Quantification of Three Dimensional Characteristics of Macrofauna Macropores and Their Effects on Soil Hydraulic Conductivity in Northern Vietnam

Soil bioturbation is associated with the production of soil macropores that influence numerous ecological functions such as those associated with water infiltration and the generation of runoff water. This impact is especially important on sloping lands in the tropics that are highly susceptible to erosion. In this study, we questioned the influence of soil biodiversity on soil macropore properties (>20 mm3) and saturated hydraulic conductivity (Ksat) on sloping land in northern Vietnam. Biostructures found at the soil surface (casts, sheetings, and soil excavated on the ground) were used to identify areas colonized either by earthworms, termites or dung beetles, respectively. The influence of soil macrofauna on Ksat was measured in situ using the Beerkan method below bioturbated zones and compared to the surrounding soil without visible biostructures at the soil surface. Undisturbed soil columns were afterwards sampled and scanned by X-ray computed tomography (X-ray CT). Properties of macropores below each biostructure depicted a large variability, revealing the complexity of the macropore network. Further, galleries made by termites, dung beetles, and earthworms were manually isolated from the rest of macroporosity. Galleries made by beetles, termites and earthworms were clearly differentiated on the basis of their diameter, verticality, sphericity, tortuosity, length and number of branches and the fraction of galleries in the top part of the column. Ksat was most increased by dung beetles (45-fold), then by termites (30-fold) and to a lesser extent by earthworms (16-fold). Relationships between total macropore properties and Ksat showed that the most important properties explaining Ksat were (i) the volume of percolating macropores, (ii) the diameter, (iii) the critical macropore diameter, and (iv) the number of macropores. In conclusion, this study confirmed not only the interest in using X-ray CT for the quantification of macroporosity but also the absence of a clear relationship between aboveground biostructures and macropore properties and functional impacts

The Extragalactic Distance Database: All Digital HI Profile Catalog

An important component of the Extragalactic Distance Database (EDD) at http://edd.ifa.hawaii.edu is a group of catalogs related to the measurement of HI line profile parameters. One of these is the All Digital HI catalog which contains an amalgam of information from new data and old. The new data results from observations with Arecibo and Parkes telescopes and with the Green Bank Telescope (GBT), including continuing input since the award of the NRAO Cosmic Flows Large Program. The old data has been collected from archives, wherever available, particularly the Cornell University Digital HI Archive, the Nancay Telescope extragalactic HI archive, and the Australia Telescope archive. The catalog currently contains information on ~15,000 profiles relating to ~13,000 galaxies. The channel - flux per channel files, from whatever source, are carried through a common pipeline. The derived parameter of greatest interest is W_m50, the profile width at 50% of the mean flux. After appropriate adjustment, the parameter W_mx is derived, the linewidth which statistically approximates the peak to peak maximum rotation velocity before correction for inclination, 2 V_max sin(i).Comment: 19 pages, 22 figures, Astronomical Journal (anticipated 2009, December

Lessons from a landmark 1991 article on soil structure: distinct precedence of non-destructive assessment and benefits of fresh perspectives in soil research

In 1991, at the launch of a national symposium devoted to soil structure, the Australian Society of Soil Science invited Professor John Letey to deliver a keynote address, which was later published in the society’s journal. In his lecture, he shared the outcome of his reflexion about what the assessment of soil structure should amount to, in order to produce useful insight into the functioning of soils. His viewpoint was that the focus should be put on the openings present in the structure, rather than on the chunks of material resulting from its mechanical dismantlement. In the present article, we provide some historical background for Letey’s analysis, and try to explain why it took a number of years for the paradigm shift that he advocated to begin to occur. Over the last decade, his perspective that soil structure needs to be characterised via non-destructive methods appears to have gained significant momentum, which is likely to increase further in the near future, as we take advantage of recent technological advances. Other valuable lessons that one can derive from Letey’s pioneering article relate to the extreme value for everyone, even neophytes, to constantly ask questions about where research on given topics is heading, what its goals are, and whether the methods that are used at a certain time are optimal

Traces of trauma – a multivariate pattern analysis of childhood trauma, brain structure and clinical phenotypes

Background: Childhood trauma (CT) is a major yet elusive psychiatric risk factor, whose multidimensional conceptualization and heterogeneous effects on brain morphology might demand advanced mathematical modeling. Therefore, we present an unsupervised machine learning approach to characterize the clinical and neuroanatomical complexity of CT in a larger, transdiagnostic context. Methods: We used a multicenter European cohort of 1076 female and male individuals (discovery: n = 649; replication: n = 427) comprising young, minimally medicated patients with clinical high-risk states for psychosis; patients with recent-onset depression or psychosis; and healthy volunteers. We employed multivariate sparse partial least squares analysis to detect parsimonious associations between combinations of items from the Childhood Trauma Questionnaire and gray matter volume and tested their generalizability via nested cross-validation as well as via external validation. We investigated the associations of these CT signatures with state (functioning, depressivity, quality of life), trait (personality), and sociodemographic levels. Results: We discovered signatures of age-dependent sexual abuse and sex-dependent physical and sexual abuse, as well as emotional trauma, which projected onto gray matter volume patterns in prefronto-cerebellar, limbic, and sensory networks. These signatures were associated with predominantly impaired clinical state- and trait-level phenotypes, while pointing toward an interaction between sexual abuse, age, urbanicity, and education. We validated the clinical profiles for all three CT signatures in the replication sample. Conclusions: Our results suggest distinct multilayered associations between partially age- and sex-dependent patterns of CT, distributed neuroanatomical networks, and clinical profiles. Hence, our study highlights how machine learning approaches can shape future, more fine-grained CT research

Evolution de la structure et de la perméabilité d'un sol en contexte de non labour associé à l'apport d'effluent d'élevage : rôle de l'activité lombricienne.

Conservation tillage practices are increasingly being used by the farmers; however, their impacts on soil physical properties remain poorly documented, especially when they are combined to manure fertilization. This study aimed at evaluating the effect of reduced tillage and manure fertilization on soil structure and its permeability, particularly in relation with earthworm activity. This study was conducted at the Kerguéhennec experimental station, established in 2000, located in Brittany, France. Three tillage treatments were compared (moldboard plowing, surface tillage and no-tillage) along with two types of fertilizers (poultry manure and mineral). In the first part of this work, we were interested on methodologies to quantify earthworm biostructures (burrows and casts) and the impact of cultural practices on their abundance. In a second part, we have measured the combined effect of cultural practices and earthworm biostructures on the structural stability of aggregates, macroporosity and permeability of soil during one growing season. This work demonstrates the difficulty of quantify earthworm biostructures, particularly earthworm casts. We proposed various indicators, that, when combined provide a good estimate of the abundance of casts. Our results confirm that the abundance of biostructures increases under no-tillage and with manure fertilisation. We also showed that these biostructures evolved during the crop year as a result of climate, tillage and probably the physiological activity of earthworms. Tillage practices alone had a strong impact on soil physical properties in comparison to manure fertilization. Reduced tillage increased soil aggregate stability: this increase was not explained by earthworm activity. No tillage had the lowest soil macroporosity and permeability but the earthworm activity was highest in that treatment. Soil physical properties have changed during the cropping year. The dynamics of soil aggregate stability was affected by the climate with similar fashion in all treatments. Earthworm activity, tillage events and climate were linked closely to the dynamics of soil permeability under tilled treatments. Theses factors influence mainly one class of porosity, the inter-aggregate complex macropores. Under no-tillage, the dynamics of soil permeability was affected by the climate and the abundance of earthworm casts, without significant modification of soil macroporosity (size and shape). Thus, in the experimental conditions of this work, the surface tillage practice has reflected the best soil physical properties, while manure fertilization does not show any obvious impact on the studied soil physical properties. Moreover, our study highlights the importance of earthworm casts on the short term soil permeability variations.Alors que les techniques culturales sans labour sont de plus en plus utilisées par les agriculteurs, leurs effets sur les propriétés physiques du sol restent encore mal documentés en particulier lorsqu'elles sont associées à des apports d'effluents d'élevage. L'objectif de ce travail était d'évaluer l'effet du non labour associé à l'apport d'effluent d'élevage sur la structure et la perméabilité du sol en étudiant plus particulièrement le rôle de l'activité lombricienne. Ce travail repose sur un dispositif expérimental mis en place à Kerguéhennec (Bretagne, France) depuis 8 années sur lequel sont comparées six pratiques culturales croisant trois techniques de travail du sol (le labour conventionnel, le travail superficiel, le semis direct) et deux types de fertilisation (minérale et fumier de volaille). Dans une première partie de ce travail nous nous sommes intéressés aux méthodes pour quantifier les biostructures lombriciennes (galeries et déjections) et à l'impact des pratiques culturales sur leur abondance. Dans une deuxième partie nous avons mesuré l'effet conjoint des pratiques culturales et des biostructures lombriciennes sur la stabilité structurale des agrégats, la macroporosité et la perméabilité du sol au cours d'une année culturale. Ce travail démontre la difficulté de quantifier les biostructures lombriciennes, en particulier les déjections. Nous avons proposé différents indicateurs qui, lorsqu'ils sont combinés, permettent une bonne estimation de l'abondance des déjections. Nos résultats confirment que l'abondance des biostructures est augmentée en semis direct et sous apport de fumier de volaille ; nous montrons par ailleurs que ces biostructures évoluent au cours de l'année culturale sous l'effet du climat, du travail du sol et probablement de l'activité physiologique des lombriciens. Le travail du sol modifie considérablement les propriétés physiques du sol, alors que l'apport d'effluent d'élevage n'a pas d'effet. Le non labour (semis direct et travail superficiel) augmente la stabilité structurale des agrégats du sol : cette augmentation n'est pas expliquée par l'activité lombricienne. Le semis direct présente les plus faibles valeurs de macroporosité et de perméabilité du sol, alors que l'activité lombricienne y est la plus importante. Les propriétés physiques du sol évoluent au cours de l'année culturale au même titre que les biostructures. La stabilité structurale évolue sous l'effet du climat, de la même façon pour toutes les modalités étudiées. La perméabilité des sols travaillés évolue sous l'effet du climat, du travail du sol et de l'activité lombricienne. Ces différents facteurs agissent sur une classe de pores du sol, les macropores inter-agrégats de forme complexe. La perméabilité du sol sous semis direct évolue sous l'effet du climat et de l'abondance des déjections lombriciennes, sans modification significative de la taille et forme de la macroporosité du sol. Ainsi dans les conditions expérimentales de cette étude, le travail superficiel est la modalité qui présente les meilleures propriétés physiques du sol ; l'apport d'effluent d'élevage n'agit pas sur celles-ci. Ce travail met aussi en évidence le rôle important des déjections lombriciennes sur les variations à court terme de la perméabilité du sol

Earthworm ecological categories are not functional groups

International audienceSeven earthworm ecological categories, including anecics, endogeics and epigeics, were defined by Marcel Bouche in 1972 based only on morpho-anatomical characteristics measured on European lumbricids. These categories had an outstanding success, and their use was generalized even outside of Europe. However, most of the time, only the three main categories are used, and over two decades, these categories have been considered functional groups, i.e. to presume how earthworms influence the soil functioning. Moreover, this relationship between ecological categories and functional groups is seldom tested and often uncritically accepted by soil biology researchers. It is then not surprising to observe unexpected trends when earthworm species are gathered in ecological categories to, for instance, analyze burrow systems or cast properties. We believe it is time to acknowledge that ecological categories are not functional, because they were not made for this purpose. We also propose three future directions in order to either improve our knowledge on the functional effects of earthworms or to build new authentically functional groups: (i) going back to the seven initial ecological categories to provide greater accuracy than the usage of the simplified three-level classification; (ii) testing, for a set of selected species, the functionality of the groups, being ecological categories or new tailored ones; and (iii) using trait-based approach in order to study the correlation between some earthworm traits and main soil functions

Earthworm ecological categories are not functional groups

Seven earthworm ecological categories, including anecics, endogeics and epigeics, were defined by Marcel Bouche in 1972 based only on morpho-anatomical characteristics measured on European lumbricids. These categories had an outstanding success, and their use was generalized even outside of Europe. However, most of the time, only the three main categories are used, and over two decades, these categories have been considered functional groups, i.e. to presume how earthworms influence the soil functioning. Moreover, this relationship between ecological categories and functional groups is seldom tested and often uncritically accepted by soil biology researchers. It is then not surprising to observe unexpected trends when earthworm species are gathered in ecological categories to, for instance, analyze burrow systems or cast properties. We believe it is time to acknowledge that ecological categories are not functional, because they were not made for this purpose. We also propose three future directions in order to either improve our knowledge on the functional effects of earthworms or to build new authentically functional groups: (i) going back to the seven initial ecological categories to provide greater accuracy than the usage of the simplified three-level classification; (ii) testing, for a set of selected species, the functionality of the groups, being ecological categories or new tailored ones; and (iii) using trait-based approach in order to study the correlation between some earthworm traits and main soil functions

Effects of ageing under field conditions on soil organic matter in earthworm casts produced by the anecic earthworm Amynthas adexilis in northern Vietnam

International audienceCarbon sequestration in soils became a major issue that governments have to face under their sustainable development objectives and the international 4p1000 program. Although, earthworms are recognized to play a key role in the structure and dynamics of organic matter (OM) in soils, their contribution to soil OM cycling is not taken into account in biogeochemical models nor well understood. In particular, the fate of OM protected in earthworm casts is unknown. In this study, we investigated the effects of ageing under field conditions on the OM dynamics contained in casts produced by the anecic earthworm Amynthas adexilis in North Vietnam. To this end we investigated (1) the microscale organisation of particulate organic matter and pores during the exposure of casts and control aggregates during 12 months and (2) compared it to the potential OM mineralisation during a laboratory incubation.Our results indicated that fresh casts contained significantly more particulate organic matter (POM) than control soil aggregates and field aged earthworm casts. Conversely, the porosity was higher in soil control aggregates than in casts and the porosity of casts tended to increase with their ageing. The analyses of micro-CT images also revealed that POM and Pores contents between casts samples presented strong variabilities even in the youngest casts category. We found, on average, higher mineralisation rates for casts than for controls and a reduction of the OM mineralisation with the ageing of casts. Our results also highlighted a strong positive correlation (r2 = 0.89) between POM contents determined by the segmentation of micro CT images and CO2 emissions from the incubation experiment. We conclude that earthworms impact the microscale organisation of POM and pores in their casts and thereby influence soil OM dynamics