生态补水对黄河三角洲盐沼地土壤微生物群落分布特征的影响

为探究生态补水对盐沼湿地土壤微生物群落的影响，以黄河三角洲国家级自然保护区内人工围坝、实施“引淡压咸”淡水补给工程的湿地土壤为研究对象，以潮汐区天然盐沼湿地土壤为参照，使用磷脂脂肪酸（PLFA）法对比研究0~30 cm土层中4种土壤微生物群落（细菌、真菌、放线菌和丛枝菌根真菌等）在2类湿地中的分布特征，同时区别不同植被条件下（芦苇群落、盐地碱蓬群落和裸滩）的差异。结果表明:供试土壤的PLFA总量在4.25~32.71nmol.g-1之间，微生物群落组成均以细菌为主，表征4种微生物类群的PLFA含量由高到低依次为细菌(（8.47±4.66) nmol.g-1）、真菌（（1.28±2.21 ）nmol.g-1）、放线菌（（0.98±0.68） nmol.g-1）、丛枝菌根真菌（（0.29±0.27） nmol.g-1）。表征4种微生物类群的PLFA的含量均表现为生态补水区高于天然盐沼区，其中细菌平均高出39.63% ，真菌平均高出63.56% ，放线菌平均高出65.14% ，丛枝菌根真菌平均高出69.22% ，这可能是由补水引起的土壤pH减小、有机碳含量增加而导致的；从3种植被条件的对比来看，土壤PLFA含量由高到低依次为芦苇群落（7.43~32.71 nmol.g-1）、盐地碱蓬群落（4.87~16.58 nmol.g-1）、裸滩（4.25~7.54 nmol.g-1）。6种样地土壤PLFA总量排序为:补水区芦苇群落（17.70~32.71 nmol.g-1）、补水区盐地碱蓬群落（10.71~15.44 nmol.g-1）、潮汐区芦苇群落（7.43~12.23 nmol.g-1）、补水区裸滩（5.93~7.54 nmol.g-1）、潮汐区盐地碱蓬群落（4.87~6.50 nmol.g-1）、潮汐区裸滩（4.25~5.02 nmol.g-1）。补水区芦苇湿地土壤PLFA总量和真菌PLFA相对含量的增幅较大，这与补水区土壤适宜芦苇生长，而芦苇生物量的大量增加又导致土壤有机质的大幅增多和pH的下降密切相关；真菌与其他3类微生物相比，对补水和植被的响应幅度最大，尤其在恢复区芦苇群落土壤中，这进一步证实了土壤真菌在植物枯落物分解、植物碳转化为土壤碳方面的重要作用。从当前PLFA含量增加的角度来看，补水显著提升了芦苇群落土壤中微生物的生物量，然而盐沼湿地土壤微生物生物多样性及盐沼湿地生态过程、生态系统结构和功能在补水后的变化有待进一步系统综合地研究和评估。 

Distribution of soil microbial community in natural salt marshes and restored salt marshes in the Yellow River Delta

Ecological effect of recovery projects on soil microbial community in the Yellow River Delta was investigated in the present work.Soil samplings were taken from natural tidal salt marshes and recovery regions.Phospholipid fatty acid (PLFA)analysis was done to characterize soil microbial communities:bacteria, fungi,arbuscular mycorrhizal fungi and actinomycete in 030 cm soil layer, differences in vegetation conditions (Phragmitesaustralis,Suaedasalsa and bare land)were noted.Total soil PLFA content was found to be 4.2532.71 nmol·g-1 ,dominated by bacteria community.According to PLFA content,abundance of microbial groups was:bacteria ((8.47±4.66)nmol·g-1 )>fungi ((1.28±2.11)nmol·g-1 )>actinomycetes ((0.98±0.68)nmol·g-1 )>arbuscular mycorrhizal fungi ((0.29 ±0.27)nmol·g-1 ).Soil PLFA content in recovery region was higher than in natural tidal region,bacterial PLFA increased by 39.63％,fungi PLFA by 63.56％,actinomycetes PLFA by 65.14％,arbuscular mycorrhizal fungi PLFA by 69.22％.Such changes were likely due to decreased soil pH and increased soil organic carbon in the recovery project,after freshwater pumping-in and subsequent plant especially large biomass plant-reed development.Of the three vegetations, microbial PLFA content was:Phragmites australis (7.4332.71 nmol·g-1 )>Suaeda salsa (4.8716.58 nmol·g-1 )>bare land (4.257.54 nmol·g-1 ).PLFA contents in soil samples were:Phragmites australis in recovery area (17.7032.71 nmol·g-1 )>Suaeda salsa in recovery area (10.7115.44 nmol·g-1 )>Phragmitesaustralis in tidal area (7.4312.23 nmol·g-1 )>bare land in recovery area (5.937.54>nmol· g-1 )>Suaeda salsa in tidal area (4.876.50 nmol·g-1 )>bare land in tidal area (4.255.02 nmol·g-1 ). Total PLFA content and relative abundance of fungi PLFA in Phragmites australis community in recovery region increased more than others due to Phragmites australis growth leading to increased soil organic matter and decreased pH values.Compared with the other three microbial groups,fungi had larger response amplitude to reed development and freshwater pumping in salt marshes.The important role of soil fungi in decomposition of plant litter,and transformation of plant carbon into soil carbon was confirmed.Increased PLFA content in salt marsh soils demonstrated that freshwater supplementation increased significantly the biomass of soil microorganisms in Phragmitesaustralis community,largely attributed to microbial proliferation and reed litter decomposition.Microbial biodiversity, biogeochemical process, ecosystem structure and function of salt marshes after freshwater supplementation need to be further investigated.