|European Weed Research Society. Abstracts. EWRS workshop weeds and biodiversity, Salem, Germany, Universität Rostock 14-15 March 2007
T. Hyvönen, E. Huusela-Veistola, J. Salonen1
MTT Agrifood Research Finland, Plant Production Research, FI-31600 Jokioinen, Finland,
Monitoring of the populations of organisms associated with farmland provide information on the sustainability of cropping measures. Recently, interest in the application of arable weeds as an indicator group has grown. This study aimed at to develop an indicator based on the interactions between weeds and animals associated with weeds for the sustainability of cropping measures.
The relative importance of 25 common weed species for farmland birds, pollinators (wild bees), phytophagous insects and pests was explored by recording the number of linkages between weed species and each animal group found from the literature. The weed species were ranked by weighting them by the relative number of above weed-animal linkages. The application of these weights for the exploration of the importance of the long-term changes in weed populations for each animal group in focus was demonstrated. The data of three weed surveys of Finnish spring cereal fields, those conducted in 1961-1964, in 1982-1984 and in 1997-1999, were used for this purpose. The relative area of the herbicide-treated and organically cropped fields in each survey were involved in the calculations.
The literature review showed the relative importance of weed species to vary between animal groups. For farmland birds, annual weed species that are able to produce a high number of seeds (e.g. Chenopodium album, Polygonum aviculare) got high ranks. For pollinators, the most important weed species were insect pollinated plants (e.g. Achillea species, Cirsium arvense and Sonchus arvensis). In the case of phytophagous insects, the variation in the number of linkages between weed species was high. Furthermore, some weed species (e.g. Elymus repens, Galium species) that were not found important for other animal groups was found to be important for phytophagous insects. The number of pest species associated with weeds found in Finland remained low for all weed species. The most important weed species for the pests was E. repens.
The general pattern in the changes of the values of indices between decades was similar: a tremendous decline in the values between the 1960s and the 1980s, and a slight increase between the 1980s and the 1990s. The changes in the values of the index of farmland birds were more pronounced between decades compared to other indices, which was due to tremendous changes in the density of some important seed-food plants for farmland birds (e.g. Chenopodium album). The changes in the weed density and in the values of pest index followed the same trend as the values of indices of the animal groups.
The results showed all indices to react with tremendous decline in their values to the intensification of agriculture between the 1960s and the 1980s. In the 1990s, some positive changes in the cropping measures for biodiversity has occurred, e.g. increase in the area of organic farming. However, despite the benefits of organic cropping for the biodiversity its significance remained minor due to small acreage. Weed species were shown to differ in their importance to other organisms associated with farmland. Indicator based on these differences proved to be applicable in the assessment of the long-term changes in weed populations, enabling the interpretation of the ecological importance of the changes.