Dataset from HIE Growth Chamber experiment: 13C labelled seedlings

Dataset for article: Improved phosphorus status supress soil organic matter decomposition in low phosphorus soil
Johanna Pihlblad1,2, Louise Rütting3, Laura Castañeda-Gómez1,4, Catriona A. Macdonald1, David S. Ellsworth1, Yolima Carrillo1
1 Hawkesbury Institute of environment, Western Sydney University, Penrith Australia
2 Lancaster Environment Centre, Lancaster University, Bailrigg, United Kingdom
3Chair of Soil and Plant Systems, Brandenburg Technological University Cottbus-Senftenberg, Cottbus, Germany
4 SouthPole Environmental Services, Zurich, Switzerland.
Elevated atmospheric CO2 (eCO2) affects soil carbon (C) dynamics by altering the balance between soil organic matter decomposition (SOM) and plant-derived C accumulation. Even minor changes in this balance can significantly impact future climate. Soil nutrient availability to decomposers, particularly nitrogen (N) and phosphorus (P), is crucial for both rates of SOM decomposition and plant-derived C accumulation, yet these processes are rarely assessed simultaneously. To investigate the interaction between eCO2 and nutrient availability on these soil C cycling processes we cultivated a tree (Eucalyptus grandis) and a grass species (Microlaena stipoides) in a controlled 13C-depleted atmosphere for 22 weeks. The altered δ13C signature of CO2 allowed separation of plant-C from SOM-C. N and P availability was manipulated by nutrient additions, while assessing multiple C pools, fluxes, and gross N processes. We found that plant-derived and SOM-derived C pools were decoupled in poor soils (a larger plant-C pool in soil does not affect the magnitude of the priming effect). The rhizosphere priming effect was suppressed when P limitation was alleviated, with a simultaneously increase of the N mineralization rate, leading us to conclude that microbes are mining for P in SOM and N in rhizodeposition products. The impact of CO2 was highly dependent on nutrient availability. Findings highlight that in this low P soil the processing of SOM-C and plant-C were not coupled and were more dependent on P availability than N availability. Further exploring these controls will be crucial for understanding ecosystem C, N and P cycling in future climates.