Observation and modeling of NPP for Pinus elliottii plantation in subtropical China

Based on the stem analysis of 59 individuals of Pinus elliottii in combination with tree biomass models, we calculated annual biomass increment of forest plots at Qianyanzhou Ecological Station, Chinese Academy of Sciences in subtropical China. In addition, canopy layer and community NPP were calculated based on 12 years’ litter fall data. NPP of the 21-year-old forest was estimated by using the BIOME BGC model; and both measured NPP and estimated NPP were compared with flux data. Community biomass was 10574 g · m⁻²; its distribution patterns in tree layer, shrub layer, herbaceous layer, tree root, herbaceous and shrub roots and fine roots were 7542, 480, 239, 1810, 230, 274 and 239 g · m⁻², respectively. From 1999 to 2004, the average annual growth rate and litter fall were 741 g · m⁻² · a⁻¹ (381.31 gC · m⁻² · a⁻¹) and 849 g · m⁻² · a⁻¹ (463 gC · m⁻² · a⁻¹), respectively. There was a significant correlation between annual litter fall and annual biomass increment; and the litter fall was 1.19 times the biomass increment of living trees. From 1985 to 2005, average NPP and GPP values based on BGC modeling were 630.88 (343.31–906.42 gC · m⁻² · a⁻¹) and 1 800 gC · m⁻² · a⁻¹ (1351.62–2318.26 gC · m⁻² · a⁻¹). Regression analysis showed a linear relationship (R ²=0.48) between the measured and simulated tree layer NPP values. NPP accounted for 30.2% (25.6%–32.9%) of GPP, while NEP accounted for 57.5% (48.1%–66.5%) of tree-layer NPP and 41.74% (37%–52%) of stand NPP. Soil respiration accounted for 77.0% of measured tree NPP and 55.9% of the measured stand NPP. NEE based on eddy covariance method was 12.97% higher than the observed NEP. Supported by the National Key Basic Research Special Foundation of China (Grant No. 2002CB4125), International Joint Research Project under Ministry of Science and Technology of China (Grant No. 2006DFB91920)     

Control of primary productivity and the significance of photosynthetic bacteria in a meromictic kettle lake. Mittlerer Buchensee,West-Germany

During 1986 planktonic primary production and controlling factors were investigated in a small (A₀ = 11.8 · 10³ m², Z_max = 11.5 m) meromictic kettle lake (Mittlerer Buchensee). Annual phytoplankton productivity was estimated to ca 120 gC · m^–2 · a^–1 (1,42 tC · lake^–1 · a^–1). The marked thermal stratification of the lake led to irregular vertical distributions of chlorophylla concentrations (Chla) and, to a minor extent, of photosynthesis (A_z). Between the depths of 0 to 6 m low Chla concentrations (< 7 mg · m^–3) and comparatively high background light attenuation (k_w = 0,525 m^–1, 77% of total attenuation due to gelbstoff and abioseston) was found. As a consequence, light absorption by algae was low (mean value 17,4%) and self-shading was absent.Because of the small seasonal variation of Chla concentrations, no significant correlation between Chla and areal photosynthesis (A) was observed. Only in early summer (June–July) biomass appears to influence the vertical distribution of photosynthesis on a bigger scale. Around 8 m depth, low-light adapted algae and phototrophic bacteria formed dense layers. Due to low ambient irradiances, the contribution of these organisms to total primary productivity was small. Primary production and incident irradiance were significantly correlated with each other (r² = 0.68). Although the maximum assimilation number (P_opt) showed a clear dependence upon water temperature (Q₁₀ = 2.31), the latter was of minor importance to areal photosynthesis.     

Seasonal dynamics of algal biomass and allochthonous input of coarse particulate organic matter in a low-order sandstone stream (Weidlingbach, Lower Austria)

From December 1997 to December 1998, benthic algal biomass and the input of allochthonous coarse particulate organic matter (CPOM) were investigated in bi-weekly intervals at two sampling stations (shaded and sunny) of the Weidlingbach, a fourth order sandstone stream in the Wienerwald. A total of 41 benthic algal taxa was collected, belonging to the groups Cyanobacteria (4 taxa), Bacillariophyceae (33), Rhodophyta (1), Chrysophyceae (1) and Chlorophyta (2). At the shaded site, periphyton dry mass ranged from 13 g m⁻² in April to 440 g m⁻² in August (annual mean = 93 g m⁻²), at the sunny site from 3 g m⁻² in May to 512 g m⁻² in late fall (annual mean = 70 g m⁻²). Based on the algal carotenoid pattern, Bacillariophyceae were most abundant in fall and winter while Chlorophyceae dominated during summer. Mean annual standing stock of chlorophyll-a was 8.65 μg cm⁻² at the shaded station and 7.53 μg cm⁻² at the sunny site. Annual allochthonous CPOM input rates ranged from 382 to 665 g dry mass m⁻² for aerial input and from 1006 to 1062 g DM m⁻¹ of stream length for lateral input. Lateral input rates were influenced by the bank inclination; the temporal distribution of aerial input showed an autumnal maximum (61-65% of the total). Direct CPOM input was significantly highest (P<0.05) during the period of defoliation from October to November. In the course of this period, 61.1% (shaded) to 64.9% (sunny) of the annual CPOM dropped into the brook, yielding daily input rates of 6.6 to 4.0 g DM m⁻². From December to September, daily direct input rates decreased to 0.84 g DM m⁻² (shaded) and 0.44 g DM m⁻² (sunny). At both sites, retention capacity was high; 70% of marked leaves released along transects were retained by coarse sediment particles within 40 m from the starting point. The annual mean of periphyton dry mass made up 52% of CPOM standing stock at the shaded site and 39% at the sunny site.     

Primary Productivity Studies on Freshwater Fish-Ponds of Bhagalpur,India

A one year study from October 1972 to September 1973 in four freshwater fishponds of Bhagalpur (87° 02' E long, and 25° 15'N lat.), India, has shown that a high phytoplankton primary production occurred twice during the annual cycle. There were seasonal variations in the production rate with a great fluctuation in the maximum and minimum values (3 … 4 times). Amongst the ponds studied, the highest daily production recorded was 6.93 g C/m²/day in Pond I and the minimum was 0.82 g C/m²/day in Pond II. The highest annual gross production was estimated to be 1611.98 g C/m²/y in Pond I, next in the order was 1543 g C/m²/y in Pond IV and then 1155.7.5 g C/m²/y in Pond I and the minimum was 641.75 C/m²/y in Pond II. It has also been observed that in certain months the net:gross ratio recorded was zero, while the community respiration as percentage of the gross production value reached 100% in few months. A comparison has been made in the annual production of temperate and tropical freshwater systems and this indicates that tropical waters are more productive than the temperate waters. Various physico-chemical factors such as rainfall, light, temperature and alkalinity may regulate or limit production.     

Phycoperiphyton Development on an Artificial Substrate in the River Wye System,Wales, U. K. Part 1: Biomass Variation

The phycoperiphyton on Perspex slides is investigated after an exposure for four weeks at six stations in the upper course of the River Wye System from June 1979 to June 1981. The pigment contents were between 0.1 and 48 mg/m² chlotophyll-a as well as 0.01 and 18 mg/m² phaeophytin with a unimodal or bimodal annual variation (minima in winter, maxima in April and July). The biomass was between 55 and 11,000 cells/cm² and is closely correlated with chlorophyll in the annual variation. The algal community colonizing the artificial substrate shows only a very slight similarity to that on the natural stones of the water. The SØRENSEN index lies between 0.1 and 0.7, the biomass on the artificial substrate amounts to only 0.7… 0.01 ‰, the chlorophyll quantity only 0.5… 0.007‰, the phaeophytin quantity only 1… 0.003‰ of the values on the natural stones. Therefore, the periphyton on artificial substrates represents only a more or less restricted selection of the real natural phycoperiphyton. At four of the six stations, biomass and chlorophyll are positively correlated with each other and with temperature and phosphorus concentration and negatively correlated with flow, current velocity, oxygen concentration, hardness and nitrate concentration.     

Natural recolonization of a productive tropical pond: Day to day variations in the photosynthetic parameters

Chlorophyll pigments (CHL), primary productivity (PP) and particulate nitrogen (N_p) in relation to several environmental factors were monitored during planktonic colonization of an aquaculture pond (Layo, Côte d'Ivoire). How interactions between the organisms are established in an initially azoic environment were investigated. From March, 15 (D1) to March, 31 (D16), the system transformation went through three stages. First, a precolonization by heterotrophic microbial community from D1 to D2 (N_p < 1 m maximum at D2: 243 mg m^–2; CHL around 0). Then, a pioneer microalgal community developped from D3 to D7 (maximum CHL on D6: 19 mg m^–2; PP: 1.0 g C m^–2 d^–1) with a significant contribution of picoplankton (CHL and PP < 3 m: 33 and 23% of the total, respectively). Finally, a second microalgal colonization was noticed from D9 to D12 (maximum CHL: 55 mg m^–2, PP: 2.8 g C m^–2 d^–1), largely dominated by nanoplankton (CHL and PP > 3 m: 95 and 99% of the total, respectively). Overall, photosynthetic activity appeared to be closely linked to algal biomass. The study of autotrophic biomass and activity in different size classes in relation to the other parameters allowed us to precise the origin of the biomass fluctuations. The first bloom appeared to be controlled by selective grazing on small algae. The second algal development ended when N requirement represented at least 69% of N supply (in the N — NH₄ form). This control was enhanced by the appearance of rotifers, leading to a more complex equilibrium.     

Phytoplankton productivity in Lake Lugano before water treatment

A study of phytoplankton primary productivity was carried out on Lake Lugano before the installation of sewage treatment plants. Average day rates of 1.9 g C·m² and annual production of 690 g C·m² were estimated. Primary productivity was also evaluated by calculations based upon Secchi disc and light data. The results show the high cultural eutrophication state of this lake.     

The effect of periphyton on the light environment and production of Potamogeton perfoliatus L. in the mesotrophic basin of Lake Balaton

Light within the littoral zone affects the productivity and interaction between periphyton and its macrophyte substrate. The effect of periphyton on macrophyte photosynthesis, seasonal variation and vertical distribution of periphyton on artificial substrates (plastic strips), and the effect of periphyton on the light environment was studied in Lake Balaton. Data showed that an average of 4.1 ± 0.4 mg (dry weight) cm^?2 of periphyton had accumulated on the plastic strips after 8.8 ± 0.4 days. This biomass corresponded to 294 ± 30 μg m^?2 chl-a of epiphytic algae and blocked 92.3 ± 0.8 % of the depth specific radiation. Seasonal variation and specific vertical distribution of periphyton were observed. The most active time of periphyton accumulation corresponded to spring up until mid-June. Later in the year, the amount of periphyton significantly decreased. The optimal conditions for periphyton accumulation were at 30–40 cm depth. Most of the light reaching the adaxial leaf surface was attenuated by periphyton, decreasing the production of Potamogeton perfoliatus by 60–80 %. This increased the importance of backscattered light that corresponded to 10–15 % of the macrophyte production. A smaller part of the periphyton consisted of precipitated inorganic material, while epiphytic algae, making up the majority of the periphyton, were connected to both benthic (dominantly benthic penales) and pelagic (very close seasonal dynamics of pelagic and epiphytic biomass) algae. Periphyton affects macrophyte production especially in spring and in the upper water layers even in a mesotrophic water body. This increases the importance of the light absorbed through the abaxial side of the leaf and confirm the role of periphyton in transition from clear to turbid water states.     

Substrate influence and temporal changes on periphytic biomass accrual and metabolism in a tropical humic lagoon

We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6 mg cm⁻², but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44 μg cm⁻² throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO₂ to the system.     

Litterfall,litter and associated chemistry in a dry sclerophyll eucalypt forest and a pine plantation in south-eastern Australia: 1. Litterfall and litter

Litterfall was measured in a dry schlerophyll eucalypt forest and a nearby Pinus radiata plantation of similar tree density and basal area near Canberra in south-eastern Australia. Total annual litterfall for the eucalypts was 329 g m⁻², compared with 180 g m⁻² for the pines, with the bark component being 52 g m⁻² for eucalypts and zero for pines. Barkfall did not occur for the eucalypts during the drought of 1982–1983 but complete bark shedding occurred during the subsequent very wet year when barkfall was 177 g m⁻² for Eucalyptus rossii and 146 g m⁻² for Eucalyptus mannifera (9·3 and 7·6 g m⁻² of basal area, respectively). Barkfall of E. rossii responded to rainfall in the period autumn to early summer, whereas E. mannifera responded to summer rainfall. In the eucalypt forest floor-litter was stratified into a surface layer where the components were substantially intact, and a cohesive layer where the components were fragmented and bound together by fungal hyphae. The amount and residence times of loose and cohesive floor-litter were 1056 g m⁻² and 3·2 years, respectively, for the loose litter layer; and 1164 g m⁻² and 3·5 years for the cohesive layer. The litter biomass represented 17% of the estimated total above-ground biomass of 127 tonnes ha⁻¹. A previous study showed roots to be 25% of total biomass, suggesting a total biomass of 167 tonnes ha⁻¹. © 1998 John Wiley & Sons, Ltd.     

Longitudinal and temporal patterns of benthic coarse particulate organic matter in the Agüera stream (northern Spain)

Benthic coarse particulate organic matter (CPOM) was studied between November 92 and December 93 at four sites along the longitudinal gradient of the Agüera stream system (Northern Spain). CPOM was sorted in four main categories: leaves (several species), fruits and seeds, twigs and debris. Headwater site showed higher densities of total CPOM, leaves and twigs than downstream reaches, but no regular longitudinal pattern of change was noticed. The ranges of mean CPOM standing stock at the sampling sites were 20.5–74.1 g AFDW m^–2 (site B), 9.9–47.7 g AFDW m^–2 (site 5), 4.3–21.4g AFDW m^–2 (site 7) and 9.8–37.9 g AFDW m^–2 (site 9). The particulate matter at downstream sites was in a more advanced stage of breakdown probably as a result of processing and transport from upstream reaches. Leaves species composition of benthic CPOM clearly reflected the type of riparian vegetation at each site. The timing of inputs and the hydrologic regime appeared to act together influencing temporal dynamics of benthic CPOM. A gradual temporal change in species composition of benthic leaf litter was observed under natural mature deciduous forest: first alder, later chestnut and finally oak.     

新疆乌伦古湖大型底栖无脊椎动物的群落结构

乌伦古湖是我国十大内陆淡水湖之一,同时也是新疆维吾尔自治区的第二大湖泊和主要渔业基地.近年来,随着气候变化和人为因素的影响,湖区水体营养状况、生物群落组成等均发生了较大变化.为揭示该湖大型底栖无脊椎动物的群落结构特征及其对生态系统变化的响应,2006年11月至2008年7月设28个采样点对大型无脊椎底栖动物的群落结构特...     

Benthic macroinvertebrate communities of three tropical,warm monomictic Mexican lakes

Most studies of benthic macroinvertebrate communities are from shallow lakes or restricted to the littoral zone of deep, temperate lakes, with just a few dealing with the deep benthos. Furthermore, the deep benthic macroinvertebrate communities of tropical lakes are almost unknown. The present work describes the benthic macroinvertebrate communities of three tropical, warm monomictic lakes in “Lagunas de Montebello” National Park, Mexico, by describing the differences along the bathymetric profile, from the littoral down to the profound benthos. We studied the benthic macroinvertebrate communities in the two contrasting hydrodynamic periods of the warm monomictic lakes: a) stratification, when the hypolimnion becomes anoxic, and b) mixing, when the water column becomes oxygenated. We expected: 1) a reduction in the benthic macroinvertebrate taxonomic richness, density, and biomass from the littoral to the deep zone, 2) an impoverished benthic macroinvertebrate community while stratified (anoxia) compared to mixing (oxygenated), and 3) depletion in the taxonomic richness, density, and biomass of the profundal benthic macroinvertebrates in the tropical compared to temperate lakes. We found: 1) a decreasing trend in taxonomic richness (6 ± 2–3 ± 1 taxa), density (1868.7 ± 1069.7–349.1 ± 601.8 in. m⁻²) and biomass (277.8 ± 188.9–85.1 ± 95.6 mg C m⁻²) from the littoral to the deep zone; chironomids dominated the littoral zone, while oligochaetes dominated the deep zone. 2) Lower density and biomass but not taxonomic richness while stratified (4 ± 3 taxa; 586.2 ± 527.6 in. m⁻²; 81.6 ± 164.3 mg C m⁻²) compared to mixing (4 ± 3 taxa; 877.5 ± 1051.4 in. m⁻²; 190.1 ± 131.1 mg C m⁻²). 3) lower taxonomic richness and density but not biomass in tropical Montebello oligotrophic lakes (3 ± 3 taxa; 349.1 ± 601.8 in. m⁻²; 85.1 ± 195.6 mg C m⁻²) compared to temperate analogous (2–48 taxa; 492−83,189 8 in. m⁻²; 0.13−201.5 mg m⁻²). We conclude the early onset and long-lasting hypolimnetic anoxia restrict the benthic macroinvertebrate community radiation and diversification in tropical, oligotrophic, warm monomictic lakes.     

Petroleum hydrocarbons in zooplankton faecal pellets from the Sargasso Sea

Analysis of hexane-extractable hydrocarbons in zooplankton collected off Bermuda in August 1979, and their faecal pellets, gave an estimated removal rate of hydrocarbons from surface waters by ‘grazing’ of 16–46 μg m^?2 for a 4 h period. With a number of assumptions, this can be translated to 8–23 mg m^?2 yr^?1. When compared to the annual input due to petroleum discharge in the currents feeding the Sargasso Sea (18–70 mg m^?2 yr^?1 hexane-extractable hydrocarbons), this result implies that zooplankton are an important factor in the short-term removal of petroleum residues from open ocean surface waters.     

武汉东湖超微藻生态学的初步研究

论述了武汉东湖超微藻年数量,叶绿素含量,生产量分布,于室内模拟了不同光强与不同浓度Ｐ营养对超微藻光合性能的影响,同时与国外海洋与淡水超微藻的生产力,生物量和各自所占百分比进行了比较。文中还就东湖超微藻分布与生态环境之间关系进行了讨论。     

Seasonal and interannual variation of the phytoplankton and copepod dynamics in Liverpool Bay

The seasonal and interannual variability in the phytoplankton community in Liverpool Bay between 2003 and 2009 has been examined using results from high frequency, in situ measurements combined with discrete samples collected at one location in the bay. The spring phytoplankton bloom (up to 29.4 mg chlorophyll m⁻³) is an annual feature at the study site and its timing may vary by up to 50 days between years. The variability in the underwater light climate and turbulent mixing are identified as key factors controlling the timing of phytoplankton blooms. Modelled average annual gross and net production are estimated to be 223 and 56 g C m⁻² year⁻¹, respectively. Light microscope counts showed that the phytoplankton community is dominated by diatoms, with dinoflagellates appearing annually for short periods of time between July and October. The zooplankton community at the study site is dominated by copepods and use of a fine mesh (80 μm) resulted in higher abundances of copepods determined (up to 2.5 × 10⁶ ind. m⁻²) than has previously reported for this location. There is a strong seasonal cycle in copepod biomass and copepods greater than 270 μm contribute less than 10% of the total biomass. Seasonal trends in copepod biomass lag those in the phytoplankton community with a delay of 3 to 4 months between the maximum phytoplankton biomass and the maximum copepod biomass. Grazing by copepods exceeds net primary production at the site and indicates that an additional advective supply of carbon is required to support the copepod community.     

Studies on Primary Productivity and some Hydrochemical Aspects of a Polluted Water-body of the Himalayan Jhelum Valley

The lake without any outlet (11 ha, 55000 m³, z_max 2,25 m) has a weak thermal stratification with maximum surface temperatures of 32.5 °C. The annual variation of temperature and depth of visibility is unimodal, with the maxima or minima in August. Phytoplankton consists mainly of Cyanophyceae. The primary production determined by the light-dark bottle technique (oxygen method) varies in the annual variation between 0.3… 0.5 g m^?2 d^?1 C (winter) and 3.4… 4.6 g m^?2 d^?1 C (summer); as the annual means of 1975 and 1976 there were found 1.9 and 2.4 g m^?2 d^?1 C, resp., gross production at a utilization of 0.42… 2.85% of the radiation energy. The chemism is a well-buffered hydrogen-carbonate water (pH 8.1… 9.0) with 74… 90 mg/1 Na and 20.5… 31.5 mg/1 K and with a good nutrient supply (20… 40 μg/1 PO₄—P and 100… 240 μg/1 NO₃—N) at the same time.     

Seasonal Variation in Primary Productivity and its Interrelationship with Chlorophyll in the Lake Jaisamand (Rajasthan,India)

Lake Jaisamand near Udaipur (Rajasthan) is one of the oldest man-made lakes in India. The primary productivity of the lake showed a bimodal pattern with a first peak of a higher magnitude in July (7.605 g/m₂d C) and the second of a lower magnitude (5.851 g/m₂ dC) in December. The minimum production was 2.455 g/m₂ dC in November. The chlorophyll values were high during low water levels of summer and low during monsoon months when the water level rises, thereby dispersing the phytoplankton biomass and decreasing its density per unit of water volume. From the results obtained it appears that beside temperature and transparency, the trophogenic area and seasonal water level fluctuations have a considerable influence on the primary productivity in this lake. Based on annual production rates and chlorophyll values lake Jaisamand could be regarded as an eutrophic waterbody.