Holocene regression of the critically endangered species Cladium mariscus (L.) Pohl on Žitný ostrov Island (site Mad, Danubian plain Lowland)

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This study presents the palaeo-botanical record from the central part of Žitný Ostrov Island on the Danubian Lowland in Slovakia. The record spans almost the entire Holocene period and provides evidence that the wetland species Cladium mariscus (Cyperaceae) was present in this region as late as the Greenlandian period. In addition, the combination of C. mariscus and Carex elata beds were most likely an important part of the littoral zone vegetation during that period. Our investigations are based on plant macro-remain analysis, radiocarbon dating and physical sedimentary analysis of the former Danube side channel. The palaeo-channel infill active in the Late Pleistocene reflects complete hydroseral succession of a terrestrialised palaeo-lake. The earlier of two possible hiatuses in the fossil record was likely associated with a disturbance which caused Cladium mariscus to disappear from the local plant spectra. The most likely drivers of C. mariscus’ decline are a climate change of 8.6 cal ka BP associated with water fluctuations and the local habitat alteration to an eutrophic environment. These are discussed herein together with the isolated scattered populations surviving in the surrounding micro-region throughout the Meghalayan period. Finally, there are only two known remaining C. mariscus sites in the Žitný Ostrov Island area, and the key modern driving factor was the dramatic water regime changes in 19–20th Century caused by anthropogenic impact. These were caused by the construction of drainage canal systems and the transition from alluvial meadows to agricultural land.