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The Role of Mineral Nutrients in Eriophorum Communities: IV. Potassium Supply as a Limiting Factor in an E. Vaginatum Community
Gordon T. Goodman and Donald F. Perkins
Journal of Ecology
Vol. 56, No. 3 (Nov., 1968), pp. 685-696
Published by: British Ecological Society
Stable URL: http://www.jstor.org/stable/2258100
Page Count: 12
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Powdered salts of potassium, phosphorus, nitrogen, calcium and magnesium were added separately and all together at low, medium and high rates of application to an intact sward of Eriophorum vaginatum L. growing at 610 m O.D. in Breconshire U.K., in August 1958. Chemical analyses of leaf material from the treated plots, 4 and 12 weeks after salt application, confirmed that the added nutrients had been taken up by the leaves, but also showed that P, N and, particularly K often increased in leaf material from plots where these elements had not been added. By 30 weeks after salt addition, nutrient levels in leaf material and underlying peat had returned to normal. A subsequent set of high treatments, set up in August 1959 to follow leaf nutrient changes over the first 8 weeks after salt application, confirmed this result and also showed significant increases in leaf Ca and Mg on plots where these elements had not been added. The increases recorded for all elements were beginning to fall off 8 weeks after salt addition. An attempt to correlate the growth responses which had occurred on these plots 1 and 2 years after salt application (Goodman & Perkins 1968) with the leaf nutrient increases, indicated that a rise in leaf potassium was most consistently associated with improved growth. It is concluded that potassium is the primary limiting element at this site and also on a raised bog at 157 m O.D. near Tregaron, Cardiganshire, U.K. where a very similar pattern of growth responses with added macronutrients was obtained. Tamm (1954) obtained a striking growth response in E. vaginatum to added P at Morhults Mosse, Sweden. The available leaf analyses point to a very low P status on the Swedish site and the question is how differences in P and K status arise and are maintained. It is suggested that the size and turnover of the local invertebrate biomass may possibly be important as a reservoir of readily available P. The importance of K loss by rainwater leaching from living leaves, particularly under very high rainfall, is also noted.
Journal of Ecology © 1968 British Ecological Society