Abstract
AbstractQuestionsHow can we quantify changes in the distribution and abundance of injurious weed species (Senecio jacobaea,Cirsium vulgare,Cirsium arvense,Rumex obtusifolius,Rumex crispus and Urtica dioica), over long time periods at wide geographical scales? What impact do these species have on plant communities? To what extent are changes driven by anthropogenically induced drivers such as disturbance, eutrophication and management?LocationGreat Britain.MethodsData from national surveys were used to assess changes in the frequency and abundance of selected weed species between 1978 and 2007. This involved novel method development to create indices of change, and to relate changes in distribution and abundance of these species to plant community diversity and inferred changes in resource availability, disturbance and management.ResultsThree of the six weed species became more widespread in GB over this period and all of them increased in abundance (in grasslands, arable habitats, roadsides and streamsides). Patterns were complex and varied by landscape context and habitat type. For most of the species, there were negative relationships between abundance, total plant species richness, grassland, wetland and woodland indicators. Each individual species responds to a different combination of anthropogenic drivers but disturbance, fertility and livestock management significantly influenced most species.ConclusionsThe increase in frequency and abundance of weeds over decades has implications for landscape‐scale plant diversity, fodder yield and livestock health. This includes reductions in plant species richness, loss of valuable habitat specialists and homogenisation of vegetation communities. Increasing land‐use intensity, excessive nutrient input, overgrazing, sward damage, poaching and bare ground in fields and undermanagement or too frequent cutting on linear features may have led to increases in weeds. These weeds do have conservation value so we are not advocating eradication, rather co‐existence, without dominance. Land management policy needs to adapt to benefit biodiversity and agricultural productivity.
Highlights
Human-induced environmental changes such as eutrophication, land use change, land intensification, disturbance or changes in the management regime may be facilitating the spread of species with the appropriate traits to exploit changing conditions (Smart et al, 2005)
The study species include: Senecio jacobaea, an herbaceous, winter annual or short-lived perennial that reproduces by seed and vegetatively (Bain, 1991); Cirsium arvense, a perennial herb that can reproduce sexually and regenerate vegetatively from roots (Tiley, 2010); Cirsium vulgare, a biennial or short-lived monocarpic herb, only spread by seeds; Rumex crispus, an annual to short-lived perennial herb that produces large numbers of seed which remain viable for many years and can regenerate from root fragments (Cavers and Harper, 1964; Grime, et al, 1988); Rumex obtusifolius, less ruderal than Rumex crispus, more robust and exclusively perennial; and Urtica dioica, a tall, usually dioecious, rhizomatous, perennial herb (Taylor, 2009)
Following the approach taken by the New Atlas of the British and Irish Flora (Telfer et al, 2002), we model the relationship between all plant species counts from the different Countryside Survey (CS) survey years, whilst accounting for recorder effort, and use the residuals from this model as an index of change
Summary
Human-induced environmental changes such as eutrophication, land use change, land intensification, disturbance or changes in the management regime may be facilitating the spread of species with the appropriate traits to exploit changing conditions (Smart et al, 2005) This could lead to dominance by aggressive competitive species (“thugs”; Marrs et al, 2011). Five native plant species pose a threat to plant species diversity and agricultural productivity and have been classified as “injurious weeds” under the Weeds Act 1959 (with an additional amendment for Ragwort in 2003) These are Common Ragwort (Senecio jacobaea), Spear Thistle (Cirsium vulgare), Creeping Thistle (Cirsium arvense), Broad-leaved Dock (Rumex obtusifolius) and Curled Dock (Rumex crispus). Land owners can be required through an enforcement notice to take all reasonable steps to prevent spread on their land and onto adjoining land; grazing areas or land which is used to produce conserved forage
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