Native and Invasive Woody Species Differentially Respond to Forest Edges and Forest Successional Age

Whalen Dillon,S Flory,Deah Lieurance,Keith Clay,Drew Hiatt

doi:10.3390/f9070381

Abstract

Forest fragmentation can promote non-native plant invasions by increasing invasive plant seed dispersal and resource availability along edges. These effects can vary based on forest age and may be influenced by differences in traits of native and invasive plant species. To determine how native versus invasive plant species respond to forest edges and forest successional age, we experimentally evaluated germination, survival, and growth of three native and three invasive woody plant species in eastern USA forests. Across all species, increasing distance from the edge resulted in more germination and less seedling growth, but had no effect on seedling survival. Generally, seedling growth was greater in younger forests and invasive species outperformed native species; however, there were significant species-specific differences in performance. For example, among native species, spicebush had poor growth performance but high survival, while redbud had low germination but high growth performance and survival. By contrast, the invasive privet and autumn olive produced more biomass with high relative growth rates, and autumn olive had exceptionally high germination but the lowest survival. Overall, our results suggest that while there are some general characteristics of invasive species, species-specific traits may better inform management strategies and improve predictions about biological invasions along forest edges.

Highlights

The susceptibility of forests to plant invasions is determined by both characteristics of invaders and environmental conditions of forest stands [1]
Forest fragmentation and proximity to forest edges have frequently been associated with non-native plant invasions (e.g., [3,4,5]), predominantly due to a combination of greater invasive plant propagule dispersal and higher resource availability along edges compared to forest interiors [6,7,8]
Introducing multiple native and co-occurring invasive species in a natural setting enabled the assessment of differences in species performance under similar environmental conditions

Summary

Introduction

The susceptibility of forests to plant invasions is determined by both characteristics of invaders and environmental conditions of forest stands [1]. Anthropogenic disturbances that fragment forests and create edges may increase propagule pressure through direct introductions on contaminated forestry or road building equipment. Forest edges can have unique biotic and abiotic conditions compared to forest interiors [12,13], including differences in productivity, nutrient cycling, and evapotranspiration due to modification of tree density and canopy cover along edges [14]. These effects in turn influence invasive and native plant species recruitment, growth, reproduction, and exposure to herbivory, often resulting in distinct

Methods

Results

Discussion

Conclusion