Recent developments in labelling and data analysis approaches for 15N tracing experiments

• The microbial mediated soil nitrogen (N) cycle is often investigated using stable isotope (15N) labelling. The main objective of these studies is to quantify gross rates of simultaneously occurring N transformations. In this paper we will give an overview on recent progress in 15N tracing methodologies, including both in-situ 15N label application as well as data analysis. In most studies investigating gross N transformations, soils are disturbed before incubation, leading to alteration of soil properties compared to field conditions. In-situ studies typically disrupt the soil-rootmycorrhiza system by inserting cylinders into the soil. A novel in-situ 15N labelling approach, coined ‘Virtual Soil Core’[1], was developed in order to allow the soil properties as well as the plant root and mycorrhizal activity to remain unaltered during the course of the 15N experiment. Most investigations have used analytical 15N tracing models[2] for data analysis, which though allow only the quantification of total production and consumption rates[3, 4]. To achieve a process based quantification of simultaneously occurring N transformation rates, numerical 15N tracing models are required. Recent progress in these models, by implementing Monte Carlo methods[5], overcome the limitations of earlier models, which restricted the number of considered transformations as well as the chosen kinetics. In summary, using case studies in different ecosystems, we show that 15N labelling techniques in combination with robust data analysis tools provide us with a deeper insight in N cycling processes. Therefore, 15N tracing techniques are an essential tool to increase our understanding of the soil N cycling.

Ämnesord

LANTBRUKSVETENSKAPER  -- Lantbruksvetenskap, skogsbruk och fiske -- Markvetenskap (hsv//swe)

AGRICULTURAL SCIENCES  -- Agriculture, Forestry and Fisheries -- Soil Science (hsv//eng)

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