Abstract
Soil-borne micro-organisms are the greatest source of biodiversity on Earth, and plants drive the dynamics of soil-borne microbial communinities via the quality and quantity of carbon source inputs into the system. Fot rerestrial ecosystems, it is expected that global climate changes will affect plants most directly, and thes changes include elevated temperature, alterations in moisture (rainfall) and increased levels of greenhouse gasses, especially CO2. Changes in general microbial processes have been observed in response to plant-driven effects of elevated CO2 but so far most of out knowledge is limited to net process information. The effects of elevated CO2 on the diversity and composition of soil microbial communities, as wellas on criticalinteractions between functional groups, are still largely unknown (Jones et al 1998; Hu et al 1999). The simulation or repression of key microbial groups will govern the course of these interactions, potentially shifting the balance between beneficial and harmfull interactions with the plant. As the species diversity of soil micro-organisms for most ecosystem functions is very high, it is unlikely that moderate losses of soil microbial diversity will alter soil ecosystem functioning. Rather, shifts between key groups or species within the microbial community are considerd to be of much more relevance CO2 concentrations on shifts within the microbial community in soil, focussing on the balance between attackers (plant pathogens) and protectors (antagonists) in the root-zone (rhizosphere) of wild plants, as one of the processes vital to the functioning of terrestrial ecosystems. We aim to answer the following research questions; (i) what is the effect of enhaced CO2 concentrations on the composition of the fungal and bacterial community int he rhizosphere? (ii) do enhanced CO2 concentrations result in shifts in the population densities of pathogens and beneficials and what are the consequences of these shifts? We will detemine changes in the abundance of fungi and bacteria, as well as functional groups within thes microbial groups, with particular focus on plant pathogens and antagonists in the rhizosphere of two dominant plant species of dune ecosystems, Festuca rubra and Carexd arenaria, exposed to increased concentrations of atmosphere CO2. By tracking changes in, and consequences of, functional diversity in these rhizosphere habitats, we propose to address the consequences of global change for this vulnerable dune ecosystem as well as more generally for the development of natural vegetation.
Netherlands