252 THE BOTANICAL REVIEW
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252
The Botanical Review 69(3): 252–268
Vegetation Ecology and Conservation on Tuscan Ultramafic Soils
ALESSANDRO CHIARUCCI
Dipartimento di Scienze Ambientali “G. Sarfatti”
Università di Siena
I-53100 Siena, Italy
I. Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
II. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
III. Notes on Historical Studies in Geobotany . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
IV. Floristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
V. Vegetation Structure and Composition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
A. Garigues and Grasslands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
B. Scrub and Woods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
C. Conifer Plantations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
VI. Environmental Factors Associated with Vegetation Dynamics . . . . . . . . . . . . . . . . . . 260
VII. Fertilization Experiments and Monitoring of Permanent Plots . . . . . . . . . . . . . . . . . . 263
VIII. Conservation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
IX. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
X. Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
I. Abstract
This article provides a review of studies concerning the floristics, vegetation description
and ecology of the ultramafic (serpentine) soils of Tuscany, central Italy. After a concise history
of geobotanical research on Tuscan ultramafic outcrops since the end of sixteenth century, the
features of the flora are summarized. The most significant vegetation types are concisely described
and their ecology discussed in the following section. The role of soil nickel toxicity in
limiting vegetation development is reconsidered and appears less important than are drought
and nutrient stress. Drought stress also has a special role during exceptionally dry summers,
which can occasionally occur and significantly reduce vegetation structure by causing the local
extinction of many late-successional species. Nutrient-addition experiments and permanent
plot monitoring provided additional evidence supporting the drought and nutrient stress hypothesis.
The last section of this article discusses the main threats to the conservation of the
unique plant diversity of Tuscan ultramafic environments, the most significant of which are
quarrying and pine plantations. Pine plantations, mostly established for soil amelioration and
erosion control, determine not only the increase in vegetation cover and diversity but also a
trend for serpentine endemic and rare species to disappear.
Issued February 200425
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 253
II. Introduction
Ultramafic outcrops in Italy are concentrated along the Alps and the Northern Apennines
(Abbate et al., 1980). A large number of differently sized outcrops are located in Tuscany,
central Italy, from the islands of Elba, Giglio and Gorgona, to the coastline, to the inland
mountain chain of the Apennines (Fig. 1). The mainland outcrops are larger and more diverse.
They are therefore considered more interesting from the botanical and ecological point of view
than are the offshore islands. These outcrops are mostly formed by lherzolitic serpentinites, but
gabbro and basalt are also widespread.
The first botanical investigations of ultramafic areas probably were in Tuscany, and it is
here that the understanding of much of today’s ultramafic plant ecology began. This was due in
part to the long-established botanical studies at the University of Florence, where the first plant
endemic to serpentine was identified and the phenomenon of metal hyperaccumulation first
discovered.
In spite of the large number of studies, the only attempt at a comprehensive treatment was
that of Vegnano Gambi (1992), which discussed ecophysiological problems related to soil
metal toxicity and nickel hyperaccumulation. After centuries of geobotanical studies it appears
timely to provide a comprehensive review of studies concerning the description and ecology of
the vegetation of Tuscan ultramafics. This is the aim of the present article.
The first section of the article provides a historical synthesis of geobotanical studies. This is
followed by a summary of the flora and a description of plant communities described for the
Tuscan ultramafics in the second and third sections, respectively. The fourth section deals with
the main factors related to vegetation ecology and dynamics. Section 5 summarizes recent
work on nutrient-addition experiments and monitoring of permanent plots. Finally, problems
related to conservation issues are discussed.
III. Notes on Historical Studies in Geobotany
The scientific literature on the flora of ultramafic outcrops of Tuscany dates back to the
sixteenth century, when Andrea Cesalpino (1583) wrote about Alyssum bertolonii, “Quarta
fruticosior, & brevior provenit in nudis saxosis, copiosa in Montacuto, juxta lapidem nigrum;
quod multum Amianti nigri complectitur: in alia terra reperire non licet hanc herbam.” Three
centuries later the physician and botanist Gaspare Amidei from Volterra explored some ultramafic
areas of Tuscany, collecting plants to make an herbarium, which is currently preserved at
the Volterra Civic Library. He lectured on the ultramafic flora at the 3rd
Congress of Italian
Scientists (Amidei, 1841) and wrote an article in a local newspaper. He also wrote a stillunpublished
manuscript on the subject (see Pichi Sermolli, 1948). Later, Teodor Caruel, author
of the famous “Prodromo della Flora Toscana” (Caruel, 1860), made some interesting observations
on the flora of Tuscan ultramafic soils. Caruel reported that several species were either
preferential to or exclusive to ultramafic substrates. He also suggested that the soil features
were the cause of the peculiar morphological features shown by many plants in these habitats
(Caruel, 1867, 1871). In this period an international excursion was organized to Monte Ferrato,
an ultramafic site near Prato, during the International Congress of Botany, held in Florence in
1874 (Atti del Congresso Internazionale Botanico, 1876).
In the first half of twentieth century other botanists from the University of Florence investigated
the flora of Tuscan ultramafic areas. Pampanini (1912) published a floristic report on
the small ultramafic outcrop of Montignoso; Adriano Fiori, the author of a well-known Flora
of Italy (Fiori, 1923–1928), compared the flora of Monte Ferrato with that of the neighboring
Calvana limestones (Fiori, 1914) and described the flora of the ultramafic outcrops in the
254 THE BOTANICAL REVIEW
Fig. 1. Ultramafic outcrops of Tuscany, Italy, and surrounding areas.
Cecina Valley (Fiori, 1920). He also aimed to realize a “Flora of the Tuscan Serpentines”
(Fiori, 1920), though he never succeeded. Some years later Albinia Messeri described the
flora and vegetation of Monte Ferrato (Messeri, 1936); and Rodolfo Pichi Sermolli, the soil,
flora and vegetation of the Upper Tiber Valley ultramafics (Pichi Sermolli, 1948). The article
by Pichi Sermolli is still regarded as a classic of serpentine ecology. In 1940 Corti described
the vegetation of ultramafics of Elba Island in a botanical excursion report; however, Elba
has no serpentine endemics. During this period Sambo (1927, 1931) and Cengia Sambo (1937)
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 255
published floristic data on lichens and fungi of the Monte Ferrato. In 1934 the seventh international
phytogeographical excursion was again on Monte Ferrato (Negri et al., 1934).
After World War II the plant ecology of Tuscan ultramafics was made known mainly by the
work of Ornella Vergano Gambi and colleagues. The phenomenon of nickel hyperaccumulation
by plants was discovered by Minguzzi and Vergnano (1948) in Alyssum bertolonii, the same
plant species described as lunaria quarta by Andrea Cesalpino (1583). In the following years
they carried out many studies on the ecophysiology of A. bertolonii and other serpentine plants
in relation to soil metal content, with a special regard for nickel (for a review, see Vergnano
Gambi, 1992). A few descriptive articles were also published on flora and vegetation during
this period: floristic data on the Cecina Valley ultramafics (Vergnano, 1953) as well as short,
descriptive reports on the bryophytes (Cortini Pedrotti, 1974), flora (Arrigoni, 1974) and vegetation
(Corti, 1974) of Monte Ferrato. A phytosociological description of the garigues and
grasslands of Monte Ferrato was published by Arrigoni et al. (1983). Some cytotaxonomical
and chorological data of serpentine endemics were provided by Arrigoni et al. (1976, 1980). In
two articles on element analysis in soils and plants, Sasse (1979a, 1979b) observed that the
richest and closest vegetation types were related to soil with the lowest nickel content, but no
data on vegetation were offered.Athird international excursion was organized on Monte Ferrato
during an OPTIMA meeting, held in Florence (Arrigoni et al., 1977).
In recent decades interest in geobotanical studies on Tuscan ultramafic areas has been renewed.
New floristic data were compiled by Ansaldo et al. (1988) and Zocco Pisana and Tomei
(1990) for the Livorno Hills and by Chiarucci et al. (1994) for the Siena province. Descriptive
studies were published on the vegetation of the garigue plant communities growing over all
outcrops (Chiarucci et al., 1995), on grasslands of the Upper Tiber Valley (Viciani et al., 2002)
and on Juniperus scrub communities (Chiarucci et al., 1998b) growing over all outcrops. The
vegetation dynamics at the Murlo site in Siena province were investigated by Chiarucci (1994).
In recent years studies of the relationship between environment and vegetation have been carried
out by researchers from the University of Siena. These studies specifically investigated the
effects of pine plantations on natural plant communities (Chiarucci & De Dominicis, 1995;
Chiarucci, 1996; Chiarucci et al., 1996) and the relationships between edaphic and physical
properties of the site and vegetation structure and composition (Chiarucci et al., 1998a, 1998d,
2001). Manipulative studies, with nutrient additions to natural plant communities, have investigated
the effects of nutrients on species diversity and productivity (Chiarucci et al., 1998a,
1999a, 1999b). Most recently, a checklist of all the plants reported from all the Tuscan ultramafics
between 1841 and 1998 was published (Chiarucci & De Dominicis, 2001).
IV. Floristics
The checklist compiled by Chiarucci and De Dominicis (2001) consisted of 809 subgeneric
taxa; i.e., 14.5% of the entire Italian flora. The families with the highest representation are
listed in Table I. The relative importance of the families found in the Tuscan ultramafics is
similar to that found on the ultramafics of northern Apennines (Ferrari et al., 1991). Analysis of
the Raunkiaer life-form spectrum (Table II) shows that 40% of all flora consist of hemicryptophytes,
roughly the same proportion as for the Tuscan and Italian floras (Pignatti, 1994).
In comparison with the Northern Apennine ultramafics (Ferrari et al., 1991), there was a higher
proportion of therophytes and a lower proportion of hemicryptophytes (Table II), possibly a
reflection of the warmer and dryer climate of Tuscany (Chiarucci & De Dominicis, 2001).
Eleven serpentine endemic taxa are known from Tuscany (Table III). Among these, Stipa
etrusca Moraldo and Biscutella pichiana Raff. ssp. pichiana were only recently described as
256 THE BOTANICAL REVIEW
autonomous taxa (Moraldo, 1986; Raffaelli & Fiesoli, 1993). Twelve taxa are considered locally
serpentine preferential (Table III). Not much is known about the distribution of most of
these taxa; however, the single locality of Stipa tirsa Steven is known to be on the serpentine of
Upper Tiber Valley (Pichi Sermolli, 1948; Pignatti, 1982; Moraldo, 1986), where it is locally
endangered by pine afforestation (Chiarucci et al., 1996). Other interesting taxa found on Tuscan
serpentine are in need of more in-depth taxonomic investigations. Among these are a taxon of
Linum belonging to the L. gr. alpinum, an Anthemis close to A. montana L. (Chiarucci et al.,
1998d) and a Sesleria close to S. insularis Sommier (Chiarucci et al., 1998d; Rossi & Ubaldi,
1995). These taxa are likely to be restricted to ultramafic outcrops of Tuscany and are presently
known from only one (Anthemis) or two (Linum and Sesleria) sites.
Table I
Richest families of the flora of ultramafic outcrops
in Tuscany
Family
Number
of taxa
Percentage
of the
flora
Compositae 107 12.6
Graminaceae 99 11.6
Leguminosae 89 10.4
Caryophyllaceae 43 5.0
Rosaceae 42 4.9
Labiatae 38 4.5
Umbelliferae 28 3.3
Cruciferae 27 3.2
Orchidaceae 25 2.9
Cyperaceae 21 2.5
Liliaceae 21 2.5
Scrophulariaceae 20 2.3
Ranunculaceae 18 2.1
Source: Chiarucci & De Dominicis, 2001.
Table II
The life-form spectrum of the total flora recorded for Tuscan ultramafics, compared with
the life-form spectra of the Northern Apennine ultramafics (Ferrari et al., 1991),
the flora of Tuscany and the flora of Italy (Pignatti, 1994)
Life-form
Number
of taxa
Percentage
of the flora
Northern
Apennine
ultramafics
(%)
Flora of
Tuscany
(%)
Flora of
Italy
(%)
Therophytes 222 27.4 17.7 30.7 25.1
Geophytes 98 12.2 10.3 14.1 12.1
Idrophytes 2 0.2 0.0 2.7 2.6
Hemicryptophytes 324 40.0 52.0 37.5 41.7
Chamaephytes 60 7.4 9.2 6.2 10.3
Phanerophytes 103 12.8 10.8 5.8 8.5
Total 809 100.0 100.0 100.0 100.0
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 257
V. Vegetation Structure and Composition
A. GARIGUES AND GRASSLANDS
Open vegetation types, mainly garigues and steppe grasslands, are the habitat of most serpentine
endemics and rare species. Garigues, on shallow soils, were first described on Monte
Ferrato by Messeri (1936) as “vegetation of stony grounds.” Later Pichi Sermolli (1948) described
this vegetation type, in the Upper Tiber Valley, as an “Alyssum bertolonii chamaephytic
community.” The relevés of these authors, sampled by the Raunkiaer method, were used by
Ernst (1974) to describe the association Alyssetum bertolonii as belonging to the class Violetaea
calaminariae. Arrigoni et al. (1983) remarked that Ernst’s table gave no precise indication of
the relevés taken from the original data, thus preventing lectotypification of the name (Art. 37
of the C.P.N.; Barkman et al., 1986), and that Ernst’s unclear taxonomic interpretation of some
critical species groups, such as Festuca ovina L. s.l., Euphorbia nicaeensis All. s.l., Centaurea
paniculata L. s.l. and Stachys recta L. s.l. rendered it a useless syntaxon. These authors proceeded,
therefore, to describe the same vegetation type from Monte Ferrato as Armerio-Alyssetum
bertoloni. This association was later found on all of the main ultramafic outcrops in Tuscany,
and two subassociations were recognized: typicum, in inland areas, and euphorbietosum spinosae,
in areas closer to the coast and the southernmost areas (Chiarucci et al., 1995). Typical features
of the garigue plant communities are: sparse plant cover (20–60%), low species richness, floristic
homogeneity and the presence of several endemic and rare species (Chiarucci et al.,
1995). Similar vegetation types, with floristic differences mostly due to endemic species, are
Table III
Serpentine endemics and locally serpentine-preferential plants
Serpentine endemics
Alyssum bertolonii Desv.
Armeria denticulata (Bertol.) DC.
Asplenium cuneifolium Viv.
Biscutella pichiana Raff. ssp. pichiana
Centaurea aplolepa Moretti ssp. carueliana (Micheletti) Dostal
Euphorbia nicaeensis All. ssp. prostrata (Fiori) Arrigoni
Leucanthemum pachyphyllum Marchi et Illuminati
Minuartia laricifolia (L.) Sch. et Th. ssp. ophiolithica Pignatti
Stachys recta L. ssp. serpentini (Fiori) Arrigoni
Stipa etrusca Moraldo
Thymus acicularis W. et K. var. ophioliticus Lacaita
Locally serpentine-preferential plants
Artemisia saxatilis W. et K.
Euphorbia spinosa L. ssp. spinosa
Festuca inops De Not.
Festuca robustifolia Mgf.-Dbg.
Genista januensis Viv.
Iris lutescens Lam.
Notholaena marantae (L.) Domin ssp. marantae
Onosma echioides L.
Plantago holosteum Scop.
Silene paradoxa L.
Stipa tirsa Steven
Trinia glauca (L.) Dumort. ssp. glauca
258 THE BOTANICAL REVIEW
also known from the ultramafic areas of Liguria (Furrer & Hofmann, 1969; Nowak, 1987;
Mariotti, 1994) and Emilia-Romagna (Pignatti & Pignatti, 1977).
On slightly more developed soil the chamaephytic vegetation of garigues may develop into
steppe grasslands. Plant cover is higher, and the most abundant species are grasses, such as
Festuca inops, F. robustifolia, Bromus erectus, Koeleria splendens, Danthonia alpina, and
sedges, such as Carex humilis. These steppes have been reported in almost all of the Tuscan
ultramafic areas, with differences in the dominant species and floristic composition, but they
are more frequent in the inland sites: Monte Ferrato (Messeri, 1936; Arrigoni et al., 1983;
Chiarucci et al., 1998c, 1998d) and the Upper Tiber Valley (Pichi Sermolli, 1948; Chiarucci et
al., 1996, 1998d; Viciani et al., 2002). Festuca robustifolia and F. inops usually dominate in
the less developed soils, whereas Bromus erectus and Danthonia alpina dominate in the more
developed ones (Messeri, 1936; Pichi Sermolli, 1948; Chiarucci et al., 1998c, 1998d). In the
Upper Tiber Valley Viciani et al. (2002) described these grasslands as a vegetation type exclusive
to ultramafic substrates, namely the Festuco robustifoliae–Caricetum humilis. These grasslands
may be dominated locally by Stipa etrusca, a recently described species endemic to
Tuscan and Emilian ultramafics and to some volcanic soils of northern Latium (Moraldo, 1986).
In some Upper Tiber Valley sites these grasslands are dominated by Stipa tirsa (Pichi Sermolli,
1948; Chiarucci et al., 1996; Viciani et al., 2002), a Euro-Siberian species found in only a few
places in Italy. Pignatti (1982) reported the Upper Tiber Valley as its only Italian locality, while
Moraldo (1986) stated that it grew in a few places in Italy but is abundant only in the Upper
Tiber Valley ultramafic and a site in northern Italy. In some situations, with more organic
matter or after burning, Brachypodium rupestre may form dense clumps within these grasslands,
generally associated with very low species richness (Chiarucci et al., 1998c).
In the coastal areas, such as the Cecina Valley and Livorno Hills, similar grasslands can
locally be found, where communities dominated by chamaephytic species, such as Euphorbia
spinosa, are more abundant than true grasses (Chiarucci et al., 1995). Compared with the garigues,
grasslands have fewer endemics and more central European species (Arrigoni et al.,
1983; Chiarucci et al., 1995, 1998c, 1998d).
B. SCRUB AND WOODS
Unlike garigues, which are floristically very homogeneous on all outcrops, woody plant communities
are more diverse, in relation to altitude and distance from the sea (Chiarucci et al., 1998d).
Messeri (1936) provided the first complete description of woodland communities in the Monte
Ferrato area. She described woodlands dominated by Pinus pinaster, Quercus pubescens, Q. ilex
and Q. cerris, located in “stations with sufficiently deep soil.” Well-structured woodlands, with a
rich shrub layer of Erica scoparia, Calluna vulgaris, Ulex europaeus, Genista pilosa and other
species, were, however, found mainly on gabbro. Pichi Sermolli (1948) reported Juniperus oxycedrus
ssp. oxycedrus and Erica scoparia scrub communities and woodlands dominated by Quercus
pubescens and Q. cerris and by Fagus sylvatica in the Upper Tiber Valley. On pure serpentinite,
however, woodlands occur only in areas close to lithological contacts with limestone or other
substrata. Pichi Sermolli (1948) observed that woodlands do not develop directly from typical
ultramafic plant communities but by limited colonization of marginal areas by woody species from
nearby sites. On soils originating from gabbro, scrub and woodlands similar to those growing on
serpentinite are much more common. Chestnut woodlands were also reported from mixed soils
originating from serpentinite, gabbro and diabase.
Chiarucci et al. (1998d) suggested that the scrub communities dominated by Juniperus
oxycedrus ssp. oxycedrus may be the most developed vegetation stage on xeric slopes of the
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 259
Mediterranean ultramafic outcrops. These scrub communities may be sparse within garigues
and grasslands or dense and with the presence of broad-leaved woodland species. The more
typical aspect of this vegetation type has recently been described as a new association, named
Carici humilis–Juniperetum oxycedri (Chiarucci et al., 1998b). The successional dynamics of
these scrub communities toward closed maquis and woodland communities is prevented by
nutrient deficiency and periodic reversions caused by stress factors such as extreme drought
(Chiarucci et al., 1998d).
Where the environmental conditions are less harsh and drought stresses less frequent, the
juniper communities can develop into broad-leaved maquis and woodland. Broad-leaved evergreen
maquis, belonging to the Viburno–Quercetum ilicis ericetosum, have been reported on
ultramafic soils, originating mainly from serpentinites, in the Livorno Hills (Marchiori &
Tornadore Marchiori, 1977), the Murlo area (Chiarucci, 1994) and the Cecina Valley (Chiarucci
et al., 1998d). Evergreen woods, with a structure determined by frequent cutting and a near
absence of deciduous species, typically belong to this syntaxon on other soil types (Braun
Blanquet, 1952). More developed and structured woodlands in the Murlo area have been ascribed
to the Viburno–Quercetum ilicis ornetosum (Chiarucci, 1994). Because of their species
composition, almost entirely evergreen species, these woodlands contrast with other Quercus
ilex woodlands of this part of Tuscany, which have a mixture of evergreen and deciduous
species (De Dominicis, 1973), being more similar to Q. ilex woodlands in coastal areas (Pignatti
& Pignatti, 1968; De Dominicis & Barluzzi, 1983). Similar woodlands have also been reported
for the Cecina Valley and the Livorno Hills (Chiarucci et al., 1998d).
C. CONIFER PLANTATIONS
Although natural woodlands can be found (Messeri, 1936; Pichi Sermolli, 1948; Chiarucci
et al., 1998d), the most widespread woodlands on Tuscan ultramafics were conifer plantations.
Because of their low productivity, ultramafic soils of Tuscany are frequently planted with conifers,
mainly pines (Pinus pinaster, P. pinea and P. nigra). Pine woodlands originating from
these plantations are typically low and scattered (Arrigoni et al., 1983; Chiarucci & De Dominicis,
1995), mainly due to soil nutritional deficiencies (Angelone et al., 1993; Vaselli et al., 1993).
The effects of pine plantations on natural vegetation have only recently been investigated. In
the shallow soils of Pievescola it was found that pine plantations strongly affect the natural
plant communities, leading to an increase in total plant cover and species diversity, with a
higher number of species showing intermediate abundance (Fig. 2). However, pine plantations
caused the disappearance of some endemics and the spread of many alien species from surrounding
areas (Chiarucci & De Dominicis, 1995; Chiarucci, 1996). The vegetation, originally
a garigue with low ground cover, developed into a grassland dominated by Bromus erectus,
Festuca robustifolia and Danthonia alpina, resembling some natural grasslands, with species
diversity higher than that in garigues. Shrub species were also promoted by pine canopy, and
successional dynamics toward a woodland community is likely. The disappearance of the less
competitive species, typical of ultramafic soils, and the development of structured, species-rich
grassland, less dependent on soil type, are closely related to the formation of an organic soil
layer. Pine cover has a positive influence on soil genesis, providing protection against erosion
and supplying organic matter that binds soil particles. Chiarucci (1996) hypothesized that an
increase in nutrient input, mainly nitrogen, under tree cover may also be due to the intercepting
action of the tree canopies with respect to dry deposition (see, e.g., Van Breemen & Van Dijk,
1988). Similar changes were observed in the pinewood understory of Monte Ferrato (Chiarucci
et al., 1998c) and the Upper Tiber Valley (Chiarucci et al., 1996, 2001).
260 THE BOTANICAL REVIEW
Fig. 2. Relative distributions of species abundance in natural garigue vegetation (left curve, circles),
in sparse pine plantations (center curve, squares) and dense pine plantations (right curve, triangles).
VI. Environmental Factors Associated with Vegetation Dynamics
Recent articles (Chiarucci et al., 1998c, 1998d, 2001) indicate that the exchangeable fraction
of metals is higher in the soil under the more developed and structured communities, both
in natural (maquis and woodland) and anthropogenic (pine plantation) habitats, suggesting that
soil metal content is not the most important limiting factor for the vegetation. For example, the
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 261
soluble fraction of chromium is generally too small to affect vegetation (Pandolfini & Pancaro,
1992; Chiarucci et al., 1998c, 1998d, 2001). The increased availability of metals in the soil
under the more developed vegetation types may be a direct consequence of the lower pH in
these areas (Robinson et al., 1996), as shown in Figure 3. Closed woody vegetation is likely to
lower the soil pH, as locally moister conditions increase humic decay acidifying the soil. This
in turn induces a higher availability of metals.
Recent pedological (Angelone et al., 1991, 1993) and vegetation (Chiarucci et al., 1998c,
1998d, 2001) studies contradict the long-held assumption that metal content is the most important
limiting factor in Tuscan ultramafic soils. In contrast to previous studies, the importance of
the metal fraction available to plants rather than the total metal concentrations was emphasized.
Other authors have made similar observations in well-studied serpentine sites. Carter et al.
(1987) reported that nickel was not the cause of the low fertility of serpentine soils in the Keen
of Hamar, Shetland Islands. Kruckeberg (1992) did not find any evidence that cobalt, chromium,
iron and nickel affect plant growth in the ultramafic soils of western North America. In
New Zealand, Lee (1992) observed that only in some southern ultramafics is nickel toxicity
likely to reduce plant growth. Proctor and Nagy’s (1992) review suggested that many assumptions
about the role of nickel in causing the unusual serpentine vegetation are unfounded, and
in-depth studies have often disproved the importance of this element.
One of the most important limiting factors for the vegetation of Tuscan ultramafic soils
appears to be drought stress due to topographical position. Water stress, together with soil
nutritional deficiencies, constantly limit vegetation development. In both Mediterranean and
inland sites, the annual solar radiation was found to be significantly higher in juniper scrub
communities, a relatively undisturbed vegetation type where the serpentine endemics grow,
than in sites with a proper woodland vegetation (Chiarucci et al., 1998c, 1998d). Juniper scrub
communities, when sufficiently dense, can be colonized by many forest species; i.e., evergreen
Fig. 3. Exchangeable nickel concentration in the soil (␮g g–1
) as a function of soil pH. Data from 80
plots in different ultramafic areas of Tuscany sampled by Chiarucci et al. (1998d).
262 THE BOTANICAL REVIEW
species such as Quercus ilex, Phillyrea latifolia, Arbutus unedo and Rhamnus alaternus in
Mediterranean sites (Chiarucci et al., 1998d) and deciduous species such as Fraxinus ornus
and Quercus pubescens in inland sites (Messeri, 1936; Pichi Sermolli, 1948; Chiarucci et al.,
1998c, 1998d). This development of more structured woody communities improves soil structure
and fertility, thus allowing better plant growth through positive feedback. Natural dynamics
toward more developed vegetation types would lead to the disappearance of the endemic
species, linked to the less evolved soils, and the spread of the more competitive forest species.
However, occasional periodic droughts and other exceptional stresses (e.g., fire) may kill off
forest plant species, creating gaps in the juniper canopies, which can be colonized by xerophile
and heliophile plants, such as the serpentine endemics, interrupting vegetation dynamics and
promoting soil erosion. This “pulsating dynamics model” (Fig. 4) is likely to represent the
driving force (Grime, 1990; Van der Maarel, 1996) behind the permanence of pioneer vegetation
types, in which Alyssum bertolonii and the other serpentine endemic and rare species may
persist within a patchy landscape dominated by juniper scrub communities (Chiarucci et al.,
1998d).
In addition, the garigues were found to be located on soils with the lowest concentrations of
potentially toxic metals and in sites with a wide range of physical conditions (Chiarucci et al.,
1998d). The apparent lack of correlation between environmental limiting factors and garigues
suggests that their commonness has been partially favored by human disturbance through destruction
of more developed vegetation types, such as the juniper scrub communities and the
evergreen maquis. For the serpentine soils of the Keen of Hamar, where rainfall is distributed
throughout the year, Carter et al. (1987) suggested that a summer drought of seven or more
consecutive days, which happen on average once every three to five years, may exhaust the soil
water reserve. This dry period is considered one of the most significant causes of retarded plant
colonization and vegetation succession. In Tuscany, located in the middle of the Mediterranean
area, summer droughts may be much longer and are likely to have significant effects on vegetation
dynamics. Permanent plots have been set up to test this hypothesis (periodic drought
stress). The exceptional drought of summer 1998 has already provided some support for this
hypothesis.Adieback of many xerophile shrubs, such as Cistus salvifolius and C. monspeliensis,
Fig. 4. Scheme of the “pulsating dynamics model” proposed by Chiarucci et al. (1998d), according to
which vegetation development is occasionally interrupted by exceptional drought stresses.
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 263
as well as of branches of taller shrubs, such as Erica scoparia, Juniperus oxycedrus ssp. oxycedrus
and Arbutus unedo, was observed (Chiarucci, unpubl. data).
VII. Fertilization Experiments and Monitoring of Permanent Plots
The evidence that soil metal toxicity is not the most important limiting factor for the
vegetation of Tuscan ultramafics has been reenforced by recent nutrient-addition experiments
(Chiarucci et al., 1998a, 1999a, 1999b). The addition of small amounts of nitrogen, phosphorus
and potassium to a garigue plant community induced a significant increase in ground
cover (Chiarucci et al., 1998a) and biomass production (Chiarucci et al., 1999a) after two
years (Fig. 5). A higher nutrient availability has also been reported to alleviate the effects of
drought (Grime, 1990). Proctor and Nagy (1992) considered the low nutrient content of the
soil a “key feature” in causing serpentine infertility in many areas. On the other hand, Cadeficiency
or the Mg/Ca ratio, considered very important limiting factors for serpentine vegetation
(Brooks, 1987; Baker et al., 1992; Roberts & Proctor, 1992), did not appear as very
important in these ultramafic soils; the addition of calcium, alone or with nitrogen, phosphorus
and potassium (NPK), led to a nonsignificant increase (Fig. 5) of cover and biomass,
compared with the control plots and the NPK-added plots (Chiarucci et al., 1999a). This is
likely to be due to the fact that in these soils the Mg/Ca quotient is relatively low, averaging
from 1.5 to 3.0 (Chiarucci et al., 1999a). The addition of fertilizer favored the growth of
species already present within the plots, rather than colonization by other species, as observed
in other ultramafic areas following nutrient addition; e.g., California (Huenneke et al.,
1990). In fact, in an analysis of three years of cover data of fertilized plots, Chiarucci et al.
(1998a) showed that nutrient addition significantly improved the cover of the species already
present without any significant colonization. The data from the fertilization experiment by
Chiarucci et al (1998a, 1999a) were employed to study the use of Alyssum bertolonii for
Fig. 5. Total biomass harvested per 1m2
plot (geometric mean Ϯ standard deviation) after two years of
nutrient addition in the Murlo area by Chiarucci et al. (1999a).
264 THE BOTANICAL REVIEW
Fig. 6. Five years of data on species richness per 4m2
plots (mean value of four plots) in the nutrientaddition
experiment at Pievescola, Italy. Nutrients were added in the autumn of 1994 and of 1995, and
species richness was sampled every spring. Species richness was linked more to climatic variation than to
fertilization (Chiarucci, unpubl. data). Key: circles = control plots; squares = plots fertilized with potassium;
diamonds = plots fertilized with nitrogen; triangles = plots fertilized with phosphorus.
extracting nickel from serpentine soils, with phytoming and phytoremediation aims (Robinson
et al., 1997; Brooks et al., 1998, 2002).
In another experiment performed with single nutrient treatments of nitrogen, phosphorus
and potassium, Chiarucci (unpubl. data) found that phosphorus was the main limiting factor
for this Tuscan ultramafic vegetation. Treatments were performed for two years, during which
time total plant cover continued to increase: from about 20% before nutrient addition to more
than 45% two years after the cessation of treatments. Species richness in this study was found
to be related more to interannual climatic variations than to nutrient addition (Fig. 6), confirming
the importance of drought in the structuring of serpentine plant communities. Increase of
plant cover in the years after the cessation of nutrient addition similar to those found in this
study have also been reported for other serpentine sites, such as the Keen of Hamar (Carter et
al., 1988; Slingsby, 1991).
VIII. Conservation
The main threats to the conservation of ultramafic environments of Tuscany are quarrying,
conifer plantations and eutrophication. Since ultramafic rocks, especially serpentinites, represent
inert materials important in certain industrial processes, they are often quarried. Ultramafic
rocks are also used as building material: Monte Ferrato serpentinite is a prestigious marble,
known as “verde e nero di Prato” (green and black marble of Prato), widely used in decorative
elements in Tuscan buildings and monuments. Although a few large quarries are still active,
quarrying was once more widespread, and smaller quarries are presently worked only
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 265
sporadically or have been abandoned. The problem was recognized in the 1970s, in a motion
proposed at the second OPTIMA Congress in 1977 (Anonymous, 1979).
The greatest threat to biodiversity conservation in Tuscan ultramafics, however, is presently
soil eutrophication due to the increased nutrient content of rainfall and the effects of tree cover
in afforestation. Vegetation changes similar to those reported by Chiarucci & De Dominicis
(1995), Chiarucci (1996) and Chiarucci et al. (1996), have been described by Carter et al.
(1987) at Keen of Hamar as a consequence of eutrophication from winter feeding of stock.
Rare species totally disappeared, and closed grassland dominated by Agrostis spp. and Festuca
spp. developed. The cessation of nutrient input did not lead to disappearance of the grassland
and reversion to original vegetation, which was achieved only by mechanical removal of the
established vegetation and the soil that had developed (Slingsby, 1991).
The survival of the typical ultramafic vegetation of Tuscany is seriously threatened in areas
with intense afforestation.Artificial removal of the pines would probably not sufficiently modify
the established vegetation because of the organic matter accumulated and the structure of vegetation
that developed. In many sites, to enable serpentine plants to spread again it is probably
necessary to remove the organic layer of soil together with the pines (Chiarucci & De Dominicis,
1995). Indeed, conservation of the endemic ultramafic vegetation of Tuscany calls for a general
examination of the interests connected with pinewood forestry and biodiversity conservation.
If we wish to conserve this typical vegetation, ultramafic areas must not be planted for soil
protection or timber production, and some areas should be rehabilitated to the original vegetation
types.
In conclusion, it should be noted that changes are under way. Parts of the ultramafic habitat
of Tuscany are presently protected as nature reserves, and some projects are undergoing restoration
of degraded habitat: In the Upper Tiber Valley a project funded by the EU Life program
was recently promoted to restore a Stipa tirsa grassland in which pines had been planted in
preceding decades (see Chiarucci et al., 2001).
IX. Acknowledgments
I wish to express my gratitude to all of the people who have helped me over the years and
have collaborated with parts of my “serpentine project.” First, I wish to thank Prof. V. De
Dominicis for his friendly support and encouragement and the late Prof. R. R. Brooks, whose
eclectic and friendly nature was one of the most important findings of my serpentine experience.
Many other persons and colleagues have supported me, too. In particular, I am grateful
to Prof. M. G. Mariotti, Prof. R. E. G. Pichi Sermolli, Dr. S. Maccherini, Dr. B. H. Robinson,
Dr. E. Busoni, Mr. V. Gonnelli, Dr. F. Selvi, Dr. B. Foggi, Dr. A. Lombini, Dr. A. Angiolini
and Dr. S. Loppi for useful discussions and suggestions. Dr. G. Calvani, Dr. E. Tesi, Dr.
D. Morrocchi, Dr. P. Castagnini, Dr. M. Marchiani and Dr. M. Riccucci helped me solve
many problems related to the field activities. Dr. B. Anderson revised the language and made
considerable criticism to a previous version of the manuscript. Finally, I wish to acknowledge
deeply Dr. Ilaria Bonini, who, with love and patience, followed me in the many adventures I
imagined and started—and some that I finished.
X. Literature Cited
Abbate, E., V. Bortolotti & G. Principi. 1980. Apennine ophiolites: A peculiar oceanic crust. Ofioliti,
special issue, 1: 59–96.
Amidei, G. 1841. Specie di piante osservate nei terreni serpentinosi. P. 523 in Atti 3a Riunione Scienziati
Italiani. Florence.
266 THE BOTANICAL REVIEW
Angelone, M., O. Vaselli, C. Bini & M. G. Pancani. 1991. Total and EDTA-extractable element contents
in ophiolitic soils from Tuscany (Italy). Zeit. Pflanz. Bodenk. 154: 217–223.
———, ———, ———, ——— & N. Coradossi. 1993. Pedogeochemical evolution and trace elements
availability to plants in ophiolitic soils. Sci. Total Environm. 129: 291–309.
Anonymous. 1979. Motions: For the saveguard of Monte Ferrato. Webbia 34: 24–25.
Ansaldo, C., F. Garbari & S. Marchiori. 1988.Aspetti floristici e vegetazionali della Valle della Sambuca
(Colline Livornesi). Quad. Mus. St. Nat. Livorno 9: 45–65.
Arrigoni, P. V. 1974. La flora del Monte Ferrato. Atti Soc. Tosc. Sci. Nat., Mem., Ser. B, 81: 1–10.
———, M. Giannerini & B. Mori. 1976. Contributi citotassonomici e corologici alla conoscenza di
alcune serpentinofite toscane. Giorn. Bot. Ital. 110: 438–439.
———, C. Ricceri & O. Vergnano Gambi. 1977. Excursion to Monte Ferrato (25 May 1977). Webbia
37: 27–31.
———, M. Giannerini & B. Mori. 1980. Numeri cromosomici per la flora italiana: 714–721. Inform.
Bot. Ital. 12: 137–143.
———, C. Ricceri & A. Mazzanti. 1983. La vegetazione serpentinicola del Monte Ferrato di Prato in
Toscana. Centro di Scienze Naturali, Prato.
Atti del Congresso Internazionale Botanico. 1876. Gita a Monteferrato, 17.5.1874. Regia Società Toscana
di Orticoltura, Florence.
Baker, A. J. M., J. Proctor & R. D. Reeves (eds.). 1992. The vegetation of ultramafic (serpentine) soils.
Intercept, Andover, England.
Barkman, J. J., J. Moravec & S. Rauschert. 1986. Code of phytosociological nomenclature. Ed. 2.
Vegetatio 67: 145–195.
Braun Blanquet, J. 1952. Les Groupements végétaux de la France méditerranéenne. Macabet Frères,
Vaison la Romaine, Vaucluse.
Brooks, R. R. 1987. Serpentine and its vegetation: A multidisciplinary approach. Dioscorides, Portland, OR.
———, A. Chiarucci & T. Jaffré. 1998. Revegetation and stabilisation of mine dumps and other degraded
terrain. Pp. 227–247 in R. R. Brooks (ed.), Plants that hyperaccumulate heavy metals. CAB
International, Wallingford, England.
———, B. H. Robinson, A. W. Howes & A. Chiarucci. 2002. An evaluation of Berkheya coddii Roessler
and Alyssum bertoloni Desv. for phytoremediation and phytomining of nickel. S. Afr. J. Sci. 97:
558–561.
Carter, S. P., J. Proctor & D. R. Slingsby. 1987. Soil and vegetation of the Keen of Hamar serpentine,
Shetland. J. Ecol. 75: 21–42.
———, ——— & ———. 1988. The effects of fertilisation on part of the Keen of Hamar Serpentine,
Shetland. Trans. Bot. Soc. Edinb. 45: 97–105.
Caruel, T. 1860. Prodromo della Flora Toscana. Le Monnier, Florence.
———. 1867. Sur la flore des gabbres de Toscane. Pp. 58–63 in Actes du Congrés International de
Botanique, Paris.
———. 1871. Flora dei Gabbri di Toscana. Pp. 321–326 in T. Caruel, Statistica botanica della Toscana.
Pellas, Florence.
Cengia Sambo, M. 1937. Osservazioni lichenologiche sul Gruppo del Monte Ferrato. N. Giorn. Bot. Ital.,
n.s., 44: 295–311.
Cesalpino, A. 1583. De Plantis Libris, vol. 16. Florence.
Chiarucci, A. 1994. Successional pathway of Mediterranean ultramafic vegetation in central Italy. Acta
Bot. Croat. 53: 83–94.
———. 1996. Species diversity in plant communities on ultramafic soils in relation to pine afforestation.
J. Veg. Sci. 7: 57–62.
——— & V. De Dominicis. 1995. Effects of pine plantations on ultramafic vegetation of central Italy. Isr.
J. Plant Sci. 43: 7–20.
——— & ———. 2001. The diversity and richness of the serpentine flora of Tuscany. Bocconea 13:
557–560.
———, I. Bonini, S. Maccherini & V. De Dominicis. 1994. Remarks on the ultramafic garigue flora of
two sites of the Siena province, Italy. Atti. Accad. Fisiocritici Siena, Ser. XV, 13: 193–200.
———, B. Foggi & F. Selvi. 1995. Garigue plant communities of ultramafic outcrops of Tuscany (Italy).
Webbia 49: 179–192.
VEGETATION OF TUSCAN ULTRAMAFIC SOILS 267
———, I. Bonini, V. Gonnelli & V. De Dominicis. 1996. The Stipa tirsa communities of Upper Tiber
Valley, Italy and their conservation. Coll. Phytosoc. 24: 305–309.
———, S. Maccherini, I. Bonini & V. De Dominicis. 1998a. Effects of nutrient addition on species
diversity and cover on “serpentine” vegetation. Plant Biosystems 132: 143–150.
———, B. Foggi & F. Selvi. 1998b. The Juniperus oxycedrus ssp. oxycedrus scrub communities of
Tuscan serpentine soils. Atti Soc. Tosc. Sci. Nat., Mem., Ser. B, 105: 51–57.
———, M. Riccucci, C. Celesti & V. De Dominicis. 1998c. Vegetation-environment relationships in the
ultramafic area of Monte Ferrato, Italy. Isr. J. Plant Sci. 46: 213–221.
———, B. H. Robinson, I. Bonini, D. Petit, R. R. Brooks & V. De Dominicis. 1998d. Vegetation of
Tuscan ultramafic soils in relation to edaphic and physical factors. Folia Geobot. 33: 113–131.
———, S. Maccherini, I. Bonini & V. De Dominicis. 1999a. Effects of nutrient addition on community
productivity and structure of serpentine vegetation. Plant Biol. 1: 121–126.
———, J. B. Wilson, B. J. Anderson & V. De Dominicis. 1999b. Cover versus biomass as the estimate
of abundance in examining plant community structure: Does it make a difference to the conclusions?
J. Veg. Sci. 10: 35–42.
———, D. Rocchini, C. Leonzio & V. De Dominicis. 2001. A test of vegetation-environment relationships
in serpentine soils of Tuscany, Italy. Ecol. Res. 16: 627–639.
Corti, R. 1940. Appunti sulla vegetazione dell’Elba, I. Una gita a M. Orello e ai monti tra Rio Alto e
Portolongone, con osservazioni sui distretti ofiolitici dell’isola. N. Giorn. Bot. Ital., n.s., 47: 494–505.
———. 1974. Caratteristiche generali della vegetazione del Monteferrato (Prato). Atti Soc. Tosc. Sci.
Nat., Mem., Ser. B, 81: 32–38.
Cortini Pedrotti, C. 1974. La vegetazione pioniera del Monte Ferrato (Prato). Atti Soc. Tosc. Sci. Nat.,
Mem., Ser. B, 81: 39–44.
De Dominicis, V. 1973. Inquadramento fitosociologico delle leccete dei dintorni di Siena. Giorn. Bot. Ital.
107: 249–262.
——— & C. Barluzzi. 1983. Coenological research on macrofungi in evergreen oak woods in the hills
near Siena (Italy). Vegetatio 54: 177–187.
Ernst, W. 1974. Schwermetallvegetation der Erde. Geobotanica Selecta, vol. 5. Gustav Fisher Verlag,
Stuttgart.
Ferrari, C., A. Lombini & B. Carpené. 1991. Serpentine flora of the Northern Apennines, Italy. Pp.
159–173 in A. J. M. Baker, J. Proctor & R. D. Reeves (eds.), The vegetation of ultramafic (serpentine)
soils. Intercept, Andover, England.
Fiori, A. 1914. La flora dei serpentini della Toscana, II. Confronto fra la Flora del M. Ferrato (serpentino)
e quella della Calvana (calcare alberese). N. Giorn. Bot. Ital., n.s., 21: 216–240.
———. 1920. Rilievi geografici e forestali sulla flora del bacino della Cecina e località finitime. Ann R.
Ist. Sup. For. Naz., Firenze 5: 151–186.
———. 1923–1928. Nuova flora analitica d’Italia, vols. 1–3. Edagricole, Bologna.
Furrer, E. & A. Hofmann. 1969. Das Euphorbietum spinosae-ligusticae, fine Serpentingesellshaft in
Ligurien. Acta Bot. Croat. 28: 81–90.
Grime, J. P. 1990. Mechanisms promoting floristic diversity in calcareous grasslands. Pp. 51–56 in S.
H. Hillier, D. W. H. Walton & D. A. Wells (eds.), Calcareous grasslands: Ecology and management.
Bluntisham Books, Bluntisham, England.
Huenneke, L. F., S. P. Hamburg, R. Koide, H. A. Mooney & P. M. Vitousek. 1990. Effects of soil
resources on plant invasion and community structure in Californian serpentine grassland. Ecology
71: 478–491.
Kruckeberg, A. R. 1992. Plant life of western North American ultramafics. Pp. 31–74 in B. A. Roberts &
J. Proctor (eds.), The ecology of areas with serpentinized rocks: A world view. Kluwer, Dordrecht,
Germany.
Lee, W. G. 1992. The serpentinized areas of New Zealand, their structure and ecology. Pp. 375–417 in
B. A. Roberts & J. Proctor (eds.), The ecology of areas with serpentinized rocks: A world view.
Kluwer, Dordrecht, Germany.
Marchiori, S. & N. Tornadore Marchiori. 1977. Lineamenti vegetazionali del Monte Pelato–
Castiglioncello (Livorno). Atti Soc. Tosc. Sci. Nat., Mem., Ser. B, 84: 7–15.
Mariotti, M. G. 1994. Osservazioni sulle formazioni a Buxus sempervirens e a Genista salzmannii della
Liguria orientale. Mem. Accad. Lunig. Sci. “G. Capellini” 59: 77–125.
268 THE BOTANICAL REVIEW
Messeri, A. 1936. Ricerche sulla vegetazione dei dintorni di Firenze, IV. La vegetazione delle rocce
ofiolitiche del Monte Ferrato (presso Prato). N. Giorn. Bot. Ital., n.s., 43: 277–372.
Minguzzi, C. & O. Vergnano. 1948. Il contenuto di nickel nelle ceneri nelle ceneri di Alyssum bertolonii
Desv. Atti Soc. Tosc. Sci. Nat., Mem., Ser. B, 55: 49–71.
Moraldo, B. 1986. Il genere Stipa L. (Graminaceae) in Italia. Webbia 40: 203–278.
Negri, G., E. Tongiorgi, R. Corti, R. Pampanini & A. Chiarugi. 1934. Septième Excursion Phytogéographique
Internationale, Italie 1934: Guide Itineraire. Tip. M. Ricci, Florence.
Nowak, B. 1987. Untersuchungen zur Vegetation Ostliguriens (Italien). Dissert. Bot. 111: 1–259.
Pampanini, R. 1912. Flora dei serpentini di Montignoso. N. Giorn. Bot. Ital., n.s., 19: 464–466.
Pandolfini, T. & L. Pancaro. 1992. Biogeochemical survey of some ophiolitic outcrops in Tuscany.
Flora 187: 341–351.
Pichi Sermolli, R. 1948. Flora e vegetazione delle serpentine e delle altre ofioliti dell’Alta valle del
Tevere (Toscana). Webbia 6: 1–380.
Pignatti, E. & S. Pignatti. 1968. Die Auswirkungen von Kahlschlag und Brand auf das Quercetum ilicis
von Süd-Toskana, Italien. Folia Geob. Phytotx. 3: 17–46.
——— & ———. 1977. Die vegetation auf serpentin-standorten in den Nördlichen Apenninen. Pp. 113–
124 in Studia phtytologica in honorem jubilantis A. O. Horvát. MTA Pécsi Bizottsága, Pécs, Hungary.
Pignatti, S. 1982. Flora d’Italia, vols. 1–3. Edagricole, Bologna.
———. 1994. Ecologia del paesaggio. UTET, Turin.
Proctor, J. & L. Nagy. 1992. Ultramafic rocks and their vegetation: An overview. Pp. 469–494 in A. J.
M. Baker, J. Proctor & R. D. Reeves (eds.), The vegetation of ultramafic (serpentine) soils. Intercept,
Andover, England.
Raffaelli, M. & P. Fiesoli. 1993. Biscutella L. ser. Laevigatae malin. (Cruciferae) in Toscana: Indagini
morfobiometriche e tassonomiche. Webbia 47: 55–78.
Roberts, B. A. & J. Proctor (eds.). 1992. The ecology of areas with serpentinized rocks: A world view.
Kluwer, Dordrecht, Germany.
Robinson, B. H., R. R. Brooks, J. H. Kirkman, P. E. H. Gregg & P. Gremigni. 1996. Plant-available
elements in soils and their influence on the vegetation over ultramafic (“serpentine”) rocks in New
Zealand. J. Roy. Soc. New Zeal. 26: 455–466.
———, A. Chiarucci, R. R. Brooks, D. Petit, J. H. Kirkman, P. E. H. Gregg & V. De Dominicis.
1997. The nickel hyperaccumulator plant Alyssum bertolonii as a potential agent for phytoremediation
and phytomining of nickel. J. Geochem. Explor. 59: 75–86.
Rossi, G. & D. Ubaldi. 1995. Sulla presenza di Sesleria insularis Sommier nell’Appennino settentrionale.
Arch. Geobot. 1: 171–176.
Sambo, E. 1927. I licheni del M. Ferrato (Toscana). N. Giorn. Bot. Ital., n.s., 34: 333–358.
———. 1931. Macromiceti di Prato in Toscana. N. Giorn. Bot. Ital., n.s., 38: 589–604.
Sasse, F. 1979a. Untersuchungen an Serpentinstandorten in Frankreich, Italien, Oesterreich und der
Bundesrepublik Deutschland, I. Bodenanalysen. Flora 168: 379–395.
———. 1979b. Untersuchungen an Serpentinstandorten in Frankreich, Italien, Oesterreich und der
Bundesrepublik Deutschland, II. Pflanzenanalysen. Flora 168: 578–594.
Slingsby, D. 1991. The Keen of Hamar: A twenty-one year study. Shetland Naturalist 1: 1–12.
Van Breemen, N. & H. F. G. Van Dijk. 1988. Ecosystem effects of atmospheric deposition of N in the
Netherlands. Environm. Poll. 54: 249–274.
Van der Maarel, E. 1996. Vegetation dynamics and dynamic vegetation science. Acta Bot. Neerl. 45:
421–442.
Vaselli, O., C. Bini & M. Del Sette. 1993. Geochemie des eaux lessivantes un sol brun eutrophe (Typic
Xerochrochrept) sous foret en climat tempere. Quad Sci. Suolo, Firenze 5: 75–89.
Vergnano, O. 1953. Erborizzazioni su alcune serpentine della Val di Cecina. N. Giorn. Bot. Ital., n.s., 60:
330–332.
Vergnano Gambi, O. 1992. The distribution and ecology of the vegetation of ultramafic soils in Italy. Pp.
217–248 in B. A. Roberts & J. Proctor (eds.), The ecology of areas with serpentinized rocks: A world
view. Kluwer, Dordrecht, Germany.
Viciani, D., B. Foggi, A. Gabellini & D. Rocchini. 2002. Contributo alla conoscenza delle praterie su
substrati ultramafici dell’Alta Val Tiberina (Toscana orientale, Italia). Fitosociologia 30: 127–134.
Zocco Pisana, L. & P. E. Tomei. 1990. Contributo alla conoscenza della flora livornese: Gli affioramenti
serpentinicoli di Monte Pelato e Poggio alle Fate. Quad. Mus. St. Nat. Livorno 11: 1–24.