A framework for modelling soil structure dynamics induced by biological activity.

Katharina Meurer,Mats Larsbo,Thomas Keller,David Parsons,Paul Hallett,Harry Vereecken,Jennie Barron,Elisabet Lewan,Nicholas Jarvis,Dani Or,John Koestel,Claire Chenu,Anke M. Herrmann,Matthew Fielding,Nargish Parvin,Astrid Taylor,Elsa Coucheney

doi:10.1111/gcb.15289

Abstract

Soil degradation is a worsening global phenomenon driven by socio‐economic pressures, poor land management practices and climate change. A deterioration of soil structure at timescales ranging from seconds to centuries is implicated in most forms of soil degradation including the depletion of nutrients and organic matter, erosion and compaction. New soil–crop models that could account for soil structure dynamics at decadal to centennial timescales would provide insights into the relative importance of the various underlying physical (e.g. tillage, traffic compaction, swell/shrink and freeze/thaw) and biological (e.g. plant root growth, soil microbial and faunal activity) mechanisms, their impacts on soil hydrological processes and plant growth, as well as the relevant timescales of soil degradation and recovery. However, the development of such a model remains a challenge due to the enormous complexity of the interactions in the soil–plant system. In this paper, we focus on the impacts of biological processes on soil structure dynamics, especially the growth of plant roots and the activity of soil fauna and microorganisms. We first define what we mean by soil structure and then review current understanding of how these biological agents impact soil structure. We then develop a new framework for modelling soil structure dynamics, which is designed to be compatible with soil–crop models that operate at the soil profile scale and for long temporal scales (i.e. decades, centuries). We illustrate the modelling concept with a case study on the role of root growth and earthworm bioturbation in restoring the structure of a severely compacted soil.

Highlights

The physical arrangement of the soil pore space (‘soil structure’) profoundly influences life in soil and many important processes and the ecosystem services that soil can deliver (e.g. Bünemann et al, 2018; Dominati, Patterson, & Mackay, 2010; Keesstra et al, 2016; Powlson et al, 2011; Robinson, Lebron, & Vereecken, 2009)
Adverse changes in climate or the adoption of non-sustainable land management practices may degrade the structure of soil to such an extent that it becomes unsuitable for crop production (e.g. Food & Agriculture Organization of the United Nations [FAO/ITPS], 2015; Gregory et al, 2015; Intergovernmental Panel on Climate Change [IPCC], 2019; Intergovernmental SciencePolicy Platform on Biodiversity and Ecosystem Services [IPBES], 2018; Rickson et al, 2015; Smith et al, 2016)
In this paper, we focus on the impacts of biological processes and agents on the dynamics of soil structure, in particular, the growth of plant roots and the activity of soil-living organisms

Summary

Introduction

The physical arrangement of the soil pore space (‘soil structure’) profoundly influences life in soil (e.g. root growth and microbial activity) and many important processes (e.g. rates of water and air movement, solute leaching, carbon and nutrient cycling, water and nutrient uptake by crops) and the ecosystem services that soil can deliver (e.g. Bünemann et al, 2018; Dominati, Patterson, & Mackay, 2010; Keesstra et al, 2016; Powlson et al, 2011; Robinson, Lebron, & Vereecken, 2009).

Results

Conclusion