Non-Native Woody Plant Species Show Different Leaf Functional Traits and Herbivory Levels From Native Ones in the Urban Areas of Beijing, China

Abstract

A large number of non-native species have been introduced to urban ecosystems, and it is a distinctive feature of the urbanization process. However, it is unclear whether these non-native species have similar functional traits to native ones and are similarly integrated into the local food web. We evaluated the differences in leaf functional traits and herbivory between native and non-native species of common woody plants in 50 parks in Beijing, China. The nutrient contents, defensive traits, and levels of herbivory were measured in 2681 leaves across 138 (52 native and 86 non-native species) woody plant species. Results show that compared to native species, non-native trees showed greater potential for short-term carbon sequestration, lower nutrient contents, and chemical defense but similar levels of herbivory. Non-native shrubs had lower carbon contents and herbivory levels than native shrubs. Phylogenetic history explained much more of the variance in plant traits and herbivory than spatial variation, suggesting the high homogeneity of environments among different urban parks. Furthermore, the variation in leaf traits and herbivory of non-native species had higher uncertainty than that of native species. Our research findings indicate that compared to native species in urban ecosystems, non-native species have reduced plant-herbivore energy flow to primary consumers, which may hinder biodiversity at higher nutrient levels. In the future, urban parks should incorporate more native plant species and enhance environmental heterogeneity.

Keywords: herbivory; leaf functional traits; non‐native plants; phylogenetic history; urban ecology; urbanization.

FIGURE 1

The study area and sampled parks. Eeach point represents a sampled urban park (n = 50).

FIGURE 2

(A) The phylogenetic tree of the native and non‐native species used in this study. (B) Coefficient of variation of leaf functional traits and herbivory.

FIGURE 3

Comparison of leaf functional traits and Herbivory of native and non‐native plants (mean values and 95% CIs). The significance levels were indicated by asterisks (***, p < 0.001, **, p < 0.01, *, p < 0.05). The asterisks above the horizontal lines indicate significant differences in life form. The asterisks below the horizontal lines indicate significant differences in types within the same life form. The asterisks on the left indicate significant differences between native and non‐native species.

FIGURE 4

The contribution of phylogenetic history and spatial variation on the variances in leaf traits and herbivory between native and non‐native species.

FIGURE 5

Correlation between the contribution of different factors (phylogenetical history and spatial variation) to the variances of leaf traits and herbivory. Colors represent the sources of variation. A 1:1 reference line was shown.