Lichens and higher plants on stone: a review - AseanBiodiversity.info

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3.3. Damage Vegetation growing on historical buildings <strong>and</strong> ruins may be picturesque but it is also one of the main reasons for their deterioration (Dia <strong>and</strong> Not, 1991; Mouga <strong>and</strong> Almeida 1994; Almeida et al., 1994). Both the roots <strong>and</strong> the aerial part of the <strong>plants</strong> damage the structure of the walls. The branches <strong>and</strong> leaves hide the building so that it cannot be appreciated, <strong>and</strong> cause static damage due to their weight, which may cause stones or large portions of wall to fall (Plate 2d). They increase the risk of re with all the destruction that it can cause. The roots may penetrate deep into the structure <strong>and</strong> grow to a large size, causing physical <strong>and</strong> chemical damage. The secretions of roots contain substances that attack building materials, <strong>and</strong> their mechanical force opens cracks, causes crumbling <strong>and</strong> loosens stones <strong>and</strong> large fragments of wall. The damage is not limited to that which the plant causes to the building, but also includes the consequences of falling stones (Plate 2D). Not all <strong>plants</strong> cause the same type or quantity of damage (Table 1). Herbaceous <strong>plants</strong> like Mercurialis annua, Parietaria di usa <strong>and</strong> Sonchus tenerrimus are certainly less destructive than trees <strong>and</strong> shrubs like Ailanthus altissima, Capparis spinosa, Clematis vitalba, Ficus carica, Hedera helix <strong>and</strong> Rubus ulmifolius (Almeida et al., 1994). Herbaceous perennials, suchas Cynodon dactylon, Dittrichia viscosa <strong>and</strong> Cheiranthus cheiri, are more harmful than herbaceous annuals. However, the most destructive <strong>plants</strong> of all are those with vegetative reproduction (Fig. 7). Stolons <strong>and</strong> rhizomes cause the infesting <strong>plants</strong> to increase in size <strong>and</strong> propagate over large areas, to the obvious detriment of building structure. The damage caused by this type of vegetation is especially destructive to statues (Plate 2e). A plant that is aesthetically very attractive but which causes many types of damage is Hedera helix. The fruit is eaten by birds <strong>and</strong> the seeds germinate in many microsites (Fig. 7). The damage varies according to whether the plant grows as a liana from the soil or actually germinates <strong>and</strong> grows in the wall. In the rst case, the damage is due to the weight of the aerial part; in the second, there is additionally the destructive action of the roots. If it grows on a stuccoed wall, it may cause the plaster to fall away. 3.4. Methods of control Methods of control vary according to the type of plant, the structure of the building, its state of conservation <strong>and</strong> its location. Recent buildings made of classical materials (squared stones <strong>and</strong> bricks), should be checked to prevent the formation of substrate <strong>and</strong> the growth of pioneer <strong>plants</strong> (Fig. 1). The speed of colonization depends on building structure <strong>and</strong> materials (Fig. 1). Decorations suchas ledges <strong>and</strong> cornices favor the formation of substrate. Porous materials or those with cracks, like travertine <strong>and</strong> red bricks, provide good microsites (Fig. 6). The state of conservation of a building is very important in determining the appropriate method of control. For ruins, periodic clearing of <strong>plants</strong> should be performed to prevent plant growth between the stones <strong>and</strong> crumbling of the remains (Plate 2f). Large buildings of historical interest in towns should be checked for aesthetic reasons, in the interests of their conservation <strong>and</strong> for the safety of inhabitants <strong>and</strong> visitors. Two very ancient examples are the Pantheon <strong>and</strong> Coliseum in Rome, but even Baroque <strong>and</strong> Renaissance buildings can be dangerous in a city like Rome if they are infested with <strong>plants</strong>. Buildings fenced o on archaeological sites present less of a peril to visitors. The surest method of control with long term advantages is total removal of the <strong>plants</strong>, including their roots. After this the cracks are lled so that other seeds do not germinate in them. This method works well for herbaceous <strong>plants</strong> but the roots of ligneous <strong>plants</strong> are di cult to remove, <strong>and</strong> pieces remaining may give rise to new growth. Other di culties are encountered when the walls are impervious or very high. The surface may be damaged if tools such as saws, chisels <strong>and</strong> drills are used. Manual weeding is useful for preventing the establishment of herbaceous <strong>plants</strong>, but as we already mentioned, they are only the rst colonizers. When the wall already hosts luxuriant vegetation in which the herbaceous <strong>plants</strong> have been replaced by ligneous ones, manual weeding is no longer e cacious, <strong>and</strong> more complex methods must be used. These may include killing the plant with chemicals, or if the position of the plant in the building permits, removing stones, extirpating the roots <strong>and</strong> rebuilding. Chemical herbicides are much faster <strong>and</strong> more e cient than manual weeding, but certain environmental (climate, chemical <strong>and</strong> physical properties of the building materials, analysis of the vegetation in the area where the chemical is to be applied) <strong>and</strong> toxicological (toxicity, volatility, biodegradability) aspects need to be veri ed before they are used. Today herbicides with speci c properties <strong>and</strong> di erent mechanisms of action (contact, systemic, residual, <strong>and</strong> so forth) are available (Appendix A). Their careful use can help greatly in the maintenance <strong>and</strong> protection of buildings <strong>and</strong> monuments (Caneva <strong>and</strong> De Marco, 1986; Caneva et al., 1991). Contact <strong>and</strong> systemic herbicides belong to the latest generation <strong>and</strong> are especially indicated because of their reduced environmental impact. They may be applied sporadically or repeatedly, up to three times. The same product may be used or others may be alternated to exploit their di erent possibilities. The most commonly applied herbicidal methods are: (a) total elimination of all vegetation (bare ground) which has a long term e ect; (b) temporary (short term) weeding; (c) selective weeding of herbaceous <strong>plants</strong>; (d) brush control, consisting in removing shrubs <strong>and</strong> trees <strong>and</strong> leaving herbaceous vegetation. The last two methods are the most frequent in archaeological sites, whereas total <strong>and</strong> temporary weeding are used for historical buildings <strong>and</strong> monuments in towns. Bettini <strong>and</strong> Villa (1975) <strong>and</strong> Bettini <strong>and</strong> Cinquanta
Table 1 List of the principal species growing on the walls of historical interest. Tree <strong>and</strong> shrub species are more destructive than herbaceous <strong>plants</strong>. Not all species are capable of growing on vertical surfaces. Nomenclature according to Flora Europea (Tutin et al., 1964–1980); common names from Clapham et al. (1962) Families <strong>and</strong> species Adiantaceae Common names Forms Microsites Damage Adiantum capillus-veneris L. Hypolepidaceae Maidenhair-fern HP A,B,C,D,J, + Pteridium aquilinum (L.) Kuhn Aspleniaceae Bracken HP A,B,C,D,J + Asplenium trichomanes L. Maidenhair Spleenwort HP A,B,C,D,J + Ceterach o Ulmaceae cinarum DC. Rusty-back Fern HP A,B,C,D,J + Celtis australis L. Nettle-tree T E,F,H,I,K ++++ Ulmus minor Miller Moraceae Elm S=T E,F,H,I ++++ Ficus carica L. Urticaceae Fig S=T A,B,C,D,E,F,H,I,K ++++ Parietaria di usa Mert. & KochPellitory of the Wall HP A,B,C,D,E,F,G,H,I,J + Urtica dubia Forska l Caryophyllaceae Nettle HP A,B,C,D,E,F,H,I + Arenaria serpyllifolia L. Thyme-leaved S<strong>and</strong>wort HA A,B,F,H,I + Minuartia hybrida (Vill.) Schischk. Fine-leaved S<strong>and</strong>wort HA A,B,F,H,I + Stellaria media (L.) Vill. Ranunculaceae Chickweed HA A,B,F,H,I + Clematis vitalba L. Papaveraceae Traveller’s Joy S F,G,H,I,J,K +++ Chelidonium majus L. Greater Cel<strong>and</strong>ine HP A,F,H,I ++ Fumaria o Capparidaceae cinalis L. Common Fumitory HA A,B,D,F,H,I + Capparis spinosa L. Cruciferae Caper S B,C,D,G ++++ Cheiranthus cheiri L. Wall ower HP A,B,C,D,E,F,H,I +++ Diplotaxis muralis (L.) DC. Wall Rocket HA A,F,E,I + Draba muralis L. Wall Whitlow Grass HA A,C,H,I + Matthiola incana (L.) R.Br. Stock HP A,B,C,E,F,H,I +++ Sinapis arvensis L. Crassulaceae Charlock HA A,E,F,G,H ++ Sedum album L. White Stonecrop HP B,C,D,E,F,G,H,I + Sedum dasyphyllum L. Thick-leaved Stonecrop HP B,C,D,E,F,G,H,I + Umbilicus rupestris (Salisb.) D<strong>and</strong>y Rosaceae Pennywort HP B,C,D,E,F,G,H,I + Rubus sp. Leguminosae Blackberry S F,G,H,I,J,K +++ Robinia pseudacacia L. Euphorbiaceae Acacia T A,E,I,J,K ++++ Mercurialis annua L. Simaroubaceae Annual Mercury HA A,E,F,H,I + Ailanthus altissima (Miller) Swingle Celastraceae Tree of Heaven S=T A,E,I,J,K ++++ Euonymus europaeus L. Rhamnaceae Spindle-tree T A,E,I,J,K +++ Rhamnus alaternus L. Guttiferae Buckthom S A,E,I,J,K +++ Hypericum perforatum L. Araliaceae Common St John’s Wort HP A,B,C,D,E,F,H,I + Hedera helix L. Oleaceae Ivy S A,B,C,D,G,J,K ++++ Syringa vulgaris L. Boraginaceae Lilac T A,E,I,J,K +++ Echium vulgare L. Labiatae Vipers’ Bugloss HP C,E,F,G,H,J + Calamintha nepeta (L.) Savi Lesser Calamint HP A,B,C,D,E,H,I,J + Lamium amplexicaule L. Henbit HA A,B,C,D,E,H,I,J + Micromeria graeca (L.) Bentham HP A,B,C,D,E,H,I,J +
Page 1 and 2: Abstract Lichens <
Page 3 and 4: Plate 1. (a) Statue in archaeologic
Page 5 and 6: Fig. 3. Di erent structures of vege
Page 7: e avoided on windy days and
Page 10 and 11: Fig. 6. The stages of a second mode
Page 14 and 15: Table 1. Continued Families <strong
Page 16 and 17: Corball, R., Paz-Bermudez, G., Sanc

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