Study of population distribution and benefits of Nipah (Nypa fruticans)

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Introduction
The mangrove forest zone closest to the sea (seaward zone) is usually covered by Avicennia sp. and Sonneratia sp.; areas close to land (landward zone) is usually dominated by Rhizophora sp., Bruguiera sp., and Xylocarpus sp.; and in the mainland zone (transition between mangrove forests and lowland forests) it is usually dominated by nipah (Nypa fructicans) and several other palm species [1,2].However, degraded mangrove forests will be dominated by invasive species such as nipah.This species is an indicator of mangrove forest degradation.Nipah has an explosive population because it can produce high seeds and is easily distributed under water currents so that it can suppress mangrove growth [3].
Almost all mangrove forests on the east coast of South Sumatra, including the Air Telang Protected Forest (ATPF), have been invaded by nipah.This event is an indicator that the mangrove forests in this region, especially the ATPF, have largely been degraded as a result of anthropogenic activities.If the ATPF is disturbed, nipah will easily invade almost all zones, from the tidal zone to the land zone.Nipah stands are found in both primary forest, secondary forest and disturbed primary forest in the ATPF; and dominates tree-level stands with an average species Importance Value Index (IVI) of 89.9% [4].This also happens in various regions of the world which shows that the Nipah invasion has explored areas outside its natural habitat [5][6][7].Nipah dominance can disrupt the functional mangrove forest ecosystem, especially due to changes in coastal environmental conditions physically, chemically and biologically [8].
Even though nipah palms can ecologically disrupt the balance of the ecosystem due to their invasive nature in disturbed mangrove forest areas, on the other hand nipah palms have ecological and economic functions.Nipah is able to stabilize soil in coastal areas; protect soil erosion due to waves and wind; as well as reducing the strength of cyclones and high sea waves in coastal zones [9].Parts of the nipah plant organs have been used by people living around the ATPF, including the leaves, stems and fruit; as well as earthworms associated with palm trees [8].In several places in the world, various organs of the nipah have been used to make various products such as fuel, medicine, food, clothing accessories, and so on.
This research aims to examine the ecology of nipah palm populations, especially in the ATPF and describe the benefits and potential of nipah palms both in the ATPF and in various regions in the world.It is hoped that the results of this research will be able to contribute information regarding population distribution, invasion and potential of nipah so that it can stimulate researchers to study more deeply about autecology and the benefits of nipah.

Description of the study area
The location of this research is the Air Telang Protected Forest (ATPF), Banyuasin Regency, South Sumatra, Indonesia, which is a mangrove forest covering an area of around 12,660.87 ha (Fig. 1).It has experienced a lot of degradation due to anthropogenic activities so that no more than 40% of the remaining primary and secondary forests remain [10].This protected forest and the surrounding area are being converted by the government, communities and companies to become coconut plantations, oil palm plantations, ponds, agriculture, settlements and ports.

Data collection and analysis
This research uses two types of data, namely primary and secondary data.Primary data was collected through direct surveys in the field.Field surveys were carried out by exploring the ATPF area which consists of secondary forests and areas that have been disturbed (ponds, open areas, shrubs, water channels and river banks).Direct survey data in the field is obtained through field descriptions and documentation of site conditions, especially the distribution of the nipah palm population and its association with other plants.Apart from that, interviews were also conducted with the community regarding its use by the community for various purposes.
Secondary data was collected through a literature review of previous research results, both regarding the distribution of the nipah population and its use by people in the world.The two types of data obtained were analyzed to determine population distribution, associations, invasion and benefits of nipah.

Distribution of the nipah population and its invasion
Nipah is a mangrove forest plant that thrives in relatively calm brackish water habitats containing sediment deposited due to the accretion process of sea water on the banks of rivers, bays, tidal areas of rivers and land areas during the ebb and flow of fresh water [11][12][13].This plant can tolerate areas that are rarely flooded as long as the soil does not dry out for long periods of time; and can grow inland as far as the tide can carry its floating seeds.The stems grow horizontally and new fronds grow quickly so they can stabilize the soil on river banks to prevent erosion due to waves and wind.The characteristics of the anatomical shape of the nipah organ can be seen in Fig. 2.  Nipah ideally grows in land zones in natural mangrove forest formations, namely the transition zone between lowland forests and mangroves [14].However, damage to mangrove forests, especially the reduction in trees, results in a reduction in mangrove root mass, so that floating nipah seeds will easily be carried away by tidal currents because there is no barrier in the form of mangrove roots.This facilitates nipah seeds to migrate along open areas carried by tidal currents by developing a few colonies at first and then becoming permanent residents [15].The development of a plant species, including nipah, is largely determined by the presence of seeds and carrier media such as water currents and wind.
Anthropogenic activities in mangrove forests have caused changes in plant population formation in various disturbed mangrove forest areas which do not conform to natural zoning patterns, where plants that have high adaptability will dominate the area, including nipah.Mangrove forest succession is greatly influenced by human activities, hydrographic changes, interactions of species in mangroves, geomorphological and environmental changes [16,17].
The results of our research show that nipah palms have invaded tidal areas (seawards) which should not be their natural growth areas.We found nipah palms associated with other mangrove species such as Avicennia alba and Rhizophora apiculata in the seaward region, we even found nipah palms to be the dominant species in the region (Fig. 3).In line with our previous research which showed an association of these three species to form the Nypa-Avicennia vegetation type [4].Anthropogenic activities have caused mangrove degradation on the east coast of the island of Sumatra [18], resulting in massive nipah invasion.Anthropogenic pressure on mangrove forests has caused the invasion of nipah palms which reduces the quantity of mangroves and other species on the coast, because nipah is capable of producing large quantities of seeds that can be distributed effectively and have the ability to adapt to the environment [3].
We also found that nipah invaded land areas, such as secondary forests, open areas and former pond areas (Fig. 4).Secondary forests are the result of succession from disturbed natural mangrove forests, while open areas are deforested areas that will be converted into plantation/agricultural land; or areas that are no longer used.Nipah is associated with plants at the trees and shrubs level in secondary forest areas, while in open areas and former ponds it is associated with shrubs.Open areas are the largest areas in the ATPF as a result of logging or forest fires, reaching half of the total area of this protected forest [10,19].The presence of nipa in the ATPF is found in almost all sampling locations, from primary forest to secondary forest [4].The nipah palm invasion can replace the existence of the mangrove population, thereby hampering the succession process.The loss of mangroves has an impact on changing the character of the habitat.Nipa palm invasion can inhibit water circulation which has an impact on increasing sedimentation and inhibiting waste circulation, thereby reducing substrate quality.Mangrove forest succession can be hampered by the loss of mature trees; and biological invasions such as nipah palm invasion, which inhibits the growth of mangrove propagules [20].This will also have an impact on disrupting the spawning process of aquatic biota, such as fish and shrimp, thereby reducing fisheries productivity; as well as causing ecological problems [3,21].In addition, damage to mangrove forests can reduce the amount of carbon stocks in the forest and at the same time increase greenhouse gas emissions [19,[22][23][24]; as well as reducing the diversity of flora and fauna species in it [25].

Benefits of nipah for coastal communities and research developments
Ecologically, nipah palm invasion in ATPF can disrupt the balance of the mangrove forest ecosystem.However, nipah also has economic value for coastal communities who use it as a form of local wisdom.The use of plants by the community (ethnobotany) is important to study to explore the potential of plants and at the same time study ecosystem services for local communities [26].People living around the ATPF use parts of the nipah plant in the form of leaves, stems, fruit and worms associated with the nipah roots.The people there use palm leaves to make roofs for their houses (Fig. 5); the stems are used as building materials, bridges, and firewood; and the flesh of the fruit (Fig. 6) is eaten [8].Table 1.The use of nipah by the community and the content of various compounds in it.

Parts used
Used for/contents Sources Leaves Whole leaves Raw material for roofing houses [8,27] Cuticle of young leaves Tobacco wrapping material for making cigarettes [8,27,28] Fresh leaves Inhibits the corrosion of zinc [29]

Dry leaves
Used for fuel [9] Shoots Able to sorption Pb2+ and Cu2+ ions [30] Shoots For worm killing poison because it contains vermicide [9] Young shoots Used against herpes [9] Fronds Produces pure cellulose for fuel [31] Fruits Fruit flesh (mesocarp) Content of carbohydrate, crude protein, crude fat, insoluble and soluble fiber, phenolics compound [32] Fruit flesh (mesocarp) Content of phenolics, flavonoid and antioxidant [33] Fruit flesh (mesocarp) Starch raw materials containing carbohydrates [34,35] Fruit fiber Raw materials for making briquettes (fuel) [36][37][38][39][40][41][42][43] Fruit shell Raw materials for making briquettes (fuel) [41][42][43] Fruit shell For making buttons, necklaces and other clothing accessories [9] Fruit shell Heterogeneous catalyst in biodiesel synthesis [44] Sap For making alcohol, molasses, vinegar, syrup, granulate sugar [27,28,45] Sap Contains anti-diabetic compounds and antioxidants [9,45,46] Sap Rich in glucose, sucrose, fructose, minerals, vitamins, organic compounds and antioxidant activity [47][48][49] fruit residues Used for fuel [9] Tree Fiber Raw materials for making particle board [50] Fiber Raw materials for making briquettes (fuel) [43] Stem wood Used for fuel [9] Roots Rhizomes Floats for fishing nets to float above the surface of the water [9] Roots Associated with nipah worms which are useful for fishing bait [8] We have collected various research literature in various places which shows that nipah has enormous benefits (Table 1).The part of the nipah plant that is commonly used by the community is the leaves which can be made into roofs and cigarette wrappers; and the sap can be used as alcohol [27], and the fiber is used as raw material for particle board [51].The shells and fibers of nipah fruits have the potential as an energy source by using them as charcoal briquettes through a certain process [36][37][38][39].Nipah contains high levels of cellulose and hemicellulose, namely around 28.9-45.6%and 21.8-45.6%respectively, so it has potential as an energy source [51].Trees, fruit bunches, and fruit peels of nipah can also be processed into charcoal briquettes [42,43].Apart from that, nipah also has the potential to be used as a source of food and medicine.Nipah sap contains a lot of sucrose, glucose, fructose and organic compounds with a high content of minerals, vitamins and antioxidant activity which have many benefits for human health [50].

Conclusions
The nipah population can spread widely in disturbed mangrove forest ecosystems and it can dominate areas outside its natural habitat because it has a high ability to adapt to the environment; has high seed productivity; and effective and adaptive seed distribution.Although widespread nipah palm invasion can hamper the succession of mangrove forests, nipah palm has great benefits for coastal communities and contains important compounds for food, drink and medicine.

Fig. 3 .
Fig. 3. Nipah population in the seaward area which is not its natural habitat.A and B show the association of nipah with other mangrove plants; C and D show nipah dominates in this habitat.

Fig. 4 .
Fig. 4. The nipah population in the mainland area is the area of the former pond channel (A), secondary forest (B) and open areas (C and D).

Fig. 5 .
Fig. 5. Nipah leaves are used to make roofs of houses.Nipah leaves collected by craftsmen (A) and house roof products made from nipah leaves (B).

Fig. 6 .
Fig.6.Characteristics of nipah palm fruit.Nipah fruit that has been removed from the bunch (A), nipah fruit that is still in the bunch (B), nipah fruit that has been split into 2 parts with white flesh (C).