Biomedical subjects

Zucong Cai

Publications and source records attributed to Zucong Cai.

11 recordsLinked to original sources

PubMed2007

Nitrous oxide emissions from an intensively cultivated maize-wheat rotation soil in the North China Plain.

N2O emissions from a maize-wheat rotation field were monitored in the Fengqiu State Key Agro-Ecological Experimental Station (Fengqiu County, Henan Province, China) from June 2004 to June 2005. The experiment included four treatments: a bare (crop-absent) soil treated with 150 kg N ha-1 (WN150) and soils fertilized with 0 (N0), 150 (N150), and 250 (N250) kg N ha-1 and cropped with maize or wheat. The bulk of the N2O emissions occurred in pulses following the application of fertilizer N at soil temperatures of 15 degrees C or more. The application of fertilizer N significantly increased the N2O emission, from 636 g N2O-N ha-1 year-1 in the N0 treatment to 4480 g N2O-N ha-1 year-1 in the N250 treatment. However, this increase primarily occurred during the maize growing season. The emission factor of applied fertilizer N as N2O was 1.05-1.34% and 0.24-0.26% during the 105-day maize and 241-day wheat growing seasons, respectively, and was on average 0.61-0.77%. Increasing the rate of fertilizer application increased the emission factor during the maize growing season. The presence of maize appears to increase N2O emission by 45% versus bare soil during the maize growing season. And, N2O emission during the maize season were significantly related to CO2 production (R=0.43-0.81, n=30, P<0.05). N2O emission was greatly affected by soil moisture during the maize growing season and by soil temperature during the wheat growing season. The maximum rates of nitrification occurred when soil moisture was in the range of 45-60% WFPS, with the optimum value being approximately 50%. However, soil moisture influenced N2O emission only when the soil temperature was at the optimum level. It is suggested that reducing the application rate of basal fertilizer N during the maize growing season could decrease N2O emission.

Agriculture↗

PubMed2005

[Effects of N application and maize growth on N2O emission from soil].

With pot experiment and using static chamber-GC technique, this paper studied the effects of N application (150 and 300 mg x kg(-1) soil) and maize growth on N2O emission from soil. In maize-planted soil, the N2O emission rate increased with increasing N application rate, its peak appeared at seedling stage, and there was no significant correlation between N2O emission and air temperature. Contrarily, in bare soil, the peak of N2O emission rate occurred at the anaphase of the experiment, and there was a significant exponential correlation between N2O emission and air temperature. The total amount of N2O emission increased remarkably with increasing N application rate in both planted and bare soils. In comparing with bare soil, maize-planting reduced N2O emission by 92% and 87%, respectively at high and low N application rates, which suggested that maize-planting not only affected the seasonal variation and magnitude of N2O emission from soil, but also altered the relationship between air temperature and soil N2O emission.

Fertilizers↗

PubMed2005

[Dynamics of fluvo-aquic soil organic matter fractions under long-term fertilization].

By the method of relative density fractionation, this paper studied the dynamics of organic matter and its light and heavy fractions in a fluvo-aquic soil under long-term fertilization. The results indicated under current fertilization system, the contents of soil organic matter and its light and heavy fractions were basically unchanged within 13 successive years of no fertilization, but had an increasing trend with the duration of chemical fertilizer NPK and organic manure applications, with a larger fluctuation among years and a less increment in treatment NPK. Regression analysis showed that soil organic matter and its light and heavy fractions had a linear correlation with the duration of fertilization in treatment NPK, and had a logarithm correlation in treatment organic manure.

Crops, Agricultural↗

PubMed2004

[Methods for studying soil microbial diversity].

This paper gave a review on the main methods for studying soil microbial diversity. Traditionally, the analysis of soil microbial communities relied on culturing techniques, using a variety of culture media. However, only a small fraction of the soil microbial community has been cultured and isolated with this approach. Other methods such as Biolog GN analysis, phospholipids fatty acids analysis and nucleic acid-based analysis can be used to study and characterize soil microbes which currently cannot be cultured, and to get more and complete information about soil microbial community.

Biodiversity↗

PubMed2003

Key factors affecting spatial variation of methane emissions from freshwater marshes.

To understand the mechanism for spatial variation of CH(4) emissions from marshes grown with different type of plants in a region and plots within a certain marsh grown with one type of plants, we measured CH(4) emissions from a region in which eutrophic freshwater marshes were divided into three types: Carex lasiocarpa, Carex meyeruana and Deyeuxia angustifolia according to plant type as well as CH(4) concentration in porewater, aboveground plant biomass and stem density in situ in Sanjiang Plain of Northeast China in August 2001. Spatial variation of CH(4) emissions from both different marshes in a region and different plots within a certain marsh was high. The flux rates of CH(4) emissions from three marshes ranged from 17.2 to 66.5 mg CH(4) m(-2)h(-1) with 34.76% of variation coefficient, whereas the values in Carex lasiocarpa, Carex meyeriana and Deyeuxia angustifolia marshes varied from 21.6 to 66.5 (39.61%), from 17.2 to 45.0 (29.26%) and from 19.1 to 33.0 mg CH(4) m(-2)h(-1) (17.51%), respectively. Both the flux rates and spatial variation of CH(4) emissions strongly increased as standing water depth increased significantly. Standing water depth greatly governed the spatial variation of CH(4) emissions from different marshes in a region by changing the amount of plant litters inundated in standing water, which provided labile organic C for methanogens and controlled CH(4) concentrations in porewater. Moreover, the aboveground plant biomass determined spatial variation of CH(4) emissions from plots within a certain marsh by controlling the pathways (stem density) of CH(4) emissions from the marsh into the atmosphere.

Biomass↗

PubMed2003

[Effect of temperature on methane production and oxidation in soils].

The influence of temperature and its mechanism on methane production and oxidation in soils were reviewed in this paper. Temperature can alter the soil ability to produce methane through changing types of dominant methanogens in archaeal community. Dominant methanogen is Methanosarcinaceae at higher temperature which can utilize both H2/CO2 and acetate as the precursor to produce methane, while Methanosaetaceae at lower temperature which only use acetate as the precursor and produce far less methane than do Methanosarcinaceae. Increasing soil temperature apparently raises soil ability to produce methane, which is called temperature effectiveness and expressed as Q10 with a range from 1.5 to 28 and an average of 4.1. There is an obviously positive correlation between temperature effectiveness (Q10) on methane production and substrate content. As compared to methane production, effect of temperature on methane oxidation is lower, which may be related to the strong affinity of methanotrophs for methane.

Methane↗

PubMed2003

[Factors influencing CH4 emissions from a permanently flooded rice field during rice growing period].

Permanently flooded rice fields are the rice fields which emit the largest amount of CH4 in China. A 6-years (1995-2000) measurement carried out in a permanently flooded rice field in Chongqing, China showed that draining floodwater in winter and planting upland crops, either winter wheat or rape, instead of fallow under flooded conditions not only stopped CH4 emission during the winter season, but also mitigated CH4 emission during following rice growing period. CH4 emission could also be mitigated by ridge-cultivation. By using the results obtained from 1998-2000, statistical analysis indicated a significant relationship between the mean CH4 emission over the rice growing period and averaged soil moisture in winter season, which explained 56% of the variation of the CH4 emissions among the years and treatments. The averaged soil moisture (0-20 cm) in winter season and soil temperature (5 cm) over the rice growing period explained 78% of the variation. The significance of soil moisture in winter season in CH4 emission during the following rice growing period was further demonstrated by a lysimeter experiment. The relationships implied that the precipitation during non-rice growing period, which dominates soil moisture at a large spatial scale, and the soil temperature during the rice growing period would be the main factors controlling the annual variation of CH4 emissions from rice fields.

Methane↗

PubMed2003

[Effect of plants on methane production, oxidation and emission].

The paper reviewed the role of plants in the processes of methane production, oxidation and emission in soils. It was the abilities of different plants to excrete the quantity and quality of root exudates that resulted in discrepancies of methane production among plants and in plant growing seasons. The oxygen magnitude of the downward transport through the plant aerenechyma, which, in turn, also acted as a conduit for methane from the soil to the atmosphere, affected endogenous methane oxidation capacity with plants and with plant growing seasons. Plant through changing amount and density of plant aerenchyma altered its ability to transport methane from soil to atmosphere. In addition to soil properties, flux and pattern of methane emission from soils largely depended on plant abilities to excrete exudates and oxygen, and transport methane in different plant growing seasons.

Methane↗

PubMed2003

[Effects of rice plants on methane emission from paddy fields].

Methane emission from rice paddy fields is the net result of the combination of many processes, i.e., CH4 production, CH4 oxidation and CH4 transportation in paddy soil. Rice plants play a key role in the CH4 emission from paddy fields, particularly in all the processes involved. The positive and negative effects of rice plants on CH4 emission from paddy fields are well recognized as the main factors influencing the temporal variation of CH4 emission flux in paddy field. Process-based studies about the effects of rice plants on methane emission from paddy fields were summarized, and different roles of rice plants on this emission were discussed. Root exudates and litters of rice plants could serve as the substrate for methanogenesis and enhance the CH4 production of paddy soils, resulting in a high CH4 emission peak, particularly in rice late growing season. Rhizospheric CH4 oxidation induced by rice root-excreted oxygen constitutes a main biogenic sink of CH4, which could account for 36-90% of CH4 produced in paddy soil over the entire growing season of rice. Up to 80% and more of CH4 released from rice field during a growing season could be emitted by rice plant-mediated transport. The fully developed aerenchyma of rice plants could be of importance in CH4 emission during rice growing seasons, and responsible for the CH4 emission peak observed at rice early growing season.

Methane↗

PubMed2002

[Responses of rice (Oryza sativa) growth and its C, N and P composition to FACE (free-air carbon dioxide enrichment) and N, P fertilization].

FACE (Free-air Carbon Dioxide Enrichment) was used to study the effects of elevated CO2 on rice (Oryza sativa) growth, tissue C/N, N and P concentration and uptake at different development stages under two N and two P levels. Results showed that elevated CO2 increased dry matter accumulation in rice stem, ear and root. Leaf dry matter was increased at tillering stage and no significant effect was found at jointing, heading and ripening stages. N concentration of stem and leaf was decreased. Ear N concentration at heading stage was increased but was decreased at ripening stage. No significant effect was found on root N concentration at tillering stage but root N concentration at jointing, heading and ripening was decreased. Leaf P concentration at jointing, heading and ripening was increased but no significant effect was found on P concentration in stem, ear and root. C content in various tissues changed unremarkably and the ratio of C over N (C/N) was increased. Elevated CO2 significantly increased P uptake in aboveground tissues; and increased N uptake, but the difference was not statistically significant. N and P fertilization had no significant effect on various tissue dry biomass. Tissue N content at higher N fertilization was higher than at lower N fertilization but no such effect of P fertilization on tissue P content was found. At higher N fertilization, elevated CO2 increased the ratio of below-ground biomass over above-ground biomass at ripening stage. Possible reasons are discussed for the differences of tissue N and P content and the ratio of below-ground biomass over above-ground biomass between elevated and ambient atmospheric CO2 concentrations.

Air↗

PubMed2002

[Determination of net exchange of CO2 between paddy fields and atmosphere with static poaque-chamber-based measurements].

We firstly introduced the method for determining the net ecosystem exchange fluxes of CO2 (NEE) between croplands and atmosphere, based on field measurements using static opaquechamber/gas chromatography methods was introduced, and the application of this method in the FACE (free-air CO2 enrichment) study to examine the effects of elevated CO2 on the NEE over a typical paddy ecosystem was carried out, because of lacking in observation data for some necessary parameters, e.g., dark maintenance respiration coefficient, only the minimum value of NEE (NEEmin) was calculated based on opaque-chamber measurements. The NEEmin data indicate that CO2 elevated by 200 +/- 40 mumol.mol-1 significantly increased the ecosystem uptake of atmospheric CO2 by a factor ca. 3. To accurately determine the NEE based on opaquechamber measurements, dark maintenance respiration coefficient, above-ground biomass and root: shoot, i.e. R:S, ratio of root to shoot should be observed over the whole growing season.

Air↗