Woody plant functional traits and phylogenetic signals correlate with urbanization in remnant forest patches

Abstract

Exploring the alterations in functional traits of urban remnant vegetation offers a more comprehensive perspective on plant assembly within the context of urbanization. While plant functional traits are influenced by both environmental gradients and the evolutionary history of plant species, the specific mechanisms by which urbanization mediates the combination of functional traits and the evolutionary history of remnant vegetation remain unclear. To examine the relationship between functional traits and phylogenies of remnant vegetation and urbanization, we classified the woody plant species surveyed in 72 sample plots in nine remnant forest patches in Guiyang, China, into four groups (urban, rural, middle and general groups) according to their location under different levels of urbanization and measured nine functional traits of these species. The phylogenetic signals of each functional trait of the four species groups were then quantified based on Blomberg's K. Furthermore, we analysed the correlations between functional traits and species abundance using phylogenetic generalized least squares. The results showed that significant phylogenetic signals were detected in more functional traits of the urban group than other groups. Thirteen and three significant relationships between functional traits and species abundance were detected for tree and shrub species after removing phylogenies. Tall tree species were more abundant in the urban group, while the general group favoured the species with adaptable traits (low height and high leaf area and C/N). Overall, we demonstrate that urbanization drove shifts in plant functional traits in remnant forests after combining the phylogenetic patterns.

Keywords: functional traits; phylogenetic signals; species group; urban remnant forests; urbanization; woody plants.

FIGURE 1

Impervious surfaces within 500 m of the remnant patches. The colour white denotes land cover types other than impervious surfaces.

FIGURE 2

Study area and spatial locations of sample patches with different levels of urbanization.

FIGURE 3

Diagram of categories of species groups. The left, right and bottom circles represent the species that occurred in the remnant patches under high, medium and low levels of urbanization, respectively. A represents the species that only occurred in the patches under high urbanization; B represents the species that only occurred in the patches under medium urbanization; C represents the species that only occurred in the patches under low urbanization; D represents the species that both occurred in the patches under high and medium urbanization; E represents the species that both occurred in the patches under high and low urbanization; F represents the species that both occurred in the patches under medium and low urbanization; G represents the species that simultaneously occurred in the patches under three levels of urbanization.

FIGURE 4

Functional traits of woody plants in different groups. The bar is the mean value, and the arrow is the standard error (95% confidence level).

FIGURE 5

Significant relationship (p < .01) between functional traits and species abundance for tree species based on generalized least squares (purple lines) and phylogenetic generalized least squares (blue lines). Circles represent scatter plots showing the relationship between predictor and response variables.

FIGURE 6

Significant relationship (p < .01) between functional traits and species abundance for shrub species based on generalized least squares (purple lines) and phylogenetic generalized least squares (blue lines). Circles represent scatter plots showing the relationship between predictor and response variables.