沿海区土壤线虫对海水入侵土壤盐渍化的响应

Response of soil nematodes to soil salinization induced by seawater intrusion in coastal areas

摘要:

在2013年对大连市大魏家镇海水入侵污染区域进行了土壤理化性质和线虫群落调查，在此基础上，应用线虫多样性指数和功能类群指数研究海水入侵土壤盐渍化以及不同土地利用方式对土壤线虫群落结构的影响。研究期间共鉴定出土壤线虫30科48个属。其中食细菌类群的比例最高，共17属，占总数42.81%；其次为杂食/捕食类群，共9个属，占总数25.26%。优势属为Plectus。结果显示：海水入侵已造成该地区土壤盐渍化；土壤盐分与线虫生态指数SR、f/b、NCR、PPI、MI、PPI/MI、PP%、FF%、BF%和OP%存在显著的相关关系；土地利用方式、土壤盐分对线虫群落的生态指数影响显著，是影响该地区土壤线虫群落结构的主要因素。通过开展土壤线虫对海水入侵土壤盐渍化响应的研究，为促进沿海受海水污染区土壤生态系统的健康发展提供科学依据。

Abstract:

In 2013, soil samples were collected in Daweijia Town of Dalian City where seawater intrusion once occurred, for analysis of soil physical and chemical properties, including soil salinity, moisture content, Na⁺ content, K⁺ content, organic matter content, nitrate content, available P and pHand for counting of soil nematodes, using the ISC process. The nematodes separated from the soil were classified and identified. Then impacts of seawater contamination and land use on soil nematodes community structure were studied using the diversity index and functional group indices. Results show that long-term irrigation with sea water polluted groundwater has caused the background soil salinity value of the region doubled or tripled, with Na⁺ content increasing, K⁺ content decreasing and the soil significantly salinized. The closer to the coast, the higher the degree of soil salinization was.Organic matter content decreased with the increasing salinity. The total of 13 308.4nematodes identified belonged to 48 genera of 30 families, including 17 genera of bacterivores nematodes and 9 genera of omnivore-predator, representing 42.81% and 25.26%, respectively, of the total. Plectus was the dominant genera, representing 13.47% of the total. Among the life history strategies of soil nematodes, c-p1~2 was the largest in proportion, and the proportion of c-p1~2 was higher in soils high in salinity than in soils low in salinity under the same land use, and higher in farmland than in soils under other forms of land use. With rising soil salinity, NCR, PPI and PPI/MI of soil nematodes and proportions of plant-parasitic nematodes, bacteria-feeding nematodes and omnivores/predatory nematodes all increased, but Shannon-Wiener, f/b, MI, and proportion of bacterivores reduced. The relationship between nematode community and soil moisture content was also quite significant. The impacts of type of land use were very significant on number and diversity of soil nematode groups (S) and extremely significant on population and PPI of soil nematodes. Among the different types of land use, orchards received large volumes of organic manure and chemical fertilizer, thus altering their soil properties and raising their soil fertility and organic matter content as well. In such soils, the higher the organic matter content, the great the population of soil nematodes, the less the number of parasite nematodes, the more favorable the soil to crop growth, and the higher the density of nematode individuals in the soil. In croplands, often short in cultivation history, but frequently disturbed by tillage, the habitat for nematodes varied sharply, thus making the density of soil nematodes lower. The findings demonstrate that soil nematode community responds to sea water contamination variably, depending on degree of the contamination. Therefore, its response can be used to indicate status of the soil environment and sea water pollution degree of the region. Beside, the impacts of land use on soil nematode communities relative to type of the land use. In orchard, soil nematodes are quite high in individual density, number of groups and diversity because orchards offer soil nematodes a better habitat than croplands do. The findings of the study provide a theoretical basis for future study on how soil nematode community respond to seawater pollution and how the soils in sea water polluted areas can be remedied.