Differential responses of UK upland plants to nitrogen deposition

Abstract

Native upland species, Nardus stricta, Eriophorum vaginatum, Erica cinerea and Vaccinium vitis-idaea were given 3 or 60 kg N ha −" yr −" , over 2 yr, applied as a mist (NH % NO $ ). 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 : 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 : 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. vitisidaea 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.

Responses of wetland graminoids to the relative supply of nitrogen and phosphorus

“…In experiment 1 of this study, the RMR of C. elata decreased less with increasing N:P supply ratio than that of C. curta and C. flava, yet their biomass responded similarly. The RMR can also respond differently to N supply according to the growth medium, amount and form of N used ͑Crabtree and Bazzaz 1993; Leith et al 1999͒. In conclusion, none of the simple control mechanisms suggested in Figure 1 seems to apply generally for the RMR.…”

The Role of Plants in the Effects of Global Change on Nutrient Availability and Stoichiometry in the Plant-Soil System

“…Species with traits that enable better adaptation to P limitation are thus favored (Leith et al, 1999;Fujita et al, 2010;Blanes et al, 2012 (Stevens et al, 2006;Sparrius et al, 2012). A recent review provides some evidence that the efficiency of carbon use by soil microbes increases with N deposition (Manzoni et al, 2012), suggesting that soil mineralization increases and microbes improve their uptake of nutrients, which, in turn, would increase the competition for nutrients between microbes and plants.…”

“…This increase in the plant N-P ratio further limits plant growth (Güsewell, 2005;Granath et al, 2012) and photosynthetic rates (Güsewell, 2005). Another frequent effect accompanying N deposition is an increase of root growth (Brunner and Godbold, 2007), but some studies have observed a reduction in root growth (Gundersen et al, 1998;Nadelhoffer 2000) and increases in fine-root turnover (Nadelhoffer 2000) and very frequently a lower rootshoot ratio (Leith et al, 1999).…”

Modeling the effects of nitrogen deposition on carbon budget in two temperate forests

“…Increased availability of fixed N to plants may lead to increased photosynthetic rates due to strong correlations between foliar N concentration and photosynthetic rates (Field and Mooney, 1986;Reich et al, 1998;Peterson et al, 1999). Simulated deposition studies at both the leaf and stand levels have revealed increases in photosynthesis or enhanced aboveground production (Aber et al, 1993;Leith et al, 1999), and enhanced primary production lead to increased terrestrial C storage (Schindler and Bayley, 1993;Thornley and Cannell, 1996;Townsend et al, 1996;Holland et al, 1997). Much research efforts have focused on NPP and C sequestration responses to N deposition (Peterson and Melillo, 1985;Schindler and Bayley, 1993;Hudson et al, 1994;Townsend et al, 1996;Holland et al, 1997).…”