Giant reed (Arundo donax) is an invasive weed that is native to the Old World. Tens of thousands of hectares of riparian habitat in the Rio Grande Basin (RGB) in Texas and Mexico have been heavily affected by invasions of Arundo. Additionally, many other watersheds across the southwestern United States have also been affected. Giant reed is being targeted for biological control because it displaces native vegetation and consumes water that could potentially be used for agricultural and municipal purposes, especially in areas with limited access to water. Finding the best-adapted insects for biological control involves locating the origin(s) of this plant. To narrow down the proximal source(s) of invasion of giant reed in the RGB, 10 microsatellite markers were developed. An analysis of 203 Old World and 159 North American plants, with an emphasis on the RGB, indicated a reduction in the allelic diversity in the introduced range compared with the Old World. Clonal assignment, neighbor joining, principal coordinates analyses, and STRUCTURE analyses were consistent and implied multiple introductions in North America, with one (likely clonal) lineage responsible for the invasion of the RGB, northern Mexico, and other parts of the southwestern United States. Although no identical matches with the RGB lineage were found in the Old World, several close matches were found on the Mediterranean coast of Spain.

Nomenclature: Giant reed, Arundo donax L

Management Implications: Giant reed is a clonal, rhizomatous grass that has invaded tens of thousands of hectares of riparian habitat throughout the Rio Grande Basin (RGB) and other parts of the southwestern United States. In this paper, we used microsatellites to determine the original population source(s) of the invasive Arundo donax in the RGB to locate biocontrol agents from the Old World. Biological control is deemed the best long-term option for control of giant reed. Chemical and mechanical control of A. donax is expensive, especially in heavily affected areas. Although A. donax is clonal, some genetic variation was found throughout the RGB. We also discovered multiple introductions in the United States, but only one lineage is responsible for the invasion in the RGB. This indicates that a limited sampling of biocontrol insects might be effective in controlling A. donax along the Rio Grande. Additionally, these biocontrol agents might also be effective in controlling giant reed in others areas where this lineage has been introduced, such as California and Mexico.

Prioritizing management of invasive plants is important for large land management entities, such as federal and state public land stewards, because management resources are limited and multiple land uses and management objectives are differentially impacted. Management decisions also have important consequences for the likelihood of success and ultimate cost of control efforts. We applied multi-criteria decision analysis methods in a geographic information system using natural resource and land use data from Fort Bragg, North Carolina. Landscape-scale prioritization was based on a hierarchical model designed to increase invasive plant management efficiencies and reduce the risk of impacts to key installation management goals, such as training-land management and protected species conservation. We also applied spatial sensitivity analyses to evaluate the robustness of the prioritization to perturbations of the model weights, which were used to describe the relative importance of different elements of the hierarchical model. Based on stakeholders' need for confidence in making management investments, we incorporated the results of the sensitivity analysis into the decision-making process. We identified high-priority sites that were minimally affected by the weight perturbations as being suitable for up-front management and evaluated how adopting this strategy affected management area, locations, and costs. We found that incorporating the results of the sensitivity analysis led to a reduced management area, different target locations, and lower costs for an equal area managed. Finally, we confirmed the distinctiveness of the approach by comparing this same subset of prioritized sites with locations representing species-centric strategies for three invasive plants and their aggregate distribution. By supplying pragmatic information about the localized effects of weighting uncertainty, spatial sensitivity analyses enhanced the invasive plant management decision-making process and increased stakeholder confidence.

Management Implications: Limited resources force land managers to make choices about where and when to implement invasive plant management actions. Ideally these choices will satisfy the multiple land management objectives, legal requirements, and stakeholders pertinent to most invasive plant management campaigns. Multi-criteria decision analysis (MCDA) provides a proven approach for solving complex decision problems, but has not been widely used for invasive plant management. We applied one MCDA method, the Analytic Hierarchy Process (AHP), to a landscape-scale prioritization of invasive plant management at Fort Bragg, North Carolina. Cognizant of the potential impact of weight uncertainty on AHP outputs, we additionally used spatial sensitivity analyses to reveal high-priority locations where investments in invasive plant management could be made with a degree of confidence deemed acceptable by installation stakeholders.

Our results showed that AHP can be easily implemented in a geographic information system to match local invasive plant management concerns and that incorporating spatial sensitivity analysis into the decision-making process affected the area, locations, and costs associated with management implementation. Results of the integrated prioritization also differed from ad hoc species-centric strategies in terms of the locations identified for management and the priority values associated with these locations.

The AHP can be applied to diverse invasive plant management prioritization problems using available data, expert opinion, and science-based heuristics, but can also be expanded to include new insights provided by additional data, stakeholder input, or models of relevant system processes as they become available. Additionally, spatial sensitivity analyses of AHP weights, decision criteria, or both are recommended in or

Medusahead is a close relative of bread wheat that is native to Eurasia but has become a noxious, invasive weed in North America. Intergeneric use of primers for bread wheat simple-sequence repeat (SSR) markers was tested in medusahead in order to expand the pool of available genetic resources for study of this plant. Forty-two primer pairs were screened in medusahead, of which 29 produced visible bands in agarose gels. Amplicons from eight of these markers were sequenced and analyzed for the presence of SSRs and single-nucleotide polymorphisms (SNPs) among medusahead individuals from six populations in the western Great Basin. Of the eight sequenced amplicons, two contained SSRs, both of which were polymorphic and shared by the original bread wheat marker. Six of the eight markers combined to detect 33 SNP loci. BLAST comparisons of the eight amplicons revealed variable numbers of matching sequences from wheat and other grass species ranging from 0 to > 200 matches. Using data from the polymorphic loci, population genetic analysis of the six invasive medusahead populations indicated that they arose from two separate introductions with two additional subclusters possible within the two principal clusters. Extrapolating from these results, it is reasonable to expect that between 170 and 830 of the approximately 1,200 publicly available bread wheat SSRs would produce useful marker loci in medusahead.

Nomenclature: Bread wheat, Triticum aestivum L., medusahead, Taeniatherum caput-medusae (L.) Nevski, ELYCM

Management Implications: Medusahead is an invasive annual grass that is unpalatable to livestock and contributes to increased wildfire risk on 250,000 ha of rangelands, mainly in western North America. It is native to Eurasia and has no known natural enemies in North America and is now the target of a classical biological control program. Currently there are few genetic markers available for the study of medusahead. An increase in the number of genetic markers would enable or facilitate many studies with important implications for field practitioners. These include precise genetic fingerprinting for medusahead plants to track the spread of invasive populations and link them to putative source populations in the weed's native range, as well as genetic analyses of medusahead traits associated with invasiveness, which will lead to improved control strategies through better understanding of the invasion process. Making new genetic markers can be expensive and technically challenging but this article shows that markers for medusahead can be adapted from the large pool of existing wheat simple-sequence repeat (SSR) markers using technology available to most minimally equipped genetic labs at a reduced cost compared to conventional SSR marker development. These results suggest that between 170 and 830 wheat SSR primer pairs could be successfully adapted to produce genetic markers in medusahead.

Dalmatian toadflax is listed as a noxious weed in most of the western United States, but control of this species has not been extensively studied in California. Studies in other states show effective control of Dalmatian toadflax with picloram, but this herbicide is not registered for use in California. In addition, reports vary as to the optimal timing for herbicide applications. In this study we evaluated several herbicides with combined foliar and soil-residual activity at two times of application: postsenescence (fall) and rosette (winter to early spring). We applied two series of treatments (2008 and 2009 to 2010) on adjacent sites in high desert scrub of southern California. In the year of treatment and the following year, we evaluated Dalmatian toadflax cover and presence/absence of associated dominant species (≥ 5% cover). Although time of application, treatment, and timing by treatment interaction all produced significant differences in Dalmatian toadflax cover in the 2008 trial, only the high rate of aminocyclopyrachlor (280 g ae ha⁻¹) applied to dormant plants in fall consistently reduced cover through the second year. No treatments at the rosette stage consistently produced 2 yr of control. In 2009 to 2010, treatments were more effective, probably owing to higher precipitation in spring. In both dormant and rosette applications made in 2009 to 2010, aminocyclopyrachlor (140 and 280 g ae ha⁻¹) and aminocyclopyrachlor chlorsulfuron (140 g ae ha⁻¹ 53 g ai ha⁻¹) gave second year control; chlorsulfuron at the dormant stage (105 and 158 g ai ha⁻¹) and aminopyralid at the rosette stage (245 g ae ha⁻¹) also gave 2 yr of control. The treatments had only minor effects on grass species. The response of broadleaf species varied among treatments, with aminocyclopyrachlor at the high rate increasing Eriogonum spp., but greatly reducing Asteraceae species. These results provide options for the management of Dalmatian toadflax in California and other western states.

Nomenclature: Aminocyclopyrachlor, aminopyralid, chlorsulfuron, picloram, Dalmatian toadflax, Linaria dalmatica (L.) Mill. subsp. dalmatica LINDA, Eriogonum spp

Management Implications: Dalmatian toadflax is usually controlled with picloram in most areas of the western United States. However, results can vary owing to application timing or to environmental factors. Furthermore, picloram is not registered for use in California, and thus is not an option for controlling this plant in California's high deserts. In this study we evaluated several herbicides with combined foliar and soil-residual activity at two times of application: postsenescence (fall) and rosette (winter to early spring). The trial was conducted twice. The primary chemicals tested included aminocyclopyrachlor, aminopyralid, chlorsulfuron, dicamba, imazapic, imazapyr, metsulfuron, picloram, and 2,4-D, but only aminocyclopyrachlor, aminopyralid, and chlorsulfuron were effective. Aminocyclopyrachlor (280 g ae ha⁻¹), applied to dormant plants in fall, gave the most consistent long-term control, providing > 90% reduction in Dalmatian toadflax cover in both trials in the second season after treatment. This rate also increased native species in the genus Eriogonum, but reduced the presence of members of the Asteraceae. Applications at the rosette stage were less consistent between trials, probably because of differences in spring rainfall between the two trial years. In the first trial, with very low spring rainfall, none of the rosette-stage treatments produced 2 yr of control. However, in the second trial, with considerably more spring rainfall, both dormant and rosette applications of aminocyclopyrachlor (2 and 4 oz ae ac⁻¹) and aminocyclopyrachlor chlorsulfuron (2 oz ae ac⁻¹ 0.75 oz ai

Understanding seed characteristics and seedling establishment patterns is essential for the development of effective management strategies for invasive annual species. Dittrichia graveolens (stinkwort) has increased its range rapidly within California since 1995, yet its biology is not well understood, which has led to poorly timed management. In this study, seed viability, germination, longevity, and dormancy, as well as seedling emergence characteristics of D. graveolens were evaluated in field, greenhouse, and laboratory experiments in Davis, CA, over a 2-yr period (fall 2010 to summer 2012). In the laboratory, seed germination of D. graveolens occurred at a wide range of constant temperatures (12 to 34 C). Cumulative germination was comparable to total seed viability (80 to 95%) at optimal germination temperatures, indicating that primary (innate) dormancy is likely absent. The base temperature for germination was identified using a thermal time model: 6.5 C and 4 C for 2010 and 2011 seed populations, respectively. In the field, seedlings emerged from fall through spring following precipitation events. A very low percentage of seedlings (2.5%) emerged in the second year after planting. Equivalent seedling emergence was observed over a wide range of light conditions (100, 50, 27, and 9% of available sunlight) in a greenhouse experiment, indicating that seed germination is not limited by high or low light. Results from these seed experiments improve our understanding of the reproductive biology of this rapidly expanding exotic annual and provide valuable information for developing effective timing and longevity of management programs.

Nomenclature: Stinkwort, Dittrichia graveolens (L.) Greuter. Synonyms: Inula graveolens L., Erigeron graveolens L

Management Implications: Dittrichia graveolens is an invasive annual broadleaf plant of Mediterranean origin. It has become well established in California and has spread effectively over the past two decades. Plants establish in disturbed areas such as roadsides, gravel mines, and heavily grazed rangeland; at wetland margins; and on riparian floodplains. Individual D. graveolens plants produce many thousands of small, pappus-bearing achenes that disperse along transportation corridors. Control of D. graveolens has been challenging in the early stages of its invasion due to the absence of information on basic biology and ecology, both scientific and anecdotal. Most importantly, misunderstanding of seedling emergence has led to improper timing of control efforts.

Dittrichia graveolens seeds disperse in late fall and, based on our findings, the majority of seeds germinate in the winter and spring following major rain events, with few seedlings emerging the second year after dispersal. Mature seeds have high viability (> 80%) and no primary dormancy. Together these factors indicate that seed longevity is likely to be on the order of 2 to 3 yr, suggesting that a short, intensive management program that successfully prevents seed production should greatly reduce or eliminate infestations. However, in disturbed areas and along transportation corridors the risk of recontamination is high; continued monitoring to identify new populations is advised in these situations. The base temperature for germination is moderate: 6.5 C and 4 C in the two populations examined, and seeds will germinate with temperatures up to 34 C as long as sufficient moisture is available. This temperature flexibility combined with the dependence on seasonal precipitation makes seed germination very opportunistic, such that emergence timing is year-specific. Preemergent control, therefore, requires careful planning with a high level of context specificity.

Effective control techniques for pale swallowwort (PSW), an invasive herbaceous vine of old fields and forest understories, are limited. We conducted a 3-yr cutting and herbicide study on an adjacent old-field and forest understory site near Ithaca, NY, for control of PSW. Plants in experimental plots were cut in early July and cut again or sprayed in late August for two seasons with the isopropylamine salt of glyphosate , or one of two rates (low or high) of either triclopyr triethylamine salt (i.e., SL, SH) or triclopyr butoxyethyl ester (EL, EH). The herbicide treatments were effective in reducing PSW cover, plant (stem) density, and aboveground biomass in the old-field site, but in several cases, only after 2 yr of cutting plus herbicide application. Only the cutting plus SH treatment did not reduce PSW cover relative to the unmanaged control in the forest understory and no treatment reduced biomass. In general, the cutting plus EH treatment was most effective in reducing PSW stem densities in the forest site. The most effective herbicide treatments differed between sites. Cutting plus EH reduced PSW cover by 84% and stem density (> 5 cm) by 86% in the old-field site. Cutting plus SH effectively decreased long and short (≤ 5 cm) stem densities by 86 and 96%, respectively. Cutting plants twice during each of two seasons increased PSW cover by 301% and density of stems > 5 cm by 73% at this site. In the forest site, cutting plus glyphosate, or cutting plus EH or cutting plus SL and EL resulted in the greatest reductions in PSW cover (80, 76, 66, and 56%, respectively). Cover in plots cut twice per year decreased by 19%. The EH or SL treatments decreased long-stem densities by 78 and 71%, respectively. The EH treatment decreased short-stem density by 37%. These findings suggest that integrated techniques may control PSW but that effective management strategies may be habitat constrained.

Nomenclature: Glyphosate, triclopyr butoxyethyl ester, triclopyr triethylamine salt, pale swallowwort, Vincetoxicum rossicum (Kleopow) Barbar., syn. European swallowwort, Cynanchum rossicum (Kleopow) Borhidi

Management Implications: Pale swallowwort (PSW) is a highly invasive, difficult-to-control herbaceous vine that thrives in old fields but can also establish in shaded forest understories. This study sought to determine the efficacy of integrated management techniques in open-field and forest understory habitats. When PSW is cut in early July and followed in late August by application of an herbicide, the best control is obtained using different herbicides and rates in old-field compared with forest understory habitats. In the old field, two cuttings a year were ineffective and should be avoided. All herbicides reduced PSW cover, stem densities, and shoot biomass in the old field after 2 yr of combined mechanical and chemical treatments. However, cutting plus high rates of triclopyr, either as a triethylamine salt (4.87 kg ae ha⁻¹) or butoxyethyl ester (4.87 kg ae ha⁻¹), provided the best control. The cutting plus glyphosate treatment also provided effective control of PSW, but the cover of other species was significantly lower relative to three of four cutting plus triclopyr treatments. Regardless, it will take longer than two seasons of cutting plus herbicide applications to achieve total control of PSW in this old-field site. In the forest understory site, where PSW density was initially much lower than the old-field site, most cutting plus herbicide treatments were effective in reducing PSW cover. In general, the high rate of the triclopyr butoxyethyl ester formulation provided the best control of PSW, including a reduction in stem densities and increased cover of other species. Cutting PSW twice in each of two growing seasons was also ineffective as a management option in the forest site. Infestations of PSW in old

Soil engineering by downy brome may be a facet of its competitiveness. Using rhizotrons in the greenhouse, we compared the growth and plant–soil relationships of downy brome grown in two field soil types: soil invaded for 12 yr by downy brome and a similar soil not yet invaded. For each soil type, downy brome was grown for two growth cycles. At harvest, root mass and soils were sampled at depths of 10, 40, and 80 cm (4, 16, and 32 in); aboveground biomass was also sampled. After the first growth cycle, downy brome grown in invaded soil had 250% greater aboveground biomass and nearly double the root mass per soil volume at 10 cm relative to downy brome grown in noninvaded soil; root mass per volume was similar at depths of 40 and 80 cm. For the second growth cycle, aboveground biomass declined, but was twice greater for downy brome grown in invaded soil; however, root mass per volume was similar between soil types for each depth. Soil attributes that positively related to aboveground biomass included bicarbonate-extractable P, DTPA (diethylentriamene pentaacetate)-extractable Mn, and solution-phase (80-cm depth). We conclude that the data support our hypothesis that downy brome has engineered the soil to increase its growth potential, but proof will require a more robust experimental design. Plant competition is affected by myriad interactions; however, a plant that can increase the availability of soil nutrients for itself and its growth potential, relative to competing plants, would appear to be at an advantage. The mechanistic underpinnings involved are inconclusive, but may involve increased availability of soil N, P, and Mn.

Nomenclature: Downy brome, Bromus tectorum L

Management Implications: In the ecosystem studied, our data suggest 12 yr of invasion by downy brome has engineered the soil to facilitate its growth. Mechanistic underpinnings of this positive feedback are possibly due to an increase in soil N, P, and Mn availability. The literature is clear: downy brome benefits and becomes more competitive when provided elevated sources of nutrients, particularly N and P. Given that this is a case study, spatial extrapolation is limited; however, by its ability to increase soil nutrient availability, one can expect downy brome to potentially invade communities thought somewhat resistant to invasion owing to inherently low soil nutrient availability.

Throughout the world, the invasion of nonnative plants is an increasing threat to native biodiversity and ecosystem sustainability. Invasion is especially prevalent in areas affected by land transformation and disturbance. Surface mines are a major land transformation, and thus may promote the establishment and persistence of invasive plant communities. Using the Shale Hills region of Alabama as a case study, we assessed the use of landscape characteristics in predicting the probability of occurrence of six invasive plant species: sericea lespedeza, Japanese honeysuckle, Chinese privet, autumn-olive, royal paulownia, and sawtooth oak. Models were generated for invasive species occurrence using logistic regression and maximum entropy methods. The predicted probabilities of species occurrence were applied to the mined landscape to assess the probable prevalence of each species across the landscape. Japanese honeysuckle had the highest probable prevalence on the landscape (48% of the area), with royal paulownia having the lowest (less than 1%). Overall, 67% of the landscape was predicted to have at least one invasive plant species, with 20% of the landscape predicted to have two or more species, and 3% of the landscape predicted to have three or more species. Japanese honeysuckle, sericea lespedeza, privet, and autumn-olive showed higher occurrence on the reclaimed sites than across the broader region. We found that geospatial modeling of these invasive plants at this scale offered potential for management, both for identifying habitat types at risk and areas that need management attention. However, the most immediate action for reducing the prevalence of invasive plants on reclaimed mines is to remove invasive plants from the reclamation planting list. Three (sericea lespedeza, autumn-olive, and sawtooth oak) out of the six most common invasive plants in this study were planted as part of reclamation activities.

Nomenclature: Autumn-olive, Elaeagnus umbellata Thunb., Chinese privet, Ligustrum sinense Lour., Japanese honeysuckle, Lonicera japonica Thunb., royal paulownia, Paulownia tomentosa (Thunb.) Sieb. & Zucc. ex Steud., sawtooth oak, Quercus acutissima Carruthers, sericea lespedeza, Lespedeza cuneata (Dumont) G. Don

Management Implications: Geospatial modeling of the invasive plants studied, at this project scale, is useful and offers the potential for management both in terms of identifying habitat types most at risk and identifying areas that need management attention. At an individual species level we did not determine the need for strong active management for Japanese honeysuckle (ubiquitous), or royal paulownia (very low prevalence), both volunteer species. The only species not planted for which we suggest active management is Chinese privet. This species is considered to be the second most abundant invasive plant in the South and possibly the most detrimental. We would suggest that privet is of management concern in the Shale Hills region (SHR) given its potential distribution, and that as forest regenerates that it would be advisable to manage for privet, particularly in the depressions and low-lying areas that are more hydric and closer to water. The most immediate action for reducing the prevalence of invasive plants on reclaimed mines would be to remove invasive plants from the reclamation planting list. Three out of the six most common invasive plants have been planted as part of reclamation activities. For the planted species, sericea lespedeza was the most prevalent; however, it may be competitively excluded as forest reestablishes. For the management of this species, increased canopy cover with a diverse forest structure seems to be the best long-term approach, but the best management practice to assist in eliminating this species from the reclaimed sites would be to remove it from allow

English ivy (Hedera helix) is an evergreen, perennial vine that was introduced from Europe and Asia and is not endemic in much of the United States. English ivy can be invasive and difficult to control once established. Four similar, but not identical, experiments were conducted in sequence to evaluate selected, POST-applied herbicides for English ivy control. English ivy plants were propagated from cuttings and container-grown to obtain a large population of uniform plants. Aminopyralid and fluroxypyr applied at 1.34 and 0.71 kg ae ha⁻¹, which is more twice the maximum registered rate for either herbicide, were ineffective. Glyphosate and 2,4-D amine were generally more effective, but neither herbicide provided a level of control that could be deemed consistently acceptable. Glyphosate applied at 8.51 kg ae ha⁻¹ (the highest rate evaluated) provided 69, 98, and 89% control in the second, third, and fourth experiments as determined by foliage fresh-weight reduction relative to a nontreated control. Treatment with 2,4-D at 5.60 kg ae ha⁻¹ (the highest rate evaluated) controlled English ivy 28, 98, and 89% in the second, third, and fourth experiments, respectively. Mixtures of 2,4-D and glyphosate were generally no more effective than were the components applied alone. Metsulfuron was the most effective herbicide. Metsulfuron applied at 0.168 kg ai ha⁻¹ controlled English ivy ≥ 97% across the three experiments in which this treatment was included. This treatment also prevented regrowth.

Nomenclature: 2,4-D, aminopyralid, fluroxypyr, glyphosate, metsulfuron, sulfometuron, English ivy, Hedera helix L

Management Implications: English ivy was first introduced into North America centuries ago in the colonial period. This species has been widely planted as an ornamental ground cover, but it can be invasive and difficult to control once established. Herbicide-based control has traditionally been only marginally effective, and eradication was never attainable. Six herbicides, plus two herbicide combinations were evaluated for English ivy control. Surprisingly, two relatively new pyridine herbicides that are used for the control of noxious and invasive species in pastures and rangelands, i.e., aminopyralid and fluroxypyr, were less effective than either glyphosate or 2,4-D. The sulfonylurea herbicides metsulfuron and sulfometuron were also evaluated. Metsulfuron was more effective than sulfometuron and was also more effective than either glyphosate or 2,4-D. Metsulfuron applied at 0.168 kg ai ha⁻¹ consistently provided ≥ 97% control, as measured by foliage fresh-weight reduction, and prevented any regrowth. Metsulfuron may have potential for English ivy control and eradication.

Exotic plants have the ability to modify soil seed banks in habitats they invade, but little is known about the legacy of invasion on seed banks once an exotic plant has successfully been controlled. Natural areas previously invaded by leafy spurge in the northern Great Plains typically have one of two fates following its removal: a return of native plants, or a secondary invasion of other exotic plants. It is unknown, however, if this difference in plant communities following leafy spurge control is due to seed bank differences. To answer this question, we monitored seed banks and standing vegetation for 2 yr in mixed-grass prairies that were previously invaded by leafy spurge but controlled within 5 yr of our study. We found that native plant seed banks were largely intact in areas previously invaded by leafy spurge, regardless of the current living plant community, and leafy spurge invasion history had a larger impact on cover and diversity of the vegetation than on the seed banks. Differences in plant communities following leafy spurge control do not appear to be related to the seed banks, and soil conditions may be more important in determining trajectories of these postinvasion communities.

Nomenclature: Leafy spurge, Euphorbia esula L. EPHES

Management Implications: Leafy spurge is an invasive exotic plant of great concern in the northern Great Plains. Control efforts have been successful in recent years, but previously invaded areas either experience a return of native plants (a desirable outcome), or a secondary invasion of other exotic plants (an undesirable outcome). Little is known about the impact of leafy spurge invasion on seed banks, and if seed banks differ between areas with varying invasion histories and vegetation trajectories following leafy spurge control. Our investigation of these seed banks revealed that native species were common in the seed banks of all invasion histories, and that the seed banks were not significantly different among invasion histories and vegetation trajectories. These differences did not appear to be a reflection of the current standing vegetation, but rather resulted either from seeds that arrived at the soil before the invasion, or that were dispersed to invaded sites from nearby native-dominated areas. We conclude that native plant restoration in areas previously invaded by leafy spurge is probably not hindered by the seed banks, and that seed banks appear to be relatively resilient after leafy spurge invasion and control. However, the ubiquitous presence of the aggressively invasive grasses smooth brome and Kentucky bluegrass may necessitate active restoration efforts that simultaneously reduce invasive grass presence and promote native plant recruitment. Additional experimentation would help determine if popular management methods, such as seed addition, are effective in achieving these restoration goals in habitats that already have intact native seed banks.

We assessed pre- and posteradication nitrogen and phosphorus dynamics in longleaf pine sandhill stands severely affected by cogongrass. Across a 7-yr posteradication (glyphosate imazapyr) “recovery chronosequence,” which included untreated cogongrass, uninvaded reference, and treated plots, we analyzed soils for total N, potentially available P (Mehlich-1 [M1]), pH, and organic matter content. We also used resin bags to assess fluxes of plant available N and P in the soil solution. Additionally, we used litterbags to monitor the decomposition and nutrient mineralization patterns of dead rhizome and foliage tissue. Our results indicate similar total N and M1-P contents in both cogongrass-invaded and uninvaded reference plots, with levels of M1-P being lower than in cogongrass plots for 5 yr after eradication. Soil organic matter did not differ between treatments. Resin bag analyses suggest that cogongrass invasion did not affect soil nitrate availability, although a pulse of NO₂ NO₃ occurred in the first 3 yr after eradication. No such trends were observed for ammonium. Resin-adsorbed PO₄ was lowest 3 yr after eradication, and pH was highest 5 yr after eradication. Our litterbag study showed that approximately 55% of foliar biomass and 23% of rhizome tissue biomass remained 18 mo after herbicide treatment. Substantial N immobilization was observed in rhizomes for the first 12 mo, with slow mineralization occurring thereafter. Rapid P mineralization occurred, with 15.4 and 20.5% of initial P remaining after 18 mo in rhizomes and foliage, respectively. Overall, our findings indicate that cogongrass invasion has little to no effect on soil nutrient cycling processes, although some significant—but ephemeral—alterations develop after eradication.

Nomenclature: Glyphosate, imazapyr, cogongrass, Imperata cylindrica (L.) Beauv. IMCY, longleaf pine, Pinus palustris Mill

Management Implications: An improved understanding of how invasive alien plant species alter soil properties and of how novel soil properties persist after eradication is essential for practitioners to develop effective restoration strategies for invaded natural communities. Toward these ends, we undertook this study to assess nutrient dynamics in forest stands affected by cogongrass—an invasive alien plant that affects tropical and subtropical ecosystems on six continents. We chose a longleaf pine sandhill ecosystem as the study site because these forests are frequently targeted in restoration efforts and are commonly invaded by cogongrass in the southeastern United States. Because nitrogen (N) and/or phosphorus (P) availability often affect plant establishment after disturbance, we focused on processes that affect N/P availability and uptake. Our results indicate that cogongrass invasion does not substantially alter soil properties. This is intriguing, given that this species is known to be a superior competitor for belowground resources and often forms dense, single-species stands in longleaf pine ecosystems. The decomposition of cogongrass biomass after herbicide treatment resulted in a rapid pulse of P into the soil and the temporary immobilization of soil N. All measured soil properties (N, P, pH, organic matter), however, returned to a preinvasion state within 5 yr. These results suggest that long-term posteradication soil “legacy” effects, which have been observed with other invasive alien plant species (e.g., alterations to the nitrogen cycle and other biogeochemical cycles), might not occur in cogongrass-affected pine ecosystems—at least those that have been invaded for a relatively short period of time. In light of these findings, we see little evidence to indicate that altered soil properties would impede groundcover restoration efforts in sites that have been invaded by cogongrass for 1–2 yr, as long as practitioners give the soi

To investigate the impacts of long-term targeted invasive plant stewardship projects on students' subsequent stewardship attitudes, an experiment using pre and post-tests to understand program effects and using post-test only comparisons to understand school effects was conducted. The resulting scores from two science classes that participated in year-long invasive plant and restoration activities were compared with those from three comparable classes at a linked school that did not participate in any of these activities. Students in the experimental classes showed overall significantly higher scores compared with the control classes. These attitude scores were then divided into two indexes: sense of personal effectiveness and attitudes of caring for particular places. Students in the experimental group showed increases in both, as compared with the controls. Parent and student focus groups were conducted at the end of the academic year. The resulting comments provide evidence for actual behavior change outside of the school environment. Analysis showed that any student, especially those in the control classes in the traditional middle school, indicating they had prior exposure to nature stewardship projects showed significantly higher scores than students who did not. The results underscore the value of having students involved in real-world stewardship projects, especially those of a long-term nature.

Management Implications: English ivy (Hedera helix) is a pervasive invasive plant growing in parks and greenspaces in many urban areas. This plant is frequently the target of public and school invasive plant removal events. If the management goal is removal, chemical treatment may be more effective. However, if the management goal is greater public awareness about invasive plants, a targeted community-based education and stewardship approach may be effective. By involving an interested teacher, students can be involved in long-term experiences that both inform and involve them directly in work that has credible, beneficial real-world outcomes. Students in the experimental group of this study were highly motivated and continued to both inform and inspire their families to help remove invasive species outside of school in their own communities. In addition, they informed their families and friends about the work they had done removing invasive species in local parks and took them there to show off their results. Agencies can work with schools using long-term stewardship projects in effective strategies that increase awareness and motivation in students and lead to community-wide effects.

Desert grasslands of the southwestern United States have experienced an increase in the abundance and distribution of woody plant species over the past century. Shrub encroachment has caused a substantial loss of grasslands in the northern Chihuahuan Desert. The Chihuahuan Desert has also been invaded by Lehmann lovegrass, a fire-adapted species from southern Africa. In 1999, the U.S. Department of Agriculture–Agricultural Research Service burned a remnant desert grassland to determine the effects of prescribed fire on shrub–perennial grass dynamics. The grassland also contained the nonnative perennial grass Lehmann lovegrass. I am reporting on a study that was initiated to determine whether prescribed burning would alter the vegetative community within and proximal to a Lehmann lovegrass–dominated patch. Cover of Lehmann lovegrass showed no significant response to the burn treatment. Of the dominant native species, only black grama and broom snakeweed had a significant year by treatment interaction. No species or growth form had a significant vegetation type by year by treatment interaction. After 6 yr, differences between burned and unburned transects were not significant for any species or growth form.

Nomenclature: Lehmann lovegrass, Eragrostis lehmanniana Nees, black grama, Bouteloua eriopoda (Torr.) Torr., broom snakeweed, Gutierrezia sarothrae (Pursh) Britt. & Rusby