Language: French with trilingual abstract in English, French, and German
This paper deals with the mostly calcareous springs and seepages of the Luxembourg Sandstone area (Lower Jurassic, Luxembourg, Gutland). It gives a short survey of these springs, considering several recent inventories. In the Luxembourg Petite Suisse area less than 10% of the calcareous springs are (still) petrifying nowadays. Many springs happen to be in a bad state of conservation. In order to illustrate on a more scientific basis the value of these fragile sites, a phytosociological examination of the bryophyte vegetation was carried on. Calcareous, more or less petrifying springs (pertaining mostly to the Montio-fontanae-Cardaminetea amarae Braun-Blanq. & Tüxen 1943) were examined, moreover some (rare) springs with an acidophileous vegetation (pertaining mostly to the Pellion epiphyllae Marstaller 1984, notably with Hookeria lucens) and some contiguous wet ecologies. The phytosociological investigation enables us to describe a new sub-association of the Cratoneuretum commutati (Gams 1927) Walther 1942, with Fissidens adianthoides, as well as to recognize two completely different associated groups dominated by Trichocolea tomentella, a species tolerant with regards to the pH level. Two recordings were realised in an extensive pasture near a petrifying spring; the species list includes also, besides some bryophytes pertaining to the Cratoneuretum commutati, the rare Campylium stellatum. Philonotis calcarea has disappeared from this site, as well as from two other places. The vegetation dominated by Conocephalum conicum only partly belongs to the Pellion endiviifoliae; the rare Dichodontium flavescens has been observed three times in this community. pH values were measured in five localities; the vegetation didn't match exactly in all the cases. After an examination of the legal framework, both European and national, pertaining to springs – petrifying or not – and after identifying the reasons why these sites are presently threatened, the authors make several precise proposals on conservation issues and recommend some amendments to the red lists concerning the examined bryophyte flora and vegetation.