title: Interacting microbe and litter quality controls on litter decomposition: a modeling analysis.
abstract: The decomposition of plant litter in soil is a dynamic process during which substrate chemistry and microbial controls interact. We more clearly quantify these controls with a revised version of the Guild-based Decomposition Model (GDM) in which we used a reverse Michaelis-Menten approach to simulate short-term (112 days) decomposition of roots from four genotypes of Zea mays that differed primarily in lignin chemistry. A co-metabolic relationship between the degradation of lignin and holocellulose (cellulose+hemicellulose) fractions of litter showed that the reduction in decay rate with increasing lignin concentration (LCI) was related to the level of arabinan substitutions in arabinoxylan chains (i.e., arabinan to xylan or A∶X ratio) and the extent to which hemicellulose chains are cross-linked with lignin in plant cell walls. This pattern was consistent between genotypes and during progressive decomposition within each genotype. Moreover, decay rates were controlled by these cross-linkages from the start of decomposition. We also discovered it necessary to divide the Van Soest soluble (labile) fraction of litter C into two pools: one that rapidly decomposed and a second that was more persistent. Simulated microbial production was consistent with recent studies suggesting that more rapidly decomposing materials can generate greater amounts of potentially recalcitrant microbial products despite the rapid loss of litter mass. Sensitivity analyses failed to identify any model parameter that consistently explained a large proportion of model variation, suggesting that feedback controls between litter quality and microbial activity in the reverse Michaelis-Menten approach resulted in stable model behavior. Model extrapolations to an independent set of data, derived from the decomposition of 12 different genotypes of maize roots, averaged within <3% of observed respiration rates and total CO2 efflux over 112 days.
authors.affiliation: Department of Environmental Sciences, University of Toledo, Toledo, Ohio, United States of America; INRA, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France; Université Reims-Champagne Ardenne, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France.
authors.forename: Daryl
authors.initials: D
authors.lastname: Moorhead
authors.affiliation: INRA, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France; Université Reims-Champagne Ardenne, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France.
authors.forename: Gwenaëlle
authors.initials: G
authors.lastname: Lashermes
authors.affiliation: INRA, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France; Université Reims-Champagne Ardenne, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France.
authors.forename: Sylvie
authors.initials: S
authors.lastname: Recous
authors.affiliation: INRA, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France; Université Reims-Champagne Ardenne, UMR614 Fractionnement des AgroRessources et Environnement, Reims, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Bertrand
mesh_terms: D018533:Biomass; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D005591:Chemical Fractionation; D003198:Computer Simulation; D017753:Ecosystem; D006868:Hydrolysis; D008031:Lignin / Q000378:metabolism; D056265:Microbial Interactions; D008962:Models, Theoretical; D018515:Plant Leaves / Q000737:chemistry*; D018517:Plant Roots / Q000502:physiology; D025341:Principal Component Analysis; D012995:Solubility; D003313:Zea mays / Q000502:physiology
chemical_list: C036909:lignocellulose; D002245:Carbon Dioxide; D002244:Carbon; D008031:Lignin