Abstract
Temporal heterogeneity of a resource supply can have a profound effect on the interactions between alien and native plant species and their potential invasiveness. Precipitation patterns may be variable and result in a higher heterogeneity of water supply with global climate change. In this study, an alien shrub species, Rhus typhina, introduced to China from North America and a native shrub species, Vitex negundo var. heterophylla, were grown in monoculture and mixed culture under different water supply regimes, with four levels of water supply frequencies but with a constant level of total supplied water. After 60 days of treatments, the alien species was found to be the superior competitor in the mixed culture and was unaffected by changes in the water supply pattern. The dominance of R. typhina was mainly owing to its greater biomass and effective modulation of leaf physiology. However, in the mixed culture, V. negundo var. heterophylla exhibited both leaf- and whole-plant-level acclimations, including higher leaf length to petiole length and root to shoot biomass ratios, and lower specific leaf weight and leaf length to leaf width ratio. Plant height of V. negundo var. heterophylla was comparable to that of R. typhina in the mixed culture, which is a strategy to escape shading. Although water treatments had little effect on most traits in both species, the possible influence of water regimes should not be neglected. Compared with high-frequency water supply treatments, more individuals of V. negundo var. heterophylla died in low-water-frequency treatments when in competition with R. typhina, which may lead to species turnover in the field. The authors recommended that caution should be exercised when introducing R. typhina to non-native areas in the context of global climate change.
Highlights
Alien species have potentially significant effects on local ecosystems, including population dynamics, community composition, and ecosystem function [1, 2, 3]
In R. typhina, leaf chlorophyll content was higher in the mixed culture than in the monoculture treatment (Fig 2A), whereas a decreasing trend was present in V. negundo var. heterophylla based on the leaf area (Fig 2B)
The native species grown in mixed culture exhibited more morphological plasticity, including lower LMA, Leaf lengths (LL)/leaf widths (LW), and γ values, and higher LL/petiole lengths (PL) values (Figs 2 and 3)
Summary
Alien species have potentially significant effects on local ecosystems, including population dynamics, community composition, and ecosystem function [1, 2, 3]. The structure and function of local ecosystems can change entirely if the alien species exert high pressure on the native dominant species in a local area. Significant differences between the leaf traits of cooccurring alien and native species have been reported. Most of the traits are associated with rapid carbon capture and fast relative growth rate. In low-resource environments, plant traits associated with high resource-use efficiency favor alien species colonization [2]. Relatively few studies have focused on pair-wise competition of alien and native species, especially in the context of changing resource supply patterns (but see [8, 9])
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