Soil organic matter (SOM) is quantitatively a minor component (by mass and volume) of most soils, yet it is responsible for facilitating or moderating many key soil ecosystem services that affect agricultural food security, biodiversity and environmental quality. Its constituents range in mean residence times from <1 min for some low molecular weight (LMW) compounds, through to >10000 years for charcoal-like materials. It is these somewhat enigmatic aspects of SOM that not only provoke such interest from the research community, but also drive the need for applied research that enables custodians of the landscape to effectively manage SOM in a way that limits its loss and maintains or enhances its stock and function.
This special issue of Soil Research arises from the 7th International Symposium on Soil Organic Matter, which was held in Adelaide, South Australia, 6-11 October 2019. The theme of the conference was 'Soil Organic Matter in a Stressed World', reflective of the many challenges facing SOM, particularly the effects of climate change and over-exploitation by agriculture, as well as the role that SOM can play in mitigating some of the adverse effects of a stressed world. This overarching theme allowed a broad swathe of sessions and keynote topics framed to address the grand challenges of understanding and better managing SOM in our changing environment. Many of the conference topics/ sessions are captured in the collection of papers published in this special issue.
The symposium itself opened and closed with perspectives of some of the traditional custodians of Australia and Aotearoa New Zealand. Following the traditional Welcome to Country from Kaurna (pronounced gar-na) elder Uncle Rodney O'Brien, Robert McGowan delivered an inspiring talk on the perspectives of indigenous Maori people of New Zealand on managing their soils, waters and lands. Of note was the philosophy the Maori apply to the management of Papatuanuku (Earth Mother), in so much as it is not management but more of a partnership approach (McGowan 2021). To close the conference, Kauma elder Mickey Kumatpi Marrutya O'Brien spoke powerfully about the >60 000 years of land management undertaken by Australia's traditional indigenous owners. This management was far more than hunter-gathering, and included active management of the landscape to encourage important species for food, including grains for the production of damper (Coles and Hunter 2010; Gammage 2012; Pascoe 2018). There is a wealth of information and wisdom held by First Nations people that complements 'western' science, and in some countries such as New Zealand, there are examples of this informing policy (McGowan 2021). Indeed, Te ao Maori--the Maori worldview--is explicitly considered in a recent transdisciplinary review of regenerative agriculture (RA) research in New Zealand (Grelet et al. 2021).
There is an acute need for SOM scientists to communicate with policymakers to inform policy development with robust scientific evidence and to dispel misconceptions. For compelling arguments to be made, transdisciplinary approaches that explicitly consider the social impacts of recommendations such as 'quatre pour mille' (4 per mille; United Nations/Framework Convention on Climate Change 2015) should be...