Abstract
Tropical rainforests are the most diverse and productive ecosystems on Earth. These system account for two-thirds of global plant diversity, and are often referred to as hyperdiverse in terms of tree species richness. Typically, any random draw of 300 adult individuals will represent over 100 different species. Understanding the ecological processes underlying this diversity will be essential for predicting biodiversity consequences of global change factors currently challenging tropical rainforests such as increased intensity of drought and changing nutrient balances. Mycorrhizal fungi act as a major conduit of carbon into soil, and affect competition between trees through connecting them belowground. This plant-fungal interaction is one of the most abundant symbioses on earth and is tightly linked to plant nutrient limitation. Ecosystems are increasingly enriched with CO2 and nitrogen and subject to climate change, which could alter abundance and functional properties of mycorrhizas in yet unknown ways. This in turn could have large consequences for plant interactions.
Forests in French Guyana are unique in being among the most pristine and well-studied lowland tropical rain-forests on Earth. In this project we will use a variety of approaches to better understand the effect of drought and nutrients (Nitrogen and Phosphorus) on root colonizing microbes including mycorrhizal fungi, pathogens and bacteria. This will be done through combinations of small scale precipitation experiments and fertilization trials, as well as with a larger separate fertilization trial.
Also, we will test the effect of neighbouring seedlings on these microbial communities on seedling inventories that have been carried out for over 10 years to test for statistical between seedling success and effects on conspecific neighbours through mutualists and antagonists. In parallel the project proposes to conduct experiments to assess the effect of mycorrhizas on adult-seedling interactions, which may have a major influence on tree biodiversity.
Together, these experiments will greatly increase our understanding of the importance of this plant-fungal symbiosis for seedling performance. This knowledge will allow better prediction of the interdependence of soil fertility, plant-fungal relationships, and their combined effect on plant diversity and soil carbon levels.
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