PLANT-DISTRIBUTION IN RELATION TO MINERAL NUTRIENT AVAILABILITY AND UPTAKE ON A WET-HEATH SITE IN SOUTH-WEST ENGLAND

Chemical analyses of peat samples from wet-heath vegetation at Aylesbeare Common, Devon, show trends significant at the 1% level in 3rd order trend-surfaces for pH and extractable Ca, Mg, K, Mn, P and NH4-N. The major vegetation contrast between species-poor wet heath and acid Sphagnum carpet communities on the one hand, and species-rich wet heath and Molinietum on the other, correlates closely with the distribution of Ca, Mg and pH. Molinia performs best in areas with higher pH, Ca, Mg and K, and where there is active water movement. Leaf (or green shoot) material of Molinia caerulea, Ulex gallii, Trichophorum cespitosum, Eriophorum angustifolium, Narthecium ossifragum, Cirsium dissectum, Succisa pratensis and Serratula tinctoria was analysed for nutrients. In mean percentage chemical composition, Cirsium, Succisa and Serratula are relatively high in Ca, Mg and K; Cirsium and Succisa in Mn; Molinia and (especially) Ulex in N; and Ulex, Cirsium, Succisa and Serratula in P. Narthecium contains higher levels of most elements than the other monocotyledons. The concentration of an element in a plant species is best predicted by the concentration of the same element in the peat in only a few instances. More commonly uptake of one element is most strongly related to the concentration of another element in the peat. Thus K in Trichophorum and Succisa is positively correlated with peat Ca; Ulex Mg and K, and Cirsium Mg and Na, are negatively correlated with peat Ca. The pattern of uptake for every species and every element is different. This could be taken as evidence of niche differentiation between species in relation to nutrient uptake, and may be a factor in their stable coexistence. -from Authors