Keywords

1 Introduction

Peatlands cover a large area of Indonesia—around 14.9 million ha (Ritung et al. 2011). After the catastrophic fires in 2015, the Indonesian government targeted the restoration of at least 2 million ha of burnt peatlands between 2016 and 2020 (The Presidential Instruction—Inpres No. 1/2016). A nonstructural agency was developed, namely, the Peatland Restoration Agency (Badan Restorasi Gambut, BRG)Footnote 1 which was mandated to plan and implement the restoration of the degraded peat ecosystem. This demonstrates the government’s commitment to restore degraded peatlands and mangroves and combat peat fires and the haze hazard.

Peatland restoration aims to restore degraded burnt peatlands by applying three approaches: rewetting, revegetation, and revitalization of the community. Rewetting is an effort to rewet the drained peatland by increasing the water content of the peat and raising the ground water level. Revegetation includes wide scope for rehabilitation and replanting the degraded peatlands to improve land cover and economic benefits (BRG 2017a). Page et al. (2009) suggested three similar actions in addition to restoration of the carbon sink and reduction of greenhouse gas emissions. In fact, maintaining a high water table through rewetting and increasing carbon stocks through revegetation can be used to achieve the target of emission reduction (Ritzema et al. 2014; Jauhiainen et al. 2016; Wilson et al. 2016).

The regulation signed by the Minister of Environment and Forestry (number P.16 in 2017) on technical guidelines for the restoration of the peatland ecosystem states that the number of trees planted and have survived in the third year after planting should be at least 500 trees per ha−1. The Minister formally stated that the survival rate of revegetation in peatland restoration should be 90% (Ministry of Environment and Forestry 2018). In a comprehensive review of peatland restoration, Dohong et al. (2018) stated that the early survival rate of revegetation in the Mega Rice Project of Central Kalimantan Province varied between 65% and 85%. They highlighted the need to formulate future revegetation efforts with a strategy appropriate to peat forests. In addition, Page et al. (2009) asserted that the obstacles in revegetation include finding viable planting stocks that are suitable for temporarily high waterlogged and dry peatlands. The authors suggested maintaining the ongoing vegetation monitoring in restoration, investigating ecological barriers to tree species regenerating in degraded peatland, and gaining a better understanding of hydrological tolerance in times of drought and in the wet season. Neither article, however, discussed genetic diversity and genetic sources as the criteria for species used in restoration.

Landscape restoration aims to improve the genetic diversity of plant populations to recover the characteristics of species composition and diversity (Brancalion et al. 2011). Restoring a landscape with multifunctionality requires multiple species. Focusing on the functional diversity of tree species is more important than species per se (Aerts and Honnay 2011). In a degraded and burned peatland landscape, the mother trees are not available and genetic materials are disrupted. Therefore, obtaining viable seeds and seedlings is the main constraint (Brancalion et al. 2011).

In peatland landscape restoration, diversity at the gene level is rarely observed. It is necessary to take into account the genetic variation of a species and the variety of plant species planted (Bischoff et al. 2010; Thomas et al. 2014a, b). Genetic diversity is positively related to the vigor of the tree population, its flexibility, and its ecosystem functions (Reynolds et al. 2012; Thomas et al. 2014a, b). High genetic diversity of plant populations is a fundamental factor in ensuring the long-term success of restoration (Brancalion et al. 2011). The failure of revegetation in peatland restoration is may be caused by low genetic diversity within a species (Thomas et al. 2015).

There are many native peatland tree species; however, information on genetic diversity is very limited. Some reports have shown the genetic diversity of three important tree species that those are naturally grown on peatlands, namely, Gonystylus bancanus (Ogden et al. 2008; Widyatmoko and Aprianto 2013), Shorea macrophylla (Kanzaki et al. 1996), and Dyera polyphylla (Wahyudiningsih et al. 2014; Tata et al. 2018). D. polyphylla is widely used in peatland restoration in Indonesia (Tata and Susmianto 2016; Tata et al. 2016). Many other tree species used in peatland restoration merit further study.

This study, which was based on literature review and field observation, aims to highlight the importance of genetic diversity. In addition, we discuss some community-based seedling nurseries of native species in Jambi and Central Kalimantan that provide planting stocks for peatland restoration. The nurseries of native peatland species are usually established by smallholder farmers, who usually collect seeds from wild and planted populations, which will affect the genetic variation of the seedlings.

2 Planting Stocks for Peatland Restoration

Following the destructive peat fires in 2015, a series of investigations were conducted in the peat swamp forests in Kerumutan in Riau Province, Kepayang in South Sumatra, and Tumbang Nusa in Central Kalimantan. There is no doubt that many big trees were destroyed in the fires. Figure 10.1a shows the state of the Kepayang peat swamp forest in South Sumatra after the fire. Only a small patch of forest area survived, in which some mother trees were still alive. A year after the fire, some tree species (such as the Euphorbiaceae family) were able to sprout and recover quickly, obviously having suffered a low impact from the fire (Fig. 10.1b). However, the physiology of the threes affected by the fires has not been determined.

Fig. 10.1
2 photographs. A. Fully grown trees without any leaves in front of a pond water. B. A worm-view of a large tree sprouting new leaves.

(a) Severely burnt peat swamp forest in Kepayang, South Sumatra; (b) Sprouting tree a year after the fire

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Peatland degradation has been characterized based on the change in peatland components, for example, plants, water, and peat, from minimal up to maximal level. These characteristics determine the restoration strategy. Restorability is decreasing in contrast with the degradation level (Joosten 2016). The peatland restoration action is determined by multiple factors, such as level of degradation, location of the peatland in the peatland hydrological unit, and its area status. Although in the regulation, the BRG was mandated to restore million ha of degraded peatland, after reassessment and remeasurement were carried out, the peatland restoration target in Indonesia increased to 2.49 million ha in seven provinces (BRG 2017b). The area and peatland distribution to be restored are shown in Fig. 10.2.

Fig. 10.2
A cluster bar graph illustrates B R G target of protection area, cultivation area with permit, cultivation area without permit in seven provinces are Riau, Jambi, S. Sumatra, W, C, S. Kalimantan, and Papua. The cultivation area with permit is highest in Riau, protection area, cultivation area without permit, and protection area are highest in C. Kalimantan.

Restoration target of BRG in seven provinces (Source of data: BRG 2017b)

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The BRG has classified the target of the three actions in all the target areas. This study focuses on revegetation, which consists of full revegetation, enrichment planting, and natural regeneration. Revegetation is determined by the level of peatland degradation (BRG 2017a).

  1. 1.

    Natural regeneration is applied when the level of degradation is low, and the canopy cover is >50%. The peatland condition allows the recolonization of native forest species, recruitment of indigenous species, and seed dispersal mechanisms.

  2. 2.

    Enrichment planting is carried out when the level of degradation is moderate, and the canopy cover is between 25% and 50%. In this condition, unassisted regeneration may occur; enrichment planting is recommended to accelerate vegetation cover and to enrich tree diversity.

  3. 3.

    Revegetation (100% planting) is used when the level of degradation is high, and the canopy cover is <25%. Assisted regeneration with native tree species is necessary.

The BRG has calculated the target area for revegetation in seven provinces of Indonesia. The four important stakeholders responsible for revegetation are shown in Table 10.1.

Table 10.1 Areas for revegetation and responsible stakeholders (Source of data: BRG 2017a)
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The degraded peatland area to be revegetated is 146,779 ha, and the area for enrichment planting is 335,287 ha. According to the regulation, revegetation should have at least 500 trees/ha that have survived in the third year after planting. The assumption is that enrichment planting only needs 50% trees to be planted in the area for revegetation. If we use a survival rate of 90% yearly, a total of 617 viable seedlings/ha are needed. Therefore, the total number of viable planting stocks (either seedlings or cuttings) required for revegetation is about 90.56 million, and for enrichment planting, it is 103.44 million (in total, 194 million), which is a large number of planting stocks. The intriguing question then becomes: How might we provide the required number of viable planting stocks? Large areas of peat swamp forest have been burnt and degraded, and the standing stocks or mother trees in the natural population are scarce and scattered in patchy areas.

3 Avoiding Failure in Revegetation in Peatland Restoration

There is increasing awareness of the importance of planting native tree species in certain ecosystems for restoration. The native species are already adapted to the environment, which improves the success of restoration efforts and thus ecosystem functions (Bischoff et al. 2010; Kettenring et al. 2014). However, the origin of the species alone is not enough. The native species used in restoration should have high genetic diversity and the appropriate germ plasm, as this significantly increases the survival rate from the first year and over time (Broadhurst et al. 2008; Bischoff et al. 2010; Thomas et al. 2015). It has been found that small increase in the genetic diversity of species used in restoration positively enhanced ecosystem services, such as habitat quality, primary productivity, and nutrient retention (Reynolds et al. 2012).

On the other hand, using low-quality materials in revegetation results in high mortality, poor growth, susceptibility to environmental condition, and low reproductive success. These failures may not be evident in the early growth, but become apparent as the trees mature (Bischoff et al. 2010; Thomas et al. 2015). Self-pollination—mating with the offspring—can considerably affect survival and thus lead to genetic drift (Bischoff et al. 2010).

The revegetation project in the peat forest reserve (Hutan Lindung Gambut, HLG) of Bram Itam in Jambi used D. polyphylla of which the origin was unknown. However, the genetic analysis revealed that the seedlings were likely brought from Central Kalimantan. The diversity of D. polyphylla planted in the HLG of Bram Itam was relatively high (H′ = 0.35) (Tata et al. 2018). The growth of planted D. polyphylla was good: at 7 years after planting, the stem diameter at the breast height had reached 11.2 cm (Tata et al. 2016). This supports the statement of Reynolds et al. (2012) and Thomas et al. (2015).

Wild populations of particular species are usually used as seed sources for forest and landscape restoration. A population in a fragmented and isolated ecosystem may have low genetic diversity owing to limited gene flow. However, in the multifunctionality of landscape, such as agroforestry systems, the gene flow could be increased (Thomas et al. 2015; Tata et al. 2018).

4 Sourcing Germ Plasm for Peatland Restoration

The principle in sourcing germ plasm for peatland restoration is using high quality and genetically diverse seeds to maximize the adaptive potential of restoration efforts. Using local seeds may lead to unsuccessful restoration (Broadhurst et al. 2008) for a number of reasons, for example, the low genetic diversity of the local seeds, which come from a fragmented and isolated population. The isolated habitat may lead to self-pollination, which reduces genetic variation. Tata et al. (2018) reported that several wild populations of D. polyphylla from Senyerang and Sungai Aur in Jambi and Tumbang Nusa in Central Kalimantan maintain high genetic diversity since their habitats were surrounded by a complex system of agroforests. An isolated and degraded population of D. polyphylla, such as the wild population in Rawasari Jambi, has lower genetic diversity (Tata et al. 2018). Habitat fragmentation may influence pollinators and their behavior, which leads to reduced outcrossing and higher inbreeding (Broadhurst et al. 2008). Wild populations of D. polyphylla in Senyerang and Rawasari in Jambi are shown in Fig. 10.3.

Fig. 10.3
2 photographs of fully grown long trees in the forest.

The habitat of a wild population of swamp jelutung (Dyera polyphylla). Both populations are used as a seed source for peatland restoration in Southern Sumatra. (a) Rawasari, Tanjung Jabung Timur, (b) Senyerang, Tanjung Jabung Barat, Jambi

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5 The Community-Based Nursery

Several community-based nurseries (Kebun Bibit Rakyat, KBR) especially for peatland native species have been established in various villages in Sumatra and Central Kalimantan to provide planting stocks for peatland restoration and to encourage farmers to plant native species in peatlands (Fig. 10.4).

Fig. 10.4
5 photographs. a. display board with text in foreign language. b, d, and e different photo view of seeding in a community-based nursery, seeding in Tumbang Nusa nursery, and seeding in Hampangen Central Kalimantan c. Jelutong tree planted in a straight line, surrounded by different types of fully grown trees.

Community-based seedling nurseries in Jambi and Central Kalimantan: (a) Rimba Lestari forest farmer group; (b) Jelutung seedlings in a community-based nursery (KBR); (c) jelutung planted in Tanjung Jabung Barat; (d) jelutung nursery in Tumbang Nusa; and (e) nursery jelutung in Hampangen Central Kalimantan

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In Senyerang village (Jambi), the KBR was established by a forest farmer group (Kelompok Tani Hutan) called Rimba Lestari (Fig. 10.4a) and led by Saman. Some jelutung trees have been certified as mother trees of jelutung by the Forest Seed Technology Office (Balai Teknologi Perbenihan Hutan) (Tata et al. 2016). There are other native tree species in the patchy forest of Senyerang that can be developed as a seed source for peatland restoration, such as medang labu (Endospermum diadenum), asam kandis (Garcinia sp.), meranti batu (Shorea uliginosa), gemor (Alseodaphne sp.), and gaharu buaya (Gonystylus sp.). However, only three species, namely, asam kandis, jelutung, and medang labu flower yearly.

The KBR in Rawasari village (Jambi) was established and led by Lukman. Jelutung is the only species developed in the KBR (Fig. 10.4b). Other potential species, such as swamp pulai (Alstonia pneumatophora), could also be developed. In a field observation, there were some native species of peat swamp forest remains. A big canal was built in the area, which affected the hydrological and ecological conditions.

In Tumbang Nusa in Central Kalimantan, a seedling nursery of native species has become a business and a source of livelihood for the villagers (Fig. 10.4d, e). Four villagers living on the main road developed a seedling nursery and have been selling planting stocks (seedlings and wildings). Various native species are available, including jelutung (as the commonest seedlings), swamp pulai, gelam (Melaleuca leucodendra), petai (Parkia speciosa), kapur naga (Calophyllum sclerophyllum), and jangkang (Syzygium sp.). The villagers developed the nursery based on their own initiative, without any cooperation with a farmer group. Figure 10.4c shows a seedling vendor from Tumbang Nusa village. The seedling nursery was developed in an area of 1.4 ha. There were 75,000 seedlings (from various tree species) per ha. The mean price of one seedling was Rp3,000, and the gross revenue was Rp225 million (Sumarhani and Tata 2018).

In providing planting stock, community-based seedling nurseries could enhance peatland restoration in terms of the quantity of seedlings. As mentioned earlier, local species do not necessarily improve the quality of peatland restoration. It has been found that the use of 10–50 selected from healthy and viable individual trees per population and up to 50 populations per species is adequate (Broadhurst et al. 2008). The suitable sourcing strategies include compound provenancing, that is, collecting a mixture of seeds that try to follow gen-flow dynamics; and admixture provenancing, which involves collecting seeds from large populations and various environments, and mixing them before sowing. This generates new populations with a variety of genotypes of wide provenance (Broadhurst and Boshier 2014).

6 Conclusion

To achieve the target area of peatland restoration with a survival rate of 90%, there must be a sufficient quantity of high-quality planting stocks to ensure genetic value and plant health. The strategy should include combining seeds not only from local species but also from various environments. As reported by Tata et al. (2018), the planted jelutung in Tanjabar in Jambi and Tumbang Nusa in Central Kalimantan showed no loss of genetic diversity. It was used as a seed source for the recent peatland restoration in the two provinces. Villagers with a seedling nursery business should be made aware of the potential risk of genetic drift if they are collecting seeds from a few individual trees and a limited population. The correct strategy for seed sourcing should be explained to farmers to make them aware of the importance of genetic diversity in peatland landscape restoration.