Control of <Emphasis Type="Italic">Lepidium latifolium</Emphasis> (perennial pepperweed) and recovery of native plants in tidal marshes of the San Francisco Estuary

Several management techniques are effective in controlling Lepidium latifolium (perennial pepperweed) in rangelands and hay meadows; however, this invader’s rapid spread into sensitive aquatic habitats throughout the western US calls for alternative control strategies. To evaluate control methods for use in tidal marshes of San Francisco Estuary, we tested chemical, mechanical, and biological methods in field and greenhouse experiments. In a field experiment in three brackish marshes spanning the estuary, application of the herbicide glyphosate to re-growth of L. latifolium following hand-removal reduced L. latifolium cover by an average of 80% after 2 years and led to a 60% increase in native vegetation cover. Glyphosate alone was less effective at reducing L. latifolium cover (20% decrease) and increasing native cover (34% increase). Preliminary tests of a potential biological control, a native parasitic plant, were not successful, thus plots intended for field trials were instead used to test the newly approved herbicide imazapyr, which showed promise in controlling L. latifolium. An additional greenhouse experiment found large reductions in stem lengths with either glyphosate following clipping or imazapyr with or without clipping, all significantly more so than glyphosate alone. We conclude that an integrated management approach of applying glyphosate following mechanical removal can be effective at reducing L. latifolium cover and allowing recovery of native tidal marsh plants, providing a useful solution for controlling smaller, accessible infestations of the invader. Our preliminary tests of imazapyr suggest that it may be very effective at controlling L. latifolium in tidal marshes, although further assessment of non-target effects and native plant recovery are needed to evaluate its relative merit.     

Seasonal Effects of Four Control Methods on the Invasive Morrow's Honeysuckle (Lonicera morrowii) and Initial Responses of Understory Plants in a Southwestern Pennsylvania Old Field

The first step in restoration often involves the removal of invasive plants, but few studies have determined if the response of plant communities matches management goals. The shrub Morrow's honeysuckle ( Lonicera morrowii Gray) is one of a suite of exotic bush honeysuckle species that have become pervasive woody invaders in eastern North America. In 2004, we tested four control methods (cut, mechanical removal, stump application of glyphosate, and foliar application of glyphosate) during late spring and early autumn within a degraded meadow at Fort Necessity National Battlefield, Pennsylvania, U.S.A. Our restoration goals are to control Morrow's honeysuckle, restore native vegetation, and mimic the conditions present in the mid-1700s. We established forty-five 5 × 5–m plots to measure woody species; five plots of each treatment method were treated in spring, whereas the remaining five were treated in autumn. We maintained five control plots. Before control, mean density of Morrow's honeysuckle was 67,920 ± 4,480 shrubs/ha. Foliar application of herbicide and mechanical removal were most effective at reducing the number of shrubs (≥62%). Overall, our treatments were less successful (26–68% reduction) than reported control efforts of other bush honeysuckle species; the sheer number of shrubs coupled with their open habitat made control efforts difficult. Spring treatments, particularly cut and mechanical treatments, had higher metrics of herbaceous community quality. However, continued restoration efforts, including follow-up treatments, White-tailed deer ( Odocoileus virginianus ) control, and the planting of native seeds and saplings, should be employed to favor the establishment of native seedlings and herbs.     

Efficacy of Imazapyr and Glyphosate in the Control of Non-Native Phragmites australis

The cosmopolitan common reed ( Phragmites australis ) has been expanding into previously unoccupied wetland habitats throughout North America. This invasion by a non-native haplotype of Phragmites has become a major concern due to a reduction in plant diversity, reduction of faunal biodiversity, and changes in ecosystem structure. A randomized complete block design was used to compare the efficacy of two herbicides, glyphosate (Rodeo, Dow AgroSciences, IN, U.S.A.) and imazapyr (Habitat, BASF Corporation, NC, U.S.A.), on 1-ha Phragmites monoculture in a shallow borrow pit. Six foliar experimental treatments were applied consisting of (1) 2% glyphosate formulation, June application; (2) 2% glyphosate formulation, September application; (3) 2% imazapyr formulation, June application; (4) 2% imazapyr formulation, September application; (5) 5% imazapyr formulation, June application; and (6) 5% imazapyr, September application. Experimental plots were monitored yearly for two years after treatment. Relative importance values (RIV) were determined to assess the efficacy of herbicide treatments. We report that imazapyr foliar application is statistically superior to glyphosate in reducing Phragmites RIV, with no significant differences between the 2 and 5% formulations. Both herbicides are more effective in reducing Phragmites RIV if applied early in the growing season (June). No significant differences in non- Phragmites plant recolonization were observed between herbicide treatments over the two-year time course. These results suggest that imazapyr is superior in reducing Phragmites RIV, and that earlier applications of herbicides may be more effective on Phragmites . However, managers must note that adjacent nontarget plant species may be negatively affected by earlier treatments.     

Invasive Phragmites australis management outcomes and native plant recovery are context dependent

The outcomes of invasive plant removal efforts are influenced by management decisions, but are also contingent on the uncontrolled spatial and temporal context of management areas. Phragmites australis is an aggressive invader that is intensively managed in wetlands across North America. Treatment options have been understudied, and the ecological contingencies of management outcomes are poorly understood. We implemented a 5‐year, multi‐site experiment to evaluate six Phragmites management treatments that varied timing (summer or fall) and types of herbicide (glyphosate or imazapyr) along with mowing, plus a nonherbicide solarization treatment. We evaluated treatments for their influence on Phragmites and native plant cover and Phragmites inflorescence production. We assessed plant community trajectories and outcomes in the context of environmental factors. The summer mow, fall glyphosate spray treatment resulted in low Phragmites cover, high inflorescence reduction, and provided the best conditions for native plant recruitment. However, returning plant communities did not resemble reference sites, which were dominated by ecologically important perennial graminoids. Native plant recovery following initial Phragmites treatments was likely limited by the dense litter that resulted from mowing. After 5 years, Phragmites mortality and native plant recovery were highly variable across sites as driven by hydrology. Plots with higher soil moisture had greater reduction in Phragmites cover and more robust recruitment of natives compared with low moisture plots. This moisture effect may limit management options in semiarid regions vulnerable to water scarcity. We demonstrate the importance of replicating invasive species management experiments across sites so the contingencies of successes and failures can be better understood.     

Responses of invertebrates to herbicide in Salix cinerea invaded wetlands: Restoration implications

The use of herbicides to control weeds, particularly large invasions, has now become an essential management tool in many ecological restoration projects. The herbicide glyphosate is routinely used to control the invasive weed, Grey Willow (Salix cinerea), within New Zealand wetlands. However, little is known about the effects of glyphosate on invertebrates. We determine the short‐term effects of glyphosate on the abundance and composition of the nontarget canopy invertebrate community in wetlands invaded by Grey Willow in New Zealand. Initially, the application of glyphosate and a surfactant showed no detectable effect on the canopy invertebrates examined in this study. However, 27 days after herbicide application, significant Grey Willow canopy loss caused dramatic decreases in the abundance of invertebrates in the glyphosate‐treated plots compared with the unsprayed plots. Invertebrates appeared to be sensitive to changes in vegetation structure, such as canopy loss. These results agree with previous studies that have shown that the negative impacts of glyphosate on invertebrate communities are related to indirect effects via habitat modification as the herbicide‐treated vegetation dies. From a terrestrial invertebrate perspective, this study suggests that the use of glyphosate herbicide is suitable for the control of invasive weeds within wetland restoration projects as it appears to have negligible impact on the canopy invertebrate assemblage.     

Integrating revegetation with management methods to rehabilitate coastal vegetation invaded by Bitou bush (Chrysanthemoides monilifera ssp. rotundata) in Australia

Two multi‐year field experiments investigated the effects of integrating revegetation with invasive plant management methods to rehabilitate coastal dune and woodland vegetation invaded by Bitou bush (Chrysanthemoides monilifera (L.) Norl. ssp. rotundata (DC.) Norl.) in New South Wales, Australia. The revegetation technique used was to sow directly seeds of three native species common to coastal habitats. Management treatments involved combinations of prescribed fire, manual removal of Bitou bush and an application of herbicide. Addition of native seeds significantly increased density of native species in both habitats. The benefits of manually removing Bitou bush were observed only where densities of native species were at their lowest. Fire increased densities of some native species in the woodland, but decreased those of others in the dune. Densities of Acacia longifolia ssp. sophorae (Labill.) Court (woodland) and of Banksia integrifolia L.f. (woodland and dune) were significantly reduced within 4 months of herbicide application, alone or in combination with other treatments. The majority of these effects, however, did not persist. Manual removal in both habitats and addition of seed in the woodland were most effective in reducing Bitou bush densities when applied post‐fire. Herbicide treatment on its own or in combination with other treatments did not significantly reduce Bitou bush densities by the end of the experiments. We conclude that restoration of coastal ecosystems invaded by a major invasive plant species requires a whole‐of‐system approach involving revegetation in combination with known management methods to assist recovery of native species in the longer term.     

Herbicide and Tillage Effects on Volunteer Vegetation Composition and Diversity During Reforestation

Fraxinus pennsylvanica (green ash) is commonly used for reforestation of agricultural lowlands in the midwestern and eastern United States. We evaluated the effects of herbicide (untreated, glyphosate, and sulfometuron methyl) and tillage (tilled and no‐till) on F. pennsylvanica success and composition of associated volunteer vegetation 3 years after the treatment applications and reforestation of a formerly cultivated field in southern Illinois. Tillage had no effect on F. pennsylvanica growth, whereas both herbicides increased all measures of tree performance. The response of associated native and non‐native species cover was affected by an interaction between the herbicide and tillage treatments. In the presence of herbicide, cover of native species was greater in the no‐till treatment, whereas non‐native cover was higher in the tillage treatment. Both native and non‐native cover were unaffected by tillage in the absence of herbicide, and there were no differences in cover among the herbicide treatments in the presence of tillage. Total diversity was higher in the tillage treatment than the no‐till treatment, and diversity was lower in the sulfometuron methyl herbicide treatment than the control and glyphosate herbicide treatment. Lower diversity in the sulfometuron methyl treatment was attributed to greater cover of a native perennial grass, Andropogon virginicus (Broomsedge), which was inversely related to total diversity. We conclude that a single glyphosate herbicide application can enhance F. pennsylvanica growth and conserve associated species diversity in this system. Furthermore, species‐specific responses of the associated vegetation should be included in management considerations, particularly if silvicultural treatments influence dominance and diversity in the establishing understory community during reforestation.     

Prescribed Fire and Herbicide Effects on Soil Processes During Barrens Restoration

Prescribed fire has become a common tool of natural area managers for removal of non‐indigenous invasive species and maintenance of barrens plant communities. Certain non‐native species, such as tall fescue (Festuca arundinacea), tolerate fire and may require additional removal treatments. We studied changes in soil N and C dynamics after prescribed fire and herbicide application in remnant barrens in west central Kentucky. The effects of a single spring burn post‐emergence herbicide, combined fire and herbicide treatments, and an unburned no‐herbicide control were compared on five replicate blocks. In fire‐plus‐herbicide plots, fescue averaged 8% at the end of the growing season compared with 46% fescue cover in control plots. The extent of bare soil increased from near 0 in control to 11% in burned plots and 25% in fire‐plus‐herbicide plots. Over the course of the growing season, fire had little effect on soil N pools or processes. Fire caused a decline in soil CO₂ flux in parallel to decreased soil moisture. When applied alone, herbicide increased plant‐available soil N slightly but had no effect on soil respiration, moisture, or temperature. Fire‐plus‐herbicide significantly increased plant‐available soil N and net N transformation rates; soil respiration declined by 33%. Removal of non‐native plants modified the chemical, physical, and biological soil conditions that control availability of plant nutrients and influence plant species performance and community composition.     

Effects of Initial Site Treatments on Early Growth and Three-Year Survival of Idaho Fescue

Prairies in the Pacific Northwest have been actively restored for over a decade. Competition from non‐native woody and herbaceous species has been presumed to be a major cause for the failure of restoration projects. In this research, plugs of the native prairie bunchgrass, Festuca idahoensis Elmer var. roemeri (Pavlick), were grown from seed in a nursery and transplanted into a grassland site dominated by non‐native pasture grasses. The growth of the plants was followed for three years, and biomass of all volunteer plants was measured. Before planting, five treatments were applied to the plots: removal of vegetation by burning, removal of vegetation by an herbicide‐and‐till procedure, soil impoverishment by removal of organic matter, fertilizer application, and compost mulch application. Initial growth of Idaho fescue plugs was greatest with fertilizer and compost mulch. Plants grown in mulched plots were also able to photosynthesize later into the dry summer season. After the first year, plots initially fertilized or composted had the lowest survival rate of Idaho fescue. Impoverished and herbicide‐and‐till plots had the greatest 3‐year survival. Mulched plots supported the greatest weed growth after three years. Stressful environments give a competitive advantage to Idaho fescue in prairie restoration projects. As weedy species increase, growth and survival of Idaho fescue decreases.     

Restoration of Arthropod Assemblages in a Spartina Salt Marsh following Removal of the Invasive Plant Phragmites australis

Invasive plants are one of the most serious threats to native species assemblages and have been responsible for the degradation of natural habitats worldwide. As a result, removal of invasive species and reestablishment of natural vegetation have been attempted in order to restore biodiversity and ecosystem function. This study examined how native arthropod assemblages, an abundant and functionally important group of organisms in many ecosystems, are affected by the incursion of the invasive wetland plant Phragmites australis and if the restoration of the native vegetation in brackish Spartina alterniflora marshes results in the reestablishment of the arthropod community. The invasion of Phragmites into a coastal Spartina marsh in southern New Jersey seriously altered arthropod assemblages and trophic structure by changing the abundance of trophic groups (detritivores, herbivores, carnivores) and their taxonomic composition. Herbivore assemblages shifted from the dominance of external free‐living specialists (e.g., planthoppers) in Spartina to concealed feeders in Phragmites (stem‐feeding cecidomyiids). Moreover, free‐living arthropods in Phragmites became dominated by detritivores such as Collembola and chironomids. The dominant marsh spiders, web‐building linyphiids, were significantly reduced in Phragmites habitats, likely caused by differences in the physical environment of the invaded habitats (e.g., lower stem densities). Thus, trophic structure of arthropod assemblages in Phragmites, as seen in the large shifts in feeding guilds, was significantly different from that in Spartina. Removal of Phragmites with the herbicide glyphosate resulted in the rapid return of Spartina (≤5 yrs). Moreover, return of the dominant vegetation was accompanied by the recovery of most original habitat characteristics (e.g., live and dead plant biomass, water flow rate). The arthropod assemblage associated with Spartina also quickly returned to its preinvasion state and was not distinguishable from that in uninvaded Spartina reference sites. This study provides evidence that the reestablishment of native vegetation in areas previously altered by an invasive plant can result in the rapid recovery of the native arthropod assemblage associated with the restored habitat.     

Effects of different Rhododendron control methods in eastern beech (Fagus orientalis Lipsky) ecosystems in the western Black Sea region of Turkey

Intensive weed control and plot preparation practices have become a critical and integral part of productive beech forest management in Turkey’s coastal Black Sea region (BSR). This study was conducted in an eastern beech forest of 100+ year old in the BSR to evaluate ecosystem effects of three different experimental Rhododendron ponticum understory control methods with a randomised block design, including manual grubbing, foliar and cut stump spraying with imazapyr (Arsenal) and foliar and cut stump spraying with triclopyr (Garlon). Untreated vegetation plots served as controls. Evaluation of these treatments included their effects on understory and forest floor biomass and nutrients (C, N, P, S, K, Ca and Mg) and effects on soils, including bulk density, pH, soil nutrients (C, N, P and S), exchangeable cations (K, Ca and Mg) and soil cation exchange capacity (CEC). Grubbing and imazapyr treatments had greatly reduced the amount of understory biomass 5 years after application (P = 0.002). Triclopyr treatment also had a major effect on understory vegetation control, but by 5 years later, about 10% of the rhododendron originally present on these plots had gradually re‐sprouted and partially covered the plots. Five years after woody vegetation control treatments, at the 0‐ to 20‐cm depth, treatments did not appear to affect soil bulk density, pH and CEC. For the upper 20‐cm soil depth, the exchangeable soil K concentration at the 10‐ to 20‐cm depth on triclopyr‐treated plots was 33% higher than on grubbing plots, and it was twice that of imazapyr application plots. Imazapyr plots had almost 11 times more dead organic matter on the forest floor than there was on grubbing plots. Forest floor C concentrations on imazapyr plots were 26 and 14% greater than those on grubbing and triclopyr plots, respectively. Total ecosystem (forest floor + understory + soil exchangeable) Ca content was 50% higher on imazapyr plots than that on triclopyr plots, while the ecosystem K pool on imazapyr treatment plots was 27% lower than that on triclopyr plots. Herbicides can be used as an alternative for achieving some forest management objectives when other vegetation control methods are not feasible or economical. It is recommended that vegetation control not be used on steep slopes because of greater risk of soil erosion. There may be benefits in encouraging slash disposal by fire after imazapyr treatments, thus removing recalcitrant understory residues left on the forest floor and releasing the essential nutrients within them.     

Effects of Herbicide on the Invasive Biennial Alliaria petiolata (Garlic Mustard) and Initial Responses of Native Plants in a Southwestern Ohio Forest

Restoration often includes control of invasive plants, but little is known about how native plant communities respond to this control. The biennial Alliaria petiolata (M. Bieb.) Cavara and Grande (garlic mustard) is one of the most prevalent invasive plants in forests of eastern North America. We investigated the effects of the herbicide Round‐up (glyphosate) on Alliaria and the response of the forest floor plant community to the herbicide and the subsequent decline of Alliaria. In an old‐growth Acer–Fagus stand and a second‐growth Liriodendron‐dominated stand in Hueston Woods State Nature Preserve, Ohio, United States, we spot applied Round‐up in November 2000 and 2001 in 25 1 × 1–m plots and maintained 25 control plots. Herbicide decreased Alliaria density in both stands and reduced the density of other species in leaf during treatment (mostly exotic winter annuals) in the old‐growth stand. Treatment did not affect the initial density of the Alliaria cohort that germinated in the spring of 2001, but decreased the 2002 cohort. Community differences were found in the old‐growth stand after Alliaria reduction, specifically greater cover of spring ephemerals in the herbicide treatment. In the second‐growth stand, herbicide treatment increased reproduction of the late‐summer perennial, Phryma leptostachya. These results indicate that glyphosate reduces Alliaria without negatively impacting native species and that some native species respond positively to a single‐year reduction in this invasive biennial.     

Evaluation of perennial pepperweed (Lepidium latifolium) management in a seasonal wetland in the San Francisco Estuary prior to restoration of tidal hydrology

Herbicide applications have shown potential for control and management of invasive perennial pepperweed (Lepidium latifolium) in rangelands and tidal wetlands. However, reported efficacy of management methods varies widely, and the effects of more recently registered aquatic herbicides on non-target vegetation in riparian corridors and seasonal wetlands are poorly understood. In a replicated field experiment, we applied two registered aquatic herbicides to control L. latifolium upstream of a sensitive tidal wetland reserve as a preliminary step towards hydrologic restoration of a degraded ephemeral creek channel and associated seasonal wetlands. Herbicide treatments (imazapyr, 2,4-d) were applied at flower bud stage in May 2007 and monitored at 1 and 2 years following application. Two years of 2,4-d application were not effective in controlling L. latifolium (<1% control) but had minimal non-target impacts on the native plant community. Imazapyr reduced L. latifolium cover by more than 90% after 1 year of treatment as compared to untreated controls although non-target impacts on the native plant community were severe and persistent over the 2 years of observation. These results provide important information about the response of L. latifolium to management trials in a seasonal wetland and will be used to develop an integrated and adaptive management strategy for weed control as a component of a proposed tidal marsh restoration plan.     

Experimental Restoration of Native Vegetation in Indiana Dunes National Lakeshore

We investigated the effects of prescribed fire, herbicide treatment, and sod removal on the eradication of exotic grasses and the establishment of native plant species in 24 experimental restoration plots in three razed residential sites within the boundary of Indiana Dunes National Lakeshore. During 1992–1995, herbicide treatment and sod removal decreased the combined cover of Poa pratensis (Kentucky blue grass) and Agropyron repens (quackgrass) significantly (from 82% to 13%, and 85% to 8%, respectively), whereas fire did not suppress such exotic lawn grasses. In 1993, several opportunistic species, represented by Cyperus spp. (umbrella sedges), Digitaria sanguinalis (crab grass), and Ambrosia artemisiifolia (common ragweed), filled the gaps left by the removal of lawn grasses. For the same period, Detrended Correspondence Analysis revealed a clear vegetation divergence between the control-fire plots and the herbicide-sod removal plots. While Poa pratensis and Agropyron repens continued to dominate the control and fire plots, the planted native species, represented by Schizachyrium scoparium (little blue-stem), Sorghastrum nutans (Indian grass), Rudbeckia hirta (black-eyed Susan), and Monarda punctata (horsemint), began to dominate in the herbicide and sod removal plots from 1994. In both herbicide and sod removal plots, the ground cover of grasses (68%) was much higher than the forbs (10%). The herbicide plots, where exotic species were removed but nitrogen-rich top soils were not removed, showed a higher diversity of planted native species than the sod removal plots (where both exotic species and top soils were removed) and the control-fire plots (where neither was removed). This finding suggests that an optimum but not excessive concentration of soil nitrogen is needed to support a maximum species diversity in such infertile substrate as sandy soil. In addition, the decrease in potassium in all plots, regardless of treatment, suggests that potassium may become a limiting factor for our restored native vegetation.     

Residual herbicide treatments reduce Andropogon gayanus (Gamba Grass) recruitment for mine site restoration in northern Australia

Weed invasion is a major threat to Australian tropical savannas, and controlling weeds is essential for successful re‐establishment of native species on disturbed sites. Gamba Grass (Andropogon gayanus) is an African grass which has invaded large areas of tropical savanna across northern Australia. Current management strategies in northern Australia focus on fire and glyphosate to effectively control mature plants; however, re‐establishment of infestations from the soil seed bank remains a major challenge to eradication efforts. This study focused on the effects of soil seed bank treatments on Gamba Grass recruitment on a mine site in northern Australia. Adult Gamba Grass plants within test plots were killed with glyphosate to exclude resource competition. Chemical, physical and biological treatments were then applied, and the treatment effects on subsequent Gamba Grass seedling emergence and survival quantified. Seedling emergence was significantly reduced by three of the four residual herbicide treatments tested. The most effective herbicide treatments, dalapon and sulfometuron, reduced emergence by 90% compared to the standard glyphosate treatment alone. This equated to a reduction in Gamba Grass seedling emergence from 1 seedling/m² to 1 seedling 10 m^?2, a major improvement for Gamba Grass management. These residual herbicide treatments significantly reduced the population density of Gamba Grass for at least 5 months after emergence. The physical and biological treatments did not have a significant effect on seedling emergence. This significant reduction in Gamba Grass seedling emergence and survival can substantially improve Gamba Grass management. Reducing re‐colonisation from the soil seed bank using residual herbicides provides a valuable management tool for land managers, integrating readily with established strategies for controlling the mature plants.     

Biodiversity impacts of an invasive grass: ant community responses to <Emphasis Type="Italic">Cenchrus ciliaris</Emphasis> in arid Australia

Buffel grass (Cenchrus ciliaris) is a highly invasive species that thrives in semi-arid environments and has the capacity to transform native vegetation outside its native range. However, there is limited information on the effects of buffel grass invasion on native fauna. We used an experimental approach to investigate the impact of buffel grass on the native ant fauna near Alice Springs in semi-arid central Australia. A series of plots where buffel grass was removed and native vegetation had regenerated (B?), paired with adjacent control plots heavily invaded by buffel grass (B+), were used to assess the impact of buffel grass on ant diversity and composition, and on rates of seed dispersal by ants. Differences in ant diversity were also compared between two microhabitat types: bare ground and under cover, to examine the extent to which any impacts were a simple function of change in vegetation cover. Ant abundance and richness were approximately 50 % higher in B? compared with B+ plots, and higher abundance was especially pronounced for the very thermophilic Hot-Climate Specialists. Ant species composition varied significantly between plot types. B? plots supported more species and individuals in both bare and covered microhabitats, which suggests that the differences in ant diversity was not simply through changes in vegetation cover. Rates of seed removal by ants were marginally higher in B? plots. Our findings indicate that buffel grass has a major impact on a dominant faunal group of arid Australia, and possibly reduces the delivery of an important ecosystem service. In addition, our study demonstrates the potential for ecosystem recovery following effective buffel grass management.     

Longleaf Pine (Pinus palustris P. Mill.) Restoration Using Herbicides: Overstory and Understory Vegetation Responses on a Coastal Plain Flatwoods Site in Florida,U.S.A.

A study was conducted on a Coastal Plain flatwoods site in Florida to determine the effects of common forestry herbicides on Longleaf pine seedling survival and growth and on the understory vegetation. Following removal of the overstory slash pine, five low‐rate herbicide treatments were applied over the top of planted Longleaf pine seedlings to provide short‐term understory vegetation control and accelerate seedling growth. The objective was to increase Longleaf pine growth by reducing the shrub competition while increasing the herbaceous ground cover. Despite causing reduction in seedling survival over the control treatment, imazapyr (0.21 ae kg/ha) resulted in the highest seedling growth (height and volume). The significant reduction of shrub cover, density, and height by imazapyr was believed to be responsible for the improved seedling growth in this treatment. Both hexazinone (0.56 ai kg/ha) and sulfometuron methyl (0.26 ai kg/ha) + hexazinone (0.56 ai kg/ha) treatments also reduced cover of Runner oak, a major shrub species, but the response was evident only 8 months after treatment. Although sulfometuron methyl (0.26 ai kg/ha) and sulfometuron methyl + hexazinone treatments did not result in any significant change in overall grass, forb, and shrub cover, both treatments resulted in greater Longleaf pine growth compared to the control. None of the herbicides significantly affected the major understory grasses and forbs. Overall, imazapyr provided the best desired results with significant increase in seedling growth and better control of shrub species with no significant effects on grass and other herbaceous species cover.     

A preliminary assessment of the response of a native reptile assemblage to spot‐spraying invasive Bitou Bush with glyphosate herbicide

During recent work examining the effects of Bitou Bush (Chrysanthemoides monilifera ssp. rotundata) invasion on native reptile assemblages in coastal heathland vegetation in Eastern Australia, unplanned spot‐spraying of glyphosate occurred at some of our experimental sites invaded by Bitou Bush. We used this unexpected herbicide application as an opportunity to provide a preliminary assessment of the short‐term impacts on reptiles of glyphosate spot‐spraying of Bitou Bush. Using an M‐BARCI design, we compared reptile assemblages among uninvaded (reference) sites, invaded (control) sites and invaded and sprayed (impact) sites before and after spraying. We found no significant short‐term (7 – 10 months) differences in reptile abundance, species richness or assemblage composition among invaded, uninvaded and sprayed sites before and after glyphosate application. We cautiously interpret our results to generate a preliminary finding that spot‐spraying of Bitou Bush with glyphosate appears not to have a deleterious effect on reptile assemblages at seven and ten months following herbicide application. While we would not recommend basing management decisions on the outcomes of our study alone, we suggest that our findings can be used to assist in the development of strategic analyses of glyphosate impacts on native flora and fauna.     

Control of Exotic Annual Grasses to Restore Native Forbs in Abandoned Agricultural Land

Exotic annual grasses are a major challenge to successful restoration in temperate and Mediterranean climates. Experiments to restore abandoned agricultural fields from exotic grassland to coastal sage scrub habitat were conducted over two years in southern California, U.S.A. Grass control methods were tested in 5 m² plots using soil and vegetation treatments seeded with a mix of natives. The treatments compared grass‐specific herbicide, mowing, and black plastic winter solarization with disking and a control. In year two, herbicide and mowing treatments were repeated on the first‐year plots, plus new control and solarization plots were added. Treatments were evaluated using percent cover, richness and biomass of native and exotic plants. Disking alone reduced exotic grasses, but solarization was the most effective control in both years even without soil sterilization, and produced the highest cover of natives. Native richness was greatest in solarization and herbicide plots. Herbicide application reduced exotics and increased natives more than disking or mowing, but produced higher exotic forb biomass than solarization in the second year. Mowing reduced grass biomass and cover in both years, but did not improve native establishment more than disking. Solarization was the most effective restoration method, but grass‐specific herbicide may be a valuable addition or alternative. Solarization using black plastic could improve restoration in regions with cool, wet summers or winter growing seasons by managing exotic seedbanks prior to seeding. While solarization may be impractical at very large scales, it will be useful for rapid establishment of annual assemblages on small scales.     

Disturbance-mediated competition: the interacting roles of inundation regime and mechanical and herbicidal control in determining native and invasive plant abundance

Disturbance is a key component of many successful plant invasions. However, interactions among natural and anthropogenic disturbances and effects of these interacting disturbances on invasive plants and desired vegetation are rarely examined. We investigated the effect of anthropogenic disturbance (herbicidal and mechanical) along a natural inundation gradient (20–282 days) on the biomass and resource allocation of the invasive wetland plant, alligator weed (Alternanthera philoxeroides), and two co-occurring competitor plants, the introduced grass, kikuyu (Pennisetum clandestinum), and the native grass, couch (Cynodon dactylon), over a 2-year period. In the absence of additional disturbance, kikuyu biomass was negatively affected, alligator weed biomass was positively affected, and couch biomass was not affected by inundation disturbance. In addition, kikuyu was not affected by the selective removal of alligator weed, while couch increased in wetter habitats where kikuyu was absent due to inundation stress. This suggests that kikuyu is a superior competitor in drier habitats and inundation facilitates the invasion of alligator weed, while couch is an inferior competitor to both kikuyu and alligator weed and is therefore suppressed across its entire niche by these two introduced species. Mowing alone had no effect on the biomass of the species, suggesting the plants are equally tolerant of shoot removal. Selective herbicide reduced alligator weed biomass by 97.5% and the combination of selective herbicide and mowing reduced the biomass of alligator weed significantly more than herbicide alone, by 98.6% compared with un-manipulated controls. To predict community change and prevent sequential exotic plant invasions after weed removal, it is necessary to consider the interacting effects of disturbance and the niche space of invasive species in the local propagule pool.