Soil and Temperature Influence on Microbiological Nitrogen Transformations : A microcosm study by dynamic 15N dilution technique

Göttingen

1998

131 S.

Bandaufführung

59176

This study is intended to be a contribution to some still open questions concerning the role of nitrogen in forest ecosystems. One major question which it addresses is the fate of nitrogen input in cationic and anionic form (NH4+-N and NO3hoch-N) in soil microbiological transformation processes. The study of these pathways by employment of stable isotope tracers (15N). Another scope of the investigations are the differences of microbial communities and activities in relation to temperature, soil type, acidity and soil depth. As the central goal of the study is to obtain an improved parameterization for N cycling models in forest soils under field conditions, the research in this work is interconnected with two other studies, one using intact cores incubation in situ with and without root uptake (Raubuch & Meyer, 1996), and the other concentrating on soil micro-, meso-, and macrofauna in microcosms as well as in situ (Wolters, 1996). To make such parameter estimates as realistic as possible, we used a methodolgy as "realistic" as possible, i.w., the incubation of undisturbed soil columns in a micrososm system to conserves the soil structure and the soil biota. For this approach, the methodology is a combination of the continuous flow incubation technique originated from Macura & Malek (1958) and the 15N dynamic dilution technique of Brumme (1986). The continuous flow incubation was further improved by Standford & Smith (1972), it combines a continuous removal of nutrients like by plant roots or natural leaching (Erh et al., 1967) with the possibility of a repeatable measurement of N transformationrates using an undisturbed system. From this comination arose the necessity to improve the methology of 15N-analysis which consequently occupies ample space in chapter 2 and 4. Because of the complicated interactions of processes and factors, and as the results of the prallel studies and other investigations had to be considered in direct conjunction with own results, it was considered opertune to split up the discussion and to incorporate the session into the chapter Results and Discussions (3).