Study sites
The research of harvestmen (Opiliones) was carried out at seven study sites located in the historical park of Rusovce, located in the southwestern part of the city of Bratislava. The study sites are placed approximately 1–1.4 km away from the Danube River. (Fig. 1). Currently, only the area in front of the oxbow lake Rusovské rameno is considered as the park, covering an area of approximately 16 hectares. According to Reháčková (2011), in the past, a part behind the oxbow lake Rusovské rameno also belonged to the park, forming a cohesive unit, as evidenced by the species composition of the plants. Therefore, our research was carried out in both parts within the historical boundaries of the park area. The total area of the entire park is approximately 36 hectares and represents two types of areas with two management approaches, distinguishing between the park-maintained area where more intensive management measures are implemented (study sites S1–S3) and the area with less or no management interventions (sites S4–S7), which is separated by the oxbow lake Rusovské rameno.
S1 (48°03ʹ08.40ʺ N, 17°09ʹ09.50ʺ E, 134 m a.s.l.) – represents a shrub-meadow ecotone influenced by mowing, trampling of vegetation, and the presence of invasive plant species. The tree layer (E3) is absent. The shrub layer (E2) is represented by one species – Taxus baccata 2 with a total coverage of 30%. The herbaceous layer (E1 species) is represented by 42 plant taxa with a total coverage of 100%.
S2 (48°03ʹ05.50ʺ N, 17°09ʹ19.50ʺ E, 132 m a.s.l.) – plane tree alley, with Platanus hispanica 3 in the tree layer with a total coverage of 90%. The shrub layer (E2) is represented by Acer platanoides 2, A. pseudoplatanus 2, Fraxinus excelsior 2, Sambucus nigra 2, Acer campestre 1, Cerasus avium 1, Padus avium 1, Platanus hispanica 1 and Prunus spinosa 1 with a total coverage of 75%. The herbaceous layer includes 14 plant species with a total coverage of 20%.
S3 (48°03ʹ04.0ʺ N, 17°09ʹ22.70ʺ E, 152 m a.s.l.) – a hardwood floodplain forest with Acer pseudoplatanus 2, Fraxinus excelsior 2, Quercus robur 2 and Ulmus glabra 2 in the tree layer, with a total coverage of 70%. In the shrub layer (E2), the following plant species are represented: Acer campestre 2, A. pseudoplatanus 2 and Padus avium 2, with a total coverage of 15%. The herbaceous layer (E1) is represented by 15 plant species with a total coverage of 95%.
S4 (48°03ʹ07.0ʺ N, 17°09ʹ20.30ʺ E, 150 m a.s.l.) – a hardwood floodplain forest, located near the Rusovské Rameno oxbow lake, with Fraxinus excelsior 3 and Populus alba 2 in the tree layer with a total coverage of 55%. The shrub layer (E2) is represented by Acer pseudoplatanus 3, A. campestre 2, A. platanoides 2, Euonymus europaeus 2, Crataegus monogyna 2, Swida sanguinea 2, Berberis vulgaris 1, Cerasus avium 1, Carpinus betulus 1, Padus avium 1, Rosa canina agg. 1 and Ulmus glabra, with a total coverage of 60%. The herbaceous layer consists of 20 plant taxa with a coverage of 70%.
S5 (48°03ʹ09.70ʺ N, 17°09ʹ23.70ʺ E, 127 m a.s.l.) – represents a semi-open, young stand with Betula pendula 2, Populus alba 2, Prunus insititia 2 and Juglans regia 1 in the tree layer, with a coverage of 45%. The shrub layer is represented by Acer pseudoplatanus 2, Betula pendula 2, Fraxinus excelsior 2, Pinus sylvestris 2, Salix cinerea 2, Tilia x vulgaris 2 and Carpinus betulus 1, with a total c overage of 60%. The herbaceous layer is represented by 28 plant taxa with a total coverage of 95%.
S6 (48°03ʹ11.80ʺ N, 17°09ʹ31.10ʺ E, 130 m a.s.l.) – represents a 50-year-old forest stand with Pinus nigra 3 and Tilia x vulgaris 2 in the tree layer and a coverage of 90%. The shrub layer consists of the species: Crataegus monogyna 2, Tilia x vulgaris 2 and Cotinus coggygria 1 with a coverage of 4%. The herbaceous layer consists of 13 plant species with a coverage of 8%.
S7 (48°03ʹ16.10ʺ N, 17°09ʹ11.10ʺ E, 158 m a.s.l.) – a 20-year-old forest stand with Tilia x vulgaris 3 and Acer campestre 1 in the tree layer with a total coverage of 95%. The shrub layer includes Crataegus laevigata 2, C. monogyna 2, Lonicera xylosteum 2, Acer campestre 1, A. pseudoplatanus 1, Frangula alnus 1, Ligustrum vulgare 1, Taxus baccata 1 and Tilia x vulgaris 1 with a coverage of 20%. The herbaceous layer is represented by 22 plant species with a total coverage of 75%.
Sampling
The research was conducted from 1 March 2019 to 1 April 2020. The harvestmen (Opiliones) were captured by pitfall trapping (Krajčovičová et al. 2022), using 0.5 l plastic cups (9 cm in opening diameter) with 4% formaldehyde as a fixation fluid (approximately one third of the volume). At each study site, five traps were installed in a line with a distance of at least 5 m between adjacent cups. These transects were placed in the middle of the monitored sites. The traps were emptied and refilled approximately every two weeks. The contents of five traps of each site and date was merged and treated as a composite sample per each sampling period. The obtained material was sorted in the laboratory, and the harvestmen subsequently identified to the species level according to Martens (1978) and Krajčovičová et al. (2022). Specimens were fixed in 75% ethyl alcohol and deposited at the Faculty of Natural Sciences of the Comenius University in Bratislava. The scientific nomenclature was used according to the work of Kury et al. (2023).
Concerning environmental characteristics, we opted to observe the parameters that could influence the composition of harvestman communities (Table 1).
Table 1 The analysed environmental parameters: the number of management measures observed at individual study sites (management), the number of species richness of individual layers (E1, E2, E3 species), stand canopy of individual layers (E1, E2, E3 [%]) and the study sites S1–S7
Environmental parameters
|
S1
|
S2
|
S3
|
S4
|
S5
|
S6
|
S7
|
Management
|
3
|
1
|
1
|
0
|
2
|
1
|
1
|
Age [year]
|
20
|
120
|
70
|
70
|
8
|
50
|
20
|
Litter depth [cm]
|
1.5
|
7
|
3.1
|
3
|
1.8
|
3.4
|
2.5
|
E1 [%]
|
100
|
20
|
95
|
70
|
95
|
8
|
75
|
E2 [%]
|
30
|
75
|
15
|
60
|
60
|
4
|
20
|
E3 [%]
|
0
|
90
|
70
|
55
|
45
|
90
|
95
|
E1 species
|
42
|
14
|
15
|
20
|
28
|
13
|
22
|
E2 species
|
1
|
9
|
3
|
12
|
7
|
3
|
9
|
E3 species
|
0
|
1
|
4
|
2
|
4
|
2
|
2
|
Regarding management measures, during our research, within individual study sites, we documented activities such as mowing, cutting trees, and trampling of vegetation, as well as the condition of habitats altered by human intervention in the environment: the presence of invasive plant species and the presence of monoculture forests (Table 2).
Table 2 Documented activities and habitat condition caused by ongoing management measures in the monitored area
Management
|
S1
|
S2
|
S3
|
S4
|
S5
|
S6
|
S7
|
Trampling vegetation
|
x
|
|
|
|
|
|
|
Invasive species
|
x
|
x
|
|
|
x
|
|
|
Cutting trees
|
|
|
x
|
|
x
|
|
|
Mowing
|
x
|
|
|
|
|
|
|
Monoculture
|
|
|
|
|
|
x
|
x
|
We conducted estimations of the cover of tree, shrub, and herb layers at the study sites, and sampled species occurring in individual layers, all in a sampling area of 300 m2 (30 m x 10 m). For each plant species, we assigned ecological indices (1–3) based on Tansley and Chipp (1926): 1 denoting less than 1% dominance, 2 denoting 1 to 50% dominance, and 3 denoting more than 50% dominance. The nomenclature of the vascular plants was interpreted following the Euro+Med Plantbase (Uotila 2011+). The age of the trees at the study sites (Age [year]) was determined based on historical maps and our own estimate. During our fieldwork, we measured the average depth of the litter layer (Litter [cm]).
Microclimatic data were recorded every 15 min from 1 March 2019 to 1 April 2020 using TMS-4 loggers (Wild et al. 2019) located in the centre of the study site. We had 7 data loggers in total. TMS-4 loggers measure soil temperature in 6 cm depth (T1), air temperature at ground level +2 cm (T2) and 15 cm above ground (T3). Furthermore, soil moisture is measured up to 11 cm depth, but we did not evaluate the recorded soil moisture values because some moisture sensors did not register moisture at certain times. Therefore, we wanted to avoid an incorrect interpretation of the data.
Statistical analyses
In redundancy analysis (RDA) we expressed relationship between the research variables (temperature (T1–T3), management (invasive species, trampling vegetation, mowing, cutting trees, monoculture tree plantations), E1–E3 [%], E1–E3 species, age, litter) and spatial dispersion of Opiliones species. We tested the statistical significance of the variables using the Monte Carlo permutation test in (iteration 499) the Canoco5 program (Ter Braak and Šmilauer 2012).
We performed the analysis of rarefaction curves in the programme R version 4.1.3 (R Core Team 2020).