Windows of opportunity: historical and ecological controls on Berberis thunbergii invasions

Comparing long-term patterns of spread of native and invasive plants in a successional forest

A fundamental question in invasive plant ecology is whether invasive and native plants have different ecological roles. Differences in functional traits have been explored, but we lack a comparison of the factors affecting the spread of co-occurring natives and invasives. Some have proposed that to succeed, invasives would colonize a wider variety of sites, would disperse farther, or would be better at colonizing sites with more available light and soil nutrients than natives. We examined patterns of spread over 70 years in a regenerating forest in Connecticut, USA, where both native and invasive species acted as colonizers. We compared seven invasive and 19 native species in the characteristics of colonized plots, variation in these characteristics, and the importance of site variables for colonization. We found little support for the hypotheses that invasive plants succeed by dispersing farther than native plants or by having a broader range of site tolerances. Colonization by invasives was also not more dependent on light than colonization by natives. Like native understory species, invasive plants spread into closed-canopy forest and species-rich communities despite earlier predictions that these communities would resist invasion. The biggest differences were that soil nitrate and the initial land cover being open field increased the odds of colonization for most invasives but only for some natives. In large part, though, the spread of native and invasive plants was affected by similar factors.

Fire suppression and land-use strategies drive future dynamics of an invasive plant in a fire-prone mountain area under climate change

Woody invasive alien species can have profound impacts on ecosystem processes and functions, including fire regulation, which can significantly affect landscape resilience. Acacia dealbata, a widespread invasive alien plant in the Iberian Peninsula, holds well-known fire-adaptation traits (e.g., massive soil seed banks and heat-stimulated seed germination). In this study, we assess to what extent fire suppression and land-use strategies could affect the potential distribution of A. dealbata in a fire-prone transboundary protected mountain area of Portugal and Spain, using Habitat Suitability Models. Specifically, we predicted changes in habitat suitability for A. dealbata between years 2010 and 2050. We explored the potential impacts of two land-use strategies ('Business-as-usual' or 'High Nature Value farmlands') combined with three levels of fire suppression effectiveness using the biomod2 package in R. We also considered the potential effects of two climate change scenarios (RCP4.5 and RCP8.5). Our modeling approach demonstrated a strong capacity to predict habitat suitability using either climate or land-cover information alone (AUC climate = 0.947; AUC LC = 0.957). According to climate-based models, A. dealbata thrives under conditions characterized by higher precipitation seasonality, higher precipitation in the warmest month, and higher minimum temperature in the coldest month. Regarding land cover, A. dealbata thrives mainly in landscapes dominated by urban areas and evergreen forest plantations. Our models forecasted that habitat suitability by 2050 could either increase or decrease depending on the specific combinations of fire suppression, land-use, and climate scenarios. Thus, a combination of business-as-usual and fire-exclusion strategies would enhance habitat suitability for the species. Conversely, management promoting High Nature Value farmlands would decrease the available suitable habitat, particularly under low fire suppression efforts. These findings suggest that promoting sustainable farming activities could impede the spread of A. dealbata by reducing habitat availability, while strategies aiming at fire-exclusion could facilitate its expansion, likely by enabling establishment and large seed production. This study highlights the complex interplay between fire-prone invasive species, fire and land-use strategies, and climate change; and thus the need to consider the interactions between land-use and fire management to promote invasive species control and landscape resilience.

'Invasion debt' after extensive land-use change: An example from eastern Australia

Land-use change, and associated land clearing/conversion and fragmentation are major drivers of biodiversity decline across the globe. The spread of invasive species is a well-recognised consequence of land-use change. The extent and intensity of invasion however is often difficult to assess due to a lack of temporal data. Using detailed mapping information for 130, 950 km² of sub-coastal Queensland, Australia and results from field surveys we investigated changes to land-use, the extent of remnant (intact) vegetation and the spread of prominent invasive plant species over time (1997-2018). In the 50 years prior to 1997 the area underwent significant land development (mostly for livestock grazing and crops), resulting in a reduction of 45% of its remnant vegetation. Despite key policy developments aimed at protecting the remaining vegetation and species, 7392 km² was cleared/converted between 1997 and 2017, mainly for the expansion of grazing and cropping lands. Vegetation types specifically listed for national protection under these policies were some of the greatest affected, highlighting the need for improved implementation and regulation of these control measures. Within remaining fragments of remnant vegetation, the cover and presence of two invasive perennial grass species indian couch (Bothriochloa pertusa) and buffel grass (Cenchrus ciliaris) increased significantly during this time period. There was also a moderate increase in the cover and presence of the annual herb Parthenium weed (Parthenium hysterophorus). The spread of these species within the landscape likely reflects an 'invasion debt', incurred from an intense history of land-use within the region and we predict this trend will continue to threaten remnant ecosystems.

Physiological indicators of habitat quality for a migratory songbird breeding in a forest invaded by non-native Japanese barberry (Berberis thunbergii)

Non-native, invasive plants can impact birds by altering food sources, nesting substrates and other critical resources. Japanese barberry (Berberis thunbergii) is one of the most invasive, non-native woody plants in in the northeastern USA, and yet almost nothing is known about its effects on birds or other wildlife. To investigate individual-level impacts of Japanese barberry on a forest-breeding bird, we compared food abundance (leaf-litter arthropod biomass) and the physiological condition of territorial male ovenbirds (Seiurus aurocapilla) between areas of a forest preserve in New York State that had high or low densities of Japanese barberry. We used haemoglobin and plasma triglyceride concentrations to indicate energetic condition, plasma uric acid and total plasma protein levels to indicate diet quality, and heterophil to lymphocyte ratios to indicate chronic stress. We found no difference in arthropod biomass between ovenbird territories that were heavily invaded by or relatively free of Japanese barberry. Perhaps largely as a result, we found no relationship between Japanese barberry density and any of our five haematological condition indices. There was also no difference in body mass, body size or age ratio between ovenbirds nesting in areas with low or high densities of Japanese barberry to suggest that relatively uninvaded forest patches were in greater demand and acquired by the most dominant individuals. Our results indicate that Japanese barberry does not reduce habitat quality for breeding male ovenbirds in a way that affects their prey abundance or physiological condition, but we caution that other species of birds and other aspects of habitat quality could be affected differently. We encourage future research on additional bird species and the effects of Japanese barberry on factors such as diet composition, pairing and nesting success and post-fledging survival to improve science-based decision-making about the extent to which conservation resources should be applied towards Japanese barberry control.

Invasive Japanese Barberry, Berberis thunbergii (Ranunculales: Berberidaceae) Is Associated With Simplified Branch-Dwelling and Leaf-Litter Arthropod Communities in a New York Forest

Arthropod food webs can be indirectly impacted by woody plant invasions, with cascading consequences for higher trophic levels. There are multiple bottom-up pathways by which invasive plants can alter food webs: above-ground interactions based on plant-herbivore associations and below-ground at the interface of leaf-litter and soil food webs. We compared arthropod community composition in these two food web dimensions in a New York forest that has been heavily invaded by nonnative Japanese barberry. Using two sampling protocols, we compared arthropod community composition on Japanese barberry shrubs to multiple species of native host shrubs and then compared leaf-litter arthropod assemblages between forest patches with exceptionally high Japanese barberry densities and those with relatively little to no Japanese barberry present. Fitting with trends in other woody shrub invasions, arthropod species richness was significantly lower in the leaf litter around Japanese barberry and on Japanese barberry plants themselves. Although overall arthropod abundance was also significantly lower on and in the leaf litter around Japanese barberry than on and around native shrubs, total biomass did not differ due to the taxa associated with Japanese barberry tending to be larger-bodied. We observed a dramatic reduction in predatory arthropods in response to both bottom-up pathways, particularly among ants and spiders. Our results show that Japanese barberry-invaded habitats may be experiencing trophic downgrading as result of lower numbers of generalist predators like spiders and ants, which may have rippling effects up the food web to insectivorous animals and their predators.

Multispectral Approach for Identifying Invasive Plant Species Based on Flowering Phenology Characteristics

Invasive plant species (IPS) are the second biggest threat to biodiversity after habitat loss. Since the spatial extent of IPS is essential for managing the invaded ecosystem, the current study aims at identifying and mapping the aggressive IPS of Acacia salicina and Acacia saligna, to understand better the key factors influencing their distribution in the coastal plain of Israel. This goal was achieved by integrating airborne-derived hyperspectral imaging and multispectral earth observation for creating species distribution maps. Hyperspectral data, in conjunction with high spatial resolution species distribution maps, were used to train the multispectral images at the species level. We incorporated a series of statistical models to classify the IPS location and to recognize their distribution and density. We took advantage of the phenological flowering stages of Acacia trees, as obtained by the multispectral images, for the support vector machine classification procedure. The classification yielded an overall Kappa coefficient accuracy of 0.89. We studied the effect of various environmental and human factors on IPS density by using a random forest machine learning model, to understand the mechanisms underlying successful invasions, and to assess where IPS have a higher likelihood of occurring. This algorithm revealed that the high density of Acacia most closely related to elevation, temperature pattern, and distances from rivers, settlements, and roads. Our results demonstrate how the integration of remote-sensing data with different data sources can assist in determining IPS proliferation and provide detailed geographic information for conservation and management efforts to prevent their future spread.

Landscape-scale GPP and carbon density inform patterns and impacts of an invasive tree across wet forests of Hawaii

Plant invasion typically occurs within a landscape-scale framework of abiotic and biotic conditions, often resulting in emergent feedbacks among environment, ecosystem functions, and the dominance of invasive species. Understanding the mechanisms underlying successful invasions is an important component of conservation and management efforts, but this has been poorly investigated in a spatially explicit manner. Knowing where and why invasion patterns change throughout the landscape enables managers to use context-specific controls on the spread of invasive species. Using high-resolution airborne imaging spectroscopy, we studied plant performance in growth within and across landscapes to examine the dominance and spatial distribution of an invasive tree, Psidium cattleianum (strawberry guava), in heterogeneous environmental conditions of a submontane Hawaiian tropical forest. We assessed invader performance using the GPP ratio index, which is the relative difference in remotely sensed estimates of gross primary productivity between canopies of guava and canopies of the invaded plant community. In addition, we used airborne LiDAR data to evaluate the impacts of guava invasion on the forest aboveground carbon density in different environments. Structural equation modeling revealed that substrate type and elevation above sea level interact and amplify landscape-scale differences in productivity between the invasive species and the host plant community (GPP ratio); differences that ultimately control levels of dominance of guava. We found shifts in patterns of forest carbon storage based on both gradual increase of invader dominance and changes in environmental conditions. Overall, our results demonstrate that the remotely sensed index defined as the GPP ratio provided an innovative spatially explicit approach to track and predict the success of invasive plants based in their canopy productivity, particularly within a landscape-scale framework of varying environmental factors such as soils and elevation. This approach may help managers accurately predict where invaders of forests, scrublands, or grasslands are likely to exhibit high levels of dominance before the environment is fully invaded.

Historic Mining and Agriculture as Indicators of Occurrence and Abundance of Widespread Invasive Plant Species

Anthropogenic disturbances often change ecological communities and provide opportunities for non-native species invasion. Understanding the impacts of disturbances on species invasion is therefore crucial for invasive species management. We used generalized linear mixed effects models to explore the influence of land-use history and distance to roads on the occurrence and abundance of two invasive plant species (Rosa multiflora and Berberis thunbergii) in a 900-ha deciduous forest in the eastern U.S.A., the Powdermill Nature Reserve. Although much of the reserve has been continuously forested since at least 1939, aerial photos revealed a variety of land-uses since then including agriculture, mining, logging, and development. By 2008, both R. multiflora and B. thunbergii were widespread throughout the reserve (occurring in 24% and 13% of 4417 10-m diameter regularly-placed vegetation plots, respectively) with occurrence and abundance of each varying significantly with land-use history. Rosa multiflora was more likely to occur in historically farmed, mined, logged or developed plots than in plots that remained forested, (log odds of 1.8 to 3.0); Berberis thunbergii was more likely to occur in plots with agricultural, mining, or logging history than in plots without disturbance (log odds of 1.4 to 2.1). Mining, logging, and agriculture increased the probability that R. multiflora had >10% cover while only past agriculture was related to cover of B. thunbergii. Proximity to roads was positively correlated with the occurrence of R. multiflora (a 0.26 increase in the log odds for every 1-m closer) but not B. thunbergii, and roads had no impact on the abundance of either species. Our results indicated that a wide variety of disturbances may aid the introduction of invasive species into new habitats, while high-impact disturbances such as agriculture and mining increase the likelihood of high abundance post-introduction.

Integrated assessment of biological invasions

As the main witnesses of the ecological and economic impacts of invasions on ecosystems around the world, ecologists seek to provide the relevant science that informs managers about the potential for invasion of specific organisms in their region(s) of interest. Yet, the assorted literature that could inform such forecasts is rarely integrated to do so, and further, the diverse nature of the data available complicates synthesis and quantitative prediction. Here we present a set of analytical tools for synthesizing different levels of distributional and/or demographic data to produce meaningful assessments of invasion potential that can guide management at multiple phases of ongoing invasions, from dispersal to colonization to proliferation. We illustrate the utility of data-synthesis and data-model assimilation approaches with case studies of three well-known invasive species--a vine, a marine mussel, and a freshwater crayfish--under current and projected future climatic conditions. Results from the integrated assessments reflect the complexity of the invasion process and show that the most relevant climatic variables can have contrasting effects or operate at different intensities across habitat types. As a consequence, for two of the study species climate trends will increase the likelihood of invasion in some habitats and decrease it in others. Our results identified and quantified both bottlenecks and windows of opportunity for invasion, mainly related to the role of human uses of the landscape or to disruption of the flow of resources. The approach we describe has a high potential to enhance model realism, explanatory insight, and predictive capability, generating information that can inform management decisions and optimize phase-specific prevention and control efforts for a wide range of biological invasions.

Amplicon pyrosequencing reveals the soil microbial diversity associated with invasive Japanese barberry (Berberis thunbergii DC.)

The soil microbial community acts as a reservoir of microbes that directly influences the structure and composition of the aboveground plant community, promotes plant growth, increases stress tolerance and mediates local patterns of nutrient cycling. Direct interactions between plants and rhizosphere-dwelling microorganisms occur at, or near, the surface of the root. Upon introduction and establishment, invasive plants modify the soil microbial communities and soil biochemistry affecting bioremediation efforts and future plant communities. Here, we used tag-encoded FLX amplicon 454 pyrosequencing (TEFAP) to characterize the bacterial and fungal community diversity in the rhizosphere of Berberis thunbergii DC. (Japanese barberry) from invasive stands in coastal Maine to investigate effects of soil type, soil chemistry and surrounding plant cover on the soil microbial community structure. Acidobacteria, Actinobacteria, Proteobacteria and Verrucomicrobia were the dominant bacterial phyla, whereas fungal communities were comprised mostly of Ascomycota and Basidiomycota phyla members, including Agaricomycetes and Sordariomycetes. Bulk soil chemistry had more effect on the bacterial community structure than the fungal community. An effect of geographic location was apparent in the rhizosphere microbial communities, yet it was less significant than the effect of surrounding plant cover. These data demonstrate a high degree of spatial variation in the rhizosphere microbial communities of Japanese barberry with apparent effects of soil chemistry, location and canopy cover on the microbial community structure.

Increasing seriousness of plant invasions in croplands of eastern china in relation to changing farming practices: a case study

Arable areas are commonly susceptible to alien plant invasion because they experience dramatic environmental influences and intense anthropogenic activity. However, the limited reports on relevant factors in plant invasion of croplands have addressed single or a few invasive species and environmental factors. To elucidate key factors affecting plant invasions in croplands, we analyzed the relationship between 11 effective factors and changes in composition of alien plants, using field surveys of crop fields in Anhui Province conducted during 1987–1990 (historical dataset) and 2005–2010 (recent dataset), when rapid urbanization was occurring in China. We found that in the past few decades, the dominance and richness of alien plant populations approximately doubled, despite differences among the 4 regions of Anhui Province. Among the 38 alien invasive plant species observed in the sites, the dominance values of 11 species increased significantly, while the dominance of 4 species decreased significantly. The quantity of chemical fertilizer and herbicide applied, population density, agricultural machinery use, traffic frequency, and annual mean temperature were significantly related to increased richness and annual dominance values of alien plant species. Our findings suggest that the increase in alien plant invasions during the past few decades is primarily a result of increased application of chemical fertilizer and herbicides.

The new flora of northeastern USA: quantifying introduced plant species occupancy in forest ecosystems

Introduced plant species have significant negative impacts in many ecosystems and are found in many forests around the world. Some factors linked to the distribution of introduced species include fragmentation and disturbance, native species richness, and climatic and physical conditions of the landscape. However, there are few data sources that enable the assessment of introduced species occupancy in native plant communities over broad regions. Vegetation data from 1,302 forest inventory plots across 24 states in northeastern and mid-western USA were used to examine and compare the distribution of introduced species in relation to forest fragmentation across ecological provinces and forest types, and to examine correlations between native and introduced species richness. There were 305 introduced species recorded, and 66 % of all forested plots had at least one introduced species. Forest edge plots had higher constancy and occupancy of introduced species than intact forest plots, but the differences varied significantly among ecological provinces and, to a lesser degree, forest types. Weak but significant positive correlations between native and introduced species richness were observed most often in intact forests. Rosa multiflora was the most common introduced species recorded across the region, but Hieracium aurantiacum and Epipactus helleborine were dominant in some ecological provinces. Identifying regions and forest types with high and low constancies and occupation by introduced species can help target forest stands where management actions will be the most effective. Identifying seemingly benign introduced species that are more prevalent than realized will help focus attention on newly emerging invasives.

Historic land use influences contemporary establishment of invasive plant species

The legacy of agricultural land use can have widespread and persistent effects on contemporary landscapes. Although agriculture can lead to persistent changes in soil characteristics and plant communities, it remains unclear whether historic agricultural land use can alter the likelihood of contemporary biological invasions. To understand how agricultural land-use history might interact with well-known drivers of invasion, we conducted factorial manipulations of soil disturbance and resource additions within non-agricultural remnant sites and post-agricultural sites invaded by two non-native Lespedeza species. Our results reveal that variation in invader success can depend on the interplay of historic land use and contemporary processes: for both Lespedeza species, establishment was greater in remnant sites, but soil disturbance enhanced establishment irrespective of land-use history, demonstrating that contemporary processes can help to overcome legacy constraints on invader success. In contrast, additions of resources known to facilitate seedling recruitment (N and water) reduced invader establishment in post-agricultural but not in remnant sites, providing evidence that interactions between historic and contemporary processes can also limit invader success. Our findings thus illustrate that a consideration of historic land use may help to clarify the often contingent responses of invasive plants to known determinants of invasibility. Moreover, in finding significantly greater soil compaction at post-agricultural sites, our study provides a putative mechanism for historic land-use effects on contemporary invasive plant establishment. Our work suggests that an understanding of invasion dynamics requires knowledge of anthropogenic events that often occur decades before the introduction of invasive propagules.

Pinus halepensis invasion in mountain pampean grassland: effects of feral horses grazing on seedling establishment

We evaluated the mechanisms that determine the increasing abundance of Pinus halepensis in mountain pampean grasslands in Argentina that is associated with the continuous presence of feral horses. We hypothesized that direct and indirect effects of feral horse grazing on grassland may affect the establishment of P. halepensis. We conducted a field experiment to evaluate this hypothesis, studying the response of seedling emergence, survival and growth to herbaceous vegetation defoliation and soil disturbance in sites with contrasting grazing histories. We also evaluated the composition and structure of plant communities of each experimental site. Direct effects such as heavily defoliated perennial grasses and indirect effects such as reduced specific and functional richness, diversity and evenness enhanced the emergence, survival and early growth of the seedlings. High bare ground percentage and low grass biomass also positively affected seedling establishment. The experimental evidence demonstrates that the combination of invasional meltdown hypothesis and weakened biotic resistance are the mechanisms involved in P. halepensis invasion.

Legacy effects overwhelm the short-term effects of exotic plant invasion and restoration on soil microbial community structure, enzyme activities, and nitrogen cycling

Plant invasions can have substantial consequences for the soil ecosystem, altering microbial community structure and nutrient cycling. However, relatively little is known about what drives these changes, making it difficult to predict the effects of future invasions. In addition, because most studies compare soils from uninvaded areas to long-established dense invasions, little is known about the temporal dependence of invasion impacts. We experimentally manipulated forest understory vegetation in replicated sites dominated either by exotic Japanese barberry (Berberis thunbergii), native Viburnums, or native Vacciniums, so that each vegetation type was present in each site-type. We compared the short-term effect of vegetation changes to the lingering legacy effects of the previous vegetation type by measuring soil microbial community structure (phospholipid fatty acids) and function (extracellular enzymes and nitrogen mineralization). We also replaced the aboveground litter in half of each plot with an inert substitute to determine if changes in the soil microbial community were driven by aboveground or belowground plant inputs. We found that after 2 years, the microbial community structure and function was largely determined by the legacy effect of the previous vegetation type, and was not affected by the current vegetation. Aboveground litter removal had only weak effects, suggesting that changes in the soil microbial community and nutrient cycling were driven largely by belowground processes. These results suggest that changes in the soil following either invasion or restoration do not occur quickly, but rather exhibit long-lasting legacy effects from previous belowground plant inputs.

Disturbance affects short-term facilitation, but not long-term saturation, of exotic plant invasion in New Zealand forest

We investigate the spread of an exotic herb, Hieracium lepidulum, into a New Zealand Nothofagus forest with the aim of understanding how stand-development of tree populations, propagule pressure and invader persistence, affect invasion across the landscape and within communities. Using data repeatedly collected over 35 years, from 250 locations, we parametrize continuous-time Markov chain models and use these models to examine future projections of the invasion under a range of hypothetical scenarios. We found that the probability of invasion into a stand was relatively high following canopy disturbance and that local abundance of Hieracium was promoted by minor disturbances. However, model predictions extrapolated 45 years into the future show that neither the rate of landscape-level invasion, nor local population growth of Hieracium, was affected much by changing the frequency of canopy disturbance events. Instead, invasion levels were strongly affected by the ability of Hieracium to persist in the understorey following forest canopy closure, and by propagule supply from streams, forest edges and plants already established within the stand. Our results show that disturbance frequency has surprisingly little influence on the long-term trajectory of invasion, while invader persistence strongly determines invasion patterns.

Multivariate forecasts of potential distributions of invasive plant species

The fact that plant invasions are an ongoing process makes generalizations of invasive spread extraordinarily challenging. This is particularly true given the idiosyncratic nature of invasions, in which both historical and local conditions affect establishment success and hinder our ability to generate guidelines for early detection and eradication of invasive species. To overcome these limitations we have implemented a comprehensive approach that examines plant invasions at three spatial scales: regional, landscape, and local levels. At each scale, in combination with the others, we have evaluated the role of key environmental variables such as climate, landscape structure, habitat type, and canopy closure in the spread of three commonly found invasive woody plant species in New England, Berberis thunbergii, Celastrus orbiculatus, and Euonymus alatus. We developed a spatially explicit hierarchical Bayesian model that allowed us to take into account the ongoing nature of the spread of invasive species and to incorporate presence/absence data from the species' native ranges as well as from the invaded regions. Comparisons between predictions from climate-only models with those from the multiscale forecasts emphasize the importance of including landscape structure in our models of invasive species' potential distributions. In addition, predictions generated using only native range data performed substantially worse than those that incorporated data from the target range. This points out important limitations in extrapolating distributional ranges from one region to another.

Hierarchical models facilitate spatial analysis of large data sets: a case study on invasive plant species in the northeastern United States

Many critical ecological issues require the analysis of large spatial point data sets - for example, modelling species distributions, abundance and spread from survey data. But modelling spatial relationships, especially in large point data sets, presents major computational challenges. We use a novel Bayesian hierarchical statistical approach, 'spatial predictive process' modelling, to predict the distribution of a major invasive plant species, Celastrus orbiculatus, in the northeastern USA. The model runs orders of magnitude faster than traditional geostatistical models on a large data set of c. 4000 points, and performs better than generalized linear models, generalized additive models and geographically weighted regression in cross-validation. We also use this approach to model simultaneously the distributions of a set of four major invasive species in a spatially explicit multivariate model. This multispecies analysis demonstrates that some pairs of species exhibit negative residual spatial covariation, suggesting potential competitive interaction or divergent responses to unmeasured factors.

Vulnerability of rehabilitated agricultural production systems to invasion by nontarget plant species

Vast areas of arable land have been retired from crop production and "rehabilitated" to improved system states through landowner incentive programs in the United States (e.g., Conservation and Wetland Reserve Programs), as well as Europe (i.e., Agri-Environment Schemes). Our review of studies conducted on invasion of rehabilitated agricultural production systems by nontarget species elucidates several factors that may increase the vulnerability of these systems to invasion. These systems often exist in highly fragmented and agriculturally dominated landscapes, where propagule sources of target species for colonization may be limited, and are established under conditions where legacies of past disturbance persist and prevent target species from persisting. Furthermore, rehabilitation approaches often do not include or successfully attain all target species or historical ecological processes (e.g., hydrology, grazing, and/or fire cycles) key to resisting invasion. Uncertainty surrounds ways in which nontarget species may compromise long term goals of improving biodiversity and ecosystem services through rehabilitation efforts on former agricultural production lands. This review demonstrates that more studies are needed on the extent and ecological impacts of nontarget species as related to the goals of rehabilitation efforts to secure current and future environmental benefits arising from this widespread conservation practice.