Control of bracken and the restoration of heathland. III. Bracken litter disturbance and heathland restoration.
In trials in the Breckland region (Norfolk/Suffolk border) UK in 1978-88 on Calluna vulgaris heathland and grass heathland (dominated by Festuca ovina) sites, bracken (Pteridium aquilinum) was sprayed with 4.4 kg asulam/ha in Aug. 1978. The litter was undisturbed, rotary cultivated into the mineral layers of the soil, burned, or removed by raking. Bracken control treatments were implemented with or without sowing 20 000 seeds of C. vulgaris/m2 on the Calluna heathland and with or without sowing a mixture of Holcus lanatus, Festuca spp. (mainly F. ovina), Lotus corniculatus and Rumex acetosella (at 5000, 10 000, 600 and 4400 seeds/m2, respectively) on the grass heathland. Bracken regrowth was removed by hand-pulling fronds 3 times/year in 1979-86. At both sites, litter disturbance increased the speed of colonization and subsequent development of the sown heathland species. At the Calluna site, litter removal was the most effective treatment. At both sites the rapid establishment of the sown species reduced natural colonization of other species. After 11 years, bracken reinvasion was reduced 15-20 m away from surrounding dense bracken edges at the grass heath. The implications of the results for conservation management and heathland restoration are discussed.