Contemporary floristic changes in the Karkonosze Mts.

Abstract

The paper presents the transformations of species composition in the main plant communities of the Karkonosze Mts. subalpine and alpine belts during the last 35 years. The investigations of floristic changes were performed in associations: <em>Carici (rigidae)-Nardetum</em>, <em>Carici-Festucetum supinae</em>, <em>Crepidi-Calamagrostietum villose</em> and <em>Empetro-Vaccinietum</em>. Signalized are also some vegetation transformations in the remaining belts. The progressing floristic degradation of plant communities in the subalpine and alpine belts consists in: (a) expansion of grasses, (b) decline of rare vascular plants, and (c) elimination of terricolous bryophytes and lichens. In spruce forest belts declining are species connected with old-growth spruce forests like: <em>Listera cordata</em> and <em>Moneses uniflora</em>. The changes of plant communities of low mountain swards (<em>Nardetalia</em>) caused by cessation of pasture and mowing in the cause of retreat of many rare plants, like e.g., <em>Arnica montana</em>. The main cause of the still lasting in the Karkonosze Mts. community transformations is the changes in soil environment connected with anthropogenic nitrogen fertilization. The large inflow of mineral nitrogen from the atmosphere (1138 mg/m² sum for vegetation season) is the reason of accelerated rate of decomposition of organic matter and intensified nitrification. The high content of nitrates in soil (5 times higher than in the Tatra Mts. swards) is the reason of expansion of graminoids, mainly <em>Deschampsia flexuosa</em>, <em>Calamagrostis villosa</em> and <em>Carex bigelowii</em> subsp. <em>rigida</em>. The overfertilisation of habitats causes the retreat of rare high mountain vascular plants and the decline of terricolous bryophytes and lichens.