Vascular plant flora in the Cytadela cemeteries in Poznań ( Poland )

The paper presents the spontaneous vascular flora and the flora originating from old or contemporary plantations found in all six currently existing cemeteries located in immediate vicinity on the slopes of the Cytadela Park in Poznań. These studies were carried out in the years 2011–2014. Over this period, 255 species of vascular plants were found. The most interesting species include: Chionodoxa luciliae, Rumex rugosus, Aegopodium podagraria ‘Variegatum’, Ficaria verna f. plenifolia, Galanthus nivalis f. pleniflora, Ornithogalum boucheanum, Ranunculus repens ‘Plena’, and hybrids: Dactylis ×intercedens, Gagea ×pomeranica, Ornithogalum boucheanum × O. nutans, Viola cyanea × V. odorata. A great number of spring geophytes, namely 31 species, was also found. Among species occurring spontaneously outside the graves, some were new for Poland, e.g., Chionodoxa luciliae, Ornithogalum boucheanum × O. nutans, Viola cyanea × V. odorata, while others were new for the Wielkopolska region: Rumex rugosus, Dactylis ×intercedens, Gagea ×pomeranica, as well as new for Poznań: Erigeron ramosus, Lilium bulbiferum, Muscari armeniacus, M. neglectum, Pimpinella nigra, Poa subcaerulea, and Veronica hederifolia s. s.


Introduction
The cemeteries on the slopes of the Poznań Cytadela Park are in the southern part of that largest park in Poznań, covering an area of 100 ha.Previously, it constituted the core of the Poznań Military Garrison (Winiary district) and at the same time it was a Church Parish.Here are buried the mortal remains of thousands of war victims from the wars of the nineteenth and twentieth centuries, creating one of the truly attractive, but not very widely known necropolises.About 5800 Soviet soldiers, 1300 French soldiers, and 500 British soldiers were buried here.Including the St. Adalbert's Parish cemetery, the tradition of burials in this place dates back about 180 years [1].
So far, the cemetery vascular flora in Poznań Cytadela has not been listed.Also, other cemetery flora in the currently operating and non-operating Poznań cemeteries has not been listed to date.
An exception in this respect is provided by the active cemeteries in the Poznań districts Jeżyce and Górczyn, the Corpus Christi cemetery at Bluszczowa Street and the St. John Vianney Parish cemetery at the Lutycka and Szczawnicka street crossing [2] as well as in the Świerczewo district [3].
The aim of this study was to analyze the botanical composition of the cemeteries in the Cytadela Park in Poznań and to verify the hypotheses that the introduced species of plants account for more than half of the total flora, while apophytes represent less than 10%.

Material and methods
Floristic studies on all six cemeteries on the southern slopes of Poznań Cytadela were carried out during the vegetation season in the years 2011-2014 (Fig. 1).
after 2000, and surviving in vegetative forms.
This assessment was based on own observations conducted in old cemeteries of the Wielkopolska region and on gardening catalogs.
Species which were found in two or three layers of their classification into individual groups of GGHs, LF, and GSEg were accounted for two or three times, i.e., in the manner they were reported.
The names of species occurring spontaneously follow Mirek et al. [7], while the names of cultivated plants follow Gawryś [8].The geo-historical and socio-ecological plant groups have been presented according to Chmiel [9] and Czarna [10], while the Raunkiaer life forms are named mainly after Zarzycki et al. [11].Species new for Poland have been identified in comparison with the work of Mirek et al. [4].Species new for the Wielkopolska region are named after Szulczewski [12], whereas the names of species new for Poznań follow Jackowiak [13].Protected species have been identified based on the Regulation of the Minister of the Environment of 9 October 2014 [14], while species of symbolic importance follow Kopaliński [15], Wysoczyński [16], Zaraś-Januszkiewicz et al. [17].

Cemetery characteristics
The Cytadela Park is the largest park in the city of Poznań with an area of approx.100 ha, created in the years 1963-1970 on the grounds of the former Winiary Fort.It was named the Park-Monument of the Brotherhood of Arms and Polish-Soviet Friendship.In 1992, this name was changed to the Cytadela Park.In 2008, the park together with other parts of the city was named a monument of history [17].
Within the area of the park, the following cemeteries are located: the Saint Adalbert's Parish Cemetery (Cmentarz parafii św.Wojciecha), the Garrison Cemetery (Cmentarz Garnizonowy), the Soviet War Heroes Cemetery (Cmentarz Bohaterów Radzieckich), the War Commonwealth Cemetery (Cmentarz Wspólnoty Brytyjskiej), the Cemetery of Polish Heroes (Cmentarz Bohaterów Polskich), and remnants of the former Old Garrison Cemetery, the German Honorary Cemetery and the Russian Orthodox quarter (Cmentarz Prawosławny).In the Garrison Cemetery, containing over 1500 graves, graves of military personnel and servicemen are located, including also graves of insurgents of the January Uprising of 1863 and the Wielkopolskie Uprising of 1918, soldiers killed in action in the years 1918-1920, generals, and holders of the Virtuti Militari cross.Victims of the Nazi and Soviet terror rule and Poles fighting in spring 1945 to free Poznań (the so-called Cytadelowcy) are also buried there.In the area, there are also mass graves with tombstones of Russian and French POWs.The Commonwealth Cemetery, among other things, includes the graves of 48 participants of the so-called Great Escape from Stalag Luft III, some of which were Poles [17].
In the Poznań Cytadela Park, the vegetation covered mainly the slopes, which was distinctly visible on the photos taken from airplanes in the period 1919-1939.The condition of tree stands was the object of main interest and care of a known Poznańbased naturalist, Prof. Adam Wodziczko [1].
Presently, the greatest care is provided to greenery in the Commonwealth Cemetery.In recent years, many herbaceous perennial plants with showy flowers have been planted there.The Cemetery of Polish Heroes is sown with grass.Thus, both of them differ markedly from the other cemeteries of the Cytadela Park.

Results
Within the area of the six studied cemeteries of Poznań Cytadela, the occurrence of 255 species of vascular plants was recorded (Tab.1).Among them, 76% of vascular flora species were introduced when the cemeteries were established or are planted presently.
The analysis of the frequency of occurrence of plant species showed that the most numerous group represents the species that include several specimens -almost 50% (the second degree in the 7-point frequency scale; Fig. 1).A total of 20 species were classified as rare and they accounted for over 7%.They mainly included the following tree species: Acer pseudoplatanus, Betula pendula, Carpinus betulus, Aesculus hippocastanum, Fraxinus excelsior, Quercus robur, Robinia pseudoacacia, Tilia cordata, T. platyphyllos, but also Viscum album, as well as herbaceous plants: Gagea lutea, Galium aparine, Ornithogalum boucheanum, O. nutans, Scilla sibirica, Taraxacum officinale, Viola odorata.Two species were reported in the third cover degree (Aegopodium podagraria, Aesculus hippocastanum) and one in the fourth cover degree (Acer platanoides).No species were found in the fifth cover degree.
A high presence of species in the first cover degree was due to cultivation (additional sowing of grass, addition of ornamental plants on almost 1/2 of the cemetery area), while the remaining part of the cemetery is less frequently visited and utilized.Therefore, Aegopodium padagraria reached a high cover degree.
The species recorded in all studied cemeteries of Poznań constitute a full spectrum of the life forms according to Raunkiaer (Tab.1).The most numerous group in four studied cemeteries is represented by hemicryptophytes (over 43%).This is due to the presence of the old part (1/2 of the total cemetery area), where almost no human interference takes place, as well as very numerous plantings of herbaceous perennials in the Commonwealth Cemetery.
Moreover, a considerable share of geophytes (32 species) was found -with their greatest number in the oldest part of the Cytadela cemetery (Fig. 2  cemeteries include two hybrids: Gagea ×pomeranica, Ornithogalum boucheanum × O. nutans.Their appearance was possible thanks to the presence of the parental species, potentially found only in cemeteries and in the parks of former manors.The abovementioned geophytes include exclusively spring species.Mega-and nanophanerophytes in these cemeteries are represented by a similar number of species (about 11% each).The high proportion of therophytes (49 species) is associated with the presence of footpaths in the southern and eastern parts of the cemeteries.An analysis of the share of the particular vascular plant species in the studied cemeteries according to the geo-historical division indicates that the most numerous group consists of indigenous species -apophytes, which account together for over 47% of the total flora in the studied cemeteries (Fig. 3).It is connected with the presence of the cemetery's old no-longer-used section of forest-like character (about 1/2 of the total area) as well as the current additional planting of the following indigenous species: Aegopodium podagraria 'Variegatum' , Ajuga reptans ' Artropurpurea' , Arabis alpina, Armeria maritima subsp.elongata, Campanula persicifolia, Carex ornithopoda 'Variegata' , Geranium sanguieum, Potentilla reptans 'Plena' .Among alien species, the highest share is found for plants which were introduced into cultivation and have remained as such for a long time, but which do not spread beyond the locality where they were introduced (e.g., in cemeteries, as it is in this case).They represent ergasiophytes (86 species).Still another group identified comprises plant species which are cultivated, but do not run wild.They are represented by 22 species which were introduced and are still additionally planted in the Cemetery of Polish Heroes and in the Cemetery of the British Commonwealth.
The vegetation of the studied sites originates from 15 groups of synergetic plant communities.Many of the species found there prefer communities of fertile deciduous forests and shrub communities (53 species).Apart from trees and shrubs, which were almost exclusively introduced at the time the cemetery was established, many herbaceous plants were also planted.These include: Aegopodium podagraria, Ajuga reptas, Anemone nemorosa, A. ranunculoides, Aquilegia vulgaris, Campanula persicifolia, Chaerophyllum aromaticum, Convallaria majalis, Corydalis solida, Ficaria verna, Gagea lutea, Galanthus nivalis, Geranium sanguineum, Lamium maculatum, Myosotis sylvatica.A rather numerous group also consists of species usually growing in nitrophilous thicket communities and in forest edge communities (23 species).A significant participation is also shown for semi-natural and anthropogenic meadow and pasture communities from the Arrenatheretalia order (17 species).Species with no closer phytosociological affiliation (group 19) are most numerously represented in all the cemeteries (100 species).This is observed for all plants taken into consideration, also those planted in the Cemetery of Polish Heroes and in the Cemetery of British Commonwealth.
Among the spontaneously occurring species in the studied cemeteries, in the shrub layer there were three species: Acer campestre, Euonymus eupropaeus, and Sambucus nigra.
Problematic indigenous species which could have been formerly introduced to cultivation in the studied cemeteries and which have survived until the present include the following: Campanula rapunculoides, Chaerophyllum aromaticum, Ficaria verna, Gagea pratensis, Hedera helix, and Vinca minor.
T. orientalis, while in the herbaceous layer there were In the Poznań Cytadela cemeteries, a total of 60 species of symbolic importance were also found.A total of 11 species are protected in Polandat the same time, all of them are plants of symbolic importance (Tab.1).Moreover, two species planted there which are entered in the Polish red book of plants were also reported, i.e., Dianthus gratinopolitanus [18] and Inula ensifolia [19].
Among the plants found in the cemeteries of the Poznań Cytadela, one should mention those associated with active cemeteries: Campanula rapunculoides, Erigeron annuus, E. ramosus, and Solidago gigantea.

Discussion
No studies are being conducted on vascular flora in necropolises during mapping of selected larger areas of Poland.Also, in the city of Poznań no studies have been conducted on the operating cemeteries or the former cemeteries that exist at present only as parks [20].This was done for the first time for the central Wielkopolska region [10].
Botanical analyses of the flora in cemeteries have been conducted in few operating [13,21] or closed cemeteries [22,23].First of all, the primary aim of these studies was to create a complete list of species, including basic analysis of life forms as well as geo-historical and socio-geographical groups.Only now such studies are being fully initiated: they are being conducted on a larger number of cemeteries using numerical methods [24].Such large-scale studies facilitate a comprehensive analysis of directions of diversification of flora in the cemeteries as well as factors modifying their biodiversity.
Among plants reported in the cemeteries of Poznań Cytadela, the largest share was found for ergasiophytes (approx.33%).The group next in rank comprises apophytes (approx.49%), with spontaneophytes ranking third (approx.17%).The above percentage shares of reported plants result from the introduction of many native and alien species, among them many species of trees and shrubs, as well as ornamental herbaceous plants.In turn, the most recent plantings are alien ornamental herbaceous perennials.Among all the reported species of vascular plants, as many as 76% taxa were introduced at the time when the cemeteries were established or are being planted at present.Species of ornamental plants introduced in the past to decorate the cemeteries and surviving there as well as those planted at present are ergasiophytes.In the past, these species were classified as ephemerophytes, i.e., species that penetrate wild localities from cultivation, persist for 1, 2, or 3 years and then die [13].
In the old cemeteries, a large degree of cover is found for all the layers: trees, shrubs, and herbaceous plants [23].In exceptional cases, the shrub layer is prevented from development.This happens when a given cemetery is a tourist attraction [24].In Poznań, all the three well-developed layers may be found in the old closed Catholic cemetery in the district of Świerczewo [3].In the operating cemeteries in Poznań [2], the herbaceous layer has not reached a considerable degree of cover due to frequent raking and treading.
The problematic indigenous species which could have been previously introduced to cultivation in the studied cemeteries and which have survived until the present include Gagea pratensis, Hedera helix, Ligustrum vulgare, Ornithogalum umbellatum, and Vinca minor.and T. serpyllum.■ The hypothesis that in the cemeteries there are many planted species was confirmed (Fig. 1), while it may not be said that there is a limited number of spontaneous apophytes (65 species).

Fig. 1
Fig. 1 Number of species in particular frequency classes in Poznań Cytadela cemeteries (explanations in Tab. 1)

Fig. 2 Fig. 3
Fig. 2 Number of species representing different life forms in the Poznań Cytadela cemetery (explanations in Tab. 1).