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http://www.scilit.net/article/10.1155/2014/898494
Published: 1 January 2014
International Journal of Forestry Research, Volume 2014, pp 1-8; doi:10.1155/2014/898494
Abstract: Forest over logging, forest fire, forest conversion, and opencast mining have promoted deforestation in Indonesia, and reforestation is needed immediately. However, reforestation is limited by low seedling quality and production, and slow seedling growth in nurseries. Native tropical tree and fast-growing species, Mallotus paniculatus and Albizia saman, are potential to promote the first rotation of reforestation. Arbuscular mycorrhizal (AM) fungi are known to promote nutrient uptake and plant growth. We examined the effects of two native AM fungi, Gigaspora decipiens and Glomus clarum, on the growth of M. paniculatus and A. saman seedlings under nursery conditions. At harvest, after six months, we determined AM colonization, shoot dry weight, and shoot N and P concentration. Approximately 90% and 50% of M. paniculatus and A. saman roots, respectively, were colonized by AM fungi, without any difference between the inoculation treatments. G. decipiens and G. clarum increased shoot height, leaf number, shoot dry weight, and shoot N and P uptake of both species. A positive correlation was observed between N and P uptake and shoot dry weight. These results suggest that AM fungi are effective in accelerating nutrient uptake and plant growth, which will, in turn, promote reforestation and sustainable forest timber production.1. IntroductionIn Indonesia, deforestation is occurring rapidly owing to over logging, forest fire, forest conversion into agricultural land or oil rubber plantation [1], and opencast mining [2], and, therefore, immediate restoration is required by applying a comprehensive and systematic reforestation method. Natural forest recovery, particularly in forestland used for bare opencast mining, requires several hundred years and consists of the initial, middle, and climax stages [3]. Pioneering and light-requiring species, such as leguminous trees, grasses, and shrubs, are established first [4] in the initial stage of forest succession, followed by gap-opportunistic species (Meliaceae, Dipterocarpaceae, and Flindersia spp.) in the middle stage, and finally shade-tolerant species in the mature or climax stage [5]. The preparation of seedlings of native tree species [6] and the selection of fast-growing leguminous species [7] with improved nitrogen (N), phosphorus (P), and potassium (K) uptake and biomass production are vital for the initial stage of reforestation.Mallotus paniculatus (Euphorbiaceae) is distributed throughout the Malesian region, including Indonesia [8]. As an evergreen timber tree [9], this plant is an important pioneer species in Kalimantan, Indonesia, because it contributes to the aboveground biomass in secondary forests [10].Albizia saman (Fabaceae) is native to Northern South America and has become naturalized in the tropics [11]. A. saman is usually planted for agroforestry [11] and timber purposes [12]. As a moderately fast growing species [11], A. saman has a high survival rate [13] and grows in a wide range of climatic conditions [11], making it potentially useful for reforestation.The rapid production of M. paniculatus and A. saman seedlings in nurseries is important for successful reforestation. However, the initial growth of A. saman is slow [11]. Furthermore, poor nutrient uptake due to the low fertility and the high acidity of the tropical soil in Indonesia has made it difficult to improve the seedling growth.Manure or green compost is a substrate usually used together with the amendment of other organic nutrients or fertilizers in nurseries to meet the nutritional requirements for plant growth. As fertilizer application is costly, it is important to adopt an inexpensive and environmentally friendly method to meet the nutritional requirements for plant growth improvement. As for the plants grown in pots in nursery, the possible contact between plants with soil microorganisms in the ground including AM fungi is very low. The application of symbiotic soil microorganisms that may facilitate nutrient transfer from substrate to plant may enhance nutrient uptake efficiency. It is well documented that arbuscular mycorrhizal (AM) fungi can improve seedling growth, tree height, and plant yield [14] by increasing nutrients [15]. Considering these abilities, AM fungi can assist plant nutrient uptake and therefore promote seedling growth under nursery conditions.AM colonization was observed in M. paniculatus [16] and A. saman [17]. Inoculation with AM fungi increased the height and shoot dry weight of Macaranga denticulata (Euphorbiaceae) [18]. Inoculation with AM fungi also changed the chlorophyll, carotenoid, sugar, and protein contents of A. saman in nurseries in India [19]. However, they did not measure the AM fungi colonization and its effect on nutrient uptake and growth. Therefore, to the best of our knowledge there is no information about the effect of AM fungal colonization on the N and P uptake and growth of M. paniculatus and A. saman. We hypothesize that the AM fungal inoculation of M. paniculatus and A. saman leads to AM colonization, thereby improving N and P uptake and growth of these plant species.In order to enhance the growth of M. paniculatus and A. saman in nurseries, two AM fungal species, Gigaspora decipiens Hall & Abbott and Glomus clarum Nicholson & Schenck, were inoculated. Those two AM fungal species were used because they are indigenous to Kalimantan and they have the ability to improve nutrient uptake and growth of tropical peat-swamp plants [20]. The objective of this research was to determine whether inoculation with the two native AM fungal species could improve N and P uptake and growth of native M. paniculatus and A. saman under nursery conditions in Binungan, Tanjung Redeb, Berau Regency, East Kalimantan, Indonesia.2. Materials and Methods2.1. Soil PreparationCompost is one of the most common substrates used to grow seedling in pot in nursery in Indonesia. Compost is used to reduce chemical fertilizer application and to prepare good healthy seedling before transplanting it to the field which is usually covered by compost. Compost was collected from a local area in Binungan (N02° 02′, E117° 27′), Tanjung Redeb, Berau Regency, East Kalimantan, Indonesia. Examination of the compost substrate used in the nursery revealed no spores of AM fungi, indicating that the compost substrate possibly did not support spontaneous AM colonization. To distinguish other soil fungi or soil microorganisms, the compost was sterilized in a drum by heating over wood fire for 3 hours and further stored at room temperature. The compost chemical characteristics before sterilization showed that the available P [21] was 622 mg P2O5 kg−1, total N concentration was 26.5 g kg−1, and C concentration was 372.1 g kg−1 (Sumigraph N-C 220 F). The C : N ratio was 14.04, pH H2O was 5.25, and pH KCl was 4.82.2.2. Inoculum Preparation and AM Fungi InoculationGlomus clarum Nicholson & Schenck and Gigaspora decipiens Hall & Abbott were isolated from peat soil in Kalampangan (S2° 13′, E113° 56′), Palangkaraya, Central Kalimantan, Indonesia [20]. Pueraria javanica Benth was cultivated in zeolite to propagate those two AM fungal species under greenhouse conditions for 90 days. The roots, zeolite, and spores were used as the AM fungal inoculum. Inoculation with AM fungi was accomplished by mixing 20 g of the inoculum with 800 g of the sterilized compost in a polyethylene bag (10 cm diameter × 15 cm height). Noninoculated compost was prepared by adding more 20-gram sterilized compost into 800-gram sterilized compost as control.2.3. Seed GerminationSeeds of M. paniculatus (Lamk.) Müll. Arg. were collected from natural forests in Binungan. Seeds of A. saman (Jacq.) Merr. were purchased from a local seed company, Bogor, West Java, Indonesia. The A. saman seeds were soaked in water at 80°C for 1-2 minutes [11]. No scarification was applied to the seeds of M. paniculatus. Approximately five to seven seeds were sown in the inoculated and noninoculated composts at a depth of 1 cm on 29 September 2011. One seedling per polyethylene bag was grown after germination. Due to the large size of the A. saman seedlings, the seedlings were transferred to larger polyethylene bag (15 cm diameter × 20 cm height) four months after sowing on 30 January 2012 by using the same sterilized compost. No fertilizer was applied. The experimental design used was completely randomized design (CRD) where the seedlings in the polyethylene bag were arranged randomly in the nursery. Tap water was applied once every two days. The seedlings were grown under 50% shade from 29 September 2011 to 8 March 2012 in the nursery in Binungan. This plant growth period was determined to get appropriate size of seedling for transplanting to the field.2.4. Growth Parameters M. paniculatus and A. saman seedlings were subjected to three treatments: (1) control, (2) inoculation with G. clarum, and (3) inoculation with G. decipiens. Each treatment had 20 replications and shoot height and leaf number were measured two, three, and four months after sowing. Six months after sowing, the seedlings were sampled and five replications were harvested for each treatment. The 15 remaining seedlings were left for transplanting to field. Shoots and roots were separately harvested. Shoots were oven dried at 70°C for 72 hours and weighed. Ground shoots were digested with HNO3-HClO4-H2SO4 solution. P concentration in the solution with the digested ground shoots was determined colorimetrically with the vanadomolybdate-yellow assay [22] using a spectrophotometer at 880 nm absorbance (Hitachi, U-2900). Shoot N concentration was determined using a Sumigraph N-C 220 F. Shoot P and N contents were calculated by multiplying the shoot nutrient concentration and the shoot dry weight.2.5. Assessment of AM ColonizationAM colonization was observed by harvesting the roots of M. paniculatus and A. saman. The roots were cleared in KOH (100 g L−1) at 80°C for 15 minutes, acidified ..
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http://www.scilit.net/article/10.1155/2014/898494
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