A systematic map of forest disturbance impacts on soil and litter fauna: knowledge gaps and a roadmap for future research

Philip Martin, Leticia Pérez-Izquierdo, Charlotte Biryol, Solene Brasseur, Qian Li, Inti Luna Aviles, Sebastiaan Luyssaert, Bertrand Geunet, Stefano Manzoni, Claire Menival, Catalin Petritan, Rebecca Spake, Mathieu Santonja, Jorge Curiel Yuste

Anthropogenic climate change is increasing the frequency and severity of natural disturbances such as fires, droughts, wind damage, and insect and pathogen outbreaks in forests. The impacts of these disturbances on aboveground biodiversity are relatively well known, but this is not true for belowground biodiversity, particularly soil fauna. While a number of syntheses exist summarising the impacts of these different disturbances, it is unclear which topics have been well or poorly studied, or what biases affect the literature. To fill this knowledge gap and provide a road map to guide future research, we undertook a systematic map with the aims of characterising the literature on the impacts of natural forest disturbances on soil and litter fauna. We found 307 primary studies of 24 taxonomic orders of soil and litter fauna from 48 different countries. Our results show that studies of fire impacts were vastly more common than studies of other disturbances, while there were very few studies on the impacts of insect pests and pathogens or the impacts of multiple combined disturbances. Most studies focussed on meso- and macrofauna such as springtails or beetles, with relatively few studies on microfauna such as nematodes. Biodiversity metrics often measured abundance or local diversity, with few studies examining more complex outcomes like food webs. There were clear geographic biases, with many studies conducted in Europe and North America, but few in Africa and South America, leaving gaps in our knowledge of impacts outside of Temperate and Mediterranean forests. Study design robustness was highly variable, but was typically low for studies of fire, windthrow, and pests and pathogens, while it was high for studies of precipitation change. Studies tended to be short, often lasting for less than 2 years. Reporting of the intensity of disturbances was common for studies of precipitation change but for other disturbances was relatively rare. Our results indicate that while much progress has been made in understanding the impacts of forest disturbances on soil and litter fauna, there is a need to study: (i) a wider range of disturbances and especially the effects of multiple disturbances, (ii) a wider range of taxonomic groups, (iii) field sites in boreal and tropical forests, especially in the wet tropics, and (iv) there is a pressing need for longer-term studies with more robust methodologies.