Mismatching streetscapes: Woody plant composition across a Neotropical city

Abstract

With the establishment and expansion of urban areas, many plants are lost, while some are gained. Understanding plant species richness and composition in cities, including planted elements along streetscapes, is a priority for urban vegetation management and biodiversity conservation. In this study, we assessed the compositional dissimilarity of street trees and shrubs (namely woody vegetation) in the Neotropical city of Xalapa (Mexico) through a citywide sampling scheme. We also evaluated potential relationships between woody vegetation compositional dissimilarity among survey sites considering the distance between them (which is the inverse equivalent of distance decay in studies focused on similarity). For this, we calculated pairwise compositional values using the partitioned Sorensen dissimilarity index (βsor), which allows accounting for the turnover (βsim) and nestedness (βsne) components of the observed dissimilarities. To assess potential distance increases in dissimilarity, we used generalized linear models. Results from our citywide survey show that βsor values were high, indicating that planted woody species composition on streetscapes was heterogeneous and mainly driven by species turnover. Additionally, woody vegetation composition showed a weak increase in dissimilarity with increasing distances between survey sites. Altogether, our findings show that the dissimilarity of woody vegetation along the streetscapes of Xalapa does not follow any particular spatial pattern, which is not in agreement with previous evidence reported in the literature. These findings reflect the impact and role that citizens and local authorities play on the configuration of the street tree and shrub species composition by species selection, planting, and care.