The variable responses of bracken fronds to control treatments in Great Britain

We describe six experiments set up at four regional locations in Great Brit ain, in 1993 and 1994, to examine the impact of control treatments on brack en and associated vegetation. Present discussion is limited to the effects of treatments on bracken frond variables (density, length and dry mass). Th ese variables would be used by a land manager to judge the extent of infest ation and the efficacy of control methods. Results of statistical analyses are reported for the period 1994 to 1998, inclusive. The treatments showed great variability in effectiveness between both sites and years. Great inte r-regional differences were seen, but stands at sites within a short distan ce of each other also varied in their response to treatment. Meso- and micr o-climatic differences are suggested as possible causes, together with stan d growth phase and genetic effects. The most effective treatments in the sh ort-term were found to be combinations of cutting and herbicide spraying, a pplied once. Annual cutting usually gave a better result in the longer term . All treatments had greatly improved effects when combined with a follow-u p application of herbicide several years after commencement. A number of re commendations are given for management, such as best methods for short- and long-term results. Systematic monitoring is urged as changes in frond dens ity, for example, may reveal the extent of the problem for control at a par ticular site. (C) 2000 Annals of Botany Company.