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Title: Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept

item CASTELLANO, MICHAEL - Iowa State University
item Mueller, Kevin
item Olk, Daniel - Dan
item SAWYER, JOHN - Iowa State University
item SIX, JOHAN - Swiss Federal Institute Of Technology Zurich

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2015
Publication Date: 8/1/2016
Citation: Castellano, M., Mueller, K.E., Olk, D.C., Sawyer, J., Six, J. 2016. Integrating plant litter quality, soil organic matter stablilization, and the carbon saturation concept. Global Change Biology. 21:3200-3209.

Interpretive Summary: The chemical composition of plant litter, such as dead leaves or crop residues, changes considerably from species to species and also varies according to land management and environmental change, with potential consequences for the formation and persistence of organic matter in soil. This manuscript attempts to advance the understanding and predictability of how the chemical composition of plant litter influences soil organic matter formation by linking two existing theories of soil organic matter formation that emphasize i) microbial processing of plant litter and ii) the capacity of soil minerals and aggregates to protect organic matter from further microbial processing. We show that the chemical composition of plant litter should only have an effect on soil organic matter storage when soil mineral surfaces and aggregates are not already maximized with respect to their potential to protect organic matter from microbial processing. We also predict that when mineral surfaces and aggregates do have the capacity to protect more organic matter, storage of soil organic matter will occur faster for plant litters that are more easily and efficiently processed by microbes (e.g. litter that has more nutrients and simple compounds such as sugars). Land managers can use the concepts and predictions in this manuscript to maximize formation and retention of soil organic matter in agricultural landscapes that often have to capacity to retain more organic matter (i.e. sequester more carbon).

Technical Abstract: Recent research suggests labile plant litters promote the stabilization of soil organic matter (SOM) in physico-chemically protected fractions with relatively slow turnover. However, the effect of litter quality on SOM stabilization is inconsistent. Labile, ‘high quality’ litters characterized by high N concentrations, low C/N ratios and low phenol concentrations are not consistently stabilized in SOM with greater efficiency than ‘low quality’ litters characterized by low N concentrations, high C/N ratios and high phenol concentrations. Here, we attempt to resolve these inconsistent results by developing a new concept model that links litter quality to the soil C saturation concept. Our model builds on the Microbial Efficiency-Matrix Stabilization framework (Cotrufo et al. 2013) by suggesting that both high and low quality litters contribute to SOM stabilization, but over different timeframes and under different soil C status