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Forest restoration is increasingly heralded as a global strategy to conserve biodiversity and mitigate climate change, yet long-term studies that compare the effects of different restoration strategies on tree recruit demographics are lacking. We measured tree recruit survival and growth annually in three restoration treatments—natural regeneration, applied nucleation and tree plantations—replicated at 13 sites in southern Costa Rica—and evaluated the changes over a decade. Early-successional seedlings had 14% higher survival probability in the applied nucleation than natural regeneration treatments. Early-successional sapling growth rates were initially 227% faster in natural regeneration and 127% faster in applied nucleation than plantation plots but converged across restoration treatments over time. Later-successional seedling and sapling survival were similar across treatments but later-successional sapling growth rates were 39% faster in applied nucleation than in plantation treatments. Results indicate that applied nucleation was equally or more effective in enhancing survival and growth of naturally recruited trees than the more resource-intensive plantation treatment, highlighting its promise as a restoration strategy. Finally, tree recruit dynamics changed quickly over the 10-year period, underscoring the importance of multi-year studies to compare restoration interventions and guide ambitious forest restoration efforts planned for the coming decades. This article is part of the theme issue ‘Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration’.

Reversing large-scale habitat degradation and deforestation goes beyond what can be achieved by site-level ecological restoration and a landscape ecology perspective is fundamental. Here we assess the relative importance of tree cover and its configuration on forest-dependent birds and late-successional tree seedlings in restoration sites in southern Costa Rica. The abundance and species richness of birds increased in landscapes with more corridors, higher tree cover, and lower levels of fragmentation, highlighting the importance of riparian corridors for connectivity, and continuous tree cover as suitable habitat. Landscape variables affected abundance and species richness of seedlings similarly, but effects were weaker, possibly because seedlings face establishment limitation in addition to dispersal limitation. Moreover, the scale of landscape effects on seedlings was small, likely because proximal individual trees can significantly influence recruitment in restoration plots. Results underscore the importance of incorporating landscape-level metrics to restoration projects, as knowing the extent, and how the landscape may affect restoration outcomes can help to infer what kind of species will arrive to restoration plots., Scientific Reports, 12 (1), ISSN:2045-2322

Reintroduction is an increasingly common practice to conserve and recover threatened and endangered plant species, so understanding how practitioners view their work and identifying persistent resource mismatches are key to the long-term viability of these listed species. We interviewed practitioners involved in reintroduction projects for 14 species in the state of California to understand (1) how they defined recovery; (2) their assessment of the likelihood of recovery; (3) what advice they would share with other practitioners to improve reintroduction efforts; and (4) what resources could make future projects more successful. Practitioners’ definitions of recovery aligned with ecological theory and emphasized the importance of self-sustaining populations and large populations, as well as the presence of multiple populations. However, most practitioners felt that recovery was unlikely or did not think the species they worked with should or would be de-listed without the guarantee of perpetual future interventions. Practitioners thought that studying basic biology and natural history, using experiments to determine the best techniques, and repeatedly planting populations were important to project success. However, practitioners also felt they were missing critical resources, including long-term funding for implementation and maintenance, successful and positive relationships between members of the practitioner-agency-scientist-landowner nexus, and assurances/safe harbor agreements for experimental populations. Overall, rare plant reintroductions are complicated by persistent mismatches in timing and goals, but some individuals have been able to successfully navigate these challenges. Longer duration funding mechanisms for monitoring and maintenance and better data handling, storage, and dissemination would benefit future projects.

Author(s): Holl, Karen D; Reid, J Leighton; Cole, Rebecca J; Oviedo-Brenes, Federico; Rosales, Juan A; Zahawi, Rakan A

Conservation and restoration of riparian vegetation in agricultural landscapes has had mixed success at protecting in‐stream habitat, potentially due to the mismatch between watershed‐scale impacts and reach‐scale restoration. Prioritizing contiguous placement of small‐scale restoration interventions may effectively create larger‐scale restoration projects and improve ecological outcomes. We performed a multi‐site field study to evaluate whether greater linear length of narrow riparian tree corridors resulted in measurable benefits to in‐stream condition. We collected data at 41 sites with varying upstream tree cover nested within 13 groups in rangeland streams in coastal northern California, United States. We evaluated the effect of riparian tree corridor length on benthic macroinvertebrate communities, as well as food resources, water temperature, and substrate size. Sites with longer riparian corridors had higher percentages of invertebrates sensitive to disturbance (including clingers and EPT taxa) as well as lower water temperatures and less fine sediment, two of the most important aquatic stressors. Despite marked improvement, we found no evidence that macroinvertebrate communities fully recovered, suggesting that land use continued to constrain conditions. The restoration of long riparian corridors may be an economically viable and rapidly implementable technique to improve habitat, control sediment, and counter increasing water temperatures expected with climate change within the context of ongoing land use.

In degraded tropical landscapes, lack of seed dispersal can strongly limit recovery, and restoration interventions can overcome this barrier by attracting dispersers. However, seed dispersal patterns are typically studied over short time periods, thus the influences of temporal and spatial variability on seed arrival cannot be teased apart. The choice of management approach can have important implications for restoration-mediated community reassembly. Accordingly, we used a 3.5-year record of seed deposition in pre-montane tropical wet forest in southern Costa Rica to examine how seed arrival differed between passive (natural regeneration) and active (applied nucleation, plantation) restoration after a decade of recovery, compared to remnant forest. We investigated: (a) how restoration treatments affected seed deposition rates and community composition; (b) how within-plot heterogeneity of animal-dispersed seed deposition varied by intervention; and (c) how interannual variation influenced animal-dispersed seed arrival across treatments. Overall seed rain composition and diversity in restoration treatments was converging towards, but still differed substantially from, remnant forest (89.7%, 86.6% and 76.3% Shannon diversity recovered in applied nucleation, plantation and natural regeneration respectively). Within-plot animal-dispersed seed heterogeneity was similar in applied nucleation and remnant forest, 27.0% more heterogeneous in applied nucleation than plantation, and equivalent when comparing natural regeneration to either applied nucleation or plantation. In contrast to active interventions, animal-dispersed tree and shrub communities did not differ year to year in natural regeneration, which may promote the assembly of relatively homogeneous plant communities at this successional stage. Synthesis and applications. Compared to natural regeneration, active restoration interventions: (a) catalysed the recovery of seed diversity (overall Shannon diversity 17.5% and 13.4% higher in applied nucleation and plantation respectively), (b) shifted seed community composition towards remnant forest more rapidly (overall Shannon diversity 13.4% and 10.2% closer), (c) almost doubled the proportion of later-successional tree species arriving, and (d) had seed communities that differed year to year—a pattern not observed in natural regeneration. Finally, applied nucleation was the only intervention where seed arrival was as spatially heterogeneous as remnant forest, highlighting that this approach may facilitate the recovery of specific natural dispersal processes. Universidad de Costa Rica/[809-B8-A15]/UCR/Costa Rica National Science Foundation/[05-15577]/NSF/Estados Unidos National Science Foundation/[09-18112]/NSF/Estados Unidos National Science Foundation/[14-56520]/NSF/Estados Unidos UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigaciones en Productos Naturales (CIPRONA)

Remnant trees and forest fragments in agricultural landscapes can be important sources of propagules to facilitate forest recovery. However, many studies simply quantify forest cover in the surrounding landscape as a percentage, with little attention given to species composition, and subsequently fail to detect an effect on recruitment patterns. We assessed the relative importance of the spatial distribution and life-history traits of 77 tree species on recruitment patterns at a landscape scale in a well-replicated long-term restoration study in southern Costa Rica. We censused and mapped potential mother trees in a 100-m buffer surrounding eight replicate restoration plots and quantified respective tree recruits within each plot. We assessed how mother tree abundance, species life-history characteristics (seed size, dispersal mode), tree size (DBH, height) and distance to restoration plot affected recruitment at coarse (plot: 50 × 50 m) and fine (quadrat: 3 × 3 m) spatial scales. The presence of a mother tree within 100 m of a restoration plot resulted in a 10-fold increase in potential mean recruitment. Mother tree abundance was also an important driver of recruit density, and particularly so for large-seeded (≥ 5 mm) zoochorous species with a fivefold increase in recruit density across the observed mother tree abundance range. An interaction between mother tree abundance and proximity demonstrated that the effect of mother tree abundance on recruit density was important but waned with increasing distance from restoration plots. At the fine spatial scale, proximity was uniformly important; height and DBH of the closest potential mother tree also affected recruit abundance but responses differed by seed size. Results highlight the importance of remnant vegetation composition to the recovery of adjacent degraded habitats, underscoring the outsized role nearby remnant forest and isolated trees can play for the persistence of localized biodiversity., Ecography, 44 (12), ISSN:0906-7590, ISSN:1600-0587

A growing number of initiatives at global, regional and national scales propose to plant millions, billions or even trillions of trees as a simple solution to resolve complex environmental problems. However, tree planting is much more complicated than it seems. We summarize the multifaceted decision‐making process needed and offer guidelines to increase the success of the proposed ambitious efforts to increase tree cover world‐wide. Given the varied definitions of and motivations for tree planting, it is critical that stakeholders work together to clearly define the biophysical and socioeconomic goals of each project. Then a series of questions must be addressed about where and how (e.g. planting trees vs. allowing for natural forest regrowth) to most effectively achieve these goals and minimize unintended negative consequences, as well as how, when and by whom success of efforts will be evaluated. Key guidelines to successfully increase tree cover include: (a) first addressing the underlying drivers of deforestation; (b) integrating decision‐making across scales from local to global; (c) tailoring tree planting strategies to clearly stated project goals and planning, adaptively managing and evaluating success over a sufficiently long timeframe; (d) focusing on the forest ecosystem as a whole, and not just the trees; (e) coordinating different land uses and (f) involving stakeholders at all stages of the planning process. Synthesis and applications. Tree planting, along with other strategies to increase tree cover in appropriate locations and contexts, can make a valuable contribution to ensuring the ecological and social well‐being of our planet in coming decades, but only if these efforts are considered as one component of multifaceted solutions to complex environmental problems and are carefully planned, implemented and monitored over a sufficiently long time‐scale with stakeholder engagement and broader consideration of socio‐ecological complexities.

Successful restoration of California terrestrial ecosystems requires knowledge of seed germination rates for a diversity of native species. We quantified greenhouse germination of 25 native perennial forbs, shrubs, and grasses collected coastally near Santa Cruz, CA for restoration at the Younger Lagoon Reserve and nine annual forb species from interior grasslands at Pinnacles National Park. Seeds of most species were collected in multiple years. Twenty-seven of our 34 study species had at least 25% germination without complicated germination triggers. All but two of the 13 species that were collected in ≥3 years and germinated showed significant interannual variation in germination; seven species had a trend of decreasing percent germination with increasing age. These species- and collection-year specific results indicate a necessity to test seed stock when possible prior to seeding to increase restoration success, and highlight the importance of following best practices for seed collection and storage.

To constrain global warming, we must strongly curtail greenhouse gas emissions and capture excess atmospheric carbon dioxide1,2. Regrowing natural forests is a prominent strategy for capturing additional carbon3, but accurate assessments of its potential are limited by uncertainty and variability in carbon accumulation rates2,3. To assess why and where rates differ, here we compile 13,112 georeferenced measurements of carbon accumulation. Climatic factors explain variation in rates better than land-use history, so we combine the field measurements with 66 environmental covariate layers to create a global, one-kilometre-resolution map of potential aboveground carbon accumulation rates for the first 30 years of natural forest regrowth. This map shows over 100-fold variation in rates across the globe, and indicates that default rates from the Intergovernmental Panel on Climate Change (IPCC)4,5 may underestimate aboveground carbon accumulation rates by 32 per cent on average and do not capture eight-fold variation within ecozones. Conversely, we conclude that maximum climate mitigation potential from natural forest regrowth is 11 per cent lower than previously reported3 owing to the use of overly high rates for the location of potential new forest. Although our data compilation includes more studies and sites than previous efforts, our results depend on data availability, which is concentrated in ten countries, and data quality, which varies across studies. However, the plots cover most of the environmental conditions across the areas for which we predicted carbon accumulation rates (except for northern Africa and northeast Asia). We therefore provide a robust and globally consistent tool for assessing natural forest regrowth as a climate mitigation strategy. A one-kilometre-resolution map of aboveground carbon accumulation rates of forest regrowth shows 100-fold variation across the globe, with rates 32% higher on average than IPCC estimates.

Tree planting must be carefully planned and implemented to achieve desired outcomes

Restoration frequently aims to improve native species biodiversity at a site, but practitioners have limited resources. In diverse ecosystems, the selective use of certain guilds or species can come at the cost of species that are more challenging to incorporate, resulting in the overall homogenization of the ecosystem and a relative loss of biodiversity. We surveyed practitioners who restore California prairies to understand their use of native annual forbs, an important component of the biodiversity in this ecosystem. We found that practitioners preferentially planted native perennial species, mainly grasses. Despite practitioners' recognition of the high conservation value of native annual forbs, they were hesitant to include this guild in their planting palettes because of high costs, low and unpredictable establishment, and lack of seed. We recommend that California annual prairie forbs be seeded in multiple years to enhance establishment, and that monitoring targets be designed to better reflect the high variability in interannual abundance of native annual forbs. These issues are not unique to California prairie, and more broadly, restoration objectives and research across a range of ecosystems should prioritize guilds that are more challenging to establish but are of high conservation concern.

QUESTIONS: Natural regeneration is increasingly recognized as a potentially cost‐effective strategy to reach ambitious forest landscape restoration targets, but rates of recovery are notoriously variable. We asked how well initial habitat conditions after cessation of agriculture predict forest recovery after nearly a decade. We aimed to provide land managers with general rules of thumb to assess when it is necessary to invest resources in active restoration, such as tree planting, to accelerate forest recovery. LOCATION: Coto Brus County, Puntarenas, Costa Rica. METHODS: We compiled data on initial vegetation structure, soil nutrients, prior land‐use history and surrounding forest cover at 13 sites. After 8.5 years, we measured vegetation indicators commonly used to assess forest recovery, namely amount of canopy closure and number and diversity of woody recruits. RESULTS: Two variables, grass cover and canopy closure, measured 1.5 years after site abandonment, explained 47–87% of five of the six response variables after 8.5 years; recovery was faster in sites with lower grass cover and higher canopy closure initially. Waiting an additional year to measure initial vegetation variables did not improve model fit. Time since the original forest was cleared explained 62% of change in canopy cover, whereas percentage of surrounding forest cover, length of pasture use and soil variables explained minimal additional variation. CONCLUSIONS: Our results suggest that two easily measurable vegetation variables can provide guidance to land managers and policy makers about where to invest scarce restoration resources to facilitate forest recovery.

Author(s): Lanuza, Oscar; Casanoves, Fernando; Zahawi, Rakan A; Celentano, Danielle; Delgado, Diego; Holl, Karen D

Author(s): Brancalion, Pedro HS; Amazonas, Nino T; Chazdon, Robin L; van Melis, Juliano; Rodrigues, Ricardo R; Silva, Carina C; Sorrini, Taisi B; Holl, Karen D

Both dispersal- and niche-based factors can impose major barriers on tree establishment. Our understanding of how these factors interact to determine recruitment rates is based primarily on findings from mature tropical forests, despite the fact that a majority of tropical forests are now secondary. Consequently, factors influencing seed limitation and the seed-to-seedling transition (STS) in disturbed landscapes, and how those factors shift during succession, are not well understood. We used a 3.5-yr record of seed rain and seedling establishment to investigate factors influencing tree recruitment after a decade of recovery in a tropical wet forest restoration experiment in southern Costa Rica. We asked (1) how do a range of restoration treatments (natural regeneration, applied nucleation, plantation), canopy cover, and life-history traits influence the STS and (2) how do seed and establishment limitation (lack of seed arrival or lack of seedling recruitment, respectively) influence vegetation recovery within restoration treatments as compared to remnant forest? We did not observe any differences in STS rates across restoration treatments. However, STS rates were lowest in adjacent later successional remnant forests, where seed source availability did not highly limit seed arrival, underscoring that niche-based processes may increasingly limit recruitment as succession unfolds. Additionally, larger-seeded species had consistently higher STS rates across treatments and remnant forests, though establishment limitation for these species was lowest in the remnant forests. Species were generally seed limited and almost all were establishment limited; these patterns were consistent across treatments. However, our results suggest that differences in recruitment rates could be driven by differential dispersal to treatments with higher canopy cover. We found evidence that barriers to recruitment shift during succession, with the influence of seed limitation, mediated by species-level seed deposition rates, giving way to niche-based processes. However, establishment limitation was lowest in the remnant forests for large-seeded and late successional species, highlighting the importance of habitat specialization and life-history traits in dictating recruitment dynamics. Overall, results demonstrate that active restoration approaches such as tree planting catalyze forest recovery, not only by decreasing components of seed limitation, but also by developing canopy cover that increases establishment rates of larger-seeded species.

To meet their large-scale forest and landscape restoration targets, countries must find ways to accommodate areas for conservation alongside agricultural production. In some pasture-dominated regions of Latin America, intensive silvopastoral systems (SPS) are being promoted to increase cattle productivity on certain lands while facilitating the removal of cattle from marginal areas for forest restoration. However, the recovery of these forests and their contribution to the overall conservation value of the landscape has not been assessed rigorously. We evaluated forest structure and composition in 20 sites in a region of the Colombian Andes where a decade ago farmers transitioned to SPS and fenced off riparian areas to enable forest recovery. We compared these restored forests to a reference model based on the remaining riparian forest across the region, all of which has been subjected to human management. We found that woody species richness was higher in restored than in reference forests, and the proportion of large-seeded, later successional, animal-dispersed species were similar in both forest types. Whereas we found a similar suite of dominant tree species in restored and reference forest, Guadua angustifolia, a native giant bamboo was more abundant in the reference forests due to human management. Total tree basal area was higher in restored forests due to a small number of very large trees likely present in the pastures at the time of site protection. These findings highlight (1) the potential for recovery of diverse forests in riparian sites despite previous grazing use and (2) the role of remnant trees in facilitating natural succession. Overall, rapid forest recovery with minimal intervention in previously farmed lands is good news for conservation in a region that still harbors significant biodiversity despite high levels of fragmentation and the influence of human management.

Tropical grassland-savanna mosaics are threatened globally, but they are challenging to restore because highly competitive pasture grasses inhibit recovery and are not shaded out by the patchy tree cover. We analyzed the outcomes of restoration projects and experiments established over four years in 55 ha of abandoned pastures dominated by invasive C4 grasses within the Neotropical savanna, Central Brazil. We tested the efficacy of direct seeding native grasses, forbs, shrubs and trees in reducing invasive grass cover and increasing native ground cover. We performed a series of experiments aimed at answering questions about the effect of seeding density, soil plowing to control invasive grasses, life form of ground cover species (grass, forb or shrub) and soil type on restoration outcomes. Relative native cover reached 34 ± 3% three rainy seasons after the first seeding experiment. Higher seeding densities and more soil plowing repetitions increased relative native cover. Soil type interacted with the life form of ground cover species to strongly influence relative native cover; two years after seeding, the highest relative native cover was achieved in rocky soils seeded with grasses (78 ± 6%) and the lowest was for seasonally waterlogged soils seeded with shrubs (15 ± 4%). Direct seeding can effectively establish many native Neotropical savanna species of different life forms with better restoration outcomes on rocky soils and with higher seeding densities. Further research is urgent to improve restoration methods, especially to control invasive grasses, to be able to achieve the large-scale restoration targets set internationally.

Defining the reference system for restoration projects in regions characterized by complex vegetation mosaics is challenging. Here we use the Cerrado region of Brazil as an example of the importance of clearly defining multiple natural and anthropogenically altered states in grassland‐savanna‐forest mosaics. We define three main, natural vegetation types–grassland, savanna, and scleromorphic (cerradao) forest–to (1) distinguish between original and degraded states and (2) set appropriate targets for and guide restoration. We contend that the differences in Cerrado vegetation composition originally were driven by soil conditions and secondarily by fire frequency and precipitation patterns that differ from the core to the edge of the Cerrado region. Grasslands are found on the shallowest, least fertile soils and/or in waterlogged soils; scleromorphic forests are generally located on deeper, more fertile soils; and savannas occupy an intermediate position. In recent decades, this biophysical template has been overlain by a range of human land‐use intensities that strongly affect resilience, resulting in alternative anthropogenic states. For example, areas that were originally scleromorphic forest are likely to regenerate naturally following low‐ or medium‐intensity land use due to extensive resprouting of woody plants, whereas grassland restoration requires reintroduction of grass and forb species that do not tolerate soil disturbance and exotic grass competition. Planting trees into historic grasslands results in inappropriate restoration targets and often restoration failure. Correctly identifying original vegetation types is critical to most effectively allocate scarce restoration funding.

Overview of the PLoS ONE collection 'Rewilding and Restoration'.

Soil and litter arthropods represent a large proportion of tropical biodiversity and perform important ecosystem functions, but little is known about the efficacy of different tropical forest restoration strategies in facilitating their recovery in degraded habitats. We sampled arthropods in four 7‐ to 8‐year‐old restoration treatments and in nearby reference forests. Sampling was conducted during the wet and dry seasons using extractions from litter and pitfall samples. Restoration treatments were replicated in 50 × 50‐m plots in four former pasture sites in southern Costa Rica: plantation – trees planted throughout the plot; applied nucleation/islands – trees planted in patches of different sizes; and natural regeneration – no tree planting. Arthropod abundance, measures of richness and diversity, and a number of functional groups were greater in the island treatment than in natural regeneration or plantation treatments and, in many cases, were similar to reference forest. Litter and pitfall morphospecies and functional group composition in all three restoration treatments were significantly different than reference sites, but island and plantation treatments showed more recovery than natural regeneration. Abundance and functional group diversity showed a much greater degree of recovery than community composition. Synthesis and applications: The less resource‐intensive restoration strategy of planting tree islands was more effective than tree plantations in restoring arthropod abundance, richness, and functional diversity. None of the restoration strategies, however, resulted in similar community composition as reference forest after 8 years of recovery, highlighting the slow rate of recovery of arthropod communities after disturbance, and underscoring the importance of conservation of remnant forests in fragmented landscapes.

Ecological restoration of modified and degraded landscapes is an important challenge for the 21st century, with potential for major gains in the recovery of biodiversity. However, there is a general lack of agreement between plant- and animal-based approaches to restoration, both in theory and practice. Here, we review these approaches, identify limitations from failing to effectively integrate their different perspectives, and suggest ways to improve outcomes for biodiversity recovery in agricultural landscapes. We highlight the need to strengthen collaboration between plant and animal ecologists, to overcome disciplinary and cultural differences, and to achieve a more unified approach to restoration ecology. Explicit consideration of key ecosystem functions, the need to plan at multiple spatial and temporal scales, and the importance of plant–animal interactions can provide a bridge between plant- and animal-based methods. A systematic approach to restoration planning is critical to achieving effective biodiversity outcomes while meeting long-term social and economic needs.

Author(s): Brancalion, Pedro HS; Meli, Paula; Tymus, Julio RC; Lenti, Felipe EB; Benini, Rubens M; Silva, Ana Paula M; Isernhagen, Ingo; Holl, Karen D

International audience; We welcome the opportunity to further discuss our analysis and conclusions [1] that Larkin et al.'s [2] (hereafter LEA) comment provides. In this response, we first discuss mischaracterizations and criticisms of our analyses, then highlight how the main conclusions from both LEA's and our analyses are similar, and end with further discussion of what both analyses suggest for restoration and conservation moving forward.LEA contend that the response ratio is ‘fundamentally flawed’; given its prominence in the restoration [3–5] and meta-analysis literatures [6–8], we suggest that the matter of its usefulness or lack thereof is far from settled and leave it to meta-analysis statisticians to discuss its utility. For those interested, both LEA and we consulted with meta-analysis statisticians who came to different conclusions (see published reviews of LEA's comment). We further direct readers to the reviews of LEA's comment for a more in-depth response to their criticisms on the choice of variables to calculate response ratios, of how to treat response ratios that overshoot recovery goals, exclusion of invasive species disturbances, and of minimal sample size calculations.

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

In tropical areas with high levels of fragmentation due to agricultural use, forest fragments play an important role for biodiversity conservation at the landscape scale. But these fragments are subject to recurrent disturbances, which lead to arrested succession and loss of functional groups. In such cases, active restoration, such as enrichment planting, could facilitate recovery. We studied enrichment planting methods to restore tropical forest fragments in the Brazilian Atlantic Forest, and we evaluated the costs to implement them in the field. We planted four later successional tree species as seeds, small seedlings, and large seedlings in three remnants embedded in a landscape dominated by sugarcane plantations. Overall, survival of seedlings was low using all methods due to a severe drought during the study period, and there were no differences in seedling survival or growth across the three study sites. Direct seeding was the least expensive technique but was successful only for one large-seeded species, Hymenaea courbaril. Large seedlings survived better than did small seedlings, for all four species, suggesting that the additional cost of growing large seedlings is warranted to enhance success. Our results highlight that a combination of planting methods at species level is likely to increase restoration success.EDITED BY John Parrotta EDITED BY John Parrotta

Neotropical fruit bats (family Phyllostomidae) facilitate forest regeneration on degraded lands by dispersing shrub and tree seeds. Accordingly, if fruit bats can be attracted to restoration sites, seed dispersal could be enhanced. We surveyed bat communities at 10 sites in southern Costa Rica to evaluate whether restoration treatments attracted more fruit bats if trees were planted on degraded farmlands in plantations or island configurations versus natural regeneration. We also compared the relative influence of tree cover at local and landscape spatial scales on bat abundances. We captured 68% more fruit bat individuals in tree plantations as in controls, whereas tree island plots were intermediate. Bat activity also responded to landscape tree cover within a 200-m radius of restoration plots, with greater abundance but lower species richness in deforested landscapes. Fruit bat captures in controls and tree island plots declined with increasing landscape tree cover, but captures in plantations were relatively constant. Individual species responded differentially to tree cover measured at different spatial scales. We attribute restoration effects primarily to habitat structure rather than food resources because no planted trees produced fruits regularly eaten by bats. The magnitude of tree planting effects on fruit bats was less than previous studies have found for frugivorous birds, suggesting that bats may play a particularly important role in dispersing seeds in heavily deforested and naturally regenerating areas. Nonetheless, our results show that larger tree plantations in more intact landscapes are more likely to attract diverse fruit bats, potentially enhancing seed dispersal.

Past studies have shown that tropical forest regeneration on degraded farmlands is initially limited by lack of seed dispersal, but few studies have tracked changes in abundance and composition of seed rain past the first few years after land abandonment. We measured seed rain for 12 months in 10 6-9-year-old restoration sites and five mature, reference forests in southern Costa Rica in order to learn (1) if seed rain limitation persists past the first few years of regeneration; (2) how restoration treatments influence seed community structure and composition; and (3) whether seed rain limitation is contingent on landscape context. Each restoration site contained three 0.25-ha treatment plots: (1) a naturally regenerating control, (2) tree islands, and (3) a mixed-species tree plantation. Sites spanned a deforestation gradient with 9-89% forest area within 500 m around the treatment plots. Contrary to previous studies, we found that tree seeds were abundant and ubiquitous across all treatment plots (585.1 ± 142.0 seeds · m(-2) · yr(-1) [mean ± SE]), indicating that lack of seed rain ceased to limit forest regeneration within the first decade of recovery. Pioneer trees and shrubs comprised the vast majority of seeds, but compositional differences between restoration sites and reference forests were driven by rarer, large-seeded species. Large, animal-dispersed tree seeds were more abundant in tree islands (4.6 ± 2.9 seeds · m(-2) · yr(-1)) and plantations (5.8 ± 3.0 seeds · m(-2) · yr(-1)) than control plots (0.2 ± 0.1 seeds · m(-2) · yr(-1)), contributing to greater tree species richness in actively restored plots. Planted tree species accounted for < 1% of seeds. We found little evidence for landscape forest cover effects on seed rain, consistent with previous studies. We conclude that seed rain limitation shifted from an initial, complete lack of tree seeds to a specific limitation on large-seeded, mature forest species over the first decade. Although total seed abundance was equal among restoration treatments, tree plantations and tree islands continued to diversify seed rain communities compared to naturally regenerating controls. Compositional differences between regenerating plots and mature forests suggest that large-seeded tree species are appropriate candidates for enrichment planting.

© 2015 Elsevier Ltd. Large areas of tropical lands are being removed from agriculture and restored to address conservation goals. However, monitoring the ecological value of these efforts at the individual land-owner scale is rare, owing largely to issues of cost and accessibility. Traditional field-based measures for assessing forest recovery and habitat quality can be labour intensive and costly. Here we assess whether remote sensing measurements from lightweight unmanned aerial vehicles (UAV) are a cost-effective substitute for traditional field measures. An inexpensive UAV-based remote sensing methodology, Ecosynth , was applied to measure forest canopy structure across field plots in a 7-9-yr tropical forest restoration study in southern Costa Rica. Ecosynth methods combine aerial images from consumer-grade digital cameras with computer vision software to generate 3D 'point cloud' models of vegetation at high spatial resolutions. Ecosynth canopy structure measurements were compared to field-based measures and their ability to predict the abundance of frugivorous birds; key seed dispersers that are sensitive to canopy structure. Ecosynth canopy height measurements were highly correlated with field-based measurements (R2≥0.85), a result comparable in precision to LiDAR-based remote sensing measurements. Ecosynth parameters were also strongly correlated with above-ground biomass (R2≥0.81) and percent canopy openness (R2=0.82). Correlations were weaker with proportion-based measures such as canopy roughness (R2=0.53). Several Ecosynth metrics (e.g., canopy openness and height) predicted frugivore presence and abundance at levels of accuracy similar to those of field-based measurements. Ecosynth UAV remote-sensing provides an effective alternate methodology to traditional field-based measures of evaluating forest structure and complexity across landscapes. Furthermore, given the volume of data that can be generated in a single flight plan, as well as the ability to use the technology in remote areas, these methods could expand the scope of studies on forest dynamics and recovery when combined with field-based calibration plots.

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., National Science Foundation, German Helmholtz Centre for Environmental Research—UFZ, Leipzig (Research Program ‘Terrestrial Environments'), sDiv, the Synthesis Centre of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (German Research Foundation), Northern Illinois University

Restoration treatments can impact the growth and development of tree seedlings; however, it is often difficult to discern whether responses are driven by changes in microclimate, biotic interactions, or soil properties. To isolate for the latter, we quantified the growth response of four species [Ocotea puberula (Lauraceae); Otoba novogranatensis (Myristicaceae); Pseudolmedia mollis (Moraceae); Senna papillosa (Fabaceae)] grown under similar shade-house conditions in soils collected from 6 - 7 year old active (four species plantation) and passive restoration plots (natural recovery), and nearby reference forest sites in Costa Rica. We also evaluated the role of parent tree by collecting individuals from five mother trees. We measured height, above- and below-ground biomass, and determined root: shoot ratios (RSR). Species differed markedly in their responses. Ocotea, and to a lesser extent Pseudolmedia, were largely driven by parent tree. In contrast, Senna showed a strong soil response for all variables with more growth in active than passive restoration soils; reference forest seedlings were typically intermediate. An interaction suggested that some genotypes are more responsive to different soil properties than others. Otoba had higher soil-driven RSR in both restoration treatments. Surprisingly most soil nutrients, including %N, were similar or significantly lower in active restoration soils, suggesting that seedlings are responding to differences in soil microbial communities or more labile nutrients (e.g., NH4+ and NO3-). Active restoration appears to facilitate the growth of other species by improving certain soil properties. Additionally, genotypes are an important driver of seedling vigor and some species may be more responsive to subtle differences in soil properties than others.