This PhD thesis focuses on alien plant invasions in mountain ecosystem and in alien and native forests in hilly urban/rural landscape under the influence of human disturbance and land use change. These factors facilitate the spread of alien species, threatening biodiversity and ecosystem function, especially in Mediterranean regions. The research had three main objectives: 1. To explore the distribution and ecological characteristics of alien plant species along elevation gradients and mountain roads in the Central Apennines (Italy); 2. To assess the role of native plant community resistance and land-use changes in shaping alien species invasions in Central Apennines; 3. To analyse the distribution pattern, the ecological features and the woody species richness of alien and native forests in a small Mediterranean city. Vegetation data were collected in 60 plots, stratified by elevation along three mountain roads (Gran Sasso, Maiella and Terminillo mountains) following the road survey protocol of the Mountain Invasion Research Network (MIREN). Climate and land-use changes were quantified using current and historical climatic data alongside the analysis of aerial imagery spanning from the 1950s to the present. In the functional urban area of Campobasso, according to the survey protocol of the National Biodiversity Future Centre (NBFC, spoke 5), a random sampling stratified by forest categories based on the Carta della Natura of the municipality of Campobasso and the gradient of cover and fragmentation of green areas was applied. The woody species richness, the community-weight mean of moisture and nitrogen ecological indicators, and soil disturbance indicators were analysed. Statistical analyses were performed in the R Studio environment, utilizing tools such as random forests, box plots, and structural equation modelling. Key findings, concerning MIREN data, show that alien plant species are more abundant near roads and disturbed habitats, particularly in areas with warmer and lighter conditions. Thermophilous alien plant species were prevalent at lower elevations, with some extending to higher altitudes, suggesting a potential upward shift due to climate change. Roads and disturbed areas significantly contribute to the presence of alien species, especially in regions with high soil disturbance and moderate grazing pressure. Alien species cover was especially high in nitrogen-rich environments commonly found in disturbed sites. These findings emphasize how human-made infrastructures, such as roads, act as pathways for alien species, facilitating their spread in mountain landscapes, although the altitudinal gradient remains a constraining factor. The research also indicates that native plant communities dominated by taller native species with larger seeds are more resistant to invasion by alien species. This is particularly evident in areas where agricultural abandonment led to the establishment of short-statured native communities, which have lower resistance to invasion, while areas with forest expansion show increased resistance to alien invasion. In hilly urban environments, both native oak forests and non-native Robinia pseudoacacia-dominated woods contribute to woody species richness. However, R. pseudoacacia is invasive and harmful in disturbed sites along riverbanks, where it competes with native riparian forests dominated by Salix alba and Populus alba. This highlights the need for targeted management to control invasive species in hilly urban areas. The study emphasizes the importance of protecting and maintaining healthy native plant communities to prevent invasions by alien species. Activities such as managing roadsides, removing native vegetation, and creating bare ground through soil disturbance contribute to the establishment of alien species. The research also highlights the importance of long-term ecological monitoring to track alien plant invasions and vulnerable habitats, contributing to effective management strategies such as early detection and rapid response to contain the spread of invasive species.
La tesi di dottorato esamina le invasioni di piante aliene negli ecosistemi montani e nelle foreste di specie native e aliene in paesaggi collinari, urbani e rurali, sotto l'influenza delle attività umane e delle trasformazioni del paesaggio. Tali fattori facilitano la diffusione delle specie aliene, minacciando la biodiversità e il funzionamento degli ecosistemi, in particolare nelle regioni mediterranee. La ricerca si è posta tre obiettivi principali: 1. Esplorare la distribuzione e le caratteristiche ecologiche delle specie vegetali aliene lungo i gradienti altitudinali e le strade montane dell’Appennino centrale (Italia); 2. Valutare il ruolo della resistenza delle comunità vegetali native e dei cambiamenti d'uso del suolo nel determinare le invasioni di specie aliene in Appennino centrale; 3. Analizzare i pattern di distribuzione, le caratteristiche ecologiche e la ricchezza di specie legnose delle foreste aliene e native in una piccola-media città mediterranea. I dati vegetazionali sono stati raccolti in 60 plot, stratificati per altitudine lungo tre strade montane (Gran Sasso, Maiella e Terminillo), seguendo il protocollo di indagine del Mountain Invasion Research Network (MIREN). I cambiamenti climatici e d'uso del suolo sono stati quantificati attraverso l'analisi di dati climatici attuali e storici, insieme all'analisi di immagini aeree che coprono il periodo dal 1950 fino ai giorni nostri. Seguendo il protocollo di indagine del National Biodiversity Future Centre (NBFC, spoke 5), nell'area urbana di Campobasso è stato applicato un campionamento casuale stratificato per categorie forestali, basato sulla Carta della Natura del Comune e sul gradiente di copertura e frammentazione delle aree verdi. Sono stati analizzati la ricchezza di specie legnose, la media ponderata degli indicatori ecologici di umidità e azoto, nonché gli indicatori di disturbo del suolo. Le analisi statistiche sono state condotte in R Studio, utilizzando tecniche come random forest, box plot e structural equation modelling. I principali risultati derivanti dall'analisi dei dati MIREN mostrano che le specie di piante aliene sono significativamente più abbondanti ai bordi delle strade e in habitat disturbati, con una prevalenza nelle aree caratterizzate da condizioni termofile ed eliofile. Le specie aliene termofile sono risultate prevalenti a bassa altitudine, con alcune che raggiungono anche quote più elevate, suggerendo un possibile spostamento altitudinale dovuto ai cambiamenti climatici. Le strade e le aree disturbate contribuiscono in modo rilevante alla presenza di specie aliene, in particolare nelle regioni con elevato disturbo del suolo e moderata pressione di pascolo. Gli ambienti ricchi di azoto, tipici dei siti disturbati, presentano una maggiore copertura di specie aliene. Questi risultati evidenziano come le infrastrutture antropiche, in particolare le strade, agiscano come vie di diffusione per le specie aliene, favorendone la propagazione nei paesaggi montani, sebbene il gradiente altitudinale continui a rappresentare un fattore limitante. La ricerca suggerisce, inoltre, che le comunità di piante native, dominate da specie più alte e con semi di dimensioni superiori, mostrano una resistenza superiore all'invasione da parte delle specie aliene. Questo fenomeno è particolarmente evidente nelle aree dove l'abbandono agricolo ha portato alla formazione di comunità native di statura ridotta, caratterizzate da una minore resistenza all'invasione, mentre le aree con espansione forestale mostrano un aumento della resistenza all'invasione da parte delle specie aliene. Nell'ambito degli ambienti urbani collinari, sia le foreste di querce native che le foreste dominate da Robinia pseudoacacia (non native) contribuiscono alla ricchezza di specie legnose. Tuttavia, R. pseudoacacia è una specie invasiva particolarmente problematica nei siti disturbati lungo le rive dei fiumi, dove compete con le foreste ripariali native dominate da Salix alba e Populus alba. Questo evidenzia la necessità di adottare misure di gestione mirate per controllare le specie invasive nelle aree urbane collinari. Lo studio sottolinea l'importanza di proteggere e mantenere le comunità vegetali native sane al fine di prevenire le invasioni da parte delle specie aliene. Le attività di gestione, come la manutenzione delle strade, la rimozione della vegetazione nativa e la creazione di terreni nudi attraverso il disturbo del suolo, contribuiscono all'insediamento delle specie aliene. Inoltre, la ricerca evidenzia l'importanza di un monitoraggio ecologico a lungo termine per tracciare le invasioni di specie aliene e monitorare gli habitat vulnerabili, al fine di sviluppare strategie di gestione efficaci, come la rilevazione precoce e la risposta rapida per contenere la diffusione delle specie invasive.
Alien plant species distribution and diversity in hilly and mountain habitats in central Italy
SANTOIANNI, Lucia Antonietta
2025
Abstract
This PhD thesis focuses on alien plant invasions in mountain ecosystem and in alien and native forests in hilly urban/rural landscape under the influence of human disturbance and land use change. These factors facilitate the spread of alien species, threatening biodiversity and ecosystem function, especially in Mediterranean regions. The research had three main objectives: 1. To explore the distribution and ecological characteristics of alien plant species along elevation gradients and mountain roads in the Central Apennines (Italy); 2. To assess the role of native plant community resistance and land-use changes in shaping alien species invasions in Central Apennines; 3. To analyse the distribution pattern, the ecological features and the woody species richness of alien and native forests in a small Mediterranean city. Vegetation data were collected in 60 plots, stratified by elevation along three mountain roads (Gran Sasso, Maiella and Terminillo mountains) following the road survey protocol of the Mountain Invasion Research Network (MIREN). Climate and land-use changes were quantified using current and historical climatic data alongside the analysis of aerial imagery spanning from the 1950s to the present. In the functional urban area of Campobasso, according to the survey protocol of the National Biodiversity Future Centre (NBFC, spoke 5), a random sampling stratified by forest categories based on the Carta della Natura of the municipality of Campobasso and the gradient of cover and fragmentation of green areas was applied. The woody species richness, the community-weight mean of moisture and nitrogen ecological indicators, and soil disturbance indicators were analysed. Statistical analyses were performed in the R Studio environment, utilizing tools such as random forests, box plots, and structural equation modelling. Key findings, concerning MIREN data, show that alien plant species are more abundant near roads and disturbed habitats, particularly in areas with warmer and lighter conditions. Thermophilous alien plant species were prevalent at lower elevations, with some extending to higher altitudes, suggesting a potential upward shift due to climate change. Roads and disturbed areas significantly contribute to the presence of alien species, especially in regions with high soil disturbance and moderate grazing pressure. Alien species cover was especially high in nitrogen-rich environments commonly found in disturbed sites. These findings emphasize how human-made infrastructures, such as roads, act as pathways for alien species, facilitating their spread in mountain landscapes, although the altitudinal gradient remains a constraining factor. The research also indicates that native plant communities dominated by taller native species with larger seeds are more resistant to invasion by alien species. This is particularly evident in areas where agricultural abandonment led to the establishment of short-statured native communities, which have lower resistance to invasion, while areas with forest expansion show increased resistance to alien invasion. In hilly urban environments, both native oak forests and non-native Robinia pseudoacacia-dominated woods contribute to woody species richness. However, R. pseudoacacia is invasive and harmful in disturbed sites along riverbanks, where it competes with native riparian forests dominated by Salix alba and Populus alba. This highlights the need for targeted management to control invasive species in hilly urban areas. The study emphasizes the importance of protecting and maintaining healthy native plant communities to prevent invasions by alien species. Activities such as managing roadsides, removing native vegetation, and creating bare ground through soil disturbance contribute to the establishment of alien species. The research also highlights the importance of long-term ecological monitoring to track alien plant invasions and vulnerable habitats, contributing to effective management strategies such as early detection and rapid response to contain the spread of invasive species.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/217642
URN:NBN:IT:UNIMOL-217642