Soil aggregation, ecosystem engineers and the C cycle

Patrick Lavelle (1) , Alister Spain (2) , Steven Fonte (3) , Jose Camilo Bedano (4) , Eric Blanchart (5) , Victor Galindo (6) , Michel Grimaldi (1) , Juan Jose Jimenez (7) , Elena Velasquez (8) , Anne Zangerlé (9)

1 iEES Paris - Institut d'écologie et des sciences de l'environnement de Paris
2 UWA - The University of Western Australia
3 CSU - Colorado State University [Fort Collins]
4 UNRC - National University of Río Cuarto = Universidad Nacional de Río Cuarto
5 UMR Eco&Sols - Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes
6 Univalle - Universidad del Valle [Cali]
7 IPE - CSIC - Instituto Pirenaico de Ecologìa = Pyrenean Institute of Ecology [Zaragoza]
8 UNAL - Universidad Nacional de Colombia [Bogotà]
9 Ministère de l'Agriculture, de la Viticulture et du Développement rural [Luxembourg]

Soil aggregation and its effects on soil C storage have been addressed in thousands of research articles over the last 40 years. Research has been mostly focused on the resistance of aggregates to mechanical disruption and the role of organic matter in aggregate stabilization. On the other hand, relatively little attention has been paid to identifying the microbial, plant root and macro-invertebrate actors and physical processes that continuously create and destroy aggregates. The sum and dynamics of these processes determines the ability of soils to store and conserve C. Understanding the interactions between aggregation dynamics and C transformations in soils therefore requires a precise identification of the agents that produce aggregates and knowledge of the rates of formation and persistence in the pools thus identified.We propose to separate macro-aggregated components of different, physicogenic and biogenic origins from non-macro-aggregated soil on a morphological basis, using a simple visual technique. The specific biological or physico-chemical agent which produced each individual macro-aggregate can then be determined using Near Infrared Spectroscopy (NIRS). A general description of the distribution and quality of organic matter among the different groups of macro-aggregates can be made. Simple soil re-aggregation or dis-aggregation tests conducted in field conditions further measure the production of different macro-aggregates with time and their mean residence times in the studied soil. Respirometry measurements on each recognized category of macro-aggregates evaluate the respective C losses through respiration. The methods described here will allow the dominant pathways of C flow at a given site to be characterized and possible management options to increase C storage identified. We finally discuss the different assumptions made to build this simple model and offer ways to test the methodology under field conditions.

Keywords: Soil aggregation; Soil organisms; C cycling

Domains: Environmental Sciences

Patrick Lavelle, Alister Spain, Steven Fonte, Jose Camilo Bedano, Eric Blanchart, et al.. Soil aggregation, ecosystem engineers and the C cycle. Acta Oecologica, 2020, 105, pp.103561 -. ⟨10.1016/j.actao.2020.103561⟩. ⟨hal-03490669⟩