Geoderma 348 (2019) 158–167 Contents lists available at ScienceDirect Geoderma journal homepage: www.elsevier.com/locate/geoderma Camponotus japonicus burrowing activities exacerbate soil erosion on bare T slopes c,⁎ a,b,d,⁎⁎ a Tongchuan Lia,b, Yuhua Jia , Ming'an Shao , Nan Shen a State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling 712100, China b Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China c College of Water Conservancy, Key Laboratory of Soil Erosion Control and Ecological Restoration in Liaoning Province, Shenyang Agricultural University, Shenyang 110866, China d College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, China ARTICLE INFO ABSTRACT Handling Editor: Morgan Cristine L.S. As soil ecosystem engineers, ants considerably affect soil physical and chemical properties, and further ac- ff ff Keywords: cordingly a ect soil erosion. However, few study was made on studying the e ects of ant-burrowing activities on Ant mound soil erosion previously. This study quantified the impacts of ant (Camponotus japonicus)-burrowing activities on Rainfall simulation runoff and soil erosion rates. Simulated laboratory rainfall experiments were undertaken on six soil tanks filled Soil erosion rate with clay-loam soil classified as a cumulic anthrosol, three of which introduced with ant colonies for two days − Runoff rate and the other three were without ant colonies, under 40, 80, and 120 mm h 1 of rainfall intensities and a slope fi − Water in ltration of 15°. Results showed that ants made mounds with a bulk density of 0.75 g cm 3, which was lower than that of − the soil matrix, i.e. 1.34 g cm 3. Soil erosion rates for the tanks with ants were 6.78, 36.90, and − − − 62.00 g m 2 min 1 under three rainfall intensities of 40, 80, and 120 mm h 1, which were much higher than − − those of 3.94, 23.49, and 44.48 g m 2 min 1 for the tanks without ants. Ant nests reduced the runoff rate by 31%, 20% and 13% compared with those without ants and enhanced the soil water storage within 90 cm depth. Ant nests played a positive role in soil water conservation due to the large nest entrance diameter and the continuous macropore network. However, the ant mounds provided a loose erodible material and changed micro-topography of the slope surface, thereby accelerating the rill formation and exacerbating soil erosion. This study can help understand the effects of burrowing insects on soil erosion, which is an important environmental problem on the Loess Plateau. 1. Introduction Loess Plateau and can make nest entrances with large diameters (4.1–6.6 mm) (Li et al., 2017a). Ant nests can be 10 cm to almost 4 m Ants are present in almost all terrestrial ecosystems (Liu et al., 2010) deep and are akin to underground fortresses (Tschinkel, 2003). These and are ecosystem engineers (Jones et al., 1994) that can affect the depths are much greater than those of other insects, such as mole structure (Tschinkel, 2003), hydrology (Cerdà and Jurgensen, 2008), crickets (64.1 cm) (Bailey et al., 2015) and dung beetles (20–30 cm) chemistry (Jílková et al., 2011) and biota of soils (Ginzburg et al., (Brown et al., 2010). 2008). The burrowing activities of ants dramatically alter the physical Some studies focused on the effects of ant nests on the infiltration of properties of soil at a small scale. Ant colonies are able to create water and solutes (e.g. Cerdà and Jurgensen, 2008; Li et al., 2014). abundant macropores, galleries, and chambers within their nests Large-diameter tunnels can create high levels of water infiltration (Karlen et al., 2003). Nest size depends on the body type of ants, colony (Eldridge, 1993). Owing to the large nest entrance diameter and the scale and ant species. The species of ants herein is Camponotus japonicus, continuous macropore network of C. japonicus nests (Li et al., 2017a), which has the largest body (10–12 mm long) among ants found on the rainfall can quickly flow into the soil (Bailey et al., 2015). Burrows with ⁎ Correspondence to: Y. Jia, College of Water Conservancy, Key Laboratory of Soil Erosion Control and Ecological Restoration in Liaoning Province, Shenyang Agricultural University, Shenyang, 110866, China. ⁎⁎ Correspondence to: M. Shao, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China. E-mail addresses: [email protected] (Y. Jia), [email protected] (M. Shao). https://doi.org/10.1016/j.geoderma.2019.04.035 Received 28 October 2018; Received in revised form 8 April 2019; Accepted 18 April 2019 0016-7061/ © 2019 Elsevier B.V. All rights reserved. Y. Jia, et al. Geoderma 348 (2019) 158–167 large tunnels also have a large contact area between nests and soil, The soil tank (2 m long, 0.5 m wide, and 1.0 m deep) is shown in thereby increasing infiltration capacity. Li et al. (2014) demonstrated Fig. 1. The tank had 351 holes (0.5 cm in diameter) at the bottom to that ant-induced soil disturbance can increase the amount of soil water facilitate drainage. Prior to packing the tank, the soil water content of at 40–100 cm deep by enhancing infiltration in areas covered by bio- the tested soil was determined and used to calculate how much soil was − logical soil crusts in the arid desert ecosystems of China. With such needed and to obtain the target bulk density of 1.35 g cm 3, which was high-level infiltration, ant nests can cause only a small amount of sur- similar to that in the field. First, a 5 cm thick layer of sand was packed face runoff at the fine scale (Li et al., 2014). Within a landscape, ant at the bottom of the tank to allow free drainage of excess water. During nests also increase the heterogeneity of infiltration rates and alter sur- the packing process, the soil layer was packed in 10 cm increments. face hydrological processes (Cammeraat and Risch, 2008). Second, the tanks were flatly exposed to rainfall and solar radiation for Ants can further create spherical soil pellets and carry them onto the a month to ensure that the simulated soil water conditions in the tanks soil surface with their mandibles when burrowing a nest. These pellets are similar to those in the field. Prior to the experiments, the slope of are stacked around the nest entrance and form a mound that is rela- the soil tank was adjusted to 15°. Three pipes (100 cm long and 2.8 cm tively stable when the wind blows. In dry season, ant mounds can re- in diameter) were installed in the soil (Fig. 1) to measure soil water duce soil evaporation (Li et al., 2017b), similar to artificial mulching contents at depths of 10, 20, 30, 50 and 90 cm with a PR2–6 probe such as gravel, sand, cobble, basaltic tephra and soil biocrust covering (Cambridge, UK, Delta-T Device Ltd.). No pre-rain was conducted to (Diaz et al., 2005; Ma and Li, 2011). However, unconsolidated soil saturate the surface soil before rainfall. Two soil tanks (with and brought to the surface by ants can also increase the potential for soil without ants) were used in each rainfall event. Each treatment was loss (Cerdà and Jurgensen, 2008). Ant-made pellets (Li et al., 2017b) conducted once; thus, six soil tanks were prepared in total. can easily be hydrolysed and they lead to soil detachment during heavy rains (Cerdà and Doerr, 2007). Many ant species can build aboveground 2.3. Source of test ants mounds or anthills on the soil surface (Ohashi et al., 2005; Kilpelainen et al., 2007). The mounds created by the chaco leafcutter ant (Atta The ants used in this study were collected from several C. japonicus vollenweideri) can considerably affect surface hydraulic processes and nests in the field of Yangling City through a field survey. We dug the sediment transport (Cerdà and Jurgensen, 2008, 2011). However, re- soil along the tunnels of ant nests using a small shovel. Once the nests search that quantitatively evaluates the effects of ant-burrowing ac- were destroyed, soldier and worker ants emerged to defend the nests tivities on runoff and soil loss remains lacking. and were collected using a modified dust catcher. After the slope of the In this study, three simulated rainfall experiments were conducted soil tank was adjusted to 15°, 12 colonies with 200 worker ants in each to (1) quantify the effects of ant-burrowing activities on soil water colony were collected and introduced into the tanks. We considered no content profile, runoff rate and soil erosion rate under different rainfall significant difference in nest volume among the plots with an equal intensities and (2) explore the mechanism through which ant bur- number of worker ants introduced into soils. Four PVC cylinders (40 cm rowing activities affect soil loss. diameter and 20 cm height) were evenly laid onto the soil surface of each tank. A colony was introduced into each PVC cylinder. To prevent 2. Materials and methods ants from escaping, talcum powder was smeared on the inner wall of each cylinder. Damp soil was easy to burrow, and the ants constructed 2.1. Rainfall simulator and lived in their nest for two days. A rainfall simulation system was used to apply rainfall in the rain- 2.4. Experimental measurements fall-simulation laboratory of the State Key Laboratory of Soil Erosion and Dryland Farming in Yangling City, Shaanxi Province, China.
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