Hyphobox Experiment Schwaebische Alb

The short-term allocation of fresh photosynthates to hyphosphere microbial communities is still poorly understood, particularly under natural field conditions. To address this, we constructed a field experiment with so-called hyphoboxes separating a rhizosphere, hyphosphere, and substrate compartment, with the hyphosphere and substrate compartments accessible only to microbes but not to roots using a 50-um mesh. The substrate compartment was partly amended with 15N-labeled or unlabeled urea and additionally separated by a 4-mm airgap. 36 Hyphoboxes were buried at a grassland plot located on the Schwaebische Alb for 3 months (April-July 2021), followed by a 13CO2 pulse labeling of the plant aboveground biomass allowing us to track the transport of recently plant-fixed C into the soil and into microbial phospho- and neutral lipid fatty acids (PLFAs, NLFAs) in different microhabitats (e.g., rhizosphere and hyphosphere). We further investigated the assembly of fungal and bacterial communities in eight of the 36 hyphoboxes to compare community assembly across compartments and measured the transfer of urea-derived 15N via hyphosphere microbes into plants after the 3 months.