Achieve Restoration Goals Research Articles

Inconsistent recovery of nitrogen cycling after feral ungulate removal across three tropical island ecosystems

Non-native ungulates (sheep, goats, and pigs) have significant negative impacts on ecosystem biodiversity, structure, and biogeochemical function throughout the Pacific Islands. Elevated nitrogen (N) availability associated with ungulate disturbance has been shown to promote the success of resource-exploitive invasive plants. While ungulate removal is a common restoration intervention, evaluations of its efficacy typically focus on vegetation responses, rather than underlying nutrient cycling. We used multiple chronosequences of ungulate exclusion (10–24 years duration) in three Hawaiian ecosystems (montane wet forest, dry forest, and dry shrubland) to determine N cycle recovery by characterizing gross mineralization and nitrification, soil inorganic N concentrations and leaching, N2O emissions, and plant tissue δ15N. Ungulate removal led to a 1–2 ‰ decline in foliar δ15N in most species, consistent with a long-term decrease in N fractionation via ecosystem N losses, or a shift in the relative turnover of N forms. This interpretation was supported by significant (dry forest) or trending (wet forest) increases in mineralization and decreases in nitrification, but conflicts with lack of observed change in inorganic N pool sizes or gaseous losses, and increased leaching in the dry forest. While results could indicate that ungulate invasions do not strongly impact N cycling in the first place (no uninvaded control sites exist in Hawai’i to test this hypothesis), this would be inconsistent with observations from other sites globally. Instead, impacts may be spatially patchy across the landscape, or ungulate invasions (possibly in combination with other disturbances) may have permanently shifted biogeochemical function or decoupled elemental cycles. We conclude that eliminating ungulate disturbance alone may not achieve restoration goals related to N cycling within the timeframe examined here.

Inverse priority effects: The order and timing of removal of invasive species influence community reassembly

Abstract An ongoing restoration challenge is to recover native communities after the removal of invasive species. Because priority effects (i.e. the order and timing of species arrival) can strongly determine the trajectory of community assembly, their intentional manipulation is gaining attention to manage invasive plants and achieve restoration goals. Yet, ecologists and conservationists rarely consider how the order and timing of species removal—inverse priority effect—may impact future plant communities. Here, we evaluated the dependence of community reassembly on inverse priority effects by experimentally removing the target invasives Sweetbriar rose (Rosa rubiginosa) and Scotch broom (Cytisus scoparius) in field and mesocosm communities. We manipulated removal order (rose before broom vs. broom before rose) and timing (simultaneously early vs. simultaneously late in the season). We performed a hierarchical modeling of species sommunity to assess differences in community structure in response to order and timing of removal, and to evaluate whether species origin and leaf and seed traits were associated with species responses. We found that the order of removal was as important as timing driving community reassembly. Simultaneous removal favoured nonnatives, more so when performed early. Sequential removals led to contrasting communities. Rose before broom removal also favoured nonnative grasses at expense of native species, whereas the inverse order produced small changes in communities. In general, species with high specific leaf area were boosted, regardless of their seed size. Synthesis and applications. Inverse priority effects are neglected mechanisms that can drive variability in the reassembly of plant communities and can potentially upgrade invasive species management. These historical contingencies suggest the existence of an optimal order of removal that facilitates the recovery of the native community. We found that simultaneous removal promoted secondary invasions to a greater extent than sequential removals. Furthermore, removal order affected post‐removal community structure. In our system, we suggest removing the rose before the broom to hinder nonnatives and pave the way for restoration of native communities. Our results show that manipulation of the order and timing of removal can help to achieve restoration goals.

Growth-survival trade-offs and the restoration of non-forested open ecosystems

The growth-survival trade-off has been extensively documented for phanerophyte species, whereas there is little evidence for non-phanerophyte species. However, information on the growth-survival trade-offs in non-phanerophyte species could be of great use in non-forested open ecosystem restoration by providing insights for plant production and transplantation, thus impacting the planning of cost-effective restoration actions. In this study, we explored the relationship between growth and survival of individual plants of non-phanerophyte species used in a coastal dune restoration project, and we investigated whether plant functional traits explained patterns of trade-off between growth and survival. We monitored 355 individual plants of 13 perennial non-phanerophyte species belonging to foredune and transition dune communities every 30 days after planting and calculated relative growth and survival rates. In addition, we regressed the relationship between growth and survival on values of leaf and floral traits. We found that, besides being a widely recognised axis of life history variation in phanerophyte species, the growth-survival trade-off can also be observed in perennial non-phanerophyte species. Species of different coastal dune communities (i.e., foredune vs. transition dune communities) differed with respect to the growth-survival trade-off, with plant species of foredune communities exhibiting higher growth but lower survival rates than plant species of transition dune communities. Leaf dry matter content and mean number of floral displays explained species position on the growth-survival trade-off axis; species with relatively high growth and low survival rates exhibited an acquisitive strategy, with low values of leaf dry matter content, but also a low sexual reproductive effort, as revealed by low number of floral displays. In contrast, plant species with relatively low growth and high survival rates exhibited a conservative strategy but also high sexual reproductive effort, suggesting that trade-offs occur in resource allocation among vegetative and reproductive plant structures. The trade-off we found between growth and survival in perennial non-phanerophyte species provides useful insights for planning cost-effective ecosystem restoration actions of non-forested open ecosystems, especially when the actions are nature-based and involve planting individual plants. The results of this study suggest that individual plant production for coastal dune restoration should disproportionately target plant species of foredune communities because they have low survival rates associated with low sexual reproductive effort. Planning plant production based on ecological knowledge of plant species’ growth and survival after planting in the field could help achieve restoration goals while meeting project cost-effectiveness requirements.

Landscape and site factors drive invasive Phragmites management and native plant recovery across Chesapeake Bay wetlands

AbstractSuccessful invasive plant management—where invaders are sufficiently reduced and diverse native plant communities recover—remains an elusive goal for land managers. The site‐ and landscape‐scale drivers of variable management outcomes and vegetation recovery are poorly understood due to a lack of rigorous experiments that characterize longer term vegetation trends across contexts. We present the results of a five‐year experiment across eight subestuaries of Chesapeake Bay, representing a gradient of watersheds with differing dominant land‐use types and anthropogenic impacts, to evaluate invasive and native plant response to herbicide management. The focal invader, Phragmites australis (common reed), is one of the most aggressive and pervasive invasive plants in North American wetlands. We found that with multiyear herbicide treatments, it was possible to greatly reduce Phragmites across an array of subestuaries while increasing the cover and quality of native plant communities. Yet, by the end of the study, plant community composition in all Phragmites‐managed sites remained distinct from, even if composition was shifting toward, reference sites. There was also large inter‐site variation in the vegetation responses related to site environmental conditions and subestuary vegetation conditions. We uncovered specific aspects of the surrounding landscape that were linked to improved vegetation recovery—the species richness and conservation value of nearby wetlands. Results from this five‐year experiment conducted at multiple sites in Chesapeake Bay inform what is possible for management, particularly in more degraded landscapes and sites where setting realistic expectations and pragmatic goals will be essential. Assessing environmental and vegetation conditions of the site and surrounding landscape prior to commencing invasive species management is critical to predict the time and effort required to achieve restoration goals.

Prescribed fire in longleaf pine ecosystems: fire managers’ perspectives on priorities, constraints, and future prospects

BackgroundProjected trajectories of climate and land use change over the remainder of the twenty-first century may result in conditions and situations that require flexible approaches to conservation planning and practices. For example, prescribed burning is a widely used management tool for promoting longer-term resilience and sustainability in longleaf pine ecosystems of the southeastern United States, but regional stressors such as climatic warming, changing fire conditions, and an expanding wildland-urban interface may challenge its application. To facilitate the development of fire management strategies that account for such changes, we surveyed nearly 300 fire managers to elicit information on the criteria used for prioritizing burn sites, current burning practices and constraints, and expectations for changes in burning opportunities, including those pertaining to climate change and urban growth.ResultsRespondents noted that their most common criteria for selecting longleaf pine stands for burning were fire history, ecosystem health, and fuel reduction, with the presence of threatened and endangered species also given priority by public land managers. Many respondents (38%) cited recent burn frequencies that fall short of historic burn intervals. Barriers to burning included legal, institutional, and managerial constraints, such as proximity to human developments, public concerns, and risk aversion, as well as environmental and resource constraints, including weather, air quality restrictions, and lack of personnel, equipment, or funding. Roughly half of all respondents expect that opportunities to burn will be reduced over the next 30 years, particularly during the growing season. Fire manager perceptions of factors that will limit prescribed burning in the future include a similar suite of constraints, many of which will be affected by projected regional changes in land use and climate.ConclusionsOn an organizational level, burn window availability and resource limitations constrain prescribed burning practices. More broadly, policy and legal frameworks coupled with trends in urbanization and climate change are expected to interact with operational constraints to challenge managers’ abilities to implement landscape-scale burning strategies and achieve restoration goals. Additional research and engagement with fire managers are needed to investigate opportunities for introducing policy flexibility, leveraging shared management interests, and developing creative solutions to expand burning opportunities.

Forest restoration by direct seeding: a global bibliometric analysis

Direct seeding has been suggested to be a highly cost‐efficient system for forest restoration but is still not applied on a large scale worldwide. Thus, to improve the knowledge surrounding the application of this system, I conducted a global bibliometric analysis about forest restoration by direct seeding. Based on a literature search of three online databases (Web of Science, Scopus, and Google Scholar), I found 81 peer‐reviewed articles related to field experiments testing direct seeding for forest restoration. Each article was analyzed according to the following aspects: publication years, countries, continents, forest types, stages of restoration, journals, and authors. The results showed an increase in the number of articles published in recent years but a still low number of studies conducted to test the application of the system. These included field studies from a number of tropical and temperate countries worldwide, with a concentration of studies in Brazil and United States. Monitoring forests established by direct seeding is rare. A few researchers have paid special attention to the development of the field, and a few journals have published three or more articles on this topic. Overall, this study concludes that the application of direct seeding for forest restoration is a promising area for research, as the field is still little studied and has great potential to help achieve restoration goals. Furthermore, the results show trends and gaps that should be considered in future research to improve the application of direct seeding around the world.

Using biodiversity response for prioritizing participants and service provisions in a payment-for-water-storage program in the Everglades basin

Hydrological changes can lead to biodiversity responses that are complex and challenging to quantify. We present a framework that uses biodiversity as a criterion to address “where to buy” and “how much to buy” in a payment-for-environmental-services (PES) program focused on water storage service in the Everglades basin, USA. The PES program was designed to pay for added water storage on private cattle ranchlands by raising the spillage level in drainage control structures to reduce surface flows. We predicted that increased hydration of previously drained wetlands would benefit biodiversity, a previously unquantified but desirable co-benefit of the original program, and that a PES program offering bundled services (e.g., storage and biodiversity) can better achieve restoration goals. We quantified desirable biodiversity services (abundance of native flora and fauna such as cover of wetland and forage plants, and abundance of fishes, amphibians, and macroinvertebrates), dis-services (e.g., abundance of invasive plants and mosquitos), and hydrologic signatures (e.g., wetland water depth, inundation area and duration) at four ranches to develop eco-hydrological relationships (models) between hydrological changes and biodiversity responses. Next, a hydrologic model (MIKE-SHE/MIKE-11) was used to predict surface and subsurface water levels and flows and resulting wetland hydrologic signatures for 13 water storage alternatives on the ranches, which were used as example PES proposals. A decision-support-system (DSS) was developed to integrate (i) storage predicted by the hydrologic model, (ii) biodiversity responses predicted by eco-hydrologic models, and (iii) a user-defined preference scheme to assign importance weights to storage, biodiversity, and implementation cost. The DSS calculated a cumulative score for ranking PES proposals. By considering desirable services and dis-services, stakeholders can decide on their preferred level of services, e.g., buyer(s) may settle for less storage if there is a gain in desirable biodiversity. The DSS can identify trade-offs among services, helping stakeholders negotiate.

Low passive restoration potential following invasive woody species removal in oak woodlands

The restoration of oak woodlands often requires removal and management of woody invasive plants. This can trigger germination of the soil seed bank, which can alter restoration trajectories. In degraded deciduous woodlands generally, it is unclear whether the soil seed bank will contribute native plant material in sufficient quantities to help achieve restoration goals and allow practitioners to rely on passive restoration without supplemental seeding. To support restoration decision‐making around passive or active restoration in three Rhamnus cathartica‐invaded forest preserves in the Chicago region, we asked: (1) Does the soil seed bank differ from standing aboveground vegetation at reference and unrestored sites? and (2) Can the species richness, Shannon diversity, floristic quality (measured by abundance‐weighted mean coefficients of conservatism), or density of germinable seeds of native species in the soil seed bank be predicted by a site's restoration status (reference or unrestored)? We found that species composition differed significantly between aboveground vegetation and the soil seed bank at reference and unrestored sites, with a significant interaction between restoration status and location. Despite high variation among the three forest preserves, restoration status also predicted native species richness, diversity, floristic quality, and seed density in the soil seed bank, with unrestored sites significantly lower than reference sites in all measures. Results suggest that reintroduction of native seeds will be necessary to fully restore desired native plant communities in oak woodlands following the removal of invasive woody plants.

Marine restoration governance arrangements: Issues of legitimacy

AbstractA new motivation for marine restoration has been observed, associated with the dissatisfaction with current marine restoration governance arrangements (MRGAs). An MRGA consists of alliances of public and private actors (coalitions) who, through their common conceptualisation of the problem (discourses), try to influence and design marine restoration activities while considering the rules of decision‐making, and the management of limited resources. Emerging MRGAs rise in parallel to existing ones and aim to contribute to the same goals or show another way of reaching those goals. This phenomenon raises questions of legitimacy both for the emerging and the existing arrangement. Building on existing literature, this paper proposes an analytical framework to simultaneously explore input, throughput and output legitimacy as three essential pre‐conditions of legitimacy for MRGAs. The framework is tested in three European cases of MRGAs that were part of the European Union MERCES project (http://www.merces-project.eu/). Analysis showed that actors who are influential in achieving restoration goals, and also those who are impacted by restoration actions, should be involved in the MRGAs (input legitimacy); actors within MRGAs should establish and follow procedures for decision‐making that are both transparent and clear (throughput legitimacy); and actors within MRGAs need to establish a common understanding of restoration, of the goal to reach and of the related uncertainties (output legitimacy). Awareness of these pre‐conditions allows actors internal and external to MRGAs to address aspects that give legitimacy to restoration actions. It also creates a language that allows actors to engage in discussion on legitimacy that goes beyond the mere application of the rule of law.

Biophysical Impacts of Historical Disturbances, Restoration Strategies, and Vegetation Types in a Peatland Ecosystem

AbstractRewetting of disturbed peatlands is an important restoration strategy for climate change mitigation. Previous work primarily focuses on the biogeochemical processes altered by rewetting and few studies have investigated the biophysical impacts, which can diminish or amplify biogeochemical effects beyond the ecosystem scale. We used a paired flux tower approach in a restored peatland to collect year‐round eddy covariance data to assess the biophysical impacts of disturbance and management practices. The first site was actively rewetted and is characterized by Sphagnum and white beak‐rush with patches of open water. The second site represents a disturbed ecosystem, which underwent natural regeneration and is dominated by scrub pine, Sphagnum, and low shrubs. We found that the actively restored site had higher net radiation compared to the second site due to more surface water ponding; however, the higher aerodynamic conductance at the passively restored site contributed to enhanced daytime turbulent fluxes, and hence, both sites had similar aerodynamic temperatures during the daytime. The actively restored site experienced warmer nighttime and seasonal aerodynamic temperature as much of the excess radiation during the day was stored in the water column and released at night. To achieve restoration goals, higher water tables are now maintained throughout large sections of the bog. The study implies that water table manipulation has the potential to minimize greenhouse gas emissions from the bog, thereby allowing the biophysical impacts of peatland restoration to enhance the biogeochemical benefits. Therefore, it is important to consider both biophysical and biogeochemical changes in peatland restoration management.

Identification of restoration species for early roadcut slope regeneration using functional group approach

Current restoration protocols for roadside cut slopes in South Korea involve hydroseeding with exotic species to achieve early greening and soil stabilization. However, exotic species can negatively affect adjacent native ecosystems. This study investigated the functional traits of early colonizers in slope restoration and surrounding environments to inform restoration methods that generate similar communities as those of native ecosystems. Slope vegetation (species density, species cover, upperstory species, canopy cover) and environment (aspect, angle, soil properties) were surveyed from the road edge to the forest boundary, and were classified as three distinct zones: a hydroseeded slope, a transition zone, and the forest edge. Naturally occurring species were classified into functional groups to examine dominant traits during early colonization. Hemicryptophyte or geophyte forest species and forest interior woody species were well established and dominant in transition zones and cut slopes. Potential native species for slope restoration can be identified by examining functional group species in the adjacent forest. These native species can achieve restoration goals and block invasive species in the same functional group. Festuca arundinacea (tall fescue), which is reported as an invasive alien species, rapidly spread after introduction for restoration. Thus, continuous monitoring for impact on native communities is required after sowing invasive alien species. Future slope restoration should consider native woody species and perennial forest sedge species that develop rhizomes, and reconsider the use of tall fescue. This study indicates that cut slopes can be appropriately managed to enhance the quality of habitats for native species.

Urbanization and stream ecosystems: the role of flow hydraulics towards an improved understanding in addressing urban stream degradation

Catchment urbanization is widely recognised as a primary driver of stream degradation by increasing stormwater runoff, which causes major changes to key ecosystem processes. Reinstating the “natural” hydrogeomorphic conditions is central in designing successful, self-sustaining restoration actions; however, addressing urban stream degradation by re-establishing the hydrogeomorphic conditions remains a challenge, and comparatively limited measurable progress has been observed, particularly in achieving ecological objectives. This review articulates that stream restoration goals might be better achieved when management measures take a broader approach that considers anticipated hydraulic condition effects that liaise relationships between flow and ecology. The study argues that fluvial systems are characterised by complex and dynamic ecosystem processes primarily governed by the hydraulic conditions (e.g., velocity, depth, shear stress); thus, as the practice of addressing urban stream restoration becomes increasingly common, it is critical to explore and understand the anticipated response of the hydraulic conditions. It describes how hydraulic regime consideration provides further opportunity for a holistic approach to urban stream management given their capacity to account for multiple ecological and geomorphic objectives. This review suggests that developing suitable flow–biota–ecosystem processes nexus is critical to addressing urban stream degradation, and hydraulic consideration in restoration actions provides an important step towards that. It discusses opportunities to evolve management actions to achieve restoration goals by highlighting how the management of the two key levers (addressing altered flow regime and morphology) to improve the hydraulic conditions can help to address the urban stream disturbance.

Native Plant Production in Chile. Is It Possible to Achieve Restoration Goals by 2035?

Facing rapid loss of biodiversity as a consequence of climate change, Chile has formally pledged to restore 600,000 ha of native forest by 2035. This effort, however, has not considered the amount and quality of native plants required to meet this pledge. Thus, we examined data collected during the annual, government-conducted census of small- and medium-sized nurseries from central Chile, which account for 78% of the nation’s total plant production, to assess if current production is sufficient to meet Chile´s restoration needs. We coupled this with data collected during our series of ongoing research projects to determine if nurseries are currently meeting minimum seedling quality standards based on morpho-physiological attributes. Our four-year analysis (2016–2019) shows that the number of native seedlings has increased by only 4%, but because only 19% of nursery managers have training, just 29% of all seedlings meet quality criteria for restoration. Thus, under the current rate and quality of plant production, meeting restoration pledges desired by the year 2035 would not be achieved until 2181. This timeline can be accelerated through an urgent expansion of nursery space, implementation of a continuous program for technology and knowledge transference, and strong support through governmental policies.

Priority effects and ecological restoration

Priority effects refer to the order or timing of species arrival, including how species that arrive early at a site either positively or negatively affect establishment, growth, or reproduction of species that arrive later. Despite the clear implications of priority effects for ecological restoration, there have been no reviews of how and where priority effects have been studied and the extent to which findings can be applied to restoration. Here, we systematically review the literature on priority effects by (1) synthesizing information from papers that compared simultaneous and nonsimultaneous planting or sowing; (2) discussing the mechanisms through which priority effects operate, (3) considering how these mechanisms might be manipulated to achieve restoration goals; and (4) highlighting future research needed to improve the use of priority effects in restoration. In a term‐targeted search, we found 43 studies that experimentally manipulated the order of arrival of different species. Overall, these concluded that even small delays in arrival time, as opposed to simultaneous arrival of species, can promote differences in subsequent community composition as well as ecosystem functions. There were very few studies on the long‐term stability of these priority effects, and the majority were conducted in temperate grasslands. Our findings suggest that creating alternative vegetation states via priority treatments is a promising avenue for restoration. However, for the concept to be best operationalized for restoration, we need research in more ecosystems that are priorities for restoration, and treatments that are followed over extended time periods.

Do early trends in oak barrens fire treatment predict later outcomes? Insights from three decades of vegetation monitoring

BackgroundVegetation structure, species diversity, and composition have been monitored at a fire-treatment and a fire-free control unit of a dry oak barrens and woodland complex in southern Illinois, USA, over a 29-year period and five burns. The restoration hypothesis is that fire management would result in different trends for vegetation parameters of conservation interest between fire treatment and control units, that before–after differences would be greater with fire management, and that early trends provide a reliable predictor for later outcomes. This study examines effectiveness of management in achieving restoration goals and uses response to the first two burns and monitoring results over the first seven years as an estimation period to test whether early trends with fire treatment are a reliable predictor for outcomes following three additional burns over the following 22 years.ResultsTrends differed between fire-treatment and control units for all parameters measured, and before–after differences were greater at the fire treatment unit. However, trends at the fire-treatment unit during the estimation period were a poor predictor of later outcomes. Tree density and basal area declined more than expected while ground-layer species density, richness, diversity, and percent cover did not keep pace with expectations of increase. Trends at the control unit were more predictable; however, tree basal area declined more than expected, possibly due to an outbreak of rapid white oak mortality disease, and decline of ground-layer species density was less than predicted from the early estimation period.ConclusionsResults suggested that fire alone can be effective at restoring woodland and barrens natural areas and that a fire return interval of about every four years would be optimal for maintaining composition and diversity in this specific oak barrens habitat. However, burns followed immediately by severe drought possibly can have negative interactions, resulting in declines of ground-layer species diversity.

Key Principles for Managing Recovery of Kelp Forests through Restoration

AbstractThere is increasing interest in mitigating the loss of kelp forests through restoration, but this has received scant attention relative to other coastal habitats. We evaluate current knowledge centered on key restoration principles to provide guidelines for best practice in kelp restoration. The cause and scale of degradation is fundamental in determining if kelp can be restored and the methods required to promote reestablishment. Removal of stressors may be adequate to achieve restoration goals where degradation is not too widespread or acute. Extensive losses of kelp forests will often require active reseeding of areas because of the low dispersal ability of many kelp species. Restoration efforts have generally taken a trial-and-error approach at experimental scales to develop techniques for establishing individuals. Furthermore, studies that inform cost–benefit analysis and the appropriate spatial scales for restoration of sustainable kelp forests are urgently needed for prioritizing and scaling up restoration efforts globally.

What makes ecosystem restoration expensive? A systematic cost assessment of projects in Brazil

Limited funding is a major barrier to implementing ambitious global restoration commitments, so reducing restoration costs is essential to upscale restoration. The lack of rigorous analyses about the major components and drivers of restoration costs limit the development of alternatives to reduce costs and the selection of the most cost-effective methods to achieve restoration goals. We conducted detailed restoration cost assessments for the three most widespread biomes in Brazil (Amazon, Cerrado, and Atlantic Forest) and estimated the restoration costs associated with implementing Brazil’s National Plan for Native Vegetation Recovery (12M hectares). Most surveys (60–90%) reported using the costly methods of planting seedlings or sowing seeds throughout the site, regardless of the biome. Natural regeneration and assisted regeneration approaches were an order of magnitude cheaper but were reported in <15% of projects. The vast majority of tree planting and direct seeding costs were incurred during the implementation phase, and nearly 80% of projects ended maintenance within 30 months. We estimated a price tag of US$0.7-1.2 billion per year until 2030 to implement Brazil’s restoration plan depending on the area that recovers through natural regeneration. Our results offer valuable insights for developing strategies to make restoration cheaper and to increase its cost-effectiveness for achieving diverse benefits in Brazilian ecosystems. Our survey also provides a starting point for sound assessments of restoration costs and their drivers in other biomes, which are needed to reduce the financial barriers to scaling up restoration at a global scale.

Can we condition native plants to increase drought tolerance and improve restoration success?

A common method in ecological restoration is the transplanting of nursery-grown seedlings to the field and, with proper resources, this technique can be highly successful. However, stressors such as drought may negatively impact plant performance and restoration success, especially in dryland ecosystems. Furthermore, increasing environmental change may hamper the ability of practitioners to restore native vegetation. A growing body of research suggests that exposing plants to a stressor may improve tolerance to subsequent stress events later in life. We sought to understand if such a phenomenon could be exploited in order to improve plant drought-tolerance and aid native plant restoration in southern California. In a multi-phase experiment, we first exposed seedlings of native perennials to episodic drought and then later compared the response of these plants to a second drought event to that of well-watered controls. We also transplanted replicates of both treatments to a restoration site in the field to test whether exposure to drought as a seedling could improve plant performance. Plant species responded to drought differently, with species exhibiting the full range of positive, neutral, and negative responses to temporal variability in water stress. However, some species appeared to benefit from drought preconditioning, exhibiting greater growth and increased water-use efficiency compared to well-watered plants. This suggests that simple applications of stress treatments could improve plant growth and stress tolerance, but the success of this method is likely very species specific. Restoration practitioners should consider conducting pilot studies with target plant species to better understand if this technique could assist in achieving restoration goals.

Season of burn effects on vegetation structure and composition in oak-dominated Appalachian hardwood forests

Previous research indicates that low-intensity single or multiple prescribed burns in oak-dominated upland hardwood forest do not substantially change stand structure or species composition of the arborescent regeneration layer, leading managers and ecologists to suggest that burns during the growing-season may better achieve restoration goals. We examined season of burn effects on dry-mesic oak-hickory forests in the southern Appalachian Mountains, North Carolina. Treatments included: (1) control (CON); (2) dormant-season burn (DSB), and (3) growing-season burn (GSB). Prior to burning and again after three growing seasons post-burn, we inventoried the forest overstory (stems ≥ 25 cm dbh), subcanopy (stems ≥ 5 and <25 cm dbh), sapling (stems ≥ 1.2 m and < 5 cm dbh), and seedling (stems < 1.2 m) strata. We found no effect of prescribed fire, regardless of burn season, on stem density or basal area of the overstory and subcanopy strata, leaving the light environment in the forest understory relatively unchanged. In general, treatment effects on the sapling and seedling layers were limited to the mesophytic species group, where seedling density post-burn was greater in GSB than both CON and DSB and sapling density post-burn was lower than pre-burn in DSB and GSB. Mortality of individually-tagged seedlings three growing seasons post-burn did not differ among treatments for the red oak, white oak, red maple, mesophytic, and pyrophilic species groups, and averaged 29.0, 28.5, 31.8, 29.3, and 25%, respectively. This study provides support for the notion that a single fire in a closed-canopy oak-hickory forest has little effect on forest structure or regeneration composition, regardless of the burn season. Prescribed fires should be repeated in subsequent years to assess whether the effects of burn season are amplified under a periodic burning regime.

Restoration and repair of Earth's damaged ecosystems.

Given that few ecosystems on the Earth have been unaffected by humans, restoring them holds great promise for stemming the biodiversity crisis and ensuring ecosystem services are provided to humanity. Nonetheless, few studies have documented the recovery of ecosystems globally or the rates at which ecosystems recover. Even fewer have addressed the added benefit of actively restoring ecosystems versus allowing them to recover without human intervention following the cessation of a disturbance. Our meta-analysis of 400 studies worldwide that document recovery from large-scale disturbances, such as oil spills, agriculture and logging, suggests that though ecosystems are progressing towards recovery following disturbances, they rarely recover completely. This result reinforces conservation of intact ecosystems as a key strategy for protecting biodiversity. Recovery rates slowed down with time since the disturbance ended, suggesting that the final stages of recovery are the most challenging to achieve. Active restoration did not result in faster or more complete recovery than simply ending the disturbances ecosystems face. Our results on the added benefit of restoration must be interpreted cautiously, because few studies directly compared different restoration actions in the same location after the same disturbance. The lack of consistent value added of active restoration following disturbance suggests that passive recovery should be considered as a first option; if recovery is slow, then active restoration actions should be better tailored to overcome specific obstacles to recovery and achieve restoration goals. We call for a more strategic investment of limited restoration resources into innovative collaborative efforts between scientists, local communities and practitioners to develop restoration techniques that are ecologically, economically and socially viable.