Carla M. D'Antonio

• University of California, Santa Barbara

Global change is associated with variable shifts in the annual production of aboveground plant biomass, suggesting localized sensitivities with unclear causal origins. Combining remotely sensed normalized difference vegetation index data since the 1980s with contemporary field data from 84 grasslands on 6 continents, we show a widening divergence i...

While the influence of canopy trees on soils in natural and restored forest environments is well studied, the influence of understory species is not. Here, we evaluate the effects of outplanted native woody understory on invasive grass biomass and soil nutrient properties in heavily grass-invaded 30 + year-old plantations of a native N-fixing tree...

Climate change is increasing the frequency and severity of short-term (~1 y) drought events—the most common duration of drought—globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in t...

Millions of hectares of agricultural land have been abandoned globally in recent decades, presenting opportunities for secondary vegetation growth and restoration. While abandoned fields have the potential to return to ecological communities with similar species diversity to their pre-agricultural state, they alternatively may transition to novel e...

Ecological restoration often focuses on short‐term intervention efforts with the goal of creating restored ecosystems that do not require continuous human maintenance. Here, we ask: Do short‐term restoration efforts result in self‐sustaining native assemblages, or do these restored ecosystems require long‐term management to prevent reinvasion of ex...

Restricting seed collecting to local populations is a common practice in restoration because it is assumed that most plants are adapted to local environmental conditions. However, there is still considerable debate about whether local seed collection should be the default seed‐provenancing strategy as the effects of climate change are increasingly...

Invasions by multiple non‐native plant species are common, but management programs often prioritize control of individual species that are expected to have the highest impacts. Multi‐species invasions could have larger or smaller impacts than single‐species invasions depending on how multiple co‐occurring invaders interact to alter their abundance...

Deforestation and subsequent land-use conversion has altered ecosystems and led to negative effects on biodiversity. To ameliorate these effects, nitrogen-fixing (N 2 -fixing) trees are frequently used in the reforestation of degraded landscapes, especially in the tropics; however, their influence on ecosystem properties such as nitrogen (N) availa...

Forest removal for livestock grazing is a striking example of human‐caused state change leading to a stable, undesirable invasive grass system that is resistant to restoration efforts. Understanding which factors lead to resilience to the alternative grass state can greatly benefit managers when planning forest restoration. We address how threshold...

The increased occurrences of drought and fire may be contributing to the loss of biodiverse ecosystems in Mediterranean regions. Specifically, the conversion of diverse native shrublands, such as chaparral, to non‐native annual grassland by fire is of great conservation concern in California. To avoid or slow the loss of chaparral, it is important...

Introduction Forest restoration is a powerful tool to combat the dual threats of drought and fire, both of which have been increasing in frequency and severity in recent years in the Western United States. The hard-hit region of Southern California is home to the endemic bigcone Douglas-fir, Pseudotsuga macrocarpa (Vasey), whose abundance and range...

Big-cone Douglas-Fir ( Pseudotsuga macrocarpa , hereafter BCDF) is an endemic, fire-adapted conifer found throughout the mountains of southern California. Because recent large high intensity wildfires have resulted in loss of BCDF, understanding how environmental factors, such as topography, fuels, climate, and weather, impact BCDF survivorship is...

To evaluate how increased anthropogenic nutrient inputs alter carbon cycling in grasslands, we conducted a litter decomposition study across 20 temperate grasslands on three continents within the Nutrient Network, a globally distributed nutrient enrichment experiment We determined the effects of addition of experimental nitrogen (N), phosphorus (P)...

Trees can have large effects on soil nutrients in ways that alter succession, particularly in the case of nitrogen‐(N)‐fixing trees. In Hawaiʻi, forest restoration relies heavily on use of a native N‐fixing tree, Acacia koa (koa), but this species increases soil‐available N and likely facilitates competitive dominance of exotic pasture grasses. In...

Abiotic conditions can influence the effect that herbivores have on plant growth. Such biotic and abiotic interactions are of special interest in plant biological control programs because the goal of herbivore suppression of the target weed may not be reached in some abiotic settings. Additionally, target invasive plants typically occur across dive...

The form and function of terrestrial plants is largely governed by the availability of water, with plants in water‐limited environments expressing traits minimizing water loss and tissue damage during drought. Areas with high salinity are analogous to those with low water availability, even where water is abundant. We evaluated variation in salinit...

Non‐structural carbohydrate (NSC) storage may be under strong selection in woody plant species that occur across broad environmental gradients. We therefore investigated carbon (C) allocation strategies in a widespread non‐native woody plant, Tamarix. We predicted that genotypes with exposure to episodic freeze events would show elevated NSC concen...

Abandoned tropical pastures offer opportunities for passive and active restoration of native forest communities. Tree architecture of remnant canopy trees may be one important factor that can facilitate native plant recruitment in abandoned pastures but has largely been overlooked. Here, we evaluated patterns of native woody plant recruitment under...

Questions In southern California, shortened fire return intervals may contribute to a decrease in native chaparral shrub presence and an increase in non-native annual grass presence. To test the hypothesis that short-fire return intervals promote a loss in shrub cover, we examined the contribution of single short-interval fires and abiotic conditio...

Tropical montane forests are being lost at an alarming rate but harbor some of the globe’s most unique biodiversity. The Hawaiian archipelago is a prime example of the importance of high elevation forests to species conservation and persistence as they serve as the last refugia for Hawaiian birds. Yet these forests have been converted to invasive d...

This book contains 23 chapters divided into seven parts. Part I reviews the key hypotheses in invasion ecology that invoke biotic interactions to explain aspects of plant invasion dynamics; and reviews models, theories and hypotheses on how invasion performance and impact of introduced species in recipient ecosystems can be conjectured according to...

Invasion ecology has grown to include scientists with diverse skill sets who focus on a range of taxa and biomes. These researchers have the capacity to contribute to practical management solutions while also answering fundamental biological questions; however, scientific endeavors often fail to meet the perceived needs of practitioners involved in...

Invasion by exotic plant species can profoundly affect native plant species performance and the inferred proximate cause is typically competition. We used invaded grasslands in the semi-arid Western USA to separate resource competition from structural interference of an exotic grass on native forb performance, specifically evaluating the role of co...

Wetting of dry soil triggers a pulse of microbial respiration that has been attributed to two broad mechanisms: (1) recycling of microbial cellular carbon (C), and (2) consumption of extracellular organic C made available to microbes by wetting. We evaluated these two mechanisms by measuring cumulative CO2 release, changes in the size and chemical...

This book contains 23 chapters divided into seven parts. Part I reviews the key hypotheses in invasion ecology that invoke biotic interactions to explain aspects of plant invasion dynamics; and reviews models, theories and hypotheses on how invasion performance and impact of introduced species in recipient ecosystems can be conjectured according to...

Recovery trajectories derived from remote sensing data are widely used to monitor ecosystem recovery after disturbance events, but these trajectories are often retrieved without a precise understanding of the land cover within a scene. As a result, the sources of variability in post-disturbance recovery trajectories are poorly understood. In this s...

Herbivores alter plant biodiversity (species richness) in many of the world’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet,...

Across Mediterranean‐type climate regions, seasonal drought desiccates plants, facilitating ignition and the spread of wildfires. Along the California coast, summertime fog has the potential to ameliorate drought conditions and thus reduce plant flammability during a critical time of elevated fire risk. This study investigated the uptake of dry sea...

Most ecosystems have multiple-plant invaders rather than single-plant invaders, yet ecological studies and management actions focus largely on single invader species. There is a need for general principles regarding invader interactions across varying environmental conditions, so that secondary invasions can be anticipated and managers can allocate...

Despite a large body of research documenting invasive plant impacts, few studies have followed individual invaded sites over decades to observe how they change, and none have contrasted how compositional impacts from invasion compare to ecosystem‐process impacts over a multi‐decadal time‐scale. Using direct measurements of plant density and composi...

Across most Mediterranean-type climate regions, seasonal drought desiccates plants, facilitating ignition and the spread of wildfires. Along the California coast, summertime fog has the potential to ameliorate drought conditions and thus reduce plant flammability during a critical time of elevated fire risk. This study investigated the uptake of dr...

Patterns of woody-plant mortality have been linked to global-scale environmental changes, such as extreme drought, heat stress, more frequent and intense fires, and episodic outbreaks of insects and pathogens. Although many studies have focussed on survival and mortality in response to specific physiological stresses, little attention has been paid...

Niche dimensionality provides a general theoretical explanation for biodiversity-more niches, defined by more limiting factors, allow for more ways that species can coexist. Because plant species compete for the same set of limiting resources, theory predicts that addition of a limiting resource eliminates potential trade-offs, reducing the number...

Ecosystem eutrophication often increases domination by non-natives and causes displacement of native taxa. However, variation in environmental conditions may affect the outcome of interactions between native and non-native taxa in environments where nutrient supply is elevated. We examined the interactive effects of eutrophication, climate variabil...

Mediterranean-type ecosystems are structured by fire. In California chaparral, fires uncouple inorganic nitrogen (N) production and consumption by enhancing nitrification and reducing plant uptake. Nitrate (NO3−) that accumulates after fire is vulnerable to leaching. However, the controls over N metabolism can change as chaparral ecosystems recover...

QuestionsWildfire is a natural disturbance that shapes vegetation characteristics worldwide, while prescribed fire is increasingly used to modify vegetation composition and structure. Due to invasion of many ecosystems by exotic species, a concern of land managers is whether wildfire and prescribed fire alter plant communities in favour of exotics....

Despite obvious impacts of nonnative species in many ecosystems, the long-term outcome of competition between native and exotic species often remains unclear. Demographic models can resolve the outcome of competition between native and exotic species and provide insight into conditions favoring exclusion vs. coexistence. California grasslands are o...

Isolated trees in savannas worldwide are known to modify their local environment and interact directly with neighboring plants. Less is known about how related tree species differ in their impacts on surrounding communities, how the effects of trees vary between years, and how composition might change following loss of the tree. To address these kn...

Harsh habitats dominated by invasive species are difficult to restore. Invasive grasses in arid environments slow succession toward more desired composition, yet grass removal exacerbates high light and temperature, making the use of “nurse plants” an appealing strategy. In this study of degraded subtropical woodlands dominated by alien grasses in...

Increased fire frequency has been shown to promote alien plant invasions in the western United States, resulting in persistent vegetation type change. Short interval fires are widely considered to be detrimental to reestablishment of shrub species in southern California chaparral, facilitating the invasion of exotic annuals and producing "type conv...

Background/Question/Methods Spatial heterogeneity plays a critical role in driving many ecological patterns and processes, including species coexistence, biological invasions, and patterns of alpha and beta diversity. Recently, spatial heterogeneity has been implicated as an important factor responsible for buffering fish and plant communities ag...

Background/Question/Methods Fog can be a significant force in shaping plant communities, particularly in coastal regions such as in California where it ameliorates summer temperatures and reduces drought stress. In southern California, fog tends to occur during the late summer during the peak of the drought season. The occurrence and seasonality...

Background/Question/Methods Climate change and increasing anthropogenic fire ignitions are expected to decrease fire return intervals in shrubland communities in Southern California. Short-interval fires (two fires within five years) may initiate a positive feedback, placing native chaparral species at risk of replacement by alien annual grasses. M...

Background/Question/Methods Extreme climatic events appear to be increasing in their frequency in the western USA over the last 100 years. Whether and how such events promote vegetation change remains an unanswered question. While managers generally expect drought to be correlated with the occurrence of fire, and in arid systems for invasive gras...

Non‐native species with growth forms that are different from the native flora may alter the physical structure of the area they invade, thereby changing the resources available to resident species. This in turn can select for species with traits suited for the new growing environment. We used adjacent uninvaded and invaded grassland patches to eval...

Scattered trees in grass-dominated ecosystems often act as islands of fertility with important influences on community structure. Despite the potential for these islands to be useful in restoring degraded rangelands, they can also serve as sites for the establishment of fast growing non-native species. In California oak savannas, native perennial g...

In the Sierra Nevada region of California, local ecological processes are greatly influenced by two major stand replacement disturbances: wildfire and selective logging. A study of vegetation regeneration in post-disturbance environment is essential for us to better understand and evaluate the effects of disturbances on ecological processes such as...

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 d...

Returning native species to habitats degraded by biological invasions is a critical conservation goal. A leading hypothesis poses that exotic plant dominance is self-reinforced by impacts on ecosystem processes, leading to persistent stable states. Invaders have been documented to modify fire regimes, alter soil nutrients or shift microbial communi...

Invasions have increased the size of regional species pools, but are typically assumed to reduce native diversity. However, global-scale tests of this assumption have been elusive because of the focus on exotic species richness, rather than relative abundance. This is problematic because low invader richness can indicate invasion resistance by the...

Background/Question/Methods Fog can be a significant force in shaping plant communities, particularly in coastal regions such as in California where it ameliorates summer temperatures and can reduce drought stress. The effect of fog on coastal shrublands, particularly fire prone ones, has not been well studied and the likelihood that fog events m...

A common hypothesis to explain the effect of litter mixing is based on the difference in litter N content between mixed species. Although many studies have shown that litter of invasive non-native plants typically has higher N content than that of native plants in the communities they invade, there has been surprisingly little study of mixing effec...

Alterations in natural fire patterns have negatively affected fire-prone ecosystems in many ways. The historical range of variability (HRV) concept evolved as a management target for natural vegetation composition and fire regimes in fire-prone ecosystems. HRV-based management inherently assumes that ecosystem resilience is reflected in observed ra...

Non-native, invasive grasses have been linked to altered grass-fire cycles worldwide. Although a few studies have quantified resulting changes in fire activity at local scales, and many have speculated about larger scales, regional alterations to fire regimes remain poorly documented. We assessed the influence of large-scale Bromus tectorum (hereaf...

Climate change and biological invasions are primary threats to global biodiversity that may interact in the future. To date, the hypothesis that climate change will favour non-native species has been examined exclusively through local comparisons of single or few species. Here, we take a meta-analytical approach to broadly evaluate whether non-nati...

Background/Question/Methods Invasive species are well known to have dramatic impacts on ecosystems, and it is hypothesized that such impacts can feed back to exacerbate invader abundance. However, long-term data on ecosystem impacts of invasive species are often unavailable, so it is not known whether hypothesized relationships persist over time....

Background/Question/Methods Climate change and biological invasions are two primary threats to global biodiversity, and it has been hypothesized that these factors will operate synergistically in the future to favor, and thus facilitate the spread of, non-native species. To date, this hypothesis has primarily been developed based on local compari...

Background/Question/Methods The impacts of plant invaders are often measured when they are dominant or co-dominant at a site and then extrapolated to infer long-term ecosystem outcomes. Yet for most invaders, we do not know their longterm persistence and or how their impacts change over time. Longterm sites that we established in invaded seasonall...

Background/Question/Methods: The impacts of non-native plant species on vertical and horizontal physical structure are rarely quantified, yet are likely to be important in determining what species can coexist with the invader. Impacts on physical structure and diversity may be greater when the life history of the non-native species differs from tha...

Background/Question/Methods Trees within savannas affect patterns of species occurrence and diversity. Oaks in Californian savannas are associated with increased dominance of exotic species beneath their canopy, reducing native and non-native species richness. At a landscape scale, however, oak trees may increase the number of available niches re...

Background/Question/Methods Fire is a major restructuring force in Mediterranean-type ecosystems, inducing nutrient redistribution that is frequently invoked as a driver of ecosystem recovery. Fire severity is expected to increase with climate warming and associated droughts. To study ecosystem response to high intensity landscape fire, we used a...

Effects of anthropogenic nitrogen (N) deposition and the ability of terrestrial ecosystems to store carbon (C) depend in part on the amount of N retained in the system and its partitioning among plant and soil pools. We conducted a meta-analysis of studies at 48 sites across four continents that used enriched 15N isotope tracers in order to synthes...

Extreme climatic events (ECEs) - such as unusual heat waves, hurricanes, floods, and droughts - can dramatically affect ecological and evolutionary processes, and these events are projected to become more frequent and more intense with ongoing climate change. However, the implications of ECEs for biological invasions remain poorly understood. Using...

Global environmental change will affect non-native plant invasions, with profound potential impacts on native plant populations, communities and ecosystems. In this context, we review plant functional traits, particularly those that drive invader abundance (invasiveness) and impacts, as well as the integration of these traits across multiple ecolog...

The widespread recognition that nonnative plants can have significant biological and economic effects on the habitats they invade has led to a variety of strategies to remove them. Removal alone, however, is often not sufficient to allow the restoration of altered communities or ecosystems. The invasive plant's effects may persist after its removal...

Chaparral soil properties are reorganized over time and space by intertwining biotic and physical feedback mechanisms. Interactions between fire and hydrology in particular can drastically enhance the cycling of nutrients and alter their retention rates at multiple scales. In order to study watershed responses to high intensity landscape fire, we c...

Many non-native plants in the US have become problematic invaders of native and managed ecosystems, but a new generation of invasive species may be at our doorstep. Here, we review trends in the horticultural trade and invasion patterns of previously introduced species and show that novel species introductions from emerging horticultural trade part...

Invasive nonnative grasses have altered the composition of seasonally dry shrublands and woodlands throughout the world. In many areas they coexist with native woody species until fire occurs, after which they become dominant. Yet it is not clear how long their impacts persist in the absence of further fire. We evaluated the long-term impacts of gr...

Soil nitrogen (N) transformations have been shown to be influenced by plant community composition. Identifying species traits that control nitrogen dynamics is more straightforward when species dramatically differ in N input via litter (e.g., N-fixing invaders in a non-fixing community) or in litter carbon:N or lignin:N ratios. Cases where invaders...

The success of biological control programs is rarely assessed beyond population level impacts on the target organism. The question of whether a biological control agent can either partially or completely restore ecosystem services independent of population level control is therefore still open to discussion. Using observational and experimental app...

The impacts of biological invasions by non-native plants have been well studied from a variety of angles over the past two decades. Those exotic plants that alter ecosystem processes have been suggested to be especially ecologically important because they can create feedbacks that reinforce their own persistence. Such feedbacks can move the invaded...

Carpobrotus edulis (L.) N. E. Br., an exotic perennial that invades the coastal habitats of California, hybridizes with the presumed native Carpobrotus chilensis (Mol.) N. E. Br. To investigate the potential role of hybrids in the invasion process by C. edulis, we compared the growth and plasticity of clones of hybrids and parental species. Ramets...

Patterns of flowering and pollination visit of Carpobrotus spp. were examined to determine the hybridization potential between the introduced succulent perennial Carpobrotus edulis and its native congener, Carpobrotus chilensis, in coastal California. Both species flower from March to July and both are visited by the same Thysanoptera and Coleopter...

Components of the growth and life history of the red alga Rhodomela larix (Turner) C. Agardh were studied during an 18-month period at a high intertidal and a low intertidal site on the central Oregon coast. Growth was measured by following (i) individually marked upright axes, (ii) clumps of axes thought to represent individual plants, and (iii) l...

IntroductionHawaiian Ecosystems and Their VulnerabilitiesTechnologies to Detect Ecosystem - Transforming InvasionsAcknowledgementsReferences

Wildfires change plant communities by reducing dominance of some species while enhancing the abundance of others. Detailed habitat-specific models have been developed to predict plant responses to fire, but these models generally ignore the breadth of fire regime characteristics that can influence plant survival such as the degree and duration of e...

Fire in shrub-dominated portions of the Great Basin, largely fueled by non-native annuals such as Bromus tectorum, has become an important structuring force altering vegetation composition and soil characteristics. The extent to which fire affects native species in drier portions of the Great Basin, termed salt desert, is poorly documented. We cond...

Open grasslands in California and Washington are being invaded by two closely related European shrubs, French broom and Scotch broom, that are considered among the most invasive and damaging of wildland species in those habitats. In this study, we present evidence of their effects on soil nitrogen (N) and the implications for restoration. Using nat...

Fire is a worldwide phenomenon that appears in the geological record soon after the appearance of terrestrial plants. Fire influences global ecosystem patterns and processes, including vegetation distribution and structure, the carbon cycle, and climate. Although humans and fire have always coexisted, our capacity to manage fire remains imperfect a...

Early emergence of plant seedlings can offer strong competitive advantages over later-germi-nating neighbors through the preemption of limiting resources. This phenomenon may have contributed to the persistent dominance of European annual grasses over native perennial grasses in California grasslands, since the former species typically germinate ea...

Non‐native perennial grasses form 30% of the live understory biomass in seasonally dry, submontane forests in Hawaii Volcanoes National Park, yet their effects on native species are unknown. We removed these grasses from plots of 20 m × 20 m in 1991 and maintained removal and control areas over the next three years. Two fast growing shrub species,...

The management of plant invasions has typically focused on the removal of invading populations or control of existing widespread species to unspecified but lower levels. Invasive plant management typically has not involved active restoration of background vegetation to reduce the likelihood of invader reestablishment. Here, we argue that land manag...

Questions: How do young sagebrush shrubs ( Artemisia rothrockii, Asteraceae ) affect soil moisture availability? How do young sagebrush shrubs affect soil nitrogen cycling? How does the resident herb community respond to shrub removal in the early stages of sagebrush encroachment? Location: Mulkey and Bullfrog Meadows on the Kern Plateau in the Gol...

This chapter presents a discussion of one invasive plant species that is believed to act as both an autogenic and an allogenic engineer potentially influencing resident species composition and ecosystem processes through any of several pathways. Species such as C. edulis are of conservation concern because very few resident species appear to co-exi...

We measured spatial and temporal patterns of seed dispersal and seedling recruitment for 58 species in a grassland community to test whether seed dispersal could predict patterns of invasion after disturbance. For the 12 most abundant grasses, recruitment of native species was dependent on the propagule supply of both native and exotic species. Var...

Grasslands are one of California's most important ecosystems in terms of both biodiversity and economic value. Bringing together the large amount of research conducted in recent years on California's grasslands, this comprehensive, state-of-the-art sourcebook addresses the pressing need to understand this unique habitat. Providing a summary of curr...

Resistance to the invasion of exotic plants may sometimes result from the strong effects of a relatively small number of resident species. Understanding the mechanisms by which such species resist invasion could provide important insights for the management of invaded ecosystems. Furthermore, the individualistic responses of community members to re...

We studied the effect of two years of sawdust addition on the growth of native perennial grasses in a site where we manually removed two introduced nitrogen-fixing shrubs, French broom (Genista monspessulana) and Scotch broom (Cytisus scoparius) in central coastal California. We tested the hypothesis that sawdust addition to soil would reduce plant...

Grasslands created by grass invasions into shrublands or woodlands followed by fire are now a dominant feature of many seasonally dry environments. In Hawaii Volcanoes National Park, introduced perennial grasses dominate grasslands created by fire in grass-invaded woodlands. In a previous study, we found that net primary production in these grassla...

We tested the hypothesis that, where fire has historically been infrequent, wooded areas that have been invaded by grasses and converted to grassland by fire are predisposed to future fire compared to adjacent areas that remain wooded; thus, an initial forest fire may promote future fires. We compared microclimate between a grass-dominated burned a...