Geoderma 363 (2020) 114144

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Geoderma

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A preliminary investigation of the effect of ( unispina T Saussure; : Gryllotalpidae) activity on soil evaporation in semiarid Loess Plateau of northwest China ⁎ Xi Yanga,b, Ming'an Shaoa,b,c,d, Tongchuan Lia,c, , Yuhua Jiae, Xiaoxu Jiac, Laiming Huangc a State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling 712100, China b College of Natural Resources and Environment, Northwest A & F University, Yangling, Shaanxi 712100, China c Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China d College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China e College of Water Conservancy, Shenyang Agricultural University, Shenyang 110866, China

ARTICLE INFO ABSTRACT

Handling Editor: Yvan Capowiez Many species, especially soil-inhabiting ones, greatly affect the physical and chemical properties of soil. The Keywords: widespread soil-inhabiting mole cricket on the northern Loess Plateau creates subterranean tunnels, damages Soil-inhabiting topsoil structures, and likely alters soil infiltration, erosion, and evaporation. In this study, we assessed the effectof Disturbance adult and immature mole crickets (Gryllotalpa unispina Saussure; Orthoptera: Gryllotalpidae) on soil water eva- Subterranean tunnels poration in loam soil. A series of simulation experiments was conducted in iron buckets (20 cm in diameter and Soil water 20 cm high) filled with disturbed soil at the Shenmu Erosion and Environment Research Station. Thesoilwas saturated and drained until the water content approached the field moisture capacity (25.3%), and then the soil was subjected to evaporation for 58 days. Evaporation was found to occur in two stages. In the first 18 days, daily evaporation in soil with adult and immature mole crickets was significantly (P < 0.05) lower than that in soil without mole cricket. Compared with bare soil treatment, the cumulative evaporation of soil treated with adult and immature mole crickets decreased by 24.6% and 13.9%, respectively. In the second stage, daily evaporation in soil treated with mole cricket was greater than that in bare soil due to the higher soil moisture in treatments with mole cricket in the first stage. Under the condition of continuous drought, mole cricket activity had a lag effectonsoil water evaporation. The effects of mole cricket activity on soil evaporation depended on the soil-surface disturbance area, i.e., a larger disturbance area corresponded to more greatly reduced soil-evaporation function. These results can help elucidate the effects of soil-inhabiting insects on water movement in semiarid areas.

1. Introduction forming macropores with a diameter of 1–14 mm (Bastardie et al., 2003) and accumulating water-stable aggregates on the soil surface, thereby In 1999, the policy of returning farmland to forests and grassland changing soil bulk density (Tucker et al., 2004) and reducing surface was implemented. Since then, the vegetation coverage of the Loess runoff and soil erosion by increasing water infiltration and roughness Plateau in northwest China has increased from 6.5% in the 1970s to (Blanchart et al, 2004; Evans et al., 2011; Jouquet et al., 2012). As around 50% in 2010 (Wang et al., 2012) and reached 60.2% by the end ecosystem engineers, social ants can form continuous macroporous tun- of 2013 (Gao et al., 2017). However, with the improvement of the nels and charms during nesting (Karlen et al., 2003). Ant activities can ecological environment, the massive restoration of vegetation provides form macropores in the soil and agglomerates on the soil surface, thereby a large amount of food and suitable living space for soil (Wang increasing rainfall infiltration and reducing soil water evaporation (Li et al., 2010). The diversity and quantity of soil animals in the Loess et al., 2017a), drainage, and runoffBrevik ( et al., 2015) around the nest. Plateau are also increasing. Mole crickets have larger body width than ants and earthworms and Soil organisms can seasonally and temporally influence many factors have strong forelegs suitable for digging. A mole cricket spends almost all of soil formation and structure (Brevik et al., 2015). The earthworm its life underground and forms underground tunnels for feeding, pro- consumes soil organic matter when excavating a tunnel (Edwards, 2004), tecting, and mating (Bailey et al., 2015). X-ray CT scans (Bailey et al.,

⁎ Corresponding author at: 26 Xinong Road, Yangling, Shaanxi 712100 China. E-mail address: [email protected] (T. Li). https://doi.org/10.1016/j.geoderma.2019.114144 Received 23 June 2019; Received in revised form 22 November 2019; Accepted 15 December 2019 Available online 28 December 2019 0016-7061/ © 2019 Elsevier B.V. All rights reserved. X. Yang, et al. Geoderma 363 (2020) 114144

2015; Villani et al., 2002), fiberglass resin (Brandenburg et al., 2002), In the arid and semi-arid regions of the Loess Plateau, with the and thin slurry of orthodontic plaster (Li et al., 2018) were used to large-scale restoration of vegetation and the massive increase of soil generate the three-dimensional images of mole cricket tunnels. The animals (ants, mole cricket, mice, etc.), the destruction of soil structures tunnels extended in horizontal and vertical directions, and the mean because of soil animals and the changes in soil water movement cannot diameter and depth of adult mole crickets tunnels were significantly be ignored. In recent years, the community of mole cricket in the larger than immature mole cricket tunnels (Li et al., 2018). In the hor- Liudaogou Catchment has gradually increased, especially in the semi- izontal direction, branching structures develop in all directions, and egg naked land, but its effect on the ecological environment has rarely been chambers are built next to horizontal tunnels (Endo, 2007). Mole crickets studied. The structure of the mole cricket tunnel and its influence on are solitary insects. A vertical tunnel usually holds only one mole cricket soil erosion and hydrologic processes were studied in the Liudaogou (Endo, 2007). Regardless of the tawny mole cricket, Scapteriscus vicinus Catchment (Li et al., 2018), but minimal attention was paid to the ef- Scudder, and the southern mole cricket, Scapteriscus borellii Giglio–Tos, fects of mole crickets activities on soil evaporation. their horizontal and vertical tunnels interconnect to form Y-shaped We hypothesized that the disturbance of the soil surface during channels (Villani et al., 2002). The depth of tunnel excavated by a mole long-term drought can reduce soil evaporation and increase water cricket can reach 70 cm (Brandenburg et al., 2002), and the width of the storage in small-scale soils. Therefore, the objectives of this study are to tunnel is 2–3 times of the mole cricket’s body width (Bailey et al., 2015). (1) determine the influence of adult and immature mole cricket on soil Mole crickets (Gryllotalpa unispina Saussure; Orthoptera: Gryllotalpidae) evaporation and (2) investigate the relationship between disturbance feed on the young roots, tender stems, and newly sprouted seeds of area created by burrowing mole crickets on the surface and evapora- various plants, so they dig for food under 2 cm of the surface. Therefore, tion. On the basis of previous studies on soil evaporation, this study has the ground often shows swollen fresh soil, which is the horizontal tunnel carried out a preliminary exploration of the mole cricket surface dis- under the bulge. Endo (2007) reported that the horizontal tunnel ex- turbance as a key factor affecting evaporation. This study combines soil cavated by mole cricket is 5 cm below the surface. The tunnel structures animals and soils to enrich the research content of soil animals and soil, vary with mole cricket type and affected by factors, such as soil moisture and provides new ideas and perspectives for studying the changes of (Hertl and Brandenburg, 2002), bulk density (Brandenburg et al., 2002; soil physical and chemical properties. Villani et al., 2002), environmental conditions, density of other in- dividuals, food resource distribution, and surface cover (Comber et al., 2. Materials and methods 2006). However, numerous horizontal and vertical channels formed during the excavation process affect soil hydraulic properties. Channels 2.1. Experimental site formed by mole crickets in soil are conducive to water flow and reduce surface runoff (Bailey et al., 2015). Horizontal caves on the surface of the The study site is located at the Shenmu Erosion and Environmental soil can intercept rainfall and reduce runoff, thereby increasing water Research Station in the Liudaogou Catchment of Shenmu County, penetration (Li et al., 2018). Agglomerates produced by earthworms Shaanxi Province, China (E110°21′–110°23′ N38°46′–38°51′). Situated have a certain water stability (Jouquet et al., 2012), whereas soil parti- in the hinterland of the Loess Plateau, it is a typical water–wind erosion cles formed by mole crickets’ horizontal excavation on the soil surface crisscross region. The area of the catchment is 6.89 km2, and the alti- are extremely vulnerable to erosion by rainstorm and to surface runoff tude is 1081–1274 m. The annual precipitation is 437 mm, and over (Li et al., 2018). When mole crickets excavate a horizontal channel, the 81% of the precipitation is concentrated in June–October, which be- surface and lower soil layer become separated and form a new soil layer, longs to a semiarid continental climate zone. The aridity index is 1.8, which has high porosity as sand or stone covering layer. The area of this and the mean annual potential evapotranspiration reaches 785 mm. new layer on the soil surface expands with the activities of mole crickets. The main vegetation type in the catchment is drought shrub-clustered This new soil layer may affect soil evaporation in a manner similar to grassland (Caragana korshinskii and Stipa capillata Linn). artificial cover, such as gravel, sand, pebbles (Xu et al., 2005), soil bio- crust (Rasiah et al., 2001; Ma and Li, 2011), and basalt tephra (Diaz et al., 2005). Therefore, soil layers can also prevent the soil surface from 2.2. Collection of soil and mole cricket being directly exposed to solar radiation (Chen et al., 2005; Ma and Li, 2011) and reduce the exchange of water vapor between the soil surface The soil and mole cricket for the experiments were collected in the and the atmosphere (Yuan et al., 2009). In addition, with the increase in Liudaogou Catchment. The most representative loam soil in this area the number of mole crickets, its effect on the ecological environment was selected as experimental soil. The disturbed soil was collected from cannot be ignored. Mole crickets are pests on farmland and lawns be- the field where mole crickets were often active. It was sieved througha cause they can cause serious damage to lawns and pastures through di- 2 mm mesh and air-dried under natural conditions. The basic physical rect feeding and underground tunnels (Frank and Parkman, 1999). and chemical properties of soil were measured using the well-mixed Herbivorous mole crickets (Brandenburg et al., 2002) and rodents primordial soil, and the results are presented in Table 1. (Herbst and Bennett, 2006) feed on the roots of creeping and gramineous Mole crickets (Gryllotalpa unispina Saussure; Orthoptera: plants and thus inhibit the growth of plants around the caves and reduce Gryllotalpidae)(Fig. 1) were collected in the field using a manual ex- vegetation coverage. Moreover, pesticides, fertilizers, and even ground- cavation of caves from August 1 to 20, 2018 in the Liudaogou Catch- water can enter the soil profile through preferential flow paths and in- ment. G. unispina Saussure is widely distributed in this area. G. unispina crease the risk of pollution (Dekker and Ritsema, 1994). Saussure nest channel is composed of horizontal and vertical parts. The horizontal channel is close to the soil surface, covered by loose soil and

Table 1 Basic physical and chemical properties of soil in the Liudaogou Catchment.

Soil type Soil bulk density(g cm−3) Soil mechanical composition Total organic carbon(g kg−1) Total nitrogen(g kg−1) Total phosphorus(g kg−1)

Clay /% Silt /% Sand /%

Loam 1.37 ± 0.02 13.88 ± 0.11 51.13 ± 1.14 34.99 ± 0.90 3.49 ± 0.08 1.54 ± 0.12 1.67 ± 0.07

Values of soil bulk density, soil mechanical composition, total organic carbon, total nitrogen and total phosphorus are means ± the standard error of the mean (SD, n = 4).

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Fig 1. Disturbance of the soil surface by the mole cricket (Gryllotalpa unispina Saussure) activity. crosses each other. Most mole cricket have one vertical channel, and disturbance of the soil surface was stable for approximately 7 days, some nests have two entrances. The other nest channels are inverted which was the same as the time Villani et al. (2002) studied the be- “Y” shaped with only one surface entrance. This species is large and havior of mole crickets. So after 7 days, the nylon net was removed so cause strong disturbance to the soil. The mole crickets were divided into that the mole crickets would have free access to the iron bucket. To adult and immature categories according to body size. An immature simulate the evaporation process of natural conditions and reduce the mole cricket is 2–3 cm long, and its wings are immature or newly de- influence of boundary effects as much as possible, the iron buckets were veloped. An adult mole cricket body is 3–5 cm long, and its wings are placed into three pits measuring 1 m wide, 1.2 m long, and 0.15 m deep well developed. Adult mole crickets tend to have deeper and more in the open space. A total of 90 iron buckets were randomly placed in extensive tunnels than immature mole crickets. Before the formal ex- the pits and evaporated under natural conditions. Five evaporating pans periment, they were provided organic shredded alfalfa leaves and ger- with a diameter of 20 cm were placed at a height of 70 cm nearby to minated millet seeds for food and held in a plastic box. measure the evaporation force of the atmosphere. Each bucket was weighed using an electronic scale with an accuracy 2.3. Experimental design of 1 g (with a measurement range of 0–30 kg) (Zhujiang Weighing Apparatus Co., Ltd. in Yongkang City, Zhejiang Province, China) at The experiment was designed with three treatments consisting of 8:00 pm every two days from August 23 to October 20, 2018. The only adding loam (control, CKL), loam and adult mole cricket (LA), and changes in weight of the iron bucket and the evaporation pan were loam and immature mole cricket (LI). CKL, LA, and LI treatments were recorded to represent amount of soil evaporation and atmospheric conducted with 30 replicates, so a total of 90 evaporation containers evaporation, respectively (the evaporation pan was replenished at (iron buckets) were prepared in this experiment. regular intervals to maintain a stable amount of water). The appropriate The air-dried loam soil of 7 kg was packed into each iron bucket area was selected for studying the effect of disturbance area on soil (20 cm diameter × 20 cm height). In this experiment, the soil bulk evaporation when the soil particle layer thickness was certain (Fig. 2). density in the iron bucket was also controlled at approximately The disturbance area varied from 0% and 100%, so the disturbance area 1.4 g cm3 to simulate the field environment. According to Wilson et al at 0%, 30%, 60%, 90%, and 100% were selected as a representative. A (1997) test method, a proper amount of water was added to the soil digital camera was used to take photos of the disturbed soil surface sample and mixed well to prepare a saturated slurry (initial water (Filmed on the 7th day of the trial). The calculation of the disturbance content was about 90%). The purpose was to obtain the sample with area was processed by Adobe Photoshop CS6 software. The area was simple initial state and homogeneous structure, improve the repeat- represented by pixels, and the area ratio was expressed in pixel ratio ability of the test, and facilitate the result analysis. The prepared slurry (the area ratio refers to the ratio of the area destroyed by the surface of sample was allowed to stand for 72 h to stabilize its settling. After 72 h, the soil to the total area during the excavation channel). the water on the surface was sucked with a 20 ml medical syringe. The According to the recorded weather conditions, the rainy days were iron bucket was evaporated under natural conditions for a few days to from August 30 to August 31, September 1, September 10 to 12, remove the gravity water to reach the field moisture capacity (25%). At September 17 to September 18, September 24 to September 25, October this time, the experiments were initiated. According to the Villani et al. 14, and October 18. (2002) experiment method, one mole cricket was placed in each iron bucket for conducting the experiments to avoid possible behavioral 2.4. Data analysis changes that may occur when multiple mole crickets are present. In this study, the upper part of each bucket was covered with nylon net (25 cm The ratio of soil evaporation to atmospheric evaporation was used long × 25 cm wide, 10 mm mesh size) to keep mole crickets from to compare the evaporation rate among different days in the successive escaping. The entire experimental area was covered with a canopy evaporation process. Before statistical analyses, the residuals from the when it rained. Preliminary test observation showed that the analysis of variance (ANOVA) were examined for normality and

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Fig 2. Area of soil surface disturbance caused by mole cricket activity (0% means bare soil that has not been treated with mole cricket). homogeneity for all the variables. The comparisons of evaporation rate evaporation to atmospheric evaporation was: LA > LI > CKL, and and cumulative soil surface evaporation were analyzed by using one- this difference gradually decreased with time. On the 51st to 58th days way ANOVA, followed by Fisher’s least significant difference (LSD) test of evaporation, the Es/Ea value under different treatments was about (P < 0.05) with SPSS 16.0 (IBM Corp., Armonk, NY). Microsoft Office 4.1%. Therefore, there was no significant (P > 0.05) difference be- 2016 (Microsoft Corporation, Redmond, US) was used to record data tween the different treatments. and preliminary processing. Origin 9.0 software (Origin Lab, Northampton, ME) was used to plot and fit curves. Photoshop CS6.0 (Adobe Systems Corporation, San Jose, US) was used in image proces- 3.2. Cumulative soil evaporation sing and calculation of area. The variation of accumulated evaporation in soil with adult and immature mole cricket activity is shown in Fig. 4. During the successive 3. Results evaporation process of 58 d under natural condition, the cumulative evaporation was gradually increased and approached 1.300 kg in all 3.1. Ratio of soil evaporation to atmospheric evaporation: Es/Ea during the treatments. The cumulative evaporation of the CKL in the first stage was evaporation process 1.044 kg compared with 0.787 and 0.898 kg under adult and immature mole cricket activity, respectively, accounting for 78.6%, 59.3%, and The variation of the ratio of soil evaporation to atmospheric eva- 67.6%, respectively, of the atmospheric evaporation separately during poration over time under three treatments of CKL, LA, and LI are shown the same period. Compared with CKL, the cumulative evaporation of in Fig. 3. The ratio of soil evaporation (Es) to atmospheric evaporation the LA and LI was significantly (P < 0.05) decreased, especially for the (Ea) decreased gradually over time. In the first two days of evaporation, LA. For the entire evaporation process, different treatments (CKL, LA, the water supply was sufficient, and the evaporation was relatively and LI) accounted for 37.4%, 37.1%, and 37.2% of the atmospheric high. The Es/Ea values of CKL, LA, and LI were 94.2%, 76.7%, and evaporation in the same period. Therefore, there was no significant 87.3%, respectively. During the first two days, when the soil moisture (P > 0.05) difference between the different treatments. In the caseof was higher, the LA and LI treatment significantly (P < 0.05) reduced the same initial water content, the cumulative evaporation amount was the evaporation, especially the LA treatment. According to the change always: LA < LI < CKL, and this rule was more significant in the of daily evaporation, the variation process of Es/Ea can be divided into early stage. In the first stage, mole cricket activity can reduce soil two stages with the evaporation. The first 18 days of evaporation were evaporation; the larger the mole cricket, the greater the inhibition ef- considered as the first stage. The order of Es/Ea values was: CKL> fect. However, for the entire process, no significant (P > 0.05) dif- LI > LA. In this stage, soil treated with mole cricket had significantly ference was observed in the cumulative evaporation among different (P < 0.05) lower evaporation rates compared with bare soil. The treatments, and the disturbance of mole cricket to the soil played a role subsequent days were regarded as the second stage. The ratio of soil in slowing down the evaporation.

Fig 3. Ratio of soil evaporation to atmospheric evaporation in the successive evaporation process among three treatments of CKL (only adding loam), LA (loam and adult mole cricket), and LI (loam and immature mole cricket). The vertical line divides the evaporation process into two stages (SD, n = 30).

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Fig 4. Temporal variation of soil cumulative evaporation under three treatments of only adding loam (control, CKL), loam and adult mole cricket (LA), and loam and immature mole cricket (LI). The vertical line divides the evaporation process into two stages (SD, n = 30).

3.3. Soil moisture variation in the successive evaporation process the value tended to be stable. Therefore, the difference between dif- ferent treatments was gradually reduced. Throughout the evaporation The comparison of soil moisture content between under mole process, the values of the soil water content followed the order LA > cricket treatment and that in bare soil is shown in Fig. 5. During the LI > CKL, which was more significant in the first stage. entire evaporation process, the soil moisture content gradually de- creased from 25.3% to 4.0%. In the case of consistent initial moisture 3.4. Relationship between the surface area destroyed by mole crickets and content, no significant (P > 0.05) difference of soil moisture content soil evaporation change was observed between mole cricket treatment and control treatment in first two days of evaporation. In the first stage, thewater Five different disturbance areas (0%, 30%, 60%, 90%, and 100%) content decreased sharply with time. For CKL treatment, soil moisture were chosen to evaluate the relationship between the surface area de- evaporation was faster, so the soil moisture content was significantly stroyed by mole crickets and soil evaporation (Fig. 2). A comparison of (P < 0.05) lower than the soil moisture content of LI and LA treat- the soil cumulative evaporation at 58 days among the treatments with ment. Ignoring different levels of soil moisture, the decrease rate ofsoil different disturbed areas is provided in Fig. 6. For the entire evapora- moisture content in LI and LA treatment was significantly lower than tion process, the cumulative evaporation increased gradually under that in CKL treatment (P < 0.05), and the rate increased with the different disturbed areas. The larger the disturbance area, the smaller decrease of mole cricket body size. However, in the second stage, the the cumulative evaporation. Fig. 6 shows that the order of cumulative soil moisture content of all treatments changed slowly with time, and evaporation under different disturbance areas is from large to small:

Fig 5. Relation of soil moisture content with time under three treatments of only adding loam (control, CKL), loam and adult mole cricket (LA), and loam and immature mole cricket (LI). The vertical line divides the evaporation process into two stages (SD, n = 30).

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Fig 6. Relationship between soil cumulative evaporation and areas of mole cricket disturbance (0%, 30%, 60%, 90%, and 100% means the area of the disturbance area as a percentage of the total area). The vertical line divides the evaporation process into two stages (SD, n = 4).

0% > 30% > 60% > 90% > 100%. However, in the late stage of In his research, aggregates were transported onto the surface by ant and evaporation, no significant (P > 0.05) difference was observed in the formed a new soil layer with high porosity as the gravel mulches. cumulative evaporation of other disturbed areas except for the 100% However, the disturbing effect of mole cricket activity on soil differed disturbance area. In the first two days of the evaporation process, the from that of ant. Compared with ant, the mole cricket was larger in evaporation rate was the fastest under different disturbance areas and body size, often excavating more horizontal tunnels, and loose surface accounted for 75.3%–94.2% of atmospheric evaporation during the soil when feeding. Whether mole cricket or ant, a new soil particle layer same period. Compared with the second stage, the evaporation rate in was formed by excavating activity similar to sand and gravel mulches. the first stage was fast, and the cumulative evaporation under different For ant, soil particles were moved from inside the nest to the ground disturbance areas was significant different (P < 0.05). With the de- without damaging the surface soil. For mole cricket, surface soil was crease of water content, the daily evaporation and the proportion of the destroyed in the process of excavating the tunnel such that the surface atmospheric evaporation force in the same period were also gradually of the soil formed a new soil layer as the sand or gravel mulches. The reduced. At the end of the evaporation process, the cumulative eva- disturbance of mole cricket on soil surface changed the uniform struc- poration of 100% disturbance was significantly (P < 0.05) lower than ture of soil surface layer. that of other disturbances. During the successive evaporation process of Previous studies have shown that gravel and sand mulches act as a 58 days under natural conditions, the cumulative evaporation under protective layer to block direct radiation from the sun and thus reduce different disturbance areas was exponentially correlated with time. evaporation (Chen et al., 2005; Ma and Li, 2011; Qiu et al., 2014). In However, the cumulative evaporation in the first stage changed linearly this study, the formation of a new soil particles on the soil surface by with time. The slope of the fitting equation gradually decreases as the mole cricket can also prevent the soil surface from being directly ex- disturbance area increases. The fitting equation of accumulated soil posed to solar radiation, intercept thermal conductivity, and reduce soil surface evaporation and time under different treatments are shown in surface temperature. Moreover, it can inhibit the rise of soil water along Table 2, and the correlative coefficient2 (R ) is high. the capillary flow, allowing moisture to pass through the pores ofthe mulch layer only in the form of a vapor phase (Ma and Li, 2011). The vapor in the covering pores was weakly diffused, so the water or vapor 4. Discussions contained in the pores was usually very high, which can reduce the evaporation of water on the soil surface (Yuan et al., 2009). With soil 4.1. Mole cricket influence the mechanism of soil evaporation particles layer mulches, the diffusion of water into the atmosphere re- quired passage through the gap of mulches, thereby extending the path Soil evaporation was greatly affected by atmospheric conditions, of movement of the water. soil water content, and surface mulch (Gupta et al., 2015). Mulches, such as gravel, sand, basaltic tephra, soil biocrust, sawdust, turf soil, smash of straw, and coal cinder can significantly inhibit soil evapora- 4.2. Two stages of soil evaporation tion (Kemper et al., 1994; Wang et al., 2014; Xie et al., 2010; Xu et al., 2005; Diaz et al., 2005; Belnap, 2006; Xiao et al., 2010; Xu et al., 2010). Previous studies showed that successive soil evaporation is divided Despite many kinds of covering materials, their mechanism of in- into two stages under constant external conditions (Black et al., 1969; hibiting evaporation is similar. Mulch can isolate the direct radiation of Hillel, 1971). In the first stage, the evaporation rates are very closeto the sun, reduce the internal temperature, cut off capillary flow, and free surface evaporation values, and the evaporation rates are high. In change the migration path of water (Chen et al., 2005; Ma and Li, 2011; the second stage, with soil water content reducing, losses by evapora- Qiu et al., 2014). Soil organisms play a vital role in shaping the soil tion occur at decreasing rates. Similarly, the evaporation process was environment by forming, modifying soil structures with pores and divided into two stages in this study. At the first stage, soil moisture tunnels, and transporting of soil particles (Puente et al., 2004). Li et al. content is relatively high, water supply is sufficient, and evaporation (2017b) reported that the aggregate mulches created by burrowing ant rate is relatively fast. During this stage, moisture rises to the surface (Camponotus japonicus) played a positive role in reducing evaporation. mainly through capillary motion controlled by atmospheric

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Table 2 Fitting equations of cumulative evaporation under different areas of mole cricket activity disturbance.

Areas of disturbance /% First stage fitted equations R2 Whole process fitted equations R2

0%30%60%90%100% y=51.2+62.267xy=39.9+57.892x- 0.9820.9850.9860.9850.975 y = 1397.5–1454.5*0.923^xy =- 0.9880.9890.9890.9960.996 y=30.2+55.677xy=34.1+45.694x- 1388.6–1443.8*0.931^xy =- y = 49.6 + 33.806x 1420.0–1479.2*0.937^xy =- 1474.6–1495.4*0.955^xy =- 1386.5–1353.7*0.969^x

In the equations, x is time (day), and y is the cumulative evaporation (g).

evaporation demand (Diaz et al., 2005). Because the water in the first the average disturbance area of the immature mole cricket is stage of bare soil treatment evaporates too fast, the water content also 140.99 cm2 (Fig. 7). This species is large and cause strong disturbance decreases rapidly, so the soil with mole cricket treatment in the second to the soil. The area of the cover layer formed by adult mole crickets on stage has high water content and higher evaporation rate. Soil water the surface is relatively large, and this cover layer is similar to that of content has a great influence on evaporation rate (Xiao et al. 2010). On artificial gravel, sand, pebbles, basalt tephra, and other material covers the other hand, for bare soil, as the water content of the soil surface (Xu et al., 2005; Diaz et al., 2005). Therefore, similar to an artificial decreases, forming a dry layer was easy. The dry layer had a negative cover layer, the cover layer formed by mole crickets can avoid direct effect on soil water evaporation (Xiao et al., 2010). Therefore, the daily sunlight (Chen et al., 2005; Ma and Li, 2011), prevent thermal con- evaporation at this stage was realized as: LA > LI > CKL. However, ductivity (Li, 2003; Montague and Kjelgren, 2004), reduce water and as the pore water gradually decreases, the conversion from liquid water air exchange (Yuan et al., 2009), cut off capillary flow, and change the to vapor water gradually became slower (Diaz et al., 2005). In the later migration path of water (Ma and Li, 2011; Qiu et al., 2014). Therefore, stage of the evaporation process, the soil moisture content was rela- compared with immature mole cricket, adult mole cricket has a tively low, so the difference of evaporation amount between different stronger ability to reduce the area directly exposed to solar radiation, treatments was relatively small. In the Fig. 3, the data changed dra- intercept thermal conductivity, reduce soil surface temperature and matically at around 8, 18, 28, 36, and 46 days, which may be caused by inhibit the rise of soil moisture along the capillary flow. The results of rain. As Hillel (1982) indicated, soil evaporation meets three condi- continuous evaporation study showed that the inhibition of adult mole tions: continuous heat supply, relative humidity difference, and con- cricket activity on soil evaporation was stronger (Figs. 4 and 5). tinuous water supply inside the soil. Therefore, in rainy weather, the temperature is lower, and the air humidity is higher, which can sig- 4.4. The relationship between disturbance area created by burrowing mole nificantly affect soil and atmospheric evaporation. crickets on the surface and evaporation.

The results show that the larger the soil disturbance area, the 4.3. Comparison of the effects of adult and immature mole crickets on soil stronger the ability to inhibit evaporation is (Fig. 6; Table 2). Due to the evaporation disturbing effect of the mole cricket activity on the soil surface, irre- gular soil particles were produced on the soil surface, which have high The uncontrollable factors of activity resulted in different porosity as the gravel mulches. The larger the disturbed area, the mole cricket damage soil surface areas. The relationship between body smaller the area directly radiated by the sun, and the smaller the pro- size (body length) of the mole cricket and the disturbance area is shown portion of water movement through the capillary tube. Therefore, the in Fig. 7. The observation of 60 mol cricket disturbance areas in this stronger the inhibition of evaporation, the smaller the amount of soil study showed that the adult mole cricket disturbance area was larger. evaporation (Fig. 6). This result was consistent with the results of other After measurement, the thickness of new soil layer on the surface was authors (Kemper et al., 1994; Wang et al., 2014; Xie et al., 2010; Xu about 1.5 cm, which was the same as the field survey results. The et al., 2005; Diaz et al., 2005; Belnap, 2006; Xiao et al., 2010; Xu et al., average disturbance area of the adult mole cricket is 255.34 cm2, while 2010), who also indicated that evaporation can be reduced in gravel- covered soil.

4.5. The possible ecological role of mole crickets

Mole crickets, pests on farmland and lawns, can cause serious da- mage to lawns and pastures through direct feeding and underground tunnels (Frank and Parkman, 1999). Herbivorous mole crickets (Brandenburg et al., 2002) and rodents (Herbst and Bennett, 2006) feed on the roots of creeping and gramineous plants and inhibits the growth of plants around the caves and reduce vegetation coverage. Although horizontal channels can reduce surface runoff (Bailey et al., 2015) and soil evaporation and provide habitat for other animals (Endo, 2007), they increase the likelihood of soil erosion (Li et al., 2018). Vertical tunnels can increase soil porosity and soil infiltration depth (Li et al., 2018). Moreover, pesticides, fertilizers, and even groundwater can enter the soil profile through preferential flow paths and pose agreat risk of pollution (Dekker and Ritsema, 1994). In the arid and semi-arid regions of the Loess plateau, the destruction of soil structures because of Fig 7. Relation between body size (body length) of mole cricket and the area of soil animals and the changes in soil water movement cannot be ignored. the disturbance. The disturbance of a soil surface during long-term drought can reduce

7 X. Yang, et al. Geoderma 363 (2020) 114144 soil evaporation and increase water storage in small-scale soils. With https://doi.org/10.1653/0015-4040(2002) 085[0383:taotso]2.0.co;2. loose porosity, the surface layer can provide habitats for plant seeds and Brevik, E.C., Cerdà, A., Mataix-Solera, J., Pereg, L., Quinton, J.N., Six, J., Van Oost, K., 2015. The interdisciplinary nature of soil. Soil 1, 117–129. https://doi.org/10.5194/ other soil animals (Gryllidae) and increase rainfall interception and soil-1-117-2015. infiltration. However, this study used the field microcosm methodto Chen, S.Y., Zhang, X.Y., Pei, D., Sun, H.Y., 2005. Effects of corn straw mulching on soil study the effects of mole cricket disturbance on soil evaporation, and temperature and soil evaporation of winter wheat field. Transactions of the Chinese Society of Agricultural Engineering 21, 171–173 (In Chinese). could not fully reflect the real situation in the wild. Further studies are Comber, S.C.L., Seabloom, E.W., Romanach, S.S., 2006. Burrow fractal dimension and needed to understand the relationship between soil animals and soil foraging success in subterranean rodents: a simulation. Behav. Ecol. 17, 188–195. water movements in the wild. Although this study can help us better Dekker, L.W., Ritsema, C.J., 1994. How water moves in a water repellent sandy soil: 1. understand the contribution of mole cricket activities to soil evapora- Potential and actual water repellency. Water Resour. Res. 30, 2507–2517. https:// doi.org/10.1029/94wr00749. tion in the Loess plateau, it still need to be combined with larger scale Diaz, F., Jimenez, C.C., Tejedor, W., 2005. Influence of the thickness and grain size of technology to maximize its effectiveness. tephra mulch on soil water evaporation. Agric. Water Manag. 74, 47–55. https://doi. org/10.1016/j.agwat.2004.10.011. Edwards, C.A., 2004. The importance of earthworms as key representatives of the soil 5. Conclusions fauna. In: Edwards, C.A. (Ed.), Earthworm Ecology, second ed. CRC Press, Boca Raton, FL, pp. 3–11. During the successive evaporation process of 58 d under natural Endo, C., 2007. The underground life of the oriental mole cricket: and analysis of burrow morphology. Proceedings of the Zoological Society of London 273: 414–420. doi: 10. condition, the results of our experiments show that evaporation was 1111/j.1469-7998.2007.00345.x. found to occur in two stages. In the first stage, mole cricket activity can Evans, T.A., Dawes, T.Z., Ward, P.R., Lo, N.T., 2011. Ants and termites increase crop yield reduce soil evaporation. But from the whole evaporation process, mole in a dry climate. Nat. Commun. 2, 262. https://doi.org/10.1038/ncomms1257. Frank, J.H., Parkman, J.P., 1999. Integrated pest management of pest mole crickets with cricket treatment plays a role in delaying the evaporation of water. The emphasis on southeastern USA. Integr. Pest Manag. Rev. 4, 39–52. https://doi.org/ disturbance of mole cricket on soil surface changed the uniform struc- 10.1023/A:1009628915989. ture of soil, and the loose particles on the surface inhibited the rising of Gao, H., Pang, G., Li, Z.B., Cheng, S., 2017. Evaluating the potential of vegetation re- storation in the loess plateau. Acta Geog. Sinica 72, 863–874. https://doi.org/10. capillary flow, thereby restraining the evaporation. With identical le- 11821/dlxb201705008. vels of soil water content, the surface evaporation reduction capacities Gupta, B., Shah, D.O., Mishra, B., Joshi, P.A., Gandhi, V.G., Fougat, R.S., 2015. Effect of were positively correlated with the areas of mole cricket disturbance top soil wettability on water evaporation and plant growth. J. Colloid Interface Sci. area from 0% to 100%. Compared with immature mole cricket, adult 449, 506–513. https://doi.org/10.1016/j.jcis.2015.02.018. Herbst, M., Bennett, N.C., 2006. Burrow architecture and burrowing dynamics of the mole cricket disturbance area was larger, the greater the inhibition of endangered Namaqua dune mole rat (Bathyergus janetta) (Rodentia: Bathyergidae). evaporation. This study helps us better understand the contribution of J. Zool. 270, 420–428. https://doi.org/10.1111/j.1469-7998.2006.00151.x. mole cricket activities to soil evaporation in the Loess Plateau. Hertl, P.T., Brandenburg, R.L., 2002. Effect of soil moisture and time of year on mole cricket (Orthoptera: Gryllotalpidae) surface tunneling. Environ. Entomol. 31, 476–481. https://doi.org/10.1603/0046-225x-31.3.476. Declaration of Competing Interest Hillel, D., 1982. Introduction to soil physical. Academic Press, New York. Hillel, D., 1971. Soil and water. Academic Press, NY and London, Physical Principles and Processes. The authors declare that they have no known competing financial Jouquet, P., Janeau, J.L., Pisano, A., Hai, T.S., Orange, D., Minh, L.T.N., Valentin, C., interests or personal relationships that could have appeared to influ- 2012. Influence of earthworms and termites on runoff and erosion in a tropical steep ence the work reported in this paper. slope fallow in vietnam: a rainfall simulation experiment. Appl. Soil Ecol. 61, 161–168. https://doi.org/10.1016/j.apsoil.2012.04.004. Karlen, D.L., Ditzler, C.A., Andrews, S.S., 2003. Soil quality: Why and how? Geoderma Acknowledgements 114, 145–156. https://doi.org/10.1016/S0016-7061(03)00039-9. Kemper, W.D., Nicks, A.D., Corey, A.T., 1994. Accumulation of water in soils under sand and gravel mulches. Soil Sci. Soc. Am. J. 58, 56–63. https://doi.org/10.2136/ This research was supported by the National Natural Science sssaj1994.03615995005800010008x. Foundation of China (41807011), the Open Research Fund of State Key Li, X.Y., 2003. Gravel-sand mulch for soil and water conservation in the semiarid loess Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau region of northwest China. Catena 52, 105–127. https://doi.org/10.1016/S0341- (A314021402-1910), and China Postdoctoral Science Foundation 8162(02)00181-9. Li, T.C., Shao, M.A., Jia, Y.H., 2017a. Effects of activities of ants (Camponotus japonicus) funded project (2018M631562). We thank Shenmu experimental sta- on soil moisture cannot be neglected in the northern Loess Plateau. Agric. Ecosyst. tion for erosion and environment to provide experimental conditions. Environ. 239, 182–187. https://doi.org/10.1016/j.agee.2017.01.024. We thank the editor and reviewers for the insightful comments and Li, T.C., Shao, M.A., Jia, Y.H., Jia, X.X., Huang, L.M., 2018. Small-scale observation on the effects of the burrowing activities of mole crickets on soil erosion and hydrologic suggestions on this paper. processes. Agric. Ecosyst. 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