# Soil‐Borne Pathogens Reflect Agricultural Land‐Use Legacies

## TL;DR

This study shows that historical agricultural land use has lasting effects on soil microbial communities, especially on plant pathogenic fungi, which can indicate past land use for up to 150 years.

## Contribution

The study identifies soil-borne plant pathogenic fungi as key indicators of historical arable land use legacies.

## Key findings

- Bacteria showed stronger legacy effects than fungi in response to historical land use.
- Soil-borne plant pathogenic fungi showed a legacy of arable land use that lasted about 150 years.
- Legacy effects decay over time, influenced by changes in plant and microbial communities.

## Abstract

Historical land‐use changes shape present‐day biodiversity through legacy effects, but the duration and mechanisms of these legacies are poorly understood. We used historical land‐use maps in two Swedish landscapes across three centuries to examine the persistent influence of historical land use on plant and soil microbial communities. Overall, bacteria showed stronger legacy effects than fungi, but effects varied across functional groups of plant‐associated and free‐living taxa. However, soil‐borne plant pathogenic fungi showed a persisting influence of arable land use which gradually disappeared after ~150 years, suggesting that land‐use legacies decay over time. This dilution could relate to changing plant communities but also to changes in microbial associations, as suggested by species co‐occurrence patterns over time. Our findings provide novel and crucial information on the duration of land‐use legacies and single out soil‐borne plant pathogens as key indicator groups of historical land use in present‐day ecosystems.

Legacy effects profoundly shape the distribution and diversity of terrestrial communities, but are difficult to grasp over longer timescales. Here, we use historical land‐use maps to study lingering legacies of historical land use on present‐day microbial communities. Our findings show that soil‐borne fungal pathogens are key groups to follow as indicators of historical arable land use.