The long-term effects of monoculture maize cultivation on plant diversity

Biodiversity loss is one of the most serious global environmental problems caused by human activities. The intensification of agriculture and the increasing presence of monocultures is one of the main reasons for this. To study the long-term effects of maize monocultures compared to crop rotation systems on vegetation and biodiversity, two nearby sites in the small village of Metschach in Central Carinthia, Austria, were monitored for 30 years. These two test sites with intensively used arable land, divided into maize and crop rotation (14.5 ha in total) were taken out of production in 1989 as part of a nature conservation project. Changes in the composition and abundance of vascular plant species were recorded in 29 permanent plots. The monitoring showed that the previous use has long-lasting effects on species richness and ecological indicator values of the fallow land: The species numbers of the former maize field remained on average 10 species below those of the former crop rotation field over the entire study period. After 30 years, the plant communities in the former crop rotation revealed tendencies towards species-rich grassland communities, whereas in the former maize monoculture Elymus repens or tall herbaceous fringe communities remained dominant. Ecological indicator values showed predominantly higher moisture and nutrients values in the former maize cultivation over the entire study period. Overall, this study underlines the importance of monitoring to unravel long-term effects of different crop types on biodiversity. In particular, it highlights the need for additional monitoring programmes in comparable ecosystems, including in-situ measurement of temperature, moisture and nitrogen.