鄱阳湖南矶山湿地不同植被类型对土壤碳组分、羧化酶及cbbl基因的影响

摘要

选取鄱阳湖南矶山湿地南荻群落(ND)、芦苇苔草混合群落(HH)、苔草群落(TC)、茭白群落(JB)及裸滩地(LT)土壤为研究对象,分析土壤中不同碳组分、固碳酶(1,5-二磷酸核酮糖羧化酶/加氧酶(RubisCO)酶活及其大亚基编码基因(cbbl)及环境因子对它们的影响.结果表明:土壤中全碳(TC)、有机碳(SOC)、微生物生物量碳(MBC)和可溶性有机碳(DOC)依次为6380~33830、1209~2259、124.6~1282、2.848~18.00 mg kg-1,其平均值变化表现为ND>HH>TC>JB;土壤中RubisCO酶活性在38.08~125.1 nmol CO2 kg-1 min-1之间,ND土壤RubisCO酶活性最高(125.1 nmol CO2 kg-1 min-1),TC最低(38.08 nmol CO2 kg-1 min-1);HH与JB的RubisCO酶活性分别为38.85、66.05 nmol CO 2 kg-1 min-1.土壤cbbl基因总拷贝数在36.07×104~195.6×104 copies g-1之间,ND最高,JB最低.相关性分析表明,MBC和DOC与cbbl基因均呈极显著正相关(p<0.01),而TC、SOC分别与RubisCO酶活性呈显著正相关关系(p<0.05).本研究结果说明,固碳酶及cbbl基因与各碳组分具有密切的关系,这对于进一步揭示鄱阳湖湿地土壤碳素循环及其微生物机制具有重要的参考意义.%[Objective] Soils are an essential section of the terrestrial carbon cycle and act as either source or sink for carbon,depending on what fraction the carbon is in and its stability. However,few studies have been reported on relationship between soil carbon fractions and carbon fixing process(Calvin-Benson-Bassham cycle)in wetland soil systems. Ribulose 1,5-bisphosphate carboxylase/oxygenase(RubisCO) is a key CO2 assimilation enzyme in the Calvin cycle,and its relationship with its large-subunit I gene and soil carbon fractions may provide some information about their relative importance to the genetic potential of CO2 fixation. Meanwhile,RubisCO enzyme activity and soil physicochemical properties were determined, and statistical analyses were performed to identify key factors driving microbial CO2 sequestration in wetland soils.[Method]In this study,soil samples were collected separately from wetlands under. Triarrhena lutarioriparia community(ND),Phragmites australis-Carex cinerascens community(HH),Carex cinerascens community(TC)and Zizania latifolia community(JB)and a bare shoal(LT)at Nanjishan of the Poyang Lake in China,for fractionation of soil carbon and analysis of soil organic carbon(SOC),soil microbial biomass C(MBC),and dissolved organic C(DOC),activity of RubisCO and its large-subunit I gene(cbbl).[Result]Results show that content of total carbon,SOC,MBC and DOC in the soils varied in the range of 6380~33830,1209~2259,124.6~1282 and 2.848~18.00 mg kg-1,respectively,and the four patches of wetlands displayed an order of ND > HH > TC > JB in terms of variation of their means. RubisCO activity in the soils varied in the range of 38.08~125.1 nmol CO2 kg-1 min-1 and was the highest in ND reaching 125.1 nmol CO2 kg-1 min-1 and the lowest in TC falling down to 38.08 nmol CO2 kg-1 min-1. Total number of copies of cbbl genes in the soils varied in the range of 36.07×104~195.6×104 copies g-1,being the highest in ND(195.6×104 copies g-1)and the lowest in JB(36.07×104 copies g-1). RDA analysis indicates that the main factors affecting distribution of soil carbon fractions are Total N,pH,catalase activity and sucrase activity;and soil total N is the most important factor affecting soil carbon fractionation,followed by pH. Correlation analysis indicates that Total N and sucrase activity are positively related(p<0.01), while pH and catalase activity negatively related to carbon fractionation(p<0.01). The contact of the soil with the atmosphere might lead to a significant negative relationship between soil catalase and carbon. The correlation between MBC and carbon cbbl gene is the strongest,followed by DOC,which shows a significant positive correlation with cbbl gene(p<0.01),while total C and SOC are significantly and positively related to RubisCO activity(p<0.05). [Conclusion]All the findings in this study suggest that soil carbon fixation enzyme and cbbl gene are positively correlated with soil carbon fractionation,which improves our knowledge of their roles in carbon sequestration and nutrient turnover. Obviously the study is of great significance to further researches on soil carbon cycle and its microbial mechanism in Poyang Lake wetlands.