CaNiTropIs

Coupling of the canopy and the root system through carbon and nitrogen dynamics in tropical trees

Context

Significant carbon sinks of tropical forests are the balance between large photosynthetic uptake rates of tree canopies and ecosystem respiration, releasing CO₂ back to the atmosphere. Tree roots contribute greatly to this respiratory flux, but the extent of total root respiration and its regulation by either the environment and/or allocation of photoassimilates from the tree canopy belowground are still largely unknown. This knowledge gap is mainly a result of the inaccessibility of the complex root system of trees.

Aim

This project will:

1. investigate the mechanisms underlying the coupling between canopy and root system in tropical trees;
2. assess the impact of source strength (canopy) on sink activity (root system) and vice versa;
3. quantify the net tree carbon balance and belowground carbon allocation; and
4. identify the coupling of carbon and nitrogen cycles.

We will use a globally unique aeroponic system that can host trees with a 4m high shoot and >6m deep, fully accessible root system. Total shoot CO₂ and total root-system respiration fluxes of large tropical tree saplings will be measured simultaneously under various environmental conditions (manipulation experiments). In addition, dual labeling of trees with stable, non-radioactive carbon (via CO₂) and nitrogen (via mineral nitrogen) isotopes will be applied to address the coupling of carbon and nitrogen dynamics in tropical trees.

Download See some impressions of plant movements in the climate chambers here. (AVI, 17.1 MB)