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Abstract

The study on influences of bamboo on storages of carbon, nutrients and water in agroforest ecosystem of planted bamboo-dry dipterocarp forest was carried out in the Huai Hong Khrai Royal Development Study Center, Doi Sakaet district, Chiang Mai province. Three kinds of bamboo species including Pai Sang (Bambusa menbranaceus), Pai Bong (Bambusa nutans) and Pai Ruak (Thrysostachys siamensis) were planted in the forest. Plant community had been investigated using 10, 40 x 40 m2 sampling plots. In each plot, stem girths at 1.3 m above ground, heights and crown widths of all tree species of heights >1.5 m were measured. As for bamboo species, the clump girth of bamboo bush was measured. Three plots were selected for soil study, and one soil pit was made in each plot with 1.5 meters in width and the depth to parent rock. Soil profile development was examined, and soil samples were collected along the soil depth. The soil samples were taken to a laboratory for analysis of physical and chemical properties. Soil type was later determined. Using ten sampling plots, the plant species richness varied between 12-34 trees/plot, and a total of 59 species (53 genera and 27 families) was found. The highest number of tree species in the forest was in the family of Leguminosae (12 species). Three species in Dipterocarpaceae as an indicator of the dry dipterocarp forest were found: Teng (Shorea obtusa), Rung (Shorea siamensis) and Pluang (Dipterocarpus tuberculatus). Five tree species including S. obtusa, Leucaena leucocephala, Pterocarpus macrocapus, Canarium subulatum and Haldina cordifolia had frequency values of 100%. The average density of tree species in the forest was 2,056 trees ha-1 (329 trees/plot). S. obtusa had the highest relative dominance (38.02% of all species), followed by L. leucocephala, S. siamensis, P. macrocapus and Terminalia alata. S. obtusa had also the highest IVI (20.55%), followed by L. leucocephala, S. siamensis, P. macrocapus and T. alata. The mean species diversity index using Shannon-Wiener Index (SWI) was 3.03. The forest condition index (FCI) varied between 6.50 and 16.22, 10.98 on average. Soils in three pedons of the agroforest ecosystem of planted bamboo-dry dipterocarp forest were the same type. It was very shallow soil, and classified into Order Entisols, Suborder Orthents. Pedon 1 had a profile of A-C-R1-R2-R3 whereas those of Pedon 2 and Pedon 3 were A-AC-C-R1-R2 and A-C-R1- R2- R3, respectively. Soil bulk densities in the three pedons were low throughout soil profiles. Soil textures varied from medium to moderately coarse, loam to sandy clay loam and sandy loam. Soil reaction in top soil was slightly acid while that in subsoil was neutral. Amounts of plant biomass in ten sampling plots varied between 49.12 and 93.95 Mg ha-1 (69.52 Mg ha-1 on average), while the bamboo biomass were 2.74 and 18.18 Mg ha-1 (averaging 7.04 Mg ha-1). The amounts of carbon stored in plant biomass in ten sampling plots varied between 24.27 and 46.42 Mg ha-1 (34.35 Mg ha-1), and it was in a range of 1.26-8.87 Mg ha-1 (averaging 3.43 Mg ha-1) for bamboo species (9.08% of total storage). The mean amounts of nitrogen, phosphorus, potassium, calcium and magnesium stored in plant biomass were 362.37, 42.07, 179.54, 692.85 and 112.13 kg ha-1, respectively. The mean maximum capacity of water storage in agroforest ecosystem of planted bamboo-dry dipterocarp forest was 1,206.75 m3 ha-1. This included the amounts of water stored in plant biomass at 57.53 m3 ha-1 and the amount in soil at 1.149.22 m3 ha-1. The majority amount of water storage in the ecosystem was in soil, 95.23% of the total water storage. Planting of bamboo species in the dry dipterocarp forest resulted in the establishment of an agroforest ecosystem since the farmers can get benefits from utilizing bamboo stems, and bamboo shoots for food. Three species of planted bamboo with the different number of bamboo clumps increased species diversity of the forest. The bamboo species had also increased the amounts of carbon, nutrient and water cycles in the dry dipterocarp forest. These can promote the growths of tree species and increase water retention of the dry dipterocarp forest. It is good for watershed management.