphylla (syn. Dyera lowii) as tropical peat swamp forest restoration transplant species: effects of mycorrhizae and level of disturbance

Abstract

Tropical peat swamp forests (TPSF) are being rapidly deforested, leading to disturbed hydrology, wildfires and carbon loss. Cost-effective methods are needed to increase the scale of restoration activities. One method is to inoculate seedlings with their corresponding mycorrhizae species, thereby increasing performance during nursery cultivation, although the benefits post-transplantation are less well understood. This study considered two TPSF tree species, Shorea balangeran and Dyera polyphylla (syn. Dyera lowii), and their mycorrhiza; Scleroderma columnare (S. balangeran) and Glomus clarum and Gigaspora decipiens (D. polyphylla). The performance of non-inoculated and inoculated seedlings was compared following transplantation into five forest zones, representing a gradient from intact to degraded TPSF. In the degraded area, both inoculated seedling species supported higher colonization levels compared to non-inoculated seedlings. Both tree species showed high survival rates in all forest zones, and survival, growth and biomass production were not affected by mycorrhizal treatment. Both species grew faster and accumulated greater biomass in the more degraded forest zones. Nitrogen and phosphorus content reduced for both tree species in the more degraded forest zones, however, inoculated D. polyphylla seedlings had higher nutrient content across all forest zones, as did S. balangeran though less uniformly. Both these tree species are therefore suitable for reforesting degraded TPSF and mycorrhizal inoculation is recommended given a) inoculated seedlings in the degraded area permitted a higher mycorrhizal colonization level, and b) mycorrhizae increased nutrient uptake in the transplanted seedlings, although in this short-term study survival or growth improvement in the inoculated seedlings was not apparent.