Micromorphlogy of recent and buried soils in a semi-arid region of northwestern India

Profiles of four recent soils and of eleven soils buried under archaeological sites of known ages were investigated in an area between the Ghaggar Valley and the northern piedmont of the Arawalli Hills in northwestern India. The principal approach was through study of micromorphology. Data were also obtained on mineralogies of several size fractions.Characteristics shared by the recent and buried soils indicate that essentially the same processes operated in their formation. The oldest soils are buried under Protohistoric sites and thus were formed at least 5000 years ago. They are developed on sediments rich in sand-sized mica flakes which indicate an alluvial origin. Others are buried beneath historic sites with ages ranging from 500 B.C. to 1500 A.D. These soils and the recent ones have a silt fraction low in mice. Major features of both buried and recent soils are attributed to biological activity, reflected in extensive channeling and additions of excrements throughout profiles. Local distribution of clay, silt and carbonates indicates translocation of these components. Furthermore, the forms of calcitic features indicate modifications of various kinds. Evidence of biological activity as expressed in characteristics of the soils becomes progressively weaker from older to younger profiles. Soil development seems to have weakened over that period as well. These changes are correlated with the decline with time in the proportions of mica flakes in coarse fractions. The decline is attributed to lack of alluvial sedimentation since the Protohistoric period and to greater transport and winnowing of sediments by wind. We believe this has reduced fertility of the soils formed during the last 4000 years.     

Laccase and phosphatase activities of the dominant ectomycorrhizal types in a lowland oak forest

The year-round dynamics of laccase and acid phosphatase activities of ectomycorrhizas (EM) were monitored in an oak forest, with a microplate photometric method using individual EM root tips. Among the most frequent and abundant EM morphotypes, those of Lactarius quietus and Cortinarius anomalus showed a peak of laccase activity in spring, while those of Xerocomus chrysenteron displayed highest laccase activities in summer and autumn. In comparison, less seasonal differences were observed in EM acid phosphatase activity. This suggests that the different EM types within the EM community perform complementary functions depending on season.     

Soil niche effect on species diversity and catabolic activities in an ectomycorrhizal fungal community

The species of an ectomycorrhizal (ECM) community were investigated in a temperate oak forest by morphotyping and ITS rDNA sequencing. Thirty-six ECM morphotypes were found at the site. The niche effect (as organic soil, mineral soil or dead woody debris artificially introduced in the soil) on the ECM community structure and on the potential catabolic activities of the most abundant morphotypes was studied. The morphotypes in each niche were subjected to enzymatic tests developed for hydrolytic and oxidative enzymes involved in the decomposition of organic compounds. The ECM community structure varied widely depending on the soil horizon or habitat patch. The species richness was higher in the A1 horizon than in the other niches. Different ECM species had different activity patterns for the eight enzymatic tests while co-occurring in the same niche. Catabolic activities also changed within species between niches. Dead woody debris were extensively colonized by two saprotrophic fungi (Megacollybia platyphylla and Armillaria sp.) and, in this particular niche, ECM morphotypes predominantly belonged to the genera Lactarius and Tomentella. These morphotypes showed high chitinase activities. This study suggested also that some ECM fungi could obtain nutrients via the chitin degradation of dead or live saprobes.     

Relation between oak tree phenology and the secretion of organic matter degrading enzymes by Lactarius quietus ectomycorrhizas before and during bud break

The ectomycorrhizas (ECM) formed by Lactarius quietus, an ECM fungus specifically associated with Quercus spp., are abundant all the year long. Root and stem growth, beginning before bud break in oak, are strong carbon sinks partially fulfilled with carbohydrate reserves. We hypothesized that L. quietus contributes to providing trees with carbon at bud break through enzymatic activities before photosynthesis begins. Activities of eight secreted enzymes (xylosidase, glucuronidase, cellobiohydrolase, β-glucosidase, N-acetyl-glucosamine, leucine aminopeptidase, acid phosphatase and laccase) relevant to carbon cycling and the release of phophorus and nitrogen from soil organic matter were measured on L. quietus ECMs before, during and after the bud break. Phenological, climatic and pedoclimatic parameters were also measured. Laccase, glucuronidase, cellobiohydrolase and β-glucosidase activities proved to be significantly related to tree reactivation and climate. All these activities can help the formation of new tissues by supplying carbon. L. quietus can behave saprotrophically, using soil organic matter as substrate. This is consistent with the hypothesis that it provides the oak trees with carbon when demand is high and photoassimilates are not yet available.     

Assessment of “discreet” vertebral abnormalities, bone mineralization and bone compactness in farmed rainbow trout

The present study aimed to evaluate the importance of “discreet” vertebral abnormalities in normally-shaped rainbow trout in relation to vertebral bone condition in French fish farms. A total of 373 trout (262 ± 2 mm in total length) from 20 fish farms sampled were studied. The fish were radiographed and the axial skeleton examined for vertebral abnormalities. Vertebrae from the middle axial region (V32-38) were selected to evaluate vertebral bone condition. Bone mineralization (BM, %) was estimated by the ratio of ash and dry weight. Bone compactness (BC,%) was measured using Bone Profiler 3.23 images software on digitized radiographs of transverse sections (125 ± 10 μm). Statistical analyses were performed to test the relationships between the occurrence of vertebral abnormalities, and BM and BC. The occurrence of affected trout ranged from 0 to 55% depending on the farm. Trout displayed vertebrae with low BM (< 54.6%) and low BC (< 28.1%) in 40% and 55% of the farm, respectively. No relationships were observed between bone condition parameters (BM, BC) and the occurrence of vertebral abnormalities. These results could be explained by a wide and variable plastic response of bone characters (i.e., vertebral abnormalities, BM and BC) to the various rearing conditions in the fish farms sampled.     

Secreted enzymatic activities of ectomycorrhizal fungi as a case study of functional diversity and functional redundancy

• Introduction   

Many studies deal with taxonomic diversity (TD) or estimation of functional traits of ectomycorrhizal communities. However, to our knowledge, none of them has ever tried to calculate the functional diversity (FD) of those communities, which is of critical importance for the diversity and reliability of nutrient supply to the tree.     

Protective role of murine norovirus against Pseudomonas aeruginosa acute pneumonia

The murine norovirus (MNV) is a recently discovered mouse pathogen, representing the most common contaminant in laboratory mouse colonies. Nevertheless, the effects of MNV infection on biomedical research are still unclear. We tested the hypothesis that MNV infection could alter immune response in mice with acute lung infection. Here we report that co-infection with MNV increases survival of mice with Pseudomonas aeruginosa acute lung injury and decreases in vivo production of pro-inflammatory cytokines. Our results suggest that MNV infection can deeply modify the parameters studied in conventional models of infection and lead to false conclusions in experimental models.     

Physical properties of structural soils containing waste materials to achieve urban greening

Purpose

The densification and expansion of urban areas will increase the streams of waste materials such as bricks, concrete and street sweeping waste. In parallel, green areas offer the potential to overcome many challenges that face growing/expanding cities but require the use of large amounts of natural resources such as natural topsoil and aggregates. In this work, various waste materials mixed with organic debris are tested for greening applications in urban environments as an alternative to the consumption of natural resources.

Materials and methods

Five combinations of artefacts were studied either as “growing material” (i.e. dedicated to plant growth) or “structural material” (as support for traffic). These constructed Technosols were studied in situ in lysimeters under two sets of contrasting climatic conditions at two sites in France (Angers, oceanic climate, and Homécourt semi-continental climate). They were planted with trees (Acer platanoides) and with ryegrass (Lolium perenne L.).

Results and discussion

Compared to natural soils, the constructed Technosols exhibited high porosities and highly saturated hydraulic conductivities (up to 0.76 m³ m^?3, and to 34.74 cm h^?1, respectively). The physical properties–i.e. macroporosity and microporosity–of these artificial soils revealed high water supply for plants, with available soil water ranging from 0.5 to 2.9 mm cm^?1. Tree and ryegrass roots were able to grow in the entire soil volume available in the lysimeters. Organic matter nature and soil pH conditions appeared to be the main drivers of plant development.

Conclusions

Constructed Technosols are suitable for vegetation growth and constitute a valuable alternative to the consumption of natural arable earth for urban greening applications, e.g. gardens, parks, and tree lines. Furthermore, they can provide high levels of relevant ecosystem functions in cities such as water retention and infiltration, plant settlement, carbon sequestration and even biodiversity habitats.

     

Simple microplate assays to measure iron mobilization and oxalate secretion by ectomycorrhizal tree roots

The ability of ectomycorrhizal (ECM) fungi to mobilize soil inorganic nutrients has been well documented for a diversity of species. However, most of these studies were performed with tree seedlings or fungal cultures, making them hardly comparable. We propose here three microplate assays to compare iron chelation, free iron uptake and oxalate production by ECMs freshly sampled in mature forest ecosystems. These assays proved to be sensitive enough to detect significant differences between two common ECM types. Lactarius subdulcis was less efficient than Xerocomus sp. for accessing to free or complexed iron, but produced 100 times more oxalate. These preliminary results open the way to study the contribution of ECM communities to nutrient cycling in forest ecosystems.