成土时间对黄河三角洲植物及微生物演替的影响

Driving force of soil age on vegetation and microbial succession in the Yellow River Delta

受时空因素的限制,研究土壤、微生物和植物的演替过程通常采用以空间换时间的时空替代法,关于成土时间的驱动力研究较少。选取黄河三角洲4块代表性冲积区域(形成年代分别为1904—1929年,1929—1934年,1964—1976年和1976年至今),由沿海到农田(1—40 km)设计采样路线,通过多样性调查、土壤采样、MiSeq测序等方法对陆地生态系统的植物、细菌和真菌多样性以及微生物功能组成进行了监测。结果表明,随成土时间的增加,植物物种丰富度和生物量显著提高(P<0.05),低盐度指示物种白茅的分布区域向海岸推进;细菌群落酸杆菌门(Acidobacteriota)等3个门类占比显著增加,拟杆菌门(Bacteroidota)等12个门类占比显著减少(P<0.05),涉及基因信息处理、核苷酸代谢等基础生命活动和光合作用的功能通路在年代最晚的扇区富集,而涉及细胞老化调控、外源物质生物降解与代谢、芳香化合物降解等功能的通路在年代最早的扇区富集(LDA score>2,P<0.05);真菌群落涉及病理营养的捕虫霉门(Zoopagomycota)等类群相对丰度的显著增加(P<0.05)。耐盐菌、自养菌、反硝化菌、反硫化菌等功能群在成土较晚区域的丰富度较高,有促进成土初期土壤碳氮积累、土壤养分循环和有效性的提升的功能潜力,进而影响植物演替。成土时间还驱动适应高营养环境的类群对先锋类群比值的增大,促进微生物生态位的分化。研究表明成土时间是对黄河三角洲植物和微生物群落组成变化的重要而显著的驱动力,为提高评估滨海生态系统植物和微生物演替规律的准确性提供了科学依据。

Due to the limitation of temporal and spatial factors, the succession of soil, microorganism and vegetation is usually studied by a spatial series representing the temporal series which is a kind of space-for-time substitution approaches, while the driving force of soil age is less studied. In this paper, four representative alluvial areas of the Yellow River Delta(the formation periods were 1904—1929, 1929—1934, 1964—1976 and 1976 to the present, respectively) were selected to design sampling routes from coastal areas to farmlands(1—40 km). The diversity of plants, bacteria and fungi, and the functional composition of microorganisms in terrestrial vegetation were studied by bio-diversity surveys, soil sampling, and high-throughput sequencing using the Illumina HiSeq platform. The results showed that with the increase of soil age, plant species richness and aboveground biomass increased significantly(P<0.05), and the distribution area of Imperata cylindrica(L.) Beauv. was advancing to the coast, which is a low-salinity indicator. In bacterial communities, the proportion of 3 phyla such as Acidobacteria, Nitrospirota, and Methylomirabilota increased significantly, while the proportion of other 12 phyla such as Bacteroidota, Gemmatimonadetes, and Patescibacteria decreased significantly(P<0.05). The functional pathway abundance of photosynthesis, and the basic life activities such as nucleotide metabolism and genetic information processing were enriched in the latest sector, while functional pathway abundance of aging, xenobiotics biodegradation and metabolism, and degradation of aromatic compounds were enriched in the earliest sector(LDA score>2, P<0.05). The relative abundance of groups of pathological nutrition increased significantly(P<0.05), such as Zoopagomycota. Soil age accounted for an unique portion to the variations of vegetation, bacterial, and fungal community composition(3.41%、2.61%、1.12%, respectively), which provided additional insights of the vegetation and microbial succession. Salt-tolerant bacteria, autotrophic bacteria, denitrifying bacteria, and desulfurizing bacteria were of higher richness in the later soil forming area, which have the potential to promote soil carbon and nitrogen accumulation, soil nutrient cycling, and soil availability at the early soil forming stage, and then affect plant succession. Soil age also drives the increasing ratio of groups that prefer high nutritional environment over pioneer groups and contributes to the differentiation trend of microbial niche. The study proves that soil age is an important and significant driving force for the change of vegetation and microbial community compositions in the Yellow River Delta and provides a scientific basis for improving the accuracy of assessment of the vegetation and microbial succession in coastal ecosystem.