Earlier this year, Plant-Soil-Ecosystems hosted a session dedicated to Plant-Soil feedbacks at the 5th International Ecosummit, Montpellier France.The session was chaired by Paul Kardol from SLU (Swedish University of Agricultural Sciences) and Pierre Mariotte from EPFL (Swiss Federal Institute of Technology in Lausanne) and took place on Wednesday 31st September 2016 at Le Corum Centre in Montpellier. The speakers and the titles of the presentations are listed in the session-programme, each talk has a unique code, e.g [S05.29], using which, more info on the speakers can easily be found. Unfortunately, abstracts are not available publicly.
Plant-soil feedbacks (PSF) is the term used to describe the processes by which plants modify soil biotic and abiotic properties, which in turn feedback positively or negatively on subsequent plant communities. They are integral to the understanding of plant community dynamics and species invasion. In agricultural systems, PSFs can be drivers of soil nutrient depletion or the build up of soil pathogens leading to yield loss.
In the past 30 years, research in this field has grown immensely, yet is still a relatively young field with many unanswered questions. In the light of climate change and the growing concern for food security, PSFs have been receiving more attention. The objective of the session was to give an overview of the current state of knowledge in PSFs from leading experts in the field and to provide an excellent opportunity to bring together natural and agricultural research. In this article, I will summarise the content of the session and highlight some of the most significant results.
Opening the session was established ecologist Prof. Marcel van der Heijden [S05.29] from Agroscope (Switzerland) presenting work on one of the most fundamental concepts in PSFs – the influence of soil biodiversity. One key result from van der Heijden’s work concluded that decreasing soil microbial diversity negatively affects plant growth. Thus, kicking off the morning with a simple, profound message – above-ground dynamics are irrefutably dependent on the below-ground!
Continuing on the theme of “The Fundamentals” in PSFs were two talks dedicated to the identification of the underlying forces that drive feedbacks. In a 6 year field study, Andrew Kulmatiski [205.31] utilised PSF predictions and experimental data to identify the key soil organisms which promote or impede growth of target plant species. In the second, Zia Mehrabi [205.32] reported that resource economic traits, namely nutrient conservative versus exploitative species, are key drivers of feedbacks (based on results of a meta-analysis of 95 plant species).
By exploring the consequences of using different crop varieties, the concept of nutrient conservative versus exploitative species was visited again in two talks bridging the agricultural side of PSFs. Gerlinde De Deyn [205.30] tested the hypothesis that fast-growing species promote a build up of soil pathogens by comparing traits of human-selected, fast-growing crop species against their semi-natural relatives. Similarly, Amélie Cantarel [205.34] showed that the use of different wheat varieties can influence the above and belowground traits, daringly concluding that the inclusion of lower yield varieties in crop systems could promote positive PSFs. On a slightly different note, the importance of PSFs in agriculture was stressed by Martijn Bezemer’s [205.33] talk demonstrating that disease suppression in greenhouse grown flowers is possible by recreating PSFs found in nature in controlled greenhouse environments.
Moving on, the session shifted its attention to the role of climate change in the outcome of PSFs. This topic was explored through the phenomenon of soil legacy effects via historical drought by Barbara Drigo [S05.35], Nicolas Legay,[S05.36], Aurore Kaisermann [S05.38] and one particularly clever field/lab experiment by Gemma Rutten [205.37] on PSFs in Mediterranean Oak forests across a precipitation gradient. The results were mixed; plants and soil microbial communities can show resistance to drought [S05.36], whereas other results suggest soil microbial communities can be degraded [S05.35]. Building on this theme, the final talk of the session by Tanvir Shahzad [205.40] highlighted the potential for deep root plants species to facilitate microbes in the co-mineralisation of deep, millennia old, inert carbon with labile carbon. Thus, claiming that as plants are forced to exploit deep soils due to changing land use and climate change, they pose a real risk of further adding to the high levels of CO2 emissions.
To summarise, the session covered the key areas of focus in PSFs from fundamental driving forces, through the manipulation of these interactions in agricultural settings and finally to the affects of climate change. The session was superbly organised and was well received by a full attentive audience. Plant-Soil-Ecosystems was very proud to host this session at such a prestigious event and would like to thank all involved for sharing their expertise, spreading the word and extending the network of people devoted to bridging the above and the belowground sciences!
If you would like to hear more, you can find interviews from Marcel van der Heijden and Gerlinde De Deyn made by Pierre Mariotte from the Ecosummit on the Journal of Ecology blog page by following the links.