Dynamics of ammonia exchange with cut grassland: strategy and implementation of the GRAMINAE Integrated Experiment

摘要

A major international experiment on ammonia (NH₃)biosphere-atmosphere exchange was conducted over intensively managedgrassland at Braunschweig, Germany. The experimental strategy was developedto allow an integrated analysis of different features of NH₃ exchangeincluding: a) quantification of nearby emissions and advection effects, b)estimation of net NH₃ fluxes with the canopy by a range ofmicrometeorological measurements, c) analysis of the sources and sinks ofNH₃ within the plant canopy, including soils and bioassay measurements,d) comparison of the effects of grassland management options on NH₃fluxes and e) assessment of the interactions of NH₃ fluxes with aerosolexchange processes. Additional technical objectives included theinter-comparison of different estimates of sensible and latent heat fluxes,as well as continuous-gradient and Relaxed Eddy Accumulation (REA) systemsfor NH₃ fluxes.The prior analysis established the spatial and temporal design of theexperiment, allowing significant synergy between these objectives. Themeasurements were made at 7 measurement locations, thereby quantifyinghorizontal and vertical profiles, and covered three phases: a) tall grasscanopy prior to cutting (7 days), b) short grass after cutting (7 days) andc) re-growing sward following fertilization with ammonium nitrate (10 days).The sequential management treatments allowed comparison of sources-sinks,advection and aerosol interactions under a wide range of NH₃ fluxes.This paper describes the experimental strategy and reports the grasslandmanagement history, soils, environmental conditions and air chemistry duringthe experiment, finally summarizing how the results are coordinated in theaccompanying series of papers.