Untersuchung der Wurzel-Boden Grenzfläche im Unterboden mit Hilfe der Röntgenstrahl Computertomographie und Endoskopie

Transportprozesse von Luft, Wasser und gelösten Stoffen haben erheblichen Einfluss in Hinblick auf die Erzeugung von Kulturpflanzen. Diese Transportprozesse wiederum, stehen in Abhängigkeit zu der Struktur des Bodens. Besonders für den Unterboden stellen Bioporen eine Möglichkeit als Wurzel-Boden Grenzfläche dar, die erheblich durch die Aktivität von Flora und Fauna beeinflusst wird. Mit X-ray CT, Bildauswertung und Endoskopie wurden mit Regenwürmern besetzte Bodensäulen untersucht. Es wurde der Frage nachgegangen, welchen Einfluss die Aktivität von Wurzeln und Regenwürmern auf die Wurzel-Boden Grenzfläche hat und inwiefern Eigenschaften und Charakteristik von Bioporen verändert werden. Es hat sich gezeigt, dass die vorhandenen Strukturen eines etablierten Biopore-Netzwerkes in hohem Maße wiederverwendet und somit in ihrer Struktur verändert wurden

A new model for root growth in soil with macropores

Abstract: Background and aimsThe use of standard dynamic root architecture models to simulate root growth in soil containing macropores failed to reproduce experimentally observed root growth patterns. We thus developed a new, more mechanistic model approach for the simulation of root growth in structured soil. Methods: In our alternative modelling approach, we distinguish between, firstly, the driving force for root growth, which is determined by the orientation of the previous root segment and the influence of gravitropism and, secondly, soil mechanical resistance to root growth. The latter is expressed by its inverse, soil mechanical conductance, and treated similarly to hydraulic conductivity in Darcy’s law. At the presence of macropores, soil mechanical conductance is anisotropic, which leads to a difference between the direction of the driving force and the direction of the root tip movement. Results: The model was tested using data from the literature, at pot scale, at macropore scale, and in a series of simulations where sensitivity to gravity and macropore orientation was evaluated. Conclusions: Qualitative and quantitative comparisons between simulated and experimentally observed root systems showed good agreement, suggesting that the drawn analogy between soil water flow and root growth is a useful one

Spatial variability of hydrolytic and oxidative potential enzyme activities in different subsoil compartments.

© 2015 Springer-Verlag Berlin Heidelberg The spatial heterogeneity of nutrient turnover in subsoils has been rarely studied in the past, although drilosphere and rhizosphere are found to be important microbial hotspots in this oligotrophic environment. In this study, we measured different potential enzyme activities in different soil compartments of subsoil and topsoil. It could be shown that the activities of hydrolases, which cleave readily available organic substrates, are significantly higher in samples from the drilosphere and rhizosphere both in topsoil and subsoil. In bulk soil, hydrolase activities decrease with depth. In contrast, oxidative enzymes, which are involved in the decay of recalcitrant organic material, are released from the microbial community especially in the bulk fraction of subsoil. This emphasizes the importance of subsoil for nutrient acquisition and gives evidence for a distinct spatial separation of microbes with diverging lifestyles

Bacteria utilising plant-derived carbon in the rhizosphere of <em>Triticum aestivum</em> change in different depths of an arable soil.

Root exudates shape microbial communities at the plant soil interface. Here we compared bacterial communities that utilise plant-derived carbon in the rhizosphere of wheat in different soil depths, including topsoil, as well as two subsoil layers up to 1 m depth. The experiment was performed in a green house using soil monoliths with intact soil structure taken from an agricultural field. To identify bacteria utilizing plant derived carbon, (13) C-CO2 labelling of plants was performed for two weeks at the EC50 stage, followed by stable isotope probing of extracted DNA from the rhizosphere combined with 16S rRNA gene-based amplicon sequencing. Our findings suggest substantially different bacterial key players and interaction mechanisms between plants and bacteria utilising plant-derived carbon in the rhizosphere of subsoils and topsoil. Among the three soil depths, clear differences were found in (13) C enrichment pattern across abundant operational taxonomic units (OTUs). Whereas OTUs linked to Proteobacteria were enriched in (13) C mainly in the topsoil, in both subsoil layers OTUs related to Cohnella, Paenibacillus, Flavobacterium showed a clear (13) C signal, indicating an important, so far overseen role of Firmicutes and Bacteriodetes in the subsoil rhizosphere