The limitations of vernacular names in an inventory study, Central Kalimantan, Indonesia

One hectare of primary forest in Central Kalimantan was enumerated and all trees 10 cm dbh tagged and identified to species as far as possible. Two informants, regarded as the most knowledgeable on forest trees by the local community, supplied the vernacular names for the trees. The study found that only 12% of vernacular names given by one informant and 22% by the second could be equated consistently to taxa. Of these taxa 77% were given the same vernacular name by both informants and the remaining 23% had an obvious common origin (cognate). Many of these taxa were distinctive or had a use to the informants. The results have important implications for the conversion of vernacular names to scientific names by anyone carrying out inventory work in Kalimantan.     

The carbon content characteristics of tropical peats in Central Kalimantan, Indonesia: Estimating their spatial variability in density

Clarification of carbon content characteristics, on their spatial variability in density, of tropical peatlands is needed for more accurate estimates of the C pools and more detailed C cycle understandings. In this study, the C density characteristics of different peatland types and at various depths within tropical peats in Central Kalimantan were analyzed. The peatland types and the land cover types were classified by land system map and remotely sensed data of multi-temporal AVHRR composites (1-km pixel size), respectively. Differences in the mean values of volumetric C density (CD_V) were found among peatland types owing to the variability in physical consolidation from peat decomposition or nutrient inputs, although no vertical trends of CD_V were found. Using a step-wise regression technique, geographic variables and the categories of peatland type and land cover type were found to explain 54% of the variability of CD_V within tropical peatlands in some conditions.     

Dissolved organic carbon in a humic lake: effects on bacterial production and respiration

Allochthonous matter was the main source of carbon for pelagic bacteria in a humic lake, accounting for almost 90% of the carbon required to support observed bacterial growth. The estimated contribution from zooplankton excretion was of the same magnitude as direct phytoplankton release, both accounting for 5–7% of bacterial demands for dissolved carbon. Bacteria were an important source of carbon both for heterotrophic phytoplankton and for filter feeding zooplankton species, further stressing the role of humus DOC in overall lake productivity. The high contribution of allochthonous DOC implies a stoichiometry of dissolved nutrients with a surplus of C relative to P. The high P cell quota of bacteria suggest that under such conditions they are P-limited and act like net consumers of P. Excess C will be disposed of, and bacterial respiration rate will increase following a transition from carbon-limited bacterial growth towards mineral-nutrient-limited growth. Thus the high community respiration and frequent CO₂-supersaturation in humic lakes may be caused not only by the absolute supply of organic C, but also by the stoichiometry of the dissolved nutrient pool.     

Sedimentation and pedogenesis in a Central Amazonian Black water basin

Sedimentation rates were estimated in a Central Amazonian Black-water inundation forest. Sediment deposition on the forest ground, remote from the river bed, during an annual flood period, is of the order of 1 to 10 tons per hectare, depending on water depth and duration of flooding. The sediments consisted of fine organic matter, kaolinite, quartz sands and biogenic particles of silica. Their genesis and deposition depend on the interplay between pedogenic, limnological and biological processes. Sediments derive primarily from the materials leached from the soils. Clay soils are the main source of dissolved silica, and the sandy soils are the main sources of organic coumpounds and mineral particles. The physical sedimentation of particles as quartz sand grains only occurs in the upper reaches of the studied river. In the flood plain, the sedimentation is due to the coagulation and deposition of combined mineral particles and humic substances, and to the biological precipitation of the silica leached from the soil by sponges.     

Dissolved organic carbon and fluorescence in Lake Hovsgol: factors reducing humic content of the lake water

 Lake Hovsgol is a large tectonic lake located in northern Mongolia, which has extremely transparent lake water. In our survey, the dissolved organic carbon of the lake water was 80–100 μM-C, and the fluorescence intensity in an excitation and emission matrix was very low. The brown color and high content of humic substances in river water flowing from a watershed consisting of grassland and forests rapidly declined in the coastal area of the lake. The decrease in humic content may be due not only to dilution by the lake water but also to flocculation and photobleaching. Among tectonic lakes in Asia, Lake Hovsgol would appear to have unique biological and hydrological features that reduce humic content and help to maintain water transparency. Received: June 25, 2002 / Accepted: January 10, 2003 Acknowledgments The authors acknowledge helpful discussion with Dr. J. Urabe. We thank Dr. T. Galbaatar, Mongolian Academy of Science, Mongolia, for his arrangements on the expeditions in 1999. We are also indebted to Mr. D. Hadbaatar, B. Ganbat, and the cruise staff of the R/V Suchbaatar for their assistance in the course of the study. This study was supported by Grant-in-Aid No. 09041159 and 13575034 for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology of Japan. Correspondence to:K. Hayakawa     

Group composition,home range,and diet of the maroon leaf monkey (Presbytis rubicunda) at Tanjung Puting Reserve,Central Kalimantan,Indonesia

Maroon leaf monkeys (Presbytis rubicunda) were studied at the Orangutan Research Conservation Project study area at the Tanjung Puting Reserve in Central Indonesian Borneo for approximately 15 months in 1974, 1975, and 1977. Over 250 observation hr involving 300 encounters with the monkeys were logged. Troop size ranged from three to eight individuals in the nine troops surveyed with only one adult male being present in each troop. Home range size varied from 0.33 km² to 0.99 km² and correlated with troop size. Forty-six different food types were observed eaten by the maroon leaf monkeys; of these foods, 52% consisted of fruits, 36% of leaves, and 12% of flowers.     

Effect of sulfuric acid discharge on river water chemistry in peat swamp forests in central Kalimantan,Indonesia

To estimate the range of area that is affected by sulfuric acid pollution after pyrite oxidation, the surface water chemistry of two rivers in peat swamp forests in central Kalimantan, Indonesia, was surveyed at 1.0- to 3.0-km intervals in September 2003 and 2004 (dry season) and March 2004 and 2005 (rainy season). Water discharged from canals into the main stream of the Sebangau River and the Kahayan River showed lower pH compared to the mainstream water of the rivers, implying sulfuric acid loading from the canal to the main stream of the rivers. The ratio of concentrations of sulfate ion/chloride ion, which was used as a parameter for estimating the contribution of pyritic sulfate to river water chemistry, showed that sulfuric acid loading from pyrite oxidation occurred from the river mouth up to 150 km upstream in both rivers. Water of the main stream of the rivers as well as water discharged from artificial canals into the main stream in the rainy season showed much higher acidity and a higher ratio of sulfate ion/chloride ion than that in the dry season. This result implies that the discharge of pyritic sulfate from peat swamp forests to the limnological system is much higher in the rainy (high water table) season than the dry (low water table) season. Water in the canal in the rainy season was found to be highly acidic (pH = 2.0–3.0). Pyrite oxidation after peatland development causes not only acidification of soil but also acidification of the limnological ecosystem.     

Examination of the potential relationship between droughts, sulphate and dissolved organic carbon at a wetland-draining stream

Rising dissolved organic carbon (DOC) concentrations observed at a number of sites in the northern hemisphere over recent decades are the subject of much debate, and recent reports suggest a link between DOC patterns in surface waters and changes in sulphate (SO₄) related to droughts or deposition. In order to investigate the potential influence of changes in SO₄ concentration on DOC patterns in south‐central Ontario, we used long‐term (1980–2001) stream monitoring data from a wetland‐dominated catchment (Plastic Lake‐1 subcatchment, PC1) that has been the focus of intensive investigations of both SO₄ and DOC dynamics. Annual average volume‐weighted DOC concentration increased significantly between 1980 and 2001, whereas SO₄ concentration declined, but the decrease was not significant due to large increases in SO₄ that occurred during drought years. There was no relationship between SO₄ and DOC in annual data series; however, seasonal analyses indicated significant negative correlations between SO₄ and DOC concentrations in spring (March–April–May), summer (June–July–August) and fall (September–October–November). In spring, DOC concentration was negatively correlated with flow whereas SO₄ concentrations increased with flow, and their opposing relationships with discharge explain the negative correlation between SO₄ and DOC in this season. In summer and fall, low SO₄ concentrations occur during periods of low flow as a result of microbial SO₄ reduction, whereas correspondingly high DOC concentrations in the summer and fall can be attributed to optimal conditions (i.e. stagnant flow, warm temperatures) for DOC production in the wetland. Increases in SO₄ (and acidity) following droughts were not associated with declines in DOC; instead the primary impact of droughts on DOC was to limit DOC export due to diminished stream flow. Rather than an acidification effect, we suggest that negative relationships between SO₄ and DOC were either directly (spring) or indirectly (summer/fall) caused by underlying relationships with hydrology.     

The plankton community of Lake Matano: factors regulating plankton composition and relative abundance in an ancient,tropical lake of Indonesia

Recent evidence reveals that food webs within the Malili Lakes, Sulawesi, Indonesia, support community assemblages that are made up primarily of endemic species. It has been suggested that many of the species radiations, as well as the paucity of cosmopolitan species in the lakes, are related to resource limitation. In order to substantiate the possibility that resource limitation is playing such an important role, a study of the phytoplankton and zooplankton communities of Lake Matano was implemented between 2000 and 2004. We determined species diversity, relative abundances, size ranges, and total biomass for the phytoplankton and zooplankton, including the distribution of ovigerous individuals throughout the epilimnion of Lake Matano in three field seasons. The phytoplankton community exhibited very low biomass (<15 μg l^?1) and species richness was depressed. The zooplankton assemblage was also limited in biomass (2.5 mg l^?1) and consisted only of three taxa including the endemic calanoid Eodiaptomus wolterecki var. matanensis, the endemic cyclopoid, Tropocyclops matanensis and the rotifer Horaella brehmi. Zooplankton were very small (<600 μm body length), and spatial habitat partitioning was observed, with Tropocylops being confined to below 80 m, while rotifer and calanoid species were consistently observed above 80 m. Less than 0.1% of the calanoid copepods in each year were egg-bearing, suggesting very low population turnover rates. It was concluded that chemical factors as opposed to physical or biological processes were regulating the observed very low standing crops of phytoplankton which in turn supports a very minimal zooplankton community restricted in both species composition and abundance. As chemical factors are a function of the catchment basin of Lake Matano, it is predicted that resource limitation has long played an important role in shaping the unique endemic assemblages currently observed in the food web of the lake.     

Dissolved organic carbon affects soil microbial activity and nitrogen dynamics in a Mexican tropical deciduous forest

Seasonal variation of dissolved organic C (DOC) and its effects on microbial activity and N dynamics were studied during two consecutive years in soils with different organic C concentrations (hilltop and hillslope) in a tropical deciduous forest of Mexico. We found that DOC concentrations were higher at the hilltop than at the hillslope soils, and in both soils generally decreased from the dry to the rainy season during the two study years. Microbial biomass and potential C mineralization rates, as well as dissolved organic N (DON) and NH₄⁺ concentrations and net N immobilization were higher in soils with higher DOC than in soils with lower DOC. In contrast, net N immobilization and NH₄⁺ concentration were depleted in the soil with lowest DOC, whereas NO₃⁻ concentrations and net nitrification increased. Negative correlations between net nitrification and DOC concentration suggested that NH₄⁺ was transformed to NO₃⁻ by nitrifiers when the C availability was depleted. Taken together, our results suggest that available C appears to control soil microbial activity and N dynamics, and that microbial N immobilization is facilitated by active heterotrophic microorganisms stimulated by high C availability. Soil autotrophic nitrification is magnified by decreases in C availability for heterotrophic microbial activity. This study provides an experimental data set that supports the conceptual model to show and highlight that microbial dynamics and N transformations could be functionally coupled with DOC availability in the tropical deciduous forest soils. Responsible Editor: Chris Neill     

Contribution of plant photosynthates to dissolved organic carbon in a flooded rice soil

Dissolved organic C (DOC) plays important roles in nutrient cycling and methane production in flooded rice ecosystem. The microcosm experiment was carried out to measure directly the contribution of photosynthates to DOC by using a ¹³C pulse-chase labeling technique. DOC was operationally divided into water-extractable organic C (WEOC) and salt-extractable organic C (SEOC) by successive extraction firstly with deionized water and then with 0.25 M K₂SO₄. Total WEOC increased with plant growth, whereas SEOC concentration did not change significantly over the growing season. About 0.037–0.36% (mean 0.16%) of the assimilated ¹³C was incorporated into WEOC immediately after ¹³CO₂ assimilation (Day 0), but only 0–0.025% (mean 0.01%) was incorporated into SEOC. At the end of the growing season, the ¹³C amounts of WEOC substantially decreased, while those of SEOC slightly increased. The estimated net plant C contribution was 21 mg C plant^–1 to WEOC and 6 mg C plant^–1 to SEOC, corresponding to 33.8% of total WEOC and 20.2% of total SEOC at the end of the growing season, respectively. The results suggest that the incorporation and decomposition of the photosynthesized C occurred rapidly in rice soil which significantly affected the WEOC dynamics, but SEOC appeared to be in equilibrium with the native soil organic matter, receiving less effect from the plant growth.     

Dissolved Nitrogen, Phosphorus, and Sulfur forms in the Ecosystem Fluxes of a Montane Forest in Ecuador

The N, P, and S cycles in pristine forests are assumed to differ from those of anthropogenically impacted areas, but there are only a few studies to support this. Our objective was therefore to assess the controls of N, P, and S release, immobilization, and transport in a remote tropical montane forest. The study forest is located on steep slopes of the northern Andes in Ecuador. We determined the concentrations of NO₃-N, NH₄-N, dissolved organic N (DON), PO₄-P, dissolved organic P (DOP), SO₄-S, dissolved organic S (DOS), and dissolved organic C (DOC) in rainfall, throughfall, stemflow, lateral flow (in the organic layer), litter leachate, mineral soil solution, and stream water of three 8–13 ha catchments (1900–2200 m a.s.l.). The organic forms of N, P, and S contributed, on average, 55, 66, and 63% to the total N, P, and S concentrations in all ecosystem fluxes, respectively. The organic layer was the largest source of all N, P, and S species except for inorganic P and S. Most PO₄ was released in the canopy by leaching and most SO₄ in the mineral soil by weathering. The mineral soil was a sink for all studied compounds except for SO₄. Consequently, concentrations of dissolved inorganic and organic N and P were as low in stream water (TDN: 0.34–0.39 mg N l⁻¹, P not detectable) as in rainfall (TDN: 0.39–0.48 mg N l⁻¹, P not detectable), whereas total S concentrations were elevated (stream water: 0.04–0.15, rainfall: 0.01–0.07 mg S l⁻¹). Dissolved N, P, and S forms were positively correlated with pH at the scale of soil peda except inorganic S. Soil drying and rewetting promoted the release of dissolved inorganic N. High discharge levels following heavy rainstorms were associated with increased DOC, DON, NO₃-N and partly also NH₄-N concentrations in stream water. Nitrate-N concentrations in the stream water were positively correlated with stream discharge during the wetter period of the year. Our results demonstrate that the sources and sinks of N, P, and S were element-specific. More than half of the cycling N, P, and S was organic. Soil pH and moisture were important controls of N, P, and S solubility at the scale of individual soil peda whereas the flow regime influenced the export with stream water.     

Density and population estimate of gibbons (Hylobates albibarbis) in the Sabangau catchment, Central Kalimantan, Indonesia

We demonstrate that although auditory sampling is a useful tool, this method alone will not provide a truly accurate indication of population size, density and distribution of gibbons in an area. If auditory sampling alone is employed, we show that data collection must take place over a sufficient period to account for variation in calling patterns across seasons. The population of Hylobates albibarbis in the Sabangau catchment, Central Kalimantan, Indonesia, was surveyed from July to December 2005 using methods established previously. In addition, auditory sampling was complemented by detailed behavioural data on six habituated groups within the study area. Here we compare results from this study to those of a 1-month study conducted in 2004. The total population of the Sabangau catchment is estimated to be about in the tens of thousands, though numbers, distribution and density for the different forest subtypes vary considerably. We propose that future density surveys of gibbons must include data from all forest subtypes where gibbons are found and that extrapolating from one forest subtype is likely to yield inaccurate density and population estimates. We also propose that auditory census be carried out by using at least three listening posts (LP) in order to increase the area sampled and the chances of hearing groups. Our results suggest that the Sabangau catchment contains one of the largest remaining contiguous populations of Bornean agile gibbon.     

The application of a plug-flow reactor to measure the biodegradable dissolved organic carbon (BDOC) in seawater

Most of the ambient dissolved organic carbon (DOC) is refractory to microbial degradation; bacteria can consume a minor but variable part of the DOC pool over periods of hours and days. It is important to increase our knowledge of the dynamics of the biodegradable fraction of DOC (BDOC) to understand the global carbon budget.Several methods for determining BDOC have been developed; however, the problem of most of them is the time (days/weeks) required for the colonization and/or determination.In this paper, we describe the application to seawater of a plug-flow bioreactor to measure BDOC within 3–4 h. The bioreactor was built following Søndergaard and Worm [Søndergaard, M., Worm, J., 2001. Measurement of biodegradable dissolved organic carbon (BDOC) in lake water with a bioreactor. Water Res. 35, 2505-2513.] protocols for the measurement of BDOC in lake water. We analyzed BDOC on samples collected in the Gulf of Trieste during autumn–winter and summer 2003–2004. BDOC concentrations varied from 8 to 24 μM and represented from 10.3% to 25.5% of the total DOC. To evaluate the effectiveness of this method, we compared bioreactor BDOC measurement with data obtained from batch cultures. The results indicate that BDOC in coastal seawater can be measured rapidly and reliably with this bioreactor.     

Observation of anoxic water mass in a tropical reservoir: the Cirata Reservoir in Java,Indonesia

We conducted a transect survey of water quality and bottom sediments in a large tropical reservoir, the Cirata Reservoir, located on the Citarum River, West Java, Indonesia. In the main basin of this reservoir, the surface water contained high concentrations of chlorophyll a, up to 48 μg l⁻¹, and most of the water body was occupied by thick anoxic water. The thickness of the surface oxygenated water was only 5–7 m, whereas that of the anoxic water mass was more than 70 m. The concentrations of phosphate and ammonia were quite high in the anoxic hypolimnion. The reasons for the formation of the huge anoxic water mass include the oligomictic status of circulation, a relatively weak mixing caused by topography, high hypolimnion temperature, and high loads of organic matter. The carbon/nitrogen (C/N) ratios and the carbon stable isotope ratios of sediments indicated that the major source of organic carbon in the sediments was algal production in the reservoir and fish culture activity. The mechanism of eutrophication in the reservoir is also discussed.     

Simulation of water colors in a shallow acidified lake, Lake Onneto, Japan, using colorimetric analysis and bio-optical modeling

Lake Onneto has unusually brilliant water colors, such as blue-green, green, and greenish yellow. We investigated the coloration mechanism in this lake by measuring the radiometric water color and inherent optical properties (IOPs), such as attenuation, absorption, and scattering coefficients of color-producing agents (CPAs) in the lake. The hue of the water body was determined using colorimetric analysis. In addition, the radiometric water color of the lake was simulated using bio-optical modeling. Results showed that the hues of the water body were different between two sampling stations (blue-green and green at 3.1 and 5.5 m of bottom depth, respectively). However, the total suspended solids (TSS) concentrations were almost identical between the two stations (0.47 and 0.42 mg l⁻¹, respectively). In addition, the attenuation and absorption coefficients showed that the CPAs in the water body were only inorganic suspended solids (ISS) more than 0.7 μm in diameter, and specific CPAs, such as dissolved mineral ions and aqueous colloids, were not observed in the lake. Simulation of the radiometric water color showed that the radiation around 600 nm of wavelength (yellow region) steeply increased with decreasing bottom depth, indicating that the water colors of Lake Onneto are strongly governed by the light reflection from yellowish bottom sediments.     

CO2 alters water use,carbon gain,and yield for the dominant species in a natural grassland

Global atmospheric CO₂ is increasing at a rate of 1.5–2 ppm per year and is predicted to double by the end of the next century. Understanding how terrestrial ecosystems will respond in this changing environment is an important goal of current research. Here we present results from a field study of elevated CO₂ in a California annual grassland. Elevated CO₂ led to lower leaf-level stomatal conductance and transpiration (approximately 50%) and higher mid-day leaf water potentials (30–35%) in the most abundant species of the grassland, Avena barbata Brot. Higher CO₂ concentrations also resulted in greater midday photosynthetic rates (70% on average). The effects of CO₂ on stomatal conductance and leaf water potential decreased towards the end of the growing season, when Avena began to show signs of senescence. Water-use efficiency was approximately doubled in elevated CO₂, as estimated by instantaneous gas-exchange measurements and seasonal carbon isotope discrimination. Increases in CO₂ and photosynthesis resulted in more seeds per plant (30%) and taller and heavier plants (27% and 41%, respectively). Elevated CO₂ also reduced seed N concentrations (9%).     

Sulphate,dissolved organic carbon,nutrients and terminal metabolic products in deep pore waters of an intertidal flat

This study addresses deep pore water chemistry in a permeable intertidal sand flat at the NW German coast. Sulphate, dissolved organic carbon (DOC), nutrients, and several terminal metabolic products were studied down to 5 m sediment depth. By extending the depth domain to several meters, insights into the functioning of deep sandy tidal flats were gained. Despite the dynamic sedimentological conditions in the study area, the general depth profiles obtained in the relatively young intertidal flat sediments of some metres depth are comparable to those determined in deep marine surface sediments. Besides diffusion and lithology which control pore water profiles in most marine surface sediments, biogeochemical processes are influenced by advection in the studied permeable intertidal flat sediments. This is supported by the model setup in which advection has to be implemented to reproduce pore water profiles. Water exchange at the sediment surface and in deeper sediment layers converts these permeable intertidal sediments into a “bio-reactor” where organic matter is recycled, and nutrients and DOC are released. At tidal flat margins, a hydraulic gradient is generated, which leads to water flow towards the creekbank. Deep nutrient-rich pore waters escaping at tidal flat margins during low tide presumably form a source of nutrients for the overlying water column in the study area. Significant correlations between the inorganic products of terminal metabolism (NH₄ ⁺ and PO₄ ³⁻) and sulphate depletion suggest sulphate reduction to be the dominant pathway of anaerobic carbon remineralisation. Pore water concentrations of sulphate, ammonium, and phosphate were used to elucidate the composition of organic matter degraded in the sediment. Calculated C:N and C:P ratios were supported by model results.     

Distribution of Epilithic Diatoms in Response to Environmental Conditions in an Urban Tropical Stream, Central Kenya

Use of diatoms in monitoring water quality is well acknowledged in developed countries, but only recently has the assessment started gaining importance in developing countries. Diatoms can be obtained from natural and artificial substrates. Appreciating the differences and similarities of diatom assemblages on both substrates may contribute to a better understanding and standardization particularly during monitoring of water quality. During this study we assessed diatom assemblages, biodiversity and trophic indices in relation to water quality along the Nairobi River. Fifteen sites were sampled in September 2000 during the dry season. Diatoms were collected from natural substrates (stones, pebbles) and artificial substrates (100% acrylic wool). On artificial and natural substrates, a total of 190 and 151 taxa were found, respectively, the majority of these taxa (80%) have cosmopolitan distribution and are also widespread throughout tropical African. Species composition changed downstream, five taxa dominated upper and mid stream sites whereas lower stream sites were dominated by one or two taxa. Species richness, diversity, dominance and evenness were positively correlated with NO₃, O₂ and altitude but decreased markedly downstream with a simultaneous increase in total dissolved solids, alkalinity, chemical oxygen demand and PO₄. Ordination and classification (CANOCO and TWINSPAN) showed that diatom assemblages in the Nairobi River responded strongly to water quality changes with respect to concentrations of NO₃, NO₂, total dissolved solids and temperature. Taxa common at less impacted upstream sites included Gomphonema gracilis, Anomoeoneis brachysira and Fragilaria biceps; while common taxa at midstream sites with agricultural catchments were Gomphonema parvulum, Navicula cryptocephala, N. schroeteri, N. bryophila, N. halophila, Nitzschia linearis var. linearis and Cymbella silesica. Achnanthes minutissima var. saprophila, Gomphonema angustum, Navicula subminuscula, N. arvensis, Nitzschia palea and N. umbonata were most common at urban sites, which were polluted by residential and industrial effluents. Trophic diatom indices suggested that water quality was poor at most sites in the Nairobi River. Most sites along the river had low Generic Diatom Index values, GDI (<12) and high Trophic Diatom Index values, TDI 73–78 (median = 76) and 75–84 (median = 77) for artificial and natural substrates, respectively. This study showed that diatoms' response on natural and artificial substrates were similar and reflected environmental conditions correctly.     

Occurrence of water molds in relation to hydrogen ion concentration in some lakes of Nainital,India

26 species of water molds belonging to Blastocladiales, Saprolegniales, Lagenidiales and Peronosporales were found to be different in their pH tolerance.