Exploration of the soil biota associated to Casuarinaceae trees from tropical ultramafic areas.

Pioneer plant species native to tropical ultramafic areas can be useful tools for the restoration of ultramafic soils degraded by nickel mining activities. Casuarinaceae trees are well known for its capacity to grow on nutrient-poor areas.

This is possible thanks to multiple adaptations, including the formation of actinorhizal symbioses with nitrogen-fixing Frankia actinobacteria.

Members of the genera Gymnostoma and Ceuthostoma (both from Casuarinaceae) colonise degraded ultramafic soils and promote the recovery of soil fertility.

However, they produce high amounts of slow-degrading litter which (among other effects) reduce the colonisation by other plant species.The project CASUABIOTA is intended to improve our knowledge of soil biota associated to Casuarinaceae from ultramafic areas of SE Asia.

The project has two main objectives: 1) to advance our knowledge about Casuarinaceae-associated frankiae and its tolerance to nickel, and 2) to obtain insights about the composition of Casuarinaceae litter and the organisms involved in its degradation, with a special interest in earthworms and saprophytic fungi.

To accomplish these objectives, a sampling campaign aimed at plants, litter, root nodules and earthworms will be performed in ultramafic areas from Sabah State (N of Borneo, Malaysia).

Collected material will be subjected to different analyses (litter composition, earthworm barcoding, soil fungal metabarcoding) and two manipulative experiments on litter degradation will be performed on vermireactors and on mesocosms.

Expected results include the identification of Ni tolerant Frankia strains, the assessment of litter effects on the composition of soil fungal and earthworm communities and the optimisation of a biological method to accelerate the degradation of Casuarinaceae litter.This knowledge will ease the use of Casuarinaceae for the restoration of tropical Ni-mine spoils.