Ground beetles (Carabidae) in urban habitats of Kaluga City (Russia)

Abstract Background Ground beetles (Carabidae, Coleoptera) are one of the most species-rich and well-studied insect families. However, the number of published datasets is disproportionately low against the biodiversity of this group. According to GBIF, only a fifth of the percentage of all published data covers ground beetles. This article describes a sampling-event dataset providing primary data on ground beetles collected in urban and suburban habitats in Kaluga, a typical central Russian city. We surveyed habitats of different land-use types and the extent and intensity of anthropogenic influence: yards, gardens, quarries, small urban woodlands, grasslands and riparian habitats. Carabids were collected by pitfall traps during most of the vegetative season (mostly from late April - early May to at least early October) for 13 seasons between 1994 and 2015. In total, the dataset contains 189 carabid species and 79,091 specimens. The dataset provides information about species composition and abundance, habitat distribution, seasonal and long-term dynamics of carabid beetles in environments of different degrees of urbanisation. New information This dataset is the first sampling-event dataset about carabids in various urban habitats published through GBIF.


Introduction
Ground beetles (Coleoptera, Carabidae) are a particularly popular model group of organisms for many kinds of ecological and environmental research, including studies of urbanisation (e.g. Klausnitzer and Richter 1983, Weller and Ganzhorn 2004, Magura et al. 2008, Niemelä and Kotze 2009, Schuett et al. 2018). The number of such papers has rapidly increased since the early 2000s (Magura and Lövei 2020). However, the results of these studies show inconsistent patterns of the effects of urbanisation on carabids. Generally, ground beetle assemblages in urban areas are species-poor, but sometimes researchers find high species richness and some rare species in urban and suburban habitats (Eversham et al. 1996, Zolotarev and Belskaya 2015, Belskaya et al. 2019. For Russian urban areas, there is quite a large array of carabid surveys (e.g. Dorofeev 1995, Sharova and Kiselev 1999, Eremejeva and Efimov 2006, Semenova 2008, Aleksanov et al. 2010, Zolotarev and Belskaya 2015, Aleksanov et al. 2019, Belskaya et al. 2019). However, the assessment of species diversity for different cities is rather complicated due to variation in sampling design in terms of sample plot sets and sampling methods. Typically ten traps per plot are often used to survey urban forests and parks (Niemelä et al. 2002, Semenova 2008, Niemelä and Kotze 2009), but sometimes eight (Weller and Ganzhorn 2004) or five (Deichsel 2006) traps were exposed. In urban grasslands, researchers have used six traps (Hartley et al. 2007) or have not mentioned trap numbers at all (Sharova andKiselev 1999, Eremejeva andEfimov 2006). To understand patterns of formation of ground beetles assemblages in urban areas, we definitely need primary data. However, the above-cited Russian urban studies of carabids did not publish these. For Russia, a series of datasets on ground beetles from habitats of relatively low disturbance were published recently (Konakova and Kolesnikova 2018, Makarov and Sundukov 2021, Sundukov and Makarov 2021, Zinovyev et al. 2021. Most of them are located in Nature Reserves and National Parks. A considerable dataset was published for broadleaved forests of Kaluga Oblast, including Kaluga Urban Okrug (Shashkov et al. 2020a, Shashkov et al. 2020b). The dataset presented here complements the above-cited datasets with information from highly transformed habitats of this region.
Kaluga is a typical Central Russian town, amongst which there are both provincial centres such as Tver, Vladimir or Tula and municipalities -Serpukhov, Kolomna or others. Such a city usually occupies areas ranging from dozens to just over 150 km and hosts populations of 100 to 400 thousand people. The centuries-old history and location, usually 2 on a large river (Oka or Volga, for example) , result in an irregular planning and complex development history of such cities. The city centres usually formed between more than three and two hundred years ago, often spontaneously. Multi-storey housing can be surrounded by quarters of private householding with gardens and orchards. Wastelands with dense wild grass are usual, on the periphery of industrial zones, adjacent to railroads or even amongst high buildings, as a consequence of abandoned former Soviet projects. A large watercourse with its tributaries forms a complex mosaic of near-water habitats.

Sampling methods
Study extent: Kaluga City is situated in the west of European Russia, in its middle (non-Chernozem) zone on the Oka River 150 kilometres (93 mi) southwest of Moscow. The climate is moderately continental with distinct seasons: warm and humid summers and cold winters with stable snow cover. According to nearest (~ 70 km SW) weather station, for which open data are available -Suhinichi (RSM00027707), the average annual air temperature during years of investigation  was 5.8°C. The average temperature in July was +19.1°C and in January, −6.9°C. Annual precipitation was about 633 millimetres (Bulygina et al. 2014). The city is situated on the southern edge of a mixed broadleaved-coniferous forests subzone or continental biogeographical region (Anonymous 2016), on the north margin of the Central Russian Upland. The area of the City is 168.8 km and the population is about 330 thousand people.
Prevailing landscapes of Kaluga City are flat, with undulating moraine plains shaped by the Moscow stage of the Dnieper glaciation. The main type of sediments is postglacial mantleloams. Watersheds are flat and poorly drained. The minimal height above sea level is 116-120 m and the highest point reaches 235 m a.s.l. Along the Oka River, there is a highly-dissected erosional plain.
Regarding vegetation zonation, the area belongs to the subzone of spruce-broadleaved forests, a spruce-oak vegetation district (Pashkang 1992). As for the typical central Russian provincial centre, the urban landscapes of Kaluga City have developed more or less smoothly since the 16 century. The planning structures of Kaluga City were generally established during the last half of 18 and the first half of the 19 century. The modern city area has a striped pattern of residential and industrial buildings and agricultural lands because historically residential areas were planned near factories and other industrial objects. We distinguished three positions in the urban landscapes: city centre, city periphery and suburban zone. Locations of sample plots are mapped in Fig. 1  Investigated sites can be grouped into six types of habitats which are characteristic of the urban area: 1. Forests (Fig. 2, Fig. 3) -habitats with area >0.5 ha where the dominant vegetation is trees with a canopy cover of at least 10%. In Kaluga, such habitats are located mainly in gullies and ravines. These sites are slightly managed and anthropogenic impact manifests mainly as littering. These forests are deciduous with Acer platanoides, Tilia cordata, Quercus robur, Acer negundo, Ulmus spp., Populus sp. and Salix spp. The herb layer is Table 2.
Descriptive characteristics of carabid samples for different types of habitats in the City of Kaluga.

Figure 1.
Location of surveyed habitats in Kaluga City and vicinities. Plot codes are the same as in Table 1 and correspond to parentEventID in the dataset. mainly shaped by nitrophilous weeds or nemoral herbs, which are stress-tolerators or ruderals. In one forest, the dominant tree was Pinus sylvestris and, in another, it was silver birch (Betula pendula). (Fig. 4) -sites along river, shaped by Salix triandra and other small Salix spp. or box-elder (Acer negundo). The herb layer is mainly shaped by ruderal weeds and locally, there are deadcover patches. Formally, they can be considered  Small deciduous wood (03-Park) as a forest, but they have some distinguishing habitat features: they are very narrow (about 20 m) and strongly impacted by the river. Riparian species have a large proportion in the ground beetle assemblages. Therefore, we distinguished this habitat as a distinct type.

Riparian wooded habitats
3. Yards (Fig. 5) -building areas with lines of trees, ornamental gardens and small parks beside houses or in city squares. These habitats consist of small groups of trees, grassy patches, flowerbeds surrounded by buildings and pavement with artificial surfaces.
4. Gardens -habitats with a mosaic of cultivated trees and shrubs (mainly fruit) and herbs (vegetable or ornamental) without large buildings, roads and pavements (Fig. 6,Fig. 7).  Yard with grass patches (EBCp).
They include kitchen and allotment gardens. Soils are regularly tilled and irrigated. In Kaluga, gardens are aggregated to more or less large arrays. Some plots were fallow and were overgrown by ruderal herbs in the year of sampling.
5. Grasslands (Fig. 8) -in Kaluga City, grasslands are located mainly in wastelands between industrial buildings and protected belts along roads and railways. Sometimes,  Garden (EBCg) there are poor sites with Calamagrostis epigeios and, sometimes, there are plots dominated by mesophile grasses (Festuca pratense, Dactylus glomerata, Phleum pratense); sometimes, there are poorly-drained sites with hygrophilic grasses and sedges.
6. Former quarry -the set of the biotopes on the slopes and bed of limestone the quarry, finally abandoned at least 30 years ago. The surveyed quarry is located in the northwest suburb and surrounded by spruce and pine forests. There is a village about one kilometre towards the north (Fig. 9). This type of habitat provides the possibility to investigate primary succession in vegetation and soil fauna population. That is why we consider this place as a distinct type of area. Grassland between a railway and a road (Gr).

Ground beetles (Carabidae) in urban habitats of Kaluga City (Russia)
Sampling description: The beetles were collected with soil pitfall traps (0.5 l transparent plastic cups with a mouth of 85 mm in diameter filled to about a third (150 ml) with 4% formalin solution, with covers made of transparent polyethylene film). For the broadleaved forest of the Kaluga Region, we suggested that it needs 30 traps to reveal the species composition of carabids (Alexeev and Aleksanov 2017). Urban habitats are small and frequently disturbed, so we usually expose 15 or 10 traps for small plots. Some neighbouring plots were divided into two habitats after collecting the samples, so trap numbers for each habitat were fewer. Sometimes traps were destroyed by people. Therefore, the number of traps was fewer than 15 or 10 in such cases. For relatively large forests, 30 traps were exposed in some years. Pitfall traps were exposed continuously from April or May to October or November. In some cases, traps were operated for a shorter time, about two or three months (4 plots) or even about one and half months (1 plot, 01-Gag). For most samples, the traps were emptied within an interval of one to three weeks in most cases. Sometimes, the interval was longer, usually at the late season when the activity of carabids was low. Amongst 47 sampling plots, most were sampled once, i.e. during one season, six during two or three seasons and one during six. There were two consecutive seasons (no more) in five cases.
It is worth noting that plots with the same alphabetic acronym in code could be a different biotope (94-Zh, 95-Zh and 03-Zh) or similar biotopes in different, but places situated nearby (97-Ber and 03-Ber). Although such biotopes represented one continuous vegetation area within the same mesorelief form (afforested gullies, for instance), these may be different parts of it.
Thereafter, a series of continuous sampling events within one sampling plot during one season we called a "survey". We investigated 47 habitats (sample plots). Some of them were sampled during two, three or even six seasons. So, a total of 60 surveys were done. Unique values of DwC term parentEventID correspond to a distinct survey.
On each plot within a survey, 4 to 30 traps were established at the beginning of the season, but more often, 15 or 10 (less often). Usually, we chose sites for sampling within private (with the consent of owners), restricted (office territory) or low-attandance areas to ensure non-disturbance of the traps and the continuity of the investigations. Nevertheless, there were some cases of vandalism or unintentional destruction during lawn mowing, building repairing or accidental trampling when someone walked through the site. Trap flooding in the riparian sites has occurred as well. The event table in the DwC archive contains the actual traps number (intact ones) for each sampling event (dwc: samplingEffort). We tended to set the number of traps in multipliers of 5 or 10, but in some cases, the installation of new traps to replace the damaged ones was not possible, because of which the line of traps in a particular plot was shortened. In some sample plots (07-EBCg, 07-GrR, 09-Vet), traps were added after the first sampling when vegetation development has shown that installed traps did not cover the full diversity of the site.
So, in some cases, consecutive sampling events within one survey were based on different amounts of the traps. Dealing with the relative abundance (activity-densities) of carabids, we have consdered our data consistent and comparable with others datasets. When traps were disturbed, the seasonal sum of sampling efforts does not relate to the sampling duration as an integer value (Table 3).  Samples were sorted for carabids in the laboratory. Numerous and easily-recognisable species collected in 2003-2015 were identified by Victor Aleksanov. Specimens of those species, which were difficult to determine and all specimens collected before 2003, were identified by Sergey Alexeev. For identification, we used the following keys: Gureva and Kryzhanovskii (1965), Mandl (1983) To describe and visualise carabid assemblages, we used non-metric multidimensional scaling based on Bray-Curtis Dissimilarity (qualitative), species number and Shannon Diversity Index. This data processing was performed in vegan R package (Oksanen et al. 2020).
Step description: 1. Sample plots were chosen in different kinds of urban habitats.

2.
The beetles were sampled by pitfall traps during a whole season or, in some cases, a shorter period (1-3 months). 3.
The beetles were identified and counted. 4.
The dataset was compiled. This dataset includes raw data -the number of individuals sampled during the period between trap installation and the first sampling of two consecutive samplings. The relative abundance in units of ind./100 trap days were calculated as well.
Overall, investigations covered 13 seasons during a time span of 22 years. Unfortunately, we were not able to save all of the primary data. Therefore, we could not provide data on every sampling event for 17 surveys. For these, we have data summarised for the entire season. In such cases dwc: eventID and dwc: parentEventID are the same and sampling event means the whole season of sampling, which includes several actual events. In total, data on each sampling event are available for 41 surveys from 37 plots. In total, 189 species and 79091 specimens are included in this dataset. We identified one subspecies: Harpalus xanthopus winkleri Schauberger, 1923, but since there are no other subspecies, we consider it as a species.

Geographic coverage
In the NMDS ordination graph, two groups of samples are distinctly divided from samples of other types of habitats (Fig. 10). They are habitats of a former quarry and riparian habitats. Non-riparian forests, gardens and yards are not clearly distinguished from each other. Species richness (number of species) of surveys ranged between 24 and 84 species (Table 2). More species from diverse biotopes are riparian habitats and gardens.