Ecotoxicology (2014) 23:707–717 DOI 10.1007/s10646-014-1186-x

Relationship between land use pattern and the structure and diversity of soil meso–micro arthropod community Limin Zhang • Xueping Zhang • Wei Cui

Accepted: 4 January 2014 / Published online: 28 January 2014 Ó Springer Science+Business Media New York 2014

Abstract Soil arthropod communities can provide valuable information regarding the impacts of human disturbances on ecosystem structure. Our study evaluated the structure, composition and diversity of soil meso–micro arthropod communities, in six different vegetation types and assessed the impacts of human activity. A completely randomized design, including 3 replicates from 6 sites (mowing steppe, natural grassland, severe degradation grassland, farmland, artificial shelter forest, and wetland) was used. Soil samples from the depth of 0 to 20 cm were collected during May, July, and September 2007. Soil meso–micro arthropod were separated using the Tullgren funnels method, and were identified and counted. Soil pH value, organic matter, and total nitrogen were measured in topsoil (0–20 cm) from each site. A total of 5,602 soil meso–micro arthropod individuals were collected, representing 4 classes, 14 orders, and 57 families. Most soil arthropods were widely distributed; however, some species appeared to be influenced by environment variables, and might serve as bioindicators of adverse human impacts. Canonical correspondence analysis indicated the soil arthropod distribution in the severely degraded grassland, mowing steppe, farmland, and shelter forest differed from the natural grassland. Arthropod density and diversity were greatest in May, and the forestland community was the most

L. Zhang  X. Zhang (&) Key Laboratory of Remote Sensing Monitoring of Geographic Environment, College of Heilongjiang Province, Harbin Normal University, Harbin 150025, People’s Republic of China e-mail: [email protected] W. Cui State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, People’s Republic of China

stable. Because of the vital role soil arthropods have in maintaining a healthy ecosystem, mechanisms to maintain their abundance and diversity should be further evaluated. Keywords Impacts of human activity  Soil fauna  Biodiversity  Seasonal dynamics  Meadow steppe

Introduction In the past century, research of ecology mainly focused on the aboveground components of ecosystems. Nowadays, ecologists is realizing increasingly that the underground components of ecosystems, as we do not know much about them, is the most uncertain factor in the research of the structure, function and process of the whole ecosystem. Thus, lack of knowledge about them dramatically limits the development of theoretical research on ecosystem and its global change (Wall et al. 2008; Rouifed et al. 2010; Barrett et al. 2008; Butler et al. 2008). Today, based on the rapid developing soil fauna taxonomy, research on diversity and function of soil fauna is brought to the forefront (Wall et al. 2010; Heemsbergen et al. 2004; Dı´az et al. 2009). Constitution and structure of soil arthropod communities are highly sensitive to environmental variation and destabilization. Thus, they are reliable indicator to reflect variation of environment and basic condition of ecosystem (Van Straalen 1997). In recent years, research on using soil fauna as bioindicator of soil environment has become an international hotpot and forefront of soil ecol˚ slund et al. 2012; Lin et al. ogy (Shen et al. 2006; 2012; A _ 2012; Beaudouin et al. 2012; Zmudzki and Laskowski 2012; Jubileus et al. 2013), however, it is currently hard to draw any definite conclusion about how does the variation

123

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of diversity of soil fauna impact on function of ecosystem because of limited research methods and technology. Long term experiments are still needed to evaluate the stability of both biodiversity and function of ecosystem. Vegetation is one of the indispensable means of subsistence for most soil fauna, because litterfall and root exudates influence the quality and quantity of their food as well as their habitat (Hooper et al. 2000; Wardle et al. 2004). Due to human activities, huge area of nature vegetation has been changed into farmland and pasture, and thus, components and coverage of vegetation have also varied accordingly. Community structure, population and diversity of soil fauna living in these areas have also been changed dramatically. Daqing Meadow Steppe, locating on the fertile black soil region of Songnen plain in Northeast China, is an important agricultural and stock raising base with high productivity. Meanwhile it is also a region with the characteristics of great land-use change. Zang et al. (2005) have found that the cultivated land and forest land increase continuously, but the grassland and wetland decrease dramatically in the field. For a long time, the over-exploitation of water, soil and biological resources, has already destroyed the balance of ecosystem and turned this region a typical ecological fragile zone. In this study, we investigated the structure and diversity of soil meso–micro arthropod communities in several areas with various vegetation types and land use patterns, including grassland, farmland, shelter forest and wet land in Daqing Meadow Steppe. The current study evaluates the impact of human activities on soil fauna population and community structure in Daqing Meadow Steppe of Heilongjiang Province. These data will be useful in understanding the characteristics and functions of soil fauna in meadow steppe, and in future study and management of the evaluated ecosystem.

Materials and methods Description of study area The study was conducted at the meadow steppe in Daqing (124°E, 46°N) in the northeast of Song-Nen plain, which is characterized as having a temperate continental monsoon climate with long cold winters and moderately short warm summers. The annual precipitation is 442.6 mm and the mean annual temperature is 3.7 °C (monthly extremes -18.5 and 23.3 °C). The average annual sunshine duration is 2,726 h. The soil at the study site is classified as chernozem and the typical vegetation is the meadow steppe, Leymus chinensis is the main plant population (Wang and Zang 2007).

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L. Zhang et al.

Field sampling The experimental design was completely randomized block design, involving 6 sites with 3 replicates. Six sites were selected based on various vegetation coverage and land use patterns [A (Mowing steppe with 90 % herb coverage), B (Natural grassland with 70 % herb coverage), C (Severely deteriorated grassland with 50 % herb coverage), D (Farmland with 10 % herb coverage), E (Artificial shelter forest with 70 % herb coverage) and F (Wetland with 95 % herb coverage)]. During May, July and September in 2007, three locations were random chosen in each of the six sites. Four 10 9 10 cm2 samples were collected form each location at 0–20 cm depth. Samples collected from the same location were mixed thoroughly and preserved in a plastic bag. Soil meso–micro arthropod were separated using the Tullgren funnels method and preserved in 70 % ethanol (Macfadyen 1953). Collected arthropods were counted and identified under a microscope using the Pictorial Keys to Soil Animals of China (Yin 1998). Soil chemical and physical properties were measured in approximately 1 kg of soil collected from a depth of 0 to 20 cm at each site. Samples were air-dried at room temperature and then sieved through a 2 mm screen. Soil pH was determined with a glass electrode in 1:2.5 soil:water solution (w/v). Total nitrogen (TN) was measured using the Kjeldahl method; Soil organic matter content (OM) was analyzed using the potassium dichromate volumetric method (outside heating method) (Lu 2000). Data analysis Several biological categories were selected to evaluate community indices including: Shannon–Weiner index of diversity (H0 ) (Shannon and Weaver 1949): X H0 ¼  PilnPi ð1Þ Pieluo evenness quantity (E) (Pieluo 1996): E ¼ H0 =lnS

ð2Þ

Simpson dominance index (C) (Simpson 1949): X C= Pi2

ð3Þ

Margalef abundance index (R) (Margalef 1958): R ¼ ðS  1Þ=lnN

ð4Þ

The density-group index (DG) (Liao et al. 1997) X DG ¼ ðDi=DimaxÞ  ðD=GTÞ

ð5Þ

Soil meso–micro arthropod community

where Pi is the abundance rate of the number of i species; S is the total number of species; N is the total number of individuals; Di is the density of the number of i group; Dimax is the largest density of the number i group in each community; D is the number of groups and GT is the total number of groups in each community. Soil meso–micro arthropod abundance was ln(X ? 1) transformed before analysis to normalize the data and make the variance constant. One-way ANOVA was used to evaluate the effects of land use on measured ecological indices. Principal component analysis was used to evaluate all soil arthropod community structure parameters. Canonical correspondence analysis (CCA) was used to evaluate species richness and main chemical properties under different land use types. All statistical analyses were performed with SPSS and CANOCO software packages, and differences with p \ 0.05 were considered statistically significant.

709

in the wetland (3.7 %) and farmland (2.55 %), and it was a rare group (0.27–0.59 %) in the artificial shelter forest, mowing steppe, and natural grassland, while it was not collected in severely deteriorated grassland. Sminthuridae was a common group (1.36 %) in the natural grassland, but it was a rare group in all the other five communities (0.07–0.63 %). Moreover, each of the six sites had its own unique group (Table 1). The individual density of the soil meso–micro arthropod communities were significant difference (p \ 0.05) among the six sites (Table 2). The mowing steppe had the highest individual density (8,483 ind m-2), which was three times greater than the severely deteriorated grassland (2,828 ind m-2), the community with the lowest density. The density of some meso–micro arthropods changed only slightly among sites; for example, Scarabaeoidea (CV = 34.74 %). On the contrary, some species changed dramatically. For example, the individual density of Pentatomidae was 689 ind m-2 in the natural grassland, but it was only 17 ind m-2 in the wetland (CV = 133.9 %) (Table 1).

Results Constitution and structure of soil meso–micro arthropod communities In this study, 5,602 meso–micro arthropods were collected which belonged to 4 classes, 14 orders, and 57 families. The population density averaged 5,187 individuals per square meter (ind m-2). There were three dominant species (which counted [10 % of total): Oribatida, Onychiuridae, and Prostigmata, counting for 65.48 % of the total individuals. And 26.49 % of the meso–micro arthropods were made up of 7 common groups (which counted 1 to 10 % of total): Formicidae, Isotomidae, Pentatomidae, Entomobryidae, Poduridae, Mesostigmata, and Staphylinidae, while 47 rare groups (which counted \1 %) counted only 8.03 %. Thus, it was obvious that the dominant species and the common groups made up the majority of the meso– micro arthropods in the Daqing Meadow steppe. There were 30 groups of soil meso–micro arthropods in the natural grassland (B) (Table 1) and the number of groups in the natural grassland had no significant difference with other sites which were affected by human activities (p [ 0.05) (Table 2). There were a total of 14 groups in the six sites. Oribatida was the dominant species and counted [20 % of total individuals in each of the six sites. Prostigmata, Isotomidae and Onychiuridae ranged form 2.97–18.21, 2.72–10.09 and 5.29–27.44 %, respectively in each of the six sites. Relative abundance of the same group varied significantly among the six sites. Oribatida of the farmland had the highest relative abundance in six sites (62.23 %). Chironomidae was a common group

Canonical correspondence analysis for soil meso–micro arthropod communities As canonical correspondence analysis (CCA) of the abundance of the meso–micro arthropods and the date for environmental variables including pH, NT, OM, and the rate of coverage of vegetation in six sites indicated the eigenvalues of the first axis and the second axis were 0.122 and 0.098. The species-environment correlations were 0.903 for axis 1 and 0.817 for axis 2. The first axis, which reflected NT of the soil, and the second axis, which reflected pH, OM, and Coverage, could be illustrated by the measured environmental variables. This figure revealed the relation between the distribution of species and the environment (Fig. 1). On the whole, most soil meso–micro arthropods distributed widely and were positioned in the center of the diagram, for example Oribatida and Onychiuridae. Arthropod species such as Pentatomidae, Scaphidiidae, Carabidae and Onychiuridae mainly appeared in areas with high Nitrogen. Some others, such as Scydmaenidae, Phlaeothripidae, Entomobryidae, Staphylinidae and Poduridae mainly appeared in areas with high pH, OM, and vegetation coverage. Distribution of soil meso–micro arthropods varied in the six sites. Mowing steppe, severely deteriorated grassland, farmland, and shelter forest had different arthropod distribution from natural grassland and wetland. The relative abundance of species also differed in the six sites. Some of them, such as Entomobryidae, Poduridae, Dolichopodidae and Chironomidae, had similar relative abundance in every site, while some others mainly lived in one site. For

123

123

0

Culicidae

0

0

0

6

6

0

Microphysidae

Cydnidae

Ceratocombidae

Schizopteridae

Lygaeidae

Veliidae

928

856

56

133

6

83

Onychiuridae

Isotomidae

Entomobryidae

Poduridae

Sminthuridae

Pseudachorutidae

Collembola

528

Pentatomidae

Hemiptera

0

0

Xylophagidae

Hesperinidae

6

Phoridae

0

0

Ceroplatidae

0

0

Therevidae

Tipulidae

11

Sciaridae

Hyperoscelididae

0

Rhagionidae

0

6

Empididae

6

39

Dolichopodidae

Trichoceridae

50

Tabanidae

33

Geratopogonidae

0.98

0.07

1.57

0.65

10.09

10.94

0

0.07

0.07

0

0

0

6.22

0

0

0

0

0.07

0

0

0.07

0

0

0.13

0

0.07

0.46

0.59

0.39

17

89

117

294

178

1,794

6

0

0

0

0

0

689

0

0

0

6

0

0

0

0

0

0

6

33

6

50

17

39

Density (ind m-2)

Density (ind m-2)

Relative abundance (%)

Station B

Station A

Chironomidae

Diptera

Groups

0.25

1.36

1.78

4.5

2.72

27.44

0.08

0

0

0

0

0

10.54

0

0

0

0.08

0

0

0

0

0

0

0.08

0.51

0.08

0.76

0.25

0.59

Relative abundance (%)

0

11

22

11

194

572

0

0

0

0

0

0

28

6

0

0

0

0

0

0

0

0

0

0

0

11

17

6

0

Density (ind m-2)

Station C

0

0.39

0.79

0.39

6.88

20.24

0

0

0

0

0

0

0.98

0.2

0

0

0

0

0

0

0

0

0

0

0

0.39

0.59

0.2

0

Relative abundance (%)

22

17

44

28

311

294

0

0

0

6

0

11

33

0

0

0

0

0

0

6

11

0

0

11

0

6

22

11

100

Density (ind m-2)

Station D

0.57

0.42

1.13

0.71

7.92

7.5

0

0

0

0.14

0

0.28

0.85

0

0

0

0

0

0

0.14

0.28

0

0

0.28

0

0.14

0.57

0.28

2.55

Relative abundance (%)

28

39

78

111

339

789

0

0

0

0

6

6

61

0

0

0

0

0

0

0

0

0

0

0

0

17

56

67

17

Density (ind m-2)

Station E

0.45

0.63

1.26

1.79

5.47

12.74

0

0

0

0

0.09

0.09

0.99

0

0

0

0

0

0

0

0

0

0

0

0

0.27

0.9

1.08

0.27

Relative abundance (%)

0

17

228

250

311

167

0

0

0

0

0

0

17

0

6

6

0

0

6

6

0

17

17

0

0

0

100

133

117

Density (ind m-2)

Station F

0

0.53

7.23

7.94

9.88

5.29

0

0

0

0

0

0

0.53

0

0.18

0.18

0

0

0.18

0.18

0

0.53

0.53

0

0

0

3.17

4.23

3.7

Relative abundance (%)

25

30

104

125

365

757

1

1

1

1

1

3

226

1

1

1

1

1

1

2

3

3

3

5

6

7

47

47

51

Density (ind m-2)

Total

0.48

0.57

2.00

2.41

7.03

14.6

0.02

0.02

0.02

0.02

0.02

0.05

4.36

0.02

0.02

0.02

0.02

0.02

0.02

0.04

0.05

0.05

0.05

0.09

0.11

0.14

0.91

0.91

0.98

Relative abundance (%)

105.25

105.18

71.21

95.85

68.39

77.06

47.14

133.19

0

47.14

34.64

55.9

63.46

102.76

72.44

CV (%)

Table 1 Composition and quantitative distribution of soil meso–micro arthropods in different soil collected from six different environmental study sites, Daqing Meadow Steppe, China during 2007

710 L. Zhang et al.

0

0

Geophilomorpha

3,378

0

6

Noctuidae

Notodontidae

Prostigmata

0

Curculionidae

Cantharidae

Phlaeothripidae

Araneida

17

0

0

Jassidae

Thysanoptera

11

Cicadidae

Homoptera

0

0

Elateridae

0

0

Throscidae

Lucanidae

0

Scydmaenidae

0

11

Scarabaeoidea

0

0

Scaphidiidae

Cicindelidae

33

Carabidae

Silphidae

67

Staphylinidae

Coleoptera

356

1,517

Formicidae

Hymenoptera

6

Hepialidae

Lepidoptera

0.2

0

0

0.13

0

0

0

0

0

0

0

0

0.13

0

0.39

0.79

17.88

4.19

0.07

0

0.07

39.82

0

Oribatida

0

0

Blattidae

0

0

0

0

Diplopteridae

Blattaria

0

Hypogastruridae

6

56

0

6

0

0

6

0

0

6

0

0

17

61

133

111

194

794

0

0

6

1,783

0

0

0

0

6

Density (ind m-2)

Density (ind m-2)

Relative abundance (%)

Station B

Station A

Oncopoduridae

Groups

Table 1 continued

0.08

0.85

0

0.08

0

0

0.08

0

0

0.08

0

0

0.25

0.93

2.04

1.7

2.97

12.15

0

0

0.08

27.27

0

0

0

0

0.08

Relative abundance (%)

0

22

0

0

6

6

0

0

6

0

6

0

6

0

72

67

200

122

0

0

0

1,344

6

6

0

6

11

Density (ind m-2)

Station C

0

0.79

0

0

0.2

0.2

0

0

0.2

0

0.2

0

0.2

0

2.55

2.36

7.07

4.32

0

0

0

47.54

0.2

0.2

0

0.2

0.39

Relative abundance (%)

28

6

6

0

0

0

0

6

0

0

11

11

17

22

33

39

150

94

0

0

6

2,444

0

0

11

6

0

Density (ind m-2)

Station D

0.71

0.14

0.14

0

0

0

0

0.14

0

0

0.28

0.28

0.42

0.57

0.85

0.99

3.82

2.4

0

0

0.14

62.23

0

0

0.28

0.14

0

Relative abundance (%)

6

6

0

11

0

0

0

0

0

0

0

0

11

0

6

17

1,128

894

0

0

0

2,422

0

6

0

33

39

Density (ind m-2)

Station E

0.09

0.09

0

0.18

0

0

0

0

0

0

0

0

0.18

0

0.09

0.27

18.21

14.44

0

0

0

39.1

0

0.09

0

0.54

0.63

Relative abundance (%)

6

61

11

6

0

0

0

0

6

6

0

22

11

11

28

150

494

33

0

6

0

778

0

0

0

33

39

Density (ind m-2)

Station F

0.18

1.94

0.35

0.18

0

0

0

0

0.18

0.18

0

0.71

0.35

0.35

0.88

4.76

15.7

1.06

0

0.18

0

24.69

0

0

0

1.06

1.23

Relative abundance (%)

10

25

3

6

1

1

1

1

2

2

3

6

12

16

51

75

614

382

1

1

3

2,025

1

2

2

13

16

Density (ind m-2)

Total

0.2

0.48

0.05

0.11

0.02

0.02

0.02

0.02

0.04

0.04

0.05

0.11

0.23

0.3

0.98

1.45

11.84

7.37

0.02

0.02

0.05

39.04

0.02

0.04

0.04

0.25

0.3

Relative abundance (%)

81.31

89.39

47.14

38.49

0

0

47.14

34.74

83.4

89.8

64.7

93.74

98.2

0

45.48

0

82.48

75.33

CV (%)

Soil meso–micro arthropod community 711

123

L. Zhang et al. 11.35

1.87

33

Time as the control variables (df = 2)

F

p

F

p

S

0.258

NS

13.952

p \ 0.001

D

5.622

0.007

0.842

NS

H0

2.697

NS

2.494

NS

R

0.645

NS

10.258

0.002

E

4.599

0.014

0.971

NS

C DG

3.725 0.789

0.029 NS

1.003 5.711

NS 0.014

1.0

Entom

Scap

Coverage OM Podu

Stap

Axis 2

Scyd

Phla

Rhag

Values with different alphabetic super scripts were statistically different (p \ 0.05) (make a b c super scripts)

Study sites: A mowing steppe, B natural grassland, C seriously degraded grassland, D farmland, E artificial shelter forest, F wetland

pH B

Coefficient of variation (CV) = standard deviation/mean 9 100 %

26 33 26 30 27 Total number of species

F

Smin Cara Pent

Scar

Onyc Form

NT

Gera Onco Hypo

Cica Isot Pros Meso Aran

Orib Pseu Empi A

C

Chir

Doli

D E

-0.6

97

5,187

1.76 56

3,150b

0.09 6

6,194 ab

2.69 106

3,928b

2.36 67

2,828b

0.25 6,539ab

17 333 Mesostigmata

Site as the control variables (df = 5)

Structure parameters: S the number of species, D the density of individuals, H0 Shannon–Weaner index, R Margalef index, E Pieluo index, C Simpson index, DG density-group index, NS not significant (p [ 0.05)

8,483a

3.93

123

Table 2 Results of one-way ANOVA evaluating soil meso–micro arthropod community structure parameters (n = 54) in six different environmental study sites, Daqing Meadow Steppe, China during 2007 Parameter

Total Density (ind m-2)

Density (ind m-2) Density (ind m-2) Density (ind m-2) Density (ind m-2) Density (ind m-2) Density (ind m-2) Relative abundance (%) Density (ind m-2)

Groups

Table 1 continued

Station A

Station B

Relative abundance (%)

Station C

Relative abundance (%)

Station D

Relative abundance (%)

Station E

Relative abundance (%)

Station F

Relative abundance (%)

Total

Relative abundance (%)

CV (%)

124.61

712

-1.0

1.0

Axis 1

Fig. 1 Canonical correspondence analysis (CCA) diagram for soil meso–micro arthropods in different soil collected from six different environmental study sites, Daqing Meadow Steppe, China during 2007 (only species with the relative abundance [0.1 % are included). The soil arthropods names were abbreviated to first four letters of their full name, for example: Pent-Pentatomidae, the rest genera see Table 1. Study sites: A mowing steppe, B natural grassland, C seriously degraded grassland, D farmland, E artificial shelter forest, F wetland. Environmental factors: NT soil total nitrogen content, OM soil organic matter content, coverage-vegetation coverage

example, Rhagionidae mainly lived in the natural grassland and there were dramatically more Scydmaenidae living in the wetland than in other communities (Fig. 1). Diversity of the structure of the soil meso–micro arthropod communities One-Way ANOVA was used to analyze the index of diversity of soil meso–micro arthropods. The C index and

Soil meso–micro arthropod community

80

decrease / increase (%)

60

A C D E F CV

100 60 40

50 40

20

30

0 -20

CV (%)

120

713

20

-40 -60

10

-80 -100

0 R

H

E

C

DG

G

Diversity indices

Fig. 2 Increase or decrease percentage (%) of diversity indices of soil meso–micro arthropod in mowing grassland (A), seriously degraded grassland (C), farmland (D), artificial shelter forestland (E), and wetland (F) comparing to natural grassland and coefficient of variation of diversity indices in Daqing Meadow Steppe, China during

.8 .6

S DG R

D

C

f 2 (29.29%)

.4 .2 0.0 -.2

H

-.4 -.6

E

-.8 -1.0 -.8

-.6 -.4 -.2 0.0 .2

.4

.6

.8

1.0 1.2

f1 (50.95%)

Fig. 3 Loading plots of principal component analysis for all soil meso–micro arthropod community structure parameters. Structure parameters: S the number of species, D the density of individuals, H0 Shannon–Weaner index, R Margalef index, E Pieluo index, C Simpson index, DG density-group index

Table 3 Component score coefficient of soil meso–micro arthropod community structure parameters in six different environmental study sites, Daqing Meadow Steppe, China during 2007 S

H0

R

E

C

DG

D

f1

-0.09

0.30

-0.07

0.38

-0.37

0.02

-0.01

f2

0.42

0.07

0.48

-0.11

0.11

0.17

-0.16

2007. Structure parameters: S the number of species, D the density of individuals, H0 Shannon–Weaner index, R Margalef index, E Pieluo index, C Simpson index, DG density-group index, G comprehensively index. Coefficient of variation (CV) = standard deviation/ mean 9 100 %

indicated that C index and H0 index were consistent for evaluating diversity of the communities. Among all three grasslands, natural grassland had the highest value in all indices except the C index. The extent of variation of indices differed among the sites. The DG index coefficient of variation was highest (54.57 %), while that of the E index was lowest (15.44 %) (Fig. 2). The principal component analysis of the diversity index indicated that the first principal component (f1) accounted for 50.95 % and the second principal component (f2) 29.29 % of variance. The two principal components accounted for most of the total variance (80.24 %) (Fig. 3). The ordination diagram (Fig. 3) based on the loading plots of PCA for all soil meso–micro arthropod community structure parameters indicated that the H0 and the C indexes had very high loading on f1, so f1 mainly explained the two factors and f2 mainly explained the E and S indexes. According to the component score coefficient of the soil meso–micro arthropod community structure parameters (Table 3), G index, which indicated the diversity of the communities comprehensively, was calculated. The G index was highest in wetland, followed by natural grassland, farmland, shelter forest, mowing steppe, and lastly, severely deteriorated grassland. This regular pattern was similar to that of the H0 index, as illustrated in Fig. 2.

Structure parameters: S the number of species, D the density of individuals, H0 Shannon–Weaner index, R Margalef index, E Pieluo index, C Simpson index, DG density-group index

Seasonal variation of soil meso–micro arthropod communities

E index of soil meso–micro arthropod community were significantly different (p \ 0.05), while other indices had no significant difference among the six sites (p [ 0.05) (Table 2). The H0 index and E index were highest in wetland and lowest in farmland contrary to the C index. This

Significant differences among the sampling seasons were observed in the number of groups of soil meso–micro arthropod communities (p \ 0.001), but there were no significant differences in the density of soil meso–micro arthropod (p [ 0.05) (Table 2). The number of groups reached its maximum in May and its minimum in

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July

S

100

100

D

150

Sep

80

80

CV

100

100 60 60

50

50 40

0

40

-50

20

-50

0

-100

-100 A

B

C

D

E

0

20 0

A

F Total

CV (%)

decrease / increase (%)

150

B

C

D

E

F Total

Site

Fig. 4 Increase or decrease percentage (%) of the group (S) and the density (D) of soil meso–micro arthropod in July and September comparing to May and coefficient of variation (CV) in different soil collected from six different environmental study sites, Daqing

4

5 7 9 SE CV

60

a

50

b 40

3

c

30

2

a

a

1

20

b

0

CV (100%)

5

10 0

H

R

E

C

DG

Diversity indices

Fig. 5 Seasonal variation and coefficient of variation (CV) of diversity indices of soil meso–micro arthropods in different soil collected from six different environmental study sites, Daqing Meadow Steppe, China during 2007. Diversity indices: H0 Shannon–Weaner index, R Margalef index, E Pieluo index, C Simpson index, DG density-group index. Coefficient of variation (CV) = standard deviation/mean 9 100 %. Values with different alphabetic super scripts were statistically different (p \ 0.05) (make a b c super scripts)

September at all sites except for the shelter forest and wetland sites. The groups coefficient of variation among seasons was maximum in the farmland (CV = 35 %) and the minimum in the shelter forestry (CV = 12.74 %) (Fig. 4). In general, the density of individuals reached its maximum in July and minimum in September. The variation patterns of the individual density in different sites were different. The density in mowing steppe and nature grassland decreased over time; however, the density of other sites had a single peak in July. The coefficient of variation among seasons was the maximum in wetland (CV = 47 %), and minimum in shelter forest (CV = 4.59 %) (Fig. 4).

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Meadow Steppe, China during 2007. Study sites: A mowing steppe, B natural grassland, C seriously degraded grassland, D farmland, E artificial shelter forest, F wetland. Coefficient of variation (CV) = standard deviation/mean 9 100 %

The seasonal variation of individual density differed by meso–micro arthropod family. The density of Chironomidae, Geratopogonidae, Araneida, and Empididae decreased from May to September. The density of Scaphidiidae, Scydmaenidae, and Cicadidae reached its maximum in July, while Rhagionidae was only found in September (data not listed). Seasonal variation of the R index and DG index was significant (p \ 0.001), while that of other indices were not (p [ 0.05) (Table 2). H0 , R and DG indexes decreased as with time, and the extent of variation of the DG index was more significant (CV = 54.57 %) than that of other indices (Fig. 5).

Discussion Human activities’ impact on features of soil meso– micro arthropod communities The current study evaluated soil meso–micro arthropod communities in the Daqing Meadow Steppe and indicated that most soil meso–micro arthropods are distributed widely and that Acarina, Collembola and Hymenoptera were usually the dominant or common groups in the communities (Table 1). These results are similar to those reported by Zhang and Zhang (2007) in Harbin, China and Zhu et al. (2010) in Hebei Province, China, both in temperate region, as well as, Kardol et al. (2011) in a subtropical forest in Tennessee, USA and Illig et al. (2010) in a tropical montane rainforest. Thus it can be concluded that Acarina, Collembola, and Hymenoptera have broad ecological amplitude and a strong adaptability to adapt in different environments. Meanwhile, some species were not

Soil meso–micro arthropod community

adaptable to different environments (Fig. 1), and lived only in specific heterogeneitic environments. This suggests that the limited adaptability groups of soil meso–micro arthropods can reflect the differences between environments and could be an important indicator to reflect variations in environments (Andrea 1998; Zhu et al. 2010). As there were many kinds of soil meso–micro arthropods and their distributions were very complicated, additional long-term investigations are needed to clarify their use as environmental indicators. Changing land use pattern can induce dramatic changes in vegetation and physical and chemical features of the soil, and thus greatly impact soil meso–micro arthropod community structure. In the current study, mowing and livestock grazing were primary factors inhibiting soil meso–micro arthropod succession in the three grassland biosystem. The Leymus chinensis steppe community was greatly degenerated because of the destructive depasturing activities in the severely deteriorated grassland. Because the vegetation coverage in this area was very low, the groups, density, and diversity of soil meso–micro arthropods, were also lowest of the six sites studied. Though the mowing steppe had high vegetation coverage and good soil conditions, this community lacked litter fall because of mowing. This resulted in reduced food resources for the soil arthropods, thus lower diversity (Table 1; Fig. 2). The wetland had a sufficient source of water, both rich terrestrial and aquatic plants, abundant vegetation coverage, dramatic heterogeneity of environments, and greater diversity of ecological niche differentiation, which provided enough food resources for soil arthropod communities in different trophic levels and produced richer groups and higher diversity (Fig. 2). Soil meso–micro arthropods in the farmland community had the strongest aggregation, with a high C index and low E index. The soil food web was stressed in this community mainly because of cultivation and other artificial disturbances. The results also indicated that groups and the diversity of soil meso–micro arthropods in the shelter forest sites were both lower than that of the grassland. These results differ from previously reported studies which showed that the forest zone had more groups and individuals, better distribution, and higher diversity than grassland ecosystem (Zhu et al. 2010). The differences were primarily due to the forest site in the current study being an artificial shelter forest. When choosing an area for this kind of forest, soil condition is usually not a prior aspect for consideration. Instead, traffic and administrative area boundaries are the most significant aspects. So the soil condition of the shelter forest is often worse than that of natural forestland. And the artificial shelter forest is also affected by human activities such as grazing, farming, and trampling, which results in lower vegetation coverage than natural forest and

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economic forest. Therefore, the diversity index of the soil meso–micro arthropods was low at the shelter forest site. According to CCA sorting, the distribution of soil meso– micro arthropods in the mowing steppe, severely deteriorated grassland, farmland, and shelter forest were different from that of the natural grassland (Fig. 1). This was apparently related to the fact that they were all affected by human activities. Land use changes disturb environmental processes which are closely related to soil meso–micro arthropod community, such as the variation of food resource, nutrient flow, and catabolic pathway (Norton and Niblack 1991), resulting in a decrease in several grassland species of soil arthropod. Seasonal variation of meso–micro arthropod communities The current study indicated that the density, arthropod groups, and diversity index of the meso–micro arthropod communities in Daqing Meadow Steppe varied dramatically in different seasons. The groups reached their maximum in May and the diversity decreased over time (Figs. 4, 5). This is because spring is the breeding season for most insects, thus the diversity and the groups of soil arthropods reached their peak in spring and as time passed, they are exposed to stress from predators and competitors and their diversity decreases. The density of the soil meso– micro arthropods reached its maximum in July (Fig. 4). The reason was that the water content was the limited factor in the grassland ecosystems. The rainfall in the Daqing Meadow Steppe increased from April to August. It reached a peak in July and decreased in the fall. Meanwhile, the grassland soil had poor water holding capacity, thus the soil water content of the grassland dropped sharply in September. The dominant species in the Daqing Meadow Grassland was Oribatida, which was well adapted to moist environment (Nielsen et al. 2010). So, the population of Oribatida increased dramatically in July (data not listed). This resulted in the increase of soil arthropods as a whole. Since forests have a capacity to maintain a constant environment, in the six study sites, the groups and density of soil meso–micro arthropods in the forest varied with a narrow spectrum in different seasons and this created a relatively stable community structure. On the contrary, the farmland was affected by human activities and the wetland by seasonal water fluctuations, thus these two sites had significant variations in groups and density of soil arthropods communities. According to the dynamic balancing theory in ecological stoichiometry, a feedback mechanism between community structure and environmental factors is indispensible in keeping the system in a generally stable state (Kooijman 1995). Similar mechanisms have been reported for

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microorganism. Climate warming induced change in the physiology and growth of some specific groups within soil microbial communities that maintained relative high stability in conjunction with global warming (Panikov 1999). Yu et al. (2010) studied the grassland ecosystem of Inner Mongolia, China and reported that the function and stability of the ecosystem was positively correlated with its dynamic balance. The biomass of homoeostatic species was higher and more stable than other species and ecosystems dominated by homoeostatic species were more productive and stable. Additional study is needed to determine whether there is also a dynamic balancing mechanism in the seasonal variation of structure of soil meso–micro arthropods communities, which were very sensitive in the studied ecosystems of the current study.

Conclusion Human activities had a great impact on the structure and diversity of the meso–micro arthropod communities in the Daqing Meadow Steppe. Areas impacted by human activities, such as the mowing steppe, severely deteriorated grassland, farmland, and the shelter forest had similar distribution of soil meso–micro arthropods and their diversity indexes were lower than that of the natural grassland. Severely deteriorated grassland, which was most serious affected by human activities, had the lowest vegetation coverage among the six sites studied, and it had the least number of groups, density, and diversity of soil arthropods. In contrast, the wetland ecosystem had an abundant water supply, high vegetation coverage, and high groups and diversity index of soil fauna. The structure and diversity of the soil meso–micro arthropods communities varied dramatically according to season variation. Groups and diversity index were highest in May and the density reached its maximum in July. The structure of the community in the forest was the most stable among the six sites studied because of the forest ability to maintain relatively constant environmental conditions. The farmland was affected by human farming activities and wetland by seasonal hydroperiod. The groups and density of soil arthropods in these two sites varied dramatically with the variation of seasons. The current study demonstrates that different land use types differ tremendously in terms of their effects on the seasonal and spatial distribution of soil meso–micro arthropods. Soil meso–micro arthropods analyze was an effective method for interpreting the soil ecological processes under different land uses. Acknowledgments The project was financially supported by the National Natural Science Foundation of China (Nos. 41101048;

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L. Zhang et al. 41371072), the Postdoctoral Science Foundation of China (No. 2013M541407), the Postdoctoral Science Foundation of Heilongjiang Province, Municipal Science Foundation of Harbin (No. 2011RFXXN039) and Program for the Science and Technology Innovation Team in Universities and Colleges of Heilongjiang Province. Conflict of interest of interest.

The authors declare that they have no conflict

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Relationship between land use pattern and the structure and diversity of soil meso-micro arthropod community.

Soil arthropod communities can provide valuable information regarding the impacts of human disturbances on ecosystem structure. Our study evaluated th...
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