The long-term recovery of a moderately fertilised semi-natural grassland

Semi-natural grasslands (SNG) are ecosystems whose characteristics can only be maintained by continuous human husbandry. Extensive management without ploughing, sowing or fertilising is advocated to ensure the durability of the various ecosystem services provided by these plant communities. As a semi-natural grassland rich in plant species, the Laelatu wooded meadow in western Estonia has been the subject of numerous studies. A fertilisation experiment conducted between 1961 and 1981 and the later annual observations in some areas of the meadow have provided longitudinal data for evaluating the impact of fertilisation and monitoring recovery time following the application of mineral nutrients. The characteristics under investigation were plant biomass, divided by functional groups (grasses, sedges & rushes, legumes and other herbaceous species) and species richness. Fertilisation caused a more than fourfold increase in biomass, which persisted over the following 10 years after the end of experiment. However, differences in biomass could no longer be detected during the later years of observation. On fertilised plots, ratios of forbs and sedges & rushes biomasses decreased from the second treatment year and were replaced mainly by legumes and/or grasses. In some of those plots, the higher ratio of legumes was noticeable even 35 years after the last fertilisation. Similarly, the number of plant species has not yet reached the level of the control plots. On that basis, intensification of SNG management cannot be advocated for conventional agricultural or bioeconomy purposes.