| Incubation experiments to enrich nematode were carried out by adding two types of organic matter (pig manure and rice straw) to paddy soil and upland soil, respectively. Based on this, the effect of soil nematodes on emission or consumption of greenhouse gases (i.e. CO2, N2O and CH4) from paddy soil and upland soil at different temperatures and moisture were investigated. The results obtained showed that:1) The increase in amount of nematode from paddy soil was more significant compared to that from upland soil after in situ enrichment incubation, while the reproduction of nematode in soil were promoted more obviously with pig manure addition than with rice straw. After mediums were added to two soils, the amounts of nematode were determined and showed as follows: high density > low density > control. In situ enrichment incubation method , the number of paddy soil nematode increases significantly than upland soil. Addition of pig manure can significantly promote the soil nematode reproduction than straw. and in the different soil added with matrix, the measured high density nematode number > low density nematode number >control nematode number.2) The selection of the optimal time for gas sampling of CO2, N2O and CH4. Nematode soil after enrichment incubation was incubated for 24h at 20℃, and the fluxes of CO2, N2O and CH4 were determined at 3h interval during the incubation period. The results showed that the emission fluxes of N2O and CO2 were increased, whereas flux of CH4 was decreased at 12h of incubation. It is determined to sampling time of the three greenhouse gases (CO2, CH4 and N2O) by measuring the emission flux of CO2, CH4 and N2O once every three hours. It can be obtained that at the first 12h when measuring the emission flux increased CO2 and N2O, the absorption flux of CH4 decreases.3) Effect of soil temperature and water content on CO2, N2O and CH4 emissions from paddy soil and upland soil.Two treatments (with high or low density of nematode) and control of paddy soil, which were enrichment cultured with pig manure or rice straw addition before, were incubated at six gradient temperatures (5, 10, 15, 20, 25 and 30℃) for determining the fluxes of CO2, N2O and CH4. The results showed that CO2 flux increased significantly with incubation temperature varying from 5℃to 30℃(p<0.05), while N2O flux increased gradually from 5℃to 20℃,but decreased to 30℃(p<0.05). However, CH4 flux has not significant changes among all incubation temperatures and showed consumption through the incubation. In addition, another soil incubation experiment was conducted at 20℃under six gradient water contents (15%, 20%, 25%, 30%, 35% and 40%) to investigate CO2, N2O and CH4 fluxes. The results showed that CO2 flux was increased with increasing soil water content from 15% to 40% (p<0.05), while the N2O emission increased significantly from 15% to 30% but 40% was decreased gradually (p<0.05). With increasing soil water content from 15% to 30%, CH4 was increased but did not reach significant level, however, CH4 consumption was converted to CH4 emission when soil moisture were elevated from 30% to 40%. The upland soil is similar to the paddy soil in the tendency of emission and consumption of three gases, with the exception of flux value. By contrast, emission flux of gases from the upland soil was lower than that from paddy soil, and was about 50% of that from paddy soil. The fluxes of gases emitted from both pig manure and rice straw treated soil showed as follows: high density>low density>control. Under different temperature and moisture condition, the influence of the paddy soil and upland soil on the emission greenhouse gases. Adding pig manure or adding straw soil enrichment, Make different density of nematodes and control of soil in 5℃, 10℃, 15℃, 20℃, 25℃and 30℃for culture, and measure the emission/absorption flux of CO2, CH4 and N2O. The results show that, in the temperature range of 5℃30℃, it is significant difference that CO2 emission flux increasing (p<0.05) with the increasing of temperature; the emission flux of N2O gradually increases in the temperature range of 5℃20℃but gradually reduce in the temperature range of 20℃30℃, significant difference (p<0.05), it is show that no obvious difference absorption state of CH4 at 5℃30℃. At temperature of 20℃, it is measure three kinds of greenhouse gases at 15%, 20%, 25%, 30%, 35%, 40% moisture content, the results shows that, it is significant difference that CO2 emission flux increasing (p<0.05) with the increasing of moisture content at 15%～40%. it is increasing of N2O at 15%～30% moisture content, it will decrease that emission flux of N2O at 30%～40% moisture content. CH4 absorption will increase with the increase of moisture at 15%～30%, and that is not significant, that will be emission at 30%～40%. Upland soil test as same way as paddy soil and emission trends in the same. However, the results of emission/absorption is a little different, it is showing that the affected emission/absorption numerical with paddy soil in different, and emission flux is low which is about 1/2 of the Paddy soil. No matter it is the pig manure or straw as a matrix of different density nematode, it shows that the emission flux that high density nematodes > low density nematodes > control of soil nematodes. |
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