Xerothermic pavements – a meadow biodiversity richness. Jaworzno case study

Xerothermic pavements are non-forested plant communities developing on sunlit slopes composed of dry limestone substrates, occurring particularly in south and south-eastern Europe, in areas characterised by dry and warm summers [Poschlod, WallisDeVries, 2002; Perzanowska, Kujawa-Pawlaczyk, 2004]. The pavements comprise many protected and valuable, often relict, plant and animal species, and are considered as some of the richest plant communities. However, they are also the most endangered element of the natural environment of Europe, including their unique flora and fauna [Pärtel et al., 2005]. In Poland, xerothermic communities occur in fragmented sites, covering sunlit and dry, rich in calcium habitats –usually south or west dipping exposed slopes [Monitoring gatunków i siedlisk przyrodniczych, 2019a].

As thermophilic communities, xerothermic pavements occur as small patches in entire Poland, however, only in areas with specific climate-habitat conditions. These communities occur in extreme habitats: steep escarpments covered with scree, river valley slopes and rock exposures [Barańska, Jermaczek, 2009]. Such pavements have been documented in the Lower Odra river valley, Warta river valley, Lower Vistula river valley, Nida Basin, Kielce-Sandomierz Upland, Lublin Upland, Kraków Upland, southern part of Kraków-Częstochowa Upland, eastern part of Silesian Upland, Western Pieniny, Kaczawa Foothills, Wałbrzych Foothills, Sowie Mountains, Ślęża Massif and Strzegom Hills [Celiński, Filipek, 1958; Radomski, Jasnowska, 1964, 1965; Filipek, 1974a, 1974b; Ćwikliński, 1982; Friedrich, 2000; Friedrich, Semczyszyn, 2002; Medwecka-Kornaś, Kornaś, 1972]. The xerothermic pavements from Poland have been assigned to habitat 6210, to the Fetusco-Brometea class with regard to phytosociology [Monitoring gatunków i siedlisk przyrodniczych, 2019b].

Formation of pavements in Europe was related to the retreat of the ice-sheet at the end of the last glaciation, due to which, areas without forest communities became colonised by thermophilic plants from southern and eastern Europe and Asia. This migration was possible due to climate warming, whereas later human activity, influencing the shrinking of forest areas, enhanced the spread of thermophilic species. Therefore, it is commonly considered that most xerothermic pavements in Poland are semi-natural habitats, whose formation was induced by several centuries of land use by humans: deforestation and removal of mid-field tree complexes, pasture management and meadow mowing. Xerothermic pavements were treated as less valuable grasslands, used for grazing animals enduring poorly accessible and poorer quality fodder: sheep and goats [Bąba, 1999; Barańska et al., 2010].

Xerothermic pavements are rich and diverse environments, overgrown by many species of medicinal, melliferous and herbaceous plants. In terms of phytosociology, the grass communities of meadows and pavements growing on mineral substrates, including continental xerothermic pavements, communities of thermophilic pavements of south-eastern and southern Europe are subdivided into: xerothermic calciphyte rocky pavements, steppe-like loose pavements with prevalence of grass, and compact meadow steppes [Prajs, 2010]. A typical fragrance of xerothermic pavements is the effect of flowering wild thyme and meadow sage (Photography 1, below). Species characteristic of these plant communities include: spring savory (Acinos arvensis), upright bugle (Ajuga genevensis), field garlic (Allium oleraceum), snowdrop anemone (Anemone sylvestris), St Bernard’s lily (Anthericum liliago), common kidneyvetch (Anthyllis vulneraria), hairy rock-cress (Arabis hirsuta), field wormwood (Artemisia campestris), squinancywort (Asperula cynanchica), yellow bluestem (Bothriochloa ischaemum), heath false brome (Brachypodium pinnatum), clustered bellflower (Campanula glomerata), spring-sedge (Carex caryophyllea), dwarf sedge (Carex humilis), carline thistle (Carlina vulgaris) (photography 2), greater knapweed (Centaurea scabiosa) (photographs 3 and 4), Centaurea stoebe, leafless hawksbeard (Crepis praemorsa), carthusian pink (Dianthus carthusianorum) (photography 5), cypress spurge (Euphorbia cyparissias), Euphorbia serrulata, Festuca rupicola, dropwort (Filipendula vulgaris), goldilocks aster (Galatella linosyris), white bedstraw (Galium album), cross gentian (Gentiana cruciata), common rock-rose (Helianthemum nummularium), meadow oat-grass (Helictotrichon pratense), rolling Hen-and-chicks (Jovibarba sobolifera), prairie Junegrass (Koeleria macrantha), thoroughwort pennycress (Microthlaspi perfoliatum), Odontites luteus, proliferous pink (Petrorhagia prolifera), Boehmer’s cat’s-tail (Phleum phleoides), bulbous bluegrass (Poa bulbosa), Canada bluegrass (Poa compressa), hoary plantain (Plantago media), rue-leaved saxifrage (Saxifraga tridactylites), fragrant scabious (Scabiosa canescens), goldmoss stonecrop (Sedum acre), stiff hedgenettle (Stachys recta), rock dandelion (Taraxacum laevigatum) and spiked speedwell (Veronica spicata).

Photography 1

Photography 2

Photography 3

Photography 4

Photography 5

Additionally, xerothermic pavements are locations for protected species and very rare plants: dyer’s woodruff (Asperula tinctoria), Campanula bononiensis, Campanula sibirica, dwarf sedge (Carex humilis), silver carline-thistle (Carlina acaulis), field eryngo (Eryngium campestre), Erysimum hungaricum, dwarf everlast (Helichrysum arenarium), Hieracium echioides, spiny restharrow (Ononis spinosa), Orobanche lutea (Photography 6), Oxytropis pilosa, Pontechium maculatum, cowslip (Primula veris), large-flowered selfheal (Prunella grandiflora), Scorzonera purpurea, Stipa pennata subsp. joannis, and Thesium linophyllon [Piękoś-Mirkowa, Mirek, 2006; Żukowski, Jackowiak, 1995, Snowarski, 2007].

Photography 6

A characteristic feature of xerothermic plant communities is their diversity depending on the origin and enrichment in species from other habitats. Introduction of other species distinctly increases the biodiversity of these communities [Kostuch, Misztal, 2007].

The last decades have brought diminishing of areas covered by thermophilic pavements. Disappearance of pavement vegetation is caused by changes in soil use: elimination of pasture management and abandonment of animal grazing, such as sheep and goats. Unfavourable transformation of pavements also includes their overgrowing and afforestation: in unused areas appear seedlings of trees and bushes, and green plants expand. Intensification of farming: ploughing, fertilizing and sowing of high-productivity species, is also a threat. Since the 1970s, the area of well-preserved xerothermic pavements in western Poland has been reduced to only 30% of the primary territory. Particularly susceptible to fast disappearance are isolated habitats and pavements with a small surface area, where there is no chance of reintroducing pasture management. Fast overgrowing of protected pavements is also caused by the lack of active protection measures in given sites [Barańska et al., 2010; Bornkamm, 2006; Bąba, 2004; Barańska, Jermaczek, 2009].

Several separate sites overgrown by thermophilic pavements occur in Jaworzno: Sadowa Góra wilderness (quarry – GEOsfera – Education Centre of Nature and Geology), Wielkanoc Hill in Ciężkowice, Imielin Hills, Glinna Hill and Bielany Hill pavements in Bory, and Rudna Hill [Tokarska-Guzik et al., 2012]. Some of these areas are under conservation, whereas other sites are proposed to be covered by protection measures.

The ‘Sadowa Góra wilderness’ nature-landscape complex was established in 2015 in Jaworzno. The area under legal protection is located in the north of Jaworzno town on Sadowa Hill, near the GEOsfera – Education Centre of Nature and Geology, with the abandoned quarry of the Dolomite Works Szczakowa (where exploitation terminated in 1998). The wilderness covers the area of xerothermic pavements, meadows, farmlands, patches of invasive (Canadian goldenrod) and expansive plants (common bracken), thickets, and pine-larch forest covers (Photography 7). The area also contains forestry yards, which are plant clusters serving as a fodder base and habitats for forest animals, birds and insects. A 2 km long educational path passes through the wilderness.

Photography 7

The wilderness is a mosaic of various types of habitats; a large part of the area includes farmlands, but only their small part are still used. Most abandoned farmlands are variably overgrown, creating wastelands with a different composition and vegetation density; due to soil conditions, they also include xerothermic pavements. Species of protected plants comprise: silver carline-thistle (Carlina acaulis), early marsh orchid (Dactylorhiza incarnata), February daphne (Daphne mezereum), royal helleborine (Epipactis atrorubens), broad-leaved helleborine (Epipactis helleborine), variegated horsetail (Equisetum variegatum), orange lily (Lilium bulbiferum), martagon lily (Lilium martagon), common twayblade (Listera ovata), white adder’s mouth (Malaxis monophyllos), garden star-of-Bethlehem (Ornithogalum umbellatum), and Orobanche lutea [Maślak, 2015]. The area of Sadowa Hill was previously known for the common cutleaf anemone (Pulsatilla patens); however, despite protective measures performed after the 1990s, its abundance decreased up to habitat disappearance. At present, measures aimed at active protection of xerothermic pavements and reintroduction of cutleaf anemone are performed in the wilderness.

In 2006–2008, the Jaworzno Hills were monitored for the state of xerothermic pavements in Poland [Monitoring gatunków i siedlisk przyrodniczych, 2009]. The results have confirmed that the main threat posed on the stability of xerothermic pavements is abandonment of farming-pasture management, resulting in the development of tree and bush seedlings in the undergrowth of pavement communities.

Thermophilic pavements are semi-natural communities; therefore, they will not be capable of intrinsic management and require human intervention. Therefore, passive legal protection is not sufficient – the pavements preserve their open character due to sustainable farming management, extensive grazing and mowing. The best results are achieved by pasture management with grazing of mixed animal herds: mainly sheep and goats with single cattle and horses. Due to difficult conditions, extreme habitats and poor quality of fodder, the best species of sheep and goats are from old, primary breeds. Grazing of animals on the pavements may help to stop secondary successions, which is the main factor responsible for the transformation of pavements into thermophilic thickets and forests. Livestock should have access to pavement plants before their stems harden (May–June); otherwise, the animals will avoid plants that will be difficult to chew.

Sheep grazing is conducted in Jaworzno town, which is in line with the development strategy of the Silesian Voivodeship for 2000–2015, priority 6: quality improvement of the natural and cultural environment, including attractiveness increase of the region [Studium uwarunkowań, 2012]. Since 2015, sheep from the Betlejem Society are grazed near the Leśne Bucze Forestry ecological site. Ten individuals of Polish sheep varieties, grazing on xerothermic pavements subject to ecological protection, contribute to preserving these valuable areas (Photography 8). In 2016, near Sadowa Hill and Gródek quarry, about 60 sheep were introduced as one of the project stages. It was accepted in Poland that an optimal number of sheep on an extensively grazed pavement is about 5 individuals per 1 ha.

Photography 8

Good effects are also obtained with rotational sheep grazing, in an alternative system in 4-year cycles. Selective browsing of soft-leaved plants, leaving only plants with xerothermic adaptations, leads to correct regulation of the pavement floral composition. Grazing animals remove bushes and tree seedlings in an ecological way, inhibiting their dispersion. Moreover, by roaming the slopes, they mix the topsoil, favouring the development of heliophyte seedlings of pavement plants. Grazing of local varieties of grazing animals results in the restoration of both natural and cultural values. Traditions related with grazing are very valuable and almost forgotten elements of the farming landscape in Poland.

Areas covered by xerothermic pavements in Poland and Europe have undergone substantial diminishing over the last decades. The main threats posed on thermophilic species include change in soil use towards intensification of farming linked with change of agrotechnics, such as soil cultivation and fertilization. Shift from extensive grazing of animals and the resulting succession of bushes and trees also has a negative impact on the pavements. Since several years, Jaworzno town authorities promote sheep grazing as a natural method of maintaining correct species composition of protected xerothermic pavements. Floristic impoverishment of these areas takes place following the lack of systematic and sustainable usage and the resulting secondary succession.

Authors of the photographs: Marta Boroń, Małgorzata Ociepińska.