Institute of Environmental Biology, University of Utrecht, 3584 CG Utrecht, THE NEDERLANDS.
In tropical lowland forests trees and fungi are strongly linked, through ectomycorrhiza (EcM) formation. In Sumatra, such forests are dominated by trees of the Dipterocarpaceae family. However, as part of the rapid deforestation and forest transformation, mixed dipterocarp forests have been replaced by other vegetation and land use types. Considerable areas of the lowland tropical forest in Sumatra have been turned into Rubber Agroforests (RAF). RAF is a land use type in which rubber trees are planted, while allowing the spontaneous establishment of forest tree species.
The method presented in this thesis includes four main elements. Firstly, vegetation analysis in seven types of land use. Secondly, study in nursery using dipterocarps species as bait plant to assess the effect of land use change on EcM inoculum and to analyze effect of soil heating and drying on EcM propagule. Thirdly, in-situ experiment in RAF with different history was done to assess whether fungal inoculant increased the survival, growth, nutrient uptake and EcM formation on Shorea selanica and Shorea lamellata. Finally, molecular techniques of PCR and sequencing have been applied to identify EcM fungal symbiont on dipterocarps. The study has been conducted in Jambi province, Sumatra, Indonesia. Ex-situ experiment has been conducted in the nursery of Forest Research and Development Agency, Bogor, Indonesia. Identification of EcM fungi was done in Fungal Biodiversity Centre (CBS), Utrecht, the Netherlands.
The result on vegetation analysis showed human activity in RAF management has strong effects on species richness. Very few trees dependent on EcM fungi were encountered in the RAF. Our study in the nursery shows the small differences in EcM colonization between soils derived from a wide range of land use types, may indicate that survival of spores and colonization potential are not sensitive to the history of the site. Rapid recolonization of the heated soil in the experiment may imply sufficient availability of EcM fungi for dipterocarps under field conditions, where fi re as a tool for land clearing is commonly used in Sumatra. In-situ experiment in the RAF showed that lack of trees that are dependent on EcM fungi in RAF and in non-forested land does not necessarily imply the absence of EcM inoculum belowground in the ecosystem. EcM inoculum persists in the soil after forest was changed to RAF.
Molecular identification of EcM fungi showed that Tomentella was the prevalent genus of EcM fungi colonizing dipterocarp seedlings in the nursery stage and in the in-situ test 1 year after the seedlings have been planted in the field. None of fungi was identified as Scleroderma columnare, which was inoculated to S. lamellata and S. selanica seedlings in the nursery stage. This indicated that indigenous EcM fungi dominated on the dipterocarp seedlings planted in the field, regardless of nursery inoculation.
The implementation of this study is potentially of great value for reforestation efforts with dipterocarps in RAF in collaboration with rubber farmers. This reforestation approach will ensure the successfulness of the reforestation managed sustainably by farmer, where they will benefit from them in the future.