Shannon Weaver Research Articles

Impact of human trampling on biological soil crusts determined by soil microbial biomass, enzyme activities and nematode communities in a desert ecosystem

Human activities disturb Biological soil crusts (biocrusts) in desert areas throughout the world. To assess the effects of trampling on biocrusts and its consequence on sandy soil quality, soil beneath trampling to early-successional cyanobacteria–lichen crusts and late-successional moss crusts was served as the research object in vegetation areas of the Tengger Desert. Trampling intensity was divided into non-trampling, medium trampling and severe trampling of biocrusts. We analyzed changes in soil microbial biomass, enzyme activities and nematode communities one year after trampling biocrust. The results showed that trampling biocrusts reduced soil microbial biomass carbon (C) and nitrogen (N), lowered soil urease, invertase, catalase and dehydrogenase activity, as well as reduced soil nematode abundance, generic richness, Shannon–Weaver index (H′) and Maturity index (MI) in the study areas, and severely-trampled biocrusts caused a strong decline in these parameters (p < 0.05). The declined soil available phosphorus (P), available N, total N and P may be the major factors that cause the observed reduction in soil microbial and nematode parameters. Impact was correlated with trampling intensity or successional stages of biocrusts. The studied soil microbial and nematode parameters were negatively correlated with trampling intensity. Furthermore, soil microbial biomass, the four enzyme activities, nematode abundance and generic richness were significantly greater underneath trampled/untrampled moss crusts than corresponding trampled/untrampled cyanobacteria-lichen crusts, indicating late-successional crusts have a higher tolerance to trampling disturbance compared to early-successional crusts. Overall, these results suggest that trampling biocrusts lead to a degradation of sandy soil quality in desert ecosystems.

Evaluation of optimal straw incorporation characteristics based on quadratic orthogonal rotation combination design

AbstractFor straw incorporation, three crucial factors affect the soil microbial community and various enzyme activities: straw length, amount and burial depth. To analyse the individual and interactive effects of these three factors on the soil microbial community and various enzyme activities, 23 treatments with five levels of the three variables (straw length, amount and burial depth) were applied in a quadratic orthogonal rotation combination design. A comprehensive indicator was constructed that could represent soil microbial functional diversity and enzyme activity by determining the weights of measured indicators and using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS). The results indicated that the soil microbiological indicators have a higher criteria weight than soil enzyme activity indicators. The final weight orders of indicators were as follows: Shannon–Weaver &gt; invertase &gt; Shannon evenness &gt; urease &gt; catalase &gt; McIntosh index &gt; Simpson diversity &gt; phosphatase. The soil comprehensive values constructed by the TOPSIS method are reliable. The optimal combination for the improvement of soil microbial functional diversity and enzyme activity was a straw length of 13–24 cm, burial depth of 10–17 cm and straw amount of 370–650 g/m2.

Microbial diversity and component variation in Xiaguan Tuo Tea during pile fermentation.

Xiaguan Tuo Tea is largely consumed by the Chinese, but there is little research into the microbial diversity and component changes during the fermentation of this tea. In this study, we first used fluorescence in situ hybridization (FISH), next-generation sequencing (NGS) and chemical analysis methods to determine the microbial abundance and diversity and the chemical composition during fermentation. The FISH results showed that the total number of microorganisms ranges from 2.3×102 to 4.0×108 cells per gram of sample during fermentation and is mainly dominated by fungi. In the early fermentation stages, molds are dominant (0.6×102~2.8×106 cells/g, 0~35 d). However, in the late stages of fermentation, yeasts are dominant (3.6×104~9.6×106 cells/g, 35~56 d). The bacteria have little effect during the fermentation of tea (102~103 cells/g, <1% of fungus values). Of these fungi, A. niger (Aspergillus niger) and B. adeninivorans (Blastobotrys adeninivorans) are identified as the two most common strains, based on Next-generation Sequencing (NGS) analysis. Peak diversity in tea was observed at day 35 of fermentation (Shannon–Weaver index: 1.195857), and lower diversity was observed on days 6 and 56 of fermentation (Shannon–Weaver index 0.860589 and 1.119106, respectively). During the microbial fermentation, compared to the unfermented tea, the tea polyphenol content decreased by 54%, and the caffeine content increased by 59%. Theanine and free amino acid contents were reduced during fermentation by 81.1 and 92.85%, respectively.

Testing the impact of environmental change on hunter‐gatherer settlement organization during the Upper Paleolithic in western Iberia

ABSTRACTRecent cross‐disciplinary research in the Iberian Peninsula has revealed a synchronous pattern between rapid climate change and widespread cultural modifications during the Late Paleolithic. The beginning and development of each traditionally defined techno‐complex is thought to be associated with different environmental conditions. A main contrast is put on the impact of cold and arid conditions at the onset of the Last Glacial Maximum (LGM) and its coincidence with the development of blade/flake‐size projectiles and bifacial technologies, against the dominance of bladelet‐size backed points across more temperate and forested environments. Based on the long‐recognized assumption that lithic technology operates within the broader context of Pleistocene human ecodynamics, here we test the hypothesis that climate‐related lithic techno‐typological changes across the Upper Paleolithic are linked to modifications in land‐use patterns and settlement organization. We present statistical analysis comparing the Shannon–Weaver diversity index for retouched stone tool assemblages (used as proxy for site function) and locational parameters of a series of contexts from Central Portugal. The results show a trend of continuity and change between periods, with some of the most important deviations starting at the onset of the LGM, with the Heinrich Event 2 associated with patterns of technological diversification and biocultural expansion.

Nepalese foxtail millet [Setaria italica (L.) P. Beauv.] genetic diversity revealed by morphological markers

Foxtail millet [Setaria italica (L.) P. Beauv.] is among the oldest cereal grains grown from time immemorial in the Himalayan regions of Nepal. However, Nepalese farmers do not have any improved variety officially released due to lack of substantial research in this crop. A total of 41 foxtail millet accessions were characterized using phenotypic or morphological markers at National Agriculture Genetic Resources Centre (Genebank), Khumaltar (1360 m a.s.l.), Lalitpur, Nepal during 2015 summer to enhance the utilization of foxtail millet genetic resources. Seven quantitative and nine qualitative traits were recorded using standard descriptors of foxtail millet to assess the intra-specific diversity. Significant diversity was observed among the accessions as revealed by Shannon–Weaver diversity indices (H′) for quantitative traits and qualitative traits. Six elite landraces in Cluster-4 and Cluster-5 (three from Lamjung district, and one each from Gorkha, Humla and Jumla districts) produced average grain yield of 3136 kg/ha at Khumaltar condition with earlier maturity (average of 89 days), taller height (average of 172 cm) and thicker panicles (average width of 27 mm). These landraces were selected for further evaluation in the farmers’ field of mountain region due to their early maturity, higher yield potential, disease resistance and attractive panicles which could be considered as important genetic resources to develop climate resilient varieties to cope with the adverse effects of climate change.

Genetic diversity of Geoffroea decorticans , a native woody leguminous species from Atacama Desert in Chile

SUMMARY: Geoffroea decorticans (Fabaceae), chanar, is one of the few native tree species that are adapted to the ecologically limiting conditions from Atacama Desert. Despite its considerable value as a crop species, and important medicinal and food properties, the genetic variability of this plant has not yet been evaluated. The aim of this study was to analyze genetic diversity and degree of fragmentation in G. decorticans populations from six provinces in northern Chile. Genetic variability was assessed using eight ISSR and three RAPD primers, generating 97 % and 81 % polymorphic bands, respectively. AMOVA results based on nine populations showed high genetic diversity within populations (65 %) and moderate levels among populations (35 %). Moreover, genetic relationships among individuals provided evidence for the existence of two well defined clusters in the northern and southern regions of the Atacama Desert. A Mantel test showed a significant positive correlation between geographic and genetic distances (r = 0.58) in seven populations, indicating significant isolation-by-distance. Average Shannon Weaver diversity indices showed significantly lower values associated with Pachica, Copiapo river-mouth, Alto del Carmen and Vicuna populations relative to populations from San Pedro, Calama, Azapa and Copiapo. In this work, a combination of ISSR and RAPD methods provided high quality information to evaluate genetic variability, and could be used as an alternative method to identify and distinguish G. decorticans genotypes of interest. This work represents the first attempt to molecular characterization of G. decorticans in Chile, and its significance to future genetic research is discussed.

Evaluation of the Genetic Variation of Cowpea Landraces (Vigna unguiculata) from Western Cameroon Using Qualitative Traits

Characterization of the genetic diversity and analysis of the genetic relationship between accessions of a crop species is a key step in breeding superior cultivars. The main objective of the hereby study was to determine the genetic variation between 30 cowpea accessions collected throughout the eight divisions of the Western Region of Cameroon using qualitative traits. Phenotypic variation of these accessions was evaluated using diversity indices and cluster analyses. A total of twenty qualitative traits were used for the study. Fifteen of them (75%) were polymorphic, displaying each at least two phenotypic classes. The monomorphic characters were growth pattern, leaf color, leaf hairiness, plant hairiness and pod hairiness, each with only one phenotypic class. Results showed a relatively significant level of genetic diversity among the studied cowpea accessions. Overall, the average of the observed and effective number of phenotypic classes per qualitative trait were Na = 2.350 and Ne = 1.828 respectively. The Nei’s genetic diversity and the Shannon weaver diversity index were He = 0.369, ranging from zero (monomorphic trait) to 0.655 (growth habit) and H’ = 0.609, ranging from zero (monomorphic trait) to 0.996 (seed crowding), respectively. The dendrogram constructed from the twenty qualitative traits revealed 05 accessions clusters with the number of accessions in each cluster varying from one to eleven. Information obtained from this study is likely be useful for future cowpea breeding program.

English

Characterization of landraces is central to any conservation measures devised for sweet potato in Malawi. Studies were therefore conducted using seven morphological descriptors and farmers’ indigenous knowledge systems (IKS) to investigate the phenotypical diversity of 286 landraces and 35 introductions of sweet potato from the north, south east and lower Shire. The accessions were planted in a check plot design at Bvumbwe Agricultural Research Station. The results showed that farmers’ knowledge (IKS) is a means for preliminary characterization of accessions as evidenced by elimination of 75 duplicate accessions by 12 farmers. Analysis of variance (ANOVA) showed that all accessions and populations were phenotypically variable (p≤0.01) and Chi-square test of the morphological descriptors used in the study varied significantly among the three eco-geographical areas and among the landraces and introductions (p≤0.05 and p≤0.01), implying high variability of the accessions. However, the accessions clustered at 50% dissimilarity and generally irrespective of eco-geographical origin, signifying some similarity probably due to gene flow. Shannon Weaver Diversity Index (H’) indicated that different traits had different source areas of highest diversity which were significantly different (p≤0.05); nonetheless Shire Valley had the highest mean diversity for all traits (H’=0.67) which was significantly different from the other two populations (p≤0.05) inferring that the lower shire would be ideal for in situ conservation of sweet potato diversity. Key words: Field evaluation, germplasm, phenotype, population, root crop, variability.

Genetic diversity of improved varieties of intraspecific (O. sativa and O. glaberrima) and interspecific (O. sativa × O. glaberrima) rice

Information on genotype diversity and interrelationships is essential for germplasm management, crop improvement and seed production. In this study the diversity of a collection of 36 rice accessions comprising of Oryza sativa L., O. glaberrima Steud. and interspecific rice (O. sativa × O. glaberrima) was assessed using 24 agro-morphological and 27 microsatellite markers. The collection was composed mainly of improved cultivars and a few landraces which are adapted to the upland ecology in West Africa. The average Shannon–Weaver diversity index value (H′) was 0.23. The highest diversity was found in O. sativa group Indica (H′ = 0.32), and the lowest (H′ = 0.18) in O. glaberrima. Interspecific rice had intermediate diversity. There were 321 alleles with an average of 11.9 alleles per locus and an average major allele frequency of 0.29 per locus. The average gene diversity value was 0.81 and polymorphism information content was 0.80 per locus. Diversity indices for interspecific rice were intermediate between O. sativa and O. glaberrima, but closer to O. sativa group Japonica. Accessions comprised of two populations which corresponded to O. sativa group Indica and O. sativa group Japonica. Interspecific rice accessions were dispersed between the two groups.

Shannon–Weaver index as an integrated indicator of metal differentiation in soil and plant samples

The degree of contrast (differentiation) in the distribution of metals in background and contaminated soils is one of the most important geochemical indicators. The Shannon–Weaver index (H) can be a suitable criterion for the distribution of metals in soil and plant samples. A procedure for calculating the Shannon–Weaver index is described. An index scale of five gradations, from no differentiation (Hrel = 1.0–0.9) to very high differentiation (Hrel = 0.3–0.1), is proposed. The background soils in different regions of Russia have low or even no differentiation of metals. Aerial pollution of soils with heavy metals appreciably increases the degree of metal differentiation, especially near the source of pollution. The parameter value decreases with increasing distance from the pollution source, probably due to the mechanical dilution of dust in the large soil volume.

Spatial and Temporal Variations in Environmental Variables in Relation to Phytoplankton Community Structure in a Eutrophic River-Type Reservoir

This study assesses spatial and temporal variation in environmental variables in relation to phytoplankton community size and composition in a typically eutrophic river reservoir (Hai River, northern China). The aim is to identify environmental parameters governing spatial and temporal differences in phytoplankton density and composition. Physicochemical parameters, including nutrient concentrations, were determined in monthly surface water samples from 2015. The average concentration of key eutrophication indexes (i.e., total phosphorous (TP: 0.24 ± 0.11 mg·L−1), total nitrogen (TN: 2.96 ± 1.60 mg·L−1), and Chlorophyll a (Chl a: 38.5 ± 11.5 mg·m−3)) substantially exceeded threshold values for eutrophic streams. Moreover, the eutrophication increased significantly downstream along the river reservoir as a consequence of an increasing fraction of agricultural and industrial land-use in the watershed. 103 phytoplankton species were identified, of which Chlorophyta was the dominated phylum (47 species), followed by Bacillariophyta (23 species) and Cyanophyta (18 species). No spatial difference in species distribution (ANOVA, p &gt; 0.05) were found, while the temporal differences in species composition exhibited significant heterogeneity (ANOVA, p &lt; 0.001). Phytoplankton abundance was highest in early summer (June and July), with maximum values increasing from 1.78 × 108 and 2.80 × 108 cells·L−1 in upstream and middle reaches, respectively, to 4.18 × 108 cells·L−1 furthest downstream. Cyanophyta, also known as Cyanobacteria and commonly referred to as blue-green algal, are known to constitute algae bloom in eutrophic systems. Common species are Microcystis marginata, Microcystis flos-aquae, and Oscillatoria sp. This was the dominant phyla during summer months, especially in the middle and lower reaches of the stream reservoir where it accounted for 88.9% of the phytoplankton community. Shannon weaver index (H’) and Pielous’s evenness index (J’) were extremely low (1.91–2.43 for H’ and 0.39–0.45 for J’) in samples collected from the lower part of the stream during the period of algal bloom, indicating an imbalance in the phytoplankton communities. Canonical correspondence analysis (CCA) indicated that water temperature (WT) and possible pH, along with nitrate (NO3-N) and nitrite (NO2-N), were the most important explanatory parameters in regard to phytoplankton composition. This research provides an understanding of the role of physicochemical water quality parameters in governing algal blooms and phytoplankton composition in river reservoirs.

Functional Diversity of Fungal Communities in Soil Contaminated with Diesel Oil.

The widespread use and consumption of crude oil draws the public’s attention to the fate of petroleum hydrocarbons in the environment, as they can permeate the soil environment in an uncontrollable manner. Contamination of soils with petroleum products, including diesel oil (DO), can cause changes in the microbiological soil properties. The effect of diesel oil on the functional diversity of fungi was tested in a model experiment during 270 days. Fungi were isolated from soil and identified. The functional diversity of fungal communities was also determined. Fungi were identified with the MALDI-TOF method, while the functional diversity was determined using FF-plates made by Biolog®, with 95 carbon sources. Moreover, the diesel oil degradation dynamics was assessed. The research showed that soil contaminated with diesel oil is characterized by a higher activity of oxireductases and a higher number of fungi than soil not exposed to the pressure of this product. The DO pollution has an adverse effect on the diversity of fungal community. This is proved by significantly lower values of the Average Well-Color Development, substrates Richness (R) and Shannon–Weaver (H) indices at day 270 after contamination. The consequences of DO affecting soil not submitted to remediation are persistent. After 270 days, only 64% of four-ringed, 28% of five-ringed, 21% of 2–3-ringed and 16% of six-ringed PAHs underwent degradation. The lasting effect of DO on communities of fungi led to a decrease in their functional diversity. The assessment of the response of fungi to DO pollution made on the basis of the development of colonies on Petri dishes [Colony Development (CD) and Eco-physiological Diversity (EP) indices] is consistent with the analysis based on the FF MicroPlate system by Biolog®. Thus, a combination of the FF MicroPlate system by Biolog® with the simultaneous calculation of CD and EP indices alongside the concurrent determination of the content of PAHs and activity of oxireductases provides an opportunity to achieve relatively complete characterization of the consequences of a long-term impact of diesel oil on soil fungi.

Teorías sistémicas de la comunicación

Systemic theories of communication proceed from a deconstruction of Shannon's and Weaver's mathematical theory and transmission model of communication. Referring to the unresolved question of the identity of a message for different observers they instead develop a selection model of communication. In order to overcome the engineering model of signaling (rather than communication) offered by Shannon and Weaver systemic theories drop the assumption of a given set of possible messages any one message is considered to be selected from, and instead assume that the set of possible messages is to be constructed by the participants in communication as much as the single message then to be selected from that constructed set, also known as the context.

Impact De L’exploitation Artisanale De La Sabliere De Toutsang Sur La Structure Des Communautes De Macroinvertebres Du Cours D’eau Doulahang A Dschang (Ouest Cameroun)

The impact of wastewaters from the Toutsang sandpit (Dschang), both on water parameters and on benthic macro-invertebrate community structure of the Doulahang stream was studied from March 2015 to February 2016 on a monthly basis in three sampling stations named TS1, TS2 and TS3. The physico-chemical analysis were carried out according to standard protocols while the benthic macro-fauna was harvested using a haze net of 30 cm side and 400 μm mesh size. The analysis of physico-chemical parameters revealed that the introduction of wastewater from the sandpit at the TS2 station led to an increase of the temperature, conductivity, total dissolved solids, salinity, suspended matter, turbidity and colour. The wildlife inventory identified 63 taxa divided into 4 phyla, 6 classes, 13 orders and 31 families. The lowest values of the taxonomic richness (18 taxa, against 46 taxa and 47 taxa respectively to stations TS1 and TS3), the Shannon diversity index (2.48 bits / ind.) and the Pielou's evenness (0.62) were observed at station TS2 which received wastewaters from the sandpit. Similarly, the low values of the richness and abundance of the pollutionsensitive groups (Ephemeroptera-Trichoptera-Odonata) were recorded in this station. Significant negative correlations were found between some metrics (total taxonomic richness, taxonomic richness of the Diptera, Richness of Ephemeroptera-Trichoptera-Odonata, Taxonomic richness of insects, Relative abundance of Ephemeroptera-Trichoptera-Odonata, Shannon Weaver diversity index, Pielou's evenness) descriptors of the structure of benthic macro-fauna communities and physico-chemical parameters indicative of physical pollution such as turbidity, suspended matter and colour.

Diversity in proso millet (Panicum miliaceum L.) landraces collected from Himalayan mountains of Nepal

Proso millet (Panicum miliaceum L.) is one of the oldest cereal grains cultivated in the north-western part of Nepal. Not a single proso millet variety has been released so far for cultivation in Nepal. To assess the genetic diversity of proso millet conserved in the National Agriculture Genetic Resources Centre, 42 accessions of proso millet were characterized in Khumaltar (1360 m a.s.l.), Lalitpur in 2015 that were collected from the Humla (1900–2800 m a.s.l.) and Jumla (2300–2600 m a.s.l.) districts of the Western Himalayas of Nepal. Seven quantitative and nine qualitative traits were recorded using standard descriptors. The accessions were found to be diverse using Shannon–Weaver diversity indices (H′) for the quantitative traits of days to heading and maturity, plant height, panicle length, panicle exertion, flag leaf length and grain yield, whereas low diversity was observed for the qualitative traits of leaf sheath colour, flag leaf angle, grain shape, and grain colour, and no diversity was observed for leaf pubescence. The accessions were grouped in five clusters where an accession in Cluster-5 and six accessions in Cluster-4, all from Humla, were found to be high-yielding, early-maturing and of taller plant height. In contrast, 4 accessions in Cluster-2 (3 from Jumla) were low-yielding, late-maturing and of shorter plant height. Accessions H237, H176, H311, H489, H490, H643 and H653, all from the Humla district, performed better in the preliminary evaluation. Although these accessions could be used for future breeding to develop climate-resilient varieties, the genebank could employ an innovative method of using participatory diversity kits to promote farmer selection for immediate benefits.

Variation in virome diversity in wild populations of Penaeus monodon (Fabricius 1798) with emphasis on pathogenic viruses

Marine animals typically harbor a community of viruses, a number of which are known to cause diseases. In shrimp aquaculture, viral pathogens are the principal causes of major economic losses. However, the composition of the viral load of shrimps in wild population is poorly known. In this study, we explored the viral diversity in the microbiome of wild Penaeus monodon collected from six sites in the Philippines, with a view to detecting pathogenic forms. We employed a metagenomic approach via particle-associated nucleic acid isolation, sequence-independent single primer amplification, and pyrosequencing. Virome analysis of shrimp samples from different sites revealed distinct virome profiles, and hence significant differences in diversity, among the various sites based on number of OTUs, Shannon-Weaver Index, and Inverse Simpson Index. Sequences of key shrimp pathogens were detected such as the white spot syndrome virus (WSSV), and Penaeus stylirostris densovirus (PstDV). However, the patterns of distribution of the pathogenic viruses varied; whereas WSSV was found only in three out of six sites and PstDV were found in all but one site. The results also revealed shrimp-associated viruses that have not yet been observed in P. monodon such as avian virus-like, insect virus-like, plankton virus-like and bacteriophage-like sequences. Despite the diverse array of viruses detected in the study, a large proportion remains unidentified (i.e., similarity to sequences in the database was lower than the threshold required for definitive identification), and therefore could represent unexplored virus sequences and viral genomes in the environment.

Evidence for Substrate Influence on Artificial Substrate Invertebrate Communities.

Cobble baskets are frequently used as a tool to measure differences in benthic macroinvertebrate communities between waterbodies; however, underlying differences in substrate type may influence the resultant colonization of baskets, misrepresenting communities. This study tests the hypothesis that cobble basket placement influences the resulting benthic macroinvertebrate community. Cobble basket arrays (n = 4) were deployed in Dog Lake, Saskatchewan, in 2011 (97 d) and 2012 (95 d) on cobble habitats and soft or sandy substrates ∼100 m apart. Baskets placed on cobble substrate had significantly higher Shannon-Weaver diversity relative to those placed on soft substrate in both years, and higher % EPT (Ephemeroptera Plecoptera Trichoptera) in 2011, but total density was not significantly different. Nonmetric multidimensional scaling revealed that the community was different between both treatments, characterized by higher densities of Gammarus lacustris Sars in baskets placed on soft sediment in both years, higher densities of Aeshna sp. and Mystacides sp. on cobble substrate in 2011, and higher densities of Helobdella stagnalis (L.) and Glossophinia complanata (L.) on cobble substrate in 2012. The results were consistent with the hypothesis that baskets placed on cobble substrate versus soft substrate will result in differing community colonization. The resulting recommendation for monitoring and assessment using cobble baskets in lakes is that baskets be placed on comparable substrate type when comparing between lakes, and that cobble beds be chosen as a more appropriate substrate for deployment, as the added habitat complexity of baskets on soft sediment may act as an attractant and not reflect the true community composition of that habitat.

Dynamics of endophytic and epiphytic bacterial communities of Indian cultivated and wild rice (Oryza spp.) genotypes

Abstract Metabolic and structural profiles of the epiphytic, endophytic and rhizoplanic bacterial communities of three Indian cultivated rice (Oryza sativa var. Sabita/Swarna/Swarna-Sub1) and one wild rice (O. eichingeri) genotypes differing in life span and cultural practices viz. hydrology and fertilizer doses were analyzed through Biolog-Ecoplate assay, and culture-dependent and culture-independent approaches (denaturing gradient gel electrophoresis-DGGE). Overall microbial population dynamics and diversity was more in the wild genotype than the cultivated ones viz. wild > Sabita > Swarna and Swarna-Sub1. Microbial community metabolism was more in the roots according to wild > Sabita > Swarna and Swarna-Sub1. The DGGE profile of the endophytes of Swarna roots was distinct from those of the other parts of different rice genotypes. The microbial communities in different parts of the cultivated varieties produced higher Shannon–Weaver and lower Simpson's indices, but lower McIntosh index than those of the wild species. The principal components reflected similar trends of effects of carbohydrate and phenolic compounds in Biolog-ecoplate assay which suggested that the substrates would influence the assay of the microbial communities. Broadly, microbial dynamics in different parts of the four rice genotypes represent the structural differences of the phytonic microbial communities which would help to understand the interaction of microbes with different categories of rice genotypes.

Effect of Bioaugmentation by Bacterial Consortium and Methyl-β-cyclodextrin on Soil Functional Diversity and Removal of Polycyclic Aromatic Hydrocarbons

ABSTRACTThe low biological effectiveness of polycyclic aromatic hydrocarbons (PAHs) is the main limiting factor of in-situ bioremediation of PAH-contaminated soil. The purpose of the present study was to assess the effects of methyl-β-cyclodextrin (MCD) and microbial consortia on the PAHs degradation rate and microbial ecology and functional diversity and stability in soil. The results show that MCD and microorganisms significantly increased the degradation rate of pyrene and benzo[a]pyrene by 30.1% and 9.1%, respectively, (p < 0.05) after 4 weeks. The average well color development (AWCD) values and diversity indices of bioaugmentation (B) and MCD- and bacterial-assisted bioaugmentation (MB) were significantly higher than that in control (CK). The Shannon–Weaver index (H) and McIntosh index (U) in the MB treatment were significantly higher than those observed in other treatments, which indicated that its species richness and individuals were distributed evenly. The soil microbial activity and community structure were the most abundant in the MB treatment. Compared to the CK treatment, MB significantly promoted soil dehydrogenase activity (DHA) and fluorescein diacetate hydrolysis (FDAH) enzyme activity, which were increased by 96.3% and 994.3%, respectively. According to the results of principal component analysis, the physiological functions of microbial communities in the MB and B treatments were different from the other treatments. Therefore, the combination of the microorganisms with MCD can stimulate the remediation efficiency of PAHs and the physiological functions of microbial communities.

Effects of biochars on the bioaccessibility of phenanthrene/pyrene/zinc/lead and microbial community structure in a soil under aerobic and anaerobic conditions

The immobilization of co-contaminants of organic and inorganic pollutants by biochar is an efficient remediation strategy. However, the effect of biochar amendments on the bioaccessibility of the co-contaminants in dry versus flooded soils has rarely been compared. In batch experiments, bamboo-derived biochar (BB) had a higher sorption capacity for phenanthrene (Phe)/pyrene (Pyr)/zinc (Zn) than corn straw-derived biochar (CB), while CB had a higher sorption capacity for lead (Pb) than BB. After 150days of incubation, the amendments of 2% CB, 0.5% BB and 2% BB effectively suppressed the dissipation and reduced the bioaccessibility of Phe/Pyr by 15.65%/18.02%, 17.07%/18.31% and 25.43%/27.11%, respectively, in the aerobic soils. This effectiveness was more significant than that in the anaerobic soils. The accessible Zn/Pb concentrations were also significantly lower in the aerobic soils than in the anaerobic soils, regardless of treatments. The Gram-negative bacterial biomass and the Shannon–Weaver index in the aerobic soil amended with 2% CB were the highest. The soil microbial community structure was jointly affected by changes in the bioaccessibility of the co-contaminants and the soil physiochemical properties caused by biochar amendments under the two conditions. Therefore, dry land farming may be more reliable than paddy soil cultivation at reducing the bioaccessibility of Phe/Pyr/Zn/Pb and enhancing the soil microbial diversity in the short term.