Hot or not? connecting rhizosphere hotspots to total soil respiration

Abstract Aims Soil organic carbon (C) efflux is tightly linked to the rhizosphere, where soil microorganisms rapidly decompose compounds released from roots. Recently, imaging approaches have greatly improved our understanding of small-scale C-turnover heterogeneity and promoted term ‘rhizosphere hotspots’ for highly active areas. However, despite often assumed, effect these hotspots on total C balances still unknown. We aim bridge this gap by correlating rhizosphere data respiration individual plant scale. Methods grew 17 maize ( Zea mays L. ) plants in rhizoboxes filled with sandy arable soil. After four weeks, were labelled 14 CO 2 root exudation was visualized quantified C-imaging one day after labeling. The evolved trapped NaOH as well before labelling. Enzyme activity (β-glucosidase) zymography. Results Bulk β-glucosidase activitiy negatively correlated efflux, most important predictor (R = 0.55). Total specific C-activity solely (r 0.51, r 0.58). A combination bulk activity, rhizosphere- biomass, explained about 75% variance efflux. Conclusions This indicates that enzyme-activity are suitable predictors respiration, particularly when combined biomass account three-dimensional variation, scale directly larger balances.