Enhancing temperate grassland diversity and functionality: Crafting seed mixtures to align stakeholder interests and to increase establishment success

Grassland biodiversity is positively correlated to ecosystem productivity and resilience that secure net gains and functionality of such systems. Land-use change of grasslands is associated with local extinction of species and declining ecosystem services. Hence, the design of more diverse seed mixtures is crucial for successful species reintroduction and grassland functionality. Thus, we conducted a systematic review of the scientific literature on temperate grassland reseeding during the past 30 years. This generated a knowledge base of reseeding methods and success, and revealed knowledge gaps and mismatches in the design of seed mixtures created by different stakeholders. From 201 published studies, we extracted information on stakeholder groups and focus, starting conditions, species selection for the mixtures, and monitoring of reseeded grasslands. Our review showed: (i) There were five stakeholder groups with varying focus along a gradient of biodiversity control; in turn, the starting conditions of reseeded sites changed along a gradient of dissimilarity in relation to reference grasslands. (ii) The design of the grassland mixtures varied in species composition, seed origin, and seed quality. (iii) While mixtures aiming at a certain vegetation structure and biomass showed high establishment success, grassland reseeding with a biodiversity focus was less successful. (iv) The design of seed mixtures changed significantly during the past decades, since species numbers in mixtures, i.e., the biodiversity focus, and the proportion of forbs, which indicates lower productivity, decreased in most stakeholder groups. (v) The number of ecosystem services monitored, i.e., the proportion of multiple-to-single ecosystem services, also declined for most stakeholders. Such findings indicate a narrowing focus on specific grassland composition and functions by stakeholders, in contrast to current trends toward multiple ecosystem services. The different establishment success of stakeholders conducting temperate grassland reseeding call for knowledge transfer among groups to achieve higher establishment success in restoration and conservation professionals as seen among turf managers and farmers. Overall, the design of grassland mixtures needs to be revisited in the face of the current biodiversity losses and climate change.