Genomic analyses of flowering transition and inflorescence development in grapevine = Análisis genómicos de la transición floral y del desarrollo de la inflorescencia en la vid

The general objective of this work is to analyze the regulatory processes underlying flowering transition and inflorescence and flower development in grapevine. Most of these crucial developmental events take place within buds growing during two seasons in two consecutive years. During the first season, the shoot apical meristem within the bud differentiates all the basic elements of the shoot including flowering transition in lateral primordia and development of inflorescence primordia. These events practically end with bud dormancy. The second season, buds resume shoot growth associated to flower formation and development. In grapevine, the lateral meristems can give rise either to tendril or inflorescence primordia that are homologous organs. With this purpose, we performed global transcriptome analyses along the bud annual cycle and during inflorescence and tendril development. In addition, we approach the genomic analysis of the MIKC type MADS-box gene family in grapevine to identify all its members and assign them putative biological functions. Regarding buds developmental cycle, the results indicate that the main factors explaining the global gene expression differences were the processes of bud dormancy and active growth as well as stress responses. Non dormant buds exhibited up-regulation in functional categories typical of actively proliferating and growing cells (photosynthesis, cell cycle regulation, chromatin assembly) whereas in dormant ones the main functional categories up-regulated were associated to stress response pathways together with transcripts related to starch catabolism. Major transcriptional changes during the dormancy period were associated to the para/endodormancy, endo/ecodormancy and ecodormancy/bud break transitions. Global transcriptional analyses along tendril and inflorescence development suggested that these two homologous organs share a common transcriptional program related to cell proliferation functions. Both structures showed a progressive decrease in the expression of categories such as cell-cycle, auxin metabolism/signaling, DNA metabolism, chromatin assembly and a cluster of five transcripts belonging to the GROWTH-REGULATING FACTOR (GRF) transcription factor family, that are known to control cell proliferation in other species and determine the size of lateral organs. However, they also showed organ specific transcriptional programs that can be related to their differential organ structure and function. Tendrils showed higher transcription of genes related to photosynthesis, hormone signaling and secondary metabolism than inflorescences, while inflorescences have higher transcriptional activity for genes encoding transcription factors (especially those belonging to the MADS-box gene family). Further analysis along inflorescence development evidenced the relevance of additional functions likely related to processes of flower development such as fatty acid and lipid metabolism, jasmonate signaling and oxylipin biosynthesis. The transcriptional analyses performed highlighted the relevance of several groups of transcriptional regulators in the developmental processes studied. The expression profiles along bud development revealed significant differences for some MADS-box subfamilies in relation to other plant species, like the members of the FLC and SVP subfamilies suggesting new roles for these groups in grapevine. In this way, it was found that VvFLC2 and VvAGL15.1 could participate, together with some members of the SPL-L family, in dormancy regulation, as was shown for some of them in other woody plants. Similarly, the expression patterns of the VvFLC1, VvFUL, VvSOC1.1 (together with VvFT, VvMFT1 and VFL) genes could indicate that they play a role in flowering transition in grapevine, in parallel to their roles in other plant systems. The expression levels of VFL, the grapevine LEAFY homolog, could be crucial to specify the development of inflorescence and flower meristems instead of tendril meristems. MADS-box genes VvAP3.1 and 2, VvPI, VvAG1 and 3, VvSEP1-4, as well as VvBS1 and 2 are likely associated with the events of flower meristems and flower organs differentiation, while VvAP1 and VvFUL-L (together with VvSOC1.1, VvAGL6.2) could be involved on tendril development given their expression patterns. In addition, the biological function ofVvAP1 and VvTFL1A was analyzed using a gene silencing approach in transgenic grapevine plants. Our preliminary results suggested a possible role for both genes in the initiation and differentiation of tendrils. Finally, the genomic analysis of the MADS-box gene family in grapevine revealed differential features regarding number and expression pattern of genes putatively involved in the flowering transition process as compared to those involved in the specification of flower and fruit organ identity. Altogether, the results obtained allow identifying putative candidate genes and pathways regulating grapevine reproductive developmental processes paving the way to future experiments demonstrating specific gene biological functions. RESUMEN El objetivo general de este trabajo es analizar los procesos regulatorios subyacentes a la inducción floral así como al desarrollo de la inflorescencia y la flor en la vid. La mayor parte de estos eventos cruciales tienen lugar en las yemas a lo largo de dos estaciones de crecimiento consecutivas. Durante la primera estación, el meristemo apical contenido en la yema diferencia los elementos básicos del pámpano, lo cual incluye la inducción de la floración en los meristemos laterales y el subsiguiente desarrollo de primordios de inflorescencia. Estos procesos prácticamente cesan con la entrada en dormición de la yema. En la segunda estación, se reanuda el crecimiento del pámpano acompañado por la formación y desarrollo de las flores. En la vid, los meristemos laterales pueden dar lugar a primordios de inflorescencia o de zarcillo que son considerados órganos homólogos. Con este objetivo llevamos a cabo un estudio a nivel del transcriptoma de la yema a lo largo de su ciclo anual, así como a lo largo del desarrollo de la inflorescencia y del zarcillo. Además realizamos un análisis genómico de la familia MADS de factores transcripcionales (concretamente aquellos del tipo MIKC) para identificar todos sus miembros y tratar de asignarles posibles funciones biológicas. En cuanto al ciclo de desarrollo de la yema, los resultados indican que los principales factores que explican las diferencias globales en la expresión génica fueron los procesos de dormición de la yema y el crecimiento activo junto con las respuestas a diversos tipos de estrés. Las yemas no durmientes mostraron un incremento en la expresión de genes contenidos en categorías funcionales típicas de células en proliferación y crecimiento activo (como fotosíntesis, regulación del ciclo celular, ensamblaje de cromatina), mientras que en las yemas durmientes, las principales categorías funcionales activadas estaban asociadas a respuestas a estrés, así como con el catabolismo de almidón. Los mayores cambios observados a nivel de transcriptoma en la yema coincidieron con las transiciones de para/endodormición, endo/ecodormición y ecodormición/brotación. Los análisis transcripcionales globales a lo largo del desarrollo del zarcillo y de la inflorescencia sugirieron que estos dos órganos homólogos comparten un programa transcripcional común, relacionado con funciones de proliferación celular. Ambas estructuras mostraron un descenso progresivo en la expresión de genes pertenecientes a categorías funcionales como regulación del ciclo celular, metabolismo/señalización por auxinas, metabolismo de ADN, ensamblaje de cromatina y un grupo de cinco tránscritos pertenecientes a la familia de factores transcripcionales GROWTH-REGULATING FACTOR (GRF), que han sido asociados con el control de la proliferación celular y en determinar el tamaño de los órganos laterales en otras especies. Sin embargo, también pusieron de manifiesto programas transcripcionales que podrían estar relacionados con la diferente estructura y función de dichos órganos. Los zarcillos mostraron mayor actividad transcripcional de genes relacionados con fotosíntesis, señalización hormonal y metabolismo secundario que las inflorescencias, mientras que éstas presentaron mayor actividad transcripcional de genes codificantes de factores de transcripción (especialmente los pertenecientes a la familia MADS-box). Análisis adicionales a lo largo del desarrollo de la inflorescencia evidenciaron la relevancia de otras funciones posiblemente relacionadas con el desarrollo floral, como el metabolismo de lípidos y ácidos grasos, la señalización mediada por jasmonato y la biosíntesis de oxilipinas. Los análisis transcripcionales llevados a cabo pusieron de manifiesto la relevancia de varios grupos de factores transcripcionales en los procesos estudiados. Los perfiles de expresión estudiados a lo largo del desarrollo de la yema mostraron diferencias significativas en algunas de las subfamilias de genes MADS con respecto a otras especies vegetales, como las observadas en los miembros de las subfamilias FLC y SVP, lo cual sugiere que podrían desempeñar nuevas funciones en la vid. En este sentido, se encontró que los genes VvFLC2 y VvAGL15.1 podrían participar, junto con algunos miembros de la familia SPL-L, en la regulación de la dormición. De un modo similar, los patrones de expresión de los genes VvFLC1, VvFUL, VvSOC1.1 (junto con VvFT, VvMFT1 y VFL) podría indicar que desempeñan un papel en la regulación de la inducción de la floración en la vid, como se ha observado en otros sistemas vegetales. Los niveles de expresión de VFL, el homólogo en vid del gen LEAFY de A. thaliana podrían ser cruciales para la especificación del desarrollo de meristemos de inflorescencia y flor en lugar de meristemos de zarcillo. Los genes VvAP3.1 y 2, VvPI, VvAG1 y 3, VvSEP1-4, así como VvBS1 y 2 parecen estar asociados con los eventos de diferenciación de meristemos y órganos florales, mientras que VvAP1 y VvFUL-L (junto con VvSOC1.1 y VvAGL6.2) podrían estar implicados en el desarrollo del zarcillo dados sus patrones de expresión. Adicionalmente, se analizó la función biológica de los genes VvAP1 y VvTFL1A por medio de una estrategia de silenciamiento génico. Los datos preliminares sugieren un posible papel para ambos genes en la iniciación y diferenciación de los zarcillos. Finalmente, el análisis genómico de la familia MADS en vid evidenció diferencias con respecto a otras especies vegetales en cuanto a número de miembros y patrón de expresión en genes supuestamente implicados en la inducción de la floración, en comparación con aquellos relacionados con la especificación de identidad de órganos florales y desarrollo del fruto. En conjunto, los resultados obtenidos han permitido identificar posibles rutas y genes candidatos a participar en la regulación de los procesos de desarrollo reproductivo de la vid, sentando las bases de futuros experimentos encaminados a conocer la funciones biológicas de genes específicos.

Using quantitative descriptive analysis and temporal dominance of sensations analysis as complementary methods for profiling commercial blackcurrant squashes

Quantitative descriptive analysis (QDA) is used to describe the nature and the intensity of sensory properties from a single evaluation of a product, whereas temporal dominance of sensation (TDS) is primarily used to identify dominant sensory properties over time. Previous studies with TDS have focused on model systems, but this is the first study to use a sequential approach, i.e. QDA then TDS in measuring sensory properties of a commercial product category, using the same set of trained assessors (n = 11). The main objectives of this study were to: (1) investigate the benefits of using a sequential approach of QDA and TDS and (2) to explore the impact of the sample composition on taste and flavour perceptions in blackcurrant squashes. The present study has proposed an alternative way of determining the choice of attributes for TDS measurement based on data obtained from previous QDA studies, where available. Both methods indicated that the flavour profile was primarily influenced by the level of dilution and complexity of sample composition combined with blackcurrant juice content. In addition, artificial sweeteners were found to modify the quality of sweetness and could also contribute to bitter notes. Using QDA and TDS in tandem was shown to be more beneficial than each just on its own enabling a more complete sensory profile of the products.

The trade credit in the Spanish agrofood industry

Selling on credit is rather frequent in Mediterranean countries. Its generalized use can lead to excessive enlargements of the payment periods and consequently can deteriorate the profitability of firms. In spite of the relevance of this problem there are few empirical researches. This work intends to fill this gap and to shed light on the factors related to the extension of trade credit. In the theoretical and empirical literature, different motives have been proposed to explain this issue: a mechanism to reduce transaction costs, a financial alternative to the bank system and an additional tool to improve commercial activities. To contrast these ideas a panel of 388 firms of the Spanish agrofood industry has been taken, and static and dynamic regression models have been estimated by using robust methods to heteroskedasticity, autocorrelation and endogeneity of the explanatory variables. The results confirm that trade credit receivable is associated with more active firms and with cheaper bank financing. Other factors with positive relationships are short-term bank debts and accounts payable. These findings are consistent with commercial motives, rather than a pure financial view, in the sense that financial distressed producers extend trade credit as a way of promoting their products and in turn increasing their sales.

Beitrag zur Entwicklung der Querschnittsgestaltung im Verbundbrückenbau

Die grafische Darstellung des Verbundquerschnittes mit einer oberen Betonplatte und einem darunter liegenden Stahlträger war seit seiner Vorstellung in den 1950er Jahren ein Symbol, das weit über die Theorie hinausging und weite Verbreitung in der Praxis des Verbundbrückenbaus fand. Seit den 1970er bzw. 1980er Jahren hat dieses Bild – bedingt durch neue und freiere Formen, Beton und Stahl miteinander zu kombinieren – seine Symbolhaftigkeit verloren. In Deutschland und Spanien wurde der Doppelverbund mit unten liegenden Betonplatten in Bereichen mit negativen Momenten eingeführt, in Frankreich werden Stahlträger auch in vorgespannten Betonquerschnitten eingebettet. Beide Ansätze haben dazu beigetragen, dass in der Gegenwart die Materialien Stahl und Beton im Verbundbau frei miteinander kombiniert werden können. On the development of sections in composite bridges. A comprehensive theory of composite construction was established in Germany by Sattler in 1953. The theoretical image of the composite section with a superior concrete slab and a lower metallic structure was shaped in addition to the analytical resolution. Theory and graphical representation were going to be known together in Europe. This figure was repeated in all theoretical and academic publications, so becoming an authentic icon of the composite section. Its translation to the bridge deck in flexion was obvious: the superior slab defines the tread platform, while the metallic structure was left off-hook at the bottom. Nevertheless, in continuous decks the section is not optimal at all in zones of negative bending moments. But the overcoming of the graphical representation of the theory did not happen immediately. It was produced after a process in which several European countries played an active role and where different mechanisms of technological transference were developed. One approach to this overcoming is the “double composite action”, with a lower concrete slab in areas of a negative bending moment. The first accomplishments, a bridge in Orasje built in 1968 with 134 m span, as well as the publications of the system proposed by Fabrizio de Miranda in 1971 did not extend nor had continuity. Spanish bridges by Fernández Ordoñez and Martínez Calzón used double composite action for the first time in 1979. The German team of Leonhard, Andrä und partners, has used it since the end of the 1980's to solve bridges of great span. Once the technology has been well known thanks to the ASCE International Congress and the Spanish International Meetings organised by the “Colegio de Ingenieros de Caminos”, double composite action has been integrated well into the structural vocabulary everywhere. In France the approach was different. What Michel Virlogeux calls “double floor composite section” was reached as an evolution of prestressed concrete bridges. In an experimental process widely known, the external prestressing allows weight reduction by diminishing the thickness of the concrete webs. The following step, in the 1980's, was the substitution of the webs by metallic elements: stiffened plates, trusses or folded plates. A direct result of this development is the Brass de la Plaine Bridge in the Reunion Island in 2001 with 280 m span. Both approaches have contributed to a freedom of design in composite construction in steel and concrete today.

Modelos para la simulación dinámica del crecimiento y desarrollo de pastos

Este trabajo recoge una revisión de los modelos para la simulación dinámica del crecimiento y desarrollo de los pastos y su utilización con animales en pastoreo. Los modelos son herramientas para la toma de decisiones en la explotación ganadera y para la investigación. Un modelo dinámico es la representación matemática de un sistema pastoral que evoluciona en el tiempo forzado por un conjunto de variables conductoras. La simulación es el proceso de ejecución de un modelo por el cual se obtiene unos resultados sobre el estado de cada componente. Los principales componentes de los modelos son: el clima o meteorología, el suelo, la vegetación, los animales y el gestor o tomador de decisiones. En este artículo se presentan los principales procesos modelados sobre el crecimiento y desarrollo de la vegetación herbácea y leñosa, y también algunos referentes a la ingesta de los animales. El desarrollo de modelos es un proceso iterativo nunca concluso, este tipo de modelos trata de explicar el comportamiento del sistema y por tanto parte de la variabilidad que presenta no llega a ser explicada por el modelo al ser una simplificación del sistema real. Estos modelos de simulación han ido evolucionando desde simples relaciones matemáticas a complejos sistemas de ecuaciones diferenciales que tiene una representación sobre el territorio, llegándose a los modelos multi-agente, donde confluyen en el mismo espacio diferentes tomadores de decisiones, tipos de vegetación y animales. Los modelos son posibles por la existencia de un mejor conocimiento y descripción de los componentes y procesos que aparecen en los sistemas agrosilvopastorales.

Multiple avirulence paralogues in cereal powdery mildew fungi may contribute to parasite fitness and defeat of plant resistance

Powdery mildews, obligate biotrophic fungal parasites on a wide range of important crops, can be controlled by plant resistance (R) genes, but these are rapidly overcome by parasite mutants evading recognition. It is unknown how this rapid evolution occurs without apparent loss of parasite fitness. R proteins recognize avirulence (AVR) molecules from parasites in a gene-for-gene manner and trigger defense responses. We identify AVRa10 and AVRk1 of barley powdery mildew fungus, Blumeria graminis f sp hordei (Bgh), and show that they induce both cell death and naccessibility when transiently expressed in Mla10 and Mlk1 barley (Hordeum vulgare) varieties, respectively. In contrast with other reported fungal AVR genes, AVRa10 and AVRk1 encode proteins that lack secretion signal peptides and enhance infection success on susceptible host plant cells. AVRa10 and AVRk1 belong to a large family with mayor que30 paralogues in the genome of Bgh, and homologous sequences are present in other formae speciales of the fungus infecting other grasses. Our findings imply that the mildew fungus has a repertoire of AVR genes, which may function as effectors and contribute to parasite virulence. Multiple copies of related but distinct AVR effector paralogues might enable populations of Bgh to rapidly overcome host R genes while maintaining virulence.

Multifractal analysis of the pore- and solid-phases in binary two-dimensional images of natural porous structures

We use multifractal analysis (MFA) to investigate how the Rényi dimensions of the solid mass and the pore space in porous structures are related to each other. To our knowledge, there is no investigation about the relationship of Rényi or generalized dimensions of two phases of the same structure.

A Program for Fractal and Multifractal Analysis of Two-Dimensional Binary Images. Computer Algorithms versus Mathematical Theory.

In this paper we present a tool to carry out the multifractal analysis of binary, two-dimensional images through the calculation of the Rényi D(q) dimensions and associated statistical regressions. The estimation of a (mono)fractal dimension corresponds to the special case where the moment order is q = 0.

Phytoextraction of heavy metals from mine soils using hyperaccumulator plants.

Phytoextraction is an environmental-friendly and cost-effective technology that uses metal hyperaccumulator plants to remove heavy metals from soils. The metals are absorbed by the roots, transported and accumulated in the aerial parts of the plants, which can be harvested and eliminated. The aim of this work was to study some hyperaccumulator species that could be useful to decontaminate mine soils and also to investigate the bioavailability and uptake of these metals by plants with the addition of organic amendments. Pot experiments were performed with soil samples collected from two mining areas in the north of Madrid, where there was an intense mining activity more than 50 years ago. Three species (Thlaspi arvense, Brassica juncea and Atriplex halimus) were grown under controlled conditions in pots filled with contaminated soils mixed with 0 Mg, 30 Mg and 60 Mg per hectare of two different organic amendments: a commercial compost made of pine bark, peat and wood fiber and other made of horse and sheep manure and wood fiber. Plants were harvested at the end of their crop cycle and were digested in order to measure metal concentration (Zn, Cu and Cd) in roots and shoots. Highest plant metal concentration was observed in pots treated with pine bark amendment and with pure soil due to an increase in metal bioavailability with decreasing pH. Also in those treatments the total plant biomass was lower, even some plants could not germinate. On the contrary, there was a lower metal concentration in plant tissues of pots with manure because its higher pH whereas plant growth was significantly larger so there was an incresing amount of metals removed from soil by plants. Comparing the three species results indicate a higher total metal uptake in A. halimus than B. juncea and T. arvense. In conclusion, results show that pH affects metal bioavailability and uptake by hyperaccumulator plants. Addition of organic amendments could be a successful technique for stabilization of metals in contaminated soils.

The family of DOF transcription factors in Brachypodium distachyon: phylogenetic comparison with rice and barley DOFs and expression profiling

ABSTRACT: Transcription factors (TFs) are proteins that have played a central role both in evolution and in domestication, and are major regulators of development in living organisms. Plant genome sequences reveal that approximately 7% of all genes encode putative TFs. The DOF (DNA binding with One Finger) TF family has been associated with vital processes exclusive to higher plants and to their close ancestors (algae, mosses and ferns). These are seed maturation and germination, light-mediated regulation, phytohormone and plant responses to biotic and abiotic stresses, etc. In Hordeum vulgare and Oryza sativa, 26 and 30 different Dof genes, respectively, have been annotated. Brachypodium distachyon has been the first Pooideae grass to be sequenced and, due to its genomic, morphological and physiological characteristics, has emerged as the model system for temperate cereals, such as wheat and barley. RESULTS: Through searches in the B. distachyon genome, 27 Dof genes have been identified and a phylogenetic comparison with the Oryza sativa and the Hordeum vulgare DOFs has been performed. To explore the evolutionary relationship among these DOF proteins, a combined phylogenetic tree has been constructed with the Brachypodium DOFs and those from rice and barley. This phylogenetic analysis has classified the DOF proteins into four Major Cluster of Orthologous Groups (MCOGs). Using RT-qPCR analysis the expression profiles of the annotated BdDof genes across four organs (leaves, roots, spikes and seeds) has been investigated. These results have led to a classification of the BdDof genes into two groups, according to their expression levels. The genes highly or preferentially expressed in seeds have been subjected to a more detailed expression analysis (maturation, dry stage and germination). CONCLUSIONS: Comparison of the expression profiles of the Brachypodium Dof genes with the published functions of closely related DOF sequences from the cereal species considered here, deduced from the phylogenetic analysis, indicates that although the expression profile has been conserved in many of the putative orthologs, in some cases duplication followed by subsequent divergence may have occurred (neo-functionalization).

Validation of microsatellite markers for cytotype discrimination in the model grass Brachypodium distachyon

Brachypodium distachyon (2n = 2x = 10) is a small annual grass species where the existence of three different cytotypes (10, 20 and 30 chromosomes) has long been regarded as a case of autopolyploid series, with x = 5. However, it has been demonstrated that the cytotypes assumed to be polyploids represent two separate Brachypodium species recently named as B. stacei (2n = 2x = 20) and B. hybridum (2n = 4x = 30). The aim of this study was to find a PCR-based alternative approach that could replace standard cytotyping methods (i. e., chromosome counting and flow cytometry) to characterize each of the three Brachypodium species. We have analyzed with four microsatellite (SSR) markers eighty-three Brachypodium distachyon-type lines from varied locations in Spain, including the Balearic and Canary Islands. Within this set of lines, 64, 4 and 15 had 10, 20 and 30 chromosomes, respectively. The surveyed markers produced cytotype-specific SSR profiles. So, a single amplification product was generated in the diploid samples, with non-overlapping allelic ranges between the 2n = 10 and 2n = 20 cytotypes, whereas two bands, one in the size range of each of the diploid cytotypes, were amplified in the 2n = 30 lines. Furthermore, the remarkable size difference obtained with the SSR ALB165 allowed the identification of the Brachypodium species by simple agarose gel electrophoresis.

A PCR-based method for discriminating between high molecular weight glutenin subunits Bx7 and Bx7* in Triticum aestivum L

The correct assignment of high molecular weight glutenin subunit variants is a key task in wheat breeding. However, the traditional analysis by protein electrophoresis is sometimes difficult and not very precise. This work describes a novel DNA marker for the accurate discrimination between the Glu-B1 locus subunits Bx7 and Bx7*. The analysis of one hundred and forty two bread wheat cultivars from different countries has highlighted a great number of misclassifications in the literature that could lead to wrong conclusions in studies of the relationship between glutenin composition and wheat quality.

Diversity and Genetic structure of the Spanish collection of durum wheat (Triticum turgidum L) landraces

The objectives of this study were to assess diversity and genetic structure of a collection of Spanish durum wheat (Triticum turgidum L) landraces, using SSRs, DArTs and gliadin-markers, and to correlate the distribution of diversity with geographic and climatic features, as well as agro-morphological traits. A high level of diversity was detected in the genotypes analyzed, which were separated into nine populations with a moderate to great genetic divergence among them. The three subspecies taxa, dicoccon, turgidum and durum, present in the collection, largely determined the clustering of the populations. Genotype variation was lower in dicoccon (one major population) and turgidum (two major populations) than in durum (five major populations). Genetic differentiation by the agro-ecological zone of origin was greater in dicoccon and turgidum than in durum. DArT markers revealed two geographic substructures, east-west for dicoccon and northeast-southwest for turgidum. The ssp. durum had a more complex structure, consisting of seven populations with high intra-population variation. DArT markers allowed the detection of subgroups within some populations, with agro-morphological and gliadin differences, and distinct agro-ecological zones of origin. Two different phylogenetic groups were detected; revealing that some durum populations were more related to ssp. turgidum from northern Spain, while others seem to be more related to durum wheats from North Africa

Community Structurein Soil Porous System.

Soil is well recognized as a highly complex system. The interaction and coupled physical, chemical, and biological processes and phenomena occurring in the soil environment at different spatial and temporal scales are the main reasons for such complexity. There is a need for appropriate methodologies to characterize soil porous systems with an interdisciplinary character. Four different real soil samples, presenting different textures, have been modeled as heterogeneous complex networks, applying a model known as the heterogeneous preferential attachment. An analytical study of the degree distributions in the soil model shows a multiscaling behavior in the connectivity degrees, leaving an empirically testable signature of heterogeneity in the topology of soil pore networks. We also show that the power-law scaling in the degree distribution is a robust trait of the soil model. Last, the detection of spatial pore communities, as densely connected groups with only sparser connections between them, has been studied for the first time in these soil networks. Our results show that the presence of these communities depends on the parameter values used to construct the network. These findings could contribute to understanding the mechanisms of the diffusion phenomena in soils, such as gas and water diffusion, development and dynamics of microorganisms, among others.

Spatial variability patterns of some Vertisol properties at a field scale using standardized data

Spatial variability of Vertisol properties is relevant for identifying those zones with physical degradation. In this sense, one has to face the problem of identifying the origin and distribution of spatial variability patterns. The objectives of the present work were (i) to quantify the spatial structure of different physical properties collected from a Vertisol, (ii) to search for potential correlations between different spatial patterns and (iii) to identify relevant components through multivariate spatial analysis. The study was conducted on a Vertisol (Typic Hapludert) dedicated to sugarcane (Saccharum officinarum L.) production during the last sixty years. We used six soil properties collected from a squared grid (225 points) (penetrometer resistance (PR), total porosity, fragmentation dimension (Df), vertical electrical conductivity (ECv), horizontal electrical conductivity (ECh) and soil water content (WC)). All the original data sets were z-transformed before geostatistical analysis. Three different types of semivariogram models were necessary for fitting individual experimental semivariograms. This suggests the different natures of spatial variability patterns. Soil water content rendered the largest nugget effect (C0 = 0.933) while soil total porosity showed the largest range of spatial correlation (A = 43.92 m). The bivariate geostatistical analysis also rendered significant cross-semivariance between different paired soil properties. However, four different semivariogram models were required in that case. This indicates an underlying co-regionalization between different soil properties, which is of interest for delineating management zones within sugarcane fields. Cross-semivariograms showed larger correlation ranges than individual, univariate, semivariograms (A ≥ 29 m). All the findings were supported by multivariate spatial analysis, which showed the influence of soil tillage operations, harvesting machinery and irrigation water distribution on the status of the investigated area.