University of Hohenheim

About: University of Hohenheim is a education organization based out in Stuttgart, Germany. It is known for research contribution in the topics: Population & Soil water. The organization has 8585 authors who have published 16406 publications receiving 567377 citations.

Soil-carbon preservation through habitat constraints and biological limitations on decomposer activity

Abstract: We review recent experimental results on the role of soil biota in stabilizing or destabilizing soil organic matter (SOM). Specifically, we analyze how the differential substrate utilization of the various decomposer organisms contributes to a decorrelation of chemical stability, residence time, and carbon (C) age of organic substrates. Along soil depth profiles, a mismatch of C allocation and abundance of decomposer organisms is consistently observed, revealing that a relevant proportion of soil C is not subjected to efficient decomposition. Results from recent field and laboratory experiments suggest that (1) bacterial utilization of labile carbon compounds is limited by short-distance transport processes and, therefore, can take place deep in the soil under conditions of effective local diffusion or convection. In contrast, (2) fungal utilization of phenolic substrates, including lignin, appears to be restricted to the upper soil layer due to the requirement for oxygen of the enzymatic reaction involved. (3) Carbon of any age is utilized by soil microorganisms, and microbial C is recycled in the microbial food web. Due to stoichiometric requirements of their metabolism, (4) soil animals tend to reduce the C concentration of SOM disproportionally, until it reaches a threshold level. The reviewed investigations provide new and quantitative evidence that different soil C pools underlie divergent biological constraints of decomposition. The specialization of decomposers towards different substrates and microhabitats leads to a relatively longer persistence of virtually all kinds of organic substrates in the nonpreferred soil spaces. We therefore propose to direct future research explicitly towards such biologically nonpreferred areas where decomposition rates are slow, or where decomposition is frequently interrupted, in order to assess the potential for long-term preservation of C in the soil.

Capturing the complexity of water uses and water users within a multi-agent framework

Abstract: Due to the hydrological and socio-economic complexity of water use within river basins and even sub-basins, it is a considerable challenge to manage water resources in an efficient, equitable and sustainable way. This paper shows that multi-agent simulation (MAS) is a promising approach to better understand the complexity of water uses and water users within sub-basins. This approach is especially suitable to take the collective action into account when simulating the outcome of technical innovation and policy change. A case study from Chile is used as an example to demonstrate the potential of the MAS framework. Chile has played a pioneering role in water policy reform by privatizing water rights and promoting trade in such rights, devolving irrigation management authority to user groups, and privatizing the provision of irrigation infrastructure. The paper describes the different components of a MAS model developed for four micro-watersheds in the Maule river basin. Preliminary results of simulation experiments are presented, which show the impacts of technical change and of informal rental markets on household income and water use efficiency. The paper also discusses how the collective action problems in water markets and in small-scale and large-scale infrastructure provision can be captured by the MAS model. To promote the use of the MAS approach for planning purposes, a collaborative research and learning framework has been established, with a recently created multi-stakeholder platform at the regional level (Comision Regional de Recursos Hidricos) as the major partner. Finally, the paper discusses the potentials of using MAS models for water resources management, such as increasing transparency as an aspect of good governance. The challenges, for example the need to build trust in the model, are discussed as well.

Ruminal biohydrogenation as affected by tannins in vitro

Abstract: The aim of the present work was to study the effects of tannins from carob (CT; Ceratonia siliqua), acacia leaves (AT; Acacia cyanophylla) and quebracho (QT; Schinopsis lorentzii) on ruminal biohydrogenation in vitro. The tannins extracted from CT, AT and QT were incubated for 12 h in glass syringes in cow buffered ruminal fluid (BRF) with hay or hay plus concentrate as a substrate. Within each feed, three concentrations of tannins were used (0.0, 0.6 and 1.0 mg/ml BRF). The branched-chain volatile fatty acids, the branched-chain fatty acids and the microbial protein concentration were reduced (P < 0.05) by tannins. In the tannin-containing fermenters, vaccenic acid was accumulated (+23 %, P < 0.01) while stearic acid was reduced ( - 16 %, P < 0.0005). The concentration of total conjugated linoleic acid (CLA) isomers in the BRF was not affected by tannins. The assay on linoleic acid isomerase (LA-I) showed that the enzyme activity (nmol CLA produced/min per mg protein) was unaffected by the inclusion of tannins in the fermenters. However, the CLA produced by LA-I (nmol/ml per min) was lower in the presence of tannins. These results suggest that tannins reduce ruminal biohydrogenation through the inhibition of the activity of ruminal micro-organisms.

Genome Properties and Prospects of Genomic Prediction of Hybrid Performance in a Breeding Program of Maize

Abstract: Maize (Zea mays L.) serves as model plant for heterosis research and is the crop where hybrid breeding was pioneered. We analyzed genomic and phenotypic data of 1254 hybrids of a typical maize hybrid breeding program based on the important Dent × Flint heterotic pattern. Our main objectives were to investigate genome properties of the parental lines (e.g., allele frequencies, linkage disequilibrium, and phases) and examine the prospects of genomic prediction of hybrid performance. We found high consistency of linkage phases and large differences in allele frequencies between the Dent and Flint heterotic groups in pericentromeric regions. These results can be explained by the Hill–Robertson effect and support the hypothesis of differential fixation of alleles due to pseudo-overdominance in these regions. In pericentromeric regions we also found indications for consistent marker–QTL linkage between heterotic groups. With prediction methods GBLUP and BayesB, the cross-validation prediction accuracy ranged from 0.75 to 0.92 for grain yield and from 0.59 to 0.95 for grain moisture. The prediction accuracy of untested hybrids was highest, if both parents were parents of other hybrids in the training set, and lowest, if none of them were involved in any training set hybrid. Optimizing the composition of the training set in terms of number of lines and hybrids per line could further increase prediction accuracy. We conclude that genomic prediction facilitates a paradigm shift in hybrid breeding by focusing on the performance of experimental hybrids rather than the performance of parental lines in testcrosses.