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Chinese privet (Ligustrum sinense) has escaped cultivation in 20 states in the USA and is classified as a noxious weed in Florida, where its use is prohibited. There is confusion among producers and consumers surrounding the invasive status of its cultivars. In Florida, cultivars of an invasive wildtype species are also invasive unless proven otherwise and exempted from an invasive ruling. This study evaluated the fruiting and landscape performance of two cultivars of Chinese privet, 'Variegatum' (variegated privet) and 'Sunshine' (sunshine privet), and an interspecific hybrid of another form of privet, 'NCLX1' (L. × vicaryi, Golden Ticket®), planted in southwest, northcentral, and north Florida. 'Sunshine' and 'Variegatum' privet both performed well throughout the study with average quality ratings ranging from 3.2 to 4.9 (scale of 1–5) and a 100% survival rate during the nearly two-year study. 'NCLX1' privet also had a 100% survival rate at the southwest and northcentral sites, but 80% survival at the north Florida site. 'Variegatum' privet grew the largest in both height and width compared to 'Sunshine' and 'NCLX1' privet, that had similar heights. 'Variegatum' and 'NCLX1' privet flowered during the study, but 'Sunshine' privet did not. 'Variegatum' privet was the only cultivar evaluated to produce mature fruit and show clear signs of reversion back to its green wildtype form. The DNA content of all three cultivars suggests they are diploids, as is the wildtype form of Chinese privet. These results provide potential alternatives to Chinese privet for use in landscapes but recommend avoiding 'Variegatum' privet, due to its frequent reversion to the wildtype and its abundant fruit production. [ABSTRACT FROM AUTHOR]

Early detection and eradication of invasive plants are more cost-effective than managing well-established invasive plant populations and their impacts. However, there is high uncertainty around which taxa are likely to become invasive in a given area. Horizon scanning that combines a data-driven approach with rapid risk assessment and consensus building among experts can help identify invasion threats. We performed a horizon scan of potential invasive plant threats to Florida, USA--a state with a high influx of introduced species, conditions that are generally favorable for plant establishment, and a history of negative impacts from invasive plants. We began with an initial list of 2128 non-native plant taxa that are known invaders or crop pests. We built on previous invasive species horizon scans by developing databased criteria to prioritize 100 taxa for rapid risk assessment. The semi-automated prioritization process included selecting taxa "on the horizon" (i.e., not yet in the target location and not on a noxious weed list) with climate matching, naturalization history, "weediness" record, and global commonness. We derived overall invasion risk scores with rapid risk assessment by evaluating the likelihood of each of the taxa arriving, establishing, and having an impact in Florida. Then, following a consensus-building discussion, we identified six plant taxa as high risk, with overall risk scores ranging from 75 to 100 out of a possible 125. The six taxa are globally distributed, easily transported to new areas, found in regions with climates similar to Florida's, and can impact native plant communities, human health, or agriculture. Finally, we evaluated our initial and final lists for potential biases. Assessors tended to assign higher risk scores to taxa that had more available information. In addition, we identified biases towards four plant families and certain geographical regions of origin. Our horizon scan approach identified taxa conforming to metrics of high invasion risk and used a methodology refined for plants that can be applied to other locations. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Much is known about the elevational diversity patterns of native species and about the mechanisms that drive these patterns. A similar level of understanding is needed for non‐native species. Using published data, we examine elevational diversity patterns of non‐native plants and compare the resulting patterns with those observed for native plants. Location: Global. Methods: We compiled data from 65 case studies on elevational diversity patterns of non‐native plants around the world (including 32 cases in which both non‐native and native plants were sampled). We compared the elevational distributions (upper and lower limits, and extents) and diversity patterns of non‐native and native species. Results: Compared to native plant species, the elevational diversity patterns of non‐native plant species were more negative (47% vs. 13%) and less unimodal (44% vs. 84%). That is, non‐native species richness tended to be highest at lower elevations, whereas native species richness peaked at mid‐elevations. In cases where species richness for both non‐native and native species on the same mountains showed unimodal patterns in relation to elevation, maximum values in species richness occurred at lower elevations for non‐native species. Main conclusions: At present levels of invasion, non‐native and native species show different patterns in both distribution and diversity along elevational gradients worldwide. However, our observations constitute a snapshot of ongoing, long‐term invasion processes. As non‐native species typically show strong associations with human activities, future changes in human population (e.g. growth and migration), land use and climate change may promote upward spread of non‐native species and may thus increase risks of impact on native species and communities. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Invasive species occurrence is often related to the anthropogenic context of a given area. Quantifying the effects of roads is of particular interest as roads are a major vector for invasion. Our objective was to further quantify the effects of roads on forest plant invasion through a macroscale, high‐resolution investigation to assist effective invasion control and mitigation. Location: Eastern United States. Methods: Using invasive plant data from 23,039 forest inventory plots in 13 ecological provinces, we employed logistic regression to relate the odds of invasion to distance from a road, with adjustments for broadscale differences attributable to ecological provinces, and local scale differences in productivity, forest fragmentation and land use. Results: The overall proportion (P) of invaded plots was 0.58 (0.65 for plots within 50 m of a road), and the highest odds (P/1 − P) of invasion were found in relatively more productive, fragmented forest in landscapes with more than 10% agriculture or developed land cover. Wald chi‐square statistics indicated the best predictor of the odds of invasion was ecological province, followed by land use, productivity, forest fragmentation and distance from a road. Depending on the province, the adjusted odds of invasion decreased by up to 23% (typically 4%–10%) per 100 m distance from a road. The adjusted probability of invasion approached zero in only three provinces, for the least productive, least fragmented forest that was at least 2,000 m from a road in landscapes with less than 10% agricultural or developed land cover. Main conclusions: In the eastern United States, the existence of a nearby road is less important than the landscape context associated with the road. A purely road‐mediated effect has little practical meaning because anthropogenic activities and roads are pervasive and confounded. [ABSTRACT FROM AUTHOR]

Aim The ability to quantitatively measure the continuum of macroscale patterns of species invasion is a first step toward deeper understanding of their causal factors. We took advantage of two centuries worth of herbarium data, to evaluate a set of metrics to measure macroscale patterns, allowing cross-species comparisons of invasive expansion across large geographic areas. Methods We used herbarium specimens to reconstruct county-level invasion histories for two non-native plants (Alliaria petiolata and Lonicera japonica), with distinct spatiotemporal distribution patterns over the past two centuries. Using county centroids from species' initial occurrences, we quantified point pattern metrics from multiple disciplines (e.g. urban crime analysis, landscape ecology etc.) that are historically used at smaller spatial scales, to evaluate their ability to detect macroscale spatial diffusion and amount of directional expansion. Metrics were further assessed for their ease of use, data requirements, independence from other metrics and intuitiveness of interpretation. Important Findings We identified four suitable metrics for distinguishing differences in spatial patterns: (i) standard distance, (ii) number of patches, (iii) Euclidean nearest neighbor summary class statistic coefficient of variation and (iv) mean center that when applied to county-level presence data allowed us to determine the directions by which distributions expanded and if distributions increased via outward expansion, infilling and/or jump dispersal events. These metrics when compared during the same invasion phase are capable of quantifying macroscale variability among species in their distributional and dispersal patterns. Being able to quantify differences among species in these patterns is important in understanding the drivers of species dispersal patterns. These metrics therefore represent a simple yet thorough toolset for achieving this goal. [ABSTRACT FROM AUTHOR]

Forests worldwide are increasingly threatened by a wide range of human-induced socioecological challenges, such as urbanization, invasive species, and climate change. Using automated content analysis, we analyzed 14,855 abstracts published in seven prominent applied forestry journals between 2000 and 2013 to determine the degree to which these publications are providing forest managers with the information needed to address these challenges. We found that most articles still focus on more traditional forestry topics (e.g., silviculture and timber harvesting), with limited evidence of effort to address socioecological challenges. Although these traditional topics are essential to forest management, framing this research within the broader context of contemporary socioecological challenges will improve forest managers' abilities to address these challenges and contribute to the sustainability of forest ecosystems. [ABSTRACT FROM AUTHOR]

We conducted a three-year field experiment to determine if amending soils with mulched European buckthorn (Rhamnus cathartica) can limit reinvasion, and whether two methods of incorporation--tilling or surface application--produce similar results. Mulch (a high carbon:nitrogen [C:N] material) may reduce reinvasion by stimulating soil microbial immobilization of N. Converting the woody waste generated during buckthorn removal into mulch would also eliminate both the need to remove this waste from restoration sites and the expense of acquiring amendments from elsewhere. We found that adding buckthorn mulch to soils, whether tilled or not, did not decrease either buckthorn reinvasion or soil N availability. The mechanical disturbance of tilling, however, caused a large, prolonged reduction in reinvasion by killing a previously unrecognized but major contributor to reinvasion--small buckthorn individuals (most < 5 cm tall) that were undetected during initial removal. Recruitment of new individuals occurred during the experiment, but recruitment rate decreased rapidly over time, suggesting that buckthorn seeds are short-lived. Three major recommendations emerge: (1) buckthorn mulch should not be used to limit reinvasion; (2) tilling can greatly reduce reinvasion by killing buckthorn individuals that are undetected during initial removal; and (3) because buckthorn seeds appear to be short-lived, reinvasion can be reduced by repeated, annual follow-up control of undetected and newly recruited individuals. [ABSTRACT FROM AUTHOR]

We evaluated the efficacy of a mixture of ground hot mustard and water as a sampling method for earthworms (Lumbricina) in research projects involving citizen scientists. To do so we conducted a field experiment to determine if sampling earthworms using mustard-powder would reveal similar patterns of earthworm abundance and community composition as relying on the more difficult to prepare, and possibly hazardous, allyl isothiocyanate (AITC) solution. Earthworms were sampled using either mustard or AITC in four pairs of 0.25-m2 plots located in each of four woodland sites that were predicted to exhibit a range of earthworm densities. Soil gravimetric water content (GWC) of each plot was quantified as a covariate. For analyses of changes in abundance and community structure, earthworms were classified as belonging to one of five groups based on where they occur in the soil profile, developmental stage, and level of taxonomic identification. The two sampling techniques revealed similar earthworm abundances and community composition across the four sites (all Ps ≥ 0.16) and across the range in GWC (all Ps ≥ 0.36). We conclude that using the mustard-water mixture to sample earthworms at our study site appears to be just as effective and reliable as using AITC. The mustard-water mixture, which is easier to prepare and is less hazardous than AITC solution, should, therefore, be considered as an appropriate tool to be utilized by researchers who collaborate with citizen scientists to help collect the large dataseis needed to reveal how woodland management and restoration programs affect earthworms. [ABSTRACT FROM AUTHOR]

Invasive perennial species are frequently a barrier to native plant establishment in fertile sedge meadow wetland restorations. Amending soils with high carbon-to-nitrogen (C:N) materials may deplete nitrogen (N) and limit the establishment of invasive species, although the effectiveness of such amendments at depleting soil N in restored wetlands is largely unknown. Therefore we incorporated four high C:N materials (cedar, white pine, and red oak sawdust, as well as sucrose) into the soils of nonvegetated plots in a restored sedge meadow wetland and measured soil ammonium-N and nitrateN in relation to nonamended control plots over a 25-week period. All amendments depleted nitrate-N concentrations equivalently (67%-100%), although both the timing and the duration of this depletion varied among amendments. White pine sawdust was most effective, depleting nitrate-N for the entire 25 weeks. Sawdust from red oak and cedar depleted nitrate-N after 5 and 13 weeks, respectively. Lowered nitrate-N concentrations then persisted for the remaining 20 weeks in the red oak treatments, while the effects of cedar were short-lived (8 weeks). Sucrose depleted nitrate-N for 13 weeks. No amendment depleted ammonium-N concentrations, although cedar sawdust caused initial ammonium-N concentrations to increase by 300%-700%. Based on our findings, white pine sawdust will be more likely to deplete N effectively during the establishment of sedge meadow wetlands. It is unknown, however, if this depletion will suppress invasive perennials long enough to allow desired native species to establish a closed canopy and take up nitrogen, thereby limiting the chances of future invasions. [ABSTRACT FROM AUTHOR]

Efforts to eradicate invasive plants in restorations can unintentionally create conditions that favor reinvasion over the establishment of desired species, especially when remnant invasive propagules persist. Reducing resources needed by the invader for seedling establishment, however, may be an effective strategy to prevent reinvasion. Propagules of Phalaris arundinacea persist after removal from sedge meadow wetlands and reestablish quickly in posteradication conditions, hindering community restoration. A study was conducted in two experimental wetlands with controlled hydrologic regimes to determine if reducing light by sowing short-lived, nonpersistent native cover crops or immobilizing soil N by incorporating soil–sawdust amendments can prevent Phalaris reinvasion, allowing native communities to recover. A 10-species perennial target community and Phalaris were sown with high-diversity, low-diversity, or no cover crops in soils with or without sawdust, and seedling emergence, establishment, and growth were measured. High-diversity cover crops reduced light, decreasing Phalaris and target community seedling establishment by 89 and 57%, respectively. Short-term nitrogen reduction in sawdust-amended soils delayed Phalaris seedling emergence and decreased Phalaris seedling establishment by 59% but did not affect total target community seedling establishment. The target community reduced Phalaris seedling establishment as effectively as cover crops did. In plots where the target community was grown, amending soils with sawdust further reduced Phalaris seedling growth but not establishment. Results show that use of cover crops can reduce seedling establishment of desired species and is counterproductive to restoration goals. Further, establishing target species is more important and practical for limiting Phalaris reinvasion than is immobilizing nitrogen. [ABSTRACT FROM AUTHOR]

• Ornamental gardens provide ecosystem services that arthropod pests can limit. • Dense plantings can decrease pest abundance. • Species-rich and heterogeneous plantings can enhance richness and abundance of arthropod natural enemies. • Findings suggest that pest resistance can be enhanced via garden design. Urbanization is occurring at a dramatic rate, driving numerous unfavorable environmental effects. Urban designed ecosystems have been used to mitigate these impacts through the provisioning of ecosystem services. These services may be enhanced by manipulating the plant community composition and structure of designed ecosystems. Here we test this possibility by determining the degree to which plant diversity and structure in ornamental gardens are related to the ecosystem service of pest resistance, as inferred by the taxonomic richness (at the family level) and abundance of arthropod pests that harm plants and arthropod natural enemies that feed on pests. To do so, we quantified plant diversity and structure and collected arthropod pests and natural enemies in the winter and summer from 13 ornamental gardens nested within four residential communities in north-central Florida, United States. Pest abundance decreased exponentially as vegetation clumping and volume increased, but only in winter when pests were most abundant. Natural enemy abundance and family richness increased with the number of plant species present and spatial variability in plant species composition, again in the winter, but not summer. These relationships were likely driven by the direct effects of vegetation on arthropod habitat and not its indirect effects on temperature. Our results demonstrate the potential to enhance pest resistance in ornamental gardens by manipulating vegetation and reveal the need to expand these investigations into other designer ecosystems to enhance the ecosystem services they provide in urban landscapes. [ABSTRACT FROM AUTHOR]

• Human plant choice and a unique environment drive stormwater pond plant invasion. • Most plant invaders likely originated from horticultural introductions. • 93% of invaders have traits in common, including perennialism and acidic soil tolerance. • Perennialism and acidic soil tolerance are traits uncommon to urban plant colonizers. • Increased vegetation management selects for more disturbance-tolerant plants. [ABSTRACT FROM AUTHOR]

The excessive number of terms associated with invasive species, and their often incorrect usage, hinders stakeholder education about the threats of invasive species. Here we introduce seven terms (native, nonnative, introduced, established, invasive, nuisance, and range change) that are applicable across invasive taxa, understandable, typically interpreted correctly, and useful for describing most situations regarding invasive species. We also list six terms to avoid (native invasive, invasive exotic, invasive weed, alien, foreign, and nonindigenous) that create confusion via their misuse and misinterpretation. The terms we propose will increase understanding, thereby promoting behavior changes aimed at limiting the negative impacts of invasive species. [ABSTRACT FROM AUTHOR]

Research Highlights: We demonstrate a macroscale framework combining an invasibility model with forest inventory data, and evaluate regional forest exposure to harmful invasive plants under different types of forest protection. Background and Objectives: Protected areas are a fundamental component of natural resource conservation. The exposure of protected forests to invasive plants can impede achievement of conservation goals, and the effectiveness of protection for limiting forest invasions is uncertain. We conducted a macroscale assessment of the exposure of protected and unprotected forests to harmful invasive plants in the eastern United States. Materials and Methods: Invasibility (the probability that a forest site has been invaded) was estimated for 82,506 inventory plots from site and landscape attributes. The invaded forest area was estimated by using the inventory sample design to scale up plot invasibility estimates to all forest area. We compared the invasibility and the invaded forest area of seven categories of protection with that of de facto protected (publicly owned) forest and unprotected forest in 13 ecological provinces. Results: We estimate approximately 51% of the total forest area has been exposed to harmful invasive plants, including 30% of the protected forest, 38% of the de facto protected forest, and 56% of the unprotected forest. Based on cumulative invasibility, the relative exposure of protection categories depended on the assumed invasibility threshold. Based on the invaded forest area, the five least-exposed protection categories were wilderness area (13% invaded), national park (18%), sustainable use (26%), nature reserve (31%), and de facto protected Federal land (36%). Of the total uninvaded forest area, only 15% was protected and 14% had de facto protection. Conclusions: Any protection is better than none, and public ownership alone is as effective as some types of formal protection. Since most of the remaining uninvaded forest area is unprotected, landscape-level management strategies will provide the most opportunities to conserve it. [ABSTRACT FROM AUTHOR]

• Urban stormwater ponds used to manage runoff could facilitate plant invasion. • We identified over 76,000 stormwater ponds across Florida, US. • Ponds in Gainesville, FL harbor high richness and cover of invasive plants. • Invasion severity is highest in temporary ponds with little to no management. • Results highlight the commonality and disservices of these designed ecosystems. Designed ecosystems are built as part of ongoing urban expansion, providing a suite of valued ecosystem services. However, these new ecosystems could also promote disservices by facilitating the colonization and spread of invasive species. We conduct the first assessment of the quantity and invasion of an overlooked designed ecosystem: stormwater ponds. These ponds are commonly recommended for managing urban hydrology, but little is known about their ecology or extent of proliferation. Using a broad-scale survey of pond coverage in Florida, USA, we found that over 76,000 stormwater ponds have been built just in this state, forming 2.7% of total urban land cover. This extensive pondscape of manufactured habitats could facilitate species spread throughout urban areas and into nearby natural waterbodies. We also conducted a survey of the severity of plant invasion in 30 ponds in Gainesville, FL, US across two pond types (dry vs. wet), and a gradient of management intensities (low, medium, high) and pond ages. We unexpectedly found a high number of invasive plant species (28 in just 30 ponds). Ninety-six percent of surveyed ponds contained from one to ten of these species, with ponds exhibiting high turnover in invader composition (i.e., high beta diversity). The bank sections of dry unmanaged ponds exhibited the highest mean invasive species richness (5.8 ± 1.3) and the inundated centers of wet medium managed ponds exhibited the highest mean invasive species cover (34 ± 12%). Invasive plant richness and cover also tended to be greater in dry ponds with higher soil nutrient levels, and in older wet ponds. Therefore, we found that highly maintained and younger wet ponds were the least invaded. Nevertheless, common management practices that limit plant invasions may also limit native species establishment and invasion may increase in the decades following pond construction. [ABSTRACT FROM AUTHOR]