Long-term effects of forest liming on soil invertebrates

Forests are highly sensitive to air pollution and affected by acidification. Compensatory liming of forests as a preventive soil protection measure has therefore been common practice throughout Europe for decades to counteract the negative effects of acidification. Liming increases the soil pH and promotes soil processes which in turn can affect soil organisms. As cross-taxon research on the long-term consequences of forest liming is scarce, we investigated the long-term (>30 years) effects of different liming treatments on the diversity and biomass of soil organisms in forests in south-western Germany. We found that the total biomass of soil overwintering and ground-dwelling arthropods was highest in the treatment with the highest liming intensity. Furthermore, the density of earthworms increased with increasing liming intensity. This was also reflected in the effects on the community structure of ground-dwelling arthropods. In contrast, the alpha diversity – expressed as the richness of operational taxonomic units based on next-generation sequencing DNA metabarcoding – was not affected by forest liming. Our results indicate that forest liming can have long-lasting effects on soil organisms and that high liming intensities (>9000 kg ha⁻¹) can increase the biomass and densities of soil arthropods and earthworms. The extent to which this influences soil ecosystem functions, as well as the effects of liming in regions with differing soil conditions, warrants further investigation.