Abstract: Bracken young shoots oil Ha mpsfell in England appeared above ground in the middle or end of April and grew rapidly in the first two months. The maximum height of fronds was reached in September and the peak weight of fronds appeared in August.The peak biomass of bracken aerial part on Hampsfell averaged 792g.m-2 in August and then declined. The bracken aerial part died in November. The seasonal variation of bracken below ground biomass was not marked but the below ground biomass more or less increased with the growth of aerial part. The depth of soil was the most important factor influenced on the bracken biomass of Hampsfell. The primary production of bracken ecosystem averaged 778g.m-2yr-1, with maximum yield of 918g.m-2yr-1 on deep soil and minimum yield of 525g.m-2yr-1 on shallow soil.