Plant—atmosphere exchange of ammonia

The results of recent controlled environment and micrometeorological measurements of NH3 fluxes are presented to highlight the processes controlling NH3 plant-atmosphere exchange. The presence of NH+4 in leaf tissues results in the existence of an NH3 ‘compensation point’ concentration for substomatal tissues (xs), so that both emission and deposition are possible from stomata. In addition, NH3 may deposit efficiently on to leaf cuticles, short-circuiting any stomatal emission, so that a ‘canopy compensation point’ (Xc) may be defined that is smaller than Xs. Ammonia is generally deposited to nitrogen limited ecosystems, indicating a small Xs and small leaf cuticle resistance (Rw). In contrast, fluxes over croplands are typically bidirectional and may reflect a larger Xs as a consequence of greater N supply. The paper discusses the processes defining (humidity, acidic pollutants) and Xs (plant phenology, species, N nutrition) and proposes a new resistance approach, which integrates Xs and Rw into one model. Estimating long term bidirectional NH3 fluxes is still uncertain, though it is now possible to apply a single model concept to a range of ecosystem types and satisfactorily infer NH3 fluxes over diurnal time scales.

[1]  J. Moncrieff,et al.  Deposition of atmospheric ammonia to moorlands. , 1992, Environmental pollution.

[2]  J. Schjoerring,et al.  Field investigations of ammonia exchange between barley plants and the atmosphere. II. Nitrogen realiocation, free ammonium content and activities of ammonium‐assimilating enzymes in different leaves , 1993 .

[3]  L. Hove,et al.  The uptake of atmospheric ammonia by leaves. , 1988 .

[4]  J. Schjoerring,et al.  A computer-controlled system for studying ammonia exchange, photosynthesis and transpiration of plant canopies growing under controlled environmental conditions , 1995 .

[5]  R. Harrison,et al.  Land-surface exchange in a chemically-reactive system; surface fluxes of HNO3, HCl and NH3 , 1989 .

[6]  D. Fowler,et al.  The Exchange of Ammonia Between the Atmosphere and Plant Communities , 1993 .

[7]  H. V. Jaarsveld,et al.  A variable-resolution transport model applied for NHχ in Europe , 1992 .

[8]  Mark A. Sutton,et al.  Dry deposition of reduced nitrogen , 1994 .

[9]  J. Erisman,et al.  Continuous measurements of surface exchange of SO2 and NH3; Implications for their possible interaction in the deposition process , 1993 .

[10]  W. Parton,et al.  Ammonia Volatilization from Spring Wheat Plants , 1988 .

[11]  John N. Cape,et al.  Deposition of atmospheric pollutants on forests. , 1989 .

[12]  H. Rogers,et al.  Dry deposition of ammonia at environmental concentrations on selected plant species. , 1986, Journal of the Air Pollution Control Association.

[13]  O. T. Denmead,et al.  Micrometeorological methods for measuring gaseous losses of nitrogen in the field , 1983 .

[14]  J. Freney,et al.  A closed ammonia cycle within a plant canopy , 1976 .

[15]  D. Bouldin,et al.  Apparent deposition velocity and compensation point of ammonia inferred from gradient measurements above and through alfalfa , 1990 .

[16]  Mark A. Sutton,et al.  The exchange of atmospheric ammonia with vegetated surfaces. II: Fertilized vegetation , 1993 .

[17]  J. Schjoerring.  Long-term quantification of ammonia exchange between agricultural cropland and the atmosphere—I. Evaluation of a new method based on passive flux samplers in gradient configuration , 1995 .

[18]  W. H. Benner,et al.  Oxidation of SO2 in thin water films containing NH3 , 1992 .

[19]  D. Schimel,et al.  Gaseous ammonia fluxes and background concentrations in terrestrial ecosystems of the United States , 1992 .

[20]  P. Jarvis,et al.  Transpiration and evaporation from heather Moorland , 1984 .

[21]  W. J. Vredenberg,et al.  A study of the adsorption of NH3 and SO2 on leaf surfaces , 1989 .

[22]  G. Draaijers.  The variability of atmospheric deposition to forests : the effects of canopy structure and forest edges , 1993 .

[23]  K. Joy.  Ammonia, glutamine, and asparagine: a carbon–nitrogen interface , 1988 .

[24]  O. Lewis,et al.  The influence of nitrate and ammonium nutrition on the growth of wheat (Triticum aestivum) and maize (Zea mays) plants , 1993 .

[25]  J. Raven.  Acquisition of nitrogen by the shoots of land plants: its occurrence and implications for acid-base regulation , 1988 .

[26]  C. Place,et al.  Modelling the net exchange of reduced nitrogen , 1993 .

[27]  B. Hoffmann,et al.  Measurements of pH in the apoplast of sunflower leaves by means of fluorescence , 1992 .

[28]  P. A. Burrough,et al.  Soil acidification from atmospheric ammonium sulphate in forest canopy throughfall , 1982, Nature.

[29]  K. Dietz,et al.  A Fluorescence Method for the Determination of the Apoplastic Proton Concentration in Intact Leaf tissues , 1987 .

[30]  Sutton,et al.  Mapping and modelling of critical loads for nitrogen - a workshop report. , 1995 .

[31]  W. Parton,et al.  Characteristics of Ammonia Volatilization from Spring Wheat , 1989 .

[32]  D. Fowler,et al.  Micrometeorological techniques for the measurements of trace gas exchange , 1989 .

[33]  G. L. Hutchinson,et al.  Atmospheric Ammonia: Absorption by Plant Leaves , 1972, Science.

[34]  G. P. Wyers,et al.  A continuous-flow denuder for the measurement of ambient concentrations and surface-exchange fluxes of ammonia , 1993 .

[35]  J. Burkhardt,et al.  Thin water films on coniferous needles: A new device for the study of water vapour condensation and gaseous deposition to plant surfaces and particle samples , 1994 .

[36]  Ammonia volatilization from agricultural land. , 1990 .

[37]  J. Duyzer,et al.  The dry deposition of ammonia onto a Douglas fir forest in the Netherlands , 1994 .

[38]  G. Farquhar,et al.  On the Gaseous Exchange of Ammonia between Leaves and the Environment: Determination of the Ammonia Compensation Point. , 1980, Plant physiology.

[39]  Jan K. Schjoerring,et al.  Field investigations of ammonia exchange between barley plants and the atmosphere. I. Concentration profiles and flux densities of ammonia , 1993 .