[Response of Soil Nitrifier and Denitrifier Community and Activity to Elevated Atmospheric CO Concentration and Temperature].

Elevated atmospheric CO concentration and temperature may affect nitrifiers and denitrifiers which are related to soil N turnover. A climate change experiment was conducted in the rice-wheat rotation ecosystem. This study was used to investigate effects of elevated CO and temperature on soil microbial community structure, as well as abundance and activity of nitrifiers and denitrifiers.

[Fine root biomass and its nutrient storage in karst ecosystems under different vegetations in Central Guizhou, China].

The degeneration of karst ecosystem is closely associated with the reduction of soil nutrients and fine root biomass, and the retention of soil nutrients is of significance in sustaining ecosystem functioning. To understand the changes in the fine root biomass and soil nutrient retention in degenerated karst ecosystems, a comparative study was conducted with three typical vegetation stands (forest, shrub, and shrub-grass) in Central Guizhou of Southwest China. Soil samples with fine roots were collected from the depths 0-5 cm, 5-10 cm, and 10-15 cm, with the related indices of fine roots and nutrients measured.

Changes in cropland topsoil organic carbon with different fertilizations under long-term agro-ecosystem experiments across mainland China.

Topsoil soil organic carbon (SOC) data were collected from long-term Chinese agro-ecosystem experiments presented in 76 reports with measurements over 1977 and 2006. The data set comprised 481 observations (135 rice paddies and 346 dry croplands) of SOC under different fertilization schemes at 70 experimental sites (28 rice paddies and 42 dry croplands). The data set covered 16 dominant soil types found in croplands across 23 provinces of mainland China.

[Effects of heavy metals pollution on paddy soil aggregates composition and heavy metals distribution].

Topsoil samples were collected from a polluted and an adjacent non-polluted paddy field in the Taihu Lake region of China. Different particle size fractions of soil aggregates were separated by low-energy dispersion procedure, and their mass composition and Pb, Cd, Hg, and As concentrations were determined. Under heavy metals pollution, the mass composition of sand-sized fractions reduced, while that of clay-sized fractions increased.

[Responses of enzyme activities in different particle-size aggregates of paddy soil in Taihu Lake region of China to long-term fertilization].

Taking a long-term fertilized paddy soil in Taihu Lake region as research object, the enzyme activities in <2, 2-20, 20-200, and 200-2000 microm aggregates under no fertilization (NF), chemical fertilization (CF), chemical fertilization plus straw return (CFS), and chemical fertilization plus pig manure (CFM) were investigated. Fertilization promoted the formation of 200-2000 microm aggregates significantly. The enzyme activities differed with aggregates' particle-size.

[Variation of Cd, Zn and Se contents of polished rice and the potential health risk for subsistence-diet farmers from typical areas of South China].

In this study, a total of 70 polished rice samples were randomly collected at agro-product markets from some typical regions of South China. Their contents of Cd, Zn and Se were determined by atomic adsorption spectrophotometers (AAS) and atomic fluorescence spectrometry (AES) respectively. The variation of the contents with rice areas was described in terms of soil conditions and the potential health risk by food exposure to these rice rains for subsistence-diet fanners is discussed.

[An evaluation of net carbon sink effect and cost/benefits of a rice-rape rotation ecosystem under long-term fertilization from Tai Lake region of China].

Taking a long-term fertilized rice-rape rotation system in Taihu Lake as test objective, its annual C balance and economic benefit were estimated, based on the measurement of past years grain yield, litter C content, and field CO2 emission as well as the investigation of material and management inputs. The calculated annual C sink under different fertilizations ranged from 0.9 t C x hm(-2) x a(-1) to 7.

Topsoil organic carbon mineralization and CO2 evolution of three paddy soils from South China and the temperature dependence.

Carbon mineralization and its response to climatic warming have been receiving global attention for the last decade. Although the virtual influence of temperature effect is still in great debate, little is known on the mineralization of organic carbon (SOC) of paddy soils of China under warming. SOC mineralization of three major types of China's paddy soils is studied through laboratory incubation for 114 d under soil moisture regime of 70% water holding capacity at 20 degrees C and 25 degrees C respectively.

[Effects of conservational tillage on aggregate composition and organic carbon storage in purple paddy soil].

A 13 year experiment was conducted to study the effects of conservational tillage on the aggregate composition and organic carbon storage in purple paddy soil of Sichuan Basin. The results showed that under no-tillage and ridge culture (rice-rape) (NR-RR), no-tillage and plain culture (rice-rape) (NP-RR), no-tillage and ridge culture (rice-green manure) (NR-RGM), tillage and ridge culture (rice-rape) (TR-RR), and tillage and plain culture (rice-rape) (TP-RR), the proportion of macroaggregates in 0-10 cm soil layer was 23%, 69%, 9%, 36%, and 28% higher than that under conventional tillage (CT) (12%), respectively, while in 10-20 cm soil layer, this proportion under conservational tillage was 9%-38% lower than that under CT. The organic carbon storages in the macroaggregates at the depth of 0-10 cm were 13%, 31% and 32% higher under no-tillage and ridge culture (rice-fallow) (NR-RF), NR-RR and NR-RGM than under CT, respectively, while that at the depth of 10-20 cm was 28%-54% lower.

Distribution of Cu and Pb in particle size fractions of urban soils from different city zones of Nanjing, China.

Soil samples from 4 defined city zones of Nanjing were randomly collected at 0-5 cm and 5-20 cm intervals and size fractions of soil particles were separated from undisturbed bulk soils by low energy dispersion procedure. The total contents of Cu and Pb in the different particle size fractions of the urban soils were analyzed by HNO3-HF-HClO4 digestion and flame atomic absorption spectrophotometer determination. The total content of Cu and Pb in soil particle size fractions varied with their size and with city zones as well.

[Cd uptake and accumulation in grains by hybrid rice in two paddy soils: interactive effect of soil type and cultivars].

Cd translocation through soil-food crop-diet is considered as one of most important pathway for human Cd exposure. Rice is considered as a particular crop with high Cd uptake and accumulation in grains among the main food crops. In this study, a pot experiment was conducted to elucidate mutual interaction of soil and cultivars on uptake and grain accumulation of Cd by hybrid rice with or without Cd spiking at 2.

[Effect of submerging and wetting-redrying on Cd speciation and uptake by Sorghum hybrid Sudangrass in two paddy soils under spiked Cd].

Effect of continuous submerging and wetting-redrying on cadmium speciation and uptake by Sorghum hybrid Sudangrass in a Ferric-accumulic Stagnic Anthrosol and a Tipical Hapludult collected from the Taihu Lake region and the rolling downs of Yingtan, Jiangxi, China respectively, was studied by pot experiment with Cd spike in 2003. Compared to that under wetting-redrying treatment, the MgCl2-extracted pool of Cd in Huangnitu with spiked Cd of 5mg x kg(-1) and 10mg x kg(-1) was decreased from 21.8% and 28.

Sorption of pyrene on two paddy soils and their particle-size fractions.

In the present study, the sorption of pyrene on two kinds of bulk paddy soils, Gleyic Stagnic Anthrosols, and Ferric accumulic Stagnic Anthrosols as well as their particle-size fractions was investigated. The sorption isotherms fitted well with Freundlich equation. For both soils, the clay fraction( < 2 microm) and coarse sand fraction(2000-250 microm) had higher sorption capacity than fine sand fraction(250-20 microm) and silt fraction(20-2 microm).

[Aging of spiked pyrene in two paddy soils and their particle-size fractions after soil incubation and changes in extractability and bio-availability to earthworm].

Effect of aging on bioavailability and extractability of persistent organic pollutants has recently been paid much attention in environmental studies. This study deals with aging of spiked pyrene, a four-ring polycyclic hydrocarbon, in two paddy soils and their particle-size fractions under laboratory incubation and change in its extractability and bioavailability. The bioavailability of aged pyrene was tested by an assay of exposure to earthworms (Eisenia foetida).

Organic carbon stock in topsoil of Jiangsu Province, China, and the recent trend of carbon sequestration.

Data collection of soil organic carbon(SOC) of 154 soil series of Jiangsu, China from the second provincial soil survey and of recent changes in SOC from a number of field pilot experiments across the province were collected. Statistical analysis of SOC contents and soil properties related to organic carbon storage were performed. The provincial total topsoil SOC stock was estimated to be 0.

[Fractionation and spectroscopic property of dissolved organic matters in soils].

Based on a modified Leenheer DOM fractionation sche me, fractionation of DOM from paddy soils was conducted byusing XAD-8 resin into hydrophobic bases (HOB), hydrophobic acids (HOA), acid-insoluble matter (AIM), hydrophobic neutrals (HON) and hydrophillic matter (HIM), and their structural characteristics were studied by means of elemental composition, FTIR and 1H-NMR spectroscopy. The fractionation scheme used here provided a preferable separation of the fractions in terms of hydrophobicity and a high recovery. Of the DOC extracted from the soils, the HOB was the least fraction, accounting for 0.