Millimetre scale aeration of the rhizosphere and drilosphere

Soil aeration is a critical factor for oxygen-limited subsoil processes, as transport by diffusion and advection is restricted by the long distance to the free atmosphere. Oxygen transport into the soil matrix is highly dependent on its connectivity to larger pore channels like earthworm and root colonised biopores. Here we hypothesize that the soil matrix around biopores represents different connectivity depending on biopore genesis and actual coloniser. We analysed the soil pore system of undisturbed soil core samples around biopores generated or colonised by roots and earthworms and compared them with the pore system of soil, not in the immediacy of a biopore. Oxygen partial pressure profiles and gas relative diffusion was measured in the rhizosphere and drilosphere from the biopore wall into the bulk soil with microelectrodes. The measurements were linked with structural features such as porosity and connectivity obtained from X-ray tomography and image analysis. Aeration was enhanced in the soil matrix surrounding biopores in comparison to the bulk soil, shown by higher oxygen concentrations and higher relative diffusion coefficients. Biopores colonised by roots presented more connected lateral pores than earthworm colonised ones, which resulted in enhanced aeration of the rhizosphere compared to the drilosphere. This has influenced biotic processes (microbial turnover/mineralization or root respiration) at biopore interfaces and highlights the importance of microstructural features for soil processes and their dependency on the biopore's coloniser.     

Variety of non‐invasive continuous monitoring methodologies including electrical impedance tomography provides novel insights into the physiology of lung collapse and recruitment – case report of an anaesthetized horse

IntroductionThe use of alveolar recruitment maneuvers during general anaesthesia of horses is a potentially useful therapeutic option for the ventilatory management. While the routine application of recruitments would benefit from the availability of dedicated large animal ventilators their impact on ventilation and perfusion in the horse is not yet well documented nor completely understood.Case historyA healthy 533 kg experimental horse underwent general anaesthesia in lateral recumbency. During intermittent positive pressure ventilation a stepwise alveolar recruitment maneuver was performed.ManagementAnaesthesia was induced with ketamine and midazolam and maintained with isoflurane in oxygen using a large animal circle system. Mechanical ventilation was applied in pressure ventilation mode and an alveolar recruitment maneuver performed employing a sequence of ascending and descending positive end expiratory pressures. Next to the standard monitoring, which included spirometry, additionally three non-invasive monitoring techniques were used: electrical impedance tomography (EIT), volumetric capnography and respiratory ultrasonic plethysmography. The functional images continuously delivered by EIT initially showed markedly reduced ventilation in the dependent lung and allowed on-line monitoring of the dynamic changes in the distribution of ventilation during the recruitment maneuver. Furthermore, continuous monitoring of compliance, dead space fraction, tidal volumes and changes in end expiratory lung volume were possible without technical difficulties.Follow upThe horse made an unremarkable recovery.ConclusionThe novel non-invasive monitoring technologies used in this study provided unprecedented insights into the physiology of lung collapse and recruitment. The synergic information of these techniques holds promise to be useful when developing and evaluating new ventilatory strategies in horses.     

Genetic diversity and population structure of Capsicum baccatum genetic resources

Capsicum baccatum is one of five domesticated pepper species which, despite its morphological and ecological variability, has been underexploited for germplasm improvement. Utilizing a broad spectrum of domesticated and wild C. baccatum germplasm, we utilize AFLP markers to describe the species’ molecular diversity and population structure in the South American gene pool. Analysis of molecular variance (AMOVA) revealed greater genetic diversity in the wild form of C. baccatum (C. baccatum var. baccatum) than in the domesticated form of the species (C. baccatum var. pendulum). Both Bayesian and distance based clustering analysis, as well as principal coordinates analysis (PCA), concordantly demonstrated admixture/shared ancestry between wild and cultivated C. baccatum botanical varieties. Two principal genetic groups were identified in the domesticated C. baccatum accessions largely based on their geographic distribution in South America. One group was predominated by accessions from the western territories of the species’ distribution (Peru, Colombia, Ecuador, Bolivia, Chile and northwestern Argentina) and the second by accessions from the eastern regions, Paraguay and eastern Argentina). The two genetic groups overlapped in the geographic location of present-day Bolivia. The grouping pattern suggested that C. baccatum was domesticated in multiple sites and that its evolution took two lineages followed by lineage differentiation. The wild accessions most closely related to the cultigens were found in the highlands of Peru and Bolivia, which support the early hypothesis that this region is one of the domestication sites of this species. A Bayesian assignment analysis demonstrated that Brazilian wild forms of C. baccatum were genetically distant to all other accessions and made little to no contribution to the domesticated genepool. Moreover, results of clustering analysis suggested that C. baccatum likely originated from present day Paraguay. Analysis of inter-specific relationships across selected Capsicum species supported independent lineages for the two crossability groups within Capsicum, the baccatum species-complex (including C. baccatum) and the annuum species-complex (including C. annuum, C. chinense and C. frutescens). However, the results did not support taxonomic distinction of C. baccatum var. umbilicatum from C. baccatum var. pendulum. The present study provides new insights into the domestication of C. baccatum. The results will be useful for identifying accessions for crop improvement and guiding the development of in situ and ex situ conservation programs.     

Suitability of inorganic and organic amendments for in situ immobilization of Cd,Cu, and Zn in a strongly contaminated Kastanozem of the Mashavera valley,SE Georgia. I. Effect of amendments on metal mobility and microbial activity in soil

The aim was to find an adequate, cost‐efficient in situ remediation technique for the Mashavera valley, a mining area in SE Georgia heavily contaminated with Cd, Cu, and Zn. A 12‐month experiment was conducted to test: iron grit, natural zeolite, biochar, and Divergan® (a scavenger) for soil melioration. The amendments were added in different concentrations to the topsoil of a Kastanozem. Mobile metal concentrations decreased with increasing concentrations of amendments in the sequence Divergan® >> iron grit ≈ natural zeolite > biochar. In the same order amendments enhanced activities of soil microbial respiration, alkaline phosphatase, and dehydrogenase; microbial C also followed this trend. A sequential extraction confirmed a shift from easily mobilized to heavily bound fractions. The addition of 2% (w/w) of Divergan® was sufficient to lower mobile trace metal concentrations below German thresholds by chemisorption, and soil microbial activity was significantly increased. The effects of all other treatments were at a much lower level and not found suitable due to needed application rates.     

Physical properties of a Luvisol for different long‐term fertilization treatments: II. Microscale behavior and its relation to the mesoscale

We determined the impact of different fertilization, namely organic vs. mineral fertilization, on the mesoscale parameter cyclic compressibility as well as on rheology of soil samples as a microscale parameter and how these parameters are related. Therefore, undisturbed samples were taken from a long‐term fertilization trial at the Dikop farm near Bonn (Germany) and tested for their mechanical and hydraulic properties. This paper examines the sensitivity of the soil towards cyclic loading (mesoscale) and oscillatory shearing at the microscale by means of an amplitude sweep test and the resulting parameter maximum shear stress. Fertilization increased cyclic compressibility and thus revealed structural weakness of fertilized soil samples, so did shear stress at the microscale. The main reason for this was a decrease in bulk density in the wake of fertilization. However, within the range of fertilized soil samples, the soil structure became less susceptible towards cyclic loading and oscillatory shearing, respectively, the more organic matter the soil contained (equivalent to the fertilization level). This was assumedly caused by enhanced cementation due to organic substances that could partly substitute the direct grain–grain contacts generally contributing to soil strength. The similar behavior of cyclic compressibility and maximum shear stress enabled a first approach to relate soil mechanical parameters at the microscale to those at the mesoscale.     

Iron oxide mineralogy and stable iron isotope composition in a Gleysol with petrogleyic properties

Purpose  

Properties of Fe oxides are poorly understood in soils with fluctuating water tables and variable redox conditions. The objective of this research was to (a) characterize the mineralogical composition of Fe oxides and (b) determine the relationship to the stable Fe isotope ratio in a soil with temporally and spatially sharp redox gradients.     

Effects of temporal floral resource availability and non-crop habitats on broad bean pollination

Landscape Ecology - Flowering plants can enhance wild insect populations and their pollination services to crops in agricultural landscapes, especially when they flower before the focal crop....     

Density multiplication and improved lithography by directed block copolymer assembly

Self-assembling materials spontaneously form structures at length scales of interest in nanotechnology. In the particular case of block copolymers, the thermodynamic driving forces for self-assembly are small, and low-energy defects can get easily trapped. We directed the assembly of defect-free arrays of isolated block copolymer domains at densities up to 1 terabit per square inch on chemically patterned surfaces. In comparing the assembled structures to the chemical pattern, the density is increased by a factor of four, the size is reduced by a factor of two, and the dimensional uniformity is vastly improved.     

Common sequence polymorphisms shaping genetic diversity in Arabidopsis thaliana

The genomes of individuals from the same species vary in sequence as a result of different evolutionary processes. To examine the patterns of, and the forces shaping, sequence variation in Arabidopsis thaliana, we performed high-density array resequencing of 20 diverse strains (accessions). More than 1 million nonredundant single-nucleotide polymorphisms (SNPs) were identified at moderate false discovery rates (FDRs), and approximately 4% of the genome was identified as being highly dissimilar or deleted relative to the reference genome sequence. Patterns of polymorphism are highly nonrandom among gene families, with genes mediating interaction with the biotic environment having exceptional polymorphism levels. At the chromosomal scale, regional variation in polymorphism was readily apparent. A scan for recent selective sweeps revealed several candidate regions, including a notable example in which almost all variation was removed in a 500-kilobase window. Analyzing the polymorphisms we describe in larger sets of accessions will enable a detailed understanding of forces shaping population-wide sequence variation in A. thaliana.     

Territorial division: the least-time constraint behind the formation of subnational boundaries

Nations usually locate their smaller administrative subdivisions in regions of highest population density. This report derives a precise form of the size-density relationship from the general assumption that social structures evolve in such a way as to minimize the total time expended by society in their operation. The result is confirmed empirically.