Chemical and Microbiological Parameters of Paddy Soil Quality as Affected by Different Nutrient and Water Regimes

A field experiment was conducted from 1999 to 2002 to compare and evaluate the effects of nutrient and water regimes on paddy soil quality by investigating soil chemical and microbiological parameters. Four nutrient regimes, a control, chemical fertilizers only (CF), chemical fertilizers with swine manure (SM), and chemical fertilizers with wheat straw (WS), and two soil moisture regimes, continuous waterlogging (CWL) and alternate wetting and drying (AWD), were investigated. With SM and WS total organic carbon and total nitrogen in the paddy soil were significantly higher (P < 0.05) than those with CF. A similar effect for organic amendments was observed in the soil light fraction organic C (LFOC), water-soluble carbohydrates (WSC), and water-soluble organic C (WSOC). CWL, in particular when swine manure was incorporated into the paddy soil, markedly decreased soil redox potential (Eh) and increased total active reducing substances (ARS). Meanwhile, as compared to CF, SM and WS significantly (P < 0.05) increased soil microbial biomass C (MBC) and mineralizable carbon, with differences in AWD being higher than CWL. In addition, SM and WS treatments significantly (P < 0.05) improved rice above-ground biomass and grain yield, with AWD being greater than CWL. Thus, for ecologically sustainable agricultural management of paddy soils, long-term waterlogging should be avoided when organic manure was incorporated into paddy soil.

Characterization of Citrus tristeza virus Isolates by Indicators and Molecular Biology Methods

Citrus tristeza virus （CTV） exists in citrus as a large number of distinct strains differing in biological characters. The control strategies such as mild strains cross protection （MSCP） require a clear understanding of the characterization of CTV. For better understanding of the structure of CTV population and the relationship between molecular and biological characterization, 72 CTV samples collected from five provinces in China were studied, using biological indexing, p25/Hinf I restriction fragment length polymorphism （RFLP）, multiple molecular markers, and bidirectional RT-PCR assay. The mixture of severe stem pitting isolates was found to be dominant in the field. CTV isolates with p25/Hinf Ⅰ RFLP group 3 and p23/BD-PCR group Ⅰ, Ⅲ were the main cause of epidemics, and most CTV isolates were found to be the mixture of T30 and VT genotypes. More accurate identification of strain mixtures in the field and better understanding of the biological traits of the isolates may be achieved by applying the three molecular detection methods simultaneously.

Soils Typology and Floristic Diversity of the Forest of the“Cite Scientifique”of Brazzaville,Congo

A study of the typology of soils and floristic diversity was carried out in the forest of the “Cité Scientifique” of Brazzaville. The study aimed to assess the influence of soil cover on the distribution of taxa. The study covers 18 plots of 625 m2 each, distributed in different soil profiles. The floristic inventory concerns the measurement of diameter of trees with dbh ≥ 10 cm and the counting of herbaceous and shrubs of dbh < 10 cm. The floristic composition reveals a total of 129 plant species distributed in 48 families dominated by Fabaceae and a preponderance of pioneer taxa. The Jaccard coefficients of similarity reveal a low degree of homology of woody plots, whereas for the flora as a whole, the floristic composition is heterogeneous. The Shannon biological diversity index of ligneous varies from 0.6 to 2, against a maximum diversity of 0.69 to 3. The Pielou index of ligneous (0.5 to 0.9) does not reveal any dominance. Soil cover consists of ferrallitic and podzol soils. Their texture is sandy, weakly structured, fragmentary polyhedral throughout the profile, but lumpy and/or nuciform at the surface and sub angular in depth. The porosity decreases proportionally with the depth and thickness of the horizons. The floristic analysis presents an ecosystem with a low degree of diversification for a high floristic richness. The preponderance of anthropization markers is a proof of its very advanced state of disturbance. The study shows that soil cover does not influence the distribution of timber. Indeed, the establishment and development of pioneer species are less prone to soil properties.

Response of Epilithic Diatom Communities to Downstream Nutrient Increases in Castelhano Stream,Venancio Aires City,RS,Brazil

The Castelhano Stream Hydrographic Basin, located in the city of Venancio Aires, RS, Brazil, shows an area of 675.3 km2, highlighting the Castelhano Stream as their main water course. The stream is the main responsiblity for the local water supply;however, there are no published studies in the literature regarding their water quality. In this context, the present research aimed to assess the water quality of Castelhano Stream in terms of organic pollution and eutrophication, applying the Biological Water Quality Index (BWQI), which uses epilithic diatoms communities as bioindicators. Biological samples were collected at three sampling stations along the stream in the months of September, November and December 2012. The results showed 81 identified species, distributed in 30 genera. The water pollution levels detected ranged from “strong” (66.7%) and “very strong” (33.3%), with differences in species composition between sampling stations. The sampling station S1 in the upper reaches was characterized by the presence of indicative species of acidophilus and lentic environments with large amounts of organic matter. The sampling stations S2 and S3, in the intermediate and lower reaches, respectively, showed a substitution of species in the community, with the presence of highly tolerant taxa to organic pollution and eutrophication. The high pollution levels detected along the basin are related to the nutrients and high organic load originating from livestock, domestic and industrial waste, as well as excess fertilizers and agricultural inputs used in farming. The results demonstrate the necessity to implement mitigation measures to contain the processes of organic pollution and eutrophication detected due to the dangers offered to public health and the environment.

How does the brown mussel Perna perna respond to environmental pollution?A review on pollution biomarkers

The brown mussel Perna perna(Linnaeus,1758)is a valuable resource for aquaculture in tropical and subtropical coastal regions.It presents desirable characteristics for biomonitoring,including being sessile,widely distributed and abundant,and is a filter-feeder able to accumulate several classes of pollutants(e.g.,metals,hydrocarbons,among others).Mussels’biological responses to pollution exposure can be measured as biomarkers,which include alterations ranging from molecular to physiological levels,to estimate the degree of environmental contamination and its effects on biota.This full review compiles two decades(2000–2020)of literature concerning biological effects on P.perna mussel caused by environmental pollutants(i.e.,metals,hydrocarbons,and emerging pollutants),considering environmental and farm-based biomonitoring.Biochemical markers related to mussels’oxidative status were efficient for the biomonitoring of metals(i.e.,antioxidant enzymes associated with oxidative damage in biomolecules).Genotoxicity and cytotoxicity indicators(i.e.,comet,micronucleus,and neutral red assays)provided a depiction of hydrocarbon contamination.The neutral red assay gave a time-concentration cytotoxic response to a wide range of pollutants,including emerging pollutants(e.g.,pharmaceuticals and biocides)and hydrocarbons.Perna perna hemocyte parameters provided a useful approach for biocide biomonitoring.This paper summarizes useful biomarkers from molecular to physiological levels in this mussel species used to identify and quantify the degree of coastal pollution.An integrated biomarker analysis may provide a way to overcome possible biomarker variations and assess multi-polluted sites.Nevertheless,it is necessary to investigate biomarker variations according to natural factors(e.g.,season and gonad maturation stage)to standardize them for trustworthy biomonitoring.