Relations between Soil Nutrients and Vegetation in Wet-Heaths: I. Soil Nutrient Content and Moisture Conditions

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Abstract
The nutrient content of soils from 3 adjacent and closely related plant communities in Bramshill Forest, north-east Hampshire, was determined. Molinia caerulea, Calluna vulgaris and Erica tetralix were the major species present in all the 3 sites, but their relative proportions varied considerably. Molinia was most abundant in the site with richest nutrient supply and greatest water-table depth and fluctuation. Soil analyses nevertheless suggested that the Molinietum topsoil was phosphorus [P] deficient in comparison with many other soils. Nutrients were concentrated in the surface horizons of the Molinietum, a feature which may result from the activity of the deep rooted Molinia plant itself, Molinia tussocks had total nitrogen [N] and P contents 8-10 times greater than that held in the standing crop in August, but exchangeable potassium [K] was only 1/2 of the K content of the crop. The valley bog site had a permanently high water table and was markedly nutrient deficient, particularly in phosphorus. Its surface peat was similar in nutrient content to ombrogenous peats of northern England. In these conditions, Sphagnum spp. and Erica tetralix increased in prominence. The central associes site had a water table at a depth intermediate between the other 2 sites. Its topsoil had a very high C/N ratio indicating a slow release of soluble nitrogen and it was also P deficient. All 3 species were well represented in this site. Tree growth was greatest in the most nutrient rich site (the Molinietum) and least in the most nutrient deficient (the valley bog).