RECREATING SEMINATURAL COMMUNITIES - EFFECT OF SOWING RATE ON ESTABLISHMENT OF CALCAREOUS GRASSLAND

Restoration ecologists are increasingly aware of the potential to re-c reate chalk grassland on abandoned farmland. Success is often hampered by lack of desirable species in the seed bank and by poor dispersal f rom nearby sites. In certain schemes, the input of seed may be essenti al. Locally collected seed is desirable but availability is limited. W e examined whether lower sowing rates than currently recommended may b e successfully utilized, facilitating more-efficient use of available seed. Experimental plots on former agricultural land were sown at diff erent rates in a randomized complete block, and the vegetation was sur veyed for two years. We compared species richness and cover for chalk grassland plants and weeds-species not associated with chalk grassland communities. Values for cover and abundance were matched with data fo r communities of the British National Vegetation Classification (NVC). Species richness for chalk grassland plants increased with sowing rat e and with time, although after two years there was no significant dif ference between the treatments sown at 0.4, 1.0, and 4.0 grams of seed per square meter. Weed species decreased with increasing rate and tim e. After two seasons, the vegetation on all treatment plots was simila r to that of recognized NVC chalk grassland communities, while the con trols were dominated by weeds and showed signs of developing into spec ies-poor grassland. Higher rates rapidly eliminated weeds, but even a small inoculum of seed seemed to significantly enhance establishment o f desirable plants and to reduce weed cover. We conclude that lower so wing rates would enable the desired vegetation to become established s uccessfully, under appropriate conditions and management regimes. Lowe r rates allow for the re-creation of sizable areas using local seed, a nd they minimize damage to donor sites.