Socio-economic differences control species composition of urban gardens in a metropolitan area of Argentina

Human population is becoming increasingly urbanized, and in this context, private gardens (home gardens) constitute an important component of urban biodiversity and provide access to ecosystem services. This study aims at identifying spatial patterns to understand the socio-ecological processes that influence the urban landscape. In our study, we analyze private gardens in one of the main urban agglomerations of Argentina to understand whether socio-economic structure or spatial distribution is more strongly influencing the species composition of private gardens. We selected 50 gardens from the urban area of Gran San Miguel de Tucumán. We surveyed the sociodemographic characteristics of garden owners and we performed vegetation censuses in each of the gardens. In the survey, we also evaluated the main mechanisms of plant acquisition. We used the species composition of each garden to perform a non-metric multidimensional scaling, which reflected the botanical distance between gardens. We used Mantel tests to correlate these botanical distances with the geographic and socio-economic distances between gardens to determine which variable controls the ecological attributes of the garden. To spatially characterize the socio-economic level, we used data from the national population census. The species composition of the gardens is more strongly associated with socioeconomic conditions than with geographical distance. The exchange of species is the main method of obtaining plants. Our study permits understanding how socio-economic structure influences the construction of private gardens, which are important components of the landscape and urban ecology. Our results could be explained by the willingness to belong to certain socio-economic groups but also by the interchange of propagules, which may reinforce social ties. Our results highlight the importance of addressing social issues to understand private decisions and design strategies toward a fair distribution of urban vegetation services.