Deah Lieurance

Bioenergy Feedstocks at Low Risk for Invasion in the USA: a “White List” Approach

Proposed introductions of non-native bioenergy feedstocks have resulted in disagreements among industry, regulators, and environmental groups over unintended consequences, including invasion. Attempting to ban or “black list” known or high probability invasive species creates roadblocks without offering clear alternatives to industry representatives wishing to choose low invasion risk feedstocks. Therefore, a “white list” approach may offer a proactive policy solution for federal and state agencies seeking to incentivize the cultivation of promising new feedstocks without increasing the probability of non-native plant invasions in natural systems. We assessed 120 potential bioenergy feedstock taxa using weed risk assessment tools and generated a white list of 25 non-native taxa and 24 native taxa of low invasion risk in the continental USA. The list contains feedstocks that can be grown across various geographic regions in the USA and converted to a wide variety of fuel types. Although the white list is not exhaustive and will change over time as new plants are developed for bioenergy, the list and the methods used to create it should be immediately useful for breeders, regulators, and industry representatives as they seek to find common ground in selecting feedstocks.

Comparative Herbivory Rates and Secondary Metabolite Profiles in the Leaves of Native and Non-Native Lonicera Species

Non-native plants introduced to new habitats can have significant ecological impact. In many cases, even though they interact with the same community of potential herbivores as their new native competitors, they regularly receive less damage. Plants produce secondary metabolites in their leaves that serve a range of defensive functions, including resistance to herbivores and pathogens. Abiotic factors such as nutrient availability can influence the expression of defensive traits, with some species exhibiting increased chemical defense in low-nutrient conditions. Plants in the genus Lonicera are known to produce a diverse array of these secondary metabolites, yet non-native Lonicera species sustain lower amounts of herbivore damage than co-occurring native Lonicera species in North America. In this study, we searched for evidence of biochemical novelty in non-native species, and quantified its association with resistance to herbivores. In order to achieve this, we evaluated the phenolic and iridoid glycoside profiles in leaves of native and non-native Lonicera species grown under high and low fertilization treatments in a common garden. We then related these profiles to naturally occurring herbivore damage on whole plants in the garden. Herbivore damage was greater on native Lonicera, and chemical profiles and concentrations of selected putative defense compounds varied by species. Geographic origin was an inconsistent predictor of chemical variation in detected phenolics and iridoid glycosides (IGs). Overall, fertilization did not affect herbivore damage or measures of phenolics or IGs, but there were some fertilization effects within species. While we cannot conclude that non-natives were more chemically novel than native Lonicera species, chemical defense profiles and concentrations of specific compounds varied by species. Reduced attraction or deterrence of oviposition, specific direct resistance traits, or a combination of both may contribute to reduced herbivory and competitive advantages for non-native Lonicera in North America.

Predicted versus actual invasiveness of climbing vines in Florida

Climbing vines cause substantial ecological and economic harm, and are disproportionately represented among invasive plant species. Thus, the ability to identify likely vine invaders would enhance the effectiveness of both prevention and management. We tested whether the Weed Risk Assessment (WRA) accurately predicted the current invasion status of 84 non-native climbing vines in Florida. Seventeen percent of the species require further evaluation before risk of invasion can be determined. Of the remaining 70 species, the WRA predicted that 70% were at high risk for invasion, but only 50% of the 84 species are currently invasive in Florida. The status and risk prediction were inconsistent for 27% of the species: 15 non-invaders were predicted to be of high risk for invasion (i.e., false positive) and 4 invaders were predicted to be of low risk (i.e., false negative). Longer residence time in the flora was significantly correlated with higher invasion risk. Further investigation is necessary to identify whether residence time explains inconsistencies between risk and status conclusions, or whether the WRA over-predicts invasion risk. Nevertheless, the effects of invasive vines on native systems coupled with the influence of time on invasion status, suggest a precautionary approach is warranted when considering the introduction and management of non-native vines.

Weed Risk Assessments Are an Effective Component of Invasion Risk Management

Doria R. Gordon, S. Luke Flory, Deah Lieurance, Philip E. Hulme, Chris Buddenhagen, Barney Caton, Paul D. Champion, Theresa M. Culley, Curt Daehler, Franz Essl, Jeffrey E. Hill, Reuben P. Keller, Lisa Kohl, Anthony L. Koop, Sabrina Kumschick, David M. Lodge, Richard N. Mack, Laura A. Meyerson, Godshen R. Pallipparambil, F. Dane Panetta, Read Porter, Petr Pysek, Lauren D. Quinn, David M. Richardson, Daniel Simberloff, and Montserrat Vila*

Soil biota affect mycorrhizal infection and growth of Impatiens capensis and alter the effects of Lonicera maackii rhizosphere extracts.

Abstract Invasive plant species are one of the leading threats to the structure and function of native ecosystems. Increased attention has been given to the mechanisms that drive successful invasions, including those influencing belowground interactions between invasive and native plant species. To determine how the prominent invasive shrub Lonicera maackii (Rupr.) Herder affects a co-occurring native plant, we examined how a root/rhizosphere extract from L. maackii affected growth and mycorrhizal infection of Impatiens capensis Meerb. using epifluorescence microscopy of live roots. We also examined how the presence of a live soil microbial community influenced growth and mycorrhizal infection of I. capensis and how it the altered the effect of L. maackii extracts on these variables. In live soils, exposure to L. maackii extracts reduced mycorrhizal infection, reduced height, and slightly reduced shoot mass. In sterilized soils, exposure to L. maackii extracts slightly increased mycorrhizal infection, reduced height, and generally increased shoot, root, and total biomass. Soil sterilization substantially reduced mycorrhizal infection but increased growth of plants by 1.5–2 times over plants in corresponding treatments in live soils. The overall effect of the root/rhizosphere extract was dependent on the presence of a live microbial community in the soil, having generally positive effects on biomass in sterilized soils but negative effects in live soils. Despite strongly reducing mycorrhizal infection, removal of soil microbes by sterilization benefitted plant growth perhaps by removal of pathogenic microbes and/or microbes capable of metabolizing allelochemicals of L. maackii into more toxic forms.

Biomass allocation of the invasive tree Acacia auriculiformis and refoliation following hurricane-force winds1

Abstract Allometric equations and biomass allocation were determined for the aboveground wood, branch, twig, and leaf components of the invasive tree Acacia auriculiformis in south Florida prior to and after a major hurricane event. A destructive harvest was used and plant partitioned biomass was quantified for 35 trees prior to landfall of hurricane Wilma (October 2005), followed by an assessment of 29 hurricane impacted trees (representing all ontogeny classes) three months later. Allometric equations were developed to estimate plant partitioned biomass using diameter at base and diameter at breast height as predictors of biomass components, leaf area, leaf area ratio, and leaf weight ratio. Diameter at base was the best predictor of biomass allocation in all regression analyses. Hurricane force winds did not alter biomass of major woody components; however significant losses were observed in twig biomass and all measured leaf parameters. The replacement of damaged foliage resulted in overcompensation of leaf area and leaf area ratio. Similarly, leaf biomass, and leaf weight ratio also increased following the hurricane, but levels were lower than pre-hurricane observations. This research facilitates the prediction of A. auriculiformis biomass using non destructive sampling protocols while quantifying its resiliency and compensatory abilities following hurricane disturbance.

The influence of light habitat on the physiology, biomass allocation, and fecundity of the invasive shrub Amur honeysuckle (Lonicera maackii, Caprifoliaceae)1

Abstract Many exotic invasive plants exhibit plasticity in form and function across a range of environmental conditions, optimizing available resources in a manner that frequently outcompetes native organisms. The invasive shrub Lonicera maackii is one of the most prominent invasive plant species in the Midwestern United States. The objectives of this research were to investigate the morphological and physiological plasticity of this invasive shrub across light environments, and to study allometric parameters that will help estimate the aboveground biomass of L. maackii of all size classes. Shrubs were selected from open, forest edge, and understory habitats. Photosynthetic responses to light and leaf nitrogen content were measured throughout the growing season in 2003 and shrubs were harvested in October 2003. The maximum photosynthetic assimilation rates for open grown shrubs were more than double the values measured in the edge and understory. Maximum photosynthesis rates were strongly correlated with leaf nitrogen content, yet the photosynthetic nitrogen use efficiency was uniform across habitats. Open-grown shrubs had the highest values of total and partitioned biomass, although shrubs from all locations showed a proportional distribution to leaf, branch, trunk, and fruit. Although reproductive shrubs can produce copious amounts of fruits and seed in high light environments, fruit production still occurred in forest interior environments and is a direct source of seeds in the understory. Results suggest that because L. maackii exhibits physiological and morphological plasticity coupled with prolific fecundity (even in the understory), this species can persist in all habitats.