Soil oribatid mite community structure and its relationship with environmental factors in different agricultural land-use types in Shibing Karst

The karst world natural heritage site is characterized by fragility due to severe rocky desertification. Buffer zone functions as the ecological barrier of the core area of the heritage site, and can play an ecological filtering role in the core area. Therefore, buffer zones are of great ecological significance. In order to reveal the community characteristics of soil oribatid mites in different agricultural land-use in the buffer zone of Shibing Karst World Natural Heritage and their relationship with environmental factors, soil oribatid mites in the buffer zone of corn field (CF), golden pear garden (GP) and tobacco field (TF) were collected in September 2021. A total of 1220 oribatid mites belonging to 79 genera and 41 families were found in the study. Our key results include (1) The family number, genus number, individual number, and individual density of GP are higher (2) Scheloribates is the dominant group, 22 genera such as Oppiella, Tectocepheus, and Xylobates are common groups, and 56 genera such as Neoribates and Protoribates are rare groups. (3) The Diversity index of GP is higher than that of other cultivated land types. Community similarity analysis shows that the similarity between GP and CF is high, but all habitats are at a medium level of dissimilarity. (4) Analysis of the ecological group of oribatid mites shows that Poronota is more abundant than Macropylina and Gymnonota. (5) The Diversity index, richness index, family and genus level of oribatid mites were significantly positively correlated with soil humidity (SH) and the number of genera, individuals and individual density were significantly positively correlated with total phosphorus (TP). Redundancy analysis indicates that total phosphorus (TP), total potassium (TK), and soil organic matter (SOM) are the main environmental factors affecting the distribution of soil oribatid mites communities. Based on the above research results, it can be seen that there are differences in the community structure of soil oribatid mites in different agricultural land-use in the study area. The use of dominant genera of mites can preliminarily indicate the soil ecological environment of different agricultural land-use. The research results provide basic data for the biodiversity protection of soil animals in different agricultural land-use in the buffer zone of Shibing Karst World Natural Heritage.


Introduction
Oribatid mites are a class of arachnids constituting a large proportion of soil macrofauna.They look like beetles, and their body walls exhibits varying degrees of ossification and mineralization, with varying shades of color.Oribatid mites exist in various terrestrial ecosystem and are widely distributed, they are an important part of soil Arthropod [1,2].Oribatid mites have the characteristics of large quantity and diverse food habits, and can participate in the decomposition and nutrient transformation of organic matter in nature, playing an important role in soil ecosystems [3][4][5].Research has shown that different vegetation and forest types affect the community structure of oribatid mites.In evergreen broad-leaved forests, soil oribatid mites are dominated by those with high degree of ossification of body wall.At the initial stage of ecological restoration of moderate rocky desertification, soil oribatid mites are dominated by Poronota [6], while the lower level group of oribatid mites have comparative advantages in the degradation of litter [7].In addition, human interference has a significant impact on the community structure and diversity of soil oribatid mites [8].Due to their sensitivity to environmental changes, seasonal changes in the natural environment human factors can have a significant impact on the species and quantity of oribatid mites [9].Therefore, oribatid mites are considered one of the ideal indicator organisms for monitoring soil quality and fertility [10][11][12][13] Global environmental change is an important research hotspot in various countries, and a series of environmental issues have attracted the attention of researchers.Among them, changes in greenhouse gas density can affect the distribution of oribatid mites, and high concentrations of CO 2 are more suitable for the survival of oribatid mites [14].CO 2 concentration affects the litter layer and indirectly reduces the population of soil oribatid mites [15].Human activities can also affect the community distribution of oribatid mites [16].Mainly human agricultural economic activities, especially various operations engaged in agricultural land.Due to the fact that soil mites are a widely distributed group of small and medium-sized soil animals, and can respond to changes in the soil environment, such as heavy metal pollution levels and pesticide treatment concentrations, which are negatively correlated with the number of soil mites [17,18].Human activities can suppress the reproduction of populations in the community, except for the oribatid mite, thereby making the more adaptable oribatid mite a dominant species [19].In different farming systems, appropriate human activities have effectively increased the number of individuals of various types of oribatid mites and exhibited significant seasonal changes [20].The community structure and distribution characteristics of oribatid mites are important reference for environmental quality assessment.
Spatial and local environmental factors change the soil environment and, thereby, the structure of the soil mite community through a single or comprehensive action [21][22][23].The physical and chemical properties of plant litter and soil are important reasons for affecting the change of soil oribatid mite community structure [24], such as soil temperature and humidity [25].Through the correlation analysis of soil organic matter, pH and other soil environmental indicators with the number of individuals and groups of soil oribatid mites, it can provide an important basis for screening the indicator species for soil environmental monitoring [23,26].In the special soil environment of Karst caves, available nitrogen, available potassium and light intensity are the main environmental factors affecting the soil oribatid mite community [27].In summary, soil physical and chemical environmental factors affect the group, genus, individual quantity, diversity index, and distribution characteristics of soil mites.
Currently, there is a diversity of research on oribatid mites [28], among which research on oribatid mites in heritage sites mainly includes reports on new species of oribatid mites [29], seasonal distribution characteristics of oribatid mites [30], investigation of oribatid mites groups and individual numbers, and community structure of mites under different forest and crop types [29,[31][32][33][34][35][36].These studies provide us with some reference materials, but there is a lack of research on describing the structure of soil oribatid mites communities from the perspective of heritage buffer zones [23].As the 'barrier umbrella' of the core area of heritage sites, buffer zones have the function of protecting the outstanding universal value of heritage sites.They should protect the environment while balancing agricultural development and environmental protection.This study can evaluate the impact of different tillage methods on the soil environment of agricultural ecosystems by studying the structural characteristics of soil oribatid mite communities.Because corn is a representative traditional agricultural crop in the buffer zone, while golden pear and flue-cured tobacco are representative modern economic crops, and these three types of agricultural land have the largest planting scale and representativeness.Therefore, corn fields, golden pear fields, and tobacco fields were selected as sample plots for research, in order to provide theoretical significance for the ecological environment protection of the buffer zone.

Overview of the study area
Shibing Karst World Natural Heritage is one of the series of 'South China Karst' heritages, and was included in the The World Heritage List in 2014.It meets two selection criteria for World Natural Heritage sites, one being the seventh criterion: to contain superlative natural phenomena or areas of exceptional natural beauty and aesthetic importance; The second is the 8th standard: to be outstanding examples representing major stages of earth's history, including the record of life, significant on going geological processes in the development of landforms, or significant geomorphic or physical features.The study area is located in Shibing County, Qiandongnan Miao and Dong Autonomous Prefecture of Guizhou Province, between 108°01 ′ 36 ′ ′∼108°10 ′ 52′ ′ E, 27°04 ′ 51′ ′∼27°13 ′ 56′ ′ N, and in the mountain plain slope zone where the eastern edge of the Yunnan-Guizhou Plateau transits to low mountains and hills in western Hunan [37].The Karst is strongly developed, the terrain is broken, and the terrain gradually decreases from northwest to southeast, with an average elevation of 526 m.The climate belongs to the subtropical monsoon humid climate, warm in winter and cool in summer, with four distinct seasons.The annual average temperature is 14℃-16℃, and the annual rainfall is 1060-1200 mm [38].The core area of Shibing Karst World Natural Heritage is 102.80 km 2 , the buffer area is 180.15 km 2 , and the total area is 282.95 km 2 [39,40].The Soil type is mainly lime soil formed by the weathering of limestone and dolomite [41].The buffer zone is distributed with large-scale tobacco fields and golden pear gardens, while traditional farmland is mainly corn fields [36].The planting of corn, golden pears, and tobacco in the buffer zone has been carried out for a long time and has a wide planting range, with high transportation accessibility, which is conducive to the selection, setting, and sample collection of research plots [42].

Sample plot setting and sample collection
In September 2021, a field survey was carried out in the buffer zone of Shibing Karst World Natural Heritage.Three types of agricultural land were selected, namely corn field (CF), gold pear garden (GP), and tobacco field (TF).According to the actual conditions of the three types of agricultural land, three repeated quadrats with the size of about 100m 2 were set for each habitat.Five points were taken in the 'Z' shape, and the 0∼5 cm and 5∼10 cm soil layers were continuously sampled with a cylindrical soil ring cutter with the diameter of 100 mm and the height of 64 mm, a total of 90 soil mite samples (3 types of agricultural land × 3 quadrats × 5 sampling points × 2 soil layers).All the soil samples are packed into cotton bags with good air permeability and numbered taken to the laboratory for analysis.

Isolation and identification of oribatid mite specimens
Place 18 soil sample under a Tullgren dry funnel and bake it continuously for 48 h using a 60 W incandescent lamp.During baking, switch on and off the lights at an interval of 15-20 min, and the baking temperature should be controlled at around 35 C °C.At the same time, place a beaker containing a 75% alcohol diluted solution under the dry funnel to collect animal specimens.Using the Olympus SZX2-FOF stereoscopic microscope, the oribatid mite were separated from soil animals, washed and fixed with 75% alcohol.The oribatid mite were transferred to a test tube containing lactic acid and made transparent for approximately 30 days for subsequent identification.Place the transparent specimens under the Olympus CX41RF microscope to observe the morphology of soil oribatid mites.'A manual of Acarology (3rd edition)' et al were used for identification of oribatid mite specimens [43][44][45].The specimens are identified to the first order of genus, while recording the individual number of oribatid mites in the soil.

Determination of environmental factors
During the same period, a shovel was used to collect 15 cm×15 cm soil for chemical analysis in each quadrate according to the 0-5 cm and 5-10 cm soil layers.The soil of the upper and lower two layers of the same soil was mixed on the plastic film, and the mixed soil was about 1 kg.A total of 9 samples were collected (3 kinds of agricultural land ×3 quadrates ×1 mixed sample).In each quadrate, one soil sample (3 kinds of agricultural land ×3 quadrates ×2 vertical profile layers) was collected with 100cm 3 ring knife for physical analysis.A total of 18 soil samples were collected, and the physical property data of the upper and lower layers of soil taken from the same sampling point were averaged.Soil temperature (ST) and soil humidity (SH) were measured using the TASITA622A instrument.The illumination (E) is measured using a SMARTSENSORAS813 instrument.The natural water content (NWC), saturated water content (SWC), and bulk density (BD) of the soil were measured using the in situ ring knife method.The total soil porosity (P) was calculated using P = 93.947-32.995* BD.The potential of hydrogen (pH) with the potentiometric method.Total nitrogen (TN) with the semi-micro Kjeldahl method, total phosphorus (TP) with sulfuric acid-perchloric acid digestion, molybdenum with the antimony anti-colorimetric method, total potassium (TK) with hydrofluoric acid-perchloric acid digestion and flame photometry, and available potassium (AK) with neutral ammonium acetate leaching and flame photometry.Soil organic matter (SOM) was determined by Potassium dichromate oxidation external heating method [46].

Data analysis
(1) Quantity dominance [47]: According to Zheng's method, individuals with a proportion greater than 10% of the total catch are labeled as dominant groups (+++), those with a proportion between 1% and 10% are labeled as common groups (++), and those with a proportion less than 1% are labeled as rare groups (+).
(2) Community diversity analysis [48] was performed using Equations: where s is the number of groups, N is the total number of mites, n i is the number of individuals in group i, and P i is the proportion of individuals in group i to the total number of individuals in the community.
(3) Analysis of community similarity [49] was performed using equation: where a is the number of community groups A, b is the number of community groups B, and c is the number of common groups between the two communities.0 < q < 0.25 is high dissimilarity, 0.25 q < 0.5 is medium dissimilarity, 0.5 q < 0.75 is medium similarity, and 0.75 q < 1 is high similarity.
(4) Analysis of the community structure of oribatid mites [50]: using the oribatid mite MGP analysis method, oribatid mites are divided into three categories: M represents Macropylina, G represents Gymnonota, and P represents Poronota.Calculate the percentage of M, G, and P group genera using MGP -I analysis; Calculate the percentage of M, G, and P individuals using MGP -II analysis.The MGP classification criteria are shown in table 1.
(5) Statistical analysis: data were organized by Microsoft Excel 2020 software; Data were analyzed using IBM SPSS 22.0 software, and univariate analysis of variance (ANOVA) was used for community differences, with the significance level being p < 0.05.Data cartography is performed in Origin 2021 and CANOCO 5.0 software.At the family level (figure 1), GP has the highest number of soil oribatid mites, while TF has the lowest number of families, manifested as GP > CF > TF.Among them, there was a significant difference between GP and TF (F = 3.764, df = 2, p < 0.05).At the genus level (figure 1), GP has the highest number of genera of soil oribatid mites, while TF has the lowest number of genera, with the order being GP > CF > TF.Among them, there was a significant difference between GP and TF (F = 3.431, df = 2, p < 0.05), while there was no significant  Usually, individuals with a proportion greater than 10% of the total catch of oribatid mites are labeled as dominant genera, those with a proportion between 1% and 10% are labeled as common genera, and those with a proportion less than 1% are labeled as rare genera.From the composition of dominant, common, and rare genera of oribatid mites, it can be observed that there are significant differences in the composition of oribatid mites in the three types of agricultural land (figure 2).In the habitat of CF, the dominant genera of oribatid mites are Scutovertex, Scheloribates, and Xylobates, while the rare genera are Hypochthoniella, Epilohmannia, and Trichogalumna.The number of individuals in the dominant, common, and rare genera accounts for 39.77%, 44.60%, and 15.63% of the total number of individuals in this habitat, respectively.In the habitat of GP, the dominant genus of oribatid mites is Scheloribates, while the rare genera are Hypochthonius, Arcoppia, and Perxylobates.The number of individuals in the dominant, common, and rare genera accounts for 11.89%, 74.30%, and 13.80% of the total number of individuals in this habitat, respectively.In the habitat of TF, the dominant genera of oribatid mites are Oppiella, Tectocepheus, and Scheloribates, while the rare genera are Pterochthonius, Yoshibodes, and Oribatula.The number of individuals in the dominant, common, and rare  genera accounts for 46.74%, 51.63%, and 3.26% of the total number of individuals in this habitat, respectively.It can be seen that there are certain differences in the dominant genera of oribatid mites distributed in different agricultural soils, while the individual numbers of Scheloribates, Tectocepheus, and Oppiella dominate.

Results and analysis
We selected the top 1% (dominant and common groups) of the three types of agricultural land oribatid mites for classification and sorting, with 10, 14, and 4 exclusive genera for CF, GP, and TF, respectively.There are 14 genera that exist in all three types of agricultural land, and 16 groups appear in at least two habitats (figure 3).

Diversity and similarity of soil oribatid mite communities in different agricultural land-use
Diversity analysis of communities is used to characterize the complexity of community composition and their level of ecological organization [49].The results of community diversity analysis are shown in figure 4. The diversity index of oribatid mites in GP was the highest was GP > CF > TF.There was a significant difference between GP and TF (F = 3.525, df = 2, p < 0.05) The richness index of oribatid mites in GP is the highest, with GP > CF > TF in order.There was a significant difference between GP and TF (F = 3.338, df = 2, p < 0.05).The  evenness index of TF is the highest, in the order of TF > GP > CF, and there is no significant difference among the three habitats (F = 2.718, df = 2, p > 0.05).The dominance index of CF is the highest, with CF > TF > GP in order.
The top ten groups of soil oribatid mites in different agricultural land-use in the study area are Scheloribates, Tectocepheus, Oppiella, Scutovertex, Xylobates, Trichogalumna, Truncopes, Mochlozetes, Microppia, and Chamobates (figure 5).The results of the chord diagram show that different agricultural land-use practices affect the diversity composition of the oribatid mite, and also to some extent affect the individual number of oribatid mites in different agricultural land-use.
The community similarity results of oribatid mites in different agricultural land-use types are shown in table 3. The similarity index between CF and GP was the highest (0.462), the similarity index between GP and TF was the lowest (0.354), and the similarity index between the three habitats ranged from 0.354 to 0.462.The similarity of community structure of the three agricultural land-use oribatid mites was medium dissimilarity.
In order to further analyze the similarities and differences of oribatid mite communities among different agricultural land-use, oribatid mites with individual numbers greater than 1% were selected from 9 sample plots of 3 types of agricultural land-use types as raw data for bidirectional clustering analysis (figure 6).The results showed that the community structure of oribatid mites in three types of agricultural land can be divided into two categories (type 1: CF and TF; type 2: GP), indicating significant differences in soil oribatid mite community characteristics between different agricultural land-use.

Ecological groups of oribatid mites in different agricultural land-use
MGP analysis of oribatid mites is a classification method proposed by Aoki for comparing ecological groups among oribatid mite communities in different environments [50].MGP analysis can reflect the impact of human activities on the structure of oribatid mite communities.The ecological group analysis results of oribatid mites in different agricultural land-use are shown in table 4. From the percentage of the genus numbers of the oribatid mite group, CF belongs to the P-type, GP belongs to the MP-type, and TF belongs to the O-type.From the percentage of individual  numbers of mites, CF and GP belong to P-type, while TF belong to GP-type.Therefore, based on the results of MGP -I and MGP -II, the ecological groups of soil oribatid mites in the three types of agricultural land are mainly P-type.

Relationship between the community structure of soil oribatid mites and environmental factors
The 7 physical factors and 6 chemical factors for the 3 types of agricultural land in the study area is shown in table 5. Overall, the contents of TP, AK and SOM were significantly different among different habitats.
The correlation analysis between various parameters of soil oribatid mite community structure and soil factors are shown in figure 7.Among the three types of agricultural land, the family number of soil oribatid mites (F), individual number (I), and individual density (Ind.) were significantly positively correlated with TP (P < 0.01), while the dominance (C) was significantly negatively correlated with TP (P < 0.01).TN is significantly positively correlated with the number of family (F), genus (G), individual number (I), individual density (Ind.), and abundance (SR) of soil oribatid mites.The family number (F), genus number (G), diversity (H′), richness (SR) of soil oribatid mites are highly significantly positively correlated with SH.There is a significant positive correlation between individual number (I), individual density (Ind.), and SH.The individual number (I) and individual density (Ind.) of soil oribatid mites were significantly correlated with ST and AK.The correlation between the structural parameters of other soil oribatid mite communities and environmental factors was not significant (P > 0.05).
To reduce experimental analysis errors, soil oribatid mites with dominance > 1% were selected.After removing rare genera, there were 37 remaining soil oribatid mites (dominant and common groups), and trend correspondence analysis (DCA) was performed on the oribatid mites community.The results showed that the maximum gradient length was 2.0, so RDA was used to analyze the correlation between soil oribatid mite community structure and environmental factors [48].The degree of linear combination between the sorting axis and environmental factors well demonstrates the relationship between species and the environment, and the sorting results are reliable.The first two ranking axes have cumulatively explained 55.85% of the variation in soil oribatid mite community composition, with the explanatory rates of the first and second ranking axes being 35.87% and 19.98%, respectively.The results show that NWC, SWC, and P gradually decrease along the direction of the first sorting axis, and are negatively correlated with the first sorting axis; The second axis has a high correlation with pH value and soil humidity (figure 8).
According to the RDA ranking chart, different soil factors have different effects on the distribution of individual numbers of soil oribatid mites.Among these environmental factors, SWC, NWC, and BD are the main physical environmental factors that affect the distribution of soil oribatid mites; TP, TN, AK, and SOM are the main chemical environmental factors that affect the distribution of soil oribatid mites.Due to the different distribution areas of each sampling square, there are also differences in the community composition of the same type of agricultural land oribatid mites, with the most significant differences among various points in GP, indicating a high heterogeneity of the soil environment in GP.There are differences in the response of soil oribatid mite community structure to soil environmental factors.Among them, in GP, the oribatid mites are mainly positively correlated with ST, E, BD, TN, TP, AK, and SOM, while in CF soil, the oribatid mites are mainly positively correlated with SWC.

Discussion
4.1.Differences in the composition and distribution of soil oribatid mite communities in different agricultural land-use A total of 1220 oribatid mites were captured in the study area, belonging to 41 families and 79 genera.Scheloribates, Oppiella, Scutovertex, Xylobates, and Tectocepheus are the dominant groups of soil oribatid mites, which is similar to the research results of Chen et al [6,23,32,36,51].From the perspective of agricultural land, there are 681 oribatid  This may be because the thick litter layer in GP provides a good habitat environment and food resources for the survival and reproduction of soil oribatid mites, resulting in complex community structure of soil oribatid mites, and the number of individuals and groups and genera is higher than other habitats.Different agricultural land-use will have different impacts on the community structure of soil oribatid mites [52][53][54].Among the three agricultural land-use in the study area, Scheloribates has a large number and wide distribution range, which indicates that they have a strong ability to use space resources.Scheloribates has a strong adaptability to different agricultural land-use in the buffer zone of Shibing Karst World Natural Heritage, showing universality to different microhabitats, it can serve as an indicator species for the farmland ecosystem in the buffer zone.In addition, Tectocepheus, Oppiella, Xylobates, and Scutovertex are the dominant groups of the other two types of agricultural land.Studies have shown that Tectocepheus often exists in early succession and less disturbed environments [23], and it is widely distributed in three types of agricultural land, providing a good indicator for the soil environment in the study area [36].The dominant genera of oribatid mites in different agricultural land soils are different [23].The dominant genera of evergreen broad-leaved forest in Shibing Karst World Natural Heritage are Perscheloribates [34], Ceratozetes and Cosmochthonius in the plain area of Ebinur Lake Basin in Xinjiang are the dominant genera [55], and Oppia and Epicrius [56] in Jilin black soil area, which may be related to differences in the reproductive methods, adaptive mechanisms, and colonization potential of different groups of oribatid mites [57].

Differences in diversity and similarity of soil oribatid mite communities in different agricultural land-use
The higher the community diversity index and richness index, the longer the food chain and more complex food web in the ecosystem, thus enhancing the stability of the community [58].The diversity and richness of GP and  CF in the study area are higher, indicating that the stability of the underground soil oribatid mite community in this agricultural area is good, which may be related to the high content of litter and less human activity interference.During the actual sampling process in the research area, there was less human interference in GP, resulting in more litter, high ground vegetation coverage, and abundant vegetation types; The human interference in CF is relatively large, and after corn harvesting, a portion of the corn leaves often naturally fall off in the field.Therefore, there is a certain amount of litter in CF, and the oribatid mites have 'a food source'; The low diversity of soil mites in TF may be due to the fact that tobacco leaves are harvested as agricultural products after maturity, resulting in less litter in the tobacco field.In addition, human harvesting of tobacco leaves in the tobacco field significantly reduces the food source of mites.Generally speaking, the community diversity of soil oribatid mites is related to vegetation conditions and the diversity of cover plants, and the quantity and quality of their litter may have a decisive impact on the mite community.The diversity and richness of GP are the highest among the three types of agricultural land, indicating that the mite community structure in GP is more stable.The similarity of soil oribatid mite community structure among the three different agriculturals was basically medium dissimilarity.The results of cluster analysis of soil oribatid mite community in farmlands showed that the habitats of TF and CF could be classified into one category, while the habitats of GP were classified into one category alone.Moreover, relevant studies also show that ecological environment has a significant impact on community structure, and the more similar the ecological environment, the more similar the biological communities in it [59], which is consistent with the results of different clustering analysis among the same habitats in this study.

The ecological groups of soil oribatid mites in different agricultural land-use are mainly P-type
Research has shown that in areas with good ecological environments, the oribatid mite community mainly exhibits O-type and P-type [23,60,61], and oribatid mites are ideal biological indicator species for monitoring the ecological environment.Based on the analysis of MGP -I (proportion of group genera) and MGP -II (proportion of individual numbers), the community structure of soil oribatid mites in the study area is mainly P-type.The three types of agricultural land MGP -I in the study area are P-type in CF, MP-type in GP, and O-type in TF; MGP -II is mainly P-type, which is consistent with the research results of Pan [3], Yakup [54] and others.Therefore, the soil environment under the agricultural land type in the buffer zone of the heritage site is relatively stable, and the ecological environment is in good condition.The MP-type of MGP -I in GP may be related to the abundance of group genera in GP.Overall, the comprehensive performance of soil environment in different agricultural land-use is relatively good.

TP, SOM, etc. are soil environmental factors that affect the soil oribatid mite community
There is a close relationship between soil environmental factors and the community structure characteristics of soil oribatid mites.Correlation analysis shows that the 13 environmental factors in the three agricultural underground environments have different impacts on the community composition and individual quantity of oribatid mites.The diversity, richness, and family and genus levels of soil oribatid mites are highly significantly positively correlated with SH, which may be related to the fact that most soil mites are able to adapt to environments with high humidity.The number of genera, individual numbers, and individual density are highly significantly positively correlated with TP.Overall, the community composition of soil oribatid mites is positively correlated with ST, SH, E, BD, TN, TP, and SOM, while negatively correlated with SWC and NWC.Soil temperature and humidity are likely the main limiting factors for soil oribatid mite reproduction [62].
The redundancy analysis of the community structure and environmental factors of soil oribatid mites further indicates that TP has a significant impact on the composition and distribution of soil oribatid mites (P < 0.05).It is possible that an increase in TP content will increase the richness of vegetation species, providing a good living and habitat environment for soil oribatid mites.The RDA results show that ST and E are the main physical environmental factors affecting the structure of the oribatid mite community, while TP, SOM, TN, and AK are the main chemical environmental factors affecting the oribatid mite community structure.Relevant research shows that the soil light intensity within a certain range has an indirect promoting effect on small and medium-sized soil arthropod [63], If the soil moisture is too high, the soil arthropod will die due to lack of oxygen [64].Organic matter is the most important food source for soil oribatid mites, and nitrogen is also an important nutrient element [23,65,66].Therefore, there is a close relationship between soil oribatid mite community structure and soil physical and chemical properties.The combination of the two can reflect the difference in environmental quality.It is of great significance to introduce the analysis of soil oribatid mite community characteristics and soil physical and chemical factors into the monitoring and evaluation of soil in the buffer zone of heritage sites in Karst areas.

Conclusion
The soil oribatid mites in different agricultural land-use in the buffer zone of the Shibing Karst World Natural Heritage are rich and unique.1220 soil oribatid mites were captured in this study, belonging to 41 families and 79 genera.Scheloribates, Oppiella, Tectocepheus, which are the dominant groups of different agricultural landuse, which can be used as bioindicator in the buffer zone of Shibing Karst World Natural Heritage.In different agricultural land-use in the study area, the content of TN, TP, and SOM in the soil is the main factor affecting the characteristics of soil oribatid mite communities in the buffer zone.This study provides data support biodiversity protection and ecological environment monitoring in heritage sites.

7
Environ.Res.Commun.5 (2023) 115019 T Gong et al difference between other habitats (F = 3.431, df = 2, p > 0.05).In terms of individual quantity (figure1), GP has the most abundant individual quantity of oribatid mites, while TF has the rarest individual population, with the order of GP > CF > TF.Among them, there was a significant difference (F = 9.734, df = 2, p < 0.05) between CF and TF and GP, while there was no significant difference (F = 9.734, df = 2, p > 0.05) between the CF and the TF.The trend of individual density changes, as well as the differences in characteristics and the pattern of individual quantity changes, are consistent (figure1), with the highest individual density of oribatid mites in GP and the lowest individual density in TF (GP > CF > TF).It can be seen that the number of families, genera, individual numbers, and individual density of oribatid mites vary with changes in agricultural land.

Figure 1 .
Figure 1.Distribution of the number of families, genera, individuals, and individual density of soil oribatid mites in different agricultural land-use.Figure A shows the distribution of the number of families and genera of oribatid mites, while figure B shows the distribution of individual numbers and density of oribatid mites.

Figure 2 .
Figure 2. Composition of dominant, common, and rare genera of soil oribatid mites in different agricultural land-use.

Figure 3 .
Figure 3. Venn plot and upset diagram of the composition of soil oribatid mite communities in different agricultural land-use.Note: CF: corn field, GP: golden pear garden, TF: tobacco field.The Venn plot represents the composition of soil mite communities; The following is the upset diagram.The individual appearance of a circle indicates the number of unique mites in the cultivated land.The black circle with connecting lines indicates the existence of the same genus between different agricultural land-use, and the bar chart above shows the number of identical genera.

Figure 4 .
Figure 4. Diversity, Species richness, evenness, and dominance index of soil oribatid mites in different agricultural land-use.Note: Different lowercase letters indicate the differences of diversity index, richness index, evenness index and dominance index of soil oribatid mites in different agricultural land-use.

Figure 5 .
Figure 5. String diagram describing the group and number of soil oribatid mites in different agricultural land-use.Note: The width and color of the lines indicate the relationship and intensity between different groups of oribatid mites and different agricultural landuse types.

Figure 6 .
Figure 6.Bidirectional cluster analysis of soil oribatid mites in different agricultural land-use.

Figure 7 .
Figure 7. Correlation between the community structure of soil oribatid mites and environmental factors.
The composition and quantity distribution of oribatid mite communities in three types of agricultural land are shown in table2.352 oribatid mites belonging to 34 families, 52 genera were captured in CF, 681 oribatid mites belonging to 35 families, 62 genera were captured in GP, and 187 oribatid mites belonging to 21 families, 26 genera were captured in TF.It can be seen that among the three types of agricultural land, Gymnonota and Poronota oribatid mites are the majority.The GP has a 3.1.Composition and distribution of soil oribatid mite communities in different agricultural land-useA total of 1220 soil oribatid mites, belonging to 79 genera and 41 families, were captured under 3 types of agricultural land in the study area.There were 179 individuals from 14 families and 29 genera in group M (Macropylina), 307 individuals from 11 families and 19 genera in group G (Gymnonota), and 734 individuals from 31 genera and 16 families in group P (Poronota).relatively rich group and quantity of soil oribatid mites, while CF and TF have a relatively small group and quantity of soil oribatid mites.

Table 1 .
Classification criteria of community types on soil mites (Oribatida).

Table 2 .
Composition and quantitative distribution of soil oribatid mite communities in different agricultural types.

Table 3 .
Similarity of soil oribatid mite communities in different agricultural land-use.

Table 4 .
MGP analysis of soil oribatid mites in different agricultural land-use.

Table 5 .
Content of soil physical and chemical factors.It can be seen that the soil oribatid mites resources in GP are more abundant.In GP, soil oribatid mites have the largest number of species and individuals, and the diversity index is also the highest.