Effect of NH₄-fertilization on the maintenance of aCalluna vulgarisvegetation

Abstract

NH 4-fertilization in a natural, undamaged Calluna vegetation did not result in an immediate replacement of Calluna vulgaris by grasses. However, obvious changes were found in plant and soil composition that may lead to a greater stress sensitivity, but also to a lower regeneration capacity and a lower growth of C. vulgaris. Vegetative expansion of Molinia caerulea and Deschampsiaflexuosa was higher in a Calluna vegetation damaged by a severe frost in the winter of 1986/1987 compared to growth in undamaged plots. The higher stress sensitivity of C. vulgaris due to nitrogen deposition may accelerate opening of the vegetation canopy. Once the vegetation has been opened, the negative effects of the high nitrogen input by the lower regeneration capacity and lower plant growth may speed up even more the transition of heathland into grassland.

The effect of increased deposition of atmospheric nitrogen on Calluna vulgaris in upland Britain

“…However, a number of studies on Dutch heathlands characterized by very high rates of atmospheric nitrogen supply have shown no clear stimulation of growth in response to nitrogen addition in C. vulgaris or a number of other ericaceous plants (Aerts & Berendse, 1988 ;Prins et al, 1991). These results were associated with clear accumulations of nitrogen in the shoots of the plants, and also with very high tissue N : P ratios.…”

“…There is some evidence that these changes could in turn increase the susceptibility of the vegetation to a range of environmental stresses such as frost, drought and herbivory (Green et al, 1997). Changes in the structure of heathland vegetation in areas of The Netherlands exposed to high levels of deposition of atmospheric nitrogen over several decades have been particularly marked, with a clear pattern of canopy breakdown resulting from increased herbivory or drought damage (Berdowski & Zeilinga, 1987 ;Prins et al, 1991), followed by the invasion of grass species. Most heathland studies have, however, concentrated on the effects of nitrogen inputs on lowland heaths (Uren et al, 1997).…”

Ecological impacts of arable intensification in Europe

“…Deposition of atmospheric nitrogen can lead to eutrophication and acidification of semi-natural environments, resulting in reduction in botanical species diversity and changes to soil processes, as demonstrated at Rothamsted (UK) by Goulding et al (1998). Similar changes in soil processes and botanical composition resulting from atmospheric nitrogen deposition have been reported in British upland heath and calcareous grassland (Lee and Capron, 1998), and in heathland in The Netherlands (Prins et al, 1991).…”

Incorporation of 15 N from spiked cattle dung pats into soil under two moorland plant communities

“…4 Conversely Calluna has been shown to either compete weakly with grasses for nutrients 4,33 or even show negative responses to higher nutrient availability. [33][34][35] The slower incorporation of dung into heather soil reflects the slower nutrient uptake and shallower root system in Calluna.…”