Individual study: The effect of sulphur addition on the growth and survival of arable weeds and potted heather Calluna vulgaris plants, Craibstone, Aberdeenshire, Scotland
Lawson C.S., Ford M.A., Mitchley J. & Warren J.M. (2004) The establishment of heathland vegetation on ex-arable land: the response of Calluna vulgaris to soil acidification. Biological Conservation, 116, 409-416
Lowland heaths are a semi-natural habitat with high biodiversity conservation value. Conversion to arable farmland, reduction of grazing on remaining heaths (leading to succession to woodland), afforestation, and urbanisation have resulted in large scale loss of lowland heaths throughout Western Europe. Consequently, the re-establishment of lowland heathland is a priority within the UK Biodiversity Action Plan, with a 2005 target of creating 6,000 ha of heathland. The conversion of agricultural land back to heathland may help achieve this target. However, simply abandoning arable land usually results in species-poor habitat dominated by common, competetive perennial grasses, which thrive in the nutrient-rich soil. Former arable land is often unsuitable for heathland regeneration because of such high levels of soil nutrients, and also because of a high pH (due to agricultural liming), and the presence already of agressive ruderals and weeds. In this study, the relationship between soil acidification using sulphur, the development of ruderal vegetation, and the establishment of heather Calluna vulgaris (a dominant and desirable heathland species on arable soil is investigated.
Study area & heather cultivation: 4 cm high cuttings of heather Calluna vulgaris were taken from Brimmond Hill, Aberdeen (National Grid Reference NJ858091), northeast Scotland, during November 1995. These were planted in a 1:1 peat:sand mixture under mist (to maintain moiture levels) in a glasshouse. In December 1995, the rooted cuttings were transferred to peat-filled pots (78 mm diameter, 94 mm deep), and in May 1996 these were moved outside. In December 1995, arable soil was taken from the Craibstone Estate, Aberdeen (National Grid reference NJ877115) and transferred into 100 tubs (300 mm diameter, 225 mm deep) and stood outside at Craibstone. The soil was a sandy loam podzol derived from granitic till, with a pH of 5.4 and an organic matter content of 8%.
Treatments: In January 1996, sulphur (Thiovit: Pan Britannica Industries Ltd; 80% a.i.) was applied in water at 0, 0.15, 0.30, 0.45 and 0.60 kg/m² (= 0, 0.12, 0.24, 0.36 and 0.48 kg/m² sulphur). The pots were arranged in five randomised blocks, with four replicates of each of the five sulphur treatments per block. Fifteen weeks after sulphur application, arable weed cover was assessed by point quadrat for each plot. A single heather plant was then planted into each tub in June 1996.
Heather survival: The number of plants surviving was recorded at intervals of five weeks until 15 weeks after planting.
Weed cover: There was a significant negative relationship between percentage weed cover and the amount of sulphur applied (see Table 1, attached). Of the common weeds, the combined cover of pineapple mayweed Matricaria matricarioides and scentless mayweed Tripleurospermum inodorum declined from 26.8% in the control treatment to just 3.5% with the application of 0.48 kg/m² sulphur. In contrast, knotgrass Polygonum aviculare and common couch Elymus repens showed no effects.
Heather survival: After five weeks from the addition of heather plants, 27 of the 100 had died, 17 of which were in the 0.48 kg/m² sulphur treatment. By 10 weeks, 40 plants had died with only two remaining in each of the 0.36 and 0.48 kg/m² sulphur treatments. After 15 weeks, only one additional plant had died. In the control and 0.12 kg/m² sulphur treatment there were no deaths.
Conclusions: Heather grows poorly at high concentrations of sulphur due to excessive soil acidity. Lower concentrations, which also cause significant reduction in the percentage cover of competing weeds, might be the most optimal strategy for promoting heather growth. (See also Cases 357, 358 and 360).
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