Host-Associated Differences in Below-Canopy Temperature and Soil Moisture Beneath Healthy and Viscum album-Infected Silver Fir and Scots Pine Trees

European mistletoe (Viscum album L.) is an expanding hemiparasitic plant in European forests, but its association with below-canopy hydrothermal conditions remains poorly understood. We compared near-ground air, surface, and upper-soil temperatures, volumetric soil moisture, and selected soil properties beneath healthy and naturally infected silver fir (Abies alba Mill.) and Scots pine (Pinus sylvestris L.) trees in south-eastern Poland. Continuous measurements were collected at 15-min intervals from April to August 2025 using TMS-4 loggers, while soil samples collected at 35 cm depth were analysed for texture, bulk density, organic matter, carbon, nitrogen, electrical conductivity, and selected nutrient-related properties. The observations showed contrasting patterns between the two host stands. In Abies alba, infected-tree microsites were descriptively warmer, with approximately 1 °C higher near-ground air and surface temperatures and up to approximately 2 °C higher upper-soil temperature than healthy-tree microsites. Temperature–soil-moisture relationships were also weaker beneath infected fir trees (maximum reported R2 approximately 0.09) than beneath healthy trees (up to approximately 0.39). Differences were smaller in Pinus sylvestris. However, because infection was naturally occurring, the host stands may differ in canopy structure, soil conditions, tree characteristics, and other environmental factors. In addition, the available manuscript does not report the number of independent TMS loggers/trees per treatment or the raw-data reanalysis required to account for repeated temporal observations. Therefore, the present results should be interpreted as host- and stand-associated patterns rather than causal effects of mistletoe infection. The study provides a basis for testing whether mistletoe-associated changes in canopy water partitioning and tree condition are linked to localized hydrothermal variation.