Research Paper |
Corresponding author: Dario Ciaramella ( dario.ciaramella93@gmail.com ) Academic editor: Jozef Šibík
© 2024 Dario Ciaramella, Martina Marei Viti, Marco Landi, Kryštof Chytrý, Claudia Angiolini, Gianmaria Bonari.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ciaramella D, Viti MM, Landi M, Chytrý K, Angiolini C, Bonari G (2024) Vegetation diversity of Pinus pinaster forests in the Italian Peninsula. Vegetation Classification and Survey 5: 289-300. https://doi.org/10.3897/VCS.118023
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Aim: To revise Pinus pinaster-dominated communities of the Italian peninsula with special regard to central-southern Tuscany, and assess their floristic and ecological differences. Study area: Tuscany and Liguria regions, Italy. Methods: We classified 251 vegetation plots using the Two-way indicator species analysis method and we explored vegetation patterns through Principal Coordinate Analysis. We then investigated the ecology using Ecological Indicator Values. Results: We identified four major groups, primarily distinguished by the substrate of their stands and along a latitudinal gradient. We classified the forests in central-southern Tuscany in the association Erico scopariae-Pinetum pinastri. This community includes thermophilous and mesophilous species primarily distributed in the Atlantic and Western Mediterranean regions. Comparison of community means of Ecological Indicator Values revealed significant differences in soil reaction, nitrogen, moisture, and light conditions, but not in temperature, between the central-southern Tuscany forests and the other clusters. We classified the other studied forest communities on acidic substrates within the association Erico arboreae-Pinetum pinastri, whereas those found on ultramafic substrates were placed in the Euphorbio ligusticae-Pinetum pinastri typus cons. propos., and in an informal group of secondary vegetation stands. Conclusions: Our analyses showed that the Pinus pinaster-dominated forests of central-southern Tuscany belong to the association Erico scopariae-Pinetum pinastri of the alliance Genisto pilosae-Pinion pinastri (class Pinetea halepensis). The presence of species of phytogeographical importance in the forest understory, underscores the high biogeographic and conservation value of these pine forests.
Taxonomic reference:
Syntaxonomic reference:
Abbreviations: EVC = EuroVegChecklist; ICPN = International Code of Phytosociological Nomenclature; PCoA = Principal Coordinate Analysis; TWINSPAN = Two-way indicator species analysis.
Genisto pilosae-Pinion pinastri, Maritime pine, Pinetea halepensis, plant communities, vegetation classification
Mediterranean thermophilous pine forests are a common vegetation type throughout the Mediterranean Basin. These forests are dominated by one of the four Mediterranean thermophilous pines (Pinus brutia, P. halepensis, P. pinaster, and P. pinea). They typically occur in extreme climatic or soil conditions, such as on exposed, warm, and dry rocky slopes, on ultramafic bedrocks, marls, dolomites, and limestones (
Pinus pinaster s.l. (Maritime pine) is a medium-sized tree with a west-Mediterranean Atlantic range, distributed from the Mediterranean area of southwestern Europe to the Atlantic Iberian Peninsula, France, Italy, and northwestern Africa (
From a phytosociological standpoint, P. pinaster is an important diagnostic and dominant species of the order Pinetalia halepensis belonging to the class Pinetea halepensis, which includes all Mediterranean thermophilous pine forests. This class corresponds to the EUNIS habitat type “T3A Mediterranean lowland to submontane Pinus forest” and partly also to “N1G Mediterranean coniferous coastal dune forest” (
In Italy, P. pinaster forest communities have been studied since the 70s in terms of syntaxonomy (
Since the recent Mediterranean pine forest classification revision reconsidered the syntaxonomic scheme at the alliance level (
Overall, this paper aims to (i) revise P. pinaster-dominated communities of the Italian peninsula with special regard to central-southern Tuscany, and (ii) assess their floristic and ecological differences.
The sampling area is situated in central-southern Tuscany, south-west of the city of Siena, on the eastern side of the Colline Metallifere hilly-mountain complex, with elevations ranging from 100 to 800 m a.s.l. (Figure
The main vegetation types in the area include monospecific P. pinaster forests, from 8 to 20 m tall, with an understory of thermophilous evergreen shrubs and a sparse herbaceous layer. Other forests include deciduous oak forests dominated by Quercus cerris, Q. petraea, and Castanea sativa, and evergreen sclerophyllous forests with Quercus ilex. Carpinus betulus forests with relict stands of Fagus sylvatica and riparian woods with Alnus glutinosa and Osmunda regalis of the alliance Osmundo-Alnion glutinosae dominate the floors of the humid valleys (
We sampled 50 10 × 10 m original vegetation relevés subjectively placed all over the study area in May and June 2022, encompassing the major environmental local gradients (see Suppl. material
For those relevés from the CircumMed Forest Database recorded with the Braun-Blanquet methodology, the cover values of species were transformed into mid-percentage values of individual grades. In all the relevés, the cover values of the same species present in different layers were combined into a single layer, accounting for the possibility of multiple layers overlapping (
We performed TWINSPAN (
Then, to explore general patterns of forest communities and to highlight changes in species composition among groups, we ran a principal coordinate analysis (PCoA) of the dataset using the ‘vegan’ package (
Finally, to investigate the adaptive characteristics of the communities of the clusters, we investigated the life forms and chorotypes spectra by plotting bar charts.
The first TWINSPAN division separated two main pine forest communities, suggesting a distinction that was based on substrates. The TWINSPAN classification was cut at the second level of division, taking into account species composition, geographic distribution, type relevés, and information on their ecology gleaned from the literature (Figure
The same groups can also be distinguished in the ordination PCoA diagram (Figure
The distribution map of the plots is provided in Figure
We report an abbreviated synoptic table of diagnostic and constant species across clusters (Table
The analysis of Ecological Indicator Values helped to further characterise the ecology of each cluster (Figure
Analysis of life forms (Suppl. material
Dendrogram of a TWINSPAN classification based on the species composition of Pinus pinaster forest plots. The colours refer to: red - Cluster 1 (Eastern Liguria); green - Cluster 2 (Central-Southern Tuscany and marginally Western Liguria); light blue - Cluster 3 (Southern Tuscany); purple - Cluster 4 (Eastern and Western Liguria). The number of relevés for each cluster is specified in brackets.
PCoA results showing Pinus pinaster forest plots in relation to latitude and clusters (A) and associated species (B). The colours refer to: red - Cluster 1 (Eastern Liguria); green - Cluster 2 (Central-Southern Tuscany and marginally Western Liguria); light blue - Cluster 3 (Southern Tuscany); purple - Cluster 4 (Eastern and Western Liguria). Species showing a correlation coefficient >0.5 with the first two axes have been superimposed to the ordination diagram (B), and are shown with a (+).
Map showing the distribution of the clusters in relation to the study area. The colours refer to: red - Cluster 1 (Eastern Liguria); green - Cluster 2 (Central-Southern Tuscany and marginally Western Liguria); light blue - Cluster 3 (Southern Tuscany); purple - Cluster 4 (Eastern and Western Liguria). In the upper-right box, the distribution of Pinus pinaster in Italy is reported (
Abbreviated table of diagnostic and constant species of the clusters resulting from hierarchical cluster analysis (TWINSPAN). For each cluster, only species with a phi coefficient ≥0.45 and constant species with a percentage occurrence frequency >50% are shown. Species are sorted by decreasing phi coefficient for each cluster, but only the percentage frequency is shown. The frequency values >50% are indicated in grey shading. Cluster 1: Eastern Liguria; Cluster 2: Central-Southern Tuscany and marginally Western Liguria; Cluster 3: Southern Tuscany; Cluster 4: Eastern and Western Liguria. See Suppl. material
Species | Cluster 1 | Cluster 2 | Cluster 3 | Cluster 4 |
---|---|---|---|---|
(n = 83) | (n = 129) | (n = 17) | (n = 22) | |
Teucrium scorodonia | 70 | 3 | . | . |
Brachypodium rupestre | 67 | 9 | 24 | . |
Pteridium aquilinum | 86 | 41 | . | . |
Quercus ilex | 78 | 31 | 18 | . |
Castanea sativa | 69 | 22 | . | 9 |
Rubus ulmifolius | 73 | 30 | 24 | . |
Erica scoparia | 1 | 80 | 76 | . |
Calluna vulgaris | 4 | 70 | . | 14 |
Arbutus unedo | 48 | 88 | . | . |
Thymus striatus | . | . | 100 | . |
Plantago holosteum | . | . | 94 | . |
Convolvulus cantabrica | . | . | 88 | 5 |
Festuca robustifolia | . | . | 82 | . |
Genista januensis | 4 | 1 | 100 | . |
Koeleria splendens | . | . | 76 | . |
Galium corrudifolium | . | . | 71 | . |
Sanguisorba minor subsp. balearica | . | . | 65 | . |
Galatella linosyris | . | . | 59 | . |
Knautia arvensis | . | . | 59 | . |
Stipa etrusca | . | . | 53 | . |
Juniperus oxycedrus | 5 | 3 | 82 | . |
Centaurea aplolepa | 1 | . | 100 | 91 |
Bromopsis erecta | . | 2 | 94 | 86 |
Festuca ovina aggr. | 1 | . | 94 | 95 |
Potentilla hirta | . | . | 76 | 91 |
Brachypodium phoenicoides | . | . | . | 100 |
Plantago maritima subsp. serpentina | . | . | . | 91 |
Scabiosa pyrenaica | . | . | . | 91 |
Teucrium montanum | 1 | . | . | 91 |
Galium purpureum | . | . | . | 86 |
Euphorbia spinosa subsp. ligustica | 1 | 2 | . | 100 |
Satureja montana | 1 | 1 | . | 91 |
Asperula aristata | . | . | . | 82 |
Helictochloa pratensis | . | . | . | 82 |
Scorzonera austriaca | . | . | . | 82 |
Thymus serpyllum | . | . | . | 77 |
Trinia glauca | . | . | . | 77 |
Pilosella piloselloides | . | . | 6 | 77 |
Carex humilis | 2 | 2 | . | 86 |
Sorbus aria | . | 2 | . | 77 |
Peucedanum oreoselinum | . | 2 | . | 68 |
Peucedanum cervaria | 4 | 1 | . | 59 |
Lotus corniculatus | . | 2 | 6 | 55 |
Anthericum liliago | 1 | 11 | 6 | 64 |
Boxplots of unweighted community means of Ecological Indicator Values showing the results of the post-hoc Dunn’s multiple comparison test with Holm correction. The results of pairwise comparisons are indicated using Compact Letter Display method, where different letters between two clusters indicate a statistically significant difference of the test, with p <0.05. The colours refer to: red - Cluster 1 (Eastern Liguria); green - Cluster 2 (Central-Southern Tuscany and marginally Western Liguria); light blue - Cluster 3 (Southern Tuscany); purple - Cluster 4 (Eastern and Western Liguria).
The presented analytical comparison of Ligurian-Tuscan Pinus pinaster forests highlights the floristic-vegetational diversity of the investigated communities. These forests thrive in diverse edaphic conditions, occurring on both siliceous and ultramafic substrates, and are distributed along a broad climatic gradient encompassing Temperate and Mediterranean areas. Results indicate floristic and ecological similarity of the studied community in central-southern Tuscany to the association Erico scopariae-Pinetum pinastri described by
A significant difference in floristic composition exists between the forests under investigation and the association Erico arboreae-Pinetum pinastri of northern Tuscany. Both are characterised by a group of species serving as vicariants (e.g., Erica scoparia vs. E. arborea, Genista pilosa vs. G. germanica, Lonicera implexa vs. L. etrusca, Brachypodium retusum vs. B. rupestre, Rubus hirtus vs. R. ulmifolius). In the forests of central-southern Tuscany, the understory is richer in shrubs and chamaephytes, featuring a diverse array of narrow-leaved xerophytes. However, geophytes and therophytes are scarce, even though both vegetation types are species-poor. Since the forest canopy is relatively open, the presence of light-demanding taxa is common (e.g., Danthonia decumbens, Potentilla erecta, Serratula tinctoria, Tuberaria lignosa), which is consistent with findings in other Mediterranean pine forests (
Central-southern Tuscany forests stand out as they host a significant number of Stenomediterranean species, including a notable group with a Eurimediterranean distribution (e.g. Fraxinus ornus, Rubus ulmifolius, Sorbus domestica). Nevertheless, the percentage of European, Eurasian, and Boreal taxa (e.g., Calluna vulgaris, Danthonia decumbens, Molinia arundinacea, Potentilla erecta) suggests that there is a substantial influence from the Euro-Siberian region. In particular, the occurrence of Calluna vulgaris holds great phytogeographic interest as it marks the southern boundary of its distribution in Italy (
According to our analysis, the association Buxo sempervirentis-Pinetum pinastri seems to be floristically similar to the species composition of the association Erico arboreae-Pinetum pinastri. However, we preferred not to synonymize the two associations since the latter was described by
Our analysis confirms the floristic autonomy of forests found on ophiolitic substrates in the Liguria region. Along with the occurrence of shrubs like Juniperus communis, Amelanchier ovalis and Sorbus aria, and a xerophilous herbaceous layer featuring, e.g., Brachypodium phoenicoides, Bromopsis erecta, Festuca ovina aggr., and Teucrium montanum, several species characteristic of ophiolitic substrates are found, including Centaurea aplolepa, Euphorbia spinosa subsp. ligustica, Cherleria laricifolia subsp. ophiolitica, Plantago maritima subsp. serpentina and Thymus serpyllum.
Our classification includes an informal group comprising of pine forest plantations established on ultramafic bedrock in southern Tuscany (
From a habitat perspective, the studied pine forest communities were not included in Annex I of the 92/43/EEC Habitats Directive. On the one hand, this exclusion is due to the extensive use of P. pinaster for past reforestation in the surrounding areas, making it difficult to distinguish native sites from artificially established ones. On the other hand, old-established plantations of native pine species can develop an understory of natural species composition that makes these forest communities valuable in terms of nature conservation (
Our study has expanded the floristic and ecological knowledge of Pinus pinaster forests at the southeasternmost margin of their European mainland distribution range and has contributed to their classification by proposing an updated syntaxonomic scheme. We extended the occurrence of the alliance Genisto pilosae-Pinion pinastri (class Pinetea halepensis) to central-southern Tuscany, beyond the Ligurian-Provençal seaboard. Based on ecological characteristics, diagnostic species, type relevés, and information gleaned from existing literature, we confirmed the associations Erico arboreae-Pinetum pinastri and Erico scopariae-Pinetum pinastri, distributed from eastern Liguria to southern Tuscany on siliceous soil conditions. Importantly, we identified a syntaxonomic placement for the forests of central-southern Tuscany, which previously lacked classification at the association level, attributing them to the association Erico scopariae-Pinetum pinastri. Additionally, we identified two communities on ultramafic substrate: one confined to central Liguria, proposed in our study as association Euphorbio ligusticae-Pinetum pinastri, for which we suggest conserving the association name, and another one found in central Tuscany and consisting of introduced plantations. The results of this study underscore the importance of conserving the central-southern Tuscany P. pinaster forests, not only because the dominant pine species is situated at the southeasternmost boundary of its distribution on the Italian peninsula, but also due to the presence of species with phytogeographical significance in the forest understory.
Class PINETEA HALEPENSIS Bonari et Chytrý in
Order Pinetalia halepensis Biondi, Blasi, Galdenzi, Pesaresi et Vagge in Biondi et al. 2014
Alliance Genisto pilosae-Pinion pinastri Biondi et Vagge 2015
Association Erico arboreae-Pinetum pinastri Biondi et Vagge 2015 [Cluster 1]
Association Erico scopariae-Pinetum pinastri Biondi et Vagge 2015 [Cluster 2]
Pinus pinaster secondary plantations on serpentine of southern Tuscany (informal group) [Cluster 3]
Association Euphorbio ligusticae-Pinetum pinastri Hofmann ex
Association ? Buxo sempervirentis-Pinetum pinastri Biondi et Vagge 2015
The question mark “?” refers to the doubtful syntaxonomic status of this vegetation unit.
Relevés of this article are available upon request through the CircumMed Forest Database (Global Index of Vegetation-Plot Databases, ID: EU-00026).
G.B. planned the research; D.C. and M.M.V. conducted the field sampling with support of M.L.; D.C., M.M.V., M.L., and G.B. identified plant specimens; M.M.V. and K.C. performed the statistical analyses; D.C. and M.M.V. led the writing and review with major contributions of G.B. All authors critically revised the manuscript and approved the final and revised version.
We are grateful to Federico Fernández-González for his nomenclatural advice. We thank the Corpo Forestale Carabinieri of Siena for the logistic support during fieldwork. We are also grateful to Tiberio Fiaschi for assisting us in finding relevant literature. G. Bonari and C. Angiolini were funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.4 - Call for tender No. 3138 of 16 December 2021, rectified by Decree n. 3175 of 18 December 2021 of Italian Ministry of University and Research funded by the European Union – NextGenerationEU; Award Number: Project code CN_00000033, Concession Decree No. 1034 of 17 June 2022 adopted by the Italian Ministry of University and Research, CUP B63C22000650007, Project title “National Biodiversity Future Center - NBFC”.
Distribution of the relevés, life form and chorotype spectra of individual clusters (.docx file)
Synoptic table with percentage frequency and phi coefficient for each species in the clusters (.docx file)