Coming to Common Ground: The Challenges of Applying Ecological Theory Developed Aboveground to Rhizosphere Interactions

Oren Shelef,Philip G Hahn,Zoe Getman-Pickering,Ainhoa Martinez Medina

doi:10.3389/fevo.2019.00058

Abstract

Accumulating evidence supports the importance of belowground interactions for plant performance, ecosystem functioning, and conservation biology. However, studying species interactions belowground has unique challenges relative to the aboveground realm. The structure of the media and spatial scale are among the key aspects that seem to strongly influence belowground interactions. As a consequence, our understanding of species interactions belowground is limited, at least compared to what is known about interactions aboveground. Here we address the general question: Do the ecological concepts that have been developed largely in aboveground systems apply to understanding species interactions in the rhizosphere? We first explore to what extent ecological concepts related to species interactions are considered in rhizosphere studies across various subdisciplines. Next, we explore differences and similarities above- and belowground for fundamental concepts in ecology, choosing topics that are underrepresented in rhizosphere studies but represent a swath of concepts: species diversity, island biogeography, self-organization and ecosystem engineering, trophic cascades, and chemical communication. Finally, we highlight to overcome major challenges of current methodologies to study rhizosphere interactions in order to advance the understanding of belowground interactions in an ecological context. By synthesizing literature related to rhizosphere interactions, we reveal similarities, as well as key differences, in how fundamental ecological concepts are used and tested in above- and belowground studies. Closing the knowledge gaps identified in our synthesis will promote a deeper understanding of the differences above- and belowground and ultimately lead to integration of these concepts.

Highlights

There has been a recent surge in studying species interactions that occur in the rhizospheres of plants (Brussaard, 1997; Hooper et al, 2000; Wardle et al, 2004; Orgiazzi et al, 2016)
We address the general question whether ecological concepts that have been developed largely in aboveground systems apply to understanding species interactions in rhizospheres
To examine how widely ecological concepts related to studying species interactions in general ecology vs. sub-discipline journals, we focus on recent usage of ecological concepts in the literature by searching for articles published in the last two decades

Summary

INTRODUCTION

There has been a recent surge in studying species interactions that occur in the rhizospheres of plants (Brussaard, 1997; Hooper et al, 2000; Wardle et al, 2004; Orgiazzi et al, 2016). Reconciling these differences in key ecological processes is critical to developing predictive theory and understanding responses to environmental changes (Wardle et al, 2004; Sutherland et al, 2013) In this perspective, we address the general question whether ecological concepts that have been developed largely in aboveground systems apply to understanding species interactions in rhizospheres. Current theory and data are far from being able to provide a meaningful estimate to a fairly simple and fundamental question in ecological theory It highlights the gap of knowledge we still have in relation to belowground arthropod interactions as compared to microbes (Heinen et al, 2018). While the role of plant exudates has received significant attention (e.g., Steinkellner et al, 2007; Toussaint et al, 2012), the extent to which chemical communication in the soil affect interactions and dynamics of networks remains largely unknown

RESEARCH METHODOLOGY OF RHIZOSPHERE INTERACTION

Findings

CONCLUDING REMARKS