S:Odonata larvae were sampled from 16 tributaries of Kerian River in the Kerian River Basin (KRB) using a kick sampling technique from September 1998 to May 1999 encompassing both rainy and dry seasons. The distributi...S:Odonata larvae were sampled from 16 tributaries of Kerian River in the Kerian River Basin (KRB) using a kick sampling technique from September 1998 to May 1999 encompassing both rainy and dry seasons. The distribution of odonate genera was significantly different (F 15,16 =3.99) among rivers in both seasons (F 15,16 =4.70) at P=0.05. However, no seasonal influence was detected. Protoneuridae and Libellulidae were the most dominant families in this basin. Other families Gomphidae, Coenagrionidae, Macromiidae, Chlorocyphidae and Calopterygidae, were common but Aeshnidae and Eupheidae were rare. Several common species, Prodasineura autumnalis, Brachythemis contaminata, Macromia gerstaeckeri, Paragomphus, Orthetrum brunneum, Rhinocypha quadrimaculata and Copera marginipes were identified. The calculated values of biological indices (H’, D, E, R 1 and R 2) showed that the dragonfly fauna in this river basin was slightly poor. Varied physico-chemical parameters of the river possibly as a result of human activities in surrounding areas were found to influence the distribution of the dragonfly larvae in the KRB. This study showed that the KRB provided favorable habitats for Protoneuridae and 1Libellulidae. Two most dominant species Prodasineura autumnalis and Brachythemis contaminata were obviously favoured slightly acidic water of the Kerian river tributaries.展开更多
Redox potential in the well developed tropical peat swamp in Brunei was studied for a year.Generally the redox potential measurements showed a large variation,ranging from-234 mV to 727 mV.The expected rise in redox v...Redox potential in the well developed tropical peat swamp in Brunei was studied for a year.Generally the redox potential measurements showed a large variation,ranging from-234 mV to 727 mV.The expected rise in redox values did not take place following the drop of water table during the dry months of June to September.The redox value at 100 cm depth indicated that the soil remained reduced throughout the year in spite of the lowering of water table below 150 cm in all sites during dry period.Similarly the redox values did not decrease rapidly following flooding when the water table rose to the surface.This phenomenon could be attributed to the topography of the peat dome which facilitated the fast lateral movement of water and thus promoted oxygen supply down the peat profile,though not great enough to reach the 100 cm depth.The rapid lateral flow of water in the outer Alan batu site facilitated aeration,but in the inner sites remained which was reduced because of the slower water movement.The slower initiation of the reducing condition was likely due to the presence of nitrate which has accumulated as a result of ammonium oxidation during the relatively long aerobic period.Differences in the distribution of redox potential with depth are possibly explained by the different permeability of peat affecting flow patterns and residence time of water.The nature and compactibility of the peat might have slowed the diffusion rates of O2 into the lower layer.Though the bulk density of the peat was low,the composition of the peat might influence the peat permeability and hydraulic conductivity.The tree trunks are not decomposed or large branches must have lowered permeability compared to the other peat material.展开更多
文摘S:Odonata larvae were sampled from 16 tributaries of Kerian River in the Kerian River Basin (KRB) using a kick sampling technique from September 1998 to May 1999 encompassing both rainy and dry seasons. The distribution of odonate genera was significantly different (F 15,16 =3.99) among rivers in both seasons (F 15,16 =4.70) at P=0.05. However, no seasonal influence was detected. Protoneuridae and Libellulidae were the most dominant families in this basin. Other families Gomphidae, Coenagrionidae, Macromiidae, Chlorocyphidae and Calopterygidae, were common but Aeshnidae and Eupheidae were rare. Several common species, Prodasineura autumnalis, Brachythemis contaminata, Macromia gerstaeckeri, Paragomphus, Orthetrum brunneum, Rhinocypha quadrimaculata and Copera marginipes were identified. The calculated values of biological indices (H’, D, E, R 1 and R 2) showed that the dragonfly fauna in this river basin was slightly poor. Varied physico-chemical parameters of the river possibly as a result of human activities in surrounding areas were found to influence the distribution of the dragonfly larvae in the KRB. This study showed that the KRB provided favorable habitats for Protoneuridae and 1Libellulidae. Two most dominant species Prodasineura autumnalis and Brachythemis contaminata were obviously favoured slightly acidic water of the Kerian river tributaries.
文摘Redox potential in the well developed tropical peat swamp in Brunei was studied for a year.Generally the redox potential measurements showed a large variation,ranging from-234 mV to 727 mV.The expected rise in redox values did not take place following the drop of water table during the dry months of June to September.The redox value at 100 cm depth indicated that the soil remained reduced throughout the year in spite of the lowering of water table below 150 cm in all sites during dry period.Similarly the redox values did not decrease rapidly following flooding when the water table rose to the surface.This phenomenon could be attributed to the topography of the peat dome which facilitated the fast lateral movement of water and thus promoted oxygen supply down the peat profile,though not great enough to reach the 100 cm depth.The rapid lateral flow of water in the outer Alan batu site facilitated aeration,but in the inner sites remained which was reduced because of the slower water movement.The slower initiation of the reducing condition was likely due to the presence of nitrate which has accumulated as a result of ammonium oxidation during the relatively long aerobic period.Differences in the distribution of redox potential with depth are possibly explained by the different permeability of peat affecting flow patterns and residence time of water.The nature and compactibility of the peat might have slowed the diffusion rates of O2 into the lower layer.Though the bulk density of the peat was low,the composition of the peat might influence the peat permeability and hydraulic conductivity.The tree trunks are not decomposed or large branches must have lowered permeability compared to the other peat material.
