Nitric oxide (NO), a reactive nitrogen species, as a signaling compound in plant and microbial cells, and therefore an important mediator of plant-soil-microbe interactions and soil biogeochemical cycles. However, the role of NO, perticularly its connection to microbial processes and plant-microbe interactions, remains poorly quantified and understood as previous research focused on pure cultures and molecular analysis, but not an actual processes in complex soil systems. This thesis addresses gaps by investigating soil NO sources, the effect of cell-exogenous soil air NO on C and N biogeochemistry in plant-tree mesocosms, and the influence of external plant-derived NO on soil biogeochemical processes through an integrated approach combining meta-analysis, controlled mesocosm experiments, and greenhouse studies.
