International workshop SPONTANEUOS SUCCESSION IN ECOSYSTEM RESTORATION

EXCURSION GUIDE
September 9th - 10th, 1999

Itinerary: Departure from České Budějovice, 9 September, 9.00 am; Route: Písek, Příbram, Bohemian Karst - village Srbsko (approx. 12.00); lunch; in the afternoon, visit of successinal stages in abandoned fields and spontaneously re-vegetated limestone quarries, as well as fragments of natural steppe communities and well-preserved woodlands; total length of walk app. 12 km; dinner and accomodation in Karlštejn; 10 September, departure 8.30, arrival to the Most Basin about 11.00; lunch in the town of Most, visit of spontaneously re-vegetated, and technically reclaimed dumps from open-cast brown-coal mining; arrival to Prague at about 5.00 p.m., to České Budějovice at about 7.00 p.m.

The Bohemian Karst

General description

The Bohemian Karst represents one of the most diverse landscapes in Central Europe, being rich not only in its nature but also in cultural history, including research in natural sciences. For example, the famous French geologist Joachime Barrande described in this area, in the middle of the 19th century, many fossils and derived the Silur-Devon stratigraphy. The history of vegetation research in the country has its roots in the region either, both classical phytosociology and modern quantitative ecology. Moreover, there are several historical monuments important for the early history of the Czech kingdom such as the fortress where St. Wenceslas probably spent his childhood in the early 10th century, and the most famous and valuable castle named Karlštejn which served as a king treasury in the Middle Ages, protecting the king's crown and other jewellery. Recently, in the communist era, the Bohemian Karst became a conflicting area between efforts for economical exploitation and interests of nature scientists and conservationists, despite the early declaration of the most valuable parts as nature reserves (some of them already in the 1930s) and the status of Protected Lanscape Area (1972). The prevailing part of the area is formed by very pure limestones of Silur and Devonian origin. However, acid Palaeozoic slates and fluvial gravel sediments of early Quarternary origin also occur here. Scattered localities of Palaeozoic volcanits (diabas) contribute to geological diversity. The soft bedrock was deeply eroded resulting in diverse relief and, consequently, vegetation. The vegetation diversity was further supported by earlier human activities - a fine scale deforestation, extensive grazing, periodical abandonment of arable land, etc. Despite the uniform land management in the past decades, the vegetation diversity still remains high. The altitude varies between 200 and 450 m a. s. l., the average annual temperature is about 8.5 °C, the average annual sum of precipitation reaches approximately 500 mm.

Phytogeographical relations

Various floristic elements meet together in the area, especially distinct, besides typical representatives of Central European woodland flora, are those of the sub-mediterranean origin (e. g. Allium montanum, Carex humilis, Dictamnus albus, Erysimum crepidifolium, Geranium sanquineum, Quercus pubescens, Teucrium chamaedrys). De-montaneous (de-alpine) species are typical especially of steep rocks and outcrops, such as Biscutella laevigata, Saxifraga paniculata, Sesleria albicans, Thlaspi montanum. Some species of the continental origin contribute to the rich flora of steppe-like communities primarilly occurring on the most exposed southern slopes (e. g. Anemone silvestris, Cerasus fruticosa, Helianthemum canum, Oxytropis pillosa, Stipa joanis).

Main vegetation types

The zonal vegetation in the area is represented by species-rich oak-hornbeam woodland (Carpinion betuli), namely ass. Melampyro nemorosi-Carpinetum Passarge 1957. This vegetation still covers about 18 % of the area. On steep slopes, especially on screes, there are transitions to communities of all. Tilio-Acerion, ass. Aceri-Carpinetum Klika 1941 (described from the Bohemian Karst). On cold, shaded northern slopes, especially in higher elevations, we can see well preserved calcareous beech forests of the (sub)alliance Cephalanthero-Fagion with the typical occurrence of orchids such as Cephalanthera rubra, C. damasonium, and Corallorhiza trifida. Thermophilous oak woodlands are represented by two types from the alliance Quercion pubescenti-petraeae, namely that on deep soils (ass. Potentillo albae-Quercetum Libbert 1933) and that on shallow soils of the rendzina type (ass. Lathyro versicoloris-Quercetum pubescentis Klika 1932, possibly also Lithospermo-Quercetum Br.-Bl. 1932). The latter represents the most species rich and valuable woodland with the typical extrazonal occurrence of Quercus pubescens close to its northern limit. The association Lathyro versicoloris-Quercetum pubescentis is considered as endemic for the area with many sub-mediterranean and continental species. In many sites, there are gradual transitions or mozaic boundaries with relict steppe-like communities, often with distinct fringe communities dominated by Geranium sanquineum (class. Trifolio-Geranietea). The steppe fragments (all. Festucion valesiaceae) represent another rich and valuable vegetation, especially those of the primary origin. Being affected by grazing, the steppe-like vegetation expanded in the past. Recently, however, the secondary sites are overgrown again by woodland due to the gradual secondary succession. Moreover, some sites are overgrown by competitive grasses such as Arrhenatherum elatius, probably because of the nitrogen aerial deposition. A continuous existence of at least some fragments is expected during the whole Holocene period, thus many relict species of the early Holocene and even of the late Glacial cold steppe have survived (e. g. Sesleria albicans, Saxifraga paniculata, Helianthemum canum, Dracocephalum austriacum). The open vegetation on steep northern slopes is usually classified into the all. Seslerio-Festucion pallentis. Besides the primary vegetation, some secondary vegetation types draw attention, especially the secondary grasslands of the all. Bromion erecti, ruderal vegetation of the all. Sisymbrion officinalis, and segetal vegetation of the all. Caucalion lappulae. Especially the latter often contains species which are now very rare in the country (e. g. Bifora radians, Bupleurum rotundifolium, Melampyrum arvense).

Succession in abandoned fields

Succession in abandoned fields was subjected to a detailed quantitative ecological study in the late 1970s and early 1980s (Osbornová et al. 1990). Three sub-seres were distinguished reflecting soil moisture: xeric, mezic, and wet. Initial stages are composed by common, mostly annual weeds, only in the xeric sere we can occassionally see some rare, thermophilous weeds such as Caucalis lappula, Adonis vernalis, Scherardia arvensis etc. Latter, usually between the 4th and 12th year of succession, perennial weeds dominate, especially Agropyron repens, Artemisia campestris, Cirsium arvense, and Galium album, being often preceded by biennials in the xeric sere (mostly Carduus acanthoides and Crepis biennis). Then the reconstructed successional development substantially differs: In the xeric sere, a short-grass grassland develops, usually formed by Festuca rupicola, Poa angustifolia, Fragaria viridis, with scattered shrubs (species of Crataegus and Rosa). We will visit a stage developing nearly 80 years since abandonment. In the mesic sere, into the stage dominated by mesophilous grasses (Arrhenatherum elatius, Festuca pratensis, F. rubra) shrubs penetrate, forming rapidly, after app. 15 years of succession close stands, dominated by Prunus spinosa which is later overgrown by Crataegus species. A close Crataegus stage persists for a long time. We will visit a 60 years old stage where Fraxinus excelsior is seen to establish in the understory. The wet sere was decribed only fragmentary and will not be demonstrated during the excursion. The succession in this sere proceeds towards a stage with Phragmites australis.

Succession in limestone quarries

There are more than 100 quarries in the Bohemian Karst, most of them of a small size (up to 1 ha) and now abandoned. However, several large quarries are still in use, having pronounced effects on the landscape. How spontaneous vegetation succession can be used in reclamation of the quarries is a task of the contemporary project of the Ministery of Environmental Protection held by K. Prach, P. Pyšek and J. Sádlo. We use the opportunity of the excursion to discuss the topic with the workshop participants. The succession generally runs towards four main, more or less stabilized stages: (i) open vegetation formed by S-strategists (typically with Sedum species) on steep rocky slopes, bottoms and screes; (ii) short grassland on shallow soils, dominated by Festuca rupicola and with scattered shrubs (Rosa and Crataegus spec. div., Salix caprea, Cornus sanguinea, Acer campestre); (iii) tall grasland, dominated by Arrhenatherum elatius, Bromus erectus or Brachypodium pinnatum often with the above mentioned shrubs or trees such as Betula pendula, Fraxinus excelsior, or Populus nigra, tremula and cult.; (iv) close shrubs usually with nitrophilous species in the herb layer; (v) woodland, composed beside the above mentioned trees by Quercus robur, Carpinus betulus, Acer pseudoplatanus, locally also by Pinus sylvestris or Picea excelsa, the later in the wettest, shaded sites. In the most quarries a mosaic of the stages exists, determined by habitat differences and also by different successional age. The physiognomy and basic species composition are usually formed during the first 15 years of succession, then the stages are gradually stabilized up to app. 30^th year of succession and later only small changes occur. The vegetation development of the later successional stages is largely influenced by the surrounding vegetation. If natural vegetation, especially the steppe-like, is present, the typical species can establish in the quarry. Species typical of the (semi) natural woodlands establish especially in small quarries inside the woodlands. Generally, the quarries can provide refugia for the species which require open, low productive sites; these often retreat from the present landscape. On the other hand, ocurrence of alien invasive plants is generally low, except Robinia pseudoaccacia and Pinus nigra sometimes planted in the vicinity. The recent trend in the reclamation of quarries to cover the sites by organic soil results into negative effects because robust, competitive ruderals usually expand, and consequently, species diversity is low. Moreover, spontaneous establishment of native woody species is then very limited. Generally, we consider the spontaneous succession as the best (and cheapest) way of the quarries restoration, comparably fast and leading to re-establishment of (semi) natural vegetation. The presented conclusions are not valid for large quarries where processes of ruderalization are more pronounced and establishment of species typical for (semi)natural vegetation is less probable.

The Most Region

General

The Most Region is represented mostly by the flat Most Basin where brown coal layers are usually overburden by clay sediments of the Miocene period, removed and dumped during mining and reaching various depth from several tens to several hundred meters. The basin is bordered by steep slopes of the Krušné hory Mts. covered mostly with natural beech woodlands, and from the other side by a range of solitary conic hills of volcanic origin (the České středohoří Hills). Earlier, a part of the basin was filled with a lake (named Komořanské jezero), the largest natural water body in the country. The last remnants of the lake, and adjoining marshes including some localities of halophilous vegetation, retreated due the open-cast mining in the past decades. Unfortunately, the high meso-scale environmental mosaic in the region has been largely destroyed by the mining and associated activities. Air pollution from the numerous power stations, where the local coal of the low quality is burnt, have caused a total destruction of spruce forests in the surrounding mountains. Besides the destruction of nature, many historical monuments, including the large historical town Most, were demolished as the mines expanded. About 60 settlements totally disappeared. Nowadays, the region is considered as one of the largest active coal mining areas in Europe. The altitude of the basin is about 250 m, the mean annual temperature reaches 8.5 0C, and total annual sum of precipitation is about 470 mm.

Succession on dumps from mining

At present, the dumps cover the area of about 200 km2. The large portion has been reclaimed and especially in the past 5 years, the extent of the reclaimed dumps has increased. The dumps are usually re-modelled and then various deciduous trees are planted. A minor area of the reclaimed dumps is used for agricultural purpose, including one vineyard, or as amenity sites. A part of the dumps is left to spontaneous succession. The succession was described in details by Prach (1987), the paper will be available during the excursion. Here, only a short description follows: It is not surprising that the succession starts by annuals, such as Polygonum lapathifolium, P. aviculare, Atriplex sagittata, A. patula, Senecio viscosus, Tripleurospermum maritimum, Chenopodium spec. div. They reach the cover about 30 % in the 6th year of succession. Then, after a usual short-lasting stage with prevalence of biennials (Carduus acanthoides, Echium vulgare) perennial forbs take dominance after ca. 10 years of succession (especially Tanacetum vulgare, Artemisia vulgaris, and Tussilago farfara) being followed by a gradual expansion of perennial grasses such as Agropyron repens, Arrhenatherum elatius, and especially Calamagrostis epigeios. The first woody species which is able to establish already in the first years of succession is the endozoochorous species Sambucus nigra. Before closing the herb layer by perennials, several other woody species have a chance to establish such as Betula pendula, Salix caprea, Fraxinus excelsior, Acer pseudoplatanus and rarely some others. When the herb layer forms nearly a compact cover at about the 15th year of succession, further establishment of woody plants is very restricted. The average cover of woody species is about 10 % even in the oldest large dumps which are about 45 years old. In that time, Calamagrostis epigeios reaches cover of about 50 % and the succession is more or less arrested at this stage. The described sequence is typical for about 90 % of the dump area, only on dry tops the succession is slower and, on the contrary, in depressions it runs faster. In deep and very wet depressions a different sere can be distinguished, leading from loose stands of Typha latifolia to dense stands of Phragmites australis. A different successional development can be also seen on steep slopes where Tussilago farfara usually forms a distinct and persistent stage. We consider the recent trends of technical reclamation of the whole area disturbed by mining as useless. Technically reclaimed sites are less diverse in micro- and meso- habitats, and harbour much lower number of species then spontaneously re-vegetated sites. We recommend to rely more upon the spontaneous, or reasonably directed succession. Details on the succession will be discussed in the field.

Karel Prach & Petr Pyšek

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