aeroponics; canopy and root systems; sink-source relationships; carbon and nitrogen cycling; tropical trees; stable isotopes
Mannerheim Neringa, Werner Roland A., Buchmann Nina (2019), Measurement precision and accuracy of high artificial enrichment 15 N and 13 C tracer samples, in Rapid Communications in Mass Spectrometry
, 33(13), 1153-1163.
Milcu Alexandru, Puga-Freitas Ruben, Ellison Aaron M., Blouin Manuel, Scheu Stefan, Freschet Grégoire T., Rose Laura, Barot Sebastien, Cesarz Simone, Eisenhauer Nico, Girin Thomas, Assandri Davide, Bonkowski Michael, Buchmann Nina, Butenschoen Olaf, Devidal Sebastien, Gleixner Gerd, Gessler Arthur, Gigon Agnès, Greiner Anna, Grignani Carlo, Hansart Amandine, Kayler Zachary, Lange Markus, et al. (2018), Genotypic variability enhances the reproducibility of an ecological study, in Nature Ecology & Evolution
, 2(2), 279-287.
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. 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. This research will provide the unique opportunity to better understand the underlying mechanisms of canopy-root coupling and the consequences for the carbon cycle in tropical trees. It will enable us to directly access and manipulate the root system and therefore address the role of the root system in the carbon and nitrogen cycle of trees in general and of tropical trees in particular. Such information is crucial for accurately predicting the coupled biogeochemical cycles in tropical forests as well as their feedbacks in regional and global biogeochemical models under scenarios of future climate change.