Individual study: Effects of herbicide and cutting on the control of bracken Pteridum aquilinum at Cavenham and Weeting Heaths, Suffolk, England
Marrs R.H., Pakeman R.J. & Lowday J.E. (1993) Control of bracken and restoration of heathland. V. Effects of bracken control treatments on the rhizome and its relationship with frond performance. Journal of Applied Ecology, 30, 107-118
In many areas of Britain, bracken Pteridum aquilinum although a native species, can be a highly invasive, especially on marginal land such as heath and moorland on acidic soils. The effect of three bracken control treatments (cutting once and twice yearly, and spraying with herbicide) on the rhizome system of bracken on two heaths in Breckland, eastern England was assessed.
Study sites: Cavenham Heath (a heather Calluna vulgaris heathl – National Grid ref: TL 755725) in and Weeting Heath (a grass heath, mainly sheep's fescue Festuca ovina - National Grid ref: TL 757885) in the Breckland region of Suffolk, eastern England.
Bracken control treatments: Treatments applied to bracken encroached areas on the two heathlands were:
i) untreated controls
ii) cutting once yearly in late July between 1978 and 1990,
iii) cutting twice yearly in mid-June and late July between 1978 and 1990
iv) spraying with the herbicide asulam at the recommended rate (4.4 kg a.i./ha applied as Asulox™) in 1978 and 1985.
The effect of continuous treatment was compared with plots in which bracken control ceased after 6 years. The effects on rhizome biomass and length, numbers of active and dormant buds, and starch and soluble carbohydrate concentrations were measured.
Cutting bracken twice yearly was the most effective bracken control treatment, but rhizomes persisted even after 12 years of continuous treatment. Cutting once yearly and applying asulam gave intermediate reductions in all rhizome variables measured (i.e. biomass, length, number of active and dormant buds, starch and soluble carbohydrate concentrations).
Where bracken control ceased there was a relatively rapid increase in rhizome performance; at Cavenham remission for 4 years increased the starch levels in rhizomes, and after 6 years increased all rhizome measures; at Weeting all rhizome measures significantly increased within 5 years of cessation of treatments.
Analyses showed that the majority of the variation in summer frond performance (0.39-0.75) could be explained by rhizome biomass.
Conclusions: Cutting bracken twice yearly was the most effective bracken control treatment at both heathland sites, but rhizomes persisted even after 12 years of continuous treatment. Cutting once yearly for a similar period or applying Asulam at the recommended rate once and after six years reduced bracken rhizome biomass compared to untreated control plots, but these treatments were less effective than cutting twice yearly.
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