How is plant biodiversity inside grassland type related to economic and ecosystem services: An Estonian case study

Biodiversity is globally recognised as a cornerstone of healthy ecosystems and extensive management is assumed to increase biodiversity in all grassland habitats. Often, the maintenance of these semi-natural grasslands via mowing or grazing is financially subsidized and different ecosystem benefits are associated with the plant biodiversity value. These assumptions are usually made after comparing different ecosystems or management options. However, less information is available about the relations between plant biodiversity and ecosystem services in practice. Hence, we studied the impact of biodiversity on the fodder quantity and quality in two different semi-natural grassland habitats. We also checked if the species more commonly found in sites with higher biodiversity are more endangered in comparison to the rest of the species and if they have special site requirements in terms of Ellenberg indicator values. The soil of Estonian calcareous grasslands had higher pH as well as organic matter and Nitrogen content than the soil of Estonian mesic grasslands (habitat 6270). However, the average annual biomass production in the first ones was significantly smaller most probably due to water shortage. No clear relation between site productivity and plant species number was detected in either habitat. The average species number in both studied habitats was almost similar, but the median species amount in mesic grasslands was more than 13% higher than that in calcareous grasslands. Crude protein along with starch & sugar content in the calcareous grassland biomass tended to be lower than in mesic grasslands. In the last habitat, the content of these two components favoured both for fodder and biogas purposes tended to be lower in sites with more species. Positive correlations were found between species number and biomass detergent fibre contents, which is why it must be inferred that plant biodiversity does not improve grassland biomass quality. We detected several species of the Near Threatened category from the IUCN red list, but none of these appeared in our list of species that grew with higher probability in grasslands with higher plant biodiversity. According to principal component analyses, these listed species are less common, less nutrient demanding and more salt tolerant than the rest of the plant species found in calcareous grasslands and more common than the rest in mesic grasslands species. We conclude that high site biodiversity does not guarantee any larger income for the typical bioeconomy products, so other potential economic services should be included to the farm's budget.