Active Restoration Techniques Research Articles

Success of passive and active restoration of lowland hay meadows with regard to current and historical references

The restoration of hay meadows is one of the major challenges in temperate Europe, to overcome the drastic loss and degradation of these semi-natural habitats. Evaluation of restoration success requires the definition of a relevant reference ecosystem. Historical phytosociological relevés dating from the 1960s–1970s, before large scale agriculture intensification, may be used as the reference framework for such purposes. However, this reference framework may no longer be pertinent in our present-day ecological and socio-economic context. In this study, we assessed the success of three restoration techniques for lowland hay meadows, based on plant species richness and composition and functional traits, by comparing the restoration trajectories to historical and current references. The three restoration techniques, passive restoration mowing, active fresh hay transfer and active sowing of threshing material, were implemented depending on the initial level of degradation and the proximity to well-preserved meadows. The species composition of restored meadows clearly differed from historical references but converged toward current references, for both passive and active restoration techniques. Historical references are characterized by short, stress-tolerant dicotyledonous plant species with small specific leaf area, indicators of nutrient-poor environments. The gap observed between plant communities of historical and current meadows suggests that the historical data are an over-ambitious target for restoration purposes and can hardly be considered relevant to our present-day context. Therefore, creation of a new reference framework of lowland hay meadows is needed for the adequate implementation of restoration projects. Successful outcomes of active and passive techniques must encourage practitioners to adapt the choice of the restoration method depending on the local ecological context, i.e., level of degradation and proximity to well-preserved habitats.

Challenges and directions for open ecosystems biodiversity restoration: An overview of the techniques applied for Cerrado

Abstract Ecological restoration of tropical open ecosystems remains challenging for both science and practice. Over the last decade, innovative techniques have been developed, but whether they have been successful or not remains to be demonstrated. Assessing the outcomes of these initiatives is crucial to drive the following steps to improve tropical grasslands and savanna restoration. Analysing 82 data sets from the literature and primary data collection, we assessed the effectiveness of passive and active restoration techniques applied in Cerrado open ecosystems. We used plant diversity variables (species and growth forms) as indicators, considering ruderals and exotics as non‐target species. Specifically, we aimed to answer: (i) How does the diversity of target species change through time in areas subject to passive restoration? (ii) Are active and passive restoration techniques effective in restoring the proportion of target species found in old‐growth reference ecosystems? (iii) Have the current techniques been successful in recovering the proportions of growth forms of reference ecosystems? We found that target species proportions do not increase with time, suggesting limitations of typical species to colonise degraded sites. Hence, passive restoration will promote the conservation of a limited and constant number of target species. This number will depend on the magnitude of degradation and previous land use. The restoration techniques currently applied to restore the biodiversity of Cerrado open ecosystems are not reaching the reference standards, with distinct techniques driving plant communities to different sets of growth forms. Active restoration based on propagules obtained from pristine donor sites (topsoil translocation, plant material transplant, and seeding) performed better than passive restoration for most of the growth forms analysed. Synthesis and applications: Different growth forms have different roles in determining the structure and functioning of Cerrado vegetation. A mix of techniques can better approximate plant diversity and the proportionality of target species of pristine ecosystems. Singular restoration approaches are insufficient for restoring Cerrado open ecosystem biodiversity. Mixed efforts encompassing various techniques are required instead. Furthermore, it is likely restoration success can be improved with greater investment in improving our understanding of, and developing existing restoration techniques.

Assisted dispersal and retention of lichen‐dominated biocrust material for arctic restoration

Arctic biocrust loss due to industrial activity can have long‐lasting ecological impacts, highlighting the importance of restoring disturbed tundra environments. This research focused on biocrust establishment on substrates of by‐product materials from diamond mining (crushed rock, lake sediment, processed kimberlite), inoculant dispersal (dry placement, slurry), habitat amelioration (erosion control blanket, tundra soil, woody debris), and containment (jute mat), over three field seasons at Diavik Diamond Mine, Inc., Northwest Territories. Three years after inoculation, lichens were detected on 100% of inoculated plots and 70% of uninoculated plots (likely blown in from inoculated plots). Uninoculated plots had significantly lower species richness and vegetation cover than inoculated plots. Biocrust retention was highest on plots with erosion control blanket, containment, woody debris, and crushed rock; larger scale application of these treatments should be assessed in future. Plots with processed kimberlite, no habitat amelioration or tundra soil, and no containment had the lowest cover, species richness, and individual species abundance in year 3. This research suggests that active restoration techniques using lichen biocrust inoculation and habitat amelioration is required for successful biocrust revegetation outcomes on substrates of mining by‐products in the arctic.

Multi-dimensional approaches to scaling up coral reef restoration

Local and global stressors have led to rapid declines in coral reef health around the world. A range of active restoration techniques have recently been introduced in attempts to stem and reverse this decline, but their efficacy is debated. In particular, restoration faces the challenge of scale; successful projects must be deployed quickly over large areas, without being prohibitively expensive.Indonesia has more coral reefs – and more coral reef restoration programmes – than any other country on Earth. The past two decades have seen a rapid expansion in the scale of Indonesia’s restoration efforts. Having started in the 1980s, there are now hundreds of individual programmes across the country, several of which have outplanted tens of thousands of corals. Here, we identify ten different social, economic and environmental approaches that have contributed to this scaling up of reef restoration in Indonesia. We discuss the theoretical basis for each approach and provide case studies of their implementation from sixteen different Indonesian programmes.In combination, these diverse approaches have created opportunities to increase the operational efficiency, spatial scale, speed of deployment and social inclusivity of reef restoration in many different contexts. Their examples represent valuable learning experiences, highlighting a range of mechanisms through which management and policy interventions might aim to increase the scale of coral reef restoration. By combining ecological, social and economic strategies in a multi-dimensional approach to scale-up, reef restoration can deliver more beneficial and equitable outcomes locally, regionally and globally.

Coral reef restoration in Indonesia: A review of policies and projects

Indonesia’s coral reefs have been severely damaged by global and local stressors, and a range of active restoration techniques are now being used in attempts to rebuild degraded reefs. However, it is difficult to summarise Indonesia’s restoration efforts as a whole due to a lack of consistent reporting. Here, we first discuss Indonesia's legal policy framework concerning reef restoration; this is included in the agenda of two government ministries (Marine Affairs and Fisheries, and Environment and Forestry), and comprises national laws and governmental, presidential and ministerial regulations. We then provide an extensive review of reef restoration projects in Indonesia, documenting 533 records across the country between 1990 and 2020. Most (73%) of these records come from the past ten years, and many (42%) are reported in online news articles rather than scientific reports or papers. This review identified 120,483 units of artificial reef installed across Indonesia, along with 53,640 units of coral transplantation (including both coral nurseries and direct out-planting onto reefs); in total, 965,992 fragments of hard coral have been planted across Indonesia. The most favoured restoration materials are concrete (46%) and steel structures (24%). Projects are organised by a diverse range of governmental, NGO, private and community-led organisations. This review demonstrates that Indonesia’s policy has encouraged a diverse range of practitioners to implement reef restoration, but projects are often not coordinated with wider networks of restoration practitioners or scientists, and only 16% of the identified projects included a post-installation monitoring framework. Incorporating clear objectives and long-term monitoring programmes in project planning stages, while prioritising knowledge exchange and engagement with international scientific community, will substantially improve restoration outcomes in Indonesia. This will allow the country to fulfil its considerable potential as a global leader in rebuilding damaged coral reefs.

Optimizing coral reef recovery with context-specific management actions at prioritized reefs

Assisting the natural recovery of coral reefs through local management actions is needed in response to increasing ecosystem disturbances in the Anthropocene. There is growing evidence that commonly used resilience-based passive management approaches may not be sufficient to maintain coral reef key functions. We synthesize and discuss advances in coral reef recovery research, and its application to coral reef conservation and restoration practices. We then present a framework to guide the decision-making of reef managers, scientists and other stakeholders, to best support reef recovery after a disturbance. The overall aim of this management framework is to catalyse reef recovery, to minimize recovery times, and to limit the need for ongoing management interventions into the future. Our framework includes two main stages: first, a prioritization method for assessment following a large-scale disturbance, which is based on a reef's social-ecological values, and on a classification of the likelihood of recovery or succession resulting in degraded, novel, hybrid or historical states. Second, a flow chart to assist with determining management actions for highly valued reefs. Potential actions are chosen based on the ecological attributes of the disturbed reef, defined during ecological assessments. Depending on the context, management actions may include (1) substrata rehabilitation actions to facilitate natural coral recruitment, (2) repopulating actions using active restoration techniques, (3) resilience-based management actions and (4) monitoring coral recruitment and growth to assess the effectiveness of management interventions. We illustrate the proposed decision framework with a case study of typhoon-damaged eastern outer reefs in Palau, Micronesia. The decisions made following this framework lead to the conclusion that some reefs may not return to their historical state for many decades. However, if motivation and funds are available, new management approaches can be explored to assist coral reefs at valued locations to return to a functional state providing key ecosystem services.

Restoration strategies in boreal forests: Differing field and ground layer response to ecological restoration by burning and gap cutting

The boreal biome is one of the largest in the world and its forests have been widely exploited for centuries. Consequently, large areas have suffered ecological simplification and loss of biodiversity. Under the current circumstances passive conservation measures are no longer enough and active restoration techniques need to be developed and assessed to preserve and recover the loss of biodiversity. We evaluated short- and long-term effects of two restoration methods aimed at mimicking natural disturbances on species richness, Shannon Diversity and community composition of vascular plants in the field layer and bryophytes in the ground layer. The experiment consisted of 18 forest stands in northern Sweden; each assigned to a different treatment: prescribed burning, gap cutting and untreated stands left as controls. A before-after control-impact (BACI) study design was applied and data was collected on three occasions: once prior to restoration (2010) and twice post restoration; one year (2012) and eight years after (2019). We analysed the differences in species richness and Shannon Diversity with linear mixed effect models and community composition changes with multivariate methods. Fire treatment caused an initial decline in diversity for both field and ground layer, but in the long-term, field layer surpassed the species richness and Shannon Diversity values found prior to restoration. Ground layer bryophytes species richness and Shannon Diversity remained lower than pre-treatment. Prescribed burning should, therefore, be used with caution in core areas for bryophyte diversity. Community composition in burned stands differed significantly between each time point as well as when compared to other treatments, for both layers. By contrast, we found no significant differences in diversity measures or community composition after gap cutting. The absence of effects from gap cutting suggests that minor changes in canopy cover does not affect the vegetation structure of forest stands. The organism group-specific responses, and temporal variability to restoration, highlight the importance of including more than one organism group, different restoration methodologies, and long-term studies in order to properly assess restoration outcomes at landscape level.

Vegetation and soil recovery following Eucalyptus grandis removal in Limpopo Province, South Africa

South African terrestrial ecosystems are invaded by hundreds of alien plant species, and large‐scale clearing based on the passive restoration assumption that cleared areas will recover unaided is underway. This study assessed the recovery of vegetation and soil properties, three years following Eucalyptus grandis clearing using fell‐and‐removal and fell‐and‐stackburn methods at Zvakanaka Farm in Limpopo Province, South Africa. The main aim was to ascertain the extent of vegetation and soil recovery, as well as determining which clearing methods facilitate passive vegetation and soil restoration. Results indicate significantly (p < 0.001) lower native species diversity, cover and composition in cleared than in uninvaded sites. However, the recorded low species diversity and composition in cleared sites were more pronounced in the fell‐and‐stackburn than in the fell‐and‐removal sites. Measured soil physical properties varied, with compaction being higher in fell‐and‐removal, whereas soils were more repellent in fell‐and‐stackburn sites. The study concludes that vegetation and soil recovery, following E. grandis clearing, is complex and involves several interacting factors, which are linked to invasion history and intensity. Therefore, for vegetation and soil properties to recover, following E. grandis removal, the clearing programme should consider active restoration techniques, for example soil manipulation and native plant seeding.

Post-fire recovery of the plant community in Pinus brutia forests: active vs. indirect restoration techniques after salvage logging

Abstract: Although reforestation is frequently utilized in many Mediterranean Basin countries to restore burned Mediterranean pine woodlands, post-fire recovery of the plant community is often neglected. To compare the post-fire recovery of the plant community following active and indirect post-fire restoration techniques, we studied three post-fire regeneration treatments in a salvage-logged Pinus brutia forest, including two active (plantation and seeding) restoration techniques and one indirect (natural regeneration). An unburned pine stand was also included in the study. We applied the point-intercept method to obtain data on the presence and cover of individual species and functional groups in six replicate one-hectare plots for each treatment. We found no significant differences in plant species richness among post-fire treatments; however, plant community composition and vegetation structure were significantly different between treatments. There was a shift in plant community structure when active restoration techniques were applied, from the woody- and resprouter-dominated plant community of the unburned site to an annual herbaceous- and non-resprouter-dominated one. Our results suggest that active restoration by planting tree saplings in Mediterranean pine forests after a fire may decrease the plant community’s resilience and provide empirical evidence that pine plantation treatments change the plant species composition of these forests. These results have important implications for post-fire management of Mediterranean Basin pine forests.

Efecto de la restauración post-minería de la comunidad vegetal de matorral xerófilo, en Nuevo León, México

Antecedentes y Objetivos: Las estrategias de restauración tienen como objetivo favorecer la recuperación de los ecosistemas alterados, para lograr el restablecimiento de su estructura y funcionamiento naturales. La presente investigación evaluó la abundancia, dominancia, frecuencia y diversidad de especies en tres áreas de matorral espinoso tamaulipeco.Métodos: Dos áreas fueron sometidas durante siete años (2000-2006) a procesos de aprovechamiento a cielo abierto. A una se le aplicaron técnicas de restauración y a la otra no, y se compararon con un área en la que no se tiene perturbación registrada llamada área referencia. En el año 2013 se establecieron 36 sitios de muestreo, 12 por cada una de las áreas cuyas dimensiones fueron de 100 m2 (10 × 10 m), en las que se registraron los atributos ecológicos de las comunidades vegetales establecidas.Resultados clave: En el área sin restaurar no se registró regeneración de la comunidad vegetal. La riqueza específica (S), índice de Margalef (DMg) e índice de Shannon (H´) mostraron diferencias significativas entre el área restaurada y la de referencia (Valores medios S 4.75 y 8.25, DMg 0.87 y 1.80, H´ 0.7 y 1.54, respectivamente), mientras que las variables de densidad, área de copa e índice de Pretzsch (A) no mostraron diferencias.Conclusiones: Se concluye que la técnica de restauración activa, la cual consiste en el depósito de material rocoso y edáfico en el área, y su exclusión de actividades productivas, generan condiciones favorables para que la comunidad vegetal del matorral espinoso tamaulipeco se establezca teniendo similitud en la densidad y área de copa a un área de referencia en siete años.

Deciding when to lend a helping hand: a decision-making framework for seabird island restoration

Following the removal of an introduced species, island restoration can follow two general approaches: passive, where no further intervention occurs and the island is assumed to recover naturally, and; active, where recovery of key taxa (e.g. seabirds) is enhanced by manipulating movement and demography. Steps for deciding between these techniques are: (1) outlining an explicit restoration goal; (2) building a conceptual model of the system; (3) identifying the most effective management approach; and (4) implementing and monitoring outcomes. After decades of island restoration initiatives, retrospective analysis of species’ responses to active and passive management approaches is now feasible. We summarize the advantages of incorporating these analyses of past restoration results as an initial step in the decision-making process. We illustrate this process using lessons learned from the restoration of seabird-driven island ecosystems after introduced vertebrate eradication in New Zealand. Throughout seven decades of successful vertebrate eradication projects, the goals of island restoration have shifted from passive to active enhancement of island communities, which are heavily dependent on burrow-nesting petrel population recovery. Using a comparative analysis of petrel response to past predator eradications we built a conceptual model of petrel recovery dynamics and defined key site and species characteristics for use in a stepwise decision tree to select between active or passive seabird population management. Active restoration techniques should be implemented when seabird populations are absent or declining; and on islands with no nearby source colony, small remnant colonies, highly altered habitat with shallow soil and slopes, and with competitive species pairs. As we continue to restore complex island communities, decision-making tools using a logical, step-wise framework informed by previous restoration successes and failures can aid in increasing understanding of ecosystem response.

DoesEucalyptus grandisinvasion and removal affect soils and vegetation in the Eastern Cape Province, South Africa?

Many invasive alien plants drive changes in native community composition, structure and diversity. They alter soil nutrient regimes of native communities and affect native plant recovery outcomes following their removal. We assessed whether Eucalyptus grandis invasion and removal alters the soil physico-chemical properties and native vegetation recovery in the Eastern Cape Province, South Africa. We collected samples from topsoil in E. grandis invaded sites (canopy cover > 75%), cleared sites (eight years ago) and native sites (canopy cover > 80%) and quantified soil moisture, concentrations of soil macro elements (N, C and P), pH and exchangeable cations (K, Ca, Mg, Na) as well as measured soil water repellency using the Water Droplet Penetration Time and infiltration. We conducted vegetation surveys in plots measuring 10 × 10 m. Invasion by E. grandis had varying effects on soil physico-chemical properties, causing increase in soil pH and P, while decreasing total N and C. The removal of E. grandis also showed varying effects on soil physico-chemical properties, but seems to have further triggered the loss of some soil nutrients (especially soil P). Soil water repellency (a measure of soil compaction) has improved in cleared sites to non-repellent soils compared to repellent soils in invaded site. Eucalyptus grandis reduced species richness of the invaded sites. The presence of native species on cleared sites indicates a positive trajectory towards vegetation recovery. We conclude that E. grandis invasion and removal trigger varying effects on soil properties (both increases and decreases). For soil and vegetation restoration of cleared sites to be effective, active restoration techniques such as soil transfer, nutrient manipulation and native plant seeding should be considered.

Assessing techniques to enhance early post-settlement survival of corals in situ for reef restoration

For degraded coral reef systems with limited larval supply, active restoration techniques may provide a means of replenishing adult coral populations. Settling or seeding large numbers of sexually-produced larvae directly onto denuded substrate is a potential restoration tool that can eliminate the costs associated with rearing coral spat in culturing facilities. However, the long-term potential to enhance recruitment using seeding techniques has generally been limited due to high post-settlement mortality. Using the brooding coral Porites astreoides (Lamarck, 1816), we explored two potential strategies-choosing favorable substrate communities and caging recently settled spat-to enhance early post-settlement survival during seeding efforts. Larvae were collected from adult colonies in the laboratory and, once competent to settle, were seeded directly onto the reef substrate. Settled spat were individually mapped and monitored using fluorescence techniques, and found to have a low survivorship with <3%-15% surviving after 1 mo, and <1% after 5 mo. Techniques to enhance survival, including choice of substrate and post-settlement caging, did not significantly influence the high rates of natural mortality. These results underscore the general lack of knowledge regarding the major factors that drive the magnitude of early post-settlement mortality, and future identification of these mortality factors may lead to suitable techniques to enhance survival in seeding efforts.

Experimental Planting of Native Shrubs on Santa Cruz Island from Small Nursery Stock

The natural vegetation of Santa Cruz Island was severely disturbed by nonnative herbivores for well over a century. As the livestock and feral ungulates (primarily sheep, cattle, and pigs) were removed from the island over the last 30 years, many of the native plant communities began to recover naturally. Recovery has been extremely slow in other areas, especially where nonnative annual grasses and fennel (Foeniculum vulgare) dominate several hundred hectares that were under intense agricultural use (pastures and farmed lands). We experimentally tested the feasibility of speeding up the recovery process in a postagricultural area of the island's Central Valley using active restoration techniques. We assessed how weed control via herbicide application and planting of small nursery stock without irrigation might contribute to restoring natural plant assemblages in 3 different areas of the Central Valley (valley bottom, upper south-facing slope, and midsouth-facing slope). In February 2009, we planted the same 21 species of native plants in experimental plots with and without weed control at each location. In December 2009, we planted 28 species in adjacent plots after 2 seasons of weed control. We assessed natural recruitment in weeded and unweeded plots that were not planted. At all 3 locations, a single early season herbicide treatment prior to planting had strong positive effects on the survival, cover, and reproduction of planted natives compared to no herbicide treatment; the effects persisted and grew stronger in the second and third years. Repeated herbicide treatments over 2 years before planting did not result in any additional significant positive effects on native survival or growth compared to only one herbicide treatment. We saw virtually no natural recruitment of native shrubs in unplanted plots. We found that typical coastal sage scrub species performed best at the upper slope site and poorly at the valley bottom site. Grasses and shrubs tolerant of poorly drained soil did better in the valley bottom. We found that planting native species from small nursery stock without irrigation is effective for a wide range of grassland and coastal sage scrub species. All of the restoration techniques we used are cost effective and can be scaled-up to restore large areas of postagricultural lands.

Restoration of Coast Redwood (&amp;lt;i&amp;gt;Sequoia sempervirens&amp;lt;/i&amp;gt;) Forests through Natural Recovery

The management of second-growth Sequoia sempervirens (coast redwood) forests for the purpose of restoration and ecological conservation is a growing trend. However, little is known about the long-term regenerative potential of this forest type in the absence of post-harvest management techniques such as thinning and planting. Data on forest composition and structure were collected on a chronosequence (80 - 160 years) of mature recovering stands in the southern coast redwood range using a replicated, randomized, plot design. Results indicated that many stand characteristics including tree density, canopy cover, redwood dominance, species richness, herbaceous cover, and shrub cover reached levels statistically equivalent with old-growth reference sites in recovering stands within the time frame of this chronosequence. The recovery of individual herbaceous understory species was inconsistent however. While the cover of redwood-associated species (Oxalis oregana, Trientalis latifolia, and Disporum hookeri) reached levels statistically equivalent to old-growth reference sites, others (Trillium ovatum and Viola sempervirens) did not. Total basal area and species evenness also trended toward, but did not reach, old-growth conditions. The arboreal aspects of coast redwood forests appear to be remarkably resilient following a single logging event, and recover rapidly in the absence of active restoration techniques. The protracted recovery of certain redwood associated herbaceous understory species will require further study.

Changes in plant community composition and structure following restoration of maritime communities1

Old field succession has been reviewed extensively in many community settings; however, secondary succession in maritime communities, especially forest and shrub communities is poorly understood. Maritime communities of the North American Atlantic coast are unique and often fragmented ecosystems that provide critical stopover sites for migratory birds. Historical losses coupled with rising developmental pressures have created the need for conservation and restoration to protect these globally rare communities. We examined secondary succession by analyzing the vegetation community composition and soil seed bank of an abandoned agricultural field initially and at seven years (2009) after initiation of state-agency site restoration that used a combination of active and passive restoration techniques. The restoration field was divided into three projected habitats: early maritime forest (16 ha), maritime shrub (12 ha), and coastal grassland (8 ha). A trend was observed with loss of species richness across habitat types. There was a high proportion of species turnover, yet there were no significant differences in the number of species belonging to functional groups for each habitat between the two sampling years (2003 and 2009). Zones where active restoration techniques were used were more indicative of restoration success compared to areas that relied on spontaneous succession. Long-term vegetation surveys are critical to assess the success of restoration operations, and to describe and predict successional trajectories. Accessible vegetation survey data may become increasingly important in the future as land managers place more emphasis on protecting and restoring these overdeveloped, unique coastal communities.

Engineering of coral reef larval supply through transplantation of nursery-farmed gravid colonies

The continuous worldwide degradation of coral reefs raises an urgent need for novel active restoration techniques as traditional conservation practices have failed to impede the incessant reefs' decline. While applying the “gardening coral reefs” methodology in Eilat (Red Sea, Israel), we examined reproductive outputs of naturally-grown and outplanted, nursery-farmed Stylophora pistillata colonies from three coral-transplantation trials (November 2005, May 2007, and September 2008), along three reproductive seasons. Surprisingly, transplanted colonies showed better reproductive capacities than the natal Stylophora colonies during > 4 post-transplantation years. A higher percentage of nursery-farmed colonies released planula larvae as compared to naturally-grown colonies. Gravid transplants also shed more planulae per colony, yielding significantly augmented numbers of total planulae over naturally developed S. pistillata colonies. Our results indicate that nursery-grown corals may be used to enhance reef resilience by contributing to the larval pool, forming an engineered larval dispersal instrument for reef rehabilitation.