Abstract:The responses of soil enzyme activity of freshwater marsh, microbial biomass carbon (MBC), dissolved organic carbon (DOC) and aboveground biomass to water gradients were studied with Carex lasiocarpa pot culture experiment. The relationships between soil enzyme activity and MBC, DOC and aboveground biomass were discussed. The water gradients were W1, 15 cm; W2, -5 cm; W3, -5–5 cm; W4, submerged. The results indicated that acid phosphatase, invertase and urease activities were decreased with the increase of water level, while catalase activity was increased with moisture content increasing. Drying-wetting alternation (W3) increased soil enzyme activities if compared with W1. MBC content followed the order of W3 > W1 > W2 > W4, and the activities of invertase, urease and catalase were significantly positively correlated with MBC (p < 0.05). DOC content presented the order of W4 > W1 > W3 > W2, and the activities of urease and acid phosphatase were most significantly negatively correlated with DOC (p < 0.01). In addition, drying-wetting alternation promoted the growth of Carex lasiocarpa. When water submerged plants, the growth of Carex lasiocarpa was significantly inhibited. The aboveground biomass was positively related to soil enzyme activities. There were close relationships between the activities of invertase, urease and catalase and the growth situation of Carex lasiocarpa.

Abstract:The water-retaining capacity, percolation and evaporation of stony soil in Liupan Mountains, China, were measured in order to understand the effect of rock fragments on soil hydrological processes. The results indicated that the effective water-retaining capacity of soil is positively related with the volumetric content of rock fragments, but there is no relation between saturated water-retaining capacity and rock fragment content. For the soil layers within 0–40 cm, the steady infiltration rate increases with increasing volumetric content of rock fragments until it reaches the range of 15%–20%, and then it decreases when the rock fragment content further increases. For the soil layers below 40 cm, the steady infiltration rate always increases with increasing rock fragment content. The soil evaporation rate decreases with increasing volumetric content of rock fragments when it varies in the range of 0–20%, while the soil evaporation rate keeps basically stable when the rock fragment content is higher than 20%. The soil evaporation rate shows a rising tendency with increasing size of rock fragments.

Abstract:Several nitrogen (N) field experiments were carried out in Nanjing and Anyang, China, to study the dynamic characteristics of biomass accumulation and N uptake, and to define the dilution curve for critical N concentration in cotton reproductive organ over the growth period. The results show that the total biomass and N accumulation were affected significantly by the rate of N application, exhibiting a sigmoid curve over time. The beginning time of fast N accumulation was 1–5 d earlier than that of biomass accumulation. The cotton lint yield was correlated with N concentration in the reproductive organ and fluctuated with varying N concentration, indicating the existence of luxurious N consumption in the cotton reproductive organ. The N concentration increased with increasing N application rates, and decreased gradually during the growth period. The relationship between biomass and N concentration can be described with a power equation. The patterns of the N concentration dilution model were consistent at both experimental sites, but the model parameter values of a differed. The results presented in this paper indicate that a critical N concentration dilution curve for cotton reproductive organ is independent of ecological region and can be described with a power equation.

Abstract:Hirudinea in China were reviewed. The ecological distribution of Hirudinea, the population dynamics of H. hainana, the adaptation of H. hainana to temperature, soil humidity and pH, the response of H. hainana to temperature, relative humidity and light, and the effects of human activities on H. hainana populations were discussed. The land-leeches' behavior ecology, including (1) the locomotion of H. hainana such as shortening, oscillating, rotating, sucking cleaning, rubbing and foraging behaviors; (2) the factors influencing these behaviors; (3) the ecological significance, was also discussed. The ecology of freshwater leeches including (1) behavior in paddy fields of Ninghsien, Zhejiang Province, China; (2) relationship between population dynamics of Whitmania laevis and chemical factors in paddy fields of Guangzhou, China; (3) chemical environment of blood-sucking Hirudinaria manillensis in paddy fields of Guangzhou was described. The study also discussed the foraging, growth dynamics, life recycle and biology of reproduction of blood-sucking land-leech H. hainana and freshwater leech Hirudinaria manillensis, the taxonomy and the zoogeography. In addition, the morphology including histology and anatomy of the organic system of H. hainana was described. The Hirudinea can be classified into 2 subclasses (Branchiobdellidea and Euhirudinea), 3 orders (Branchiobdellida, Rhynchobdellida and Arhynchobdellida), 9 families, 33 genera and 111 species. The response of leeches to pesticides, including toxicity (LD50, LD95) of different pesticides to H. hainana, was presented. Medical usage of the leech Hirudin from salivary glands as anticoagulant material was discussed. Hirudin (from Hirudo medicinalis), Haemadin (from land-leech), and hementi (from Hementeria ghilianii) were identified and isolated.

Abstract:Isolation, molecular identification and phylogenetic analysis were carried out to investigate the biodiversity of manganese bacteria in sediments which were collected from the Arctic Ocean during the 2^nd Chinese Arctic Scientific Expedition. 21 and 19 species of cultivable strains were isolated from sediments at Stations P11 and S11, respectively, according to their distinct morphological character on the screening plate of manganese medium. Molecular identification and phylogenetic analysis showed that the cultivable manganese bacteria from Station P11 were basically composed of γ-Proteobacteria (γ subgroup of the Proteobacteria branch of the domain Bacteria) and Actinobacteria, which accounted for 86% and 14%, respectively. The isolates of γ-Proteobacteria mainly included Psychrobacter, Shewanella, Acinetobacter and Marinobacter, of which Psychrobacter was the major genus, which accounted for 67% of the γ-Proteobacteria. The cultivable manganese bacteria from Station S11 included α-Proteobacteria, γ-Proteobacteria and Flavobacteria of Bacteroides. The γ-Proteobacteria mainly included Shewanella, Marinomonas and Alteromonas. The majority of α-Proteobacteria was Sphingomonas. The phylogenetic analysis indicated that bacteria from sediments at Stations P11 and S11 had different cultivable manganese microbial communities. All tested strains had higher resistance to Mn²⁺, of which Marinomonas sp. S11-S-4 had the highest resistant ability.