The Factors Of Greenhouse Gas Emissions And GWP Of Salinization Paddy Field In Western Jilin

Stalinization of soil in arid, semi-arid,even semi-humid region is a world-class resource and ecological problem. Songnen Plain is one of the world’s three largest saline soil areas. The area of saline soil in Jilin Province is2.18×106hm2, which account for11.5%of the total area.1/5of the saline area is developed into farmland which is not fertile enough for dry farming, so the crop production is low. The Jilin western land development project aim to diverse Songhua River and Nen River to improve saline field into high yield paddy field. Researches about saline soil improvement, greenhouse gas emission and soil carbon storage are very common in both domestic and abroad. These researches have made a certain progress with mature technologies. A research group led by Professor also has carried out relevant researches in western Jilin. In the previous studies, the data of greenhouse gas emission and soil carbon storage came from either a model or an average of experimental samples. However, paddy fields of different age have big differences in physicochemical property of soil anf greenhouse gas emission.Both the two ways did not take these differences which have great influences on the results into accountIn such circumstance, under the support of National Natural Science Foundation "Research on Luce’s Impact on Soil Organic Carbon in The West of Jilin for Fifty Years and Its Drive Mechanism" and "Research on All-year Soil Organic Carbon Changing Mechanism in Jilin Salinization Paddy Field Area and The Warming Potential Trend" led by my tutor, through outdoor field sampling and community experiment, this research stimulates the impact of different nitrogen fertilizer amounts on greenhouse gas emissions of newly-developed and mature paddy fields, analyses the relationship between rice cultivation and soil physical nature, calculates paddy field organic carbon density and greenhouse gas flux in different developing years, estimates soil organic carbon reserve and the total emissions of greenhouse gas, explores salinization paddy field area’s clean warming potential trend in the west of Jilin. The results are significantly meaningful in exploring the impact of land consolidation on regional greenhouse gas emission, soil organic carbon accumulation and regional carbon cycle status, in providing regional local basic data support for global climate change,etc., and they are as follow:Rice cultivation has great impact on salinization paddy field soil physical nature of the west of Jilin:soil pH declines to8.16-8.47from9.72-9.93before exploration; soil conductivity declines to0.35～0.44mS/cm from1.27～1.38mS/cm; soil nitrogen hydrolysis rises to70.16～92.48mg/kg from27.89-33.51mg/kg; soil organic carbon rises to16.58～21.59g/kg from2.36～2.53g/kg. Soil physical nature is influenced by the combined effects of rice plant growth, climate and microorganism, and in it Nitrogen’s impact on soil nitrogen hydrolysis is obvious. Land consolidation project will transform the original extremely-strong Alkalined, severe salinized, poor nutritioned saline soil into Alkalined and strong Alkalined, moderate and mild salinized, high content of carbon organic and nitrogen paddy field soil, and it has positive affect on regional soil environment improvement.CO2emission flux increases along with increase in years of paddy field exploration and the annual rate of change is close; CH4emission flux appears an increasing trend at early stage of paddy field development, declines in the plots that the development years are over35years, plots that the development years are over55years has the biggest emission flux; the trend of N2O emission flux is first decline and then increase; along with the increase of exploration yeas, accumulated total emission of CO2、CH4、N2O three greenhouse emission are all in the increasing trend. Soil physical nature mostly influence greenhouse gas emission through composite or indirect way. Under0.05significant status, annual emission flux and accumulated total emission of three kinds of greenhouse gases CO2、CH4、N2O have no relation with soil pH value; with soil conductivity value appears functional correlation and is negative; with soil nitrogen hydrolysis and organic carbon appears functional correlation and is positive.There is little difference between mature and newly-developed paddy field areas in the greenhouse gas emission characteristics during the growing season in the saline paddy field areas in the west of Jilin, CO2emission flux rises along with the growth of the rice and keeps high in rice tillering stage, jointing and booting stage and maturity, in mid-July and mid-August(flowering stage), CO2emission flux has an obvious low value. It keeps fluctuating when reaches the peak during jointing and booting stage and has another peak in the flowering stage, then emissions gradually fall, seasonal average emission flux of CH4appears a signal peak trend;CH4gas emission characteristics of newly-developed and mature paddy fields are basically the same, the difference is CH4gas emission low value of mature paddy field appears in mid-August but this phenomenon hasn’t been observed in newly-developed paddy fields. Under no-nitrogen treatment, N2O emission appears fluctuated trend,it has no obvious peak, emissions are small and influenced by fertilizing. Compared with mature paddy field, average emission flux and total emission of three greenhouse gases are both obviously low for newly-developed paddy-field, excluding the impact of nitrogen and temperature, it mainly related with soil physical nature, mainly related with high soil pH, large salinity, available nitrogen and low soil organic content.Nitrogen application has obvious influence to CO2emission flux on both newly-developed and mature paddy field, but hasn’t influenced its variation, CO2emission characteristics are largely influenced by temperature and rainfall, nitrogen boosts CO2emission mainly through affecting soil nitrogen hydrolysis and organic carbon content. Accumulated CO2emissions of two kinds of paddy fields increase significantly along with the amount of nitrogen fertilizer, fertilizing to some degree raises paddy field’s CO2emission rate.Nitrogen application’s impact on CO2emission flux is obvious at the beginning,mainly for under the effect of nitrogen, CH4emission’s peak of mature paddy field rises significantly compared with no-nitrogen, but the emission peaks of PN60(mature paddy field low amount of fertilizer150kg/hm2) and PN150(mature paddy field conventional fertilizer150kg/hm2) under different treatment has little difference, PN250(mature paddy field high amount of fertilizer250kg/hm2)rises obviously compared with emissions under other treatments, a comparatively large peak appears in mid-July. Under N250treatment, CH4seasonal accumulated emissions of newly-developed and mature paddy fields have significant increase comparing NO treatment, under N60and N150treatments, CH4seasonal accumulated emission increased obviously comparing non-nitrogen treatment, but has little impact on newly-developed paddy field.To mature paddy field N2O emission flux, nitrogen application only brings the appearance of emission peak, compared with mature paddy field, the emission peak is low after the nitrogen is applied into newly-developed paddy field,but N2O emission flux increases obviously in other times. Under NO and N60treatments, N2O emission seasonal accumulation’s ratio of the total during every growth period is comparatively average. Under N150and N250treatments, because of the significant increase of N2O average flux, seasonal accumulation’s ratio in turning green period is greatly higher than other growth periods. CO2accumulated emission of CO2greatly increase along with the amount of nitrogen. Greenhouse gas emissions (take CO2in account) of both newly-developed and mature paddy fields increase along with the increase of nitrogen fertilizer, it reflects that nitrogen has great impact on regional comprehensive greenhouse effect. Since CO2emission is huge, the contribution rate dominates in all treatments; CH4contribution rate is obviously higher than N2O,it reflects that CH4emission in paddy field has great impact on regional comprehensive greenhouse effect.Soil organic carbon density of paddy field region in the west of Jilin increases along with paddy field’s exploration age, and the increasing rate gradually reduced; vertical distribution of soil carbon density appears as progressively decreasing along with the increasing depth. Regional soil organic carbon reserve has been kept increasing for20years, organic carbon reserve respectively are3.84x106t、7.85x106t、21.03x106t and28.38x106tin1990、2000、2012and soil consolidation completion year, average soil organic density are95.10t/hm2、108.07t/hm2、87.03t/hm2and55.46t/hm2.20years from1990to2012the research area has been in carbon sequestration process, total solid carbon of paddy field is7.19x106t, after the land consolidation project finish, it is predicted that regional soil solid carbon would reach7.34×106t and is benefited to regional soil carbon sequestration. Paddy field’s soil organic carbon in this region is lower than national average status in general in this region, since the exploration year of paddy field are short, its soil organic carbon density is in a medium-low standard, but still has huge solid carbon potential.To accumulate CO2、CH4and N2O three kinds of greenhouse emissions (take CO2in account) and contribution rates in different development ages of paddy fields gives a result:CH4and N2O two gases’ standards are same in turning green period, the former has a slightly advantage to the latter in maturity; in rice tillering, jointing and booting and flowering stages, contribution rate of CO2emission falls, CH4’s contribution to greenhouse effect increases, greatly higher than N2O.Paddy fields’ total greenhouse gas emission (take CO2in account) of different developed year present an increasing trend, CO2emission stands in a main position, the contribution rate is nearly80%,contribution rate of CH4is16.69%～20.39%, N2O0.93%～1.37%, CH4emission plays an important role in greenhouse effect. Greenhouse gas emissions of developed over one year, over five years, over fifteen years, over twenty-five years, over thirty-five years and over fifty-five years are respectively2,152.76gCO2-eqv/m2、2,565.49gCO2-eqv/m2、2,889.53gCO2-eqv/m2、3,176.82gCO2-eqv/m2、3,358.77gCO2-eqv/m2和3,493.54gCO2-eqv/m2.Average amounts of three kinds of greenhouse gas emissions were2,102.32g/m2·a、18.31g/m2·a和101.90mg/m2·a. The average CO2emission rate was in the range of northeast farmland CO2emission amount, in the medium level in the country; CH4emission amount was a little higher than parts areas, but far less than national level; the average N2O emission amount was in lower level of the country, in2012.GWP of salinization paddy field in Western Jilin were1.07×106tCO2-eqv.1.99×106tCO2-eqv.、6.26×106tCO2-eqv. and12.07×106tCO2-eqv. in1990,2000,2012and the year after project completed. It shows that the area released carbon in these years, contributed to global warming. This result is in good agreement with the research of Xu XiaoMing PhD.Most of the previous researches simply concentrated on regional organic Carbon Sequestration or greenhouse gas emission, or use models to stimulate the balanced relation between the two; base on a real situation that the coverage, greenhouse gas emission and soil organic carbon density of different base year paddy fields with different exploration years are all different, accumulates research area’s organic carbon reserve and greenhouse gas emission by using the measured data, estimates clean warming trend before and after land consolidation. Result of the research has positive theoretic value and practical meaning in exploring rice cultivation’s real contribution to regional warming effect and comprehensively judging land consolidation’s impact to regional ecological environment, etc.