Nitrophilic aspect of epiphytic lichenobiota of white willow (Salix alba L.) in the Astrakhan Reserve

Abstract

Among the epiphytic lichens of the Astrakhan Reserve, nitrophilic, toxic tolerant species dominate. At the same time, the reserve is located far from industrial areas. According to the results of quantitative studies, nitrophilic species dominate in terms of species diversity, occurrence, and projective cover. It is suggested that the abundance of nitrophilous species among lichens is associated with the ornithological factor: numerous nests of great cormorants, gray herons and crows on white willow. Crown rainwater containing bird excretions has elevated concentrations of nitrogen compounds. To assess nitrophilicity and toxicophobia, an index of average toxicophobia is proposed, calculated on the basis of a 5-point scale of lichen sensitivity and the number of species. It is based on an assessment of the most widespread lichen species, which determine the general background of lichenological toxicophobia in the surveyed area. The higher the indicator (maximum TFav = 5), the cleaner the area. The Average Toxicophobicity Index of the Astrakhan Reserve, calculated on the basis of the list of species minus the “null” trees for the established test sites in the Damchiksky, Trekhizbinsky and Obzhorovsky areas and considered as a single data set, is TFav = 2,18, which is lower than the median value of TF = 2,5 for a 5 point scale. A more accurate calculation of the Average Toxiphobicity Index (TFav), calculated on the basis of individual trees as a single array, taking into account “null” trees, is 1,66 ± 0,08. For the Damchiksky section, TFav = 1,46±0,12; for the Obzhorovsky section TFav = 1.93±0,12. For the Trekhizbinsky section, TFav = 1,48±0,16. This indicates a significant nitrophilic component of the epiphytic lichen biota Salix alba L. in the Astrakhan Reserve and the influence of the ornithological factor on the formation of the lichen flora.