Red Wood Ants prefer mature Pine Forests in Variscan Granite Environments (Formica rufa-group)

Abstract

0AbstractWe used presence/absence data of 5,160 red wood ant nests (RWA; Formica polyctena) acquired in a systematic large-scale area-wide survey in two study areas (≈350 ha) in the Oberpfalz, NE Bavaria, Germany to explore for the first time the influence of variable (e.g., forest type, tree age) and quasi-invariant factors (e.g., tectonics, geochemical composition of the bedrock) on nest size, spatial distribution and nest density for Variscan granites. A combination of the forest type (mature pine-dominated forests (≥80–140 years) as main variable factor and the geochemical property of the Variscan granites with their high natural Radon potential and moderate heat production as main quasi-invariant factor could explain the high nest numbers in both study areas. In addition, the spatially clustered distribution patterns of the observed nests suggest a strong interaction between nests and their quasi-invariant environment, especially the directionality of the present-day stress field and the direction of the tectonically formed “Erbendorfer Line”. In general, such a combination of variable and quasi-invariant factors can be addressed as particularly favorable RWA habitats.

Comparison of geogases in Cenozoic sedimentary environments

“…RWA nests were eight times more likely to be found within 60 m of known tectonic faults [12]. The results also showed that geogenic gases [13], rock formations with elevated Rn concentrations [14], fault-related CH4 emissions [15], volatile organo-halogens, alkanes and limonene [16] play key roles in the settlement of RWA nests. Physical phenomena such as tectonic stress variations in the subsurface, leading to highly mobile and oxidizing electronic charge carriers and formation of H2O2 that flow to the surface [17,18] may contribute to the survival of the colony.…”

“…Currently, Meinweg can be considered "no ants land" as no RWA nests have been observed so far. One reason could be that the concentrations of the soil gas anomalies were too low, for RWA especially prefer substrates with higher Rn concentrations [14] as observed at Meinweg. If the rifting process, the (re-)activation of faults and a higher concentrated degassing continue, RWA nests could be observed in this area in the future.…”