Control of bracken and restoration of heathland. IV. Effects of bracken control and heathland restoration treatments on nutrient distribution and soil chemistry

Published source details Marrs R.H., Lowday J.E., Jarvis L., Gough M.W. & Rowland A.P. (1992) Control of bracken and restoration of heathland. IV. Effects of bracken control and heathland restoration treatments on nutrient distribution and soil chemistry. Journal of Applied Ecology, 29, 218-225.
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Summary

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 effects of treatments to control bracken and to restore either heather Calluna vulgaris heath or grassland heath on the amounts of bracken rhizomes, the distribution of nutrients in the vegetation, and selected aspects of soil chemistry, are summarized.

Study sites: The study was undertaken at Cavenham Heath (a heather Calluna vulgaris heath – National Grid ref: TL 755725) 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. The study used a combination of treatment combinations (Marrs & Lowday 1992):

Bracken control: Four treatments were applied to bracken encroached areas on the two heathlands:

i) untreated controls;

ii) cutting once yearly in late July between 1978 to 1984 (cutting using a mechanised sythe, fronds left in situ);

iii) cutting twice yearly in mid-June and late July between 1978 and 1984;

iv) spraying with asulam (4.4 kg active ingredient applied in 400 l water/ha using a motorised backpack mistblower) in August 1978;

Heathland restoration: Each bracken treatment was undertaken with and without seeding (using seed from the local area):

Cavenham – 20,000 C.vulgaris seeds sown/m²;

Weeting – a seed mix of Yorkshire fog Holcus lanatus, fescue spp. mainly F.ovina bird's-foot trefoil Lotus corniculatus and common sorrel Rumex acetosella (5,000, 10,000, 600 and 4,400 seeds/m² respectively).

Continuous or repeat bracken control or treatment cessation:

i) Continuous/repeat treatment with cutting annually from 1978 to sampling and asulam reapplied in 1985.

ii) Bracken control ended in 1984

A randomised block design was used (4 x 2 x 2) in two10 x 7 m plots with a central 6 x 3 m sampling area, each surrounded by a 1 m cut pathway.

Sampling: Rhizome sampling was undertaken in late April at Cavenham and late February at Weeting. Ideally for this type of study samples should be taken in late April/early May but due to presence of breeding stone curlew Burhinus oedicnemus (a fully protected species in the UK) at Weeting, samples had to be taken earlier. Bracken litter samples were collected and soil cores taken to be analysed in the laboratory.

The effects of the bracken control treatments on bracken rhizomes were similar to those reported earlier (Marrs & Lowday 1992) for midsummer bracken-frond yields. The most successful treatment was cutting bracken twice yearly for at least 10 years, which reduced frond-bearing rhizomes to 2-4% and storage rhizomes to 8-11% of untreated levels.

At both heaths there were differences in the amounts of nutrients in the bracken rhizomes and litter in the untreated plots. The maximum potential flux of nutrients to the soil was lower for some elements in plots with maximum heath development or bracken recovery, but for other elements no significant effects were found.

There were a few significant differences in soil chemical properties between the different management treatments, but they were difficult to interpret. There was no evidence of any reduction in soil chemical properties in these experiments where Calluna heath (at Cavenham) and grassland heath (at Weeting) have re-established.

References
Marrs R.H. & Lowday J.E. (1992) Control of bracken and restoration of heathland.II. Regeneration of the heathland community. Journal of Applied Ecology, 29, 204-211

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