Abstract:Soil health is the central theme of sustainable agricultural development. Soil microorganisms cooperatively drive the soil life system by regulating soil ecological functions, environmental functions and immunologic functions, which are the keys to maintaining soil health. Understanding the mechanisms of soil microorganisms mediated soil health is essential to effectively utilize these core microorganisms to maintain and improve soil health. Thus, soil functions, such as soil carbon cycling, nutrient cycling, soil structure regulation, plant disease and insect inhibition and contamination control mediated by soil microorganisms are reviewed to summarize their roles in maintaining or enhancing soil health. Furthermore, as a sensitive indicator of soil health, the roles of soil microorganisms in soil health indication and warning were also studied. Research about mining, construction and application of the core microbiome information database that drives the specific function of soil health and multiple biological processes should be strengthened in the future. This will help to provide a scientific basis for improving the function of agricultural soil ecosystems using soil microorganisms, maintaining soil health and soil sustainable development.

Abstract:Viruses are non-cellular biological entities, simple in structure, composed of proteins outside and nucleic acids inside. The total number of virus-like particles (VLPs) in the Earth biosphere was estimated about 4.80×1031, which is overwhelmingly higher than that of organisms with cellular structure therein. Soil is an important reservoir of viruses, consisting mainly of bacteriophages (phages) that are able to infect prokaryotes. Metadata analysis shows that the number of the viruses in soil is closely related to the number of their host cells and certain soil physical and chemical properties. Although researchers in this aspect have realized that the viruses in soil may play an important role in regulating composition of soil microbial communities, thus influencing recycling of soil elements, promoting microbial evolution, and affecting the health of animals and plants, as well as human beings. However, due to high adsorbability of the soil virus particles and heterogeneity of the soil, as well as the limitation of research methods and analysis platforms, the cognition of and the attention paid to the viruses in soil in the current researches lags far behind those in the environments of flowing waterbodies, like river, oceans, etc.. Among the soil viral metagenomes, a huge number of genes remain undetermined in sequence, source and function and hence are sorted into the catalogue of unknown genes. Consequently, viruses in soil are deemed as biological ‘dark matter’ and the largest unexploited gene treasure trove. In this paper, a brief introduction to morphology, abundance, existing form and diversity of the viruses in soil, a review of the methods and their limitations in using molecular marker genes, random amplified polymorphic DNA-PCR and metagenomic analysis techniques to parse diversity of the viruses in soil, and then discussions about validated and potential ecological functions of the viruses were presented. In the end, directions of the researches in future on viruses in soil that should be strengthened were brought forth, stressing the importance of coupling studies on soil viruses and soil microorganisms in future studies to reveal ecological functions of the soil.

Abstract:Earthworms (Eisenia fetida) as subject in the test are exposed to chlorpyrifos of a sub-lethal dose for 8 weeks in artificial soil．Effects of the exposure on SOD, CAT, and GSH-Px activities in earthworms were observed. Results show that the compound suppressed the activities significantly. So the enzymes of the anti-oxidizing defense system of earthworms can be cited as indicators of chlorpyrifos toxicity. Besides the commonly used ecological toxicity indexes, such as LC50, oviposition rate and hatching rate, the activities of the antioxidases, were closely related to the toxic effect of the pesticide. However, the enzymes varied in sensitivity to the chemical． SOD and GSH-Px were more sensitive than CAT．Therefore, in diagnosing ecological toxicity, it is advisable to have different indices form a mutually supplementary indicator system to improve the sensitivity and efficiency of pollution identification and long term diagnosis．

Abstract:Soil organic matter (SOM) plays a vital role in long-term carbon sequestration in forest soil systems. A stable SOM pool consists of various recalcitrant biomacromolecules which mainly come from plants, animals, fungi and bacteria. These plant- or microbe-derived organic matters in the soil have their own source-specific natural biomarkers. A review is presented here of the advancement in the research on application of plant biomarkers to the study on soil carbon recycling in the past two decades, briefing on application of plant biomarkers to determination of plant sources and decomposition degree of SOM, and introducing application of stable isotopes of plant biomarkers to quantitatively estimating cycling time of SOM. Besides, the review also introduces in detail methods for chemical analysis of plant biomarkers in the soil. Therefore, the review may serve as reference for future studies on application of plant biomarkers to researches on SOM in China.

Abstract:Soil collembolan is deemed as an epitome of soil invertebrate and medium-sized soil animals because of its abundance in species and hugeness in biomass.So it plays an important role and demonstrates its unique advantages over other soil animals in the assessment of heavy metal contamination of environment; This review first briefly summarizes some methodological systems and major parameters (community structures, species character, survival,growth,reproduction, metallothionein, and enzyme) used in the study of ecotoxicology and other related biomarkers in applying Collembola in ecological risk assessment of polluted soils.In the end of this review, problems existing in and prospects of the application of Collembola in the ecological risk assessment of heavy metal contamination of soils are analyzed and discussed.

Abstract:Biochemical responses of earthworm (Eisenia fetida) to fluoranthene were studied and cited as biomarkers for monitoring PAHs-contamination of sublethal concentration in the soil.Earthworms were exposed to soils contaminated with different concentrations of fluoranthene (60,120,240,480,960μg kg-1 and CK).After exposure for 1,3,7 and 14 days,earth-worms were collected for analysis of contents of total cytochrome P450 and MDA and the activities of glutathione-Stransferase(GST),superoxide dismutase (SOD),peroxidase (POD) and catalase (CAT) in the guts.Results indicate that within the range of concentrations in the test,fluoranthene triggered varying responses from biochemical enzymes in the guts of the earthworms,particularly from P450 in content,and from SOD and POD in activity but not as significantly from GST,CAT and MDA.The research also revealed that the effect of duration of the exposure was stronger than that of dosage limited within the range of sublethal concentrations on the biochemical responses.As biochemical sensitivity to the pollutant varies from enzyme to enzyme,it is necessary to use a combined multitime multi-index diagnostic method in diagnosing ecotoxicity of the pollutant in soil,with special stress on sensitivity and effectiveness of the indicators of exposure to the pollutant.

Abstract:The ways in which earthworms perform as bioindicators of soil pollution are reviewed as follows:(1)Earth-worm population in contaminated sites reflects the degree of soil pollution as a whole;(2)For ecotoxicologial risk assessment, earthworms serve as an important indicator for potential pollutants damaging the soil eco-system;(3)Earthworms act as an early warning system in monitoring changes in soil pollution.The main mechanisms of earthworms.resistance to metal pollutants are also elaborated:(1)its lipid ant ioxidative enzyme system helps relieve the stress of oxidation;(2)Compartment and immobilization of metals;(3)Process of chelating and detoxicification;(4)Lysosome and cellular plasmid are activated to restrain activity of heavy metals.Meanwhile,the potential of earthworms to enhance soil bioremediation is discussed and it is believed that earth-worms do so by improving physical and chemical characteristics,activating microbes,changing bioavailability of pollutants in soil.