Calculating gross N transformation rates of 15N pool dilution experiments with acid forest litter: Analytical and numerical approaches

• Published in: Soil biology & biochemistry 1992, Vol.24 (10), p.931-942
• Main Authors: Wessel, Wim W., Tietema, Albert
• Format: Article
• Language: English
• Subjects: acidity; Agronomy. Soil science and plant productions; biogeochemical cycles; Biological and medical sciences; calculation; Chemical, physicochemical, biochemical and biological properties; coniferous forests; deciduous forests; errors; estimation; forest litter; Fundamental and applied biological sciences. Psychology; immobilization; mineralization; nitrification; nitrogen; Organic matter; Physics, chemistry, biochemistry and biology of agricultural and forest soils; recycling; Soil science; transformation
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/0038-0717(92)90020-X

Gross N transformation rates were determined with 15NH 4 + and 15NO 3 − pool dilution experiments in acid litter of a deciduous and a coniferous forest in The Netherlands. Although gross mineralization and NH 4 + immobilization rates were comparable in the two litter layers, gross nitrification and NO 3 − immobilization rates were much lower in the deciduous litter. Gross rates were calculated with different models solved either analytically or numerically. The numerically solved model allowing for recycling of 15N back to the enriched pool was considered superior. Recycling of 15N was significant in the 15NH 4 + enrichment experiments. Error analysis with help of the analytical solutions showed that an inherently high error existed in the results due to the sensitivity of the method to errors in the measured variables. The heterogeneity of the samples was the main source of errors in these variables. The design of the method determines the sensitivity for measurement errors. To minimize the sensitivity the duration of the experiment should be maximized and the 15N abundance of the enriched N pool should be several times the natural 15N abundance. Application of 15N above this level does not contribute to the accuracy of the estimations.