Trophic Structure of Ground Dwelling Insects in the Coastal Zone Of
Total Page：16
File Type：pdf, Size：1020Kb
ISSN 20790961, Arid Ecosystems, 2015, Vol. 5, No. 4, pp. 222–229. © Pleiades Publishing, Ltd., 2015. Original Russian Text © I.I. Lyubechanskii, R.Ju. Dudko, A.V. Tiunov, V.G. Mordkovich, 2015, published in Aridnye Ekosistemy, 2015, Vol. 21, No. 4(65), pp. 33–42. SYSTEMATIC STUDY OF ARID TERRITORIES Trophic Structure of GroundDwelling Insects in the Coastal Zone of a Salt Lake in Southern Siberia Based on the Data of Isotopic Analysis I. I. Lyubechanskiia, R. Ju. Dudkoa, A. V. Tiunovb, V. G. Mordkovicha aInstitute of Systematics and Ecology of Animals, Siberian Branch, Russian Academy of Sciences, ul. Frunze 11, Novosibirsk, 630091 Russia bSevertsov Institute of Ecology and Evolution, Russian Academy of Sciences, pr. Leninskii 33, Moscow, 119071 Russia email: [email protected], [email protected] Received February 30, 2015 Abstract—The trophic structure of a grounddwelling insect community has been studied in the coastal zone of a salt lake in the southern foreststeppe (Novosibirsk oblast). Five contrasting habitats along a 170m cat ena with an altitude drop of 1.8 m were studied. In each habitat, the soil, as well as dominant insect and plant species, were sampled: phytophages, saprophages, and predators. According to a stableisotope analysis of carbon and nitrogen (δ13C and δ15N), phytophagous insects (the locust Epachromius pulverilentus and cara bid beetle Dicheirotrichus desertus) are closely connected to their food objects and hardly migrated along the catena. Saprophages (the mole cricket Gryllotalpa unispina and earwig Labidura riparia) use various food resources; some of them (mole crickets) tend to migrate between the biotopes. Predatory beetles (carabid imagoes) can be separated into three trophic guilds: (1) highly mobile active predators, including the tiger beetles Cephalota chiloleuca and C. elegans; (2) small generalist predators of Pogonini tribe (Pogonus cumanus, P. transfuga, Pogonistes rufoaeneus, and Cardiaderus chloroticus); and (3) relatively large consumers of soil saprophages and aquatic organisms (Curtonotus propinquus and Cymindis equestris). The trophic niche overlap of different predators is partially compensated by their confinement to different habitats. Keywords: Baraba Steppe, saline soils, soil invertebrates, trophic network, salt lakes, spatial structure DOI: 10.1134/S2079096115040083 The climate of the central areas of the continents birsk oblast alone (Fedorov and Mordkovich, 2012). are becoming more arid and contrasting as a result of The foreststeppe zone is the northern distribution global changes (Otsenochnyi doklad ob izmeneniyakh limit of saline lands in western Siberia and Eurasia as a klimata, 2008). Aridization is manifested not only in whole. In recent years, these biocenoses have tended an increase in the average annual temperature or sea to expand due to lake shallowing and drying. sonal maxima, but also in the shift of longterm flood ing cycles of drainless areas towards drying. Extremely dynamic biogeocenoses are formed in the littoral zone of salt lakes. They are similar to the In a wide area of the inland flow on the south of the nearwater ecosystems from which life arrived on land western Siberian Plain with its center in Lake Chany, (Ponomarenko, 2013). The soil cover in the littoral there are thousands of shallow drainless lakes varying zones of salt lakes are also very distinctive. They are in the degree of salinization. In the exclusively flat formed both on land and under water. In addition, the landscape of the Baraba Steppe (the altitude drop is ratio of the main elements in bottom sediments during about 10 m on a 10km long profile), the shoreline of the process of pedogenesis under aquatic conditions is these lakes is extremely mobile. There are therefore significantly different from that in watershed soils and wide areas along the shores that are at times flooded is close to that aquatic organisms (Pushkareva, 2013). and at times exposed to drying (littoral zones). Plants in such ecosystems are either absent or repre Weather and seasonal fluctuations in the level of water sented by a small number of specific halophilic spe bodies occur for several weeks or even days. They are cies. The key role in them is played by invertebrates, also influenced by longterm cycles with a periodicity which are numerous and vary in their size and way of of 30–50 years (Zapadnaya Sibir’, 1963; Krivenko, life. They utilize waterbody organic waste and enhance 1991; Vasil’ev et al., 2005). the conversion of a soil environment from anaerobic to The ecosystems of saline lands near the shores of aerobic (Mordkovich, 1973a; Fedorov and Mordkovich, saltwater bodies cover more than 3000 km2 in Novosi 2012). 222 TROPHIC STRUCTURE OF GROUNDDWELLING INSECTS 223 The habitats of various species in such ecosystems tens of meters, and the difference between the highest are quite densely “packed”: there are several variants and lowest levels of water is only 0.5 m. The lake was at of biogeocenoses on the profile along the first hun the average level in 2011, almost dried out in 2012, and dreds of meters laid perpendicularly to the shore due reached a high level in 2013. Five contrasting habitats to the high contrast of abiotic conditions. The spatial along the catena were studied. They were dry during and temporal structure of the insect community in the the study period. The habitats encircle the lake in the littoral zone of a salt lake described in the text below form of concentric stripes from 10 to 85 m in width. was studied in detail in 2011–2012 (Fedorov and They are clearly seen in the vegetation cover and are Mordkovich, 2012; Fedorov, 2013). separated from each other by sharp transitional zones Our goal was to analyze the trophic structure of the of considerably smaller width (from 2 to 5 m). community of grounddwelling insects in the littoral Habitat 1—lacustrinesilty, soraffected, sulfide, zone of the salt lake. Stableisotope analysis, which saline area with a width of 1015 m during the period has been widely applied in recent years, was used to of investigation. Higher plants are almost absent; iso fulfill this purpose. The isotopic composition of nitro lated glasswort (Salicornia perennans Wild.) shoots gen (15N/14N, commonly represented as δ15N) enables appear only toward August. Projective coverage is less estimation of the trophic level of an organism, whereas than 5%. the isotopic composition of carbon (13C/12C, δ13C) Habitat 2—meadow, saline land with clumps of makes it possible to specify the spectrum of its food S. perennans mixed with Artemisia nitrosa Web., Puc objects in a number of cases (Scheu and Falca, 2000; cinellia kulundensis Serg., Atriplex patens (Litv.) Iljin. McCutchan et al., 2003; Tiunov, 2007; Goncharov Projective coverage of plants is up to 70%. This zone is and Tiunov, 2013). up to 20 m in width. We assumed that (1) predatory insects, which are Habitat 3—a belt of Halocnemum strobilaceum (Pall.) relatively lowabundant and diverse in this ecosystem Bieb. dwarf semishrubs gradually scattered along the (as compared to sapro– and phytophages), will consti soraffected saline area in a small kettle. Plants are tute a competitionbased community consisting of aged 25–28 years. Soil is covered with a bright white salty more than one guild. This type of structural organiza crust. Projective coverage is 10–15%. The zone is about tion will be indicated by differences in the diet of pred 85 m in width. ators (and, accordingly, the isotopic composition) Habitat 4—a belt of dense Atriplex verrucifera Bieb. coexisting in one biotope. On the contrary, in the case and S. perennans clumps with a projective coverage of of spatial separation, predators with a similar morpho 70%. The soil under A. verrucifera is meadow saline logical structure can have the same diet (as well as iso alkali, which is is soraffected saline soil in the open topic composition). Furthermore, we assumed that (2) area. The zone is about 35 m in width. insects with higher mobility will have a wider range of δ13C and δ15N values and the same isotopic composi Habitat 5—halomesophytic meadow on meadow, tion in different biotopes, whereas those with lower salinealkali soil with a welldeveloped (10 cm) turf mobility will have a smaller range of these values and horizon located on a short bank near the lake having a more pronounced biotopic differences. width of about 10 m. The dominant plant species are Achnatherum splendens (Trin.) Nevski., Limonium cor alloides (Tausch) Lincz., A. verrucifera, and A. nitrosa. MATERIALS AND METHODS Projective coverage is about 100%. The material for this study was sampled on the bor In all habitats except 5, plant litter on the soil sur der between the Baraba and Kuludinskaya forest face is almost totally absent. The physical and chemi steppe in the southern part of Novosibirsk oblast (the cal properties of soils in the studied habitats are given south of western Siberia). Here, the winter period lasts in the table. from early November to late March; the average tem We analyzed the stableisotope composition of car perature in January is –19 to –21°C. The temperature bon and nitrogen in the tissues of dominant insect spe in July is about +18–19°C with an absolute maximum cies representing different trophic groups (phytoph of +40°C. The main amount of precipitation falls in ages, saprophages, and predators) in the model eco summer; the average annual amount of precipitation is system, as well as in the plants and soil. The material 300–350 mm. Ground waters flow close to the surface for the study was collected in August 2013. In each of and are often salinized. Sulfate and chloride waters the five habitats, we took samples of the upper soil with a mineralization of 4–12 g/L are found (Zapad horizon (0–2 cm) in five replications and plants dom naya Sibir’, 1963).