PROCEEDINGS OF THE LATVIAN ACADEMY OF SCIENCES. Section B, Vol. 69 (2015), No. 3 (696), pp. 120–131. DOI: 10.1515/prolas-2015-0017 ECOLOGY AND DIVERSITY OF URBAN PINE FOREST SOIL INVERTEBRATES IN RÎGA, LATVIA Dmitry Telnov and Ineta Salmane# Institute of Biology, University of Latvia, 3 Miera Str., LV-2169 Salaspils, LATVIA # Corresponding author: [email protected] Communicated by Viesturs Melecis A study on ecology and diversity of soil invertebrates of urban pine and mixed pine forests was carried out in seven different sampling plots in Rîga during 2014. Ninety eight soil samples were processed and in total, 40 426 specimens were extracted (of them, 25 237 specimens were iden- tified to species level and 15 189 to order level). Indices (abundance, community similarity etc.) characterising faunal diversity and species communities of Rîga city soil fauna were estimated. The most numerous soil invertebrate groups were Collembola, Oribatida and Mesostigmata, ac- counting for 95% of all collected animals. There was rather high diversity of soil invertebrates in the disturbed urban forest habitats, but undisturbed soils harbour a greater species richness of mite fauna than disturbed soils. Key words: soil invertebrate fauna, urban forest, bioindication. INTRODUCTION Urban forests are green islands in an anthropogenic land- scape and support biological diversity within surrounding Urbanisation is increasing worldwide. Today, 45% of the built-up areas and streets (McPherson et al, 1997). Urban human population lives in cities, and in industrialised coun- forests are typical but specific ecosystems for Latvia, where tries this proportion increases to about 80% (Magura et al., nearly 20% of urban areas are forested. Pine forests are the 2008). Urbanisation is associated with a variety of effects most typical among them. These forests are under long-term on the soil system, including pollution, conversion of indig- anthropogenic pressure and urban soil mesofauna are con- enous habitats to various forms of land use, habitat frag- sidered to be degraded from environmental stress and eco- mentation and loss, and soil community changes (Pickett et logical forest succession is progressing toward deciduous al., 2001; Santorufo et al., 2012). Habitat conditions in cit- forests caused by soil eutrophication. ies much differ from those in natural habitats (Niedbala et Understanding of urban ecosystems requires information al., 1990). Especially the soil is subject to major transfor- about the response of soil biotic communities to environ- mations, which are reflected by the species composition and mental changes within large cities (Smith et al., 2006), and abundance of soil fauna (Niedbala et al., 1990). As it is well particularly the reaction of soil mesofauna to forest type known, soil plays an irreplaceable role in the biosphere: it succession and environmental stress (Barbercheck et al., governs plant productivity, organic matter degradation and 2009). nutrient cycling (Santorufo et al., 2012). Soil living organ- isms, including soil invertebrate fauna affect ecosystem pro- Surprisingly few data are available on invertebrate fauna cesses, such as organic matter decomposition, nutrient min- and ecology of Rîga. Even faunistic data are limited to eralisation and cycling, microbial activity, and soil mixing half-a-dozen papers devoted to leafhoppers (Danka, 1973), (Murphy, 1955; Witt, 1997; Koehler, 1999; Liiri et al., blow flies (Danka, 1979), barklices (Danka and Spuris 2002; Huhta et al., 2005; Huhta, 2007; Santorufo et al., 1977), ground beetles (Stiprais, 1973a; Melecis et al., 2012). They are involved in creation of the soil system, 1999), and ants (Stiprais, 1973b). An ecological description which acts as an environment for organisms, and within of the territory of Rîga was published in 1973 (Danka and which they are adapted (Colemann and Crossley, 1996). Stiprais 1973) as an introductional paper in a series devoted The soil invertebrates in nature closely interact with abiotic to the entomofauna of Rîga. environmental factors, which affect their activities, and many of them respond sensitively to changes in the environ- Of epigeic and soil arthropods, ground beetles (Coleoptera: ment conditions, and thus may be used as indicators of soil Carabidae) and ants (Hymenoptera: Formicidae) were cov- quality (Reddy 1986; Coleman, 2008). ered by sporadic studies in Rîga. Nearly one half of Latvian 120 Proc. Latvian Acad. Sci., Section B, Vol. 69 (2015), No. 3. ground beetle fauna, or 128 species, were recorded from MATERIALS AND METHODS Rîga (Stiprais, 1973a), and supplemented by several species Study area. The study was carried out in Rîga, the capital found during later studies (Melecis et al., 1999). Ground 2 beetles are among the most successful epigeic arthropods in of Latvia. The present area of Rîga is 304 km ; of which urban environments, but such high species diversity is a re- ~56% comprises build up areas and roads, 28% green sult of high diversity of available ecological niches. Fifteen spaces and ~16% water bodies (www.riga.lv). The territory ant species have been recorded from the territory of Rîga of Rîga expanded rapidly in the post-Second World War pe- (Stiprais, 1973b), of them Formica species that were mostly riod, when large surrounding areas were incorporated into found in forested areas. the city. In Latvia, after the Second World War, the urban forests in the inner city were protected by legislation of the Some data are available from Lapiòa (Lapiòa, 1988) on soil Soviet period and most of present forested areas in Rîga are Mesostigmata mites of Rîga and Jûrmala. She mentioned 50 aged up to 100 years. These forests were mostly planted species from both urban forests and gardens. Some findings post-Second World War, or expanded around older forest of Mesostigmata mites in various habitats in Cçsis, Jûrmala, fragments. Ogre, Rîga, Salaspils, and Sigulda were published by I. Sal- In Latvia, nearly 20% of the urban area is covered by for- mane (Salmane, 2005a & b; Salmane and Meiere, 2005; ests (Donis, 2003). No less than one half of green spaces in Kontschán Salmane, 2006; 2007a & b; et al., 2008; Rîga are forested areas, which amounts to 4244 ha Salmane, 2009; Salmane and Telnov, 2009). Still, all these (www.riga.lv). Rîga forests consist of 15 forest tracts that records are fragmentary and no planned investigation or are connected with rural forests or are smaller, isolated for- monitoring of soil invertebrate fauna in Rîga or any other ests — remnants of ancient forest or planted forests city of Latvia has been made. (Straupe et al., 2012). Scots pine (Pinus sylvestris)isthe prevailing species in Rîga forests, except for stands on allu- Of non-epigeic species, leafhoppers (Homoptera: Auche- vial soils, which are mostly forested by black alder (Alnus norryncha), barklices (Psocoptera) and blow flies (Diptera: glutinosa). Pine forests in Rîga cover in total 46.9 km2 or Calliphoridae) have been mentioned in the Rîga fauna. 88% of total forest area in the city (Straupe et al., 2012). Eighty seven species of Auchenorrhyncha were recorded The pine forests in Rîga and its suburb area have mostly de- from the territory of Rîga, of them 74 species connected veloped on poor sandy soils. In total, Rîga city forests con- with grasslands and only few forest species (Danka, 1973). sist of 15 forest tracts (Jankovska et al., 2014) of various Only six species have been recorded from historical old grade of isolation. town of Rîga, where green spaces are very limited. Among twenty barklice species found in Rîga, 15 species were re- So far 154 vascular plant and 18 moss species have been re- corded from the inner city parks (species possible connected ported from Rîga urban pine forests (Straupe et al., 2012). with old-growth broad-leaved trees) (Danka and Spuris, 1977). Only nine species of blow flies (Diptera: Callipho- Study plots. Seven forest plots were selected for collection ridae) have been recorded from Rîga, of them three species of soil invertebrates. Of them, one plot was located on the from the central part of the city (Danka, 1979). left and six plots on the right side of River Daugava (Fig. 1). The characteristics of plots (numbered 1 to 7) are briefly No revisional account of molluscs exists for Rîga. described in Table 1. Data on Collembola are absent for Rîga almost completely. Consequently, no studies on ecology or urban pressure on arthropod communities for the territory of Rîga city have been previously published. Our general objective was to determine if selected groups of soil arthropods and molluscs differed consistently according to relative level of pine and pine mixed forest succession and therefore could serve as potential biological indicators of ecosystem condition across forest ecosystems in the ur- ban environment. The aim was to discover differences or similarities in soil invertebrate communities among the ur- ban pine forest patches with variable vegetation and soil conditions. To test this concept, soil and epigeic arthropod and mollusc populations were examined in seven forest patches in relatively disturbed and undisturbed sites multi- ple times within one season. We selected Rîga as the largest and most populated city in NE Europe, as it is known as rich in forest ecosystems of various disturbance (Jankovska et al., 2014). Fig. 1. Sampling plots and their location in Rîga, 2014. Proc. Latvian Acad. Sci., Section B, Vol. 69 (2015), No. 3. 121 Table 1 BRIEF GEOBOTANICAL DESCRIPTION OF URBAN