【摘要】 研究红树林湿地土壤可溶性有机质(DOM)的来源、性质及其归宿对于揭示DOM在红树林湿地生物地球化学循环中的作用具有重要意义。采集了木榄(Bruguiera gymnoihiza)、秋茄(Kandelia candel)和桐花树(Aegiceras corniculatum)3种红树植物的新近落叶进行室内48 d分解实验,探讨了凋落叶分解过程对土壤可溶性有机碳(DOC)和可溶性总氮(TDN)含量、C/N比(DOC/TDN)及紫外-可见(UV-Vis)光谱特征(A280、A240/A420和A250/A365比值)的影响。在48 d分解期间,3种红树植物凋落叶的输入均明显增加了土壤DOC的含量,其变化在分解第6 d最为显著,各凋落叶添加组比对照组平均增加了149%(秋茄)~196%(桐花树),随后各凋落叶添加组土壤DOC含量呈下降趋势。与土壤DOC的变化不同,凋落叶输入后土壤TDN的变化与对照组的差异不明显,但木榄和桐花树添加组的C/N比在分解初期(第6天)显著高于对照组(P<0.05)。凋落叶的输入亦在不同程度上增大了土壤DOM的A280值,降低了DOM的A240/A420和A250/A365比值。与土壤DOC的变化相似,凋落叶输入使DOM的UV-Vis光谱特征在分解初期(第6天)的变化最明显,其中桐花树凋落叶的影响最大,秋茄凋落叶的影响最小。结果表明:凋落叶输入使培养初期土壤DOM的含量和性质发生明显改变,DOM中大分子及芳香类组分增多、团聚化程度增加,DOM的生物可降解性变小。然而,随着分解的进行,不同凋落叶处理组之间土壤DOM的变化差异性逐渐缩小,并在分解后期与对照组趋近。更多还原

【Abstract】 Understanding the sources,properties and fates of dissolved organic matter(DOM) in mangrove wetland soils is of significance to reveal the role of DOM in biogeochemical cycles in mangrove wetlands.A 48-day soil incubation experiment was conducted with addition of nearly-senesced leaves of mangrove plants(Bruguiera gymnorrhiza,Kandelia candel and Aegiceras corniculatum) to investigate soil DOM changes during mangrove leaf litter decomposition.Soil samples were collected after 6,12,18,26,36 and 48 days of incubation,and the concentrations of dissolved organic carbon(DOC) and total dissolved nitrogen(TDN),C:N ratio(DOC:TDN) and spectrophotometric absorbance(A280,A240/A420 and A250/A365 ratios) in soil solutions were analyzed.Results show that DOC concentrations in soil solutions were significantly increased by the addition of mangrove leaf litters,and reached the maximum after 6 days with an average increase of between 149%(K.candel) and 196%(A.corniculatum) compared with the control treatment without litter addition,followed by a decrease trend during later incubation periods,while those of control treatment remained fairly steady after a drop by day 6.Only slight change was observed for TDN content after input of leaf litter,while the C∶N ratios of soil solutions were significantly higher than those of control treatment(P<0.05) during the early decay of B.gymnorrhiza or A.corniculatum leaf litter.The spectrophotometric absorbances of soil solutions were also influenced by litter addition with an increase in A280 value and decrease in A240/A420 or A250/A365 ratio,noticeably for A.corniculatum leaf litter treatment but minimally for K.candel leaf litter treatment after 6-day incubation.These results suggested that litter input and decomposition strongly influenced contents and properties of DOM in soil,especially during the initial decomposition stage,resulting in enhancement of higher-molecular components and aromatic compounds,and a decline in bioavailability of DOM.However,difference of DOM contents among litter treatments shrinked with further litter decay,and the properties of DOM became chemically similar to those of control treatment at the end of incubation.更多还原