| Hongze Lake is the fourth largest freshwater lake in China,where the Huaihe River flows into from its southwest.Owing to sluggish water flow and sedimentation,a distinctive wetland has been established at the confluence of rivers and lakes with ecological and productive functions over an extended period.There are numerous natural wetlands,including lake grass beaches and reed beds,as well as artificial forests,farmland,and breeding ponds that have been created through long-term human use of wetland resources over the past few decades.A considerable number of previous studies have concentrated on the impact of land use/cover change on wetland ecology and environmental functions,with research subjects primarily encompassing water quality,plants,microorganisms,ecosystem service value,among others.These investigations have made significant strides.However,the research on soil fauna in the confluence zone of rivers and lakes remains inadequate.Soil fauna is a fundamental component in maintaining soil structure,ensuring quality and functionality.Together with plants and microorganisms,soil fauna forms an integral part of soil biodiversity.The composition of soil fauna community was significantly impacted by changes in land use/cover,and the response of fauna community to such changes indicates environmental alterations.An in-depth investigation into the impacts of wetland land use/cover change on soil fauna is anticipated to establish a theoretical foundation for examining land use/cover change from the perspective of soil fauna biodiversity alteration.This paper focuses on the intersection area of rivers and lakes in Hongze Lake,selecting natural cover wetlands such as lake grass flats and reed flats,willow and poplar plantations,as well as rice and wheat croplands for land use analysis.Soil samples were collected during May,August,November 2022 and February 2023 to investigate the seasonal variation characteristics of soil fauna.soil macrofauna and mesomicrofauna were isolated and identified,followed by a comprehensive study on their groups,composition,quantity,diversity and seasonal dynamics.Furthermore,their distribution in both 0～10 cm and 10～20 cm soil layers was analyzed.The community structure and diversity of soil bacteria and fungi were simultaneously investigated.Soil temperature(ST),soil water content(SWC),bulk density(SBD),electrical conductivity(EC),p H,organic carbon(TOC),total nitrogen(TN),dissolved organic carbon(DOC)and other soil physical and chemical properties were analyzed to determine the biological and abiotic factors affecting soil fauna diversity.This study provides a theoretical foundation for conserving soil biodiversity and assessing ecological risks associated with land use/cover modes in eco-productive wetlands at intersection areas.The principal findings and deductions of this manuscript are delineated as follows:(1)A total of 5041 soil macrofauna,classified into four phyla,eight classes and nineteen orders,were collected from five different cover/land use types.The dominant taxa comprised Porcellionidae,Formicidae and Staphylinidae,constituting 59.59% of the total catch.There were 11 common taxa accounting for 37.00%,while rare taxa numbered 21 and accounted for only 3.41%.In contrast,3 classes and 13 orders of Arthropods were represented by a total of 2879 soil meso-microfauna.The dominant groups,namely Collembola,Prostigmata and Oribatida,collectively accounted for 78.15% of the total catches.Additionally,there were 8 common species that made up 17.78% of the total catch and 11 rare groups that contributed to a mere 4.06%.(2)The abundance and diversity of soil fauna were found to be higher in plantation(willow,poplar)than in natural cover(reed,lake grass)and rice-wheat cropland at both soil macrofauna and mesomicrofauna based on the number of individuals and taxa.The abundance of soil fauna individuals and communities varied seasonally,with higher values observed during summer and autumn compared to winter and spring.The lake grass beach and reed beach had the highest number of individuals for soil macrofauna in November,while August saw the highest number of groups.The willow forest had the highest number of individuals and groups in November,whereas August was when poplar forest recorded its peak numbers.Farmland witnessed its maximum count of individuals and groups in May.In contrast,the population of soil meso-microfauna exhibited significant seasonal fluctuations,with the exception of farmland.The individual count of lake grass beach,reed beach,and willow forest was highest in August,while that of poplar forest peaked in November.The number of soil meso-microfauna groups across various regions gradually declined with seasonal changes(spring,summer,autumn,and winter).(3)The vertical distribution of soil fauna individuals and groups exhibited significant superaggregation characteristics.4179 soil macrofauna and 1869 soil meso-microfauna were captured in 0～10cm soil layer,accounting for 82.90% and 64.92% of the total catches,respectively.In the 10～20 cm soil layer,a total of 862 soil macrofauna and 1010 soil meso-microfauna were captured,representing 17.10%and 35.08%,respectively.The difference in cover/land use change resulted in significantly higher numbers of soil macrofauna and meso-microfauna individuals and groups in willow and poplar plantations compared to those found in lake grassland beaches,reed beaches,and farmland across different soil layers.Additionally,the aggregation of soil meso-microfauna individuals and groups was lowest during February.(4)The composition of soil fauna communities was significantly influenced by changes in land cover and use,resulting in shifts in dominant groups.The dominant soil macrofauna in lake grass flat were Staphylinidae,whereas Porcellionidae and Staphylinidae dominated the soil macrofauna in reed flat.Willow and poplar plantations were predominantly occupied by Porcellionidae and Formicidae.The dominant groups of farmland soil macrofauna varied significantly with seasons,primarily comprising mole Gryllotalpidae,Araneae,and Staphylinidae.In contrast,the changes in soil meso-microfauna revealed that Collembola was the dominant group in lacustrine grassland flats,while Collembola and Prostigmata were predominant in reed flats,willow woods,and farmland.Poplar forests were mainly dominated by Collembola,Prostigmata,and Oribatida.(5)The seasonal variations exerted a significant impact on the diversity and abundance of soil fauna.During the months of February,May,and August,the diversity indices of macrozoa in willow and poplar plantations exceeded those found in lake grass beaches,reed beaches,and farmland.The richness index of soil fauna in other land use/cover exhibited higher values during May and August compared to November and February.In comparison,the diversity of soil meso-microfauna indicated that the lake-grass beach had a significantly higher diversity index than the willow forest in May.The reed beach showed the highest diversity index in August,while the willow forest exhibited its highest diversity index in November and February.Additionally,the richness index of willow forest was superior across all four seasons.(6)Similarity analysis of soil macrofauna across different cover types/land uses revealed a moderate degree of dissimilarity to similarity among the genera.Among them,the poplar forest and willow forest exhibit the highest degree of similarity,while farmland and poplar forest display the lowest.The similarity between lake grass flat,reed flat,and poplar forest is higher across different seasons;however,farmland exhibits lower similarity across different seasons.In contrast,the dissimilarity between soil mesomicrofauna genera ranges from moderate to very low.Among them,the reed beach,lake beach,willow forest and poplar forest exhibit high similarity while farmland and other types of land show moderate similarity.The community structure of soil meso-microfauna varies significantly across different seasons.(7)The diversity and richness of soil macrofauna were positively correlated with the diversity of soil bacteria and fungi,while the dominance and evenness indices were negatively correlated with the diversity of soil fungi.In contrast,there was a negative correlation between the diversity index,evenness index,and richness index of soil meso-microfauna and the bacterial diversity index of soil.However,the diversity and richness indices of soil meso-microfauna were positively correlated with the fungal diversity index of soil,while the dominance index showed a negative correlation with it.(8)Analysis of the correlation between soil fauna and environmental factors revealed that TOC,SWC,TN,DOC and p H were the primary environmental factors influencing the distribution of flood macrofauna.On the other hand,soil fauna distribution was primarily influenced by SWC,EC,ST,TOC and p H as key environmental factors.Soil properties such as SBD,p H,TN and TOC play a crucial role in shaping the composition of soil bacterial and fungal communities.(9)The dominant groups of soil macrofauna,Porcellionidae and Formicidae,showed a positive correlation with the abundance of Bacterales,norank＿Vicinamibacteraceae,norank＿KD4-96 and Gaiella in the dominant groups of soil meso-microfauna.Additionally,there was a significant negative correlation with norank＿Anaerolineaceae.The soil fungal community exhibited significant positive correlations with Mortierella and negative correlations with Talaromyces,including Porcellionidae,Formicidae,Collembola,Prostigmata and Oribatida. |
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