Development of best practices for rehabilitation after mining – plants and their associated mycorrhizas and implications for soil regeneration
An interdisciplinary restoration ecology project focusing on understanding the cophylogenetic patterns of vascular plants and their mutualistic ectomycorrhizal fungi in Malagasy littoral forest
Malagasy littoral forest (left), and past (middle) and current (right) distributions of littoral forest. (Photo: Sven Buerki)
The Malagasy littoral forest is a specific type of forest. Only 10% of this distinct habitat now remains in small fragments, the overwhelming majority of which is not within protected areas. Over the last two decades, a botanical survey of the remaining littoral forests has showed that, littoral forests cover less than 1% of the total vegetation of Madagascar, yet comprises 1,535 species of plants, representing more than 10% of the total Malagasy flora, with ca. 25% of these endemic to this biome. Thus, the restoration of this fragile and threatened habitat is crucial for the survival of several species of plants.
Primary to a successful rehabilitation programme is soil restoration, of which mycorrhizas are one of the most important biotic components due to their close interactions with plants. Ectomycorrhiza (EM) is a special type of root-fungal association functionally different from the type found on >80% of all land plants. A recent study has demonstrated, for the first time, the occurrence of EM in the Malagasy endemic familes Asteropeiaceae and Sarcolaenaceae. The EM associated to members of these families in particular, as well as many other plants species in Madagascar, are potentially formed by a specific set of fungal taxa that are likely to be endemic to Madagascar and possibly even to littoral forest.
At present, nothing is known regarding the genetic diversity, gene flow, or correlated spatial genealogies of Malagasy littoral forest plants and their associated fungal mutualists; characteristics of species that are critical to restoration activities. Despite their fundamental importance to tree health and seedling establishment, and growing evidence that below-ground processes play a fundamental role in determining the structure of plant communities, there has never been a study of the distribution of root-mutualistic fungi in Malagasy littoral forest. Understanding these basic processes, i.e. appropriate levels and distributions of genetic diversity for adequate gene flow within populations and the coevolutionary dynamics of the plant-fungus mutualism, are essential for soil re-establishment. The results from this study will greatly enhance the ability to successfully restore littoral forest communities in Madagascar, which, given the dominance of EM vascular plants in this habitat, can be considered ectomycorrhizal communities.
In this study we propose to target plant taxa that are representative of all dominant angiosperm tropical trees that form EM associations (13 species have been identified to date). Such a situation is rarely found elsewhere in the tropics and it represents one of the major advantages of working in the littoral forest near Fort-Dauphin. In addition, the range of EM plant taxa found at this location goes from pioneer (e.g. Uapaca littoralis) to dominant trees (e.g. Asteropeia micaster). Although all the targeted taxa are endemic to Madagascar (with the only exception of Intsia bijuga), the investigated taxa are phylogenetically closely related to other major EM plants families found in tropical regions. For instance, it was shown that the Malagasy endemic family Sarcolaenaceae is sister to Dipterocarpaceae, which dominates Asian tropical ecosystems (with more than 470 spp.) and is of high value for ecological restoration. Based on this evidence, the present study will provide useful insights for the conservation and ecological conservation of the Malagasy littoral forest and also provide protocols that can be easily applied to other tropical regions.