A Map and Reviews of Knowledge on Farming Practices Affecting Soil Organic Carbon.

Systematic reviews are a gold standard method for synthesizing documented scientific evidence. The method was first established in the field of medicine in the 1980s, and has since been adopted across a suite of other disciplines, including environmental management. Through a systematic approach, reviewers aim to maximize transparency, objectivity and comprehensiveness. Formal systematic reviews undertaken according to guidelines set out by international review coordinating bodies help to produce high quality, reliable reviews, and we will follow these guidelines in the production of this review.

The literature was searched for relevant articles. During the screening process, most of the 20 000 original articles were excluded, but still 735 of the studies fulfilled our selection criteria, for example temperate or boreal climate and long-term records (>10 years). Metadata were extracted from these studies and presented in a GIS-application that is freely accessible at www.eviem.se/en/projects/Soil-organic-carbon-stocks/ (Haddaway et al., 2015; Environmental Evidence 4:23). The long-term studies sites identified in this map provide a useful addition to existing databases of long-term experiments. Furthermore, the review highlights 127 relevant reviews and meta-analyses that have been conducted on the topic and a GIS that displays the identified studies in detail allows users to interact with the evidence base, accessing detailed information about studies of greatest interest.

Besides introducing the methodology and the map, we will also present results from our first meta-analysis on soil tillage effect on soil carbon that we presently are conducting using data from more than 300 studies recorded in the database (Haddaway et al., 2016; Environmental Evidence 5:1).