Life on Land

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Reforestation and Sustainable Development

  • Vladan IvetićEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-71065-5_31-1
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Synonyms

Definitions

Reforestation is re-establishment of forests, by natural (including human induced) process of re-occupying of land or artificially – by planting of seedlings or direct seeding on a forest land.

Reforestation is a generic term, used to define a range of processes and human activities resulting with re-establishment of forest in a specific area: from exclusively artificial establishment of forests to broader concept which include the both artificial and natural re-establishment; from restoring of species composition and stand structure to conversion of species and/or genotypes; and from immediate action to re-establishment of forest after a relative long period of time. There is a wide range of definitions used for reforestation, depending on context (operational, ecological, and economic), objectives (statistics and research), and authorities (government, business, and NGO). At one side of spectra is an early definition offered by FAO (1967) for man-made forests regarding to “Forests established artificially by reforestation on land which carried forest within the previous 50 years or within living memory, and involving the replacement of the previous crop by a new and essentially different crop.” This definition indicate that reforestation results with a clearly man-made forest (Carle and Holmgren 2003), with replacement of genotypes and even species. On the other side of spectra are definitions of reforestation which including both natural and artificial regeneration, and including conversion of non-forested land to forested land. One of such definitions is definition by UNFCCC (2013), regarding to reforestation as “The direct human-induced conversion of non-forested land to forested land through planting, seeding and/or the human-induced promotion of natural seed sources, on land that was forested but has been converted to non-forested land.” A total of 118 definitions of reforestation collected by Lund (2018) ranges between these extremes, with 18 definitions including both natural and artificial re-establishment of forest, and different 16 definitions including conversion of non-forested land to forested land and/or consider reforestation and afforestation the same. Definition used by FAO for Forest Resource Assessment, evolved since 1967, and in FAO FRA 2015, reforestation is defined as “re-establishment of forest through planting and/or deliberate seeding on land classified as forest” FAO (2012). This definition implies that reforestation do not result with increase in forest cover, that it is a result of exclusively human intervention, excluding natural regeneration of forest, but this definition in same time in same time includes coppice from trees that were originally planted or seeded. However, a number of research studies and legislation documents include re-occupation of abandoned agricultural land or deforested areas by natural succession process as reforestation. Changes of definitions and views on forests follows the broadening of forest management objectives in last 300 years (Chazdon et al. 2016), and definition of reforestation should follow these changes, by shifting from more operational, to more ecological aspect of process.

Distinction from Afforestation

Although reforestation and afforestation are often consider equal, the distinction is usually made on whether the land use is changed and on the time between the lost and re-establishment of a forest cover at a specific area. Defined by the time since forest cover is lost, reforestation refers to re-establishment of forest at the land from which tree cover was relatively recently removed (intentionally by harvesting and change in land use, or un-intentionally by forest fire, windthrow, or some other event), while afforestation refer to establishment of forest at land which has been without the forest for a long period of time. However, there is no consensus on length of this period of time, and references such as “50 years or within living memory” (FAO 1967) and “historical time” (IPCC 1996) were offered. The distinction between afforestation and reforestation on time reference is questionable, and in some cases both actions are treated identically, e.g., under the Kyoto Protocol (IPCC 2000) or in some countries like Brazil and Bulgaria (Lund 2018), for example. In addition, because their similar goals and processes, reforestation and afforestation can be consider as identical activities for economic and practical purposes (Zhang 2017). Distinction between these two processes similar by practices used and by their result (e.g., planted forest) based on time and previous land use is appropriate for statistical reasons of survey of changes in land use. From operational aspect, the more reasonable distinction between afforestation and reforestations is on site condition, concerning the usually more harsh conditions at bare land (the most common conditions for afforestation) and more favorable conditions at the forest land (especially if reforestation take place recently after tree cover is removed).

The Role of Reforestation in Sustainable Development and Large Reforestation Programs

Reforestation, covering the wide range of definitions, has a significant role in sustainable development. Reforestation is important tool in reduction of deforestation, fight against desertification, and mitigation of climate change, providing in same time a range of economic, social, and environmental benefits. The range of environmental benefits can be manipulated with size (larger reforested areas provide more habitats, carbon, and water cycles), species composition (mixture of native species is better for biodiversity while monoculture of non-native species sequester carbon faster), and tree density (Cunningham et al. 2015). Reforestation have an important role in achieving UN Sustainable Development Goals and, like afforestation, particularly projects aimed at ecosystem restoration, generate a number of co-benefits that promote sustainable development and contribute to climate change mitigation (UNFCCC 2013).

There are many large-scale initiatives and programs for reforestation and restoration at global, regional, and national level. Some of the global initiatives sets aim at a specific number of planted trees, without any coordination of where and what species are planted, accounting the all reported plantings, from an individual efforts at small-scale to large-scale programs funded and run by different institutions. One of such is a Billion Tree Campaign, launched at 2006, and successfully reaching its target of planting a minimum of one billion trees in 2007. After accounting over 15 billion trees planted, the Billion Tree Campaign becomes the Trillion Tree Campaign in 2017. This campaign accounts all trees reported to be planted after November 2007, as well as pledges for planting trees in the future, with only restrictions on reforestation as part of commercial forestry, where reforestation is practically a restocking, resulting with same number of trees like before harvesting. By far, the largest international initiative is the Bonn Challenge, launched by the Government of Germany and IUCN in 2011, aiming to restore 150 million hectares of degraded and deforested lands in biomes around the world (by approach of forest landscape restoration) until year 2020. This goal is later extended by the New York Declaration on Forests of the 2014 UN Climate Summit, to restoration of 350 million hectares until year 2030. The Bonn Challenge drives an implementation of national priorities and commitments, and up to 2018, 47 governments, private associations, and companies have pledged over 160 million hectares to reach the goal. The biggest reforestation projects at the national level are ongoing in China, e.g., Three-North Shelterbelt Forest Program (also called as the Green Great Wall) and Grain for Green Program.

Reforestation Practice

Reforestation is an ongoing activity in a managed forests following harvesting, which can differ from forest re-establishment following a disturbance or at land previously used for different purpose. In any case, a successful active reforestation requires a set of skills and good knowledge of the forest site conditions, risks and constraints of the species involved, and available establishment techniques. The successful reforestation also requires advance planning and after planting monitoring and silviculture.

Basically, reforestation can be (1) passive, without any human intervention by natural regeneration or natural succession process; and (2) active, which can be (a) assisted natural regeneration or human induced reforestation, with some silviculture practices involved like selection of seed trees, site preparation, natural tree seedlings protection, vegetation control, and enrichment planting; and (b) artificial reforestation which imply artificial regeneration by direct seedling or planting of seedlings (Table 1). Active reforestation is necessary in cases of insufficient natural regeneration, but can be used to accelerate succession process and ecological cycle, as well. The best method for reforestation depends on management goals, the presence of a seed source, site conditions and capability, time required to establish a new generation forest, and finance.
Table 1

Methods of reforestation

  

Level of human intervention

Land use

Planning and design

Silvicultural practice in establishing phase

Passive

Natural regeneration and natural reforestation

No

Forest land cleared of forests after some disturbance and abandoned agriculture land

No

No

Active

Assisted natural regeneration

Low

Forest land cleared of forests after some disturbance

Seed tree selection,

Provenance to site matching (in cases of enrichment seeding and planting)

Seed tree method,

Site preparation,

Direct seeding,

Planting,

Vegetation control

Artificial reforestation

High

Forest land cleared of forests after some disturbance or used for different purposes for no longer than 50 years

Species selection (in case of conversion)

Provenance to site matching

Planting material selection based on quality

Site preparation

Planting spot preparation Direct seeding

Planting Vegetation control

Passive Reforestation: Natural Reforestation and Natural Regeneration

Ambitious large-scale forest restoration initiative and commitments are unlikely to meet their goals without natural regeneration. Forest restoration based on natural regeneration is cheaper than other methods like direct seeding or planting and can be applied on much larger areas, including forest clearings, landscape patches, and abandoned agricultural land.

Natural regeneration is re-establishment of forest by self-sown seed of trees remaining at or growing adjacent to the clear area, including coppice shot or root suckers. During natural regeneration forest regrowth begins with spontaneous re-establishment of plant and animal species following disturbances at a wide range of spatial scale (Chazdon and Guariguata 2016). After disturbance, clear area is usually quickly occupied by seeds from neighboring plants. This creates a mixture of herbaceous plants, shrubs, and tree species adapted to the site. The success of natural regeneration in forest systems strongly depends on seed available, and this approach can be used for reforestation only if it is synchronized with fruiting year of targeted tree species.

Abandoned agricultural fields offers a number of opportunities for large-scale forest restoration by natural regeneration, i.e., by natural succession process. Natural reforestation of abandoned fields is ongoing process at significant level around the world and it represents a positive outcome in terms of climate change mitigation strategies due to the enhancement of potential carbon sinks. Although forest recovery on abandoned agriculture land is a process outside the forest, and by that the term natural afforestation is more appropriate, many researchers describe this process as natural reforestation. The dynamic outcome of natural reforestation of abandoned fields depends on several inputs, with seed dispersal and agricultural use as the most important, while other variables include soil conditions, vegetation cover, pests and animal presence, and time since land abandonment (Tasser et al. 2007). The process of natural reforestation can have both positive and negative consequences, depending on geographical and economic context and on the scale of the sites (Sitzia et al. 2010). Natural reforestation results in changes of fire susceptibility, water regime, soil erosion susceptibility, landscape, and biodiversity. In addition to environmental, the abandonment of agro-pastoral practices can have negative impacts from an economic and social perspective, as well (Sallustio et al. 2015). From forestry perspective, there are issues regarding the structure and species composition in forests from natural reforestation. At abandoned sites, or at sites cleared of forest, in some cases invasive and so-called pioneer species are established first. This can significantly slow down, and even prohibit the establishment of more valuable late successional tree species. These types of forests are hard to manage, and they have a low economic and ecological value, although they can have some social value providing the source of fuelwood and other wood products in short time.

Active Reforestation

Reforestation by Assisted Natural Regeneration

Natural regeneration of forests can be assisted by a number of silviculture practices, including selective cutting with leaving only a selected seed trees, protecting and nurturing the seed trees, enhancement of seed dispersal, seedbed preparation to promote seed germination, tending the naturally established seedlings, vegetation control, animal control, enrichment planting by direct seeding or transplanting of wildings (natural regenerated plants from neighboring forest), and sometimes planting of nursery seedlings. The choice of silviculture systems depends on the target species to regenerate, and these systems range from clear-cut to shelterwood.

Assisted natural regeneration aims to enhance the establishment of secondary forests and to accelerate natural succession process. Although it is labor intensive, assisted natural regeneration is more cost-efficient compared to planting, more productive compared to natural regeneration, and can provide jobs for local communities.

Reforestation by Direct Seeding

Direct seeding is the oldest method used for reforestation, with first references from fourteenth century (Willoughby et al. 2004). The use of direct seeding for reforestation and forest restoration was on peak in nineteenth and in first half of twentieth century, but declined with development of nursery programs for production of good quality seedlings. At beginning of twenty-first century, the use of direct seeding is widely considered, for achieving the large-scale forest restoration targets worldwide.

Major merit of using direct seedling in restoration programs is possibility to quickly cover the large areas at a relatively low cost. Other merits are ecological (easier mixture of species compared to planting of seedlings, increased species richness, development of non-uniform and complex forest stands), biological (development of a more natural root system compared to planted seedlings) and operational (rapid reforestation of large areas, on remote, inaccessible, and hard to plant seedlings sites, use on low-productive or disturbed sites, and in low-budget restoration programs).

Despite lower cost (average cost of direct seeding per hectare is 30–38% of planting costs for planting of bare-root and container-grown seedlings), the seedling establishment rates are low (20% of seeds planted), and field performance is lower than planted seedlings (Grossnickle and Ivetić 2017). Establishment rate is driven by several variables, including seed parameters (seed source, seed germination rate and speed, seed size, seed dormancy, genetic variability of seed), timing of seedling (the best time for seeding is when site environmental conditions are least stressful), seeding practices (spot seeding, broadcast seeding, site preparation, seeding depth), microsite conditions (soil water availability during the germination and establishment phases, soil type), competitive vegetation (competition from site vegetation decrease establishment rate, but not all existing vegetation at planting sites should be considered weeds), and seed predation (diseases, insects and rodents).

For successful direct seeding program, seedbed receptivity, seed distribution, and seeding rate should be considered (Grossnickle and Ivetić 2017). Seedbed receptivity (i.e., the number of ideal seeding microsites and the ability to deliver seed to those sites, Fleming et al. 2001) can be improved by exposure of site areas with optimum conditions for seed germination and seedling establishment, i.e., by reducing or rearranging of ground cover, soil preparation, and vegetation composition. Highest stocking rates in direct seeding are achieved when seed is uniformly spread across the site (Grossnickle and Ivetić 2017), although uniform distribution pattern is hard to achieve with broadcast seeding. Of all mentioned variables driving the direct seeding success, the most easily controlled is seeding rate. The number of plants per area unit increases with seeding rate, but only to certain threshold. The recommended operational seeding rates are high, due to the low-expected establishment rates, and can go up to 300,000 seeds ha−1, depending on species, seeding practices, and soil preparation (see Grossnickle and Ivetić 2017 for more detailed review).

Reforestation by Planting of Seedlings

A successful reforestation by planting of seedlings depends on knowledge of site and targeted species biological characteristics, appropriate selection of species, provenance, and planting material, preplanting site preparation, planting technique, and postplanting culture practices.

Site Characteristics

At the very beginning of any reforestation program, the site should be assessed from ecological and silvicultural aspect. In managed forests, most of site characteristics are known, but field study is necessary to get the real knowledge about site conditions. The site assessment should include soil characteristics, present vegetation, and climate. Soil productivity depends on nutrient status and capability, as well as on watering and drainage regime. In some cases, reforestation can be facilitated by present vegetation, but in most cases, it is a serious constrain, mainly by competition for light, water, and nutrients, and by risks connected with forest health. The presence of wildlife also needs to be assessed, especially of those animal species which can cause mechanical, and more significant, damage by browsing. Together with averages, the most important climate data for focal site are extremes of air temperature and precipitation. Combined with knowledge on physical characteristic of the site (inclination, exposure), these data can help in recognition of microsites, which are potentially under risk of frost, drought, and overheating by insolation. In addition to averages and recorded extremes, a prediction of future climate should be considered and used as a reference for defining the project goal and for decision for species selection and composition.

Species Selection

Reforestation projects are mainly site-specific, and the main goal (which can be prevailing productive, conservative or ameliorative – Ivetić and Devetaković 2016) defines requirements for the best planting material to use (species, provenance, level of genetic diversity, and quality). If the main goal of reforestation project is prevailing productive, sometimes the site production capacity can be better utilized by introduction of new genes (species, provenances). Opposite, when the prevailing goal is conservative; the usual practice is to re-establish the same species using reproductive material of local provenances. In degraded forests, the prevailing goal of reforestation is ameliorative, and fast-growing pioneer species can be introduced after a clear-cut harvesting, with a goal of facilitating the introduction of late-successional species.

In uncertainty of climate change, maintaining the current state or restoring a previous forest structure and composition will be more difficult, and the primary objective of forest restoration should be focused on functional ecosystems at the landscape level (Stanturf et al. 2014). This emphasizes the significance of species selection for reforestation. For a successful reforestation project, the species’ biological characteristics must match the site conditions, environmental issues, management goals, economic criteria, and climate change predictions (Ivetić and Devetaković 2016). In projects aiming at establishing mixed forests, species selection is even more complicated, because in addition to matching the site, current and predicted conditions, species in the mixture need to match each other in several aspects, like growing rates, light requirements, shade-tolerance, and root architecture. Species selection in reforestation programs is possible due to fact that most forest sites can support more than one tree species.

Provenance Selection

After the species selection, selection of appropriate provenance of reproductive material determines the long-term success of reforestation project. Despite the fact that the most of total genetic variation of forest tree species lies within populations, due to local adaptation and differences in phenology, provenances show different growing rates and different tolerance and resilience to biotic and abiotic stresses and can respond differently to climate change.

The usual reforestation practice is to use the reproductive material from local populations, but this approach is questioned from both spatial and temporal aspects. Except in cases of collecting of seed prior to clear-cut harvesting, the question “How local is local?” and “whether genetic variation within populations is more or less of a concern then local adaptation” (McKay et al. 2005) are important to consider. In some cases, local provenances (and even species) will not be necessarily the best adapted to changing climate conditions, and distance provenance need to be selected to matching to the focal site. A number of provenancing strategies have been suggested as response to predicted climate change, including local, predictive, composite, admixture, and climate adjusted provenancing (as reviewed by Ivetić and Devetaković 2016). No single strategy is likely to work universally, and selection of provenance(s) should be based on species genetic variation and local adaptation combined with climate projections for focal site.

Planting Material: Seedling Quality

Success of the reforestation project strongly depends on seedlings quality (genetically, physiologically, and morphologically). Unfortunately, at operational level, it is quite often that the material available in nurseries is used for reforestation, regardless to the well-documented effects of seedling quality on the final outcome. In order to increase reforestation success, selection of planting material should be based on management goals, site conditions, and planting conditions (i.e., tools and labor available), with site conditions as the most important since they can have a decisive effect on seedling survival. The selection of appropriate planting material is especially important on harsh site conditions. Seedling stocktype (determined by seedlings’ age and production method) have a stronger effect on harsh sites compared to more optimal site conditions. In comparison of two basic stock types distinct on production method (reviewed by Grossnickle and El-Kassaby 2016), container seedlings have a higher survival in a predominant number of trials (61%) than bareroot trials (15%).

Reforestation success can be significantly improved by implementing of the Target Plant Concept (Landis 2011; Dumroese et al. 2016), with a project-specific definition of seedling quality and nursery culture adopted to produce seedling with required attributes. At operational level, seedlings morphological attributes are mostly used for quality assessment. This is because they are relatively simple and nondestructive to measure, and they can forecast seedling survival and growth after field planting with different reliability and for different numbers of years. Information about relation between seedlings morphological attributes and their field survival and growth are used for improvement and implementation of nursery cultural practices that promote target seedling attributes and field performance. Such nursery culture that promote target seedlings attributes are (as reviewed by Ivetić and Devetaković 2016): sowing early in the spring, sowing and growing of seedlings at lower seedbed/container densities, drought conditioning by exposure of seedlings to drought stress, fertilization of seedlings in fall (“nutrient loading”), root conditioning by wrenching and root pruning, seedlings transplant for additional growth, production of seedlings in larger and deeper containers, hydrogel amendment, and inoculation with mycorrhizal fungi and plant growth promoting rhizobacteria (PGPR).

Preplanting Site Preparation
During the establishment phase, seedlings survival and growth strongly depends on site environmental conditions, and only a good quality site preparation can provide opportunity for reforestation success. There are several practices for site preparation which can be used and combined:
  1. 1.

    Removing and/or rearrangement obstacles and residue (i.e., stones, stumps, branches, and logs). This operation can be done mechanically or manually; with goal of allowing easy movement on the site and planting the total area with a regular layout and spacing. Organic residuals can be burned on-site, or removed and used for other purposes (i.e., chipped and used for energy production). At some sites, obstacles and residuals can be rearranged to create the favorable micro-site conditions for seedlings (for example, planting of seedling on the shaded side of stump, log, shrub, or large rock).

     
  2. 2.

    Vegetation control. One of the most important operational practice for preplanting site preparation is control of competitive vegetation. This operation can be done chemically, mechanically, and manually, depending on available equipment and legal restrictions. The combination of mechanical and chemical vegetation control provides the best results. It is important to notice that not all vegetation present at the planting site should be considered as weeds and competition – some plants can facilitate the seedling establishment.

     
  3. 3.

    Soil preparation. Subsoiling, mechanical terracing, and mechanical or manual preparation of planting holes are usual soil preparation practices. Soil preparation aims on improving soil characteristics and to promote seedling establishment by rapid growth of planted seedling root to surrounding soil. Soil preparation has a decisive effect on reforestation success on sites with harsh environment conditions. Technique used depends on site characteristics, seedling stocktype used, and available equipment.

     
  4. 4.

    Water harvesting. On slopes and in arid regions, additional site preparation practices are done with goal of water harvesting, usually by making of reverse slope, by different versions of bench terracing. This reverse slopes can redirect water to the seedling and reduce erosion by intercepting of runoff. This practice can be performed on a planting spot or a whole site level, depending on site conditions.

     
  5. 5.

    Facilitation by nurse plants. On some sites, especially in arid and subarid regions, planting of seedling under the shade and protection of, so-called, nurse plants can promote survival and growth. The phenomenon that some plants benefit from closely associated neighbors is known as facilitation (Padilla and Pugnaire 2006). Facilitation by a nurse plant is stronger at low altitudes and sunny, drier slopes, compared to high altitudes and shady, wetter slopes (Gómez-Aparicio et al. 2004). On bare sites without suitable nurse plants, they can be planted before or simultaneously with tree seedlings. These nurse plants can be shrub or tree species, but only species with limited growth and resource demands can be selected and planted as a nurse plants.

     
Planting
Planting is the most critical act in reforestation project. Improper planting can depreciate time and efforts invested in seedling production. Sometimes, the improper planting is obvious reason of reforestation failure, but sometimes the effect of the planting method may not be visible until the first stress event. Basically, appropriate planting is putting and positioning seedling into the planting hole in a manner which promote seedling establishment and growth. Some of the general planting rules are (Ivetić 2013):
  1. 1.

    Always use the planting spots with best microsite conditions, including the shade and protection of material present at planting site (i.e., rocks, stumps, and nurse plants).

     
  2. 2.

    The planting hole needs to be deeper than drying zone during the critical dry period of year.

     
  3. 3.

    On wet sites, seedling should be planted on a previously prepared mound.

     
  4. 4.

    On dry sites seedling should be planted below general terrain level, in the trenches or at the bottom of the furrow.

     
  5. 5.

    The seedling should be planted upright and positioned on a way that root collar is in line, or 1–2 cm deeper of ground line.

     
  6. 6.

    When filling the planting hole, make sure that the best soil is rolled up to the root.

     
  7. 7.

    After filling, the soil around the seedling should be firmly tamped down, in order to eliminate possible air pockets.

     
The appropriate planting method depends on the site environment conditions and seedling stocktype, and different tools are developed for different combination of these variables. In addition, use of the following practices can promote seedling survival and growth (Ivetić and Devetaković 2016):
  • Increase of planting depth. Although effect of planting depth is species specific; deep-planting techniques promote seedling establishment on dry sites by positioning of root in capillary moisture soil zone.

  • Increase of nutrient availability. Decision on whether to fertilize or not should be project specific, and based on knowledge of variables like: soil conditions, competitive vegetation, site drought level, and seedling species demands. Because of possibility that that fertilization will stimulate competitive vegetation, fertilizer should be applied close to the seedling root system. Fertilization at planting can be done by organic and mineral fertilizers. For using controlled-release fertilizer, their general characteristics (i.e., formulation and release behavior), as well as their and interaction with soil and plant environment should be tested, because in some cases, they can have a negative effect on seedling performance.

  • Inoculation with mycorrhizal fungi and PGPR at planting. Given to their proven positive effect on seedling survival and growth, especially inoculation of seedlings with mycorrhizal fungi and PGPR are promising techniques on sites with shallow or no soil profile, and with contaminated soil. Although seedlings can be inoculated in nursery, the simplest and cheapest technique for promoting mycorrhization at planting site is addition of forest soil to the planting hole.

  • Amendment of superabsorbent polymers. Application of superabsorbent polymers (hydrogels) during planting shows contradictory results, and their use should be tested on a small scale in a specific site-species combination before use in large-scale reforestation projects.

  • Irregular planting pattern and density. Planting of seedlings at planting spots with best microsite conditions, which deviates from regular layout and density, results with close-to-nature appearance, but also can promote seedling survival, as it is shown in sections on Preplanting Site Preparation and Planting.

Postplanting Culture
On poor quality sites with droughty conditions, but also on higher quality sites with risk of competitive vegetation and browsing, intensive silviculture in first couple of years after planting is critical for reforestation success. There is a number of postplanting silviculture practices for improving microsite conditions and protecting planted seedlings (Ivetić and Devetaković 2016):
  • Vegetation (weeds) control. During seedling establishment phase, it is essential to reduce the competitive vegetation on minimum. Effect of existing vegetation on planting site can be twofold and not all plant species present at planting sites should be controlled, because some species can act as a nurse plants and facilitate seedling survival and growth (see sections on Preplanting Site Preparation). Only those herbaceous and woody species that compete with planted seedlings for energy, water, and nutrients should be considered weeds. Vegetation control at the planting site increase survival rate of small seedlings and growth rate of large seedlings. Control of herbaceous species after field planting has more effect than control of woody species. At planting site, weeds can be controlled physically (mulching), mechanically (cultivation), and chemically (herbicides). Efficiency of vegetation control depends on method and size of the control area. The most effective is chemical control by herbicides, but combining of methods can result with synergic effect. In addition, increasing in controlled area has positive effect on reforestation success.

  • Mulching. Cover of soil around newly planted seedlings by spreading of appropriate material can mitigate extreme temperatures, improve soil water availability, structure and fertility, and reduce weeds. Mulching effect is a site specific, and depends on mulching material, size, cost, and longevity.

  • Sheltering of planted seedlings. At planting site, the newly planted seedlings can be physically protected by tree shelters, which, depending on material and design, can improve environment conditions next to the seedling. The effect of tree shelters depends on material, design, color, and size. Although many evidences suggest that solid-wall, light-colored tree shelters are among the best in optimizing environment conditions right next to the seedling (inside the shelter), and providing of physical protection, with the wide variety of products on the market, different shelters should be tested for particular site to species combination.

  • Browsing control. At some sites, animal damage can have a decisive effect on reforestation success or failure. The negative effect of animal damage is stronger at sites with harsh environment conditions. Browsing control at the planting site can be done by physical protection or by use of chemical repellents. Fencing the entire planting site is usually not cost effective, and require regular monitoring and interventions. Because of that, and with development of new products and solutions, individual seedling protection is prevailing in reforestation projects. These products include tree shelters (plastic tubes) and guards (meshes, wires, bud protectors, etc.). Chemical repellents generally rely on fear, conditioned avoidance, pain, or taste. As alternative to industrial chemical repellents which can be highly cost, the low cost kitchen recipes which are less effective and durable, but easy and inexpensive to produce, can be used.

Reforestation Challenges and Future Perspectives

At Conference on Reforestation challenges held in Belgrade 2018, the following reforestation challenges and perspectives are recognized (Ivetić 2018):
  • Uncertainty of environmental changes. In order to improve services to the public, focus of reforestation should be on restoring critical ecosystem functions and services, rather than attempting to restore the forest structure to some historical reference. Only high-quality seedlings, following the Target Plant Concept, outplanted at the right place and at the right time will build the resilient and sustainable forests in the changing future. For some tree species, assisted migration will become a standard tool in helping them to keep up with the pace of changing climate. National legislations should relax the administrative borders in cases of transfer of forest reproductive material, because in some cases the seeds, seedlings, and genes matching the best to the target site, can be found across these borders.

  • Production of enough reproductive material of a good quality for ambitious reforestation and forest restoration programs. Appropriate seed source selection, seed collection, and processing are vital step in production of planting material, and new seed sources should be established, and seed collecting and processing should be adapted to changing environment and growing demands.

  • Neglected significance of nursery production. Because only the best nursery practices will result with high quality seedlings, more effort should be invest on recognition of significance of nursery good practices in success of reforestation. Nursery techniques, such as the use of LED lights and chemical root pruning, which are less expensive compared to genetic engineering, can be used to produce the New Generation Seedlings. These seedlings, capable to build a new, resilient forest at the single tree, stand, and landscape levels.

  • The establishment phase of seedling establishment will become more critical in the future at some sites. The final outcome of seedling facing the site conditions depends on a combination of seedling quality and the level of environmental stresses. A good knowledge and understanding of ecophysiology need to be transferred to operational level in order to improve the decision making process (planting material selection and handling, site preparation method, and time of planting) and to increase the success at the end. Seedlings field performance at the outplanting site can be promoted by different tools and techniques, including inoculation with mycorrhiza spores, vegetation control, and protection from grazing, the early recognizing of symptoms of diseases and pests and with on time reaction to protect the seedlings.

  • Changing environments brings new challenges to the traditional silvicultural approaches. Facing the changing environments, more attention should be focused on species phenology. The need to modification of existing and introduction of the new techniques of site preparation and vegetation control will grow in the future.

  • Facing the failure. The failure of reforestation programs have a range of negative consequences. A new sets of procedures (“Seedlings Forensics” and “Planting Site Investigations”) need to be developed for collecting the evidences to ascertain the reasons for failure in order to better understand what went wrong and to learn from a failure.

Many methods and techniques used in reforestation are tested and proven at the operational level. However, in uncertain global change, there is a constant need for new techniques and methods which open opportunities for new research and inventions.

Cross-References

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Faculty of ForestryUniversity of BelgradeBelgradeSerbia

Section editors and affiliations

  • Sharif Ahmed Mukul
    • 1
  1. 1.Department of Environmental ManagementIndependent University, BangladeshDhakaBangladesh