A promising new tool for enhancing grassland biodiversity in fragmented landscapes: high-diversity sowing in establishment gaps

Abstract

Halting the loss of grassland biodiversity and restoring degraded ecosystems are high priority tasks in the fragmented landscapes. In fragmented landscapes there are limited amount of propagule sources of grassland specialist species. Our aim was to develop and test a novel approach to increase the diversity of species-poor grasslands in fragmented agricultural landscape. We created establishment gaps by ploughing the dense grass sward and sowing a high-diversity seed mixture of 35 grassland specialist forb species. We established three grazed gaps (1×1 m, 2×2 m and 4×4 m) and one fenced gap (4×4 m) per site and monitored the presence and abundance of sown and non-sown species. We asked the following questions: (i) Which target species establish most successfully? (ii) What is the effect of establishment gap size on the establishment success of target species and weeds? (iii) What is the effect of management (grazed versus not managed) on the species composition of the establishment gaps? We showed that by creating establishment gaps and sowing diverse seed mixtures, we could overcome microsite and propagule limitation, successfully introducing target species into the species-poor grasslands. We found that all sown species established in the gaps, and the majority of the species maintained or even increased their first-year cover in the second year after sowing. Smaller gaps were characterised by lower cover of sown species and quite stochastic vegetation development compared to the larger ones. Weed cover was moderate in the first year and decreased significantly in the second year, regardless of gap size. Therefore, we recommend the use of larger establishment gaps in restoration practice. We found that the cover of sown species and weeds were similar in the grazed and unmanaged gaps. However, management by extensive grazing might be crucial in the long-term because livestock can disperse target species propagules and also create microsites. Our study showed that establishment gaps can serve as biodiversity hotspots in fragmented landscapes and can act as stepping stones for the dispersal of target species in the future (Valkó et al. 2016).

Valkó O., Deák B., Török P., Kirmer A., Tishew S., Kelemen A., Tóth K., Miglécz T., Radócz Sz., Sonkoly J., Tóth E., Kiss R., Kapocsi I., Tóthmérész B. 2016: High-diversity sowing in establishment gaps: a promising new tool for enhancing grassland biodiversity. Tuexenia 36: 359-378.