模拟盐水入侵对河口湿地土壤碳矿化潜力的影响研究

Effects of simulating saltwater intrusion on soil carbon mineralization potential in estuarine wetlands

河口湿地在全球陆地生态系统碳循环中具有重要作用,为了揭示盐水入侵对河口湿地土壤碳矿化潜力的影响,以闽江河口淡水湿地为研究对象,采用室内泥浆厌氧培养与气相色谱法相结合的方法,通过设置高频率盐度梯度的盐水入侵情景模式,对不同处理下的土壤碳矿化潜力(以CO_(2)产生潜力表征)及其环境调节因子进行连续3周的测定与分析.研究结果表明:(1)不同盐度处理下土壤pH值均低于对照处理(0),氨态氮(NH_(4)^(+)-N)含量均高于对照处理,且随盐度增加而增加,可溶性有机碳(DOC)含量在盐度25‰、30‰处理下高于对照处理,SO_(4)^(2-)含量在盐度20‰、25‰、30‰处理下高于对照处理;(2)随着时间的变化,厌氧培养第1周CO_(2)产生潜力显著高于第2周和第3周(p<0.05),不同盐度处理CO_(2)产生潜力差异较大,表现为低盐度(0.5‰~10‰)促进和高盐度(15‰~30‰)抑制作用,盐度10‰~15‰可能是影响土壤碳矿化转变的重要转折点;(3)不同盐度处理下CO_(2)产生潜力与土壤pH值呈显著正相关,与土壤电导率(EC)、NH_(4)^(+)-N、Cl^(-)、SO_(4)^(2-)和DOC呈显著负相关(p<0.05).盐度是影响河口湿地土壤碳矿化的的重要因素,低盐度的盐水入侵促进河口湿地土壤碳矿化,高盐度的盐水入侵抑制土壤碳矿化.

Estuarine wetlands play an important role in global terrestrial ecosystem carbon cycles.In order to reveal the effects of saltwater intrusion on the soil carbon mineralization potential in estuarine wetlands,this study used a fine-scale salinity gradient to determine the impact of saltwater concentration on soil carbon mineralization potential(represented by CO_(2) production)and associated soil properties from the Min River Estuary freshwater wetland,using indoor mud anaerobic incubation with gas chromatography methods for three consecutive weeks.The results showed:(1)Under different salinity treatments,soil pH values were lower than that under the control(0),ammonia nitrogen(NH_(4)^(+)-N)content were higher than that under the control,and increased with increasing salinity.Soluble organic carbon(DOC)contents were higher in 25‰ and 30‰ salinity treatments than that in the control.The contents of SO_(4)^(2-) in 20‰,25‰ and 30‰ treatments were higher than that in the control.(2)With the change of incubated time,the potential of CO_(2) production in the first week of anaerobic incubation was significantly higher than that in the second and third weeks(p<0.05),and the potential of CO_(2) production in different salinity treatments was significantly different,presenting the promoting effect of lower salinity(0.5‰~10‰)and inhibiting effect of higher salinity(15‰~30‰),indicated salinities of 10‰~15‰ represented an important turning point for soil carbon mineralization in wetlands.(3)There was a significant positive correlation between CO_(2) production potential and soil pH under different salinity treatments,and a significant negative correlation between CO_(2) production potential and soil conductivity(EC),NH_(4)^(+)-N,Cl^(-),SO_(4)^(2-) and DOC.Overall,salinity is an important factor affecting soil carbon mineralization in estuarine wetlands.Carbon mineralization may be reduced in higher-level saltwater intrusion,meanwhile,lower-level saltwater intrusion may leave estuarine wetlands vulnerable to submergence due to accelerated soil organic carbon loss.