Swidden pollen spectra are unique, having no modern analogues

Slash-and-burn cultivation (SABC), a widespread premodern agricultural practice, shaped vegetation across the temperate zone of Eurasia for millennia, yet the SABC-associated plant communities and their modern analogues remain poorly understood.

We compared 74 fossil pollen spectra from radiocarbon-dated swidden horizons with 223 modern surface soil spectra using non-metric multidimensional scaling and cluster analysis.

The results show that slash-and-burn cultivation creates a unique palynological assemblage in soil, distinguishable from forests, meadows, fallows, and ruderal habitats. This signature was most pronounced in sites from broad-leaved coniferous forest, where cryptogam diversity was highest.

Here, we report that pollen spectra from buried swidden soils across the Eastern European forest zone consistently form a distinct and cohesive cluster, lacking modern analogues. These spectra are characterized by high proportions of Betula, Tilia, Epilobium angustifolium , cereal pollen, and a diverse assemblage of spores ( Marchantia, Lycopodium, Pteridium ), reflecting a mosaic of post-cultivation successional stages.

Insect activity, particularly pollen-storing burrows of ground-nesting bees, may enhance the swidden signal through selective accumulation of fireweed entomophilous pollen.

Our results provide SABC reference pollen spectra for temperate mixed and deciduous forest zones and can be used as a tool for reconstructing the extinct suite of plant communities associated with swidden cultivation.