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Differential responses of UK upland plants to nitrogen deposition

Published online by Cambridge University Press:  01 February 1999

IAN D. LEITH
Affiliation:
Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK
W. KEVIN HICKS
Affiliation:
Department of Plant and Soil Science, University of Aberdeen, St Machar Drive, Aberdeen AB24 3UU, UK Present address: Stockholm Environment Institute, Department of Biology, University York, York YO1 SYW, UK.
DAVID FOWLER
Affiliation:
Institute of Terrestrial Ecology, Bush Estate, Penicuik, Midlothian EH26 0QB, UK
SARAH J. WOODIN
Affiliation:
Department of Plant and Soil Science, University of Aberdeen, St Machar Drive, Aberdeen AB24 3UU, UK
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Abstract

Native upland species, Nardus stricta, Eriophorum vaginatum, Erica cinerea and Vaccinium vitis-idaea were given 3 or 60 kg N ha−1 yr−1, over 2 yr, applied as a mist (NH4NO3). The high N treatment increased above-ground biomass in all four species, but only significantly in E. cinerea, E. vaginatum and N. stricta. Biomass increases in E. vaginatum and N. stricta resulted from enhanced tiller production rather than shoot elongation. Root growth increased in N. stricta, so that root[ratio ]shoot ratio in this species was unchanged by N. Root growth in E. vaginatum, E. cinerea and V. vitis-idaea did not respond to N and their root[ratio ]shoot ratios decreased. Tissue N concentrations increased in both shoots and roots of all species in response to N. The accumulated foliar N did not increase the proportion of N allocated to Rubisco and the photosynthetic capacities of N. stricta, E. vaginatum and V. vitis-idaea were unchanged. Thus growth responses to N were due to altered allocation rather than increased rate of photosynthesis per unit leaf area. The high N treatment increased flower production significantly in E. cinerea but not in the other species. Although in this experiment dwarf shrubs were more responsive than graminoids to N, in the field at current N inputs the enhanced tillering of the graminoids may be more competitively advantageous, especially where gaps develop in the canopy. Thus increasing N deposition may lead to increased grassiness of upland heath, and in particular, a spread of N. stricta.

Type
Research Article
Copyright
Trustees of New Phytologist 1999

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