Exploring the effects of habitat management on grassland biodiversity: A case study from northern Serbia

habitat type, with open grasslands—including sands, steppes, meadows, and marshes—inter- sected by woodlands and forests. As established by Butorac and Panjković [28], Aceri tatarici- Quercion and Festucion rupicolae mosaics have historically formed the climate-zonal vegeta- tion of this area. However, Convallario-Quercetum roboris woods are currently present as rem- nants of former woodlands, while its secondary developed scrub (Pruno spinosae- Crataegetum) predominated [29]. Due to the vicinity of groundwater, continental saturation of soil with moisture, and specific relief with many micro-depressions, riparian forests and thickets, such as white poplar (ass. Populetum albae) or grey sallow (ass. Salicetum cinereae) stands, as well as marsh vegetation (ass. Carici elatae-Fraxinetum angustifoliae), remain in small fragments [29, 30]. Despite this evident decline in native habitats, it took almost two decades of work and har- monisation of conservation policies to finally have this area protected as a region of forest con- servation value in 1982. Subsequent scientific research has shown that the area is home not only to forest species, but also to extremely small populations of species of international impor- tance (spring meadow saffron Colchicum bulbocodium subsp. Versicolor, lesser blind mole-rat Spalax leucodon) that are restricted to small areas. In line with the latest trends in nature con- servation and guided by the advances in scientific knowledge, part of the area that had previ-

ously been converted into orchards and vineyards was ploughed up in 2002. This provided an opportunity to revise the protection status and in 2003 the area was declared an Outstanding natural landscape. Active management measures were then developed and successively intro- duced. In the subsequent period, undergrowth was removed and large areas of Subotica Sands were mowed and levelled. Alongside these measures, in 2017, sheep and goat herds were allowed to actively graze in this area. In an event of a long winter, grazing was supplemented by regular mowing. Currently, this area serves as pasture for about 270 sheep per 230 ha, which are guided by shepherds and are permitted to roam freely. After two decades, the afore- mentioned active management measures were successful in the restoration of the populations of the most endangered species, thus creating the conditions for the reintroduction of some species that have previously thrived in this area (e.g., European ground squirrel Spermophilus citellus). Thus, this study site was not only suitable for the current investigation, it is also in line with the EU regulations, within which Pannonian sands and steppes are described as natu- ral habitats with priority [28]. Study design For the present investigation, we selected seven sampling sites, each covering an area of one hectare, all situated within the Level I: Total/Strict protection regime (constituting 8.32% of the Subotica Sands area). However, these sites varied in terms of the management practices

they had experienced in the past two decades. To provide more insight into the habitat charac- teristics, we categorized them into three groups: three sites were subject to mowing (M), three to grazing (G), and one served as a control site ©, having no history of specific management measures. During our fieldwork, we employed habitat classification to further specify the char- acteristics of each site according to National classification of Republic of Serbia (Table 1). Additionally, we established a buffer zone, extending 150 meters from the boundaries of each sampling site. This buffer zone provided a broader-scale perspective, allowing us to assess the impact of habitat features on bird and pollinator diversity. Furthermore, this approach allowed us to quantify parameters such as distance to the nearest trees, overall tree and shrub coverage, and the proportion of tree and shrub coverage within and outside of the study sites. The infor- mation required for these calculations was obtained by interpreting orthophoto images sourced from Google Earth Pro version 7.3.3.7786. PLOS ONE Effects of habitat management on biodiversity PLOS ONE | https://doi.org/10.1371/journal.pone.0301391 March 28, 2024 4 / 19