Structure Characteristics And Succession Of Soil Animal Community In The Yellow River Delta

Soil animal community in the Yellow River Delta was studied intensively and systematically for the first time in this study, and its characteristics and succession process were discussed from multi-levels as well. Sampling sites were set on the basis of soil-forming period, vegetation type, soil properties, human disturbance and other factors. Communities structure characteristics were analyzed from 3 levels and 4 perspectives of total soil animals, total soil mites, soil oribatid mites and soil collembola, and the differences among communities were analyzed from the aspects of species composition, quantitative distribution, seasonal changes, diversity and similarity and other aspects. Succession of the soil animal community was explored mainly based on the influence of soil-forming period and vegetation type to the community structure.Results of this study show that, the geographical environment of the Yellow River Delta is simple, both species number and quantity of the soil animals are poor, average density of animal is less than 10 thousand individuals in the entire region, and only 17 classes or orders of the soil animals are obtained in this study. For the soil animals among these 11 sampling sites from three ages, 6 different vegetation habitat, diversity, evenness and dominance show little difference, but the similarity varies greatly.Mites and Collembola are the dominant groups in all the 11 sampling sites, and they are the only two dominant groups at each site. The annual average A / C value of the whole area is 2.04, significantly greater than 1. A / C values in winter and summer are comparatively larger, indicating that adaption and resistance of mites to low temperature or drought is stronger than that of Collembola.Dominant groups of soil animals in this area are significant, community heterogeneity and diversity are low. Among the 11 sampling sites, site A (farmland) has the largest diversity index, indicating that the soil environment is poor, the soil is lean, salinized, and not suitable for soil animals,to survive, on contrast, human activities improved the soil environment, both the species and number of soil animals were increased, Soil animals has the highest diversity in autumn in the four seasons, while the diversities in winter and summer are low, indicating that the soil animals are very sensitive to soil temperature and soil moisture changes.Although the soil formation age and the vegetation are very different,soil animal community similarity among the 11 sampling sites is high, indicating that the most important environmental factors that directly impact on soil animals are "water" and "salt."Survey results show that, the number of Cryptostigmata(Oribatida) is the largest, followed by Prostigmata, and Mesostigmata is the least. Percentages of Cryptostigmata and Prostigmata are stable in the four seasons, with a varity order of January Prostigmata >Mesostigmata. The proportion of the three suborders among the 6 vegetations habitats are different significantly. The proportion of Mesostigmata in Phragmites australis wetland and in Phragmites australis - Aeluropus sinensis wasteland habitats is relatively low, and Prostigmata in farmland is the lowest, while Cryptostigmata in the farmland is the highest. Although the soil mites in layer III is significantly less than in layer I and layer II, the surface concentration is not strong.64 species of soil oribatid mites belonging to 52 genera of 38 families were obtained in this investigation, including 47 known species and 17 unknown species. With one dominant species: Epilohmannia pallida pacifica, 6 sub-dominant species: Multioppia wilsoni, Scheloribates laevigatus, Oppiella nova, Tectocepheius velatus,, Xylobates tenuis, and Trhypochthonius japonicus. Fauna analysis was carried out on these 47 known species in combination with the literature data, the overlapping coefficient between this area and central China is the highest, followed by Northeast and South China area.Species composition and quantity distribution of soil oribatid mite communities among these 11 sites are different significantly, but the change is similar. Site A, B and E in the farmland with the largest number of species and quantity. Both the change tendency of species number and the individual number in this area of three ages is coherent, with a sequence of ancient age > recent age> present age The species number and the density of soil oribatid mite increased. with the increase of soil-forming period. Species composition and quantity distribution of the soil oribatid mite communities differ significantly among these 6 vegetation habitats . Both the number of species and the individual have the same change sequence of Phragmites australis wetland < Phragmites australis - Aeluropus sinensis wasteland < Suaeda salsa - Aeluropus sinensis wasteland < Tamarix chinensis - Artemisia fauriei wasteland.Species composition of the soil oribatid mite community change with a sequence of autumn> winter> spring≈summer; individuals number in autumn is the most, and densities do not differ much in the other three seasons. The difference of seasonal fluctuation in the seven dominant genera or subdominant genera is observable, Epilohmannia is the dominant genera or sub-dominant genera in four seasons with the smallest number changes; Trhypochthonius and Xylobates seasonal fluctuation trends are the same, with the least number in summer. Number of Tectocepheius in summer is the largest. The number of Scheloribates in the fall is comparatively low, while much many in the other three seasons,while for Oppiella, with the largest number in autumn but very few in the other three seasons. Multioppia has the largest fluctuation in number, with the largest number in winter and spring, but fewer in summer and autumn.Both the number of species and individuals of the three groups of soil oribatid mites in the Yellow River Delta are even. The community structure is O type, the Structure characteristics of the soil oribatid mites communities in this area of three ages, the 6 different vegetation habitats and four seasons are similar, most are O type. Results are different partially with MGP- I and MGP II analysis.The heterogeneity and diversity of soil oribatid mite in the Yellow River Delta are high, The diversity indexes at most sampling sites are between 2.3 to 3.0, and the differences among every site are significant. The heterogeneity of soil oribatid mite of this area of three ages is high, and the diversity index is relatively high. Both the number of groups and the diversity index of the soil oribatid mite are significantly different in the 6 different types of vegetation habitats.None similarity index is higher than 0.75 of the soil oribatid mite communities among these 11 sampling sites, so the similarity is relatively low, and the majority of communities are not similar or extremely not similar. The similarity of the soil oribatid mite communities in this area among 3 ages and 6 vegetation habitats varies greatly. The similarity of this area between ancient and recent age is relatively high, and all the similarity coefficients among Phragmites australis wetland and other vegetation habitats are relatively low.22 genera belonging to 8 families of soil Collembola are obtained in the investigation, of which Onychiurus, Folsomina, Hypogastrura and Folsomia are the dominant genus, constituting the main body of the soil Collembola community. Compared to the soil oribatid mite community, the number of soil Collembola genera is less, with more stable and significant dominant genera. The species composition and quantitative distribution of the soil Collembola community among these 11 sampling sites are significantly different. Both the number of species and individuals of the soil Collembola in this area from the three ages change at the same order: ancient age >recent age>persent age. There are the least number of Collembola in Phragmites australis wetland habitats, and no significant difference for the other 5 habitats.Both the species composition and the number of individuals of soil Collembola change at the same order: fall > spring> summer> winter. The dominant genera in the four seasons is the same, but the seasonal change trend of the dominant genera shows significant difference. Onychiurus is a typical deep-soil-living type with relatively stable number. number of Folsomina successively increases with winter→Spring→Summer→Autumn changing. while Hypogastrura has the largest number in winter. Folsomia were relatively less in Autumn, found at only four sampling sites, and the number decreased significantly compared with the other three seasons.The results of this study show that, the soil animal communities composition is not very different at high-level taxa, which can not fully demonstrate the process of their succession. That is to say, the similarity of soil animal communities is relatively high at high-level taxa, and it is less use to investigate the succession of soil animal communities at this level. However, with the succession of soil formation period or plant community, similarity among soil animal communities shows certain regularity, namely, the nearer the age interval of the soil formation period, the higher the community similarity; With the succession process of Phragmites australis wetland, Phragmites australis - Aeluropus sinensis wasteland, Suaeda salsa - Aeluropus sinensis wasteland and Tamarix chinensis - Artemisia fauriei wasteland, the similarity of soil f animal communities decreased gradually, the closer succession stage, the greater the similarity among the soil animal communities. We also show that, on the taxa of class or order classification level, for habitats of different vegetation types, although the soil animal communities are similar, but with the succession of plant communities, their composition still showe some differences, and this difference is much greater than the difference caused by the soil formation age.The density differences of the soil mites in this area among 3 ages and 6 different vegetation habitats are significant, soil mites number increased with the increase of soil formation period, and all with a sequence of Cryptostigmata > Prostigmata >Mesostigmata, and increase with the succession process of vegetation. The proportion of Cryptostigmata increases while Mesostigmata decreases with the succession of vegetation, and the change of Prostigmata shows no apparent regularity, and therefore, for the study of the succession of soil animal communities, Cryptostigmata and Mesostigmata are much more important than Prostigmata.Results of this investigation show that, both the change tendency of species and individual number of soil oribatid mite in this area from three ages are the same, with a sequence of ancient age> recent age> present age, species number and density of soil Oribatida increased with the increasing of soil-forming period. Both the species composition and quantitative distribution of soil oribatid mite communities in the 6 different vegetations habitants show extremely significant differences. Both the numbers of species and individuals of soil oribatid mite community show a certain regularity with the succession process of vegetation, that is, with a order of Phragmites australis wetland << Phragmites australis - Aeluropus sinensis wasteland < Suaeda salsa - Aeluropus sinensis wasteland << Tamarix chinensis - Artemisia fauriei wasteland.With the succession of plant communities, the structure of soil oribatid mite community changes at a certain regularity, the species number and relative number of M-group of soil oribatid mite community decreased gradually, while the P-group increased gradually with the succession of Phragmites australis wetland→Phragmites australis - Aeluropus sinensis wasteland→Suaeda salsa - Aeluropus sinensis wasteland→Tamarix chinensis - Artemisia fauriei wasteland.The heterogeneity of soil oribatid mite communities in this area of three ages is high, the diversity indexes are relatively large, and both the species number and diversity of the soil oribatid mite communities increase with the soil formation period. Both the number of species and the diversity index of the soil oribatid mite communities are significantly different among the 6 different types of vegetation habitats. The species number, evenness and diversity of the oribatid communities increased gradually with the succession of the plant communities.By comparison of the similarity of soil oribatid mite communities in this area from three ages, we can see that, the further apart from the soil formation period, the smaller the community similarity. The similarity difference of soil oribatid mite communities for the 6 different vegetations habitats varied greatly. The similarity coefficient among Phragmites australis wetland and other vegetation habitats were relatively low. The similarity of oribatid mite communities decreased with the succession of plant communities, the closer the succession stage, the greater the similarity among communities.Both the change tendency of species and individual number of soil Collembola in the yellow river Delta of three ages and the 6 vegetation habitats show significant difference, but the changing tendency is the same, with a sequence of ancient age> recent age>> present age; the species number and quantity in Phragmites australis wetland is the least , and the differences among the other 5 habitants are not great.For the soil Collembola in the yellow river Delta of three ages and the 6 vegetations habitats, the diversity, evenness and dominance show no great difference.The soil Collembola communities similarity in this area of three ages changed regularly with the different soil formation periods, the closer the soil formation period, the higher the similarity. The similarity coefficient of the soil Collembola communities regularly decreased with the vegetation succession process. The maximum similarity coefficient occurred between Suaeda salsa - Aeluropus sinensis wasteland and Tamarix chinensis - Artemisia fauriei wasteland, among Suaeda salsa - Aeluropus sinensis wasteland, Tamarix chinensis - Artemisia fauriei wasteland and Phragmites australis - Aeluropus sinensis wasteland, it is similar or very similar. We studied the soil animal community in the Yellow River Delta intensively and systematically for the first time, and discussed the characteristics and succession process of the soil animal community from multi-levels.Results show that, the soil environment of this region is poor, and the soil is lean and salinized, and not suitable for soil animals to survive, resulting in significant dominant groups of soil animals, poor community heterogeneity, and low community diversity.It is also shown that, high-level taxa of soil animals can not fully reflect the succession process of community. Cryptostigmata and Mesostigmata change regularly with the succession of soil formation period and vegetation, and therefore more attention should be paid to Cryptostigmata or Mesostigmata in the study of soil animal community succession. Especially, with the succession of soil formation period or vegetation, the soil oribatid mite have shown similar regularity: with increase in species and density, gradual increase in homogeneity and diversity, the further apart from the succession of soil formation period and vegetation, the smaller the community similarity. However, with the succession of plant communities, the impact of changes in soil oribatid mite communities is more evident than that of soil formation period. Soil Collembola are more vulnerable to other environmental factors (such as temperature, humidity), and the response regulation of soil Collembola to soil formation period is not comparable to that of soil oribatid mite, reducing its importance in the study of soil animal community succession.