Eradication Of Invasive Plants Research Articles

Effects of salinity, temperature, and immersion conditions on seed germination of invasive Spartina alterniflora Loisel (smooth cordgrass) in Japan

Spartina alterniflora is a halophytic perennial grass species that has invaded coastal wetlands worldwide, including tidal flats in Japan. Rapid removal or eradication of invasive plants is desirable because of their severe ecological impact on local ecosystems. Seed germination is the main cause of its distribution and invasion. Understanding germination characteristics of S. alterniflora is critical for the prediction and early detection of its populations in new environments. Therefore, we aimed to investigate the effects of salinity (0, 10 20, 30, and 40 g/L artificial seawater), temperature (15, 20, 25 °C for constant, and 15/25 °C for alternating), and seed immersion (5 ml and 40 ml medium) based on laboratory experiments to evaluate the physicochemical environmental factors that facilitate the germination of S. alterniflora seeds. The cumulative germination rate and mean germination time were significantly affected by temperature and salinity but not by immersion. Increased salinity gradually reduced the cumulative germination rate in all temperature and immersion conditions. The mean germination time tended to be prolonged with the salinity level. A constant temperature of 25 °C promoted higher seed germination compared to constant temperatures of 15 and 20 °C. Notably, alternating temperature between 15 and 25 °C induced a higher seed germination compared to other constant temperatures. In addition, alternating temperatures varied the mean germination time to facilitate sensitivity to salinity, indicating that temperature fluctuation is a key factor that stimulates seed germination of S. alterniflora. These results suggest that S. alterniflora seeds prefer gaps in vegetation canopies and a low depth of burial in soil. Further studies are needed to analyze prevention strategies for the eradication of this invasive species in Japan.

Consensus and controversy in the discipline of invasion science.

Approaches, values, and perceptions in invasion science are highly dynamic, and like in other disciplines, views among different people can diverge. This has led to debate in the field specifically surrounding the core themes of values, management, impacts, and terminology. Considering these debates, we surveyed 698 scientists and practitioners globally to assess levels of polarization (opposing views) on core and contentious topics. The survey was distributed online (via Google Forms) and promoted through listservs and social media. Although there were generally high levels of consensus among respondents, there was some polarization (scores of ≥0.39 [top quartile]). Relating to values, there was high polarization regarding claims of invasive species denialism, whether invasive species contribute to biodiversity, and how biodiversity reporting should be conducted. With regard to management, there were polarized views on banning the commercial use of beneficial invasive species, the extent to which stakeholders' perceptions should influence management, whether invasive species use alone is an appropriate control strategy, and whether eradication of invasive plants is possible. For impacts, there was high polarization concerning whether invasive species drive or are a side effect of degradation and whether invasive species benefits are understated. For terminology, polarized views related to defining invasive species based only on spread, whether species can be labeled as invasive in their native ranges, and whether language used is too xenophobic. Factor and regression analysis revealed that views were particularly divergent between people working on different invasive taxa (plants and mammals) and in different disciplines (between biologists and social scientists), between academics and practitioners, and between world regions (between Africa and the Global North). Unlike in other studies, age and gender had a limited influence on response patterns. Better integration globally and between disciplines, taxa, and sectors (e.g., academic vs. practitioners) could help build broader understanding and consensus.

Scanning the horizon for invasive plant threats using a data-driven approach

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 data-based 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.

Habitat specialist spiders in coastal dunes benefit from eradication of the invasive shrub Rosa rugosa

Eradication of invasive plants from natural habitats may have positive side effects other than removal of the invasive species. The study describes an unintended but positive consequence of a program for eradication of Rosa rugosa in Danish coastal dunes. The measures undertaken leaves areas formerly covered by rose bushes as bare sandy patches. Vegetation-free habitat has become rare in coastal dune areas due to effective control of the natural sand dynamics, with potentially devastating consequences for the most specialized dune fauna. As a result, xerothermic species, i.e. species that depend on dry, sun-exposed and vegetation-free habitat, are particularly threatened. In a rose eradication program carried out by the Danish Nature Agency in Thy, Denmark, I tested the hypothesis that habitat specialist spiders in general and xerothermic spider species in particular would take advantage of such newly created habitat. I sampled the spider fauna by pitfall traps in areas cleared of roses, in adjacent marram vegetation, and in remaining small rose patches. The assemblage of spiders caught in the cleared areas consisted of species with more narrow habitat occurrence and stronger preference for openness of the habitat compared with those of the marram vegetation and rose patches. Also, the proportion of xerothermic individuals and species was increased in the assemblages of the cleared areas. I conclude that the habitat disturbance from rose eradication favours specialist spiders by substituting for the natural sand dynamics. Creation of vegetation-free areas benefits dune specialist species and should be implemented for that purpose even if not combined with eradication of roses.

Native seed addition as an effective tool for post-invasion restoration

Invasive plant species reduce biodiversity, alter ecosystem processes, and cause economic losses. Control of invasive plants is therefore highly desired by land managers and policy makers. However, invasive plant control strategies frequently fail, partly because management often concentrates only on the eradication of invasive plants and not on revegetation with native species that use the available resources and prevent reinvasion. In this study, we focused on the intracontinental invader Rumex alpinus L., which was introduced by humans from the Alps to the lower mountains of Central Europe, where it has spread to semi-natural meadows, suppresses local biodiversity, and reduces the quality of hay used as cattle fodder. The species can be effectively removed using herbicide, but this leaves behind a persistent seed bank. Without further treatment, the invader rapidly regenerates and reinvades the area. We supplemented the herbicide treatment by adding the seeds of native grasses. Addition of native-seed effectively suppressed the regeneration of the invader from the seed bank, reduced its biomass, and consequently, prevented massive reinvasion. While the invader removal was successful, the restored community remained species-poor because the dense sward of native grasses blocked the regeneration of native forbs from the seed bank. Nevertheless, the addition of native seed proved to be an effective tool in preventing reinvasion after the eradication of the invasive plant.

Soil microbial communities in restored and unrestored coastal dune ecosystems in California

Most restoration projects involving invasive plant eradication tend to focus on plant removal with little consideration given to how these invasives change soil microbial communities. However, soil microorganisms can determine invasibility of habitats and, in turn, be altered by invasives once established, potentially inhibiting native plant establishment. We studied soil microbial communities in coastal dunes with varying invasion intensity and different restoration approaches (herbicide, mechanical excavation) at Point Reyes National Seashore. Overall, we found evidence of a strong link between bacterial and fungal soil communities and the presence of invasives and restoration approach. Heavily invaded sites were characterized by a lower abundance of putatively identified nitrifiers, fermentative bacteria, fungal parasites, and fungal dung saprotrophs and a higher abundance of cellulolytic bacteria and a class of arbuscular mycorrhizal fungi (Archaeosporomycetes). Changes in soil microbiota did not fully dissipate following removal of invasives using herbicide, with exception of reductions in cellulolytic bacteria and Archaeosporomycetes abundance. Mechanical restoration effectively removed both invasives and soil legacy effects by inverting or “flipping” rhizome‐contaminated surface soils with soils from below and may have inadvertently induced other adverse effects on soils that impeded reestablishment of native dune plants. Land managers should consider additional measures to counteract lingering legacy effects and/or focus restoration efforts in areas where legacy effects are less pronounced.

Evaluation of Heracleum sosnowskyi Frost Resistance after Snow Cover Removal in Early Spring

The development of environmentally safe and cost-effective methods for controlling invasive species Sosnowsky’s hogweed (Heracleum sosnowskyi Manden.) is an urgent issue for the European part of Russia. The article presents findings of an experiment on the effect of snow cover removal from the areas occupied by H. sosnowskyi in the early spring period (the beginning of March 2018) in the vicinity of the city of Syktyvkar (Komi Republic, Russia). The snow depth reached 100 cm on the intact plots; the sum of below-zero air temperatures measured at 6 a.m. constituted –448°C, with a minimum of –29.0°C during the experiment. The number of H. sosnowskyi plants of all age groups at the experimental plots (with removed snow cover) was shown to be significantly decreased. The median seedling density (pcs. per square meter) was equal to zero. Most of the surviving plants were located along the sides and in the corners of experimental plots. This can be explained by the higher temperature of soil on the borders of plots with an intact snow cover. The results of the experiment may be used for development of invasive plant eradication technology by removal of the snow cover. This technology can be suitable for kindergartens, schools, hospitals, and water protection zones, where the use of chemical methods of plant control is limited or prohibited. The obtained data set with respect to H. sosnowskyi monitoring is available in the repository of Zenodo.

Invasive-Plant-Removal Frequency—Its Impact on Species Spread and Implications for Further Integration of Forest-Management Practices

For a given invasive plant species and control method, effective invasive plant eradication requires regular monitoring and management. While most previous studies characterize invasive plant species, develop appropriate control methods, or prioritize species for management using aggressiveness and other considerations, few study why some forestland owners are less likely than others to regularly remove invasive plant species. Such information is useful in prioritizing and targeting forestland owners who are at greater risk for invasion, with the stands threatening adjacent forestlands. Towards this end, we surveyed 1800 forestland owners in Virginia and Texas. We use data on forestland owners’ socioeconomics and forestland features—such as acreage, forestland ownership objectives, and forest management activities—to determine how these factors affect the regularity of invasive-plant removal. For these purposes, we used the Cochran–Armitage trend test, the Cochran–Mantel–Haenszal regression, odds ratio estimates, and partition-analysis techniques. Our results suggest that female forestland owners, owners with smaller forestlands, and forestland owners without written forest-management plans are less likely than others to regularly remove invasive plant species. Forest-management activities, such as building/maintaining roads in the forestland, partially harvesting stands, and wildlife- and fisheries-improvement projects, also significantly predict a more regular invasive-plant-removal tendency. However, since these activities are potential pathways for the spread of invasive plant species, we controlled for the other significant covariates and measured the relationship between frequent practice of the given forest-management activities and having a tendency to regularly remove invasive plant species. The results suggest that forestland owners that regularly practiced the said forest-management activities have higher odds for tending to remove invasive plant species regularly, suggesting that, despite their demonstrated effort at removing invasive plant species from their forest, their management activities may be inadvertently contributing to the spread of invasive plant species. These results highlight the importance of integrating invasive-plant-removal plans with forest-management plans as well as forestland owners’ educational and outreach needs.

Short-term soil nutrient and plant community responses to the eradication of a nitrogen fixing tree, Lupinus arboreus

Invasive plant eradication aims to restore an original state by eliminating the plant and its alteration of ecosystem structure and function. The method by which an invasive plant is eradicated is known to influence restoration success; however, success may be impeded by a legacy effect. We sought to examine how the soil nutrient pool and plant community assembly responded to the eradication of an invasive nitrogen-fixing legume, Lupinus arboreus, using three different techniques. We applied herbicide to six mature plants and with a handsaw removed the above ground biomass of 12 mature plants; six of these were left in situ to decompose and six were removed from site. Soil nutrient concentrations were measured, and plant community composition was monitored, in the treatment and reference plots over the following 13 months. Eradication resulted in a significant increase in extractable ammonium-N and potassium, in contrast nitrate-N declined. The plant community changed as a result of felling L. arboreus, and the removal of all biomass initially resulted in an increase in native plant cover. By the end of the experimental period, however, L. arboreus seedlings were increasing in abundance and native cover was declining. The application of herbicide resulted in the slow decay of the mature plant and as such delayed an increase in exotic species cover and inhibited L. arboreus germination. Nutrient concentrations in the eradication plots were not significantly different from the reference plots at the end of the experimental period. The impact of L. arboreus on the soil nutrient pool remains after eradication, a legacy effect which will hinder restoration of the original structure and function in the long term.

Determinants of native and non‐native plant community structure on an oceanic island

AbstractUnderstanding the relative importance of environmental and anthropogenic factors in driving plant community structure, including relative dominance of native and non‐native species, helps predict community responses to biological invasions. To assess factors influencing plant communities on San Clemente Island, USA, we conducted an islandwide vegetation survey in which we measured plant species richness and percent cover of native and non‐native plants, as well as physical environmental variables, soil chemical properties, abundance of soil microbial functional groups (e.g., arbuscular mycorrhizal fungi [AMF]), and a human disturbance variable (distance to road). We found that total plant species richness decreased with increasing non‐native plant cover, soil pH, and AMF abundance. Native plant cover increased with increasing distance to a major paved road and decreased with increasing soil moisture and pH. Non‐native plant cover decreased with increasing distance to a major paved road and increased with increasing soil moisture, AMF abundance, and from southwest to northeast, a geographic/climatic gradient that represents increasing moisture. Nonmetric multidimensional scaling ordination further illustrated that trends in plant community composition were correlated with elevation, distance to a major paved road, and soil moisture, organic matter, and ammonium. These results suggest complex effects of physical environmental, soil chemical, and human‐related factors on plant community structure on an oceanic island, and moreover, that different factors affect cover of native and non‐native plants. Notably, our observation of apparent moisture limitation of non‐native plants suggests that, in some contexts, drought conditions can limit plant invasions and may even represent an opportunity for efficient control or eradication of invasive plants. The apparent negative effect of non‐native plants on native plant cover and overall plant species richness represents a conservation concern for native biodiversity on oceanic islands and suggests the potential for community reassembly as invasive species increasingly dominate due to anthropogenic disturbances.

Using Microwave Soil Heating to Inhibit Invasive Species Seed Germination

Successful invasive plant eradication is rare, because the methods used target the adult stage, not taking into account the development capacity of a large seedbank. Heating by microwave was considered, because it offers a means to quickly reach the temperature required for loss of seed viability and inhibition of germination. Previous results were not encouraging, because homogeneous and deep-wave penetration was not achieved, and the various parameters that can affect treatment effectiveness were incompletely addressed. This study aimed to determine, under experimental conditions, the best microwave treatment to inhibit invasive species seed germination in terms of power (2, 4, 6 kW) and duration (2, 4, 8 min) of treatments and depending on soil moisture (10%, 13%, 20%, 30%) and seed burial depth (2, 12 cm). Three invasive species were tested: Bohemian knotweed, giant goldenrod, and jimsonweed. The most effective treatments required relatively high power and duration (2kW8min, 4kW4min, 6kW2min, and 6kW4min; 4kW8min and 6kW8min were not tested for technical reasons), and their effectiveness diminished with increasing soil moisture with germination percentage between 0% and 2% for the lowest soil moisture, 0% and 56% for intermediate soil moisture, and 27% and 68% in control treatments. For the highest soil moisture, only 2kW8min and 4kW4min reduced germination percentage between 2% and 19%. Occasionally, germination of seeds located at the 12-cm depth was more strongly affected. Giant goldenrod seeds were the most sensitive, probably due to their small size. Results are promising and justify further experiments before developing a field microwave device to treat large volumes of soil infested by invasive seed efficiently and with reasonable energy requirements. Other types of soil, in terms of texture and organic matter content, should be tested in future experiments, because these factors influence soil water content and, consequently, microwave heating.

Greenhouse gas emissions following an invasive plant eradication program

Many efforts have been made to control invasive Spartinaalterniflora and to restore coastal wetlands along the Pacific Rim. This study is the first to report the effects of a Spartina-eradication program on soil greenhouse gas (GHG) emissions. In this study S. alterniflora was eradicated in a pilot program covering an area of 0.63km2 in a Yangtze River estuarine wetland. In the following year after the eradication program was complete, plant growth, soil microbial activities, as well as CO2, CH4 and N2O emissions were investigated. S. alterniflora ramets did not re-grow after the eradication program, while a native plant, Phragmites australis, thrived and produced taller but rather thinner ramets. CO2, CH4 and N2O emissions in areas previously covered by S. alterniflora declined based on measurements made a year after eradication. This may have been caused by the removal of this plant as well as by flooding and/or by the reduced soil microbial biomass and dehydrogenase and β-glucosidase activities. CH4 fluxes significantly increased in the program sites where the native species P. australis was retained, while CO2 and N2O fluxes showed no significant changes. Our study revealed that GHG emissions can be greatly altered by an invasive plant eradication program and analysis of such emissions should be included in comprehensive assessments designed to guide successful restoration practices. Based on scenario analysis, we suggest that from the view of GHG emission equivalency, planting P. australis in approximately 50% of the area where S. alterniflora was eradicated would be appropriate in future management.

Measuring performance of invasive plant eradication efforts in New Zealand

New Zealands Biosecurity Act 1993 which has enabled local governments to pursue eradication of 69 different invasive plant taxa is strongly influenced by new public management doctrine and its emphasis on specific management objectives annual plans and performance measures Data to support meaningful eradication performance measures are still rare despite such requirements It can take several decades to achieve eradication since seed banks and other factors often complicate invasive plant eradication efforts Since eradication of all sites is often preceded by the gradual elimination of some infestations evaluating trends in site status (whether aboveground plants are present or absent) and site population size (based on complete censuses) may help biosecurity staff to evaluate progress improve eradication efforts and communicate their successes These performance measures are illustrated using a 7year dataset from Raoul Island