Abstract
SummaryThe abundance of Juncus effusus (soft rush) and Juncus conglomeratus (compact rush) has increased in coastal grasslands in Norway over recent decades, and their spread has coincided with increased precipitation in the region. Especially in water‐saturated, peaty soils, it appears from field observations that productive grasses cannot compete effectively with such rapidly growing rush plants. In autumn–winters of 2012–2013 and 2013–2014, a four‐factor, randomised block greenhouse experiment was performed to investigate the effect of different soil moisture regimes and organic matter contents on competition between these rush species and smooth meadow‐grass (Poa pratensis). The rush species were grown in monoculture and in competition with the meadow‐grass, using the equivalent of full and half the recommended seed rate for the latter. After about three months, above‐ and below‐ground dry matter was measured. J. effusus had more vigorous growth, producing on average 23–40% greater biomass in both fractions than J. conglomeratus. The competitive ability of both rush species declined with decreasing soil moisture; at the lowest levels of soil moisture, growth reductions were up to 93% in J. conglomeratus and 74% in J. effusus. Increasing water level in peat–sand mixture decreased competivitiveness of meadow‐grass, while pure peat, when moist, completely impeded its below‐ground development. These results show that control of rush plants through management may only be achieved if basic soil limitations have been resolved.
Highlights
Increases in Juncus effusus L. and Juncus conglomeratus L., which are perennial weed species that are detrimental to forage production, have been observed, not yet documented, on coastal grassland in western Norway over the last two decades
J. effusus had more vigorous growth, producing on average 23–40% greater biomass in both fractions than J. conglomeratus
The competitive ability of both rush species declined with decreasing soil moisture; at the lowest levels of soil moisture, growth reductions were up to 93% in J. conglomeratus and 74% in J. effusus
Summary
Increases in Juncus effusus L. (soft rush) and Juncus conglomeratus L. (compact rush), which are perennial weed species that are detrimental to forage production, have been observed, not yet documented, on coastal grassland in western Norway over the last two decades. (compact rush), which are perennial weed species that are detrimental to forage production, have been observed, not yet documented, on coastal grassland in western Norway over the last two decades. 491 and mown once or twice per year Such increasing patches of rushes reduce grazing areas (Cherrill, 1995). Considerable rush infestation has occurred throughout the UK, where rushes have become persistent weeds on managed grassland (Merchant, 1995), as well as in Ireland, where J. effusus is of greatest significance on pasture areas (O’Reilly, 2012) and cutaway bogs (McCORRY & RENOU, 2003). Rush species are able to establish on a broad range of soils, but most frequently on shallow peat (Richards & Clapham, 1941; KORSMO, 1954), where they can grow in a high range of pH values to as low as pH 3.5, but are less common above pH 7 (McCORRY & RENOU, 2003). A temporarily saturated soil with high organic matter content and low pH is a common factor in rush establishment (Tansley, 1949; Lazenby, 1955)
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