Tomáš Hamřík

Ondřej Košulič

Impact of small-scale conservation management methods on spider assemblages in xeric grassland

Keywords: Araneae, Central European xeric grasslands, Czech Republic, functional diversity, habitat management, prescribed burning

Seminatural grasslands are among the most valuable habitats for arthropod conservation in Central Europe. The abandonment of traditional farming has caused these areas to become overgrown and homogeneous, thereby resulting in loss of arthropod biodiversity. This traditional farming therefore needs to be complemented by active conservation management methods. An important question is whether small-scale conservation management may support arthropod diversity and habitat specialists inhabiting abandoned seminatural grasslands. We investigated the effects of mowing, prescribed burning, mechanical turf disturbance, and absence of active management on species richness, functional diversity and composition, conservation value, abundance of Red List species, and assemblage composition of spiders. The management methods were applied on small-scale (4 × 5 m) patches in protected xeric grassland. Spiders were sampled using pitfall traps and sweeping during 2017 and 2018. A total of 11,634 specimens from 154 species were recorded, including many rare and threatened species. The temporal responses of spider assemblages to active conservation management depended on the particular group of spiders. Changes in assemblage composition and resulting shifts in the community weighted mean values were distinct in the second year of the experiment. Management had no significant effect on the species richness of grounddwelling spiders. Mechanical turf disturbance shifted the assemblage composition of grounddwelling spiders towards habitat generalist species. Vegetation-dwelling spiders had the highest species richness in unmanaged patches. Their functional diversity was lower in disturbed patches. Burnt patches supported species of conservation concern for both spider groups. Prescribed burning had positive results for most of the studied indicators.

Nevertheless, mechanical turf disturbance had a rather negative effect on the spider assemblages. Our results indicate that even small, patch-like interventions with minimal costs can considerably support the valuable spider assemblages of xeric grassland in the intensified landscape of Central Europe.

Introduction

In recent decades, huge worldwide biodiversity loss has been reported and intensified land use in agriculture has been a major driver of that loss [START_REF] Tilman | Forecasting Agriculturally Driven Global Environmental Change[END_REF]. During this time, humankind has changed ecosystems more profoundly and on a much larger scale than in any other period of human history. Due to changes in the land use complex, natural ecosystems have been converted to simplified, managed ecosystems [START_REF] Tscharntke | Landscape perspectives on agricultural intensification and biodiversity -ecosystem service management[END_REF][START_REF] Henle | Identifying and managing the conflicts between agriculture and biodiversity conservation in Europe-A review[END_REF]. Species-rich meadows and pastures have been transformed into large blocks of fields for crop production or they have been abandoned and overgrown by scrublands or forests [START_REF] Robinson | Post-War Changes in Arable Farming and Biodiversity in Great Britain[END_REF][START_REF] Stoate | Ecological impacts of early 21st century agricultural change in Europe -A review[END_REF]. These changes constitute the main reasons for loss of invertebrate biodiversity that plays an important role in the ecosystems' functioning [START_REF] Ausden | Habitat Management for Conservation: a Handbook of Techniques[END_REF]. Not only rare habitat specialists but common habitat generalists have also been greatly reduced in recent history [START_REF] Conrad | Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis[END_REF][START_REF] Gaston | Biodiversity and extinction: losing the common and the widespread[END_REF][START_REF] Van Dyck | Declines in Common, Widespread Butterflies in a Landscape under Intense Human Use[END_REF][START_REF] Cizek | Diversification of mowing regime increases arthropods diversity in species-poor cultural hay meadows[END_REF].

Grasslands have an important role within biodiversity protection in terms of providing valuable habitats and refuges for many organisms [START_REF] Duelli | Biodiversity evaluation in agricultural landscapes: An approach at two different scales[END_REF]. Most of the grasslands located in Central Europe are seminatural and are maintained by mowing and grazing regimes [START_REF] Pech | Differential response of communities of plants, snails, ants and spiders to long-term mowing in a small-scale experiment[END_REF]. The seminatural grasslands host high species richness of invertebrates [START_REF] Poschlod | The historical and socioeconomic perspective of calcareous grasslands -lessons from the distant and recent past[END_REF][START_REF] Duelli | Regional biodiversity in an agricultural landscape: the contribution of seminatural habitat islands[END_REF][START_REF] Littlewood | Science into practice -how can fundamental science contribute to better management of grasslands for invertebrates?: Grassland invertebrate conservation[END_REF]. Socioeconomic changes at the end of the 20th century caused a reduction in livestock numbers and thus the abandonment of seminatural pastures [START_REF] Isselstein | Agronomic aspects of extensive grassland farming and biodiversity management[END_REF]. Furthermore, traditional mowing is no longer suitable because of lower demand for forage in many areas [START_REF] Valkó | Review: Prospects and limitations of prescribed burning as a management tool in European grasslands[END_REF]. The abandonment of traditional farming has resulted in shrub encroachment and litter accumulation that causes changes in xeric habitats and thus decreases their conservation value (Jongepierová et al., 2018;[START_REF] Valkó | The challenge of abandonment for the sustainable management of Palaearctic natural and semi-natural grasslands[END_REF].

Spiders (Araneae) are present in high numbers across vegetation strata, from leaf litter to the top of the canopy. They are able to respond immediately to sudden changes in the environment [START_REF] Samu | Regional variations in agrobiont composition and agrobiont life history of spiders (Araneae) within Hungary[END_REF][START_REF] Lafage | Impact of cutting date on carabids and spiders in a wet meadow[END_REF][START_REF] Košulič | Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests[END_REF]. Variation in spider species composition between habitats is determined by the differences in vegetation structure and micro-climatic conditions such as humidity [START_REF] Entling | Niche properties of Central European spiders: shading, moisture and the evolution of the habitat niche[END_REF][START_REF] Peres | The influence of treefall gaps on the distribution of web-building and ground hunter spiders in an Atlantic Forest remnant, northeastern Brazil[END_REF][START_REF] Pinto-Leite | Non-random patterns of spider species composition in an Atlantic rainforest[END_REF][START_REF] Buchholz | Ground spider assemblages as indicators for habitat structure in inland sand ecosystems[END_REF][START_REF] Nogueira | The effects of habitat size and quality on the orbweaving spider guild (Arachnida: Araneae) in an Atlantic Forest fragmented landscape[END_REF]. Distinct differences in spider communities can be obvious even on small patches [START_REF] Samu | Scale-dependent dispersal and distribution patterns of spiders in agricultural systems: a review[END_REF][START_REF] Pearce | Influence of habitat and microhabitat on epigeal spider (Araneae) assemblages in four stand types[END_REF][START_REF] Košulič | Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests[END_REF]. Most threatened and regionally extinct spider species are mainly linked to open habitats characterized by a lack of nutrients and proper conservation management [START_REF] Tropek | Spontaneous succession in limestone quarries as an effective restoration tool for endangered arthropods and plants[END_REF][START_REF] Řezáč | Red List of Czech spiders: 3rd edition, adjusted according to evidence-based national conservation priorities[END_REF]. Therefore, spiders are commonly used as ecological indicators in order to evaluate the nature conservation value of particular sites or to evaluate the effects of changes in habitat structure caused by conservation management [START_REF] Maelfait | ): some recent developments[END_REF][START_REF] Marc | Spiders (Araneae) useful for pest limitation and bioindication[END_REF]. Within the food chain, spiders have been found to significantly affect ecosystem processes through cascading effects, and numerous foraging strategies have been evolved in spiders that result in different functional roles within different ecosystems [START_REF] Michalko | Different hunting strategies of generalist predators result in functional differences[END_REF][START_REF] Michalko | An updated perspective on spiders as generalist predators in biological control[END_REF]. Knowledge of their foraging strategies and other functional traits is useful for assessing their functional diversity [START_REF] Cardoso | Global Patterns of Guild Composition and Functional Diversity of Spiders[END_REF][START_REF] Gallé | Trait-based paradise -about the importance of real functionality[END_REF].

Compared to the traditional measure of species richness, functional diversity takes into account functional traits which may reveal changes in the community that would not be captured by species richness alone [START_REF] Tilman | Forecasting Agriculturally Driven Global Environmental Change[END_REF][START_REF] Petchey | Functional diversity: back to basics and looking forward[END_REF]. Functional traits can be any behavioral, morphological, phenological, and physiological characteristics of species that can be affected by environmental variables (Simon et al., 2016). Differences in species traits result in differences in their roles in the ecosystem, thus affecting the functions of the ecosystem [START_REF] Ricotta | CWM and Rao's quadratic diversity: a unified framework for functional ecology[END_REF][START_REF] Gallé | Trait-based paradise -about the importance of real functionality[END_REF]. Any changes in habitat that influence the distribution of these traits will consequently affect ecosystem functioning [START_REF] Díaz | Vive la différence: plant functional diversity matters to ecosystem processes[END_REF]. Therefore, evaluating the functional diversity rather than species richness, per se, provides more accurate insights into ecosystem processes [START_REF] Díaz | Vive la différence: plant functional diversity matters to ecosystem processes[END_REF][START_REF] Loreau | Linking biodiversity and ecosystems: Towards a unifying ecological theory[END_REF].

Several studies have shown mowing and intensive disturbances such as grazing to have a detrimental effect on spider diversity [START_REF] Gibson | Changes in Spider (Araneae) Assemblages in Relation to Succession and Grazing Management[END_REF][START_REF] Bell | The implications of grassland and heathland management for the conservation of spider communities: a review[END_REF][START_REF] Pétillon | Impact of cutting and sheep grazing on ground-active spiders and carabids in intertidal salt marshes (Western France)[END_REF][START_REF] Lafage | Impact of cutting date on carabids and spiders in a wet meadow[END_REF][START_REF] Řezáč | Effects of uncut hay meadow strips on spiders[END_REF][START_REF] Řezáč | Grazing as a conservation management approach leads to a reduction in spider species richness and abundance in acidophilous steppic grasslands on andesite bedrock[END_REF]. Intensive disturbances reduce vegetation structural complexity (Bell et al. 2011;Horváth et al. 2019;[START_REF] Lyons | Epigeal spider assemblage responses to vegetation structure under contrasting grazing management in upland calcareous grasslands[END_REF]. Mowing immediately kills both the spiders and potential prey while altering vegetation structure in ways that result in rapid changes of microclimate conditions [START_REF] Morris | The effects of structure and its dynamics on the ecology and conservation of arthropods in British grasslands[END_REF][START_REF] Humbert | Meadow harvesting techniques and their impacts on field fauna[END_REF][START_REF] Humbert | Impact of different meadow mowing techniques on field invertebrates[END_REF][START_REF] Cizek | Diversification of mowing regime increases arthropods diversity in species-poor cultural hay meadows[END_REF][START_REF] Mazalová | Responses of grassland arthropods to various biodiversity-friendly management practices: Is there a compromise?[END_REF]. On the one hand, prescribed burning reduce accumulated plant biomass and create open soil surface with sparse vegetation, thus provide microhabitats that support grassland specialist and xerothermic spider species [START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF][START_REF] Valkó | Review: Prospects and limitations of prescribed burning as a management tool in European grasslands[END_REF][START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF].

Otherwise, fires at a large landscape scale cause significant spider mortality [START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF]. Prescribed burning carried out on a small spatial scale adjacent to intact areas mitigates the detrimental effect of fire [START_REF] Samu | Differential ecological responses of two generalist arthropod groups, spiders and carabid beetles (Araneae, Carabidae), to the effects of wildfire[END_REF][START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF].

In order to mitigate the negative effects of local management changes on invertebrates, it is important to implement an appropriate conservation management. The open landscape of Central Europe, however, lacks knowledge on the impacts of uncommon management methods like prescribed burning of xeric grasslands to spiders, when compared with the more popular practices such as grazing and mowing (e.g., [START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF]. Furthermore, most of the studies published to date were carried out in areas that were managed by mowing or affected by fire on large spatial scales (>1 ha) (e.g., [START_REF] Samu | Differential ecological responses of two generalist arthropod groups, spiders and carabid beetles (Araneae, Carabidae), to the effects of wildfire[END_REF][START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF][START_REF] Torma | Species and functional diversity of arthropod assemblages (Araneae, Carabidae, Heteroptera and Orthoptera) in grazed and mown salt grasslands[END_REF]. Little is known about the effect of small-scale conservation management methods on spider diversity. In addition, many studies do not take into account species of conservation concern that plays an important role in ecological and conservation studies (e.g., [START_REF] Tropek | Spontaneous succession in limestone quarries as an effective restoration tool for endangered arthropods and plants[END_REF][START_REF] Košulič | Recent artificial vineyard terraces as a refuge for rare and endangered spiders in a modern agricultural landscape[END_REF].

In order to fill the abovementioned knowledge gaps, our experiment compared the effects of different conservation management methods on spider assemblages on small spatial scales in xeric grassland. In particular, we evaluated (i) species richness, (ii) functional diversity and composition, (iii) conservation value, (iv) abundance of the Red List species, and (v) assemblage composition in xeric grassland. We hypothesized that (a) small-scale management methods will affect species richness, functional diversity and composition, and assemblage composition of spiders, (b) vegetation-dwelling spiders will be more sensitive to direct effects of management methods than ground-dwelling spiders, (c) small-scale prescribed burning will support grassland specialists, and (d) more intensive disturbances will have negative effects on both spider groups.

Materials and methods

Research area and study sites

The present research was carried out at Pláně Nature Monument, Czech Republic (Fig. 1).

Pláně Nature Monument is a former pasture located in the South Moravian Region (Fig. 1;49.35139°N,16.30361°E,. The study area was traditionally used as a cow and goat pasture until half of the 1970s. After the abandonment of traditional farming, Pláně NM was preserved through conservation management like sheep grazing. Between 2009 and 2016, the whole area of Pláně NM was left without any management [START_REF] Matuška | Plán péče o přírodní památku Pláně na období 2016-2025[END_REF]. The protected area covers 11.1 ha, where the most valuable parts include xeric grassland and southward, eastward, and westward oriented slopes with scattered rocks (1 ha).

The subsoil is characterized by orthogneiss with brown forest soils. This area belongs to the phytogeographical region of Mesophyticum along the border of the Czech Republic's South Moravian and Bohemian-Moravian Highlands. The mean annual precipitation is 579 mm and the mean annual temperature is 8 °C [START_REF] Hamřík | Spiders from steppe habitats of Pláně Nature Monument (Czech Republic) with suggestions for the local conservation management[END_REF].

Three experimental sites consisting of xeric grasslands were selected within the protected area (Fig. 1): Site 1 (452-448 m a.s.l.), Site 2 (442-439 m a.s.l.), and Site 3 (435-421 m a.s.l.). There had been no management in the area since 2009, and thus the experimental sites had identical starting conditions. All sites are characterized by steep slopes with southerly (Site 1) or southeasterly (sites 2 and 3) orientations with sparse herbaceous vegetation consisting of Festuca ovina. In the small parts of the experimental sites, there are present scattered trees and shrubs including Crataegus monogyna and Prunus spinosa.

Application of management methods

Four management methods were applied in both years of the study (2017 and 2018).

These were (i) mowing, (ii) prescribed burning, (iii) mechanical turf disturbance, and (iv) nomanagement. The mowing was carried out using a string trimmer in June (cutting height approx.. 6 cm). The mown material was raked and removed from the research plots.

Prescribed burning was performed using torches with a flammable cloth and took place in early March, which was outside of the growing season and the time for main activity among invertebrates. Burning was done during a windless day when there had been frost on the previous night. Mechanical turf disturbance was carried out using a hoe, and the soil turf was vigorously disrupted. This management method can be considered as an imitation of very intensive livestock grazing and trampling. This was done at the beginning of April. In the unmanaged plots, no management actions were taken. Although we are aware that all the aforementioned active management methods are forms of disturbance, for simplicity's sake we will hereafter use the term "disturbance" in reference to the mechanical turf disturbance.

Study design and sampling

The treatments were laid out in a checkerboard arrangement (four rows and four columns) of 4 × 5 m plots. Every method of management had four replications at each site. Therefore, 16 experimental plots covering a total area of 572 m 2 (22 m × 26 m) were established per site (Fig. 1). The plots had 2 m unmanaged buffer zones between one another.

Pitfall trapping and sweep-netting were used as sampling methods to collect grounddwelling and vegetation-dwelling spiders, respectively. Pitfall traps made of 500 ml plastic cups (diameter 9 cm, depth 15 cm) without funnels and roofs were sank into the soil surface and filled with a 3-4% solution of formaldehyde and detergent as a killing and preserving agent. Two pitfall traps were placed 1 m apart from the center of each plot. In total, 32 pitfall traps were placed in each site. Sweeping was carried out inside each plot (20 sweeps along a line per plot) using a sweep net (40 cm in diameter) only during a sunny, windless day with a minimum of 17 °C (between 10:00 and 17:30).

In 2017, the pitfall traps were installed on 7 May and deactivated on 15 October. In 2018, the traps were installed on 19 April and deactivated on 21 September. Traps were emptied monthly. Sweeping was carried out on the following dates: 28 May, 14 July, and 17 August in 2017; 21 May, 23 July, and 29 September in 2018. The sampled material was preserved in 70 % ethanol, and stored in the laboratory at Mendel University in Brno, Faculty of Forestry and Wood Technology.

Environmental variables evaluation

Spiders are highly sensitive to alterations in their physical environments [START_REF] Buchholz | Ground spider assemblages as indicators for habitat structure in inland sand ecosystems[END_REF]. In order to evaluate the influence of management methods on the environmental characteristics, we measured three simple environmental variables during July 2018: a) vegetation cover, b) vegetation height, and c) proportion of bare soil. The vegetation cover was estimated as a percentage (precision = 1%) of vegetation, and the height was measured using a tape measure (precision = 0.1 cm) at five randomly selected spots (mean for the plot was then calculated) within each of the 16 experimental plots. The proportion of bare soil was estimated by eye as the percentage (precision = 1%) of bare patches without vegetation on the surface of the research plots. Values of environmental variables in each study plot are shown in Table A.1.

Species classification and ecological traits

Adult and distinguishable subadult specimens were classified to species level using the identification keys of [START_REF] Heimer | Spinnen Mitteleuropas: ein Bestimmungbusch[END_REF] and of [START_REF] Nentwig | Spiders of Europe[END_REF]. Nomenclature follows the latest version of World Spider Catalog (2019).

For the functional diversity and composition, three functional traits were chosen: body size that determines spider prey size [START_REF] Gallé | Trait-based paradise -about the importance of real functionality[END_REF], hunting strategy that reflects how spiders hunt their prey [START_REF] Wise | Spiders in ecological webs[END_REF][START_REF] Jocqué | Spider Families of the World[END_REF][START_REF] Herberstein | Spider behaviour: flexibility and versatility[END_REF], and humidity preference that describes microhabitat [START_REF] Buchar | Catalogue of spiders of the Czech Republic[END_REF].

Body size was taken as a continuous variable and defined as the mean body length in mm averaged over females taken from [START_REF] Nentwig | Spiders of Europe[END_REF]. Hunting strategies were categorized as hunters and web-builders (coded as 1 and 2, respectively) in accordance with [START_REF] Cardoso | Global Patterns of Guild Composition and Functional Diversity of Spiders[END_REF]. Finally, each spider species was classified according to its humidity preference on the ordinal scale: 1 -very dry, 2 -dry, 3 -semi-humid, 4 -humid, 5 -very humid [START_REF] Buchar | Catalogue of spiders of the Czech Republic[END_REF]. Species belonging to more categories received an average value. If the average value was between two categories, then the value was rounded off according to the ecological data obtained from Arachnobase of the Czech Spiders [START_REF] Kasal | Arachnobase of the Czech Spiders[END_REF].

The conservation value of spider assemblages was evaluated based on the Red List of Czech Spiders conservation status (Řezáč et al., 2015), which are as follows: LC (least concern), VU (vulnerable), EN (endangered), and CR (critically endangered). The presence of individual species in a sample was weighted by ranked values according to the conservation status in the Red List: LC -1, VU -2, EN -3, CR -4. As a result, each individual patch was given a score that was based on a sum representing the conservation value of those species present. This approach has been used in many ecological and conservation studies (see [START_REF] Tropek | Spontaneous succession in limestone quarries as an effective restoration tool for endangered arthropods and plants[END_REF][START_REF] Tropek | Restoration management of fly ash deposits crucially influence their conservation potential for terrestrial arthropods[END_REF][START_REF] Košulič | Recent artificial vineyard terraces as a refuge for rare and endangered spiders in a modern agricultural landscape[END_REF][START_REF] Košulič | Impact of Canopy Openness on Spider Communities: Implications for Conservation Management of Formerly Coppiced Oak Forests[END_REF]. In addition to the conservation value, the abundance of the Red List species in the given categories (LC-CR) was evaluated.

In order to evaluate the effect of the different management methods on spider assemblages in terms of their rarity, every species was classified according to degree of rareness in the Czech Republic [START_REF] Buchar | Catalogue of spiders of the Czech Republic[END_REF] as follows: VA (very abundant), A (abundant), S (scarce), R (rare), or VR (very rare).

Ecological characteristics and functional traits of recorded spider species are shown in Table A.2.

Statistical analyses

Functional diversity was evaluated using Rao index that is based on the quadratic entropy of [START_REF] Rao | Diversity and dissimilarity coefficients: A unified approach[END_REF]. This coefficient was proposed as a good candidate for an efficient index of functional diversity [START_REF] Ricotta | A note on functional diversity measures[END_REF]Botta-Dukat, 2005;[START_REF] Pavoine | The apportionment of quadratic entropy: a useful alternative for partitioning diversity in ecological data[END_REF][START_REF] Lepš | Quantifying and interpreting functional diversity of natural communities: practical considerations matter[END_REF]. The Rao index (RaoQ) is a generalized form of the Simpson index of diversity representing a probability that two randomly picked individuals within a community are functionally different [START_REF] Lepš | Quantifying and interpreting functional diversity of natural communities: practical considerations matter[END_REF]. Furthermore, the community-weighted mean (CWM) was analyzed. CWM summarizes mean trait value weighted by the relative abundances of each species in a given community [START_REF] Garnier | Plant functional markers capture ecosystem properties during secondary succession[END_REF]. Since CWM represents the 'mean' of each trait and RaoQ represents the 'dispersion' of functional traits within a given community, these two measures provide complementary insight into the relationship between community structure and ecosystem functioning [START_REF] Ricotta | CWM and Rao's quadratic diversity: a unified framework for functional ecology[END_REF].

The Rao index (RaoQ) was computed using "melodic" function [START_REF] De Bello | Functional diversity through the mean trait dissimilarity: resolving shortcomings with existing paradigms and algorithms[END_REF] and the CWM was calculated using "functcomp" function in the "FD" package [START_REF] Laliberté | FD: Measuring functional diversity from multiple traits, and other tools for functional ecology[END_REF].

Comparison of species richness, abundance of Red List species, and conservation value among the four management methods were analyzed using generalized linear mixed models (GLMMs) with Poisson distribution and log link (GLMMs-p) in the package "lme4" (Bates et al., 2020). Generalized linear mixed models (GLMMs) allow analyzing data with non-normal distribution and the presence of a random effect that quantifies variations between units [START_REF] Bolker | Generalized linear mixed models: a practical guide for ecology and evolution[END_REF]. In cases where overdispersion appeared, GLMMs with a negative binomial distribution (GLMMs-nb) within the "MASS" package were used [START_REF] Ripley | Package "MASS": Functions and datasets to support Venables and Ripley[END_REF]. This model is an alternative to the Poisson model with overdispersion [START_REF] Pekár | Moderní analýza biologických dat. 1. vydání. Zobecněné lineární modely v prostředí R. Scientia[END_REF]. Dependent variables were species richness, abundance of Red List Species, and conservation value. The explanatory variables were the management methods, and the patch position was used as a random effect. The effects of management methods on functional diversity and composition were tested by linear mixed models (LMMs). This method is intended for analysis of normally distributed data that include a random effect [START_REF] Bolker | Generalized linear mixed models: a practical guide for ecology and evolution[END_REF]. Linear mixed models with RaoQ and CWM values as the dependent variables were used with management methods as explanatory variables, and patch position as a random effect. Post-hoc comparisons among management methods were conducted with "glht" function in the "multcomp" package (Hothorn et al., 2020).

Spearman rank correlation was used to analyze associations between environmental variables. A strong negative correlation was found between vegetation cover and proportion of bare soil (Spearman correlation coefficient; rho = -0.906, P < 0.001). Thus, for further analysis, the proportion of bare soil was excluded. Effect of management methods on the vegetation cover and height, and species composition were examined by partial redundancy analysis (RDA) and canonical correspondence analysis (CCA), where the site served as a covariate. In order to exclude accidental species, only those species with > 3 individuals were selected for the analysis. RDA was used if the initial detrended correspondence analysis revealed that the longest gradient was shorter than 3, while CCA was used if the longest gradient was greater than 4 (only vegetation-dwelling spiders in 2017) [START_REF] Šmilauer | Multivariete analysis of ecological data using Canoco 5[END_REF]. For the analysis of differences in species composition in relation to the management methods, the data were log (y + 1) transformed. The significance of the effect of management methods was tested using Monte Carlo permutation tests with 999 permutations. Permutations were restricted within the blocks represented by the sites. To investigate the effect of management on the degree of rareness, the degree of rareness of each species was passively projected into RDA biplots.

Univariate analyses were performed using R (R Development Core Team, 2018), and multivariate analyses were evaluated using CANOCO 5 [START_REF] Ter Braak | Cannoco 5. Software for multivariate data exploration, testing, and summarization[END_REF]. Two traps collected in each plot throughout each year were pooled together. Subsequently, the data from both years and the two collection methods were analyzed separately.

To detect characteristic species of each management method, the indicator value analysis (IndVal; Dufrene and Legendre, 1997) was performed using "indval" function in the "labdsv" package [START_REF] Roberts | Package "labdsv": Ordination and Multivariate Analysis for Ecology[END_REF].

Results

Overview

A total of 11,634 specimens representing 25 families, 88 genera, and 154 species was collected and identified (Table A.2). Overall, 10,532 specimens (91%) including 133 species were sampled by pitfall traps and 1,102 specimens (9%) including 49 species were sampled by sweeping. The most abundant species collected by pitfall traps were Alopecosa cuneata (n = 2,603) and Pardosa palustris (n = 1,884) from family Lycosidae. From sweeping, the most abundant species were Mangora acalypha (n = 537) and Aculepeira ceropegia (n = 135) from family Araneidae. Generally, 35 mainly xerothermic species listed on the Red List of Czech spiders were found (Řezáč et al. 2015). We have discovered a valuable araneofauna composition encompassing 18 % of all species within the Czech Republic. Detailed faunistic information, including the list of species with their ecological characteristics, is available in [START_REF] Hamřík | Spiders from steppe habitats of Pláně Nature Monument (Czech Republic) with suggestions for the local conservation management[END_REF].

Three significant indicator species of ground-dwelling spiders were found (see Table A.3).

Agroeca cuprea, species that inhabits broad range of open habitats, was associated with disturbed (2017), and unmanaged patches (2018). Haplodrassus signifer, a common habitat generalist, was found as an indicator species in mown patches (2017); and Xerolycosa miniata, typical for habitats with barren surface, was identified as a characteristic species in disturbed patches (2018).

For vegetation-dwelling spiders, three significant indicator species were also identified (see Table A.3): Mangora acalypha and Aculepeira ceropegia (2017); and Mangora acalypha and Argiope bruennichi (2018). These typical grassland orb-web spiders were found as an indicator species in unmanaged patches.

Effect of management on environmental characteristics

The redundancy analysis (RDA) model revealed a significant effect of management method on vegetation cover and height (RDA, pseudo-F = 54.0, P = 0.001; Fig. 2). The first two constrained axes explained 79.4% of the variability, while the other two unconstrained axes explained 16.3% and 4.3% of the variability in the environmental variables. Disturbed patches were characterized by a high proportion of bare substrate and relatively tall vegetation, while unmanaged patches were characterized by tall vegetation with extensive cover. Burnt patches contained taller vegetation generally, but the vegetation cover was not so extensive as was that in the unmanaged patches. This management method creates patches with sparse vegetation. Mown patches had very low vegetation with extensive coverage.

Effect of management on ground-dwelling spiders in 2017

The management method did not have a significant effect on the species richness (GLMM-nb, χ 2 3 = 0.2, P = 0.976), functional diversity (LMM, χ 2 3 = 2.9, P = 0.406), CWM of body size (LMM, χ 2 3 = 5.1, P = 0.166), CWM of hunting strategy (LMM, χ 2 3 = 2.0, P = 0.580), conservation value (GLMM-p, χ 2 3 = 2.5, P = 0.477), and abundance of Red List species (GLMM-nb, χ 2 3 = 0.3, P = 0.965; Tables 1 andA.4).

The CWM of humidity differed significantly among management methods (LMM, χ 2 3 = 8.5, P = 0.036; Tables 1 andA.4). Disturbed patches had significantly higher values than unmanaged patches, but comparable to that of burnt and mown patches. There was no significant difference in the CWM of humidity between unmanaged, burnt, and mown patches (Fig. 3a).

Management method did not significantly affect the spider assemblage composition (RDA, pseudo-F = 1.1, P = 0.316). The first three (constrained) axes explained 7.0 % and the remaining (unconstrained) axes explained 16.4 % of the variability in the spider species data.

Effect of management on ground-dwelling spiders in 2018

The species richness did not differ significantly among management methods (GLMM-p, χ 2 3 = 2.9, P = 0.406; Tables 1 andA.5).

The management method did have a significant effect on functional diversity (RaoQ) (LMM, χ 2 3 = 10.2, P = 0.017; Tables 1 andA.5). The functional diversity in disturbed patches was significantly greater in comparison to the unmanaged patches, but it did not differ significantly from that in burnt and mown patches. There was no significant difference in functional diversity between unmanaged, burnt, and mown patches (Fig. 4a). There was no significant difference in CWM of body size (LMM, χ 2 3 = 2.3, P = 0.522), and CWM of hunting strategy (LMM, χ 2 3 = 0.2, P = 0.974; Tables 1 andA.5) among management methods.

The management method had a significant effect on the CWM of humidity (LMM, χ 2 3 = 14.5, P = 0.002; Table 1 andA .5). The CWM of humidity was highest in disturbed patches. The burnt, mown, and unmanaged patches had comparable CWM of humidity (Fig. 3b).

Conservation value differed significantly among management methods (GLMM-p, χ 2 3 = 11.5, P = 0.009; Tables 1 andA.5). Burnt patches had significantly higher values than disturbed patches, but it did not differ significantly from that in unmanaged and mown patches. Mown patches had significantly higher conservation value than did disturbed patches, but their values did not differ significantly from those of unmanaged. There was no significant difference in conservation value between disturbed and unmanaged patches (Fig. 4b). The abundance of Red List species varied significantly among management methods (GLMM-nb, χ 2 3 = 17.4, P < 0.001; Tables 1 andA.5). The burnt and mown patches hosted significantly greater abundance of Red List species than did disturbed patches, but their abundance did not differ significantly from those of unmanaged patches. The burnt and mown patches had comparable abundance of Red List species. Unmanaged patches had a comparable abundance of Red List species to that of disturbed patches (Fig. 4c).

Management method significantly affected the spider assemblage composition (RDA, pseudo-F = 1.8, P = 0.003; Fig. 5a). The first three (constrained) axes explained 11.1% and the remaining (unconstrained) axes explained 13.9% of the variability in the spider species data. Burnt patches were preferred by rare and threatened xerothermic species requiring early stages of succession. Patches created by other management methods were preferred mainly by very abundant species and only rarely by scarce species (Fig. 5b).

Effect of management on vegetation-dwelling spiders in 2017

Species richness differed significantly among management methods (GLMM-p, χ 2 3 = 23.4, P < 0.001; Tables 1 andA .6). Species richness was highest in unmanaged patches. The burnt, disturbed, and mown patches had comparable species richness (Fig. 6a).

The functional diversity (RaoQ) differed significantly by management method (LMM, χ 2 3 = 12.7, P = 0.005; Tables 1 andA .6). Functional diversity in unmanaged patches was significantly greater in comparison to the disturbed patches, but it did not differ from that of in burnt and mown patches. The burnt, disturbed and mown patches had comparable functional diversity (Fig. 6b). The management method did not have a significant effect on CWM of body size (LMM, χ 2 3 = 3.1, P = 0.377), CWM of humidity (LMM, χ 2 3 = 7.0, P = 0.073), and CWM of hunting strategy (LMM, χ 2 3 = 6.6, P = 0.087; Tables 1 andA .6).

There was a significant difference in conservation value among management methods (GLMM-nb, χ 2 3 = 9.4, P = 0.024; Tables 1 andA .6). Unmanaged patches had significantly higher conservation value than did disturbed patches, but it did not differ from that of in burnt and mown patches. The conservation value in burnt, disturbed, and mown patches was comparable (Fig. 6c). Management method had a significant effect on the abundance of Red List species (GLMM-p, χ 2 3 = 12.1, P = 0.007; Tables 1 andA .6). In unmanaged patches, there was a significantly greater abundance of Red List species than in mown and disturbed patches. Burnt patches hosted a significantly greater abundance of Red List species than did disturbed patches, but their abundance was not significantly different from that of mown and unmanaged patches. The abundance of Red List species in mown patches was comparable to that in disturbed patches (Fig. 6d).

Management method did not significantly affect the spider assemblage composition (CCA, pseudo-F = 1.1, P = 0.277). The first three (constrained) axes explained 7.3% and the remaining (unconstrained) axes explained 16.8% of the variability in the spider species data.

Effect of management on vegetation-dwelling spiders in 2018

The management method did not have a significant effect on the species richness (GLMM-p, χ 2 3 = 5.9, P = 0.118), functional diversity (LMM, χ 2 3 = 4.7, P = 0.198), conservation value (GLMM-p, χ 2 3 = 6.4, P = 0.095), and abundance of Red List species (GLMM-nb, χ 2 3 = 3.4, P = 0.333; Tables 1 andA.7).

There was a significant difference in CWM of body size among management methods (LMM, χ 2 3 = 20.4, P < 0.001; Tables 1 andA.7). Unmanaged and disturbed patches had significantly higher values than did burnt and mown patches. The values in burnt and mown patches were comparable (Fig. 7a). The CWM of humidity differed significantly by management method (LMM, χ 2 3 = 28.3, P < 0.001; Tables 1 andA.7). In mown patches, there was the lowest CWM of humidity. The values in unmanaged, burnt and disturbed patches were comparable (Fig. 7b). The management method did not have a significant effect on CWM of hunting strategy (LMM, χ 2 3 = 7.3, P = 0.062; Tables 1 andA.7).

Management methods had significant effect on spider assemblage composition (RDA, pseudo-F = 3.5, P = 0.001; Fig. 8a). The first three (constrained) axes explained 20.1% and the remaining (unconstrained) axes explained 25.9% of the variability in the spider species data. Burnt patches were preferred by scarce Evarcha laetabunda that require sparse vegetation in xerothermic habitats. The presence of the species found in burnt patches also correlated positively with that of species inclining toward unmanaged patches (Fig. 8b).

Discussion

The study location had gone 7 years without a management regime, and this allowed us to apply selected management methods into plots with advanced stages of succession and accumulated plant biomass. Thus, all experimental plots were in an equivalent state at the start of the experiment. This provided an opportunity to study the responses of spider assemblages to ecological succession mediated by various conservation management methods in small experimental plots. Furthermore, due to the relatively high number of Red List species (N = 35), we were able to determine which management method supported the formation of microhabitats providing environmental conditions suitable for these rare and threatened species of spiders.

Effect on environmental variables

The individual management methods created differences in vegetation structural complexity, and this indirectly affected studied indicators. Unmanaged patches were characterized by tall, dense vegetation with accumulated biomass. These habitats include wet microhabitats and plant litter that together create habitat conditions providing a supply of food sources and shelters for invertebrates [START_REF] Lepš | Nutrient status disturbance and competition: an experimental test of relationships in a wet meadow[END_REF]. Contrary to unmanaged patches, disturbed patches contained a large proportion of bare substrate and very sparse vegetation cover. These patches can be compared to habitats maintained by very intensive livestock grazing and trampling. Mown patches contained low-height vegetation with relatively extensive cover.

Mowing also causes changes in the temperature and humidity of a given habitat [START_REF] Lepš | Nutrient status disturbance and competition: an experimental test of relationships in a wet meadow[END_REF].

Prescribed burning created patches with early stages of succession, but there was minimal vegetation removal. Therefore, the burnt patches were characterized by microhabitats with taller vegetation and bare soil. In burnt habitats, high plant diversity and large proportion of patches with flowering vegetation are present [START_REF] Lunt | Variation in flower production of nine grassland species with time since fire, and implications for grassland management and restoration[END_REF][START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF]. Less vegetation cover and lower height likely allow greater light access, and that supports microhabitats suitable for germination of many plant species [START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF].

Effect on ground-dwelling spiders

In the first year, the experiment revealed no differences in spider assemblages across most response variables, the exception was CWM of humidity.

The species richness was comparable across individual management methods. In a study initiated 2.5 years after an extensive fire, Samu et al. ( 2010) also found comparable species richness in both large burnt blocks (1 ha) and unburnt blocks. In several studies, the species richness of ground-dwelling spiders has been found to be slightly higher in unmanaged grasslands, and this has been attributed to the greater presence of prey and habitat heterogeneity (e.g., [START_REF] Cizek | Diversification of mowing regime increases arthropods diversity in species-poor cultural hay meadows[END_REF].

Most species of conservation concern preferred the burnt patches. This was confirmed also by high conservation values and abundances of the Red List species. The burnt patches were preferred by rare xerothermic species (e.g., Alopecosa striatipes and Thanatus arenarius). These species require bare soil with sparse vegetation [START_REF] Buchar | Catalogue of spiders of the Czech Republic[END_REF]. This corresponds with the findings of a large-scale study (1 ha blocks) wherein xerothermic species such as Arctosa perita and Alopecosa cursor were found more abundantly in burnt patches [START_REF] Samu | Differential ecological responses of two generalist arthropod groups, spiders and carabid beetles (Araneae, Carabidae), to the effects of wildfire[END_REF]. Open habitat specialists are more abundant in medium-grown swards than in full-grown and recently mown vegetation [START_REF] Mazalová | Responses of grassland arthropods to various biodiversity-friendly management practices: Is there a compromise?[END_REF]. [START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF] found that spider assemblages alter in the predominance of xerothermic species such as Drassodes pubescens, Thanatus arenarius, and Zelotes electus in habitats affected by fires within 3 years after the fires. Our results already revealed the same pattern in the second year of the experiment due to the small-scale approach and presence of source habitats in the vicinity. It must be noted that species inclining towards unmanaged patches were mostly widespread generalists, as confirmed also by [START_REF] Cizek | Diversification of mowing regime increases arthropods diversity in species-poor cultural hay meadows[END_REF]. In disturbed patches, the conservation value and abundance of the Red List species were low. In the first year of the experiment, the disturbed patches had higher CWM of humidity than unmanaged patches. In the second year of the experiment, the CWM of disturbed patches became highest among management mehods. Disturbed patches were only preferred by a few generalists (e.g., Cicurina cicur, Pisaura mirabilis). Thus, this pattern was probably caused by assemblage composition changes towards habitat generalists in disturbed patches, whereas xerothermic grassland specialists preferred less intensively managed patches. It was also supported by the detection of Agroeca cuprea as the indicator species in disturbed patches in the first year of the experiment but in unmanaged patches in the second year. Intensive soil disturbances have a negative effect on grassland specialist spider species [START_REF] Batáry | Are spiders reacting to local or landscape scale effects in Hungarian pastures?[END_REF][START_REF] Pétillon | Impact of cutting and sheep grazing on ground-active spiders and carabids in intertidal salt marshes (Western France)[END_REF]Horváth et al., 2019). Disturbed patches had also greater functional diversity than did unmanaged patches. In early successional stages, rapid colonization from surrounding habitats and mobility from adjacent plots bring a number of species with unique combinations of functional traits [START_REF] Hodeček | Post-industrial areas as successional habitats: Long-term changes of functional diversity in beetle communities[END_REF]. In our study, it was obviously a result of colonization by various habitat generalists. Mean spider body size and proportion of webbuilders were comparable among management methods. However, previous studies showed that ground-dwelling spiders with large body size favor less intensively managed patches [START_REF] Bell | The implications of grassland and heathland management for the conservation of spider communities: a review[END_REF][START_REF] Birkhofer | Optimizing arthropod predator conservation in permanent grasslands by considering diversity components beyond species richness[END_REF]. Our result may be explained by the low presence of web-builders captured by pitfall traps and the dominance of ground-dwelling spiders with comparable body size.

Effect on vegetation-dwelling spiders

In contrast to ground-dwelling spiders, the vegetation-dwelling spiders already responded to the management in the first year of the experiment. Management causes immediate changes in vegetation structure and direct mortality of vegetation-dwelling arthropods (e.g., [START_REF] Torma | Species and functional diversity of arthropod assemblages (Araneae, Carabidae, Heteroptera and Orthoptera) in grazed and mown salt grasslands[END_REF]. Nonetheless, assemblage composition changes and consequent shifts in CWM values were observed in the second year of the experiment.

The vegetation-dwelling spiders had the highest species richness in unmanaged patches.

The web-building spiders are limited by the presence of vegetation structural complexity that allows them to attach their webs [START_REF] Greenstone | Determinants of web spider species diversity: vegetation structural diversity vs. prey availability[END_REF][START_REF] Mcnett | Habitat selection in a large orb-weaving spider: vegetational complexity determines site selection and distribution[END_REF]Jiménez-Valverde and Lobo, 2007). Denser vegetation in unmanaged patches also provides shelters and microhabitats with suitable conditions for hibernation and female cocoon formation (De Keer and [START_REF] De Keer | Life history of Oedothorax fuscus (Blackwall, 1834) Araneae, Linyphiidae in a heavily grazed pasture[END_REF][START_REF] De Keer | Horizontal distribution of the spider fauna of intensively grazed pastures under the influence of diurnal activity and grass height[END_REF][START_REF] Bayram | Winter abundance and diversity of lycosids (Lycosidae, Araneae) and other spiders in grass tussocks in a feld margin[END_REF]. It is evident that the vegetation-dwelling arthropods are negatively affected by intensive disturbances [START_REF] Torma | Species and functional diversity of arthropod assemblages (Araneae, Carabidae, Heteroptera and Orthoptera) in grazed and mown salt grasslands[END_REF]. Conversely, less-intensive management creates more complex communities with niches suitable for vegetation-dwelling spiders [START_REF] Bell | The implications of grassland and heathland management for the conservation of spider communities: a review[END_REF].

Prescribed burning and no-management had a positive effect on the conservation value and abundance of Red List species. Conversely, disturbed patches showed significantly lower abundance of Red List species. Intensive management in xeric grasslands reduces the proportions of rare and threatened web-building spiders [START_REF] Gibson | Changes in Spider (Araneae) Assemblages in Relation to Succession and Grazing Management[END_REF]. Mown patches hosted lower abundance of Red List species than unmanaged patches. Vegetation-dwelling spiders require heterogeneous vegetation structure that is low due to the direct effect of mowing [START_REF] Bucher | Contrasting effects of habitat fragmentation, population density, and prey availability on body condition of two orb-weaving spiders[END_REF]. Evarcha laetabunda, which belongs to rare and threatened species of spiders, were inclined to burnt and unmanaged patches. This species is dependent on the presence of vegetation, which is lacking in disturbed and mown patches.

The negative impact of burning in terms of immediate mortality and habitat destruction is generally known for large-scale fires (e.g., [START_REF] Nemkov | Impact of fires on the fauna of terrestrial arthropods in protected steppe ecosystems[END_REF][START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF] but not for application on a small spatial scale as in our study.

The disturbed patches had lower functional diversity than unmanaged patches. These patches were populated by functionally more similar species, which led to the lower functional diversity. Disturbed and unmanaged patches hosted species with larger mean body size than burnt and mown patches. Also, the ordination analysis shows the preference of dominant large spider species Aculepeira ceropegia for unmanaged and disturbed patches.

This species can be found in both intact and anthropogenically disturbed habitats [START_REF] Buchar | Catalogue of spiders of the Czech Republic[END_REF]. Furthermore, Argiope bruennichi was found as indicator species in unmanaged patches. However, the occurrence of larger-sized species in disturbed patches is in contrast to the previous finding that revealed a dominance of small species of web-building spiders in heavily grazed grasslands [START_REF] Gibson | Changes in Spider (Araneae) Assemblages in Relation to Succession and Grazing Management[END_REF]. It may be due to changes in prey availability of Aphididae, Psylloidea, and Collembola which are among the most important prey of small-sized spiders [START_REF] Alderweireldt | Prey selection and prey capture strategies of linyphiid spiders in high-input agricultural fields[END_REF][START_REF] Lawrence | Spider predation on forest-floor Collembola and evidence for indirect effects on decomposition[END_REF][START_REF] Pekár | Biological control in winter: novel evidence for the importance of generalist predators[END_REF]. Grassland management affects habitat structure and these changes can cause significant mortality of these insect groups [START_REF] Purvis | The influence of sward management on foliage arthropod communities in a ley grassland[END_REF][START_REF] Ausden | Habitat Management for Conservation: a Handbook of Techniques[END_REF].

Furthermore, intraguild predation is typical for habitats with low structural complexity [START_REF] Schmidt | Opportunistic predator prefers habitat complexity that exposes prey while reducing cannibalism and intraguild encounters[END_REF]. However, complex-structured habitats provide a refuge for predators from intraguild predation [START_REF] Finke | Spatial refuge from intraguild predation: implications for prey suppression and trophic cascades[END_REF]. Therefore, we assume that the exclusion of potential small-sized prey or intraguild predation could lead to the exclusion of small spider species in disturbed patches. In conjunction with other studies [START_REF] Simons | Multi-taxa approach shows consistent shifts in arthropod functional traits along grassland land-use intensity gradient[END_REF][START_REF] Torma | Species and functional diversity of arthropod assemblages (Araneae, Carabidae, Heteroptera and Orthoptera) in grazed and mown salt grasslands[END_REF] our results also confirm that mechanical mowing can harm large species of arthropods. Furthermore, larger species that have a longer life cycle can be easily disrupted by management methods such as mowing (Simons et al., 2006). Small species from the family Linyphiidae, such as Agyneta rurestris and Tenuiphantes flavipes, had a tendency towards burnt patches. Increased bare soil in burnt patches is colonized by pioneer linyphiid species [START_REF] Merrett | Changes in the ground-living spider fauna after heathland fires in Dorset[END_REF]. We can conclude that while mowing harmed large web-building spiders, prescribed burning offered suitable microhabitats for small spider species. Mowing causes significant changes in microclimatic conditions that result in lower humidity [START_REF] Bell | The implications of grassland and heathland management for the conservation of spider communities: a review[END_REF]. The lowest CWM of humidity in mown patches may be the result of unsuitable conditions for species with high humidity preferences.

Suggestions for management implications

Based on our results, the no-management and small-scale prescribed burning are suitable conservation methods to maintain spider diversity. Therefore, their combination also appears to be appropriate. Prescribed burning creates patches that support species of conservation concern [START_REF] Nemkov | Impact of fires on the fauna of terrestrial arthropods in protected steppe ecosystems[END_REF][START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF][START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF] while unmanaged patches offer habitats with high abundance of prey, shelters, and suitable microclimate [START_REF] Bell | The implications of grassland and heathland management for the conservation of spider communities: a review[END_REF][START_REF] Cattin | The impact of mowing as a management strategy for wet meadows on spider (Araneae) communities[END_REF]. Our experiment shows that small-scale prescribed burning is a management method that achieves comparable or better results than does traditional mowing in xeric grassland. Homogeneous mowing without hay-removal usually accumulates biomass (e.g., [START_REF] Noordijk | Effects of vegetation management by mowing on ground-dwelling arthropods[END_REF]Cizek et al., 2013), which conversely can be reduced by prescribed burning [START_REF] Niwa | Influence of prescribed fire on carabid beetle (Carabidae) and spider (Araneae) assemblages in forest litter in southwestern Oregon[END_REF]. On the other hand, there are studies showing adverse effects of burning on spider diversity (e.g., [START_REF] Polchaninova | Recovery of Spider Communities After a Spontaneous Summer Fire in the Forb-Bunchgrass Steppe of Eastern Ukraine[END_REF]. To avoid the adverse effect, it is important to carry out the prescribed burning during the dormant season on a small scale within patches adjacent to intact areas (Prishutov and Arzanova, 2008;[START_REF] Samu | Differential ecological responses of two generalist arthropod groups, spiders and carabid beetles (Araneae, Carabidae), to the effects of wildfire[END_REF][START_REF] Valkó | Supporting biodiversity by prescribed burning in grasslands -A multi-taxa approach[END_REF]. Unlike the mown patches, the burnt patches have relatively tall vegetation, which offers a refuge for vegetation-dwelling spiders.

Our experiment is consistent with previous studies showing that intensive disturbance of habitats such as by soil disruption and/or intensive grazing has negative impacts on arthropods (De Keer andMaelfait, 1988, Gibson et al., 1992;[START_REF] Belsky | Effects of grazing, competition, disturbance and fire on species composition and diversity in grassland communities[END_REF][START_REF] Pétillon | Impact of cutting and sheep grazing on ground-active spiders and carabids in intertidal salt marshes (Western France)[END_REF][START_REF] Horváth | Spiders are not less diverse in small and isolated grasslands, but less diverse in overgrazed grasslands: A field study (East Hungary, Nyírség)[END_REF][START_REF] Van Klink | Effects of large herbivores on grassland arthropod diversity[END_REF]. In accordance with our results, we suggest that one-time prescribed burning could be performed as a means of restoring recently homogeneous xeric grasslands that had been abandoned from former traditional farming [START_REF] Reidsma | Impacts of land-use change on biodiversity: An assessment of agricultural biodiversity in the European Union[END_REF]. It is important to note that burning increases the dominance of expansive Calamagrostis epigejos, thus prescribed burning is inappropriate in grasslands where this plant species is present [START_REF] Házi | Seminatural grassland management by mowing of Calamagrostis epigejos in Hungary[END_REF][START_REF] Deák | Grassland fires in Hungary-Experiences of nature conservationists on the effects of fire on biodiversity[END_REF]. In such context, it is more appropriate to combine prescribed burning with mowing in order to reduce patches with expansive plants such as Calamagrostis epigejos that in general threaten biodiversity of most xeric grasslands in Europe [START_REF] Henning | Year-round cattle and horse grazing supports the resto-ration of abandoned, dry sandy grassland and heathland commu-nities by suppressing Calamagrostis epigejos and enhancing species richness[END_REF]. Prescribed burning on a small spatial scale, together with mowing, has the potential to enhance the habitat heterogeneity, thus supporting the overall biodiversity [START_REF] Ausden | Habitat Management for Conservation: a Handbook of Techniques[END_REF]. It is necessary to leave intact some small parts within managed grasslands to maintain a habitat mosaic at various stages of succession in order to support arthropods for which regular disturbances are unsuitable [START_REF] Batáry | Effect of conservation management on bees and insect-pollinated grassland plant communities in three European countries[END_REF]. We suggest diversification of conservation management methods to be conducted in parts of a given area throughout the year. However, it should be noted that in some regions, returning to traditional farming in grasslands is not feasible, or the implementation of such conservation management is high-cost [START_REF] Poschlod | The historical and socioeconomic perspective of calcareous grasslands -lessons from the distant and recent past[END_REF][START_REF] Valkó | Review: Prospects and limitations of prescribed burning as a management tool in European grasslands[END_REF]. For these reasons, we suggest that small-scale prescribed burning can be a suitable low-cost substitute for uneconomical management methods such as mowing. We also assume that such debatable conservation practices as small-scale prescribed burning in protected grasslands should be seen not as a threats to the environment, but as acceptable substitutes for traditional farming methods that are no longer in use, but which also have historically helped sustain a high level of biodiversity in the European landscape [START_REF] Ausden | Habitat Management for Conservation: a Handbook of Techniques[END_REF].

Conclusions

Our results show that patches created by small-scale conservation management may enhance spider diversity in xeric grasslands. We observed high spider species turnover among small-scale (4 × 5 m) patches created by various management methods. These changes in such notably small areas subject to various management methods highlight the importance of habitat complexity even on limited patches of grassland habitats. Our results indicate that prescribed burning had a positive effect on the species of conservation concern. On the other hand, unmanaged patches showed a positive effect on species inhabiting the vegetation. Thus, it seems that no-management and prescribed burning are most appropriate for the management of xeric grasslands to support spider occurrence. Surprisingly, mowing had in some cases unfavorable values comparable to those when mechanical turf disturbance was carried out. Based on these results, properly conducted prescribed burning can achieve better results than does more costly mowing. Therefore, it could be a cost-effective alternative management tool for conserving grassland biodiversity. We suggest that small-scale management methods may be useful for supporting biodiversity in xeric grasslands within landscapes under intense human land use that formerly had been maintained by traditional means. Finally, the results of this study may be useful to conservation organizations and government institutions in considering whether prescribed burning is an effective conservation method for use on European xeric grasslands. Nevertheless, prescribed burning needs to be implemented by well-trained conservation managers who have proper knowledge of the given habitats, with the assistance of firefighters to avoid possible negative effects.

Table A.7. Effect of prescribed burning (B), mechanical turf disturbance (D), mowing (M), no-management (N) on species richness, abundance of Red List species, conservation value, functional diversity and composition of vegetation-dwelling spiders in 2018. Effects of management methods were tested using GLMMs and LMMs. Significant results are marked with boldface.

Figure legends

Fig. 1. Map of the study area in the Czech Republic (red square on map) and sites with rectangles (4 × 5 m) where each management method was applied (ESRI, 2013). The map background was downloaded from free maps platform system (http://www.freepik.com) and modified in Adobe Photoshop CS6. Different letters indicate statistically significant differences (P < 0.050).

Fig. 2 .

 2 Fig. 2. Redundancy analysis ordination diagram (RDA) revealing relationship between

Fig. 3 .

 3 Fig. 3. Effect of conservation management methods on CWM of humidity preference of

Fig. 4 .

 4 Fig. 4. Effect of conservation management methods on diversity of ground-dwelling spiders

Fig. 5 .

 5 Fig. 5. Redundancy analysis ordination diagrams summarizing differences within ground-

Fig. 6 .

 6 Fig. 6. Effect of conservation management methods on diversity of vegetation-dwelling

Fig. 7 .

 7 Fig. 7. Effect of conservation management methods on CWM of a) body size, and b)

Fig. 8 .

 8 Fig. 8. Redundancy analysis ordination diagrams summarizing differences within vegetation-

Table 1 .

 1 Species richness, abundance of Red List species, conservation value, functional diversity and composition (mean values + SD) of ground-dwelling and vegetation-dwelling spiders in relation to individual management methods. Effects of management methods were tested using GLMMs and LMMs. Significant results are marked with boldface.

	Measured indicators	Disturbance No-management Mowing (N=12) (N=12) (N=12)	Burning (N=12)	p
	Ground-dwelling 2017
	Species richness	26.67 ± 7.46 26.00 ± 7.32	26.08 ± 5.32 27.0 ± 7.94	0.976
	Red List species	22.67 ± 12.67 22.67 ± 14.99	22.17 ± 10.58 23.17 ± 13.37 0.965
	Conservation value	10.75 ± 3.72 10.25 ± 2.99	10.42 ± 3.00 12.25 ± 4.07 0.477
	FD (RaoQ)	0.11 ± 0.03	0.11 ± 0.02	0.12 ± 0.03	0.12 ± 0.04	0.406
	CWM body size	7.24 ± 0.45	7.47 ± 0.36	7.51 ± 0.56	7.33 ± 0.27	0.166
	CWM humidity	2.14 ± 0.26	1.96 ± 0.22	2.00 ± 0.19	2.05 ± 0.24	0.036
	CWM hunting	1.04 ± 0.03	1.03 ± 0.04	1.03 ± 0.03	1.05 ± 0.05	0.580
	Ground-dwelling 2018
	Species richness	19.42 ± 4.80 20.17 ± 4.39	21.17 ± 3.74 22.42 ± 4.64 0.406
	Red List species	11.75 ± 9.16 16.92 ± 7.61	17.50 ± 9.46 23.33 ± 14.97 < 0.001
	Conservation value	7.33 ± 3.75	9.50 ± 3.15	10.50 ± 2.97 11.33 ± 3.63 0.009
	FD (RaoQ)	0.10 ± 0.02	0.08 ± 0.02	0.09 ± 0.02	0.09 ± 0.01	0.017
	CWM body size	7.94 ± 0.54	7.87 ± 0.43	7.87 ± 0.29	8.03 ± 0.46	0.522
	CWM humidity	1.71 ± 0.25	1.51 ± 0.26	1.52 ± 0.13	1.55 ± 0.21	0.002
	CWM hunting	1.02 ± 0.02	1.02 ± 0.02	1.02 ± 0.02	1.02 ± 0.01	0.974
	Vegetation-dwelling 2017
	Species richness	2.08 ± 1.62	6.33 ± 3.17	3.08 ± 1.16	3.75 ± 1.60	< 0.001
	Red List species	0.42 ± 0.79	3.50 ± 2.94	1.17 ± 0.94	2.17 ± 2.04	0.007
	Conservation value	0.58 ± 1.08	2.08 ± 1.31	1.25 ± 0.97	1.67 ± 1.44	0.024
	FD (RaoQ)	0.08 ± 0.10	0.20 ± 0.08	0.13 ± 0.07	0.14 ± 0.05	0.005
	CWM body size	5.49 ± 1.12	6.42 ± 1.39	6.10 ± 2.49	5.55 ± 1.32	0.377
	CWM humidity	1.98 ± 0.39	2.14 ± 0.35	1.79 ± 0.40	1.91 ± 0.22	0.073
	CWM hunting	1.87 ± 0.21	1.72 ± 0.16	1.65 ± 0.28	1.69 ± 0.27	0.087
	Vegetation-dwelling 2018
	Species richness	3.75 ± 1.48	5.33 ± 1.16	3.58 ± 1.50	4.83 ± 1.33	0.118
	Red List species	1.50 ± 1.68	3.08 ± 2.81	2.00 ± 2.70	2.83 ± 2.98	0.333
	Conservation value	1.08 ± 1.16	2.42 ± 1.16	1.83 ± 1.40	1.92 ± 1.44	0.095
	FD (RaoQ)	0.10 ± 0.04	0.16 ± 0.07	0.12 ± 0.09	0.13 ± 0.72	0.198
	CWM body size	7.52 ± 1.70	7.31 ± 1.00	5.57 ± 0.78	6.29 ± 1.38	< 0.001
	CWM humidity	2.14 ± 0.26	2.17 ± 0.17	1.78 ± 0.14	2.09 ± 0.19	< 0.001
	CWM hunting	1.96 ± 0.05	1.88 ± 0.12	1.87 ± 0.11	1.87 ± 0.10	0.062

0,009 2017 Aculepeira ceropegia 0,355 0,009 2017 Aculepeira ceropegia 0,420 0,011 2018 Argiope bruennichi 0,333 0,014 2017 Ground-dwelling spiders Herb-dwelling spiders

Acknowledgements

The authors would like to thank Radek Michalko, Jan Šipoš, Tomáš Kudláček, and Daniel Volařík for help with statistical analysis; Igor Malenovský and Julien Pétillon for useful comments and suggestions; Denise Paulina V. Doble for the English proofreading; and Petr Dolejš for determination and revision of spider taxa that were difficult to identify. We likewise extend our warm appreciation to Jaroslav Knotek (South Moravian Regional

Authority), David Lacina (Kuřimská Nová Ves), Libor Sedlák and AGRO Skalka for enabling us to carry out our experiments at Pláně Nature Monument; friends and family and the members of ZO ČSOP Eresus and ZO ČSOP Náměšťské rybníky for their assistance during fieldwork; and Kamila Surovcová and Luboš Staněk for sorting materials. We also thank the academic editor Santiago Poggio and three anonymous reviewers for their useful comments and correction of the manuscript. The study was financially supported by the Specific University Research Fund of the Faculty of Forestry and Wood Technology, Mendel University in Brno (LDF_PSV_2017004/2017). Conservation status: CR (critically endangered), EN (endangered), VU (vulnerable), LC (least concern); Degree of rareness: VA (very abundant), A (abundant), S (scarce), R (rare), VR (very rare); Hunting strategy: active hunters (1), web-builders (2); Humidity preference: very dry (1), dry [START_REF] Entling | Niche properties of Central European spiders: shading, moisture and the evolution of the habitat niche[END_REF], semi-humid (3), humid (4), very humid (5); Body size (mm).

Appendices