Aspects of ecotoxicology of sulphur in the Harz region - a guided excursion

Sulphur has become a major limiting factor for plant production during the last decades. In its initial stages, an insufficient S supply can only be detected by quantification of S in plant tissue with chemical methods. Severe S deficiency, however, can be identified by visual symptoms. An excursion to the Harz Mountains region not only provides the opportunity to study various visual symptoms of S deficiency in the field, but also provides insight into aspects of the ecotoxicology of sulphur. Oilseed rape fields around Silstedt and Ilsenburg display a variety of typical symptoms of S deficiency such as chlorosis starting from the leaves' edge and spreading over into intercostal areas, reddish purple colouring due to the enrichment of anthocyanins, spoonlike deformations of leaves, succulence of leaves, reduced petal size or white blooming. S deficiency also affects yield structure, which is revealed in a reduced number of seeds per pod. Decreasing concentrations of airborne sulphur over the past few decades may have an impact on the composition of plant communities, which is displayed by epiphytic lichen communities near the Kasteklippen at Romkerhall. On the other hand, a surplus of sulphur may impair plant performance, too. An example for this can be studied on mosses growing in bogs in the High Harz Mountains. A soil of calcium-sulphate origin may also give rise to the development of a specialised plant community, with plant specimens being able to store up to three times the amount of sulphur in their leaves compared to specimens growing on calcium carbonate soils. Plant communities on gypsum soils can be seen in the Hainholz near Horden. A geogenic source of sulphur exists at Rhumspringe at the southern Harz rim, where the Rhume karst spring delivers up to 5500 L of sulphur enriched water per second after high precipitation. The total annual discharge amounts to 7092 t S.