Effects of nitrogen addition on the stress sensitivity of Calluna vulgaris

• Published in: The New phytologist 1998-04, Vol.138 (4), p.663-673
• Main Authors: POWER, S. A., ASHMORE, M. R., COUSINS, D. A., SHEPPARD, L. J.
• Format: Article
• Language: English
• Subjects: Animal, plant and microbial ecology; application rate; Applied ecology; Beetles; Biological and medical sciences; buds; Calluna vulgaris; Calluna vulgaris (L.) Hull; defoliation; drought; drought stress; drought tolerance; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on plants and fungi; electrolytes; Frost; Frost damage; frost hardiness; frost resistance; Fundamental and applied biological sciences. Psychology; growth rate; heather beetles; Heathlands; Insect larvae; larvae; Larval development; lochmaea suturalis; losses; mortality; Nitrogen; nitrogen deposition; Phytophagous insects; plant physiology; Plants; sexual reproduction; shoots; stress; water; Water loss; xylem water potential
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1046/j.1469-8137.1998.00160.x

The effects of low levels of nitrogen addition (7·7 and 15·4 kg N ha−1 yr−1) on plant sensitivity to biotic and abiotic stress were studied at a lowland heath in the south of England that has received N treatments since 1989. Larval growth rates and adult weights of heather beetles were found to be significantly higher when insects were reared on plants that had received additional N, with implications for insect survival and reproductive success. Electrolyte leakage measurements failed to reveal any significant impact of N addition on plant sensitivity to frost episodes in early winter. In April, however, there was some evidence of slightly decreased frost hardiness in plants receiving additional N. Accelerated spring bud burst also suggested earlier physiological activity in N-treated plots. The rate of water loss from excised shoots of Calluna vulgaris (L.) Hull was significantly faster in plants receiving additional N, although no difference in plant water potential was measured in the field after a prolonged dry spell. Whilst experimental N addition had only a small effect on plant sensitivity to abiotic stress, the relationship between enhanced deposition and increased insect performance was clear, with the potential for substantially increased insect damage at deposition rates around the critical load contributing to the formation of gaps in the Calluna canopy.