Increasing grazing intensity reduces arthropod diversity and overrides topography-driven community patterns in...

Topographic depressions in karst landscapes, called dolines, serve as important microrefugia for biodiversity. However, they may be strongly affected by various anthropogenic disturbances, including forest management, waste dumping, and livestock grazing. Although the effects of grazing on doline vegetation are well documented, far less is known about how grazing intensity influences arthropod communities within these landforms. To study the effects of grazing intensity on arthropods, we applied a multi-taxa approach including spiders (Araneae), true bugs (Hemiptera: Heteroptera), and ants (Hymenoptera: Formicidae) as bioindicators. We selected 18 doline bottoms and their adjacent plateaus in the Aggtelek Karst, Hungary, and sampled them over two consecutive years - with grazing present in one year and excluded in the other, the latter serving as a control. We used structural equation models (SEMs) to assess how habitat type (doline vs. plateau) - which reflects associated differences in microclimate and vegetation characteristics - together with grazing intensity influenced arthropod abundance and diversity. The SEMs showed that in the control year, habitat-related differences between dolines and plateaus were clearly reflected in the diversity patterns of all three arthropod groups, with higher species richness and abundance in dolines. Grazing partially overrode this pattern through both direct and indirect pathways, although the extent and underlying mechanisms differed among taxa. Our results demonstrate that habitat type, vegetation height, and grazing intensity interactively shape arthropod diversity in karst landscapes. Appropriately managed grazing may help maintain the arthropod biodiversity of these microrefugia and should therefore be considered in future conservation planning.