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3. Doktoritööd

Selle kollektsiooni püsiv URIhttp://hdl.handle.net/10492/2490

Sirvi

Sirvi 3. Doktoritööd Autor "Alos Orti, Marta" järgi

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    Kirje
    Urban ecology : novel ecosystems, novel challenges
    (Estonian University of Life Sciences, 2022) Alos Orti, Marta; Laanisto, Lauri (advisor); Institute of Agricultural and Environmental Sciences; Cortinovis, Chiara (opponent); Helm, Aveliina (pre-opponent)
    The present thesis is the result of four years of PhD studies where various taxonomic groups were explored in terms of taxonomic and functional diversity in urban ecosystems at a broad scale. My research was conducted within the framework of BioVeins, a European research project aimed at studying urban biodiversity of several taxa and ecosystem functions and services in European urban areas. Three out of four European residents currently live in cities, and projections foresee a further increase of city dwellers in the upcoming years (UN, 2019). Urban areas are a patchwork of different land use and land cover types where surfaces unsuitable for most species (e.g. industrial and residential areas) occur simultaneously with green areas (e.g. parks, cemeteries ) varying in size and isolation from other similar areas (Faeth et al., 2012). Urbanization process comes along with land use change, habitat fragmentation and other stressors that compromise biodiversity creating novel ecosystems with new species assembl ages (Gaston, 2010 ; Swan et al., 2011). Therefore, functional diversity, providing the multifaceted ecosystem services and benefits in urban communities depends on biotic and abiotic factors acting as filters of the preexistent traits Spasojevic et al., 2018), and those arriving by natural processes such as dispersal. Novel urban communities composition are guided by processes such as stochasticity, facilitation, competition or adaptation (Kondratyeva et al., 2020). which species assemble The mechanisms by in urban ecosystems may differ from those in natural and semi ecosystems (Masonnatural rural et al., 2011), and are still not fully understood, mainly due to more factors acting in urban community composition compared to rural environments (e.g. social p references, economic constraints, urban heat island effect). Urban green spaces (UGSs) are often seen as potential biodiversity hotspots compared to the surrounding area, as they constitute habitat for native and nonnative species, and provide food and s helter for migrating wildlife (University of California, 2014; Derbi Lewis et al., 2016 ), creating ecological oases in the middle of the impervious surfaces and built structures of the urban fabric. Therefore, while urbanization and urban expansion pose a major threat for biodiversity outside cities, UGSs increase habitat heterogeneity and create new opportunities for maintaining and increasing biodiversity. However, which factors and how they influence urban taxonomic and trait diversity, species compositi on and distribution is not fully understood in urban ecology. In this thesis we firstly propose a research agenda where we discuss five potential research directions aimed at improving our understanding of the links between biodiversity, ecosystem functions and services (BEF/ES) in urban areas. Then, we explore the taxonomic and functional diversity of vegetation, lichens and wild bee species and how they respond to main urban abiotic factors (e.g. landscape metrics, air pollution) and availability of food resources. We selected a wide range of UGSs from seven cities across a NESW gradient of mainland Europe, namely: Tartu (Estonia), Poznan (Poland), Antwerp (Belgium), Paris (France), Zurich (Switzerland), Lisbon and Almada (Portugal). In each city, we selected sites based on the land cover class 1.4.1. Green Urban Areas included in the panEuropean Urban Atlas (EEA, 2012). We used random stratified 2 sampling for the selection of sites. We included the UGS size (area in m connectivity ) and calculated its with other similar elements of the urban fabric by using the Proximity Index (PI) within a 5km radius from the focal UGS. Then we created a matrix formed by two orthogonal gradients comprising the size and the resulting connectivity both classified into 6 classes and distributed the UGSs along the matrix, resulting in a maximum of 36 possible combinations of UGS size and connectivity in each studied city. We sampled taxonomic and functional diversity of woody vegetation, lichens and floral resources us ed by wild bee species using a standardized sampling design framework, thus getting comparable data from the same UGSs across the continental gradient. BioVeins research agenda identified five main research directions, namely: i) use a trait in order to improve our understanding of B-- based approac h EF/ES relationships; ii) improve urban habitat mapping; iii) use citizen science to involve city dwellers in BEF/ES research; iv) consider multiple environmental gradients; and v) include neglected urban habita ecology research. ts and ecological niches in urban In the course of fieldwork (from 2018 to 2020) we identified 418 woody species in 225 UGSs, 140 lichen species in 219 UGSs both across 7 cities, and pollen from 135 plant species as part of the larval bee diet in 80 sites from 5 cities. Regarding urban vegetation, we found high proportions of nonnative woody species in all the sampled cities (i.e. from 40 to 65% of the total species pool). Species richness, vegetative aboveground biomass (AGB) and canopy cover (m UGS size, while species density steeply decreased along the size gradient. 2 ) were positively related to Urban vegetation, particularly herb and tree species, represent an important food source for wild bees and their larvae in cities. Urban bee species displayed different successful feeding strategies. Specialist bee species showed more consistent diets across cities (i.e. less variation in the diet along the latitudinal gradient) compared to more polylectic (generalist) bees. Diet composition in terms of taxonomic and preferred plant traits varied with the specialization degree. Most generalist species showed a more diverse and variable diet, with a higher proportion of exotic plant species compared to more oligolectic (specialist) bee species. The probability of occurrence of medium and high specialized bees decreased with increasing urban intensity. Regarding lichen biodiversity, Lisbon, Antwerp and Tartu showed higher diversity and abundance compared to the other cities. Cities also present ed dissimilarities in terms of functional structure of isplayed a medium or medium lichen communities, with some exceptions. For instance, solar radiation tolerance was high across all the cities (accounting for >75% of the total lichen abundance). In general, more abundant lichens dhigh tolerance to arid conditions. Broad scale environmental drivers (air pollution and climate) explained ~15% of the total variation in taxonomic and trait for urban lichens. The remaining variance (~85%) is exrelated metrics plained by local factors (e.g. distance to the pollution source, management practices, etc.). Within the broad scale drivers, air pollution accounted for most of the variability on that scale (10.4%). However, climate was the driver of lichen functional diversity at the broad scale, although it only explained 7.1% of the broad scale variance. While biodiversity loss is occurring at an unprecedented rate (Leclère et al., 2020), and urbanization increasing globally (UN, 2019), it becomes necessary to integrate biodiversity conservation strategies into urban planning. For this, we need to understand B order to promote multifunctional urban ecosystems.EF/ES relationships at multitaxa level in UGSs are commonly vegetatively diverse environments with heterogen eity of habitats that provide a variety of food and shelter for urban taxa, such as wild bees and lichens. This high species richness is due to the big proportion of nonnative mental purposes) species that are commonly guided by local socio rather than by natural processes (e.g. dispersal). economic preferences (e.g. orna Plant selection and, therefore, species composition have an influence on several urban taxa. For instance, non native plant species turned to be an important component of the larval bee herbaceous and tree species were the preferred plant growth forms diet, and with different levels of diet conservatism across cities at the plant family and genus levels. Our results suggest that while municipalities tend to promote woody species richness, especially in bigger parks, they do so up to a certain threshold, that is city-- dependent. Therefore, local anthropogenic factors play an important role in designing urban biodiversity (e.g. Matos et al., 2019; Munzi et al., 2007) and ecosystem services. However, broad scale drivers also need to be considered since they account for an important proportion in taxonomic and functional diversity of several taxonomic groups (e.g. lichens). Woody species density, lichen diversity and larval bee diet composition revealed good indicators of how decisionmakers integrate biodiversity in urban planning and management. Comparable multi patterns and the taxa and multi relationshipcity studies provide a holistic understanding of urban biodiversity with ecosystem functioning and services. The presented taxonomic and functional diversity of urban green spaces at the contine ntal scale can support the planning and management of urban ecosystems to promote biodiversity and ESs (e.g. pollination, air quality improvement) and, therefore, increase cities resilience and livability for both humans and nature.