Microbial diversity drives Priming effect along climate gradients of the Madagascar Highlands. CAMMiSolE_Grad_Clim_Mada

Priming effect (PE) has been proposed to be generated by two distinct mechanisms: the “stoichiometry theory” and/or the “nutrient mining theory”. Each mechanism is believed to get its own dynamics, to involve its own microbial actors and to target different soil organic matter (SOM) pools. The present study, located in the Malagasy Highlands, aims to evaluate how climatic parameters drive the intensity of each PE generation mechanism via the modification of their microbial and edaphic determinants. Soils were sampled along climatic gradients, designed to discriminate the annual temperature from rainfall effect, and characterized by biotic and abiotic descriptors. Potential organic matter mineralization and PE were followed over a 42 days incubation period. Bacterial and fungal phylogenetic taxa present in soil samples were assigned to functional guilds designed from their correlation to measured basal respiration, wheat- straw mineralization and PE. Results showed that PE was more driven by the size of the functional guilds associated to its generation, than by any edaphic descriptors directly. And Mean annual temperature controlled the balance between both chanisms via the quantity and quality of SOM, determining the size of the associated functional guilds.