In dryland ecosystems, typically characterized by sparse vegetation and nutrient scarcity, pioneer plants exert a critical role in the build-up of soil carbon (C). Continuous root-derived C inputs, including rhizodeposition and structural root litter, create hotspots of increased microbial activity and nutrient availability where biogeochemical processes, such as soil aggregation and the accumulation and stabilization of organic matter (OM), are promoted. Our study aims to disentangle the effects of root C inputs on soil aggregate formation, microbial community structures, and on the fate of OM -both before and after plant death, i.e., during the transition from rhizosphere to detritusphere. This was realized in a two-phase incubation approach, tracing the natural and undisturbed transition from growth to subsequent decomposition of a pioneer plant-root system ( Helenium aromaticum ) in a semi-arid topsoil and subsoil. We quantified water-stable aggregates, investigated the fate and composition of OM separated into particulate and mineral-associated OM fractions (POM and MAOM), and observed successional changes in the root-associated microbiome. Our results underscore the significance of roots as vectors for macroaggregation within the rhizosphere in both topsoil and subsoil, associated with a particularly strong increase in fungal abundance in the subsoil. In topsoil, we identified root legacy effects in the detritusphere, as root-induced macroaggregation persisted after plant death, a phenomenon not observed in subsoil. These root legacy effects were accompanied by a clear succession towards gram + bacteria, which appeared to outcompete fungi during root decomposition. The increased availability of decaying litter surfaces further facilitated the protection of particulate OM via the occlusion into aggregates. Overall, to gain a holistic understanding of plant-microbe-soil interactions, we emphasize the need for more studies that span over the full temporal dimension from living to dying plants in intact soil systems. C1 [Witzgall, K.; Steiner, F. A.; Teixeira, P. P. C.; Mueller, C. W.] Tech Univ Munich, TUM Sch Life Sci, Soil Sci, Freising Weihenstephan, Germany. [Hesse, B. D.] Tech Univ Munich, TUM Sch Life Sci, Land Surface Atmosphere Interact AG Ecophysiol Pla, Freising Weihenstephan, Germany. [Hesse, B. D.] Univ Nat Resources & Life Sci, Inst Bot, Dept Integrat Biol & Biodivers Res, Vienna, Austria. [Seitz, S.; Scholten, T.] Univ Tubingen, Dept Geosci Soil Sci & Geomorphol, Tubingen, Germany. [Rodriguez, V.] GFZ German Res Ctr Geosci, Sect Geomicrobiol, Potsdam, Germany. [Wagner, D.] Univ Potsdam, Inst Geosci, Potsdam, Germany. [Li, M.] Czech Acad Sci, Inst Soil Biol & SoWa Res Infrastruct, Biol Ctr, Ceske Budejovice, Czech Republic. [Li, M.] Univ Atacama, Ctr Reg Invest & Desarrollo Sustentable Atacama CR, Copiapo, Chile. [Seguel, O.] Univ Chile, Fac Ciencias Agronom, Santiago, Chile. [Buegger, F.] Helmholtz Zentrum Munchen GmbH, German Res Ctr Environm Hlth, Res Unit Environm Simulat, Neuherberg, Germany. [Angst, G.] German Ctr Integrat Biodivers Res Halle Jena Leipz, Leipzig, Germany. [Angst, G.] Univ Leipzig, Inst Biol, Leipzig, Germany. [Mueller, C. W.] Tech Univ Berlin, Inst Ecol, Chair Soil Sci, Berlin, Germany. [Mueller, C. W.] Univ Copenhagen, Dept Geosci & Nat Resource Management, Copenhagen, Denmark. C3 Technical University of Munich; Technical University of Munich; BOKU University; Eberhard Karls University of Tubingen; Helmholtz Association; Helmholtz-Center Potsdam GFZ German Research Center for Geosciences; University of Potsdam; Czech Academy of Sciences; Biology Centre of the Czech Academy of Sciences; Universidad de Atacama; Universidad de Chile; Helmholtz Association; Helmholtz-Center Munich - German Research Center for Environmental Health; German Research Foundation (DFG); German Centre for Integrative Biodiversity Research (iDiv); Leipzig University; Technical University of Berlin; University of Copenhagen