Long-term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex-arable fields

Published source details Lepŝ J., Doleẑal J., Bezemer T.M., Brown V.K., Hedlund K., Igual Arroyo M., Jörgensen H.B., Lawson C.S., Mortimer S.R., Peix Geldart A., Rodríguez Barrueco C., Santa Regina I., Ŝmilauer P. & van Der Putten W.H. (2007) Long-term effectiveness of sowing high and low diversity seed mixtures to enhance plant community development on ex-arable fields. Applied Vegetation Science, 10, 97-110.
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This study is summarised as evidence for the following.

	Action	Category
	Sow native grass and forbs Action Link
	Restore/create species-rich, semi-natural grassland Action Link

Sow native grass and forbs

A replicated, randomized, paired, controlled study in 1996–2003 in five ex-arable fields in the Czech Republic, the Netherlands, Spain, Sweden, and the UK (Lepš et al. 2007) found that sowing grass and forb seeds had mixed effects on plant species richness but increased biomass. Initially, in one of two comparisons, sowing seeds increased plant species richness (38 species/plot) compared to areas where no seeds were sown (27 species/plot), but in one of two comparisons there was no significant difference (30 species/plot). However, after eight years, species richness of areas sown with seeds (26–27 species/plot) was not significantly different to that found in areas where no seeds were sown (32 species/plot). After two years, plant biomass was higher in areas where seeds were sown (0.59–0.71 kg/m²) than in unsown areas (0.3 kg/m²), and the same was true after eight years (sown: 0.50–0.64 km/m²; unsown: 0.46 kg/m²). In each site, ten 10 x 10 m plots were sown with a seed mix of either four or 15 grass, legume and other forb species, while five plots were not sown with seeds. Grasses were sown at a rate of 2,500 seeds/m², and legumes and other forbs at a rate of 500 seeds/m². All plots were mown at least once a year. In each plot, the vegetation in twelve 1 x 1 m quadrats was surveyed in 1996–1998 and 2002–2003. Biomass was estimated by cutting and drying all vegetation in twelve 0.25 x 0.25 m quadrats placed within the plots.

(Summarised by: Philip Martin)
Restore/create species-rich, semi-natural grassland

A replicated controlled experiment in five European countries (Leps et al. 2007) from 1996 to 2003 (the same study as (Gormsen et al. 2004)) found that most hay meadow species sown on plots of abandoned arable land established well at four locations (all except Sweden, where less than half of the sown species established). In the UK, the Czech Republic and the Netherlands, more than 70% of the sown species were established after eight years. Grasses, bird’s-foot trefoil Lotus corniculatus and red clover Trifolium pratense established well at almost all sites, but small legumes, black medick Medicago lupulina and lesser hop trefoil Trifolium dubium disappeared quickly at all except the UK site. The success of other plant species varied between sites. Plots sown with 15 plant species always established some of the sown species, while some plots sown with just four plant species failed to establish any. Plots (10 x 10 m) were either left to naturally regenerate, or sown with four or 15 plant species in autumn 1995. The experiment was repeated in five countries: the Czech Republic, the Netherlands, Spain, Sweden and the UK, with five replicates of each treatment. Plant species naturally occurring in local grassland systems were sown. Red fescue Festuca rubra, Timothy grass Phleum pratense, bird’s-foot trefoil, red clover, and ribwort plantain Plantago lanceolata were sown at all sites. All plots were mown once or twice a year and separated by 2 m borders. Plant cover was measured from 1996 to 1998 and 2002 to 2003, in ten 1 m² quadrats/plot.