Microbial Necromass Controls Niches of P Acquisition​ Under Warming by Enlarging Rhizosphere Hotspots and Shortening Hot Moments

Necromass derived from microbial turnover is a potential source of energy and nutrients to compromise the competition between microorganisms and plant in the rhizosphere. However, the role of necromass for microbial processes within the rhizosphere lacks a deep understanding of mechanisms and thus the interplay of root traits, soil temperature and necromass cannot be yet described thoroughly. Therefore, by using two root traits of maize (mutant rth3 with defective root hair prolongation and the corresponding wild type) at 20oC and 30 oC in phosphorus (P) deficient soil we tested if: i) necromass amendment provides additional labile organic matter to stimulate microbial-synthesized enzymes and hence expand rhizosphere hotspots and effeting P acquisition niches; ii) necromass addition stimulates rhizosphere microbial activities of hairless-mutant maize more than wild type regardless of temperature. Coupling in situ zymography and destructive sampling and subsequent analysis of microbial activities and plant biomass, revealed that the presence of necromass raises hotspot percentage in rhizosphere by three to fourfold at 20oC while this increment was three times lower at 30 oC. Shorter turnover time of substrate at 30 oC compared to 20oC in necromass treated soil evidently proves a faster decomposition stimulated by the concomitant warmerming and necromass-derived labile sources. Formation of fish-bone root structure beneficial from necromass addition could be a strategy of mutant maize to compensate the root hairs absence under warming resulting in outcompeting of rhizosphere microbiome for 33P uptake by plant. Decoupling alteration of Vmax and Km in necromass presence at 30oC showed that under warming stress microorganisms allocated their energy resources to synthesize more enzymes rather than increasing their efficiency. Overall, the intrinsic flexibility of plant-microbe interaction and necromass decomposition is a dynamic process that corresponds to the extent and duration of rhizosphere hotspots and mediates the adaptation of agro43 ecosystem to global warming.