Flora and vegetation of walls in the town of Krosno Odrzanskie (Poland)

The nora and vegct3tion of waJls in Krosno Odrzanskie (\Ves! Poland) is describcd bascd on ficld research eonducted in 1999 and 2000. The vascular nora consisls of 96 specics from 35 families. Predominalion of apophYlcS and plants capable of 'Icgct<llive propagation was obscrvcd. Associ'lIions of Aspll!/Iie/llllJ tric!lOmtI/JO-rulae-/IIl1mr;a(' and Cym/)a/ariefllm ml/ml;.\" are reponed for the first time from Ihis regioo of Poland.


INTRODUCTION
Walls of buildings and of olher constructions made of bricks, stones or concrele belong to specific, polyhemerobic habitats, which can be a substitute habitats for rock plants.They are common but rarely colonized, because of their vertical and even surface.characterized by unfavourable water and temperature regimes and recurrent conservation of the walls.The insufficiem inf10w of diaspores can also be a reason for slow colonization of walls.especially in centres of large agglomeralions.The spores of cryplogams (i.e.feros and bryophytes) and lichens are easily Iransporled by wind over long distances.so lhese organisms are normully first to colonize walls.Resides, they are less sensilive lO unfavourable thermal and water condilions.Only the heavily polluted parts of large cilies and industri::l1 constructions are Iichen deserls.Vascular plants can normally grow on siles where at least a small amount of humus has accumulated.This kind of Substfille is formed in calcium-containing mortar or slits and fissures of the walls.previously coionized by lichens and mosses.
The aim of lhe presenl work was to make a geobotanical analysis of lhe flora and  (GUMINSKI, 1948;BARTKOWSKI, 1970).

Flora
The flora of vascular planls is rather poor.It consists of only 96 tuxa (Table 1).The relatively small number of taxa is probably due to lhe small area of lhe lown und the small number of walls that offer habitats suilable for plants.The numbers of species reponed from such habitats in neighbouring lands were greater: 188 on walls of castle ruins in Lower Silesia (WERETELNIK, 1982), 146 in Wroclaw (SWIERKOSZ, 1993), IlIon lhe Palace of Culture and Science in Warsaw (GALERA & SUDNIK-WÓJCIKOWSKA.200(30) and 149 in Germany (BRANDES, 1996).
Additionally, 18 species of lichens and 14 species of mosses were found on watls in Krosoo.The relatively large oumber of lichens could indicate a low level of pollution in the town, but most of them belong to taxa wilh a wide ecological scale.
Native vascular plam species (spontaneophytes) predominate, accounling for about 73% of aH taxa, but only 5% can be treated as typical non-syoanthropic ones (Fig. 2).This is consistent with the reports of maoy authors mentioned aboye.The typical spontaneophytes (mesohemerospontaneophytes after JACKOWIAK, 1990) are: Brac!lypot!i//lII sylvll1icum.Feslllca giganlea, Lamium maCllfalllm and Lysi/lloc!lia1Il11lll1lularill.AH other sponlalleous plant species are apophytes.The forest, lhicket and meadow laxa \Vere the mosl common among the sponlaneous plant species found there.In the case of Silesian castles.where these types of plants also dominate, the situation was explained as arising from the c10se neighbourhood of foresto xerothermic thickets and meadows (WERETELNIK.1982).
Most of the taxa recorded on walls io Krosno can be identified as hemicryptophyles (RAUNKIAER, 1934), which eonsti'ule more lhan 40% of lhe 'olal flora (Fig. 3).Therophy'es raok second (27%), but woody plants (phanerophytes) are also significant.with a contribution of 11 %.Proponions of plant life-forms were differenl in various regions.For example.00 the Palace of Culture and Science in Warsaw.40% of plant species were  , 1993).
The specific condilions on the walls are al 50 a reason for the limited number of species thal can survive and elomplete their Iife-cycle there.The woody species (phanerophytes), for example, were observed only in {he seedling slage.Their appearaoce depends 00 the perrnanent supply of diaspores frorn lhe oeighbourhood.Seeds of phanerophytes are delivered by birds (omi'hochory) or by wind (anemochory).The immediate neighbourhood of parental specirneos is due to lhe occurrence of al least sorne barochorous species.The mosl cornmonly occurring herbaceous plants growing, flowering and fruitiog in wall fissures-; produce large arnounls of lighl, anemochorous seeds.Also, myrmecochorous species are frequent on walls (ULaRICH, 1939).

Vegetatioo
Two pioneer planl communilies were found on walls in Krosno Odrzañskie: AspJeniet/ll/1 tric/lOmano-rutae-murariae and CymbaJarietum muraJis (Table 2).80th of lhern are quite widespread in the town.although AspJellietum tricltomallo-rurae-I/Il1rariae is rare and CymbaJarietum muraJis is extrernely rare in lhe Wielkopolska Lowland and Lubuska Upland.The associations of fems are natural auxochorous plant eornmunilies, while CymhaJarietum muraJis is a ruderal.extrernely specialized cornmunity (FALlNSKI.1969: BRZEG and WOJTERSKA.1996).The ¡alter community seems te be a syntaxon associaled with the sunnier soulhem and westem exposures, as il \Vas also reponed from Silesia (WERETElNIK, 1982).The intensive insolation is probably the reason for a ralher poor floristic composition of the comrnunity.Only six species of vascular plams were recorded there and only 13 tegether Wilh lichens and mosses.lt must be noted that I lO 8 laxa (5 on average) were found in individual phytosociological records.Asplenietum ,r¡c!lo/1lQlIO•rutae•/lllIrariae is found mostly on east-facing walls, which are more shaded.The layer of mosses and lichens is beuer developed and lhe floristic composiLion of lhe phytoeoenoses is richer, as 10 to 19 (15 on average) laxa were found there.The 25 laxa of vascular plants, 5 of lichens and 4 of mosses were found in parches of this plant communily in Krosno Odrzanskie.The plant communities described from lhe walls of Krosno Odrzanskie are relalively poor and Iheir patches cover smaller areas lhan in olher regions (ANIOL-KwIATKOWSKA, 1974;ZAJAC, 1974;RATYNSKA, 2000;CEYNOWA-GIElDON, 1994), and especially when compared with lhe walls of caslle ruins in Silesia (WERETELNIK, 1982).
Mosl of lhe laxa found in lhe lwo associatiolls described aboye, were represented by single specimens.This attests to their accidental composition, which is al so unstable and helerogeneous, especially in lhe case of CYlIlbalarielllm mI/mUs.Apart from Cymbalaria lIluraUs.no olher species occurs in a11 phylosociologic records.Only seedlings of TaxIIs sp., Viola adorara, Ihe Iichens Lec{lI/ora albescens and Lepr{lritl i/lc{ma and the mosses Brachyrecilllll salebroslllll and B. rublllalllm have a high conslancy.CONCLUSIONS l.Old walls are specific polyhemerobic sites.The composilion of the flora of bolh Lhe seed and spore plants of this habital is diversified and ineludes a few specific taxa, while Ihe others are framework taxa of lhe flora of the lown.
2. In spite of lhe fact lhat walls are eminenlly anlhropogenic sites.their nora is composed mostly of nalive plants (spontaneophytes).This indicales lhat walls made of stones or bricks joined Wilh morlar comaining calcium are specific habilats, which acl as 'vicars' of natural rocky siles for rock plants.On this kind of siles, rock planls find their only possibility of growing and enlarging lheir range of distribulion in lowlands, where natural racks are absent (see ZAJAC & ZAJAC, 1973, 2001).
3. The walls are siles thal are nol very susceptible to colonization by anthropophytes.4. The great participalioll of species capable of vegetalive propagation shows lhat this adaptation plays a considerable role in Ihe colonizalion of walls.Produclioll of large quantilies of small seeds, anemochory and myrmecochory are other specific characlers of planls growing on walls.
5. The investigation of lhe survival rate of plants growing on walls would be a very interesting phenomenon to examine on permanenl plols.

Fig. 3 .Fig. 4 .
Fig. 3. Proportion of Raunkiaer's life-forms (descriplion see lable 1) vegetation of waJls in Krosno Odrzatískie.alQwn on lhe Dder River, located al lhe mouth of (he B6br River.Krosno OdrzaJÍskie is a small bUl old town, eSlablished in lhe 13th century.The walls of the ruined castle were partly constructed al lhat time, but all other buildings are less than 200 years old.About 65% of lhe lown was destroyed in 1945, at lhe end of lhe 2 nd World War, and many new buildings have been conslrucled in place of lhe destroyed ones.Now it is inhabited by about len lhousand people.The intermediate, oceanic-continental c1imale is characleristic of lhe region, with (he growing season lasling 218-220 days and annual precipitation of 570-650 mm.The mean annual temperature is over SOC, with 30 frosty days and about lOO days with hoarfrost per year.Weslerly winds prevail, and are frequently strong