The implications and effects of bracken (Pteridium aquilinum (L.) Kuhn) control on species diversity, re-vegetation and bracken preformance

Susan Cox, Emma (2007) The implications and effects of bracken (Pteridium aquilinum (L.) Kuhn) control on species diversity, re-vegetation and bracken preformance. PhD thesis, University of Liverpool.

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Abstract

Pteridium aquilium is the most widely distributed of all the pteridophytes; it is present throughout the world with the exception of hot and cold desert regions. Originally a component of open woodland commun.ltIes ItS. range has extended markedly as a result of mans' activities. The problems caused by bracken mfestatlOn are many and varied. Bracken infestation can cause considerable loss of revenue for farmers in terms of the reduction in available grazing land and through additional expenses such as veterinary fees and control costs. The quality of grazing is reduced due to the shading out of understorey vegetation. It also competes effectively with Cal/una and other heath and grassland species, at best reducing their cover but in some cases eliminating them. The control of Pteridium aquilinum requires a long-term strategy and when planning to undertake control at least a five year programme should be considered. One of the reasons bracken is so hard to control is its extensive rhizome system that can potentially live for more than 50 years. Segments as small as 9 cm are able to grow. A fundamental limitation in vegetation management and restoration ecology is the ability to predict, with some degree of precision the likely outcome of a proposed treatment across a range of sites. A great deal of money and effort is being placed into controlling invasive weeds as part of international and national policies, for example within the UK agri-environment schemes and Biodiversity Action Plans. One of the major issues highlighted in Pteridium aquilinum control is the high variability in success rates, and a cost-effective control strategy has proved elusive. Alongside this, the need for long-term, fully replicated experiments is often highlighted in restoration ecology. In this thesis long-term, multi-site bracken control experiments were analyzed to assess efficacy of various control treatments and subsequent re-vegetation. The experiments assessed the efficacy of five treatments designed to control Pteridium aquilinum relative to an untreated comparison in a range of contrasting ecological situations. These control treatments were also combined with site-specific treatments designed to restore appropriate heathland or grassland vegetation. In addition two methods of bracken control, bruising and the current manufacturers' guidelines for Asulox application, previously untested in formal experiments were studied. Long-term control of bracken at all sites was best achieved using a continuous cutting treatment, preferably twice per year. As expected re-spraying previously treated bracken with asulam caused a reduction in all bracken response variables at both sites tested. The rate of recovery after ten years of bracken control is dependent of the initial degree of control, which presumably reflects the starting rhizome biomass of the bracken. It, is difficult to develop a one-size-fits-all policy for vegetation restoration within a Pteridiu11l aquilinll11l control strategy, with analysis finding a considerable number of spatial effects between sites of similar vegetation type and located <2.5 km apart. Few bracken control treatment effects were found and where they were detected it was only at single sites. Thus, the development of target vegetation requires a combination of control and restoration treatments that take into consideration the aspects of that site. After only one year of treatment, the results show support for the theory that bruising is less effective than cutting as a mechanical control. All bracken response variables in August and Pteridiul1l aquilinll11l cover in June increased in the rolled three times per year plots compared with the untreated control, rather than the desired decrease. Bruised fronds were found to remain alive and green for up to seven weeks after the initial bruising treatment, with no significant difference between the photosynthesis and transpiration rates in bruised and untreated fronds. Even in severely damaged fronds key structures such as the xylem vessels remaining intact, despite extensive damage to other tissues. However there was no evidence of the 'rhizome being bled dry' as none of the bracken control treatments had any impact on the rhizomes.

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	20 Oct 2023 09:24
Last Modified:	20 Oct 2023 09:48
DOI:	10.17638/03174385
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3174385