Plant and soil invertebrate diversity of a rare alkaline fen in Croatia
Authors: Ana Randić, Vedran Šegota, Jelena Bujan, Jana Bedek, Antun Alegro, Andreja Brigić
Authors and affiliation
Abstract
In Croatia, alkaline fens are rare and highly endangered ecosystems that rely on precipitation and mineral-rich ground water. They are characterized by extreme environmental conditions such as high soil moisture, low nutrients and oxygen availability. In this study we present plant (vascular plants and bryophytes) and soil invertebrate diversity (isopods, carabid beetles and ants), together with soil properties of the alkaline fen Dretulja River Valley, near the settlement Plaški, Croatia. Our objective was to discover whether plant and animal communities are specialized to this extreme habitat, the answer to which is of great value for biodiversity conservation. The unique fen conditions supported high plant diversity, including extremely rare and threatened plant species (e.g. the carnivores Pinguicula vulgaris, Drosera rotundifolia and Utricularia minor) and relic vegetation of dominantly Holarctic (e.g. Carex flava, C. lepidocarpa, C. rostrata, Parnassia palustris) and boreal elements (e.g. Scorpidium revolvens and S. scorpioides). Analysis of the Ellenberg-type indicator values of plant species demonstrates that the fen habitat is well-insolated, water-saturated, moderately alkaline and nutrient-poor. In contrast to plants, soil invertebrate diversity, particularly isopods and carabid beetles, was reduced due to the harsh environmental conditions. Only ants demonstrated any great capacity to tolerate extreme environmental stresses, although they were also low in abundance. Soil invertebrate communities were predominantly composed of hygrophilous to mesophilous species, typically associated with wetlands, meadows and open bogs. Notably, we recorded Asellus aquaticus, a freshwater isopod species, whose presence in the samples was likely due to being washed into traps during elevated water levels. Additionally, we recorded a tyrphophilous ant species Myrmica scabrinodis in the fen. Thus, the composition and structure of plant and invertebrate communities indicates that the fen’s hydrological conditions remained well-preserved and to preserve great fen biodiversity it is essential to maintain these hydrological conditions.
Keywords
peatlands, tyrphophilous species, Isopoda, Carabidae, Formicidae