Biologisch-Ökologische Grundlagen des Schutzes Gefährdeter Segetalpflanzen [Biological-Ecological Bases of Protection of Endangered Weeds]

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Language: German with English summary

For the last fifteen years Germany has attempted to protect its endangered arable weeds. The eastem part of the country (formerly GDR) achieves this with fields kept as nature reserves, which are protected by law and managed according to traditional agricultural methods, whereas westem Germany favours field border strips, land of several meters on the edges of the fields, which apart from a ban on weed control and fertilization is managed as intensively as the adjacent land. Weeds are less effectively protected in this system. Basing our study on the biological and ecological prerequisites of endangered arable weeds, we have tried to show that every aspect of modem intensive farming has greatly contributed to their decline and would suggest that conservation procedures should be equally far-reaching. Today in Germany, 134 of the 350 arable weeds of Central Europe are extinct, endangered or rare (Table 1-1). Emphasis is placed on weeds growing in cereal crops (”cornfield weeds“, 109 species) and their preservation requirements.

In Chapter 3, 10 species are described. Taking into account their biological characteristics and habitat requirements, the causes of their decline are analysed and the necessary measures for their preservation suggested. Apart from a ban on weed control and fertilization, crop rotation and cereal density must be modified and stubble should be left unworked.

To show the relative importance of these preservation measures, biological and ecological data for many endangered arable weeds are listed in Chapter 4: native and introduced field weeds (Table 4-1, 4-2), seed weight (Table 4-4), germination depth (Table 4-5), mean seed output (Table 4-6), speirochoric weeds (Table 4-7), germination and seed ripening time (Table 4-9), life cycles (Table 4-11), and susceptibility to growth regulator herbicides (Table 4-12).

In Chapter 5 conservation requirements are summed up. The genetic variability of endangered arable weeds can only be sustained on sites managed as farmland which is worked in a traditional way. It is highly important that existing populations are protected and their whereabouts recorded as soon as possible. Apart from speirochoric species, endangered cornfield weeds can be conserved if no herbicides are used and if stubble is left untouched after harvesting. When these conditions are fulfilled such weeds may survive at least on the field margins. This minimal survival habitat can be enhanced by avoiding dense cereal stands. These three measures should suffice for long-term conservation providing one ensures that there is neither set-aside nor perennial cultures. To improve protection in field border strips agreement must be reached with farmers on these points. However, even then protection will not be total, because certain aspects of intensive farming must be retained. Total protection is only possible in field nature reserves but their management is complicated and long-term. As field border strips are more easily established the conservation of endangered arable weeds is more likely to take place in this way. Field border strips and field nature reserves complement each other and should be treated in the same context.

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