【作者】 赵晖；

【导师】 安树青；

【作者基本信息】 南京大学 ， 生态学， 2015， 博士

【摘要】 氮循环是滨海湿地最重要的物质循环之一。它不仅影响了湿地系统自身的调节机制,其在地球表层系统中所表现出的特殊动力学过程还与一系列全球环境问题息息相关。围垦是解决中国人口与土地资源短缺问题的一种有效手段,它能显著改变滨海湿地土壤的理化性质,影响植物的生长,进而影响生态系统的氮循环过程。为揭示围垦对滨海湿地氮循环的影响,从而将围垦活动对滨海湿地氮循环产生的不良影响减弱或缓解,本文以江苏盐城湿地珍禽国家级自然保护区的芦苇湿地和江苏省大丰麋鹿国家级自然保护区的碱蓬及互花米草湿地为研究对象,对比研究了自然湿地和被围垦湿地的氮循环特征,揭示了围垦对滨海湿地氮储存、迁移转化的影响过程;通过建立围垦影响下的植物-土壤系统的氮循环分室模型,揭示了围垦对滨海湿地氮循环的影响机制。结果表明:(1)围垦显著改变了滨海湿地的土壤理化性质,但对不同的生态系统具有不同的影响。围垦可以显著提高芦苇湿地表层土的含水量、有机碳、微生物量碳、碳氮比和微生物量碳氮比,但也使其土壤容重、pH、电导率和氧化还原电位显著降低。在碱蓬湿地中,围垦只显著降低了其土壤氧化还原电位,对其他土壤理化性质没有明显影响。与芦苇湿地相反,围垦可以显著提高互花米草土壤的容重、pH和氧化还原电位,而降低其含水量、电导率、有机碳、微生物量碳、碳氮比和微生物量碳氮比。(2)围垦对不同生态系统的土壤氮含量具有不同的影响。在芦苇湿地中,围垦显著提高了表层土的总氮、酸不溶性氮(惰性有机氮)、酸溶性氮(活性有机氮)、氨态氮、亚硝态氮和硝态氮含量。而在互花米草湿地中,围垦则显著降低了土壤的总氮、酸不溶性氮、酸溶性氮、水溶性有机氮、氨态氮、亚硝态氮和硝态氮含量。围垦对碱蓬湿地的土壤氮含量没有产生显著影响。逐步回归分析表明:在围垦影响下,滨海湿地土壤有机氮的主要影响因子为有机碳和微生物量碳,而无机氮的主要影响因子为含水量和电导率(盐度)。此外,围垦对三种典型湿地的土壤无机氮贮量没有显著影响;但显著提高了芦苇湿地的有机氮贮量,却降低了互花米草湿地的有机氮贮量,对碱蓬湿地的有机氮贮量则没有影响。这表明围垦是通过改变滨海湿地的土壤有机氮贮量,从而影响了其土壤总氮贮量。(3)围垦显著提高了芦苇湿地的土壤净氮矿化速率、氨化速率和硝化速率。与此相反,围垦显著降低了互花米草湿地的土壤净氮矿化速率和氨化速率。而由于围垦没有对碱蓬湿地的土壤理化性质产生影响,所以对其氮矿化过程也没有显著作用。逐步回归分析表明:在围垦影响下,土壤含水量是芦苇湿地土壤氮矿化的主要影响因子。此外,三种湿地中,土壤的氨化速率均远远大于硝化速率,这是由于滨海湿地的土壤含水量很高,土壤氮的氨化过程占主导,进而造成净氮矿化速率主要取决于氨化速率。(4)围垦显著提高了芦苇的根、茎、叶、种穗的生物量和氮贮量,但围垦后芦苇湿地的枯落物生物量和氮贮量有显著下降,这可能与其秋季的地上部分被收割有关。围垦没有改变碱蓬的生物量和氮贮量。但围垦显著降低了互花米草各器官的生物量和氮贮量。逐步回归分析表明:在围垦影响下,土壤电导率(盐度)是植物生物量的主要影响因子。同时,由于围垦没有影响三种植物各器官的氮含量,植物的氮贮量则主要由其生物量决定。(5)围垦极大地提高了芦苇植物-土壤系统的氮循环流通量,但对碱蓬植物-土壤系统的氮通量没有显著影响。与芦苇相反,围垦显著减少了互花米草植物-土壤系统的氮循环流通量。此外,在三种典型植物-土壤系统中,围垦区域均具有较高的氮素利用效率和氮再转移率,而其循环速度较慢,这表明围垦可以促进氮素的保留,防止氮素流失。基于本文的研究成果,作者认为围垦可以显著改变滨海湿地的氮循环过程。围垦通过改变滨海湿地的土壤理化性质,进而改变湿地土壤和植物氮含量,最终影响滨海湿地的氮循环过程。围垦对不同类型的滨海湿地氮循环具有不同影响。更多还原

【Abstract】 The nitrogen(N)cycle is one of the most important chemical cycles in coastal wetlands.It not only affected the self-regulation mechanism of wetland,but also showed a special kinetics process which was correlated with a series of global environmental problems in the Earth Surface System.Reclamation,as an effective means to solve the problem of population and land resources shortage in China,could significantly alter the soil physio-chemical properties and the growth of plant in coastal wetland,finally affect the nitrogen cycle of ecosystem.For understanding the effects of reclamation on the nitrogen cycle in coastal wetland which can alleviate the adverse effects of reclamation activities,we conducted some field experiments in Jiangsu Yancheng Wetland National Nature Reserve and Dafeng Milu National Nature Reserve to test the differences of soil nitrogen forms and distribution,soil nitrogen mineralization and plant nitrogen storages between natural and reclamation areas in three typical wetlands(Phragmites australis,Suaeda salsa and Spartina alterniflora).Meanwhile,based on the above studies,we established the nitrogen cycling model of these three plant-soil systems in response to reclamation by using the compartment model.The results indicated that:(1)Reclamation could change a lot of soil physio-chemical properties in coastal wetland.In P.australis marsh,reclamation significantly increased water content,organic carbon(OC),microbial biomass carbon(MBC),carbon-nitrogen ratio(C/N)and microbial biomass carbon-nitrogen ratio(MBC/MBN)in surface soil,but decreased bulk density,pH,electrical conductivity(EC)and oxidation reduction potential(Eh).In S.salsa marsh,except for soil Eh,no effect of reclamation on soil physio-chemical properties was found.In S.alterniflora marsh,reclamation significantly increased soil bulk density,pH and Eh,but decreased water content,EC,OC,MBC,C/N and MBC/MBN.(2)Reclamation had different influences on the soil nitrogen of three typical wetlands.In P.australis marsh,reclamation significantly increased the total nitrogen(TN),acid nonhydrolysable nitrogen(ANN),acid hydrolysable nitrogen(AHN),ammonium nitrogen(NH4-N),nitrite nitrogen(NO2-N)and nitrate nitrogen(NO3-N)contents in surface soils while no effect was found in S.salsa marsh.On the contrary,in S.alterniflora marsh,the soil TN,ANN,AHN,soluble organic nitrogen(SON),NH4-N,NO2-N and NO3-N contents were all decreased by reclamation.According to the regression analysis,we found that in coastal wetlands,soil OC and MBC which were changed by reclamation were the main factors to impact the contents of soil organic N,and the main influence factors on inorganic N were soil water content and EC(salinity).Moreover,reclamation significantly increased the soil organic N and total N storages in P.australis marsh,and largely decreased the same values in S.alterniflora marsh,but didn’t affect that in S.salsa marsh.And in all three wetlands,the storages of soil inorganic N were not altered by reclamation.This result indicated that reclamation altered the soil total N storage in coastal wetlands mainly by changing the soil organic N storage.(3)Reclamation significantly increased the soil nitrogen net mineralization rate(RN),soil ammonification rate(RA)and soil nitrification rate(RX)in P.australis marsh.At the same time,reclamation significantly decreased the soil RN and RA in S.alterniflora marsh,with no effect on the soil N mineralization in S.salsa marsh.According to the regression analysis,we found that in P.australis marsh,soil water content which was changed by reclamation was the main impact factor on soil nitrogen mineralization.In addition,we also found that soil Rx in all three typical wetlands was much lower than the soil RA,and it can be explained by the high soil moisture in coastal wetland.Therefore,the soil RN was mainly contributed by RA in our study.(4)Reclamation significantly increased the biomass and N storages of root,stem,leaf,seed and total in P.australis marsh,but decreased the litter biomass and N storage.And the biomass and N storages of each plant tissues in S.alterniflora marsh were all decreased by reclamation.According to the regression analysis,we found that soil EC(salinity)which was changed by reclamation was the main impact factor on plant biomass in coastal wetlands.Otherwise,reclamation also didn’t clearly affect the plant biomass and N storages in S.salsa marsh.Because the N concentrations in three typical plants were not largely changed by reclamation treatment,the plant N storage was mainly contributed by plant biomass.(5)Reclamation largely increased the N flux in nitrogen cycle of P.australis plant-soil system,while significantly decreased the N flux in nitrogen cycle of S.alterniflora plant-soil system,and didn’t affect the nitrogen cycle of S.salsa plant-soil system.Meanwhile,in these three typical plant-soil systems,reclamation areas all have higher nitrogen utilization efficiency and nitrogen re-translocation ability,but lower cycling speed,which could prevent the N from being lost easily.According to these researches,it is concluded that the reclamation can significantly change the nitrogen cycle of coastal wetland.Reclamation,by changing the soil physical and chemical properties,altered the soil and plant nitrogen content,and finally impacted the nitrogen cycling of coastal wetlands.Reclamation has different effects on the nitrogen cycle of different coastal wetlands.更多还原