Der Färberwaid (Isatis tinctoria L.) - ein Beitrag zur Vegetationsökologie und Biozönologie
In the southern Upper Rhine region 3 mass proliferations of Isatis tinctoria L. were observed since 1978, the last in 2005. Long-term observations in the Kaiserstuhl revealed that such “waves” followed a drought period and collapsed after 2 - 3 years. Because dyer's woad (also called German indigo) has been an important crop plant culture-historically and today is known as a troublesome pest in North America, in 2005 it was investigated phytosociologically and with regard to its monophagous beetles, documented nearly 3 decades by trap captures. A semiquantitative detailed mapping in the Kaiserstuhl showed dominance in the most xerothermic southwestern and central part, and absence in the somewhat moister northeastern part. The qualitative analysis of stands revealed high demands on soil aeration and temperature, as well as for light intensity, thereby indicating weak competition. Moreover, it evidently shows poor dispersal ability. The coincidence with the mass increase of monophagous beetles, especially Psylliodes isatidis, explains the rapid decline of the population of Isatis. In a literature comparison Isatis tinctoria turned out to be, at least in southern Germany, a weak character species of the Convolvulo-Agropyrion repentis, the only alliance of the Agropyretea intermedio-repentis present here.
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