Rhizosphere processes & effects of herbivory
Tidal marshes are key ecosystems of estuarine shores in the temperate zone. Here, plant species zonation is the outcome of the interplay of estuarine gradients (salinity, flooding regime), the species’ stress tolerance and biotic interactions (competition, herbivory). Marshes have been increasingly recognized as long-term C sinks sequestering organic C at rates exceeding those of most other ecosystems. The ability of marshes to sequester C depends on the rates of organic matter (OM) input from both terrestrial and aquatic/marine sources and on microbial OM degradation.
Alongside effects of abiotic factors, microbial OM degradation is essentially controlled by plant-microbe interactions at the interface between roots and soil. These rhizosphere processes may play a central role in the marsh C balance, pore water geo-chemistry and C fluxes across marsh-water boundaries. Distinct marsh plants differentially alter rhizosphere processes through differences in root architecture, the amount of root oxygen loss (ROL) and the quality and quantity of rhizodeposits (root exudates, root border cells, mucilage and nutrients). Overall, plant-microbe interactions in the rhizosphere can either stimulate or suppress OM degradation.
Herbivory (by geese, small mammals, livestock) is known to exert a major control on plant community structure and also affects micro-food webs in soils of estuarine marshes. As microbial OM processing in estuarine marshes has shown to be largely driven by plant productivity, herbivory can be expected to largely alter C cycling in estuarine marshes including greenhouse gas (GHG) emissions.
Doctoral projects within RT A will address the following research questions:
- How do plant-microbe interactions in the rhizosphere control C turnover?
- How is herbivory affecting C cycling and GHG dynamics?
- How do plant-microbe interactions and herbivory affect C cycling on different scales?