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Mechanism Study On Vegetation Succession Influencing Soil Carbon Sequestration In Coastal Alkali-Saline Soil

Posted on:2018-11-14Degree:MasterType:Thesis
Country:ChinaCandidate:N LiFull Text:PDF
GTID:2370330575975241Subject:Marine science
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Soil carbon pool is the largest carbon pool in terrestrial ecosystem,which is very important to global carbon cycle.Widely distributed coastal alkali-saline soils in China is a potential carbon sink that can not be ignored.The development and utilization of coastal alkali-saline soils resources as well as improving the carbon sequestration capacity of coastal alkali-saline soils is beneficial to the mitigation of global warming.In this study,the basic physical and chemical properties of typical vegetation successions in coastal alkali-saline soils in Dafeng City in Jiangsu Province were analyzed,including the soil physicochemical properties of BS,SL,IG and JF.In order to explore the changes of soil carbon components and the main physical and chemical factors affecting carbon sequestration during vegetation succession,soils organic carbon,soil microbial biomass carbon and soil dissolved organic carbon of different vegetation types were measured.At the same time,soil enzyme activities(urease,catalase,invertase and alkaline phosphatase)during the vegetation succession were studied.Correlations between of soil organic carbon,soil bulk density,soil pH,soil enzyme activities,total nitrogen and total phosphorus were analyzed.In addition,the variation and abundanceof soil microbial diversity in different vegetation groups was studied by using second-generation sequencing technology and the correlation between soil physicochemical properties and microbial diversity index was also discussed.The main components of root exudates and the changes of soil mineral composition in coastal alkali-saline soils were analyzed.Carbon Sequestration and Jerusalem artichoke biomass under nitrogen applications was also discussed.The results provide reference basis for the efficient use of agricultural resources in coastal saline alkali land and the promotion of carbon sequestration.The main results are as follows:1.pH value,soil electrical conductivity and soil bulk density decreased during process of vegetation succession in coastal alkali-saline soils,while soil organic carbon and total nitrogen showed an increasing trend,which indicated that the vegetation succession decreased the salt content and carbon mineralization enhanced under the action of vegetation and microorganism conducive to improving the soil porosity and water seepage characteristics,improving soil fertility.2.The SOC contents of different vegetation types at 0-10cm and 10-20cm soil layers were ranked in the order:BS<SL<IG<JF.The ratios of MBC/SOC and DOC/SOC of Jerusalem artichoke were higher than that of the other three types.The maximum ratios of MBC/SOC and DOC/SOC were 4.67%and 0.45%,respectively,indicating that the soil microbial activity was higher in the Jerusalem artichoke,which was beneficial to improve soil carbon sequestration in coastal alkali-saline soils.3.The increases in the activities of soil urease,catalase,invertase and alkaline phosphatase were ranked in the order:BS<SL<IG<JF.Soil urease and invertase activity were significantly positively correlated with soil organic carbon(P<0.01).The activities of urease,invertase and alkaline phosphatase were significantly negatively correlated with soil electrical conductivity(P<0.01).There was a significant positive correlation between soil urease activity and invertase activity(P<0.01),while there was a significant positive correlation between soil catalase and invertase activity(P<0.01).4.In the soil samples of different soil types(BS,SL,IG,JF),Proteomics,Acidobacteria,Chloroflexi,Bacteroidetes and Gemmatimonadetes were the five most dominant phyla,accounting for 86.6%of the total bacteria.The species richness of each species varied according to different types of vegetation and soil depth.The species richness of 0-10 and 10-20cm soil layer was:BS<SL<IG<JF.Chao 1 index and Shannon index increased with vegetation succession.C/N and SOC are the main factors affecting the distribution of soil community in succession of vegetation communities in coastal alkali-saline soil.Soil microbial diversity index and soil enzyme activity have a certain correlation.A total of 529 different species were found in all soil samples,of which 27 showed significant differences in different soil samples.Soil electrical conductivity,organic carbon and soil water content were the main factors affecting the soil microbial diversity index of vegetation succession in coastal saline soil.5.The types of root exudates of BS,SL,IG and JF were 51,37,50 and 19,respectively.Di-n-octyl phthalate and 9-Octadecenamide were the coexistent root secretion during the succession of vegetation communities.The main minerals in the alkali soil were quartz,albite,illite,calcite,vermiculite and muscovite.6.Five nitrogen fertilization rates were tested(in g urea m-2):0,4,8,12 and 16.The biomass of different organs of Jerusalem artichoke during the growth cycle was significantly higher in 8 g·m-2 than the other treatments.Under different nitrogen treatments,carbon density in organs of Jerusalem artichoke ranged from 336 to 419 g C kg-1.Carbon sequestration in Jerusalem artichoke was higher in treatments with nitrogen fertilization compared to the CK treatment.The highest carbon sequestration in Jerusalem artichoke and soil was found in the N2 treatment.Carbon sequestration in both soil and Jerusalem artichoke residue was increased by nitrogen fertilization depending on the rates in the coastal alkali-saline soil studied.The results showed that the succession of vegetation community in coastal alkali-saline soil in Dafeng City in Jiangsu Province was beneficial to improve soil physicochemical properties and soil carbon sequestration efficiency.The succession process of vegetation community was beneficial to improve soil enzymic activities as well as soil microbial diversity.Soil carbon fraction,soil enzyme activity and soil microbial diversity had certain correlation between each other.Vegetation types,environmental factors and stress conditions all affected the type and quantity of root exudates.The amount of carbon fixation of Jerusalem artichoke and soil carbon sequestration reached the maximum in the range of nitrogen fertilizer level.
Keywords/Search Tags:Vegetation community succession of alkali-saline soil, Soil organic carbon, Soil enzyme activity, Soil microbial community, Root exudates, Soil mineral, Jerusalem artichoke
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