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PART II
Peatland is characterized by the accumulation of large amounts of partially decomposed plant material, low pH, high groundwater level, and low nutrient content. Because of these characteristics, peatland is unfavorable for the use as cultivated fields. Nevertheless, to supply foods balanced with the increasing population, peatland occupying 30 million ha in Southeast Asia (Radjagukguk 1997) is a potential ground for crop production. As the high groundwater level interferes with the supply of oxygen into soil, drainage is generally required to facilitate respiration of plant roots in peatland reclaimed for agricultural use. However, peat materials may be decomposed and subsided quickly if groundwater level is lowered (Blodau 2002), which would accelerate nutrient loss from peatland and further lower plant productivity (Laiho et al. 1999). Sago palm (Metroxylon sagu Rottb.) is worthy of attention as a rare crop that can grow on tropical peat soil without drainage of groundwater and yields a great amount of starch, 164–180 kg per plant on a dry weight basis (Yamamoto et al. 2003).
However, Yamaguchi et al. (1994) and Jong and Flach (1995) reported that the starch content in sago palm was larger at lower groundwater level than at higher groundwater level. Yamaguchi et al. (1994) also observed much smaller contents of micronutrients including Cu and Zn in sago palm grown in deep peat soils compared with those grown in alluvial soils. Nutrients released from peat soil may be insufficient to satisfy the growth of sago palm especially in the second and following generations. Therefore, prefer control of groundwater table and fertilizer application are required to maintain the high starch productivity, which have not been developed. Simultaneously the impact of sago palm cultivation on the environment, such as acceleration of peat decomposition, change in soil fertility, and loadings of greenhouse gasses and water-soluble nutritional/toxic elements to the atmosphere and aquatic environments, respectively, should be minimized toward the sustainable use for agriculture. There are few data (Funakawa et al. 1996; Kawahigashi et al. 2003) available to evaluate the effects of sago palm cultivation on elemental cycles in peatland ecosystem. The reclamation of peatland has been observed to have significant changes in the rate and chemistry of water flow (Burba et al. 2001; Lu and Jaffe 2001; Vasander et al. 2003). For example, the change in the concentration of dissolved organic matter (DOM), such as fulvic acids, induces the changes in the mobility, toxicity (McCartney et al. 2003), and solubility in brackish and seawater (Matsunaga et al. 1984) of metallic elements through the formation of complexes (Ku¨chler et al. 1994; Viers et al. 1997; Kalbitz and Wennrich 1998), and subsequently affect the population and community structure of aquatic biota (Roy and Campbell 1997; Matsunaga et al. 1998; O¨ ztu¨rk et al. 2002). In the present study, we examined the effects of sago palm cultivation on the chemical properties of soil and water in an Indonesian peatland, with focusing on metallic elements.
However, Yamaguchi et al. (1994) and Jong and Flach (1995) reported that the starch content in sago palm was larger at lower groundwater level than at higher groundwater level. Yamaguchi et al. (1994) also observed much smaller contents of micronutrients including Cu and Zn in sago palm grown in deep peat soils compared with those grown in alluvial soils. Nutrients released from peat soil may be insufficient to satisfy the growth of sago palm especially in the second and following generations. Therefore, prefer control of groundwater table and fertilizer application are required to maintain the high starch productivity, which have not been developed. Simultaneously the impact of sago palm cultivation on the environment, such as acceleration of peat decomposition, change in soil fertility, and loadings of greenhouse gasses and water-soluble nutritional/toxic elements to the atmosphere and aquatic environments, respectively, should be minimized toward the sustainable use for agriculture. There are few data (Funakawa et al. 1996; Kawahigashi et al. 2003) available to evaluate the effects of sago palm cultivation on elemental cycles in peatland ecosystem. The reclamation of peatland has been observed to have significant changes in the rate and chemistry of water flow (Burba et al. 2001; Lu and Jaffe 2001; Vasander et al. 2003). For example, the change in the concentration of dissolved organic matter (DOM), such as fulvic acids, induces the changes in the mobility, toxicity (McCartney et al. 2003), and solubility in brackish and seawater (Matsunaga et al. 1984) of metallic elements through the formation of complexes (Ku¨chler et al. 1994; Viers et al. 1997; Kalbitz and Wennrich 1998), and subsequently affect the population and community structure of aquatic biota (Roy and Campbell 1997; Matsunaga et al. 1998; O¨ ztu¨rk et al. 2002). In the present study, we examined the effects of sago palm cultivation on the chemical properties of soil and water in an Indonesian peatland, with focusing on metallic elements.
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Temporal variations in the concentrations of elements in drainage (canal) system were evaluated by combining the data collected from sago palm cultivation blocks with various plant ages during a 2-year period. Changes in the chemical properties of soils were estimated using two data sets obtained from soils at different distances from sago palm plant and soils at different depths. The accumulation of elements from fertilizer or the consumption of elements by active plant absorption may result in the increase/decrease in their contents horizontally and/or vertically. Chemical
properties of canal water and soil were also compared between sago palm cultivation blocks and their adjacent secondary forests. The relation of DOM to metallic elements and the chemical properties of groundwater below sago palm were also examined to discuss the behavior of fertilized and unfertilized elements as affected by the sago palm cultivation.
properties of canal water and soil were also compared between sago palm cultivation blocks and their adjacent secondary forests. The relation of DOM to metallic elements and the chemical properties of groundwater below sago palm were also examined to discuss the behavior of fertilized and unfertilized elements as affected by the sago palm cultivation.
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