互花米草盐沼土壤有机碳库组分及结构特征

在江苏盐城互花米草(Spartina alterniflora)盐沼建立以下样地:光滩(Mudflat)、互花米草建群1a(S.alterniflora flat 2011)、5a(S.alterniflora flat 2007)、12a(S.alterniflora flat 2000)、23a(S.alterniflora flat 1989)以及碱蓬(Suaeda salsa flat 1989),采集表层土壤样品,分析土壤中的活性有机碳(可溶性有机碳、微生物量碳)特征,并利用核磁共振波谱法测定土壤总有机碳的结构图谱,研究互花米草盐沼土壤有机碳库组分及结构特征。结果表明:(1)互花米草建群后,盐沼表层土壤有机碳含量显著增加(P0.05),在0.82—7.6 g/kg之间,各样地表层土壤有机碳含量为:互花米草滩(5.57 g/kg)碱蓬滩(2.4 g/kg)光滩(1.05 g/kg);可溶性有机碳含量为:互花米草滩(36.08 mg/kg)碱蓬滩(17.43 mg/kg)光滩(6.92 mg/kg);微生物量碳含量为:互花米草滩(52.51 mg/kg)碱蓬滩(18.27 mg/kg)光滩(13.56 mg/kg)。互花米草建群后,土壤中活性碳库含量显著增加(P0.05)。(2)土壤有机碳结构以烷氧碳和芳香碳为主,其中芳香碳的平均比例(35.85%)最高,其次为烷氧碳(32.83%)和羧基碳(20.62%),烷基碳的平均比例(10.36%)最低,其中建群5a的互花米草样地(SAF2007)土壤芳香碳、烷氧碳、烷基碳含量最高,建群23a的互花米草样地(SAF1989)土壤羧基碳含量最高。(3)互花米草盐沼土壤中烷基碳/烷氧碳为:SAF2007(0.44)SSF1989(0.43)SAF2000(0.28)SAF2011(0.27)SAF1989(0.22);疏水碳/亲水碳为:SAF2007(0.97)SSF1989(0.87)SAF2000(0.85)SAF2011(0.83)SAF1989(0.81)。烷基碳/烷氧碳在建群5a后达到最高值0.44,烷基化程度最高;疏水碳/亲水碳达到最高值0.97,土壤碳库稳定性高于其它样地。

Characterization of soil organic carbon fractions at Spartina alterniflora saltmarsh in North Jiangsu

Spartina alterniflora was introduced into China in 1979, and the first plantation of S. alterniflora was successfully constructed in Jiangsu province in 1982. Since it expanded quickly on coastal wetlands, great attentions were paid to its positive and negative effects on native ecosystems. In order to study the components and structural characteristics of soil organic carbon (SOC) pool of S. alterniflora saltmarsh, field observations and soil sampling work were fulfilled at permanent study sites including mudflat (MF), S. alterniflora salt marsh of 1-year (SAF2011), 5-year (SAF2007), 12-year (SAF2000), 23-year (SAF1989) and Suaeda salsa saltmarsh (SSF1989) along the coastal wetland in Yancheng, where located the largest area of S. alterniflora saltmarsh in China. The topsoil SOC, dissolved organic carbon (DOC) and microbial biomass carbon (MBC) were analyzed, and nuclear magnetic resonance (NMR) spectroscopy was utilized to explore the structure of soil organic carbon. The results showed that: (1) the development of S. alterniflora promoted the soil organic carbon sedimentation. The range of SOC was between 0.82-7.60 g/kg, which occurred as the order of S. alterniflora saltmarsh (5.57 g/kg) > S. salsa saltmarsh (2.4 g/kg) > mudflat (1.05 g/kg); the DOC occurred as the order of S. alterniflora saltmarsh(36.08 mg/kg) > S. salsa saltmarsh(17.43 mg/kg) > mudflat(6.92 mg/kg); the MBC occurred as the order of S. alterniflora saltmarsh(52.51 mg/kg) > S. salsa saltmarsh(18.27 mg/kg) > mudflat(13.56 mg/kg). These indicated that the soil active organic carbon pool was enhanced by the development of S. alterniflora. (2) The SOC contained more alcoxyl and aromatic carbon than other carbon fractions. The average proportion of SOC fractions occurred as the order of aromatic carbons(35.85%)> the alcoxyl carbon (32.83%) > carboxyl carbon (20.62%) > alkyl carbon (11.76%). The highest value of aromatic carbons, alcoxyl carbon and alkyl carbon occurred at the 5-year S. alterniflora saltmarsh(SAF2007), while the highest value of carboxyl carbon occurred at the 23-year S. alterniflora saltmarsh(SAF1989). (3) The ratio of alkyl carbon/alcoxyl carbon in topsoil occurred as the order of SAF2007 (0.44) > SSF1989 (0.43) > SAF2000 (0.28) > SAF2011(0.27) > SAF1989 (0.22); the ratio of hydrophobic carbon/hydrophilic carbon occurred as SAF2007 (0.97) > SSF1989 (0.87) > SAF2000 (0.85) > SAF2011 (0.83) > SAF1989 (0.81). The highest ratio of alkyl carbon/alcoxyl carbon (0.44) and hydrophobic carbon/hydrophilic carbon (0.97) occurred at the 5-year S. alterniflora saltmarsh(SAF2007), indicating the highest degree of alkylation and stability of SOC pool.