On arable land, weeds are often the only plant food source and habitat structure for insects and farmland birds besides crops, and are thus one of the most important foundations for a species-rich field. Higher weed diversity can support ecosystem services such as higher pollination and biological pest control. As weeds can be host plants for both beneficial insects and pests, it is important to look not only at weed abundance, but also at the species diversity of the weeds. A positive or negative influence on the cultivated crop can therefore result from the individual weed species and associated insect species.
In the MonViA module "Arable Weeds", a monitoring concept was therefore designed for a national monitoring of the diversity of arable weeds. The aim is to continuously record the diversity of weeds throughout Germany in order to be able to map long-term trends in their development. In this way, future changes in the management of arable land (increase in organically managed arable land, changes in plant protection application regulations) can be mapped and the effects of current political strategies can be assessed.
From theory to practise
Various acquisition methods have already been compared in the past. The selected method should be characterised in particular by an efficient recording of the species present on the field. For the current test phase of the monitoring concept, the transect inspection was chosen as a suitable method for monitoring weed diversity. For this purpose, it is proposed that a total of three transects with a length of 100 x 1 m are established per arable field, focussing on the weed vegetation in the inner part of the field. Along the transects and in the squares, the weed species present are recorded with their respective abundance (frequency). For the selected plots, primary data on the type and intensity of use will also be collected (e.g. crop) as well as the management method (conventional or organic). For a future, long-term monitoring at national level, a number of approximately 500 plots is proposed.