Abstract
In order to invade new ecosystems, invasive alien plants need to cope with different microbial communities. Whilst the ability to avoid antagonists is well recognized, the opportunity to establish mutualistic associations is less known, even in widespread invasive species such as Ailanthus altissima (Mill.) Swingle. We sought to evaluate whether the beneficial effects of arbuscular mycorrhizal fungi (AMF) on Ailanthus seedlings are maintained over time, under prolonged pot limitation. We compared three-month-, three-year- and four-year-old mycorrhizal seedlings grown in natural forest soil (NT) with seedlings grown in sterilized (ST) and non-mycorrhizal (NM) soils, in pots of 3.4 L (22 × 15 cm). Growth parameters and leaf traits were assessed, including carbon (δ13C) and nitrogen (δ15N) stable isotope compositions. NT seedlings showed relatively higher vigor in the early stage but, subsequently, the benefits provided by AMF were lost. Interestingly, mycorrhizal seedlings consistently showed about 2‰ δ13C enrichment, relatively to the other treatments. Negative linear relationships between leaf δ13C and N content were found. Higher photosynthesis rates and WUE are the likely causes of the early enhanced growth in mycorrhizal seedlings. The symbiotic relationship between AMF and Ailanthus could be driven by resource availability. Greater insights into such aspects could provide an improved perspective on the ecological limits of Ailanthus.
Highlights
IntroductionThe invasive nature displayed by certain alien plant species is generally attributed to differing physiological, ecological, and anthropic reasons, and is rarely dependent upon a single factor [1,2]
The invasive nature displayed by certain alien plant species is generally attributed to differing physiological, ecological, and anthropic reasons, and is rarely dependent upon a single factor [1,2].In order for invasive alien species to establish in new ecosystems, they would need to effectively interact with a different local biota [3]
The observation of long-term acclimation of A. altissima potted plants revealed that improved physiological status of mycorrhizal seedlings is strongly affected by pot limitation
Summary
The invasive nature displayed by certain alien plant species is generally attributed to differing physiological, ecological, and anthropic reasons, and is rarely dependent upon a single factor [1,2]. In order for invasive alien species to establish in new ecosystems, they would need to effectively interact with a different local biota [3]. In recent years, increasing attention has been paid to biotic interactions between the introduced species and the recipient ecosystem [4], including plant-soil microbe relationships, which strongly affect plant performance and competitive ability [5,6]. One general assumption is that invasive plant species may establish, on the whole, more positive interactions with soil biota than native co-occurring species. Exotic species may experience either partial or complete release of specialist enemies in co-evolution in the native range [7,8]. Alteration of the direction and amplitude of feedbacks with soil microorganisms has been found to disrupt the Forests 2018, 9, 409; doi:10.3390/f9070409 www.mdpi.com/journal/forests
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