Projet de Thèse « Plantes invasives et biodiversité des sols en milieux urbains »
Objectif :
Concours 2024 de l’Ecole doctorale ED60 (Université Paul-Valéry Montpellier 3)
https://www.univ-montp3.fr/fr/formation/financements/contrats-doctoraux-ed60
Laboratoire d’accueil :
Centre d’Ecologie Fonctionnelle et Evolutive (CEFE)
Direction :
Pr. Jérôme Cortet. (https://orcid.org/0000-0002-7410-8626)
Co-tutelle ou co-direction possible avec l’Université Federico II Naples.
Contacts : Jerome.cortet@univ-montp3.fr et lucia.santorufo@unina.it
Abstract
Invasive plants are amongst the main causes of biodiversity threats, as they have worldwide compromised native diversity by decreasing the abundance (by 43.5%), diversity (by 50.7%), and fitness (by 41.7%) of resident plant species (Vila et al., 2010). The alteration of the native plant community has cascading effects on ecosystem functioning because makes the recipient habitats more vulnerable to perturbations.
Europe, as a center for international trade for many centuries, has seen the establishment of many invasive species, particularly in environments with a high population density. In fact, the number of non-native plant species is greatest in human-made habitats (e.g. urban and industrial areas), where non-native species are first introduced for ornamental purposes (Gaertner et al., 2017). Accordingly, urban environments are hotspots for biological invasions. Amount of impervious surfaces, distance to city center, human population size, affluence, and density are among the factors associated with the success of invasive species in urban areas (Gaertner et al., 2017).
In Europe, urban areas host almost three quarters of the population, therefore the furniture of ecosystem services to inhabitants is challenging and represents the target of several political actions. The control of air and soil pollution caused by transportation and heating of buildings, the regulation of local temperature and hydric fluxes, the attenuation of noise and the furniture of semi-natural recreative spaces are among the main needs for ecosystem services in cities. Urban vegetation provides such benefits that can enhance the well-being of urban residents by contrasting the so-called nature deficit disorder (Driessnack, 2009) Although biodiversity is usually considered to play a critical role in ecosystem services furniture, urban communities are often poor in biodiversity and biotically homogeneous environments (Madre et al., 2014). In this context, invasive plants might provide substantial services in areas where the native plant community experience scarce performances. Previous studies performed in South Africa, USA, Canada and New Zealand highlighted the benefits provided by invasive plants in urban areas (Vaz et al., 2017; Prabakaran et al., 2019; Potgieter et al., 2019). In Europe, invasive plants have long been seen as a threat for the environment as they cause serious negative consequences for native biodiversity. However, the effects of invasive plants are ecosystem-dependent. In highly anthropized ecosystems, not able to support a high number of native species, invasive species may sustain ecosystem services rather than disrupt them.
In degraded environments, such as brownfields, polluted or abandoned soils, invasive species could be useful to restore contaminated soils (Prabakaran et al., 2019), to prevent erosion control (Forseth and Innis, 2004), or to increase soil moisture (Hartemink, 1999). However, invasive plants can modify the organism community of the urban environment. It has been demonstrated that novel interactions between non-native plants and resident pollinators can lead to facilitation of pollinator visitation to native plants (Bartomeus et al., 2008; Bjerknes et al., 2007). This may also affect pollinator population dynamics and community composition, which in turn could indirectly impact pollinator foraging to native plants. Apart from the interactions between invasive plants and above-ground communities, invasive plants affect the quantity and quality of root exudates to the soil, alter rates of nutrient cycling, and change inputs of organic matter to the soil (Bell et al., 2020). Changes in the chemical and physical properties of soil, as well as in litter and exudate inputs, are almost certain to impact microbial community assembly processes and community composition, which in turn, will alter ecosystem services (Bell et al., 2020). The changes in microbial communities, can have cascading effects on soil fauna. Soil microarthropods, in fact, have been shown to be impacted by plant invasion (Rusterholz et al., 2014; St. John et al., 2006).
The impacts of plant invasion on urban biodiversity are not well understood and particularly in relation to the potential synergistic impacts of invasion interacting with urbanization. In fact, the impacts of invasive plants are often evaluated in forest or agricultural ecosystems, only rarely in urban habitats.
The challenge is to make a city permeable to species introduction and dispersion, limiting negative impacts for environments and citizens. Despite the importance of the issue, the current knowledge is somewhat scarce and fragmented in European conurbations.
The Ph.D. will be organised into 2 closely related parts:
• Urban systems are characterised by the presence of numerous exotic plant species, introduced accidentally or deliberately. In some places (particularly on certain wasteland sites, but also in some gardens), these species can become invasive, even invasive, and contribute to a reduction in local plant biodiversity. However, little is known about the effects on soil fauna. This vegetation brings organic matter to the soil and helps to supply the soil with nutrients. It also modifies the physical conditions of the soil, for example by reducing the ground temperature. In addition, several invasive species of springtails have been observed in urban environments, and it will be necessary to analyse the reasons for these occurrences, in particular the correlations between the presence of these species and the vegetation present or the origin of the soil in place.
• The data acquired will be integrated with that collected as part of various national (BISES, PRODIJ) and international (COST Eudaphobase) projects, in order to assess the effects of urbanisation on soil fauna, particularly springtails. The aim of the Ph.D. will be to exploit the available data and combine it with available environmental data (soil analyses, landscapes), in order to be able to propose distribution patterns for taxonomic and functional communities of springtails in urban systems.
References
Bartomeus, I., Vila, M., Santamaria, L. 2008. Contrasting effects of invasive plants in plant-pollinator networks. Oecologia 155, 761–770.
Bell, J.K., Siciliano, S.D., Lamb, E.G. 2020. A survey of invasive plants on grassland soil microbial communities and ecosystem services. Scientific Data 7, 86.
Bjerknes, A.L., Totland, O., Hegland, S.J., Nielsen, A. 2007. Do alien plant invasions really affect pollination success in native plant species? Biol Conserv 138, 1–12.
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Potgieter, L.J., Gaertner, M., O’Farrell, P.J., Richardson, D.M. 2019. A fine-scale assessment of the ecosystem service-disservice dichotomy in the context of urban ecosystems affected by alien plant invasions. Forest Ecosystems 6, 46.
Prabakaran, K., Li, J., Anandkumar, A., Leng, Z., Zou, C.B., Du, D. 2019. Managing environmental contamination through phytoremediation by invasive plants: A review. Ecological Engineering 138, 28–37.
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