ศักยภาพการกักเก็บคาร์บอน ธาตุอาหารและน้ำในป่าปลูกไม้สักและสนสามใบผสมไผ่ บริเวณดอยตุง อำเภอแม่ฟ้าหลวง จังหวัดเชียงราย

Abstract

Potentials of carbon, nutrient and water storages in 29-year-old teak and three needle pine plantations mixed with bamboo at Doi Tung area, Mae Fah Luang district, Chiang Rai province, were studied for the purpose of assessing ecological and environmental roles of forest plantations. Twelve sampling plots, each of size 40x40 m, were arranged randomly from an altitudinal range of 450 m to 950 m. Six plots were used for the teak plantation with three plots each in teak with bamboo and teak without bamboo stands. Pine plantations had 950-970 m altitude and six plots were also used, three plots each in pine with bamboo and pine without bamboo stands. Plant data were obtained by measuring stem girths (1.3 m above ground and heights of all trees with height over 1.5 m). Three plots were selected for soil study, three pedons (each of size 1.5x1.5x2 m) for each of teak and pine plantation with bamboo. Soil sampling with three replications were taken along the depth with composite samples for analyzing physicochemical properties. Soil characteristics was described for soil horizon development, depth of each layer, soil color, soil texture, plant roots, etc. 1. Plant communities and species diversity A. Teak plantation without bamboo : A total of 63 species in 50 genera and 30 families was found with index of species diversity (Shannon-Wiener Index: SWI) as 4.26. Average teak density, stem girth and tree height were measured as 87.33 tree/rai, 67.59 cm and 21.09 m, respectively. As for teak plantation with bamboo, 54 species in 43 genera and 23 families were occurred with SWI as 4.05. The bamboo included three species of Pai Bong (Bambusa nutans Wall.), Pai Sang (Dendrocalamus membranaceus Munro) and Pai Rai (Gigantochloa albociliata (Munro) Kurz.). Teak density, stem girth and tree height were measured as 50.33 tree/rai, 75.08 cm and 19.79 m, respectively. B. Pine plantation without bamboo : Totally 76 species in 62 genera and 34 families were observed with SWI of 4.90. Pine density, stem girth and tree height were measured as the following order: 33.33 tree/rai, 120.96 cm and 37.16 m. In pine plantation with bamboo, 80 species in 43 genera and 35 families were found with SWI of 3.62. The bamboo included four species of Pai Bong (Bambusa nutans Wall.), Pai Sang (Dendrocalamus membranaceus Munro), Pai Rai (Gigantochloa albociliata (Munro) Kurz.) and Pai Hok (Dendrocalamus hamiltonii Nees & Arn. ex Munro). Teak density, stem girth and tree height were determined as 26.33 tree/rai, 113.17 cm and 33.09 m, respectively. 2. Carbon, nutrient and water storages A. Teak plantation mixed with bamboo : Plant biomass was calculated at 53,746.78 kg/rai, and could store amounts of carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) as the following order: 26,570.19, 267.29, 31.44, 132.43, 502.35 and 88.89 kg/rai. The water stored in the biomass was estimated at 94.20 m3/rai. Within 2 m soil depth, amounts of total C, total N and available forms of P, K, Ca and Mg were calculated at 49,412.78, 4,441.07, 5.74, 435.04, 582.43 and 456.93 kg/rai, respectively, whereas the maximum water holding capacity (MWHC) was 1,584.07 m3/rai. The total amounts of carbon and macronutrients in the plantation ecosystem (plant and soil) were estimated at 75,982.97, 4,708.36, 37.18, 567.47, 1,084.78 and 545.82 kg/rai, while the maximum water storage was 1,678.27 m3/rai. B. Pine plantation mixed with bamboo : Plant biomass was calculated at 41,064.35 kg/rai, and it could store amounts of carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) at the following order: 20,263.46, 193.26, 21.56, 95.83, 368.56 and 56.99 kg/rai. The biomass water was 53.23 m3/rai. Within 2 m soil depth, amounts of total C, total N and available forms of P, K, Ca and Mg were calculated at 52,984.69, 4,844.15, 8.14, 392.47, 35.09 and 16.24 kg/rai, respectively, whereas the MWHC was 1,471.17 m3/rai. The total amounts of carbon and macronutrients in the plantation ecosystem (plant and soil) were estimated at 73,248.14, 5,037.41, 29.70, 488.30, 403.65 and 73.23 kg/rai, while the maximum water storage was 1,524.40 m3/rai. 3. Soil characteristics A. Teak plantations : Soil depth was also 2 m and classified into Order Ultisols with a profile of A-BA-Bt. Bulk densities varied from moderately low to high. Soil textures varied between fine-textured and moderately fine-textured soils including clay, sandy clay, clay loam and sandy clay loam. Surface soil was very strongly acid and moderately acid to slightly acid in subsoils. Contents of organic matter, carbon and nitrogen were high in surface soil and lower in subsoils. Available phosphorus was almost low levels. Extractable potassium was high in surface soil and medium to high in subsoils. Extractable calcium was low throughout the profiles whereas magnesium was high in surface soil and lower in subsoils. B. Pine plantation : Soil depth was 2 m and classified into Order Ultisols with the profile of A-AB-Bt. Bulk densities varied from moderately low to moderately high. Soil textures was fine-textured soils including clay and sandy clay. There were very strongly acid in surface soil and moderately acid to slightly acid in subsoils. Organic matter, carbon and nitrogen were the high contents in surface soils and lower in subsoils. Available phosphorus was low levels. Extractable potassium was high in surface soil and medium to high in subsoils while calcium and magnesium were low throughout the profiles.