TY - THES

T1 - Gross nitrification in soils

T2 - contribution of nitrification to N-gas emission from soils

AU - Stange, Claus Florian

PY - 2023

Y1 - 2023

N2 - This work contributes to developing a better understanding of nitrification in soils as an important source of N gas emissions from soils. Therefore, the nitrification process as well as N gas produced by nitrification are considered. The work described the common methods and new developed approach for determining the gross nitrification rate. Both measuring and quantifying nitrification in soils have been shown to achieve the objective. One focus is to differentiate the sources of N gases and to quantify the contribution of nitrification to N gas emission from soils. The separation of N gas production into source-related pathways that simultaneously operate in soils requires comprehensive experiments with complex analyses. Therefore a new analytical approach and calculates the fractions of ammonia oxidation, Norg oxidation and denitrification for total soil NO and N2O released from a soil probes at different oxygen states (2.5, 1.2 and 0 % O2) is presented and tested for a five loamy Spanish forest soils. Whereas the relation between ammonia oxidation and denitrification as sources of soil N2O gas release appear to be consistent, which is commonly accepted, the contribution of Norg oxidation was unexpectedly high (up to 76%). Also two model approaches to model the N-gas production in soils are parametrised on experimental data from laboratory studies. The findings are discussed in view of choosing the best approach to predict N2O production during nitrification. and an approach to combine response functions in modelling is presented and tested on field data. The advantage against the conventional combining approaches (multiplicative or min/max approaches) is discussed. N2O production data related to nitrification and nitrification rates were collected and multiple linear regression analysis between the soil properties and N2O product ratios were applied to this dataset to identify functional relationships. Future works to support the development of sufficient model approaches are needed, and in particular, the nitrite and oxygen concentrations in soils are the most important factors for N2O production.

AB - This work contributes to developing a better understanding of nitrification in soils as an important source of N gas emissions from soils. Therefore, the nitrification process as well as N gas produced by nitrification are considered. The work described the common methods and new developed approach for determining the gross nitrification rate. Both measuring and quantifying nitrification in soils have been shown to achieve the objective. One focus is to differentiate the sources of N gases and to quantify the contribution of nitrification to N gas emission from soils. The separation of N gas production into source-related pathways that simultaneously operate in soils requires comprehensive experiments with complex analyses. Therefore a new analytical approach and calculates the fractions of ammonia oxidation, Norg oxidation and denitrification for total soil NO and N2O released from a soil probes at different oxygen states (2.5, 1.2 and 0 % O2) is presented and tested for a five loamy Spanish forest soils. Whereas the relation between ammonia oxidation and denitrification as sources of soil N2O gas release appear to be consistent, which is commonly accepted, the contribution of Norg oxidation was unexpectedly high (up to 76%). Also two model approaches to model the N-gas production in soils are parametrised on experimental data from laboratory studies. The findings are discussed in view of choosing the best approach to predict N2O production during nitrification. and an approach to combine response functions in modelling is presented and tested on field data. The advantage against the conventional combining approaches (multiplicative or min/max approaches) is discussed. N2O production data related to nitrification and nitrification rates were collected and multiple linear regression analysis between the soil properties and N2O product ratios were applied to this dataset to identify functional relationships. Future works to support the development of sufficient model approaches are needed, and in particular, the nitrite and oxygen concentrations in soils are the most important factors for N2O production.

U2 - 10.15488/15127

DO - 10.15488/15127

M3 - Habilitation treatise

CY - Hannover

ER -