Ocean acidification drives gut microbiome changes linked to species-specific immune defence.

Ocean acidification (OA) has important effects on the intrinsic phenotypic characteristics of many marine organisms. Concomitantly, OA can alter the extended phenotypes of these organisms by perturbing the structure and function of their associated microbiomes. It is unclear, however, the extent to which interactions between these levels of phenotypic change can modulate the capacity for resilience to OA. Here, we explored this theoretical framework assessing the influence of OA on intrinsic (immunological responses and energy reserve) and extrinsic (gut microbiome) phenotypic characteristics and the survival of important calcifiers, the edible oysters Crassostrea angulata and C. hongkongensis. After one-month exposure to experimental OA (pH 7.4) and control (pH 8.0) conditions, we found species-specific responses characterised by elevated stress (hemocyte apoptosis) and decreased survival in the coastal species (C. angulata) compared with the estuarine species (C. hongkongensis). Phagocytosis of hemocytes was not affected by OA but in vitro bacterial clearance capability decreased in both species. Gut microbial diversity decreased in C. angulata but not in C. hongkongensis. Overall, C. hongkongensis was capable of maintaining the homeostasis of the immune system and energy supply under OA. In contrast, C. angulata's immune function was suppressed, and the energy reserve was imbalanced, which might be attributed to the declined microbial diversity and the functional loss of essential bacteria in the guts. This study highlights a species-specific response to OA determined by genetic background and local adaptation, shedding light on the understanding of host-microbiota-environment interactions in future coastal acidification.

Brevibacillus marinus sp. nov., a thermophilic bacterium isolated from deep sea sediment in the South China Sea.

A novel thermophilic bacterium, designated SCSIO 07484T, was isolated from marine sediment sampled in the South China Sea. Growth occurred at 30-60 °C, pH 6.0-8.0 and in the presence of 0-3 % (w/v) NaCl. Cells of strain SCSIO 07484T were rod-shaped and flagellum-forming. No soluble pigment was observed. The phylogenetic analysis of the 16S rRNA gene sequences indicated that SCSIO 07484T belonged to the family Paenibacillaceae and clustered with members of the genus Brevibacillus in the phylogenetic trees with less than 96.2 % similarities. The cell wall contained meso-diaminopimelic acid. Whole-cell hydrolysates contained arabinose, glucose and ribose. The predominant menaquinone was MK-7. Major fatty acids were iso-C16 : 0, iso-C15 : 0, C16 : 0 and iso-C14 : 0. Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phosphatidylmonomethylethanolamine were its diagnostic polar lipids. The whole genome size of strain SCSIO 07484T was 4 079 826 bp with a DNA G+C content of 56.2 mol%, including one circular chromosome of 3 978392 bp and one plasmid of 101434 bp. Based on the polyphasic analysis of strain SCSIO 07484T, it is considered to represent a novel species of the genus Brevibacillus, for which the name Brevibacillus marinus sp. nov. is proposed with the type strain SCSIO 07484T (=DSM 106769T=CGMCC 1.15814T).

Diversity and Distribution of Uncultured and Cultured Gaiellales and Rubrobacterales in South China Sea Sediments.

Actinobacteria are ubiquitous in marine ecosystems, and they are regarded as an important, underexplored, potential pharmaceutical resource. The orders Gaiellales and Rubrobacterales are deep taxonomic lineages of the phylum Actinobacteria, both are represented by a single genus and contain only a few species. Although they have been detected frequently by high-throughput sequencing, their functions and characteristics in marine habitats remain unknown due to the lack of indigenous phenotypes. Here, we investigated the status of the orders in South China Sea (SCS) sediments using culture-independent and culture-dependent methods. Gaiellales is the second-most abundant order of Actinobacteria and was widely distributed in SCS sediments at water depths of 42-4,280 m, and four novel marine representatives in this group were successfully cultured. Rubrobacterales was present at low abundance in energy-limited marine habitats. An isolation strategy for Rubrobacterales from marine samples was proposed, and a total of 138 mesophilic Rubrobacterales strains were isolated under conditions of light and culture time combined with high-salinity or low-nutrient media. Marine representatives recovered in this study formed branches with a complex evolutionary history in the phylogenetic tree. Overall, the data indicate that both Gaiellales and Rubrobacterales can adapt to and survive in extreme deep-sea environments. This study lays the groundwork for further analysis of the distribution and diversity of the orders Gaiellales and Rubrobacterales in the ocean and provides a specific culture strategy for each group. The results open a window for further research on the ecological roles of the two orders in marine ecosystems.

Miltoncostaea marina gen. nov. sp. nov., and Miltoncostaea oceani sp. nov., a novel deep branching phylogenetic lineage within the class Thermoleophilia isolated from marine environments, and proposal of Miltoncostaeaceae fam. nov. and Miltoncostaeales ord. nov.

Two novel marine actinobacteria, designated as SCSIO 60955T and SCSIO 61214T, were isolated from deep-sea sediment samples collected from the South China Sea. The cells of these organisms stained Gram-negative and were rod shaped. These strains were aerobic, and catalase- and oxidase-positive. Optimal growth occurred at 28 °C and pH 7 over 14 days of cultivation. Both strains possessed phospholipids and phosphoglycolipids. The main menaquinone was MK-7. The major fatty acid was C16:0. The peptidoglycan structure was type A1γ' (meso-Dpm). Analysis of genome sequences revealed that the genome size of SCSIO 60955T was 3.37 Mbp with G + C content of 76.1%, while the genome size of SCSIO 61214T was 3.67 Mbp with a G + C content of 74.8%. The ANI and 16S rRNA gene analysis results showed that the pairwise similarities between the two strains were 73.4% and 97.7% and that with other recognized Thermoleophilia species were less than 69.1% and 87.8%, respectively. Phylogenetic analysis of the 16S rRNA gene sequences showed that strains SCSIO 60955T and SCSIO 61214T were separately clustered together and formed a well-separated phylogenetic branch distinct from their most related neighbor Gaiella occulta. Based on the data presented here, these two strains are proposed to represent two novel species of a novel genus, for which the name Miltoncostaea marina gen. nov., sp. nov., with the type strain SCSIO 60955T (=DSM 110281T =CGMCC 1.18757T), and Miltoncostaea oceani sp. nov., with the type strain SCSIO 61214T (=KCTC 49527T =CGMCC 1.18758T) are proposed. We also propose that these organisms represent a novel family named Miltoncostaeaceae fam. nov. of a novel order Miltoncostaeales ord. nov.

Rubrobacter tropicus sp. nov. and Rubrobacter marinus sp. nov., isolated from deep-sea sediment of the South China Sea.

Two novel Gram-stain-positive bacteria, designated as SCSIO 52909T and SCSIO 52915T, were isolated from a deep-sea sediment sample collected at about 3448 m water depth of the South China Sea. Phenotypic, chemotaxonomic and genomic characteristics were investigated. These strains were aerobic and tested positive for catalase activity, oxidase activity and nitrate reduction. Optimal growth occurred at 28 °C, pH 7 and 3% salinity over 14 days cultivation. Its peptidoglycan structure was type A3α (l-Lys-l-Ala) and the only menaquinone was MK-8. Both strains possessed diphosphatidylglycerol, phosphatidylglycerol, an unidentified phosphoglycolipid, an unidentified glycolipid and an unidentified phospholipid. Their major fatty acids differed, but both contained iso-branched components of C16 : 0 12-methyl. Genome sequencing revealed two large genomes of 4.58 Mbp with G+C content of 67.0 mol% in SCSIO 52909T and of 4.42 Mbp with G+C content of 69.1 % in SCSIO 52915T. The two novel strains encoded genes for metabolism that are absent in most other Rubrobacter species, and possessed many more gene copy numbers of alkaline phosphatase and thioredoxin reductase. Results of gANI and 16S rRNA gene analyses suggested that the two strains represent two new species, with 74.9, 95.0 % pairwise similarity between each other, and less than 74.3 and 93.5 % to other recognized Rubrobacter species, respectively. In the phylogenetic analysis, strains SCSIO 52909T and SCSIO 52915T were separately clustered together and formed a well-separated phylogenetic branch distinct from the other known species in the genus Rubrobacter. Based on the data presented here, these two strains should be recognized as two new species in the genus Rubrobacter, for which the names Rubrobacter tropicus sp. nov., with the type strain SCSIO 52909T (=KCTC 49412T=CGMCC 1.13853T), and Rubrobacter marinus sp. nov., with the type strain SCSIO 52915T (=KCTC 49411T=CGMCC 1.13852T), are proposed.

Autophagy Dually Induced by AMP Surplus and Oxidative Stress Enhances Hemocyte Survival and Bactericidal Capacity via AMPK Pathway in Crassostrea hongkongensis.

Crassostrea hongkongensis (Hong Kong oyster) is an ecologically and economically valuable shellfish endemic to South/Southeast Asia. Due to ocean acidification and warming waters, they have become increasingly vulnerable to invading microbes including Vibrio parahaemolyticus, a significant foodborne human pathogen. In recent years, outbreaks of V. parahaemolyticus have emerged as a perennial phenomenon in parts of the world, necessitating to better understand the biology of host-pathogen interactions in this under-examined marine invertebrate. Although an immunologically relevant autophagy apparatus has been identified in Crassostrea gigas, an evolutionarily close mollusk cousin, the precise mechanistic details of C. hongkongensis autophagy during V. parahaemolyticus infection are still wanting. Here, we compellingly demonstrated that in vivo V. parahaemolyticus challenge robustly triggered autophagic signaling in C. hongkongensis hemocytes peaking at 6 h post-infection, which subsequently promoted bacterial clearance and dampened premature apoptosis. Simultaneously, a large surplus of adenosine monophosphate (AMP) and elevations in reactive oxygen species (ROS, specifically mitochondrial O2 - and cellular H2O2) formation were observed post-infection. Extrinsically applied AMP and ROS could synergistically induce AMP-activated protein kinase (AMPK) phosphorylation to stimulate downstream autophagic events. V. parahaemolyticus infection-induced autophagy was pharmacologically shown to be AMPK-dependent in vivo. Overall, our results establish autophagy as a crucial arm of host defense against Vibrio infections in mollusks, and provide new insights into the underappreciated roles of ROS and AMP as co-regulators of autophagy.

Actinomarinicola tropica gen. nov. sp. nov., a new marine actinobacterium of the family Iamiaceae, isolated from South China Sea sediment environments.

A novel marine actinobacterium, strain SCSIO 58843T, was isolated from the sediment sample collected from the South China Sea. Strain SCSIO 58843T was Gram-stain-positive, aerobic and rod shaped. The whole-cell hydrolysis of amino acids contained dd-DAP, alanine, glutamic acid, glycine and aspartic acid. The main menaquinone was MK-9(H8). The major fatty acids were C17 : 1 ω8c and C17 : 0. The major phospholipids were diphosphatidylglycerol (DPG), phosphatidylinositol (PI), phospatidylcholine (PC) and phosphatidylinositolmannoside (PIM). The G+C content of the genomic DNA was 72.5 %. Phylogenetic analysis of the 16S rRNA gene sequences showed that strain SCSIO 58843T formed a new lineage in the family Iamiaceae and had the highest similarity of 93.8 % with Iamia majanohamensis DSM 19957T. Strain SCSIO 58843T can be distinguished from these known genera in the family Iamiaceae by polyphasic data analyses, and represents a novel genus and novel species, for which Actinomarinicola tropica gen. nov., sp. nov is proposed with the type strain SCSIO 58843T(=KCTC 49408T=CGMCC 1.17503T).

Longirhabdus pacifica gen. nov., sp. nov., isolated from a deep-sea hydrothermal sediment in the West Pacific Ocean.

A novel Gram-stain-negative bacterium, designated as SCSIO 06110T, was isolated from a deep-sea sediment of the West Pacific Ocean. Cells were 0.5-0.8 µm in width and 3.0-4.0 µm in length, spore-forming, rod-shaped with peritrichous flagella. Positive for catalase and urease, negative for oxidase and nitrate reduction. Growth occurred at 15-37 °C, pH 6-9 and 1-5 % (w/v) NaCl, with optimum growth at 28 °C, pH 7 and 3 % (w/v) NaCl. MK-7 was the only menaquinone. The strain possessed diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol and two unidentified phospholipids. Iso-C16 : 0, iso-C15 : 0 and iso-C14 : 0 were the major fatty acids. The novel isolate clustered with genera in the family Paenibacillaceae, but formed a separated branch with the closest relative Chengkuizengella sediminis J15A17T (91.1 % sequence similarity) when compared in a phylogenetic analysis of 16S rRNA gene sequences. The DNA G+C content of strain SCSIO 06110T was 38.5 mol%. Based on the polyphasic data presented, a new genus, Longirhabdus gen. nov., is proposed in the family Paenibacillaceae with the type species Longirhabdus pacifica sp. nov. and the type strain SCSIO 06110T (=DSM 105158T=CGMCC 1.16550T).

Staphylospora marina gen. nov., sp. nov., a novel member of the family Thermoactinomycetaceae, isolated from a deep-sea hydrothermal vent in the Pacific Ocean.

A novel bacterium, designated SCSIO 07575T, was isolated from a deep-sea hydrothermal sediment sample collected from the western Pacific Ocean. Growth at 65 °C was observed, but not at 70 °C or below 37 °C. The optimum conditions for growth were at 55-65 °C, pH 7.0 and in the presence of 2 % (w/v) NaCl. Strain SCSIO 07575T showed filamentous growth. Unstable formation of white aerial mycelia was observed, which disappeared after several times' subculture. Abundant substrate mycelia were observed with grape-like spores. No soluble pigment was observed. Phylogenetic analysis of 16S rRNA gene sequences showed that SCSIO 07575T belonged to the family Thermoactinomycetaceae and formed a distinct clade in the phylogenetic tree. The cell-wall peptidoglycan contained meso-diaminopimelic acid. Whole-cell hydrolysates contained ribose, xylose, glucose and galactose. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminophospholipid and two unidentified phospholipids. The predominant menaquinone was MK-7. Major fatty acids were iso-C15 : 0, iso-C17 : 0 and iso-C16 : 0. Based on the whole genome sequence analysis, the genome size was 2 751 094 bp with a DNA G+C value of 57.2 mol%, including one circular chromosome and one plasmid. On the basis of polyphasic data, strain SCSIO 07575T represented a novel species of a new genus within the family Thermoactinomycetaceae, for which the name Staphylospora gen. nov. is proposed with the type species Staphylospora marina sp. nov. and the type strain SCSIO 07575T (=DSM 106793T=CGMCC 1.15879T).

Rubrobacter indicoceani sp. nov., a new marine actinobacterium isolated from Indian Ocean sediment.

A novel mesophilic marine actinobacterial strain, designated as SCSIO 08198T, was isolated from a deep-sea sediment sample collected from the Indian Ocean. The strain was Gram-stain-positive, rod-shaped and salmon pink in colour. Good growth occurred on marine agar with 1-5 % (w/v) NaCl and incubation at 28 °C for more than a fortnight. Sensitive to short ultraviolet radiation. Analysis of 16S rRNA gene sequences revealed that strain SCSIO 08198T had the highest similarity of 97.2 % to Rubrobacter radiotolerans DSM 5868T, and loosely related (<94.2 %) to all other species in the genus Rubrobacter. Phylogenetic analysis based on nearly complete 16S rRNA gene sequences revealed that the novel isolate shared a lineage with members of the genus Rubrobacter. The total cellular fatty acid profile was dominated by C16 : 0 12-methyl. MK-8 was the main menaquinone. The peptidoglycan type was A3α (l-Lys-l-Ala). The major phospholipids were diphosphatidylglycerol, phosphatidylglycerol and unidentified phospholipids. Based on the whole genome sequence analysis, the genome size is 3 078 689 bp with DNA G+C value of 63.8 mol%, including one circular chromosome and two plasmids. Based on these polyphasic data, a new species, Rubrobacterindicoceani sp. nov., is proposed, with the type strain SCSIO 08198T (=DSM 105148T=CGMCC 1.16398T).

Selection of housekeeping genes as internal controls for quantitative RT-PCR analysis of the veined rapa whelk (Rapana venosa).

BACKGROUND: The veined rapa whelk Rapana venosa is an important commercial shellfish in China and quantitative real-time PCR (qRT-PCR) has become the standard method to study gene expression in R. venosa. For accurate and reliable gene expression results, qRT-PCR assays require housekeeping genes as internal controls, which display highly uniform expression in different tissues or stages of development. However, to date no studies have validated housekeeping genes in R. venosa for use as internal controls for qRT-PCR. METHODS: In this study, we selected the following 13 candidate genes for suitability as internal controls: elongation factor-1α (EF-1α), α-actin (ACT), cytochrome c oxidase subunit 1 (COX1), nicotinamide adenine dinucleotide dehydrogenase (ubiquinone) 1α subcomplex subunit 7 (NDUFA7), 60S ribosomal protein L5 (RL5), 60S ribosomal protein L28 (RL28), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), ß-tubulin (TUBB), 40S ribosomal protein S25 (RS25), 40S ribosomal protein S8 (RS8), ubiquitin-conjugating enzyme E2 (UBE2), histone H3 (HH3), and peptidyl-prolyl cis-trans isomerase A (PPIA). We measured the expression levels of these 13 candidate internal controls in eight different tissues and twelve larvae developmental stages by qRT-PCR. Further analysis of the expression stability of the tested genes was performed using GeNorm and RefFinder algorithms. RESULTS: Of the 13 candidate genes tested, we found that EF-1α was the most stable internal control gene in almost all adult tissue samples investigated with RL5 and RL28 as secondary choices. For the normalization of a single specific tissue, we suggested that EF-1α and NDUFA7 are the best combination in gonad, as well as COX1 and RL28 for intestine, EF-1α and RL5 for kidney, EF-1α and COX1 for gill, EF-1α and RL28 for Leiblein and mantle, EF-1α, RL5, and NDUFA7 for liver, GAPDH, PPIA, and RL28 for hemocyte. From a developmental perspective, we found that RL28 was the most stable gene in all developmental stages measured, and COX1 and RL5 were appropriate secondary choices. For the specific developmental stage, we recommended the following combination for normalization, PPIA, RS25, and RL28 for stage 1, RL5 and RL28 for stage 2 and 5, RL28 and NDUFA7 for stage 3, and PPIA and TUBB for stage 4. DISCUSSION: Our results are instrumental for the selection of appropriately validated housekeeping genes for use as internal controls for gene expression studies in adult tissues or larval development of R. venosa in the future.

[Responses of soil nematode communities to long-term application of inorganic fertilizers in upland red soil].

Soil biota plays a key role in ecosystem functioning of red soil. Based on the long-term inorganic fertilization field experiment (25-year) in an upland red soil, the impacts of different inorganic fertilization managements, including NPK (nitrogen, phosphorus and potassium fertilizers), NPKCaS (NPK plus gypsum fertilizers), NP (nitrogen and phosphorus fertilizers), NK (nitrogen and potassium fertilizers) and PK (phosphorus and potassium fertilizers), on the assemblage of soil nematodes during the growing period of peanut were investigated. Significant differences among the treatments were observed for total nematode abundance, trophic groups and ecological indices (P < 0.01). The total nematode abundance decreased in the order of PK > NPKCaS > NPK > NP > NK. The total number of nematodes was significantly higher in NPKCaS and PK than in NPK, NP and NK except in May. Plant parasitic nematodes were the dominant trophic group in all treatments excepted in NPKCaS, and their proportion ranged between 38% and 65%. The dominant trophic group in NPKCaS was bacterivores and represented 42.1%. Furthermore, the higher values of maturity index, Wasilewska index and structure index in NPKCaS indicated that the combined application of NPK and gypsum could remarkably relieve soil acidification, resulting in a more mature and stable soil food web structure. While, that of the NK had the opposite effect. In conclusion, our study suggested that the application of both gypsum and phosphate is an effective practice to improve soil quality. Moreover, the analysis of nematode assemblage is relevant to reflect the impact of different inorganic fertilizer on the red soil ecosystem.

Active ammonia oxidizers in an acidic soil are phylogenetically closely related to neutrophilic archaeon.

All cultivated ammonia-oxidizing archaea (AOA) within the Nitrososphaera cluster (former soil group 1.1b) are neutrophilic. Molecular surveys also indicate the existence of Nitrososphaera-like phylotypes in acidic soil, but their ecological roles are poorly understood. In this study, we present molecular evidence for the chemolithoautotrophic growth of Nitrososphaera-like AOA in an acidic soil with pH 4.92 using DNA-based stable isotope probing (SIP). Soil microcosm incubations demonstrated that nitrification was stimulated by urea fertilization and accompanied by a significant increase in the abundance of AOA rather than ammonia-oxidizing bacteria (AOB). Real-time PCR analysis of amoA genes as a function of the buoyant density of the DNA gradient following the ultracentrifugation of the total DNA extracted from SIP microcosms indicated a substantial growth of soil AOA during nitrification. Pyrosequencing of the total 16S rRNA genes in the "heavy" DNA fractions suggested that archaeal communities were labeled to a much greater extent than soil AOB. Acetylene inhibition further showed that (13)CO2 assimilation by nitrifying communities depended solely on ammonia oxidation activity, suggesting a chemolithoautotrophic lifestyle. Phylogenetic analysis of both (13)C-labeled amoA and 16S rRNA genes revealed that most of the active AOA were phylogenetically closely related to the neutrophilic strains Nitrososphaera viennensis EN76 and JG1 within the Nitrososphaera cluster. Our results provide strong evidence for the adaptive growth of Nitrososphaera-like AOA in acidic soil, suggesting a greater metabolic versatility of soil AOA than previously appreciated.

[Isolation, identification and characterization of a strain of phosphate-solubilizing bacteria from red soil].

OBJECTIVE: To improve use efficiency of phosphorus in latosolic red soil and to explore mechanism of phosphate solubilization. METHODS: Pikovskaya and National Botanical Research Institute' s Phosphate broth were used to isolate a phosphate-solubilizing bacterium coded as C5-A from the rhizosphere soil of peanut. According to its morphological, physiological, biochemical properties and its 16S rRNA sequence, its position in phylogenetic development tree was defined. By measuring changes in pH of the National Botanical Research Institute's Phosphate solution in which C5-A was incubated, phosphate solubilizing capacity was determined. Through fermentation, effects of carbon and nitrogen sources on the capacity of strain C5-A were investigated. Kinds and concentrations of organic acids in the cultures different in N sources were also determined by HPLC. RESULTS: The strain was identified as Burkholderia cepacia, which is stable in hereditary. In aluminum phosphate and ferric phosphate solutions, its P solubilizing capacity was negatively related to pH. It solubilized tricalium phosphate, aluminum phosphate, ferric phosphate and rock phosphates powder, and could dissolve as much as 125.79 mg/L, 227.34 mg/L, 60.02 mg/L and 321.15 mg/L P, respectively. For RPP, P solubilizing capacity of the strain was related to type and concentration of the powder. When using maltose and ammonium oxalate as C and N sources, the strain displayed its highest P solubilizing capacity. HPLC analysis detected 10 organic acids in the culture, namely: oxalic acid, acetic acid, malic acid, lactic acid, citric acid, cuccinc acid and 5 unknown organic acids. Interestingly, it is acetic acid rather than gluconic acid being the most important organic acid affecting P solubilization. CONCLUSION: The strain isolated from the rhizosphere soil of peanut plants growing in a red soil field can dissolve hard-to-solve inorganic salts, and is a promising microbial resource for development of high efficiency biological phosphorus fertilizer for latosolic red soil.

Atmospheric NO2 and NH3 deposition into a typical agro-ecosystem in Southeast China.

The dry deposition of atmospheric nitrogen (including NO(2) and NH(3)) into a typical agro-ecosystem in Southeast China during 2006-2007 was estimated. Results indicated that the dry deposition velocities of NO(2) and NH(3) ranged from 0.04-0.24 cm s(-1) and 0.09-0.47 cm s(-1), respectively. The higher values appeared in the non-crop growing period. Concentrations of atmospheric NO(2) and NH(3) ranged from 24.64-104.10 µgN m(-3) and 14.40-389.6 µgN m(-3), respectively. Variation of the NH(3) mixing ratio showed a clear double-peak. NO(2) and NH(3) deposition fluxes were 74.68-80.75 kgN ha(-1), which was equivalent to 162.4 and 175.5 kg ha(-1) of urea applied in 2006-2007. The N deposition fluxes were 13.91-40.38 and 5.33-22.73 kgN ha(-1) in peanut and rice growing periods, accounting for 8.18%-40.38% and 2.13%-23.06% of N fertilizer usages, respectively. NO(2) and NH(3) deposition were significant for the red soil farmland.

Effects of several amendments on rice growth and uptake of copper and cadmium from a contaminated soil.

Heavy metals in variable charge soil are highly bioavailable and easy to transfer into plants. Since it is impossible to completely eliminate rice planting on contaminated soils, some remediation and mitigation techniques are necessary to reduce metal bioavailability and uptake by rice. This pot experiment investigated the effects of seven amendments on the growth of rice and uptake of heavy metals from a paddy soil that was contaminated by copper and cadmium. The best results were from the application of limestone that increased grain yield by 12.5-16.5 fold, and decreased Cu and Cd concentrations in grain by 23.0%-50.4%. Application of calcium magnesium phosphate, calcium silicate, pig manure, and peat also increased the grain yield by 0.3-15.3 fold, and effectively decreased the Cu and Cd concentrations in grain. Cd concentration in grain was slightly reduced in the treatments of Chinese milk vetch and zinc sulfate. Concentrations of Cu and Cd in grain and straw were dependent on the available Cu and Cd in the soils, and soil available Cu and Cd were significantly affected by the soil pH.

[Effects of soil water status on gas exchange of peanut and early rice leaves].

The gas exchange characteristics of peanut and early rice leaves were investigated in experimental plots under different soil water conditions over a long growth period. The results showed that at the branching stage of peanut, the stomatal conductance (Gs) and transpiration rate (Tr) decreased slightly under mild and moderate soil water stress, while the net photosynthetic rate (Pn) and leaf water use efficiency (WUE) increased. The Gs/Tr ratio also increased under mild water stress, but decreased under moderate water stress. At podding stage, the Gs, Tr, Gs/Tr ratio and Pn decreased, while WUE increased significantly under mild and moderate water stress. The peanut was suffered from water stress at its pod setting stage. At the grain filling stage of early rice, the Gs, Tr and Gs/Tr ratio fluctuated insignificantly under mild and moderate water stress, while Pn and WUE increased significantly, with an increase in grain yield under mild water stress. It's suggested that the combination of Gs and Gs/Tr ratio could be a reference index for crop water stress, namely, crops could be hazarded by water stress when Gs and Gs/Tr decreased synchronously.

[Effect of long-term fertilization on crop yield and soil fertility of upland red soil].

The studies on the influence of long-term fertilization on crop yield and soil fertility of upland red soil showed that P was the most deficient in this soil, and hence, phosphorus fertilizer had the best effect on crop yield. Applying lime and microelements could not significantly increase the crop yield. The concentration of P and K in peanut could be increased if fertilizer was applied, indicating that the supply level of soil nutrients decided the nutrient concentration in plants. The reconstructive efficiency of soil available nutrient pool was dependent on the surplus or deficit of soil nutrients. When the surplus of nutrients was 1 kg x hm(-2), N was increased by 0.6-6.2 mg x kg(-1), P was increased by 0.20-0.28 mg x kg(-1), and K was increased by 1.1-8.5 mg x kg(-1). The changing in results was due to the loss of N and K from soil. The nutrient bupplying capability of soil was the quantity of the nutrients which soil could provide by weathering to satisfy the plant growth. The amount of P fixed by soil was 43.5 kg x hm(-2) x yr(-1), and that of N and K provided by soil was 40.5 and 55 x kg x hm(-2) x yr(-1), respectively.

[Effects of different vegetation restoration of degraded red soil on earthworm population dynamics].

This study was conducted at the long-term experimental plots in Ecological Experimental Station of Red Soil in Yujiang County (28 degrees 15'30''N, 116 degrees 55'30''E ), Jiangxi Province, subtropical China. Earthworm population was investigated seasonally from May 1999 to February 2000, under different vegetations including four artificial woodlands [deciduous broadleaf woodland (Quercus chenii, Qc), evergreen broadleaf woodland (Schima superba, Ss), coniferous woodland (Pinus massonina, Pm) and mixed woodland (Schima superba-Pinus massonina, Sm)], two grasslands [gently-disturbed grassland (G1), undisturbed grassland (G2)] and control wasteland (CK). The results indicated that the population structure was very simple. Only Drawinda gisti characterized by pioneer was found. The seasonal averages of density and biomass were in the order of G2 > G1 > Qc > Ss > Pm > Sm > CK, and those of G2, G1 and Qc were significantly higher than those of the latters (P < 0.05). Seasonal fluctuations were obvious with dry-hot summer depressing the earthworm population sharply, leading to the aestivation of earthworm. Based on the variation coefficients of density and biomass, Qc had the highest ecosystem stability, followed by Sm and Ss, and G1, G2, and Pm had the lowest stability. The overall differentiation of earthworm population could be drawn through canonical discriminant analysis. There were significant correlations between earthworms and some soil properties (P < 0.01). Overall, the differentiation of earthworm population was driven by the quantity and quality of soil organic matter returned by the vegetations. Additionally, based on earthworm population, the importance of selecting appropriate vegetation types during the restoration of degraded red soil was emphasized.

[Nutrient and water cycling in red soils with different planting system and their management].

Based on the data of long term located experiment, this paper studied the characteristics of nutrient and water cycling and balance and of energy flow in upland red soils with different planting system. The results showed that in red soil areas, the rainfall from March to June accounted for 60% of the whole year, which induced frequent seasonal drought and severe water and soil loss. The application of N, P and K on upland red soil was overabundant and unbalanced, which induced a reduced ratio of input and output. Optimized planting mode could increase the water and light utilization efficiency, decrease the frequency and degree of occurred drought, and increase the nutrient recycling rate. The main measures for rationally developing and utilizing red soil should be establishing compound agro-ecosystem model of planting and feeding, saving irrigation water, increasing mulch, cover-cultivating crops and forests, increasing the proportion of organic fertilizer, realizing rational and balanced fertilization, further optimizing planting structure, regulating energy input structure, and adopting multilevel-technologies of food chain utilization.