【作者】 杨淑慧；

【导师】 王开运；

【作者基本信息】 华东师范大学 ， 生态学， 2012， 硕士

【摘要】 以碳为基础的温室气体排放对全球气候变化有重要的影响。增加或维持土壤碳的持有能力作为一种碳减排的替代性战略途径正在受到各国政府和科学家的重视。《京都议定书》提出可以通过增加生态系统中的碳库来补偿经济发展中的碳排放。不同管理措施强烈地影响着土壤碳库动态。河口湿地是陆地生态系统碳库的重要组成部分,具有独特的物质循环和能量收支方式,对人为或自然的干扰极为敏感。本研究以崇明东滩芦苇群落作为研究对象,跟踪监测了不同管理措施下土壤呼吸、芦苇生长、生理特征及土壤有机碳含量的变化,研究了不同管理措施对土壤呼吸季节动态及芦苇生长和生理特征的影响,分析了土壤呼吸动态变化规律及其控制因子,并结合土壤有机碳含量比较了管理措施对土壤碳持有能力的影响。以期为增加碳汇为目的的湿地管理提供科学依据。主要研究结论如下：1)土壤呼吸强度表现为：晚期刈割+还田(LMR,0.44±0.054mol·m-2·d-1)>对照(CK,0.39±0.052mol·m-2·d-1)>晚期刈割+不还田(LMNR,0.35±0.051mol·m-2·d-1)>早期刈割+还田(EMR,0.33±0.048mol·m-2·d-1)>早期刈割+不还田(EMNR,0.26±0.036mol·m-2·d-1)。LMR措施显著提高了土壤呼吸强度,也即增加了碳输出；而LEMR、EMNR、EMNR措施均不同程度的降低了土壤呼吸强度,即减少了碳输出；还田时土壤呼吸强度高于不还田(EMR>EMNR,LMR>LMNR,p<0.05),晚期刈割时土壤呼吸强度高于早期刈割(LMR>EMR,LMNR>EMNR,p<0.05)。2)土壤表层(5cm)温度和含水量能够很好地解释土壤呼吸的变化。单因子拟合结果表明土壤表层温度可以解释土壤呼吸变化的70.2%-87.3%,土壤表层含水量可以解释土壤呼吸变化的64.2%,而双因子拟合表明可以解释90%以上的土壤呼吸变化。3)土壤呼吸的季节变化与土壤表层(5cm)温度变化趋势一致,在2009年全年呈单峰曲线,均在8-9月份达到呼吸最大值,1-2月份达到呼吸最小值。对生长季和非生长季的土壤呼吸与表层土壤温度、含水量的分析显示,在植物的生长季表层土壤含水量是影响土壤呼吸的关键因子,而在植物的非生长季表层土壤温度是影响土壤呼吸的关键因子。4)在生长初期(4-5月份),管理措施均降低了芦苇株高,增加了基径,但单株生物量和叶面积差异不显著。生长后期,EMR措施增加了芦苇的株高和叶面积,但是总鲜重、总干重降低,基径无显著差异；EMNR措施增加了芦苇的株高、叶面积、总鲜重、总干重,基径无显著差异。管理措施对芦苇底面积的影响不显著,但均使芦苇顶叶面积显著增加。株高/基径×10-2这一指标揭示了管理措施可能造成芦苇的径向生长和横向生长的不协调。5)管理措施对光合生理特征的影响不同。还田促进光合生理进程,光合-光响应(Pn-PAR)曲线上调,表现出正效应,不还田则抑制芦苇的光合生理活动,Pn-PAR曲线下移。对光合参数的研究表明,管理措施导致最大净光合速率(Pmax)和光饱和点(LSP)下降。还田时,暗呼吸速率(Rd)和光补偿点(LCP)显著降低；不还田时,Rd和LCP显著增加。同时,管理措施均显著降低了植株气孔导度(Gs)和蒸腾速率(Tr),但增加了胞间C02浓度(Ci)以及水分利用效率(WUE)。6)不同管理措施导致土壤容重有一定程度的下降,表明管理措施对土壤结构有一定的改善作用。土壤有机碳含量及有机碳储量的变化趋势一致,均表现为EMR>LMR>CK>LMNR>EMNR,这说明不同管理措施可以显著地影响土壤有机碳的积累和分解,EMR、LMR措施可提高土壤有机碳含量,LMNR、EMNR显著降低土壤有机碳含量。7)通过土壤呼吸和土壤有机碳含量的差异性比较发现：EMR措施可以增加土壤的碳持有能力,EMNR、LMNR措施可以维持土壤的碳持有能力,而LMR措施效果不佳。更多还原

【Abstract】 The influences of carbon-based greenhouse gas emissions on global climate change have caused numerous attentions. Increasing or maintaining soil carbon holding capacity as carbon emissions reduction alternative strategic approaches is subject to the attentions of governments and scientists. The Kyoto Protocol proposed that we can increase carbon pools in ecosystem to compensate carbon emissions resulted from economic development. Different management practices have strong influences on the dynamics of soil carbon. Estuarine wetland, which has unique material circulation and energy budget, is an important part of terrestrial ecosystem carbon pools. It is extremely sensitive to human or natural disturbances.Phragmites community, which is typical vegetation in east Beach of Chongming Island, was taken as the research object. Mowing and straw returning of Phragmites, two main normal management practices in Phragmites production and wetland ecosystem, were carried out in the end of2008. Measurements of soil respiration、soil surface(0-5cm depth) temperature and humidity,together with growth and physiological characteristics and soil organic carbon content was conducted during the year of2009.The effects of management practices on soil respiration dynamics and related control factors were studied. At the same time, responses of growth and physiological characteristics of Phragmites to different management practices were also discussed. Futhermore, connecting with soil organic carbon content, the influences of different management practices on soil carbon holding capacity were compared. This study has great reference value for the management of wetlands with purpose of increasing soil carbon sequestration.The major results are summarized as follows:1)Under different management practices, annual average soil respiration showed that:late mowing+straw returning (LMR,0.44±0.054mol·m-2·-d-1)>control samples (CK,0.39±0.052mol·m-2·d-1)>late mowing+no straw returning(LMNR,O.35±0.051mol·m-2·d-1)> early mowing+straw returning (EMR,0.33±0.048mol·m-2·d-1)> early mowing+no straw returning (EMNR,0.26±0.036mol·m-2·d-1）.LMR increased soil respiration significantly, suggesting that increased soil carbon emission; however, LMNR,EMR,EMNR reduced soil respiration to varying degree, suggesting that reduced soil carbon emission; soil respiration under management of straw returning is higher than that of no straw returning(EMR>EMNR, LMR>LMNR, p<0.05), soil respiration under management of late mowing is higher than that of early mowing (LMR>EMR, LMNR>EMNR, p<0.05).2) The soil surface temperature and water content can explain changes of soil respiration well. Single factor fitting results showed that soil surface (5cm) temperature can explain70.2%-87.3%of soil respiration variation, soil surface (5cm) water content can explain64.2%of soil respiration variation, two-factors fitting results can explain more than90%of soil respiration variation.3) Seasonal variation patterns of soil respiration and soil surface (5cm) temperature are consistent, showed a single-peak curve in the year of2009, maximum of respiration was achieved during August-September, minimum of respiration was achieved during January-February. Respective analysis of soil respiration and soil surface (5cm) temperature、soil surface (5cm) water content during growing season and non-growing season indicated that:during growing-season, soil surface (5cm) water content is the dominant factor that affecting soil respiration; during non-growing season, soil surface (5cm) temperature is the dominant factor that affecting soil respiration.4) In the initial growth period (April and May), management practices reduced plant height and increased stem diameter significantly, however, differences of individual biomass and leaf area were not significant. During late growth stage, EMR increased plant height and leaf area, but reduced total fresh weight and total dry weight, stem diameter had no significant difference; EMNR increased plant height, leaf area, total fresh weight and total dry weight. Stem diameter had no significant difference. The area of bottom leave did not change remarkably, but the area of top leave increased significantly. The indicator that height/diameter×10-2indicated that management practices may result in uncoordinated between radial-growth and cross-growth of Phragmites.5) Responses of photosynthetic physiological characteristics of Phragmites to management practices were different. Straw-returning could promote photosynthetic physiological processes:the net photosynthetic rate-light intensity (Pn-PAR) curves moved upward, showing positive effects; no straw-returning restrain photosynthetic physiological activities with Pn-PAR curves jumping down. Study on photosynthetic parameters showed that management practices reduced maximum photosynthetic rate (Pmax) and light saturation point (LSP). Under the management of straw returning, dark respiration rate (Rd), light compensation point (LCP) reduced significantly; under the management of no straw returning, Rd and LCP increased significantly. All management practices in this research reduced stomatal conductance (Gs) and transpiration rate (Tr) significantly, whereas increased intercellular CO2concentration (Ci) and water use efficiency (WUE).6) Management practices lead to soil bulk density to a certain degree, indicating that management practices could improve soil physical structure. Changes of soil organic carbon content and organic carbon storage were consistent, presented as follows:EMR>LMR>CK>LMNR>EMNR, which suggest that management practices could affect accumulation and decomposition of soil organic carbon significantly. EMR and LMR could increase soil organic carbon content significantly, LMNR and EMNR could reduced soil organic carbon content significantly.7) Combining analysis of soil respiration and soil organic carbon, we can infer that:EMR could increase soil carbon holding capacity, EMNR and LMNR could maintain soil carbon holding capacity, effect of LMR on soil carbon holding capacity was unsatisfactory.更多还原