Contribution of different grass species to plant-atmosphere ammonia exchange in intensively managed grassland

M. Mattsson (1) , B. Herrmann (2) , S. Jones (2, 3) , A. Neftel (2) , M. A. Sutton (3) , J. K. Schjoerring (1)

1 Plant and Soil Science Laboratory
2 ART - Agroscope Reckenholz - Tänikon
3 CEH - Centre for Ecology and Hydrology

Species diversity in grasslands usually declines with increasing input of nitrogen from fertilizers or atmospheric nitrogen deposition. Conversely, species diversity may also impact the build-up of soil nitrogen pools. Limited information is available on how plant-atmosphere ammonia exchange is related to species diversity in grasslands. We have here investigated grass species abundance and different foliar nitrogen pools in 4-year-old intensively managed grassland. Apoplastic pH and NH₄⁺ concentrations of the 8 most abundant species were used to calculate stomatal NH₃ compensation points. Apoplastic NH₄⁺ concentrations differed considerably among the species, ranging from 13 to 117 ?M, with highest values in Festuca pratensis. Also apoplastic pH values varied, from pH 6.0 in Phleum pratense to 6.9 in Dactylis glomerata. The observed differences in apoplastic NH₄⁺ and pH resulted in a large span of predicted values for the stomatal NH₃ compensation point which ranged from 0.20 to 6.57 nmol mol^?1. Three species (Lolium perenne, Festuca pratensis and Dactylis glomerata) had sufficiently high NH₃ compensation points and abundance to contribute to the NH₃ emission of the whole field. At the same time, other grass species such as Phleum pratense and Lolium multiflorum had NH₃ compensation points below the atmospheric NH₃ concentration and could thus contribute to NH₃ uptake from the atmosphere. Evaluated across species, leaf bulk-tissue NH₄⁺ concentrations correlated well (r²=0.902) with stomatal NH₃ compensation points calculated on the basis of the apoplastic bioassay. This suggests that leaf tissue NH₄⁺ concentrations combined with data for the frequency distribution of the corresponding species can be used for predicting the NH₃ exchange potential of a mixed grass sward.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

M. Mattsson, B. Herrmann, S. Jones, A. Neftel, M. A. Sutton, et al.. Contribution of different grass species to plant-atmosphere ammonia exchange in intensively managed grassland. Biogeosciences Discussions, 2008, 5 (3), pp.2583-2605. ⟨hal-00298018⟩