The effects of nitrogen fertilization on N2O emissions from a rubber plantation.

To gain the effects of N fertilizer applications on N2O emissions and local climate change in fertilized rubber (Hevea brasiliensis) plantations in the tropics, we measured N2O fluxes from fertilized (75 kg N ha(-1) yr(-1)) and unfertilized rubber plantations at Xishuangbanna in southwest China over a 2-year period. The N2O emissions from the fertilized and unfertilized plots were 4.0 and 2.5 kg N ha(-1) yr(-1), respectively, and the N2O emission factor was 1.96%. Soil moisture, soil temperature, and the area weighted mean ammoniacal nitrogen (NH4(+)-N) content controlled the variations in N2O flux from the fertilized and unfertilized rubber plantations. NH4(+)-N did not influence temporal changes in N2O emissions from the trench, slope, or terrace plots, but controlled spatial variations in N2O emissions among the treatments. On a unit area basis, the 100-year carbon dioxide equivalence of the fertilized rubber plantation N2O offsets 5.8% and 31.5% of carbon sink of the rubber plantation and local tropical rainforest, respectively. When entire land area in Xishuangbanna is considered, N2O emissions from fertilized rubber plantations offset 17.1% of the tropical rainforest's carbon sink. The results show that if tropical rainforests are converted to fertilized rubber plantations, regional N2O emissions may enhance local climate warming.

[Characteristics of N2, N2O, NO, CO2 and CH4 Emissions in Anaerobic Condition from Sandy Loam Paddy Soil].

Understanding the characteristics of the production of nitrogen gases (N2, N2O and NO), CO2 and CH4 in anaerobic paddy soils is not only a prerequisite for an improved mechanistic understanding of key microbial processes involved in the production of atmospheric greenhouse gases (GHG), but might also provide the basis for designing greenhouse gas mitigation strategies. Moreover, quantifying the composition fractions of denitrification gaseous products is of key importance for improving parameterization schemes of microbial processes in process-oriented models which are increasingly used for assessing soil GHG emissions at site and national scales. In our experiments we investigated two sandy loam soils from two paddy fields. The initial concentrations of soil nitrate and dissolved organic carbon (DOC) were set at approximately 50 mg.kg-1 and mg.kg-1, respectively, by adding a mixture solution of KNO3 and glucose. The emissions of N2, N2O NO, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each soil sample were measured simultaneously, using a gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that the accumulative emissions of N2, N2O and NO of the two soil samples for the entire incubation period were 6 - 8, 20, and 15 - 18 mg.kg-1, respectively. By measuring the cumulative emissions of denitrification gases (N, = N2 + N2O + NO) we were able to explain 95% to 98% of observed changes in s1ifr nilrate concentrations. The mass fractions of N2, N2O and NO emissions to Nt were approximately 15% -19%, 47% -49%, and 34% -36%, respectively. Thus, in our experiments N2O and NO were the main products of denitrification for the entire incubation period. However, as the temporal courses of hourly or daily production of the denitrification gases showed, NO production dominated and peaked firstly, and then N2O, before finally N2 became the dominant product. Our results show the high temporal dynamic of denitrification end products and this knowledge is of crucial importance for model development, since so far existing models assume a fixed fraction of denitrification end products.

[Angiotensin II up-regulates osteopontin mRNA expression of RAW264.7 macrophages via p38MAPK signaling].

OBJECTIVE: To investigate the changes of osteopontin (OPN) mRNA expression induced by angiotensin II (AngII) in RAW264.7 macrophages, and to determine the role of p38 mitogen-activated protein kinase (p38MAPK) signaling in up-regulation of OPN mRNA expression. METHODS: RT-PCR was used for examining the OPN mRNA expression, and the phosphorylation of p38MAPK and activating transcription factor2 (ATF2) was detected by Western blot. RESULTS: (1) AngII (1 micromol/L) enhanced the expression of OPN mRNA in RAW264.7 macrophages with time-dependent, including 0.9 fold, 2.3 folds and 2.4 folds up-regulation at 6, 12, 24 h, respectively (all P < 0.01), whereas there was no significant change in negative control at 0 h and 24 h, suggesting that the mRNA expression of OPN is inducible. (2) Following excitation by Ang II in vitro, there was substantial up-regulation of OPN mRNA expression in RAW264.7 macrophages with dose-dependent; with a dose of 1 micromol/L incubated for 12 h, Ang II increased the OPN mRNA expression by 2.6 folds (P < 0.01). (3) Pre-treatment with SB202190 (5 micromol/L) for 30 min in RAW264.7 macrophages before AngII (1 micromol/L) used, the expression of OPN mRNA was inhibited by 61.7% (P < 0.01); but no marked inhibition had happened at the time of treatment with both SB202190 (5 micromol/L) and Ang II (1 micromol/L) added at the same time and with SB202190 (5 micromol/L) for 120 min after Ang II (1 micromol/L) used. (4) Pre-treatment with SB202190 (1, 5, 10 micromol/L) for 30 min in RAW264.7 macrophages before Ang II (1 micromol/L) used, the expression of OPN mRNA was decreased by 43.4%, 63.0% and 65.5%, respectively (all P < 0.01). (5) There was a maximal expression of p38MAPK phosphorylation at 15 approximately 30 min induced by Ang II (1 micromol/L) in RAW264.7 macrophages, and the maximal expression of phosphorylated ATF2 was at 30 approximately 45 min. (6) Pre-treatment with SB202190 (1, 5 micromol/L) for 30 min in RAW264.7 macrophages before Ang II (1 micromol/L) used, the expression of p38MAPK phosphorylation was inhibited markedly with dose-dependent, and the phosphorylation of p38MAPK was decreased by 61.7% (P < 0.01) after the SB202190 (5 micromol/L) was used. CONCLUSION: Angiotensin II may up-regulate osteopontin mRNA expression of RAW264.7 macrophages via p38MAPK signaling.

[Effect of carbon substrate concentration on N2, N2O, NO, CO2, and CH4 emissions from a paddy soil in anaerobic condition].

Understanding the effects of carbon and nitrogen substrates concentrations on the emissions of denitrification gases including nitrogen (N2) , nitrous oxide (N2O) and nitric oxide (NO), carbon dioxide (CO2) and methane (CH4) from anaerobic paddy soils is believed to be helpful for development of greenhouse gas mitigation strategies. Moreover, understanding the quantitative dependence of denitrification products compositions on carbon substrate concentration could provide some key parameters or parameterization scheme for developing process-oriented model(s) of nitrogen transformation. Using a silt loam soil collected from a paddy field, we investigated the influence of carbon substrate concentration on the emissions of the denitrification gases, CO2 and CH4 from anaerobically incubated soils by setting two treatments: control (CK) with initial soil nitrate and dissolved organic carbon (DOC) concentrations of ~ 50 mg.kg-1 and -28 mg kg-1 , respectively; and DOC added (C + ) with initial soil nitrate and DOC concentrations of ~50 mg.kg-1 and ~300 mg.kg-1 , respectively. The emissions of denitrification gases, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each treatment were dynamically measured, using the gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that CH4 emission was not observed in CK treatment while observed in C treatment. Aggregate emission of greenhouse gases for C + treatment was significantly higher comparing with the CK treatment (P <0. 01). The mass fractions of NO, N20 and N2 emissions in total nitrogen gases emissions were approximately 9% , 35% and 56% for CK treatment, respectively; and approximately 31% , 50% and 19% for C+ treatment, respectively, with significant differences between these two treatments (P < 0.01). The results indicated that carbon substrate concentrations can significantly change the composition of nitrogen gas emissions. The results also implicated that organic fertilizer should not be applied to nitrate-rich paddy soils prior to or during flooding so as to mitigate greenhouse gases emissions.

[N2O emission from rice-rapeseed rotation system in Chengdu Plain of Sichun Basin].

By using static chamber/gas chromatograph techniques, the N2O emission from rice-rapeseed rotation system in Chengdu Plain of Sichuan Basin was measured from June 2005 to June 2006, with its characteristics and affecting factors investigated. The results showed that the total emission of N2O in a rotation cycle was (8.3 +/- 2.8) kg x hm(-2) x a(-1), and the emission in rice season, rapeseed season and fallow season accounted for 30%, 65%, and 5% of the total, respectively. In rice season, the mean N2O flux was higher during alternative drainage and irrigation than during continuous flooding and drainage, and was roughly the same during continuous flooding and drainage. N application was the main driving factor for the appearance of N2O emission peak, and the lower moisture content in surface soil layer in rapeseed season and fallow season was the main cause inducing soil N2O absorption. Soil moisture, soil temperature, N application, and crop involvement affected the N2O emission to various extents, and soil moisture was the key factor affecting the N2O emission. To avoid the high frequency of dry and wet alternation in rice season or to regulate soil moisture content to a level of 50%-70% WFPS (percentage of water-filled pore space) in rapeseed season and fallow season could effectively decrease the N2O emission from the rice-rapeseed rotation system.

[Estimation of chemical fertilizer N-induced direct N2O emission from China agricultural fields in 1991-2000 based on GIS technology].

Referring to the definition of agricultural field N2O emission factor by the Intergovernmental Panel on Climate Change, the main controlling factors climate and cropping system were introduced to estimate the chemical fertilizer N-induced direct N2O emission from China agricultural fields in 1991-2000, and a spatial inventory with 10 km x 10 km resolution was developed by dint of GIS framework. The results indicated that there was an increasing trend in the annual direct N2O emission, due to the increasing input of chemical fertilizer N. The mean annual emission in 1990s was estimated to be 204 Gg N2O-N, ranging from 159 to 269 Gg N2O-N, and the lowest and the highest emission occurred in 1992 and 1998, respectively. The uncertainty of the estimation was quantified to be about 23%. The spatial distribution of N2O emission was characterized by higher flux in eastern China and lower flux in western China, which was mainly attributed to the application rate of chemical fertilizer N and precipitation.

[Effect of organic material incorporation in rice season on N2O emissions from following winter wheat growing season].

In a field experiment, five fertilizer treatments including chemical fertilizer (CF), rapeseed cake + chemical fertilizer (RC + CF), wheat straw + chemical fertilizer (WS + CF), cow manure + chemical fertilizer (CM + CF), and pig manure + chemical fertilizer (PM + CF), were dedicated to examine the effect of organic materials incorporation in the rice season on N2O emissions from the following winter wheat season and to assess the climatic impacts from CH4 and N2O emissions in a rice-wheat rotation. Organic material was incorporated at the same rate (225 g x m(-2)) for organic treatments at the depth of 10 cm in the soil as the basal fertilizer just before rice transplanting. An identical synthetic nitrogen fertilizer was adopted for all treatments. Results show that the seasonal amount of N20 emissions from the following wheat season differed with organic material applied in rice season. No pronounced difference in N20 emissions was found between the CF and RC + CF treatments. In contrast with the CF treatment, however, N2O emission was decreased by 15% for the WS + CF treatment, but increased by 29% and 16% for the CM + CF and PM + CF treatments, respectively. Over the entire annual rotation cycle, N2O amount was increased by 17% for the CM + CF treatment, 7% for the PM + CF treatment, and 6% for the RC + CF treatment, but decreased by 16% for the WS + CF treatment in comparison with the CF treatment. Based on total emissions of CH4 in rice season and N2O over the entire rotation cycle, the estimation of combined Global Warming Potentials (GWPs) for CH4 and N20 shows that over a 20 years horizon or a 500 years horizon, the value of annual total GWPs was ranked in the order of RC + CF > WS + CF > CM + CF > PM + CF > CF or RC + CF > CM + CF > PM + CF > WS + CF > CF. The highest, middle and the lowest value of the GWPs per unit crop grain yield occurred for the crop residue, farmyard manure and pure synthetic fertilizer treatments, respectively. Compared to the chemical fertilizer treatment, accordingly, organic material combined with chemical fertilizer application in rice season increased climatic impacts from CH4 and N20 emissions in a rice-winter wheat rotation system.

[Effects of tillage-cropping systems on methane and nitrous oxide emissions from permanently flooded rice fields in a central Sichuan hilly area of Southwest China].

Using the static opaque chamber method, a field experiment was conducted in situ for two years to study the effects of three cultivation systems on CH4 and N2O emissions from permanently flooded rice fields in a hilly area in Southwest China. The results show that the average CH4 fluxes from a permanently flooded rice field with a single middle rice crop and flooded with no winter crop (PF) were (21.44 +/- 1.77) mg x (m2 x h)(-1) and (3.77 +/- 0.99) mg x (m2 x h)(-1) during rice-growing and non-rice growing periods, respectively, where both values were much lower than many previous reports from similar regions in Southwest China. The annual CH4 emission was mainly occurred in the rice growing period, being only 23.2% of the total annual CH4 flux emitted from the non-rice growing period, though the latter occupied two thirds of a year. The annual average flux of nitrous oxide was (0.051 +/- 0.008) mg x (m2 x h)(-1) and the N2O emission also intensive in the rice growing period. However, being only 8.1% of total annual N2O flux emitted from the non-rice growing period. After implementing the rice-wheat rotation (RW) and rice oil-seed rape rotation (RR), the CH4 emissions were reduced substantially, only 43.8% and 40.6% of those of PF, respectively. However, the N2O emissions were increased after conducting RW and RR systems, which were 3.7 and 4.5 times larger than those of PF. The global warming potentials (GWPs) of the CH4 and N2O emissions under the three tillage-cropping systems were assessed in an integrated way. The results show that the integrated GWPs of the CH4 and N2O emissions are in the following sequence: PF>>RR approximately equal to RR. Within 20, 100 and 500 years spans, the GWPs of the CH4 and N2O emissions of PF were 2.6, 2.1 and 1.7 times larger than those of RW (or RR), respectively. After introducing rice-wheat or rice oil-seed rape rotation systems into the permanently flooded rice fields, the integrated GWPs of the CH4 and N2O emissions were decreased largely.

[CO2 emission from soil-crop system as influenced by crop growth and tissue N content].

To understand the CO2 emission from soil-crop system as influenced by crop growth and tissue N content, pot and field experiments were carried out during 2001-02 wheat and rice growing seasons. Black chambers were used to take gas samples within a closed soil-crop system. The CO2 emission rate was detected by a gas chromatograph. Seasonal change of the CO2 emission was observed from the soil-crop system. Respiration from the soil-rice system was higher than that from the soil-wheat system. Dark respiration of the crop shoot was positively correlated to the shoot biomass. The respiration coefficient Rd, defined as the amount of CO2-C respired by per unit biomass C within one day under a reference temperature of 25 degrees C, can be well quantitatively expressed by shoot N content for either wheat or rice crop. Relationship between the Rd and the N content can be described as a linear regression of Rd = 0.0124N - 0.0076 (R2=0.9879, p<0.001) for the wheat crop and as a quadratic equation of Rd = 0.0085N2 - 0.0049N (R2=0.9776, p<0.001) for the rice crop, respectively. The crop roots promoted the soil respiration greatly, which increased by 178% for the wheat and 338% for the rice in comparison with the respiration from root-free soil. A further calculation of the root respiration, including root autotrophic respiration and rhizosphere respiration, suggested that the contribution of crop rhizosphere respiration to the total soil respiration was greater in the upland soil than that in the irrigated paddy soil.