Effects of grassland management on plant functional trait composition

Abstract

Semi-natural grasslands are threatened in Central Europe by intense fertilisation, afforestation or abandonment due to changes in agricultural practice during the last decades. Nature conservation but also management within the EU agri-environmental schemes (cross compliance with national good farming practices) seek to maintain these grasslands by management. The study presented here investigated the effects of different management treatments on grassland vegetation of various vegetation types. The treatments were low-intensity grazing, mulching once and twice a year and burning in winter. We investigated plant functional trait responses to the treatments aiming to identify dominant or differentiating processes of the treatments ruling trait responses. We assume that the processes ‘selective removal of the phytomass by grazing’, ‘small scale soil disturbances’, ‘treatment frequency’, ‘nutrient conditions’, ‘vertical defoliation’ and ‘timing of the treatment’ are associated with the response of the plant functional traits ‘life form’, ‘plant height’, ‘canopy structure’, ‘specific leaf area’, ‘storage organs’, ‘lateral spread’, ‘plant persistence’, ‘seed bank longevity’, ‘start of flowering’, ‘duration of flowering’ and ‘seed mass’. All treatments maintained grassland vegetation by regular phytomass removal with hemicryptophytes and perennials with clonal growth being dominant. Grazing encouraged woody life forms through selective removal of the phytomass and species with small seeds and persistent seed bank. A relation to soil disturbances was discussed. Mulching treatments were especially characterised by increasing dominance of ground-layer species through regular vertical defoliation close to the ground. Burning in winter benefited species with storage capacities for nutrients withdraw. The traits ‘plant height’ and ‘SLA’, associated with treatment frequency and nutrient conditions, as well as the phenological traits ‘start’ and ‘duration of flowering’, associated with the timing of the treatments, did not respond differently among the treatments. The study shows that the grasslands show a convergent response to management treatments from a functional point of view although they may be floristically divergent. Therefore, a functional approach is useful not only to understand the mechanisms behind changes in vegetation after applying certain management treatments but also to predict changes.