Effect of land use on soil nematode community composition and co-occurrence network relationship

Land use influences soil biota community composition and diversity,and then belowground ecosystem processes and functions.To characterize the effect of land use on soil biota,soil nematode communities in crop land,forest land and fallow land were investigated in six regions of northern China.Generic richness,diversity,abundance and biomass of soil nematodes was the lowest in crop land.The richness and diversity of soil nematodes were 28.8and 15.1%higher in fallow land than in crop land,respectively.No significant differences in soil nematode indices were found between forest land and fallow land,but their network keystone genera composition was different.Among the keystone genera,50%of forest land genera were omnivores-predators and 36%of fallow land genera were bacterivores.The proportion of fungivores in forest land was 20.8%lower than in fallow land.The network complexity and the stability were lower in crop land than forest land and fallow land.Soil pH,NH_(4)^(+)-N and NO_(3)^(–)-N were the major factors influencing the soil nematode community in crop land while soil organic carbon and moisture were the major factors in forest land.Soil nematode communities in crop land influenced by artificial management practices were more dependent on the soil environment than communities in forest land and fallow land.Land use induced soil environment variation and altered network relationships by influencing trophic group proportions among keystone nematode genera.

我国土壤线虫生态学研究进展和展望

土壤线虫生态学主要探讨土壤线虫群落和其周围环境(包括生物和非生物)的相互关系,包括不同生态系统中土壤线虫群落的分布和结构组成、线虫群落与土壤环境及其他土壤生物之间的相互作用等。本文回顾了我国研究者近年来在土壤线虫生态学研究领域的研究现状,包括不同生态系统土壤线虫群落的分布、组成和多样性及其影响因素,土壤线虫群落与全球气候环境变化的关系,土壤线虫群落的生态功能以及土壤线虫群落生态学分析方法的发展及应用。重点评述近年来我国土壤线虫生态学的发展现状,同时分析和比较了国内外土壤线虫生态学的发展态势,提出建设全国范围的监测网络的重要性。未来我国土壤线虫生态学的发展方向应继续加强小尺度下土壤微食物网联通性和大尺度下全球气候变化对土壤线虫群落影响的研究以及加强相关新的研究技术方法的应用。

下辽河平原农田土壤线虫群落组成的季节变化

下辽河平原农田生态系统在管理过程中频繁的耕作、施肥以及农用化学品施用等引发了一系列问题,如土壤退化、耕地数量减少以及生产力下降等,不可避免地对土壤生物健康产生影响。为探究农田土壤人工管理对土壤生物群落动态的影响,本研究在辽宁沈阳农田生态系统国家野外科学观测研究站开展了农田土壤线虫群落组成的季节变化研究,对4个季节农田和废弃农田(对照)的土壤线虫群落组成、多度以及多样性等进行了比较分析。研究结果表明,土壤线虫总多度在废弃农田中显著高于农田,但季节间差异不显著。季节变化主要显著影响了自由生活线虫的多度,其在9月达到最高;季节变化也显著影响了属的数量,其在非生长季的11月最低。与废弃农田相比,农田管理显著降低了杂食捕食线虫和食真菌线虫的多度,土壤食物网结构相对稳定;而废弃的农田更易受到季节波动的影响,土壤食物网也受到一定的干扰。

Organic amendment effects on nematode distribution within aggregate fractions in agricultural soils

To evaluate the effect of organic amendments on soil nematode community composition and diversity within aggregate fractions,a study was initiated in agricultural soils with four-year organic amendments.Soil samples were collected from the plow layer(0-20 cm)under three cornfield management scenarios:1)conventional cropping(CK,corn straw removal and no organic manure application);2)straw retention(SR,incorporation of chopped corn stalk);and 3)manure application(MA,chicken manure input).The soil samples were fractionated into four aggregate sizes,i.e.,>2 mm(large macroaggregates),1-2 mm(macroaggregates),0.25-1 mm(small macroaggregates),and<0.25 mm(microaggregates,silt and clay fractions).The composition and diversity of soil nematode communities were determined within each aggregate fraction.The results showed that both SR and MA treatments significantly increased the percentage of macroaggregates(>1 mm)and only MA treatment strongly increased the mean weight diameter compared to the CK(P<0.05).The abundance of total nematodes and four trophic groups were affected significantly by the aggregate fractions and their higher abundance occurred in the larger aggregates.The effects of aggregate size on most nematode genera were significant.Bacterivores in the small macroaggregates and microaggregates,and fungivores in the large macroaggregates were significantly different among treatments.The percentage of bacterivores increased after the application of organic materials,while that of fungivores decreased.It can be concluded that organic management significantly affects soil aggregation and soil characteristics within aggregates,and the aggregate size subsequently influences the distribution of nematode communities.

Effects of vegetation coverage on the spatial distribution of soil nematode trophic groups

The spatial variability of total soil nematodes and trophic groups in bare and fallow plots in Shenyang Experi-mental Station of Ecology,ChineseAcademy of Sciences was examined using geostatistics combined with classic statistics.Results showed that the soil pH value had a negative effect on plant-parasites in both bare and fallow plots;the mean number of total nematodes was significantly higher in fallow plots than in bare plots,which was 1485.3 and 464.0 individuals per 100 g dry soil in fallow and bare plots,respectively;the nugget(C_(0))/sill(C_(0)+C)ratio of total nematodes,plant-parasites and bacterivores were lower in fallow plots(27.3%-45.6%)than in bare plots(49.5%-100%);the spatial distribution of total nematodes and trophic groups was found to be different between fallow and bare plots,which indicated that vegetation coverage had an effect on soil nematodes.

Responses of nematode communities to different land uses in an aquic brown soil

An analysis of the seasonal and vertical distribution of soil nematode communities under three contrasting land uses,i.e.,cropland,abandoned cropland and woodland was conducted in an aquic brown soil.The results showed that different land-use types affected the spatiotemporal distribution of soil nematodes and their dominant genera,and different dominant genera showed different responses to land use.In the abandoned cropland and woodland,most dominant genera were present in the 0–20 cm layers and Chiloplacus was mainly distributed in the 5–30 cm layers,while in the cropland,Pratylenchus exhibited an even distribution from the 0–5 cm to the 40–50 cm depth.Soil environmental parameters under different land use could influence soil nematodes;soil porosity,total organic C,total N and the C/N ratio could positively influence the abundance of some dominant genera.Faunal profiles revealed that environmental stability and the homeostasis in the abandoned cropland and woodland lead to higher levels of community structure,and the soil food web tends to succeed to maturity.Nematode faunal analyses are a useful indicator for interpreting the stress and/or nutrient conditions under different land uses.