Impacts of management and antecedent site condition on restoration outcomes in a sand prairie

Landscape context and site history, including antecedent site conditions, may constrain restoration potential despite the efforts of restoration practitioners. However, few experimental studies have investigated the relative importance of antecedent site conditions and the intensity of on‐site management in driving restoration outcomes. We established small‐scale prairie restoration experiments within the Lost Mound Unit of the Upper Mississippi River National Wildlife and Fish Refuge in Illinois, U.S.A. We investigated the effectiveness of two restoration treatments, herbicide application and seeding of native plants, on removal of invasive crown‐vetch (Securigera varia) and recovery of sand prairie plant communities. We replicated treatment plots across 15 locations with three levels of antecedent condition and fire treatment (burned, undegraded; burned, degraded; and unburned, degraded) to determine whether antecedent condition constrained the effectiveness of on‐site restoration. Two years after initial herbicide application crown‐vetch cover was significantly reduced relative to untreated controls. This effect was more pronounced in plots treated twice with herbicide. However, removal of crown‐vetch facilitated invasion by Kentucky bluegrass (Poa pratensis). Addition of native prairie seed had little effect on restoration outcomes, regardless of herbicide application. Native community recovery was greater in plots restored in less degraded locations. Herbicide application tended to increase native species cover, but importantly, this effect was significant only in the least degraded locations. Intensive restoration management conducted in degraded landscapes can result in undesirable outcomes such as secondary species invasion. Reestablishment of native species following restoration is more likely where the surrounding remnant communities are intact.     

Local and landscape correlates of non‐native species invasion in restored wetlands

Vulnerability of natural communities to invasion by non‐native plants has been linked to factors such as recent disturbance and high resource availability, suggesting that recently restored habitats may be especially invasible. Because non‐native plants can interfere with restoration goals, monitoring programs should anticipate which sites are most susceptible to invasion and which species are likely to become problematic at a site. Restored sites of larger area and those with high rates of propagule input should have higher species richness of both natives and non‐natives, leading to a positive correlation between the two. However, in restored wetlands, urbanization, riparian landscape settings, and nitrogen enrichment likely favor non‐native relative to native species. We sampled 28 restored wetlands in Illinois, USA, modeled the responses of native richness, non‐native richness and non‐native cover to local and landscape predictors with linear regression, and modeled the presence/absence of 21 non‐native species with logistic regressions. Unexpectedly, native and non‐native richness were uncorrelated, suggesting different responses to environmental factors. Native richness declined with increasing available soil nitrogen and urbanization in the surrounding landscape. Non‐native richness, the richness of non‐natives relative to natives, and the likelihood of invasion by several individual invasive species decreased with increasing distance from the city of Chicago, likely in response to decreasing non‐native propagule pressure. Total cover of non‐natives, however, as well as cover by non‐native Phalaris arundinacea, increased with nitrogen availability. Our results indicate that although non‐native richness was better predicted by factors related to propagule pressure, non‐native species dominance was more closely related to local abiotic factors. Non‐native richness in restoration sites may be beyond the control of restoration practitioners, and furthermore, may be of limited relevance for conservation goals. In contrast, limiting the relative dominance of non‐natives should be a restoration priority and may be achievable through management of nutrient availability.     

Long‐term effects of prairie restoration on plant community structure and native population dynamics

The key to restoring degraded grassland habitats is identifying feasible and effective techniques to reduce the negative impacts of exotic species and promote self‐sustaining native populations. It is often difficult to extend monitoring of restoration efforts to evaluate long‐term success, but doing so is essential to understanding how initial outcomes change over time. To assess how initial treatment effects persist, we revisited degraded patches of Pacific Northwest prairie habitat 6 years after experimental restoration efforts ceased. We evaluated plant community composition to determine the lasting effects of supplemental native seeding and disturbance treatments (burning, mowing, and herbicide to reduce exotic species). We tracked the persistence of seeded species and measured spread of their populations to evaluate suitability of species for restoration and the ability of the habitat to support native plant populations. We found that plots that received supplemental seeding continued to exhibit higher richness of native species than those left unseeded, and that both seeding and disturbance treatments could positively influence native species abundance over the long term. The initially observed effects of disturbance treatments on reducing exotic grass abundance had diminished, highlighting the importance of long‐term monitoring and ongoing control of exotic species. Nevertheless, these treatments significantly influenced the population trajectories of 4 out of 8 seeded native species. There was evidence of spatial advance of most seeded species. Results from extended monitoring confirm that dispersal limitation of native species and difficulties maintaining the reduction of exotic grasses continue to be major barriers to success in restoration of invaded grasslands.     

Incomplete recovery of plant diversity in restored prairie wetlands on agricultural landscapes

Restoration efforts are being implemented globally to mitigate the degradation and loss of wetland habitat; however, the rate and success of wetland vegetation recovery post‐restoration is highly variable across wetland classes and geographies. Here, we measured the recovery of plant diversity along a chronosequence of restored temporary and seasonal prairie wetlands ranging from 0 to 23 years since restoration, including drained and natural wetlands embedded in agricultural and natural reserve landscapes in central Alberta, Canada. We assessed plant diversity using the following structural indicators: percent cover of hydrophytes, native and non‐native species, species richness, and community composition. Our findings indicate that plant diversity recovered to resemble reference wetlands in agricultural landscapes within 3–5 years of restoration; however, restored wetlands maintained significantly lower species richness and a distinct community composition compared to reference wetlands located within natural reserves. Early establishment of non‐native species during recovery, dispersal limitation, and depauperated native seed bank were probable barriers to complete recovery. Determining the success of vegetation recovery provides important knowledge that can be used to improve restoration strategies, especially considering projected future changes in land use and climate.     

Contrasting effects of plant inter‐ and intraspecific variation on community trait responses to restoration of a sandy grassland ecosystem

Changes in plant community traits along an environmental gradient are caused by interspecific and intraspecific trait variation. However, little is known about the role of interspecific and intraspecific trait variation in plant community responses to the restoration of a sandy grassland ecosystem. We measured five functional traits of 34 species along a restoration gradient of sandy grassland (mobile dune, semi‐fixed dune, fixed dune, and grassland) in Horqin Sand Land, northern China. We examined how community‐level traits varied with habitat changes and soil gradients using both abundance‐weighted and non‐weighted averages of trait values. We quantified the relative contribution of inter‐ and intraspecific trait variation in specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon content (LCC), leaf nitrogen content (LNC), and plant height to the community response to habitat changes in the restoration of sandy grassland. We found that five weighted community‐average traits varied significantly with habitat changes. Along the soil gradient in the restoration of sandy grassland, plant height, SLA, LDMC, and LCC increased, while LNC decreased. For all traits, there was a greater contribution of interspecific variation to community response in regard to habitat changes relative to that of intraspecific variation. The relative contribution of the interspecific variation effect of an abundance‐weighted trait was greater than that of a non‐weighted trait with regard to all traits except LDMC. A community‐level trait response to habitat changes was due largely to species turnover. Though the intraspecific shift plays a small role in community trait response to habitat changes, it has an effect on plant coexistence and the maintenance of herbaceous plants in sandy grassland habitats. The context dependency of positive and negative covariation between inter‐ and intraspecific variation further suggests that both effects of inter‐ and intraspecific variation on a community trait should be considered when understanding a plant community response to environmental changes in sandy grassland ecosystems.     

Variation in the impact of non‐native seaweeds along gradients of habitat degradation: a meta‐analysis and an experimental test

Biological invasions are acknowledged among the main drivers of global changes in biodiversity. Despite compelling evidence of species interactions being strongly regulated by environmental conditions, there is a dearth of studies investigating how the effects of non‐native species vary among areas exposed to different anthropogenic pressures. Focusing on marine macroalgae, we performed a meta‐analysis to test whether and how the direction and magnitude of their effects on resident communities and species varies in relation to cumulative anthropogenic impact levels. The relationship between human impact levels and non‐native species impact intensity emerged only for a reduced subset of the response variables examined. Yet, there was a trend for the effects of non‐native species on community biomass and abundance and on species abundance to become less negative at heavily impacted sites. By contrast, the magnitude of negative effects of seaweed on community evenness tended to increase with human impact levels. The hypothesis of decreasing severity of invader’ impacts along a gradient of habitat degradation was also tested experimentally at a regional scale by comparing the effects of the removal of non‐native alga, Caulerpa cylindracea, on resident assemblages among rocky reefs exposed to different anthropogenic pressures. Assemblages at urban and pristine site did not differ when invaded, but did so when C. cylindracea was removed. Our results suggest that, despite the generally weak relationship between human impacts levels and non‐native species impacts, more negative impacts can be expected in less stressful environments (i.e. less degraded or pristine sites), where competitive interactions are presumably the driving force structuring resident communities. Implementing strategies for controlling the establishment of non‐native seaweeds should be, thus, considered a priority for preserving biodiversity in relatively pristine areas. On the other hand, control of invaders at degraded sites could be warranted to lessen their role as propagule sources. Synthesis Local anthropogenic stressors that severely alter biotic and abiotic conditions may underpin context‐dependency in the impacts of biological invasions. We used a meta‐analysis and an experimental test to examine the relationship between cumulative human impacts and ecological impact of non‐native seaweeds on resident assemblages. Our results suggest that more negative impacts of non‐native seaweeds on the abundance and biomass of resident assemblages can be expected in less degraded or pristine sites. Possibly, stronger impacts prevail at pristine sites, where assemblages are mainly structured by biotic interactions. Hence, management efforts should be mostly directed to prevent the establishment and spread of non‐native seaweeds in pristine areas. On the other hand, weak, but positive effects of seaweeds at the most degraded sites add to the ongoing debate on the role of non‐native species in rehabilitation plans.     

Effect of habitat area and isolation on plant trait distribution in European forests and grasslands

A number of studies show contrasting results in how plant species with specific life‐history strategies respond to fragmentation, but a general analysis on whether traits affect plant species occurrences in relation to habitat area and isolation has not been performed. We used published data from forests and grasslands in north‐central Europe to analyse if there are general patterns of sensitivity to isolation and dependency of area for species using three traits: life‐span, clonality, and seed weight. We show that a larger share of all forest species was affected by habitat isolation and area as compared to grassland species. Persistence‐related traits, life‐span and clonality, were associated to habitat area and the dispersal and recruitment related trait, seed weight, to isolation in both forest and grassland patches. Occurrence of clonal plant species decreased with habitat area, opposite to non‐clonal plant species, and long‐lived plant species decreased with grassland area. The directions of these responses partly challenge some earlier views, suggesting that further decrease in habitat area will lead to a change in plant species community composition, towards relatively fewer clonal and long‐lived plants with large seeds in small forest patches and fewer clonal plants with small seeds in small grassland patches. It is likely that this altered community has been reached in many fragmented European landscapes consisting of small and isolated natural and semi‐natural patches, where many non‐clonal and short‐lived species have already disappeared. Our study based on a large‐scale dataset reveals general and useful insights concerning area and isolation effects on plant species composition that can improve the outcome of conservation and restoration efforts of plant communities in rural landscapes.     

Traits linked with species invasiveness and community invasibility vary with time,stage and indicator of invasion in a long‐term grassland experiment

Much uncertainty remains about traits linked with successful invasion – the establishment and spread of non‐resident species into existing communities. Using a 20‐year experiment, where 50 non‐resident (but mostly native) grassland plant species were sown into savannah plots, we ask how traits linked with invasion depend on invasion stage (establishment, spread), indicator of invasion success (occupancy, relative abundance), time, environmental conditions, propagule rain, and traits of invaders and invaded communities. Trait data for 164 taxa showed that invader occupancy was primarily associated with traits of invaders, traits of recipient communities, and invader‐community interactions. Invader abundance was more strongly associated with community traits (e.g. proportion legume) and trait differences between invaders and the most similar resident species. Annuals and invaders with high‐specific leaf area were only successful early in stand development, whereas invaders with conservative carbon capture strategies persisted long‐term. Our results indicate that invasion is context‐dependent and long‐term experiments are required to comprehensively understand invasions.     

Not all non‐natives are equally unequal: reductions in herbivore β‐diversity depend on phylogenetic similarity to native plant community

Effects of host plant α‐ and β‐diversity often confound studies of herbivore β‐diversity, hindering our ability to predict the full impact of non‐native plants on herbivores. Here, while controlling host plant diversity, we examined variation in herbivore communities between native and non‐native plants, focusing on how plant relatedness and spatial scale alter the result. We found lower absolute magnitudes of β‐diversity among tree species and among sites on non‐natives in all comparisons. However, lower relative β‐diversity only occurred for immature herbivores on phylogenetically distinct non‐natives vs. natives. Locally in that comparison, non‐native gardens had lower host specificity; while among sites, the herbivores supported were a redundant subset of species on natives. Therefore, when phylogenetically distinct non‐natives replace native plants, the community of immature herbivores is likely to be homogenised across landscapes. Differences in communities on closely related non‐natives were subtler, but displayed community shifts and increased generalisation on non‐natives within certain feeding guilds.     

Restoration of Native Warm Season Grassland Species in a Tall Fescue Pasture Using Prescribed Fire and Herbicides

Pastures dominated by tall fescue (Schedonorus phoenix (Scop.) Holub) cover much of the eastern United States, and there are increasing efforts to restore native grassland plant species to some of these areas. Prescribed fire and herbicide are frequently used to limit the growth of tall fescue and other non‐natives, while encouraging native grasses and forbs. A fungal endophyte, commonly present in tall fescue, can confer competitive advantages to the host plant, and may play a role in determining the ability of tall fescue plants to persist in pastures following restoration practices. We compared vegetation composition among four actively restored subunits of a tall fescue pasture (each receiving different combinations of prescribed fire and/or herbicide) and a control. We also measured the rate of endophyte infection in tall fescue present within each restoration treatment and control to determine if restoration resulted in lower tall fescue cover but higher endophyte infection rates (i.e. selected for endophyte‐infected individuals). Tall fescue cover was low in all restoration treatments and the control (1.1–17.9%). The control (unmanaged) had higher species richness than restoration treatments and plant community composition was indicative of succession to forest. Restoration practices resulted in higher cover of native warm season grasses, but in some cases also promoted a different undesirable species. We found no evidence of higher fungal endophyte presence in tall fescue following restoration, as all subunits had low endophyte infection rates (2.2–9.3%). Restoration of tall fescue systems using prescribed fire and herbicide may be used to promote native grassland species.     

Stimulating Natural Regeneration of Tropical Forest on Degraded Land: Approaches,Outcomes, and Information Gaps

Extensive land clearing in many parts of the global tropics is a major threat to biodiversity, and strategies are urgently needed to reinstate forest. Tree planting is a commonly used strategy to rapidly restore forest to degraded landscapes. However, tree planting is expensive, and in most cases financial constraints prevent its use at a scale needed to address the ongoing legacy of land clearing. Here, we conduct a quantitative review of literature from the global tropics and evaluate outcomes of less intensive interventions (i.e. non‐planting) aimed at stimulating natural regeneration of forest. We focus specifically on overcoming barriers to native plant regeneration that predominate in the earliest stages of succession. Common interventions include varied strategies to suppress herbaceous vegetation (e.g. cutting or herbicide treatment), and measures to bolster propagule supply (e.g. direct seeding and artificial bird perches). There was an apparent trend among pair‐wise comparisons of effect sizes to suggest that combined interventions to simultaneously suppress herbaceous vegetation and increase propagule supply resulted in the most consistent outcomes in terms of promoting progress toward restoring forest structure. Despite an obvious demand for lower cost interventions, a paucity of information means that it is still premature to generalize outcomes of specific interventions and their overall cost relative to active tree planting. Nevertheless, we report an increase in research effort in this area, and suggest promising directions to accelerate progress that will improve capacity to select optimal, cost effective strategies that achieve long‐term restoration objectives with a particular level of certainty .     

Native and non‐native grasses generate common types of plant–soil feedbacks by altering soil nutrients and microbial communities

Soil conditioning occurs when plants alter features of their soil environment. When these alterations affect subsequent plant growth, it is a plant soil feedback. Plant–soil feedbacks are an important and understudied aspect of aboveground–belowground linkages in plant ecology that influence plant coexistence, invasion and restoration. Here, we examine plant–soil feedback dynamics of seven co‐occurring native and non‐native grass species to address the questions of how plants modify their soil environment, do those modifications inhibit or favor their own species relative to other species, and do non‐natives exhibit different plant–soil feedback dynamics than natives. We used a two‐phase design, wherein a first generation of plants was grown to induce species‐specific changes in the soil and a second generation of plants was used as a bioassay to determine the effects of those changes. We also used path‐analysis to examine the potential chain of effects of the first generation on soil nutrients and soil microbial composition and on bioassay plant performance. Our findings show species‐specific (rather than consistent within groups of natives and non‐natives) soil conditioning effects on both soil nutrients and the soil microbial community by plants. Additionally, native species produced plant–soil feedback types that benefit other species more than themselves and non‐native invasive species tended to produce plant–soil feedback types that benefit themselves more than other species. These results, coupled with previous field observations, support hypotheses that plant–soil feedbacks may be a mechanism by which some non‐native species increase their invasive potential and plant–soil feedbacks may influence the vulnerability of a site to invasion.     

Long‐term plant community trajectories suggest divergent responses of native and non‐native perennials and annuals to vegetation removal and seeding treatments

Land managers frequently apply vegetation removal and seeding treatments to restore ecosystem function following woody plant encroachment, invasive species spread, and wildfire. However, the long‐term outcome of these treatments is unclear due to a lack of widespread monitoring. We quantified how vegetation removal (via wildfire or management) with or without seeding and environmental conditions related to plant community composition change over time in 491 sites across the intermountain western United States. Most community metrics took over 10 years to reach baseline conditions posttreatment, with the slowest recovery observed for native perennial cover. Total cover was initially higher in sites with seeding after vegetation removal than sites with vegetation removal alone, but increased faster in sites with vegetation removal only. Seeding after vegetation removal was associated with rapidly increasing non‐native perennial cover and decreasing non‐native annual cover. Native perennial cover increased in vegetation removal sites irrespective of seeding and was suppressed by increasing non‐native perennial cover. Seeding was associated with higher non‐native richness across the monitoring period as well as initially higher, then declining, total and native species richness. Several cover and richness recovery metrics were positively associated with mean annual precipitation and negatively associated with mean annual temperature, whereas relationships with weather extremes depended on the lag time and season. Our results suggest that key plant groups, such as native perennials and non‐native annuals, respond to restoration treatments at divergent timescales and with different sensitivities to climate and weather variation.     

Management of Non‐Native Annual Plants to Support Recovery of an Endangered Perennial Forb,Ambrosia pumila

Invasive non‐native plants pose a ubiquitous threat to native plant communities and have been blamed for the decline of many endangered species. Endangered species legislation provides legal instruments for protection, but identifying a general method for protecting endangered species by managing non‐natives is confounded by multiple factors. We compared non‐native management methods aimed at increasing populations of an endangered forb, Ambrosia pumila, and associated native plants. We compared the effects of a grass‐specific herbicide (Fusilade II), hand‐pulling, and mowing in two degraded coastal sage scrub sites in southern California, U.S.A. At both sites, hand‐pulling had the greatest effect on non‐native cover, and correspondingly resulted in the greatest increase in A. pumila stems. Fusilade II application also led to an increase in A. pumila, but was not as effective in controlling non‐native plants as hand‐pulling and its effect varied with the dominant non‐native species. Mowing was not effective at promoting A. pumila, and its effect on non‐native cover seemed to be related to rainfall patterns. Although some methods increased A. pumila, none of our treatments simultaneously increased cover of other native plants. Hand‐pulling, the most effective treatment, is labor intensive and thus only feasible at small spatial scales. At larger scales, managers should take an experimental approach to identifying the most appropriate method because this can vary depending on the specific management objective (endangered species or whole native community), the dominant non‐natives, yearly variation in weather, and the timing of treatment application.     

Non‐native plant species benefit from disturbance: a meta‐analysis

Disturbances, such as fire and grazing, are often claimed to facilitate plant species richness and plant invasions in particular, although empirical evidence is contradictory. We conducted a meta‐analysis to synthesize the literature on how non‐native plant species are affected by disturbances. We explored whether the observed impact of disturbance on non‐native plant communities is related to its type and frequency, to habitat type, study approach (observational or experimental), and to the temporal and spatial scales of the study. To put the results in a broader context, we also conducted a set of parallel analyses on a data set involving native plant species. The diversity and abundance of non‐native plant species were significantly higher at disturbed sites than at undisturbed sites, while the diversity and abundance of native plant species did not differ between the two types of sites. The effect of disturbance on non‐native plant species depended on the measure used to evaluate the impact (species diversity or abundance) and on disturbance type, with grazing and anthropogenic disturbances leading to higher diversity and abundance of non‐native plant species than other disturbance types examined. The impact of disturbance on non‐natives was also associated with study approach, habitat type and temporal scale, but these factors covaried with disturbance type, complicating the interpretation of the results. Overall, our results indicate that disturbance has a positive impact particularly on non‐native plant species (at least when they are already present in the community), and that the strength of this impact depends primarily on the disturbance type. Synthesis Empirical evidence of the effect of disturbances on plant species richness is contradictory. Here we use a meta‐analysis to synthesize the published literature on how different types of disturbances influence the diversity and abundance of plant species, focusing in particular on non‐native plants. Our study supports the hypothesis that disturbances generally facilitate the diversity and abundance of non‐native plant species, although the strength of this facilitation depends primarily on the disturbance type.     

Soil pH influences patterns of plant community composition after restoration with native‐based seed mixes

Reclamation of highly disturbed lands typically includes establishing fast‐growing, non‐native plants to achieve rapid ground cover for erosion control. Establishing native plant communities could achieve ecosystem functions beyond soil erosion, such as providing wildlife habitat. Pipelines, or other disturbed corridors through a landscape, present unique challenges for establishing native plant communities given the heterogeneity of soil environments and invasive plant propagule pressure. We created two structural equation models to address multiple related hypotheses about the influence of soil pH on plant community composition (current diversity and vegetative cover of the original restoration seed mix and background flora, and invasive plant density during mix establishment and current density) of a highly disturbed landscape corridor restored with native species. To test our hypotheses we conducted a plant survey on a gas pipeline crossing two state forests in the north‐central Appalachians that had been seeded with a native‐based mixture 8 years prior. Low soil pH was a strong predictor of density of the invasive annual plant, Microstegium vimineum, and had resulted in lower species diversity and cover of the seeded mix. Overall, our data provide evidence that native‐based grass and forb mixtures can establish and persist on a wide range of soil environments and thrive in competition with invasive plants in moderately acidic to neutral soils. Advancing knowledge on restoration methods using native species is essential to improving restoration practice norms to incorporate multifunctional ecological goals.     

Are two strategies better than one? Manipulation of seed density and soil community in an experimental prairie restoration

Restoration practitioners have a variety of practices to choose from when designing a restoration, and different strategies may address different goals. Knowledge of how to best use multiple strategies could improve restoration outcomes. Here, we examine two commonly suggested strategies in a single tallgrass prairie restoration experiment: increased forb sowing density and prairie soil inoculation. We designed a study with two different forb seeding densities. Within these densities, we transplanted seedlings into 1‐m² plots that had been grown in either a whole prairie soil inoculum or sterilized prairie soil. After 4 years, we found positive effects of both high forb sowing density and inoculation treatments on the ratio of seeded to nonseeded plant cover in these plots, and negative effects of both treatments on nonseeded plant diversity. No effects of either treatment were seen on seeded plant diversity. Each strategy also affected the plant community in different ways: high forb sowing density increased seeded forb richness and decreased native nonseeded plant cover, while inoculation decreased non‐native cover, and tended to increase average successional stage of the community. These effects on restoration outcome were typically independent of each other, with the result that plots with both manipulations had the most positive effects on restoration outcomes. We thus advocate the combined use of these restoration strategies, and further studies which focus on both seeding and soil community manipulation in restoration.     

Quandaries of a decade‐long restoration experiment trying to reduce invasive species: beat them,join them,give up,or start over?

We evaluate the outcomes and consequences of a decade‐long restoration project in a Hawaiian lowland wet forest as they relate to long‐term management actions. Our initial study was designed both to promote native biodiversity and to develop knowledge that would enable land management agencies to restore invaded forests. Our premise of success followed the prevalent perception that short‐term management, such as removal of invasive species, ideally translates into long‐term and sustainable restoration. We were therefore disappointed and perhaps discouraged in our results—little recovery of native biodiversity despite ongoing and labor‐intensive management. Not only did we fail to return the invaded forest to a native‐dominated system but also our efforts lead to recruitment of new non‐native species assemblages. The sobering truth of many restoration projects in Hawaii and elsewhere is that we can never completely walk away and “consider the job finished,” or we have to accept that some ecosystems cannot be returned to an all‐native state. Essentially, costs of restoration may outweigh the accomplishment. This setback gave us an opportunity to reconsider and modify our initial approach. By starting over with a new direction using both native and non‐invasive but non‐native species, we have adopted a new philosophy of “join them.” In our revision, we changed the players in the game by following invasive species removal with outplantings of native and non‐invasive non‐native species that will functionally fill missing roles in the ecosystem. We link social interest in the new experiment to changing attitudes about naturalness.     

Relationships between Methylobacteria and Glyphosate with Native and Invasive Plant Species: Implications for Restoration

After removing invasive plants, whether by herbicides or other means, typical restoration design focuses on rebuilding native plant communities while disregarding soil microbial communities. However, microbial–plant interactions are known to influence the relative success of native versus invasive plants. Therefore, the abundance and composition of soil microorganisms may affect restoration efforts. We assessed the effect of herbicide treatment on phytosymbiotic pink‐pigmented facultative methylotrophic (PPFM) bacteria and the potential consequences of native and invasive species establishment post‐herbicide treatment in the lab and in a coastal sage scrub (CSS)/grassland restoration site. Lab tests showed that 4% glyphosate reduced PPFM abundance. PPFM addition to seeds increased seedling length of a native plant (Artemisia californica) but not an invasive plant (Hirschfeldia incana). At the restoration site, methanol addition (a PPFM substrate) improved native bunchgrass (Nassella pulchra) germination and size by 35% over controls. In a separate multispecies field experiment, PPFM addition stimulated the germination of N. pulchra, but not that of three invasive species. Neither PPFM nor methanol addition strongly affected the growth of any plant species. Overall, these results are consistent with the hypothesis that PPFMs have a greater benefit to native than invasive species. Together, these experiments suggest that methanol or PPFM addition could be useful in improving CSS/grassland restorations. Future work should test PPFM effects on additional species and determine how these results vary under different environmental conditions.     

Restoration of California Native Grasses and Clovers: The Roles of Clipping,Broadleaf Herbicide,and Native Grass Density

One of the major challenges confronting grassland restoration of highly invaded communities is increasing the diversity of native species. There is surprisingly little research investigating how reconstructed native grasslands respond to common management techniques and how these techniques influence the relative establishment of both native grasses and forbs. Despite the diversity and wide distribution of native clovers in California, few practitioners incorporate them into grassland restoration plans. Conversely, non‐native clovers have been seeded extensively onto California rangelands. This study addresses the following questions: (1) Using readily available management tools, is there a strategy that can benefit the growth of both planted native bunchgrasses and seeded clovers? (2) Do native bunchgrasses compete with establishing clovers and non‐native grasses? (3) Do native and non‐native clovers differ in their response to management treatments or in their productivity? Plots were established to test three factors in different combinations over 3 years: (1) early spring clipping, (2) initial broadleaf herbicide, and (3) native bunchgrass planting density. Native and non‐native clovers were seeded in years 2 and 3. Early spring clipping did not have a significant effect on native bunchgrass cover, yet it did result in greater growth of native and non‐native clovers. The direction of the response to broadleaf herbicide changed between years for native bunchgrasses and was consistently negative for native clovers. Plots with higher native grass densities did not adversely affect the seeded clovers, yet non‐native grass cover was reduced. Native and non‐native clovers exhibited similar responses to clipping and established at similar densities.