Elevated nitrogen (N) deposition, one of the most important problems on global changes, has shown to have a variety of effects on terrestrial systems in temperate Europe and North American. Currently, many results about the reactions of ecosystem to N deposition, including biodiversity, primary productivity, nutrient cycling, N transformation and leaching, emission of greenhouse gases (CO2, CH4 and NO2), soil and water acidification, and even forests degradation have been reported. However, since most of the deposited N finally enters soil, therefore it is necessary to study the belowground response of soil fauna to N deposition. 

The responses of Collembola to long-term N deposition were studied by Drs. XU Guoliang and FU Shenglei, members of the Restoration Ecology Group of South China Botanical Garden (SCBG) and their cooperators Drs. Patrick Schleppi and LI Maihe. This study was conducted at Alptal, Switzerland in 2007, in the 13th year of experimental N addition. It is one of the sites of the European project NITREX, where two sub-catchments (approx 1500 m²) were delimited within the forest, one as a control and the other subjected to an increased deposition of 25 kg N ha-¹ year-¹as NH4NO3 added to rain water and sprinkled over the ground vegetation and the soil. In 0-15 cm soil layer, it showed a clear tendency of reduction of Collembola community in N-treated plots than in control plots. Not only density, but also group richness and diversity of Collembola are lower in N-treated plots than in control plots. The negative effects are even more efficient in 0-5 cm depth. For example, the density of Isotomiella minor was reduced significantly by 80% in N-treated plots (17000 ind m-³) in 0-5 cm soil layer compared with control plots (85600 ind m-³). It was also found that Shannon-Wiener index (H') showed less differences between the N-treated plots and the control plots than Density-Group index (dDG).

Thereby, the Collembola community could be considered as bioindicator of N inputs exceeding the biological needs, namely of soil N saturation; the reduction of Collembola under N treatment would depress decomposition process but increase the storage of soil organic C. All of the results have been published in Environmental Pollutiion.