A field investigation was conducted at the Shenyang Experimental Station of Ecology, Chinese Academy of Sciences, in an aquic brown soil of Northeast China under three land use types (cropland, abandoned cropland, and...A field investigation was conducted at the Shenyang Experimental Station of Ecology, Chinese Academy of Sciences, in an aquic brown soil of Northeast China under three land use types (cropland, abandoned cropland, and woodland) in order to evaluate whether the vertical distribution and seasonal fluctuation for the number of total nematodes and trophic groups could reflect soil ecosystem differences and to determine the relationships between soil chemical properties and soil nematodes. The majority of soil nematodes were present in the 0-20 cm soil layers, and for these land use types plant parasites were the most abundant trophic group. In the abandoned cropland the numbers of plant parasites reached a peak on the August sampling date, whereas the cropland and woodland peaked on the October sampling date. Meanwhile, in all land use types the number of total nematodes, bacterivores, plant parasites, and omnivores-predators was negatively (P < 0.05, except for bacterivores in cropland, which was not significant) correlated with bulk density, and positively (P < 0.05, except for fungivores in abandoned cropland, which was not significant) correlated with total organic carbon and total nitrogen.展开更多
Geostatistics combined with GIS was applied to assess the spatial distribution of nematode trophic groups following two contrasting soil uses in the black soil region of Northeast China. Two plots, one with fallow for...Geostatistics combined with GIS was applied to assess the spatial distribution of nematode trophic groups following two contrasting soil uses in the black soil region of Northeast China. Two plots, one with fallow for 12 years and the other cultivated, were marked on regular square grids with 2-m spacing. Soil samples were collected from each sampling point, nematodes were extracted from these samples and classified into four trophic groups: bacterivores, fungivores, plant parasites, and omnivores/predators. The numbers of total nematodes and trophic groups analyzed had normal distributions on both fallow and cultivated plots. The absolute abundances of total nematodes and trophic groups were observed to be much more homogeneous on cultivated plot than on fallow one. Geostatistical analysis showed that the densities of total nematodes and trophic groups on both fallow and cultivated plots exhibited spatial dependence at the sampled scale and their experimental semivariograms were adjusted to a spherical or exponential model, except those of bacterivores and fungivores on cultivated plot. The spatial distribution of nematode trophic groups was found to be different for the two land uses, indicating that cultivation changed the native condition for soil nematode activities.展开更多
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 classi...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.展开更多
While studies have focused on the use of biochar as soil amendment, little attention has been paid to its effect on soil fauna. The biochar was produced from slow pyrolysis of wheat straw in the present study. Four tr...While studies have focused on the use of biochar as soil amendment, little attention has been paid to its effect on soil fauna. The biochar was produced from slow pyrolysis of wheat straw in the present study. Four treatments, no addition (CK) and three rates of biochar addition at 2 400 (B1), 12 000 (B5) and 48 000 kg ha-1 (B20), were investigated to assess the effect of biochar addition to soil on nematode abundance and diversity in a microcosm trial in China. The B5 and B20 application significantly increased the total organic carbon and the C/N ratio. No significant difference in total nematode abundance was found among the treatments. The biochar addition to the soil significantly increased the abundance of fungivores, and decreased that of plant parasites. The diversity of soil nematodes was significantly increased by B1 compared to CK. Nematode trophic groups were more effectively indicative to biochar addition than total abundance.展开更多
The influence of Cu and Zn on soil nematode communities was examined along a pollution gradient with increasing distance from a metallurgical factory. Total and available heavy metal contents were used to study the ef...The influence of Cu and Zn on soil nematode communities was examined along a pollution gradient with increasing distance from a metallurgical factory. Total and available heavy metal contents were used to study the effects of heavy metals on nematode abundance, trophic groups and ecological indices. The results demonstrated significant correlations between the number of total nematodes, bacterivores, plant-parasites and the total and available heavy metals. Bacterivores and plant-parasites were the dominant trophic groups. Significant differences in different sampling sites were found only in the number of bacterivores（P〈0.01）. The Shannon-Weaver diversity index（W）, trophic diversity index（TD）, evenness index（J＇） and dominance index（λ） were found to be sensitive to soil pH and C/N ratios. Significant correlations were found between the total nematodes （TNEM）, some genera （A crobeloides, Aphelenchoides, Cephalobus, Ditylenchus, Mesorhabditis, Tetylenchus and Tylenchus） and distance from the factory.展开更多
Soil microorganism biomass and respiration and the soil nematode community were observed in the hypersaline desert valley that is found between the Dead Sea and the Red Sea. The lowest point of the valley is approxima...Soil microorganism biomass and respiration and the soil nematode community were observed in the hypersaline desert valley that is found between the Dead Sea and the Red Sea. The lowest point of the valley is approximately 400 m below sea level, and is the lowest point on earth. Soil samples (n = 72) were collected from the 0-10 and 10-20 cm soil layers at different altitudes (from -400 to +100 m) in the open spaces between plants during one of the most extreme xeric periods. Both soil microbial respiration and microbial biomass were found to be negatively dependent on soil moisture (SM) and organic matter (OM), and positively dependent on pH values. The physical-chemical characteristics of this hypersaline area were extremely unfavorable for the soil nematode communities, and the nematodes were entirely absent in the open area below sea level. The bacterivores were found to be the most resistant nematodes in this hyperarid region, with the Wilsonema being the most widespread genus. We suggest that nitrogen availability may play a crucial role in the below-ground soil interaction in this region, with bacterivore nematodes as indicators of nitrogen availability.展开更多
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,for...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.展开更多
A field experiment was carried out from 2003 to 2013 in the Wanzhong Farm of the Hainan Island, China, to determine the effects of two long-term banana rotations on the abundance and trophic groups of soil nematode co...A field experiment was carried out from 2003 to 2013 in the Wanzhong Farm of the Hainan Island, China, to determine the effects of two long-term banana rotations on the abundance and trophic groups of soil nematode communities in the island. The experiment was set out as a randomized complete block design with three replications of three treatments： banana-pineapple rotation （AB）, banana-papaya rotation （BB） and banana monoculture （CK） in a conventional tillage system. Soil samples were taken at depths of 0-10, 10-20 and 20-30 cm, and nematodes were extracted by a modified cotton-wool filter method and identified to the genus level. Nematode ecological indices of Shannon-Weaver diversity （Ht）, dominance index （A）, maturity index （MI）, plant parasite index （PPI）, structure index （SI）, enrichment index （EI）, and channel index （CI） were calculated. A total of 28 nematode genera with relative abundance over 0.1% were identified, among which Tylenchus and Paratylenchus in the AB, Thonus in the BB, Tylenchus and Helicotylenchus in the CK were the dominant genera. The rotation soils favored bacterivores, fungivores and omnivores-predators with high colonizer-persister （c-p） values. Soil food web in the rotation systems was highly structured, mature and enriched as indicated by SI, MI and EI values, respectively. Higher abundance of bacterivores and lower values of CI suggested that the soil food web was dominated by a bacterial decomposition pathway in rotation soils. Nematode diversity was much higher after a decade of rotation. Soil depth had significant effects on the abundance of soil nematodes, but only on two nematode ecological indices （λ and MI）.展开更多
It has been well documented that organic amendment affects soil nematode community structure.However,little is known about the effect of organic amendment amount on soil nematodes.To assess the effect of the amount of...It has been well documented that organic amendment affects soil nematode community structure.However,little is known about the effect of organic amendment amount on soil nematodes.To assess the effect of the amount of organic amendments on soil nematode community structure and metabolic activity,the community composition,abundance,and metabolic footprints of soil nematodes were determined in a long-term field experiment with various amounts of organic amendment in Northeast China.Fertilization treatments included an unfertilized control(CK),chemical fertilizer without manure amendment(OM0),manure applied at 7.5 Mg ha^-1 plus chemical fertilizer(OM1),and manure applied at 22.5 Mg ha^-1 plus chemical fertilizer(OM2).A total of 46 nematode genera were found.Treatments with the largest amount of organic amendment had the smallest number of plant parasite genera(5),but a largest number of dominant genera(7).Soil nematodes,bacterivores,and fungivores were the most abundant in OM2,followed by OM1,and the lowest in OM0 and CK.Organic amendment increased the enrichment index(EI),and the large amount of organic amendment increased the metabolic footprints of bacterivore(Baf)and fungivore(Fuf)and enrichment footprint(Ef).The relationships between Baf(or Fuf)and the increases in soil organic carbon(?SOC)and total nitrogen(?TN)were stronger than those of bacterivore(or fungivore)abundance with?SOC and?TN,except for the relationship between bacterivore abundance and ?SOC.The EI and Ef were positively correlated with ?SOC and ?TN.These findings suggest that the amount of organic amendment affects soil nematode activity and function at entry levels in soil food web,and that metabolic footprints of soil nematodes may be better indicators than their abundances in assessing their relationships with soil nutrients.展开更多
At a rice wheat rotational free air CO 2 enrichment(FACE) platform, the effect of elevated atmospheric CO 2 on soil nematode communities in a farmland ecosystem was studied. Wheat plots were exposed to elevated atmosp...At a rice wheat rotational free air CO 2 enrichment(FACE) platform, the effect of elevated atmospheric CO 2 on soil nematode communities in a farmland ecosystem was studied. Wheat plots were exposed to elevated atmospheric CO 2(ambient 370 μl/L + 200 μl/L). 32 families and 40 genera of nematode were observed in soil suspensions during the study period. Under FACE treatment, the numbers of total nematodes, bacterivores and fungivores exhibited an increasing trend. Because of the seasonal variation of soil temperature and moisture, the effect of elevated atmospheric CO 2 on soil nematodes was only observed under favorable conditions. The response of nematode communities to elevated atmospheric CO 2 may indicate the change of soil food web.展开更多
Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity.However,the extent to which...Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity.However,the extent to which unique geomorphic formations influence soil biotic seasonal variation is not clear.Our aim was to define seasonal variations of soil biota in soils of different-aged terraces of the Makhtesh Ramon anticline erosional cirque in southern Israel.The strong effect of Makhtesh Ramon (Ramon crater) erosional fluvial terrace age initiated by climatic changes during the Late Pleistocene- Early Holocene period on seasonal variations in both soil properties and the abundance and composition of soil biota were demonstrated.However,age dependence was not constant and values for observed soil properties and microbial activity were negligible between younger and older terraces for certain seasons,while free-living nematodes along with bacterial-feeding group were strongly dependent on the geomorphic features of the ages throughout the study period.展开更多
Soil biota play a crucial role in soil ecosystem stability, promoting organic matter decomposition and nutrient cycling. Compared to conventional farming,organic farming is known to improve soil properties such as agg...Soil biota play a crucial role in soil ecosystem stability, promoting organic matter decomposition and nutrient cycling. Compared to conventional farming,organic farming is known to improve soil properties such as aggregation. Despite the importance of soil microbial communities in soil biogeochemical processes, our knowledge of their dynamics is rudimentary, especially under different agricultural management practices. Here we studied the effects of vineyard management practices(conventional and organic) and soil aggregate fractions(micro-, meso-, and macroaggregates) on free-living soil nematodes.The abundance, diversity, and ecological indices, such as the Wasilewska index and trophic diversity, of free-living soil nematodes were determined. We found that the abundance of free-living soil nematodes was increased by organic farming. In addition, plant parasites were found to increase in macroaggregates in the organic plot, which may be attributed to the weeds present due to no-tillage and no herbicides. Nematode family network connectivity increased in complexity with increasing aggregate size, highlighting the importance of the interplay between nematodes and soil inter-aggregate pore size and connectivity.展开更多
Background: Gradients in local environmental characteristics may favour the abundance of species with particular traits, while other species decline, or favour species with different traits at the same time, without a...Background: Gradients in local environmental characteristics may favour the abundance of species with particular traits, while other species decline, or favour species with different traits at the same time, without an increase in average species abundances. Therefore, we asked: do variations in species and traits differ along gradients of deadwood variables? Do species abundance and trait occurrence change with species richness within or between functional groups? Thus, we analysed the beetle assemblages of five forest sites located in Italy, along the Apennines mountains.Methods: From 2012 to 2018 we sampled beetles and five deadwood types in 193 plots to characterise the deadwood gradient: standing dead trees, snags, dead downed trees, coarse woody debris, and stumps. We modelled beetle species relative abundances and trophic traits occurrences against the deadwood variables using joint species distribution models.Results: Out of 462 species, only 77 showed significant responses to at least one deadwood type, with a weak mean response across species. Trophic groups showed mostly negative responses to deadwood variables. Species abundance increased with species richness among sites only for phytophagous and saproxylophagous. Trait occurrence did not increase with species richness among sites, except for phytophagous and saproxylophagous.However, trait occurrence changed significantly with species richness of several trophic groups within some sites.We found that increases in species richness do not result in decreases in species abundance of a given trophic group, but rather null or positive relationships were found suggesting low interspecific competition.Conclusions: Our findings suggest that in Mediterranean mountain forests there is still room for increasing the level of naturalness, at least for what concerns deadwood management. On one side, our findings suggest that competition for deadwood substrates is still low, on the other side they indicate that increasing deadwood volume and types to improve overall beetle richness may increase also beetle abundances.展开更多
Functional structure and diversity of soil free-living nematodes in a desert environment depend on plant gender and sampling site.The objective of this study was to compare the composition,abundance and tropic group o...Functional structure and diversity of soil free-living nematodes in a desert environment depend on plant gender and sampling site.The objective of this study was to compare the composition,abundance and tropic group of soil free-living nematodes in the upper 0–10 cm soil layer under the male and female Acanthosicyos horridus Welw.ex Hook.f.plants and in the inter-shrub open areas(control)in the Namib Desert,Namibia in April 2015.Soil moisture,organic matter(OM)and pH was also analyzed.Free-living nematodes were extracted from 100 g soil using the Baermann funnel procedure,and total number of nematodes was counted under a microscope.Community composition and diversity of soil free-living nematodes were analyzed using 18S rDNA sequences.Results indicated that a total of 67 groups,including 64 species,2 genera and 1 family were identified.Feeding behavior of 58 species were identified as follows:15 bacteria-feeding species,12 fungi-feeding species,10 plant-parasite species,5 omnivorous-predator species,8 animal-parasite species,5 invertebrate-parasite species and 3 non-free-living nematodes,known as marine species.Moreover,soil free-living nematodes were found to be affected by sampling locations and plant gender,and community composition and density of these nematodes were strongly influenced by soil OM content.Result confirmed that spatial location and plant cover were main factors influencing the diversity of soil free-living nematodes.Moreover,molecular tools were found to be very useful in defining the richness of soil non-free-living nematodes.In conclusion,the results elucidated the importance of biotic variables in determining the composition and abundance of soil free-living nematodes in the Namib Desert,Namibia.展开更多
The alpine wetlands in the Qinghai-Tibetan Plateau have degraded in recent decades.However,the response of the soil food web to the degradation is still unclear.Four habitats including a wet meadow(WM),a grassland mea...The alpine wetlands in the Qinghai-Tibetan Plateau have degraded in recent decades.However,the response of the soil food web to the degradation is still unclear.Four habitats including a wet meadow(WM),a grassland meadow(GM),a moderately degraded meadow(MDM)and a severely degraded meadow(SDM)(sandy meadows)were selected along the degrees of degradation.The soil macrofaunal biomass and the environmental factors of vegetation and soil were investigated.The soil macrofaunal community biomass increased significantly from WMto MDM and decreasedto a very small amount in SDM,with most taxa disappearing.The biomass of the trophic groups of detritivores,herbivores and predators exhibited similar responses to soil macrofaunal communities.The relative biomass of detritivores increased from WM to MDM,but herbivores responded in an opposite manner,resulting in the dominant trophic group and trophic structure varying progressively from WM to GM to MDM.Soil properties but not vegetation determined the changes in trophic groups and trophic structure.The results implied that the higher trophic levels(carnivores or omnivores)responded more sensitively than the lower trophic levels(herbivores)to alpine wetland degradation.Our results also suggested that soil macrofauna have a habitat-specific characteristic trophic structure and can be used as indicators of soil health conditions.展开更多
The relative abundance of different components of the soil food web can vary tremendously in response to plant resource inputs.However,little is known about the mechanisms that plant resource regulates the energy flux...The relative abundance of different components of the soil food web can vary tremendously in response to plant resource inputs.However,little is known about the mechanisms that plant resource regulates the energy fluxes and soil community composition.Here,we experimentally reduced litter and root inputs for two years in China at low-,mid-,and high-latitude forests to explore the effects of plant-derived resource inputs on the nematode energy flux and community composition.Litter reduction at high and mid latitudes and root removal at low latitudes reduced nematode richness but did not alter nematode abundance.Besides,litter reduction reduced energy fluxes of bacterial-feeding nematodes at mid latitudes and energy fluxes of plant-feeding,bacterial-feeding and omnivorous-predatory nematodes at low latitudes,thus reducing the energy fluxes of total nematodes in mid-and low-latitude forests.By contrast,root removal reduced energy fluxes and relative energy flux of plant-feeding nematodes in high-and low-latitude forests.In most cases,nematode diversity in different trophic groups increased with increasing energy flux to nematodes.Taken together,our results suggest that the effects of plant resource inputs on nematode energy flux are affected by climate and plant resource type,which improves our understanding of plant-soil interactions.展开更多
Aims Plant invasions have the potential to affect the community structure of soil nematodes,but little is known about whether such effects are mediated by aboveground herbivores since invasive plants are not completel...Aims Plant invasions have the potential to affect the community structure of soil nematodes,but little is known about whether such effects are mediated by aboveground herbivores since invasive plants are not completely released from herbivores in the introduced range.In this study,we explored how aboveground insect herbivores mediated the effect of invasive plant Alternanthera philoxeroides on soil nematodes and examined the temporal variations of such an herbivory-elicited effect.Methods We conducted a greenhouse experiment by applying different herbivory treatments(no insect herbivores,specialist Agasicles hygrophila and generalist Cassida piperata)to potted A.philoxeroides,and then measured the community compositions of soil nematodes in corresponding pots on the 1st,10th and 20th day after removal of all herbivores.In addition,the carbon content of roots and root exudate of A.philoxeroides were also measured.Important Findings Our results showed that aboveground herbivory significantly increased the abundance of soil nematodes of A.philoxeroides,likely plant feeder nematodes,after insect herbivores were removed immediately(1st day).However,such impacts waned with time and there was no significant difference at later stages(10th and 20th days).Furthermore,the effects of specialist A.hygrophila and generalist C.piperata herbivory were consistent on the abundance of soil nematodes.Overall,our results suggest that aboveground insect herbivores have the potential to alter the effects of plant invasions on soil nematodes,but such impacts are transient.Furthermore,our study highlighted the importance of integrating the effects of above-and belowground organisms when evaluating the impacts of plant invasions.展开更多
Soil nematodes are the most numerous components of the soil fauna in terrestrial ecosystems.The occurrence and abundance of nematode trophic groups determine the structure and function of soil food webs.However,little...Soil nematodes are the most numerous components of the soil fauna in terrestrial ecosystems.The occurrence and abundance of nematode trophic groups determine the structure and function of soil food webs.However,little is known about how nitrogen deposition and land-use practice(e.g.mowing)affect soil nematode communities.We investigated the main and interactive effects of nitrogen addition and mowing on soil nematode diversity and biomass carbon in nematode trophic groups in a temperate steppe in northern China.Nitrogen addition and mowing significantly decreased the abundance of soil nematodes and trophic diversity but had no effects on nematode richness and the Shannon-Wiener diversity.Nitrogen addition influenced soil nematode communities through decreasing soil pH.Mowing influenced soil nematode communities through decreasing soil moisture.Nitrogen addition enhanced the bacterial energy channel but mowing promoted fungal energy channel in the soil micro-food web.Our study emphasizes that ecosystem function supported by soil organisms can be greatly influenced by nitrogen deposition,and mowing cannot mitigate the negative effects of nitrogen deposition on soil food webs.展开更多
基金Supported by the National Natural Science Foundation of China (No. 30570337).
文摘A field investigation was conducted at the Shenyang Experimental Station of Ecology, Chinese Academy of Sciences, in an aquic brown soil of Northeast China under three land use types (cropland, abandoned cropland, and woodland) in order to evaluate whether the vertical distribution and seasonal fluctuation for the number of total nematodes and trophic groups could reflect soil ecosystem differences and to determine the relationships between soil chemical properties and soil nematodes. The majority of soil nematodes were present in the 0-20 cm soil layers, and for these land use types plant parasites were the most abundant trophic group. In the abandoned cropland the numbers of plant parasites reached a peak on the August sampling date, whereas the cropland and woodland peaked on the October sampling date. Meanwhile, in all land use types the number of total nematodes, bacterivores, plant parasites, and omnivores-predators was negatively (P < 0.05, except for bacterivores in cropland, which was not significant) correlated with bulk density, and positively (P < 0.05, except for fungivores in abandoned cropland, which was not significant) correlated with total organic carbon and total nitrogen.
基金Project supported by the National Key Basic Research Support Foundation (NKBRSF) of China (No. G1999011804-04) the Foundation of Knowledge Innovation Program of IAE-CAS (No. SCXMS0105).
文摘Geostatistics combined with GIS was applied to assess the spatial distribution of nematode trophic groups following two contrasting soil uses in the black soil region of Northeast China. Two plots, one with fallow for 12 years and the other cultivated, were marked on regular square grids with 2-m spacing. Soil samples were collected from each sampling point, nematodes were extracted from these samples and classified into four trophic groups: bacterivores, fungivores, plant parasites, and omnivores/predators. The numbers of total nematodes and trophic groups analyzed had normal distributions on both fallow and cultivated plots. The absolute abundances of total nematodes and trophic groups were observed to be much more homogeneous on cultivated plot than on fallow one. Geostatistical analysis showed that the densities of total nematodes and trophic groups on both fallow and cultivated plots exhibited spatial dependence at the sampled scale and their experimental semivariograms were adjusted to a spherical or exponential model, except those of bacterivores and fungivores on cultivated plot. The spatial distribution of nematode trophic groups was found to be different for the two land uses, indicating that cultivation changed the native condition for soil nematode activities.
文摘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.
基金Supported by the National Basic Research Program (973 Program) of China (No. 2011CB100504)the Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-Q1-07)the Bluemoon Foundation, USA
文摘While studies have focused on the use of biochar as soil amendment, little attention has been paid to its effect on soil fauna. The biochar was produced from slow pyrolysis of wheat straw in the present study. Four treatments, no addition (CK) and three rates of biochar addition at 2 400 (B1), 12 000 (B5) and 48 000 kg ha-1 (B20), were investigated to assess the effect of biochar addition to soil on nematode abundance and diversity in a microcosm trial in China. The B5 and B20 application significantly increased the total organic carbon and the C/N ratio. No significant difference in total nematode abundance was found among the treatments. The biochar addition to the soil significantly increased the abundance of fungivores, and decreased that of plant parasites. The diversity of soil nematodes was significantly increased by B1 compared to CK. Nematode trophic groups were more effectively indicative to biochar addition than total abundance.
文摘The influence of Cu and Zn on soil nematode communities was examined along a pollution gradient with increasing distance from a metallurgical factory. Total and available heavy metal contents were used to study the effects of heavy metals on nematode abundance, trophic groups and ecological indices. The results demonstrated significant correlations between the number of total nematodes, bacterivores, plant-parasites and the total and available heavy metals. Bacterivores and plant-parasites were the dominant trophic groups. Significant differences in different sampling sites were found only in the number of bacterivores（P〈0.01）. The Shannon-Weaver diversity index（W）, trophic diversity index（TD）, evenness index（J＇） and dominance index（λ） were found to be sensitive to soil pH and C/N ratios. Significant correlations were found between the total nematodes （TNEM）, some genera （A crobeloides, Aphelenchoides, Cephalobus, Ditylenchus, Mesorhabditis, Tetylenchus and Tylenchus） and distance from the factory.
文摘Soil microorganism biomass and respiration and the soil nematode community were observed in the hypersaline desert valley that is found between the Dead Sea and the Red Sea. The lowest point of the valley is approximately 400 m below sea level, and is the lowest point on earth. Soil samples (n = 72) were collected from the 0-10 and 10-20 cm soil layers at different altitudes (from -400 to +100 m) in the open spaces between plants during one of the most extreme xeric periods. Both soil microbial respiration and microbial biomass were found to be negatively dependent on soil moisture (SM) and organic matter (OM), and positively dependent on pH values. The physical-chemical characteristics of this hypersaline area were extremely unfavorable for the soil nematode communities, and the nematodes were entirely absent in the open area below sea level. The bacterivores were found to be the most resistant nematodes in this hyperarid region, with the Wilsonema being the most widespread genus. We suggest that nitrogen availability may play a crucial role in the below-ground soil interaction in this region, with bacterivore nematodes as indicators of nitrogen availability.
基金supported by the National Natural Science Foundation of China(U22A20501)the National Key Research and Development Plan of China(2022YFD1500601)+4 种基金the National Science and Technology Fundamental Resources Investigation Program of China(2018FY100304)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA28090200)the Liaoning Province Applied Basic Research Plan Program,China(2022JH2/101300184)the Shenyang Science and Technology Plan Program,China(21-109-305)the Liaoning Outstanding Innovation Team,China(XLYC2008015)。
文摘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.
基金supported by the National Natural Science Foundation of China (No. 41301277)the Natural Science Foundation of Hainan Province, China (No. 310073)
文摘A field experiment was carried out from 2003 to 2013 in the Wanzhong Farm of the Hainan Island, China, to determine the effects of two long-term banana rotations on the abundance and trophic groups of soil nematode communities in the island. The experiment was set out as a randomized complete block design with three replications of three treatments： banana-pineapple rotation （AB）, banana-papaya rotation （BB） and banana monoculture （CK） in a conventional tillage system. Soil samples were taken at depths of 0-10, 10-20 and 20-30 cm, and nematodes were extracted by a modified cotton-wool filter method and identified to the genus level. Nematode ecological indices of Shannon-Weaver diversity （Ht）, dominance index （A）, maturity index （MI）, plant parasite index （PPI）, structure index （SI）, enrichment index （EI）, and channel index （CI） were calculated. A total of 28 nematode genera with relative abundance over 0.1% were identified, among which Tylenchus and Paratylenchus in the AB, Thonus in the BB, Tylenchus and Helicotylenchus in the CK were the dominant genera. The rotation soils favored bacterivores, fungivores and omnivores-predators with high colonizer-persister （c-p） values. Soil food web in the rotation systems was highly structured, mature and enriched as indicated by SI, MI and EI values, respectively. Higher abundance of bacterivores and lower values of CI suggested that the soil food web was dominated by a bacterial decomposition pathway in rotation soils. Nematode diversity was much higher after a decade of rotation. Soil depth had significant effects on the abundance of soil nematodes, but only on two nematode ecological indices （λ and MI）.
基金supported by the National Key Research and Development Program of China (No.2016YFD02003096)National Natural Science Foundation of China (Nos.41371296 and 41571219)Young Scientist Group of Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences (No.DLSXZ1605)
文摘It has been well documented that organic amendment affects soil nematode community structure.However,little is known about the effect of organic amendment amount on soil nematodes.To assess the effect of the amount of organic amendments on soil nematode community structure and metabolic activity,the community composition,abundance,and metabolic footprints of soil nematodes were determined in a long-term field experiment with various amounts of organic amendment in Northeast China.Fertilization treatments included an unfertilized control(CK),chemical fertilizer without manure amendment(OM0),manure applied at 7.5 Mg ha^-1 plus chemical fertilizer(OM1),and manure applied at 22.5 Mg ha^-1 plus chemical fertilizer(OM2).A total of 46 nematode genera were found.Treatments with the largest amount of organic amendment had the smallest number of plant parasite genera(5),but a largest number of dominant genera(7).Soil nematodes,bacterivores,and fungivores were the most abundant in OM2,followed by OM1,and the lowest in OM0 and CK.Organic amendment increased the enrichment index(EI),and the large amount of organic amendment increased the metabolic footprints of bacterivore(Baf)and fungivore(Fuf)and enrichment footprint(Ef).The relationships between Baf(or Fuf)and the increases in soil organic carbon(?SOC)and total nitrogen(?TN)were stronger than those of bacterivore(or fungivore)abundance with?SOC and?TN,except for the relationship between bacterivore abundance and ?SOC.The EI and Ef were positively correlated with ?SOC and ?TN.These findings suggest that the amount of organic amendment affects soil nematode activity and function at entry levels in soil food web,and that metabolic footprints of soil nematodes may be better indicators than their abundances in assessing their relationships with soil nutrients.
文摘At a rice wheat rotational free air CO 2 enrichment(FACE) platform, the effect of elevated atmospheric CO 2 on soil nematode communities in a farmland ecosystem was studied. Wheat plots were exposed to elevated atmospheric CO 2(ambient 370 μl/L + 200 μl/L). 32 families and 40 genera of nematode were observed in soil suspensions during the study period. Under FACE treatment, the numbers of total nematodes, bacterivores and fungivores exhibited an increasing trend. Because of the seasonal variation of soil temperature and moisture, the effect of elevated atmospheric CO 2 on soil nematodes was only observed under favorable conditions. The response of nematode communities to elevated atmospheric CO 2 may indicate the change of soil food web.
文摘Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity.However,the extent to which unique geomorphic formations influence soil biotic seasonal variation is not clear.Our aim was to define seasonal variations of soil biota in soils of different-aged terraces of the Makhtesh Ramon anticline erosional cirque in southern Israel.The strong effect of Makhtesh Ramon (Ramon crater) erosional fluvial terrace age initiated by climatic changes during the Late Pleistocene- Early Holocene period on seasonal variations in both soil properties and the abundance and composition of soil biota were demonstrated.However,age dependence was not constant and values for observed soil properties and microbial activity were negligible between younger and older terraces for certain seasons,while free-living nematodes along with bacterial-feeding group were strongly dependent on the geomorphic features of the ages throughout the study period.
文摘Soil biota play a crucial role in soil ecosystem stability, promoting organic matter decomposition and nutrient cycling. Compared to conventional farming,organic farming is known to improve soil properties such as aggregation. Despite the importance of soil microbial communities in soil biogeochemical processes, our knowledge of their dynamics is rudimentary, especially under different agricultural management practices. Here we studied the effects of vineyard management practices(conventional and organic) and soil aggregate fractions(micro-, meso-, and macroaggregates) on free-living soil nematodes.The abundance, diversity, and ecological indices, such as the Wasilewska index and trophic diversity, of free-living soil nematodes were determined. We found that the abundance of free-living soil nematodes was increased by organic farming. In addition, plant parasites were found to increase in macroaggregates in the organic plot, which may be attributed to the weeds present due to no-tillage and no herbicides. Nematode family network connectivity increased in complexity with increasing aggregate size, highlighting the importance of the interplay between nematodes and soil inter-aggregate pore size and connectivity.
基金funded by CONACYT for funding provided through project A1-S-21471。
文摘Background: Gradients in local environmental characteristics may favour the abundance of species with particular traits, while other species decline, or favour species with different traits at the same time, without an increase in average species abundances. Therefore, we asked: do variations in species and traits differ along gradients of deadwood variables? Do species abundance and trait occurrence change with species richness within or between functional groups? Thus, we analysed the beetle assemblages of five forest sites located in Italy, along the Apennines mountains.Methods: From 2012 to 2018 we sampled beetles and five deadwood types in 193 plots to characterise the deadwood gradient: standing dead trees, snags, dead downed trees, coarse woody debris, and stumps. We modelled beetle species relative abundances and trophic traits occurrences against the deadwood variables using joint species distribution models.Results: Out of 462 species, only 77 showed significant responses to at least one deadwood type, with a weak mean response across species. Trophic groups showed mostly negative responses to deadwood variables. Species abundance increased with species richness among sites only for phytophagous and saproxylophagous. Trait occurrence did not increase with species richness among sites, except for phytophagous and saproxylophagous.However, trait occurrence changed significantly with species richness of several trophic groups within some sites.We found that increases in species richness do not result in decreases in species abundance of a given trophic group, but rather null or positive relationships were found suggesting low interspecific competition.Conclusions: Our findings suggest that in Mediterranean mountain forests there is still room for increasing the level of naturalness, at least for what concerns deadwood management. On one side, our findings suggest that competition for deadwood substrates is still low, on the other side they indicate that increasing deadwood volume and types to improve overall beetle richness may increase also beetle abundances.
文摘Functional structure and diversity of soil free-living nematodes in a desert environment depend on plant gender and sampling site.The objective of this study was to compare the composition,abundance and tropic group of soil free-living nematodes in the upper 0–10 cm soil layer under the male and female Acanthosicyos horridus Welw.ex Hook.f.plants and in the inter-shrub open areas(control)in the Namib Desert,Namibia in April 2015.Soil moisture,organic matter(OM)and pH was also analyzed.Free-living nematodes were extracted from 100 g soil using the Baermann funnel procedure,and total number of nematodes was counted under a microscope.Community composition and diversity of soil free-living nematodes were analyzed using 18S rDNA sequences.Results indicated that a total of 67 groups,including 64 species,2 genera and 1 family were identified.Feeding behavior of 58 species were identified as follows:15 bacteria-feeding species,12 fungi-feeding species,10 plant-parasite species,5 omnivorous-predator species,8 animal-parasite species,5 invertebrate-parasite species and 3 non-free-living nematodes,known as marine species.Moreover,soil free-living nematodes were found to be affected by sampling locations and plant gender,and community composition and density of these nematodes were strongly influenced by soil OM content.Result confirmed that spatial location and plant cover were main factors influencing the diversity of soil free-living nematodes.Moreover,molecular tools were found to be very useful in defining the richness of soil non-free-living nematodes.In conclusion,the results elucidated the importance of biotic variables in determining the composition and abundance of soil free-living nematodes in the Namib Desert,Namibia.
基金supported by the National Natural Science Foundation of China(41971064,U20A2008 and 40801092)the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0302).
文摘The alpine wetlands in the Qinghai-Tibetan Plateau have degraded in recent decades.However,the response of the soil food web to the degradation is still unclear.Four habitats including a wet meadow(WM),a grassland meadow(GM),a moderately degraded meadow(MDM)and a severely degraded meadow(SDM)(sandy meadows)were selected along the degrees of degradation.The soil macrofaunal biomass and the environmental factors of vegetation and soil were investigated.The soil macrofaunal community biomass increased significantly from WMto MDM and decreasedto a very small amount in SDM,with most taxa disappearing.The biomass of the trophic groups of detritivores,herbivores and predators exhibited similar responses to soil macrofaunal communities.The relative biomass of detritivores increased from WM to MDM,but herbivores responded in an opposite manner,resulting in the dominant trophic group and trophic structure varying progressively from WM to GM to MDM.Soil properties but not vegetation determined the changes in trophic groups and trophic structure.The results implied that the higher trophic levels(carnivores or omnivores)responded more sensitively than the lower trophic levels(herbivores)to alpine wetland degradation.Our results also suggested that soil macrofauna have a habitat-specific characteristic trophic structure and can be used as indicators of soil health conditions.
基金the National Natural Science Foundation of China(31971534)the Innovation Scientists and Technicians Troop Construction Projects of Henan Province.
文摘The relative abundance of different components of the soil food web can vary tremendously in response to plant resource inputs.However,little is known about the mechanisms that plant resource regulates the energy fluxes and soil community composition.Here,we experimentally reduced litter and root inputs for two years in China at low-,mid-,and high-latitude forests to explore the effects of plant-derived resource inputs on the nematode energy flux and community composition.Litter reduction at high and mid latitudes and root removal at low latitudes reduced nematode richness but did not alter nematode abundance.Besides,litter reduction reduced energy fluxes of bacterial-feeding nematodes at mid latitudes and energy fluxes of plant-feeding,bacterial-feeding and omnivorous-predatory nematodes at low latitudes,thus reducing the energy fluxes of total nematodes in mid-and low-latitude forests.By contrast,root removal reduced energy fluxes and relative energy flux of plant-feeding nematodes in high-and low-latitude forests.In most cases,nematode diversity in different trophic groups increased with increasing energy flux to nematodes.Taken together,our results suggest that the effects of plant resource inputs on nematode energy flux are affected by climate and plant resource type,which improves our understanding of plant-soil interactions.
基金supported by The National Key Research and Development Program of China(2017YFC1200100 to J.D.)the National Natural Science Foundation of China(31822007 to W.H.).
文摘Aims Plant invasions have the potential to affect the community structure of soil nematodes,but little is known about whether such effects are mediated by aboveground herbivores since invasive plants are not completely released from herbivores in the introduced range.In this study,we explored how aboveground insect herbivores mediated the effect of invasive plant Alternanthera philoxeroides on soil nematodes and examined the temporal variations of such an herbivory-elicited effect.Methods We conducted a greenhouse experiment by applying different herbivory treatments(no insect herbivores,specialist Agasicles hygrophila and generalist Cassida piperata)to potted A.philoxeroides,and then measured the community compositions of soil nematodes in corresponding pots on the 1st,10th and 20th day after removal of all herbivores.In addition,the carbon content of roots and root exudate of A.philoxeroides were also measured.Important Findings Our results showed that aboveground herbivory significantly increased the abundance of soil nematodes of A.philoxeroides,likely plant feeder nematodes,after insect herbivores were removed immediately(1st day).However,such impacts waned with time and there was no significant difference at later stages(10th and 20th days).Furthermore,the effects of specialist A.hygrophila and generalist C.piperata herbivory were consistent on the abundance of soil nematodes.Overall,our results suggest that aboveground insect herbivores have the potential to alter the effects of plant invasions on soil nematodes,but such impacts are transient.Furthermore,our study highlighted the importance of integrating the effects of above-and belowground organisms when evaluating the impacts of plant invasions.
基金This research was supported by the K.C.Wong Education Foundation(GJTD-2019-10)the National Natural Science Foundation of China(41877047)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB15010402).
文摘Soil nematodes are the most numerous components of the soil fauna in terrestrial ecosystems.The occurrence and abundance of nematode trophic groups determine the structure and function of soil food webs.However,little is known about how nitrogen deposition and land-use practice(e.g.mowing)affect soil nematode communities.We investigated the main and interactive effects of nitrogen addition and mowing on soil nematode diversity and biomass carbon in nematode trophic groups in a temperate steppe in northern China.Nitrogen addition and mowing significantly decreased the abundance of soil nematodes and trophic diversity but had no effects on nematode richness and the Shannon-Wiener diversity.Nitrogen addition influenced soil nematode communities through decreasing soil pH.Mowing influenced soil nematode communities through decreasing soil moisture.Nitrogen addition enhanced the bacterial energy channel but mowing promoted fungal energy channel in the soil micro-food web.Our study emphasizes that ecosystem function supported by soil organisms can be greatly influenced by nitrogen deposition,and mowing cannot mitigate the negative effects of nitrogen deposition on soil food webs.
