首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
The life cycle and growth ofPotamogeton crispus L. were studied in a shallow pond, Ojaga-ike. With respect to the shoot elongation and seed and turion formations, the life cycle of this plant in the pond could be divided into following five stages: germination, inactive growth, active growth, reproductive and dormant stages. It was suggested that the plant showed these successive stages depending mainly upon water temperature. The turions germinated on the bottom in autumn when the water temperature fell below ca. 20 C. The plant showed hardly any growth during winter (December—early March) when the temperature was below 10 C. In the spring when the bottom water temperature rose to above 10 C (mid-March), the plant started to grow again and the shoot elongated rapidly at the rate of 4.2 cm day−1 until the shoot apex reached the pond surface in late April. Both the increment of node number and the internodal elongation were associated with this rapid shoot growth. On 10 May (last sampling date), the mean values of shoot length, internodal length and the number of nodes estimated for 10 predominant plants were 238.2±5.6 cm, 7.1±0.8 cm and 34.9±4.0 cm, respectively. The turion formation and flowering occurred during the period from mid-April to mid-May when the surface water temperature ranged 19 and 22 C. The dry weight of a plant reached the maximum mean value of 1180 mg on 10 May. At its peak biomass, an individual plant produced 1–10 turions (5.5 on average) of which the mean individual turion dry weight was 53.2 mg. The turion dry weight accounted for ca. 42% of the total plant biomass m−2 at that time.  相似文献   

2.

To understand the mechanism of how Phragmites australis makes valuable floating mat biotopes under oligotrophic conditions, we investigated the environmental (water chemistry) and vegetational characteristics (growth, plant species richness, and floristic composition) of a floating mat consisting of three main mat-forming species with a zonal distribution (P. australis on the land side of the floating mat, Zizania latifolia on the middle area, and Typha angustifolia on the water side). Although they showed relatively low growth in the floating mat, compared to those in land-based wetlands, P. australis grew better than other mat-forming species in terms of shoot height and biomass production. Specifically, P. australis made more below-ground parts (593?±?38 g/m2) than other mat-forming species (Z. latifolia, 100?±?10 g/m2; T. angustifolia, 167?±?8 g/m2) and more companion species were found in P. australis-dominated plots (8.5?±?1.0 species/m2) than other plots (Z. latifolia-dominated plots, 2.7?±?0.6 species/m2; T. angustifolia-dominated plots, 1.0?±?0.0 species/m2). The larger amount of below-ground P. australis parts could contribute to thicker and denser mat structures, possibly providing more favorable habitats for neighboring plant species, thus facilitating more companion species within the P. australis-dominated area of the mat.

  相似文献   

3.
《Aquatic Botany》1986,24(4):335-341
Seasonal and year-to-year variations in the growth of Zostera marina L. were measured at three sites in two locations in the lower Chesapeake Bay between 1978 and 1980. The maximum values for the 1979 above- and belowground standing crop ranged from 161–336 g dry wt m−2 and 61–155 g dry wt m−2, respectively, leaf length was 19.6–59.7 cm and shoot density 1418–2576 shoot m−2. Values for 1980 tended to be greater and may be related to climatical differences between the two years. Maximum values were usually recorded in the months of June and July when water temperatures were between 20 and 25°C. Significant loss of leaves occurred in July and August, when water temperatures ranged between 25 and 30°C, while new shoots began to appear more rapidly in late September as water temperatures dropped below 20°C. The greatest increase in all growth parameters occurred from April to June during which time reproductive shoots were present, and accounted for up to 25% of the total number of shoots.  相似文献   

4.
Intensive polyculture of blue tilapia, Oreochromis aureus, and common carp, Cyprinus carpio was conducted to determine their growth capacity and the accompanying water quality transitions in a 376 m2 (207 m3) fish pond without aeration or water exchange. A total of 485 fingerlings (290 tilapia and 195 carp) averaging 72 g each (total 35 kg) was stocked and fed commercial floating pellets (36% protein-6%-N) at the approximate daily rate of 3% of the fish biomass six days each week. The total net fish growth was 159.4 kg (4.2 t ha–1) with an average growth of 199.5 g per fish through the 96 days feeding period — 6 June to 7 September 1984. The s conversion ratio for the commercial feed was 1.3.Physiochemical patterns in the pond water were directly related to the rise and fall of turbidity through the course of the production trial. During one period of low turbidity, a biological inversion was evident with pH and dissolved oxygen measured at higher levels near the pond bottom and increasingly lower toward the surface. It is postulated that settled phytoplankton formed a photosynthetically-active algal mat on the pond bottom. The implications for potential fish kills can be significant.  相似文献   

5.
The monthly productivity, standing stock, plant size and density of Ecklonia radiata (C.Ag.) J. Agardh is presented for a 2-yr period. Annual production was 20.7 kg wet wt · m?2 with maximum growth of 0.9% per day in spring (October–December) and minimum growth of 0.2% per day in late summer. (March–April). A close negative correlation was found between spring and summer growth and water temperature. Maximum biomass (18 kg wet wt · m ?2) did not coincide with maximum growth but occurred in late summer. Minimum biomass (6 kg wet wt · m ?2) occurred in winter. An estimate of erosion of plant material from the kelp bed was made from these data and a hypothesis concerning the ultimate destination of eroded and removed kelp plants was formulated.  相似文献   

6.
The structure and production characteristics of microbial communities from the Urinskii alkaline hot spring (Buryat Republic, Russia) have been investigated. A distinctive characteristic of this hot spring is the lack of sulfide in the issuing water. The water temperature near the spring vents ranged from 69 to 38.5°C and pH values ranged from 8.8 to 9.2. The total mineralization of water was less than 0.1 g/liter. Temperature has a profound effect on the species composition and biogeochemical processes occurring in the algal-bacterial mats of the Urinskii hot spring. The maximum diversity of the phototrophic community was observed at the temperatures 40 and 46°C. A total of 12 species of cyanobacteria, 4 species of diatoms, and one species of thermophilic anoxygenic phototrophic bacteria, Chloroflexus aurantiacus, have been isolated from mat samples. At temperatures above 40°C, the filamentous cyanobacterium Phormidium laminosum was predominant; its cell number and biomass concentration comprised 95.1 and 63.9%, respectively. At lower temperatures, the biomass concentrations of the cyanobacterium Oscillatoria limosa and diatoms increased (50.2 and 36.4%, respectively). The cyanobacterium Mastigocladus laminosus, which is normally found in neutral or slightly acidic hydrothermal systems, was detected in microbial communities. As the diatom concentration increases, so does the dry matter concentration in mats, while the content of organic matter decreases. The concentrations of proteins and carbohydrates reached their maximum levels at 45–50°C. The maximum average rate of oxygenic photosynthesis [2.1 g C/(m2 day)], chlorophyll a content (343.4 mg/m2), and cell number of phototrophic microorganisms were observed at temperatures from 45 to 50°C. The peak mass of bacterial mats (56.75 g/m2) occurred at a temperature of 65–60°C. The maximum biomass concentration of phototrophs (414.63 × 10?6 g/ml) and the peak rate of anoxygenic photosynthesis [0.42 g C/(m2 day)] were observed at a temperature of 35–40°C.  相似文献   

7.
We studied vegetation changes in a small floating mat bog in Mizorogaike Pond (Kyoto, Japan), which had experienced a severe decrease in the number and area of hummocks caused by nutrient loading in the 1960s and 1970s, to examine whether reducing the extent of nutrient loading can restore degraded wetland vegetation. However, nutrient loading in the region has been minimized since the 1980s. We examined the distributions of hummocks and Sphagnum cuspidatum mats in 1980, 1988, and 2006, as well as nine major vascular plants that dominated the hollows on the floating mat in 1980 and 2006. The total area of normal hummocks formed by Sphagnum palustre increased from 5865.3 m2 in 1980 to 5913.6 m2 in 1988 and 8485.2 m2 in 2006. The total area of the S. cuspidatum mats also changed, from 416.4 m2 in 1980 to 322.3 m2 in 1988 and 1012.5 m2 in 2006. Examination of the spatial distribution patterns of major plants revealed that emergent plants decreased in the northern part of the mat, but increased in the southern part. Thus, the improved pond water quality was effective at restoring hummocks, although nutrient loading may have caused some irreversible changes in the wetland vegetation.  相似文献   

8.
We examined the impacts of macrophyte beds dominated by a canopy-forming (Myriophyllum sibiricum) and a meadow-forming (Chara canescens) species on bottom shear stress (τ) and resuspension in shallow Lake Christina, Minnesota (U.S.A.). Studies were conducted in late summer, 1998, when macrophyte biomass levels exceeded 200 g m?2, and in early summer, 2000, when biomass was greatly reduced (<20 g m?2) in both plant beds. The critical shear stress (τc) of sediments, measured experimentally in the laboratory, was low (1.4 dynes cm?2) indicating potential for resuspension in the absence of macrophytes. During 1998, turbidity was low at the M. sibiricum and Chara station, rarely increasing when calculated bottom τ (calculated from wave theory assuming no biomass obstruction) exceeded τsub c sub, indicating that both beds reduced sediment resuspension at high biomass levels. In situτ (estimated τ), measured via gypsum sphere dissolution, did not exceed τc above the sediment interface in either bed during 1998. In contrast, sediment resuspension occurred in both beds during similar high winds in 2000. However, estimated τ was lower than calculated bottom τ, suggesting that at low biomass, macrophytes were having some impact on τ.  相似文献   

9.
Seasonal growth of Typha latifolia L. stands in five oxbow lakes of the Athabasca River in the boreal forest zone of Alberta, Canada, was monitored by both the harvest technique and double sampling by regression. The technique for calculating mean biomass and variance for the double sampling procedure is described. The relationship between stem weight and height was linear for flowering stems, but a logarithmic transformation of weight was used for the non-flowering stem regressions. Growth began in late May and stems reached maximum weight by mid-August. Stem mortality (up to 14%) was highest at sites with high stem density, but mortality was limited to small stems at all sites. Total biomass of these stems was less than 4% of the peak above-ground standing crop. In nutrient-poor sites, Typha was found on floating organic mats, but in more nutrient rich sites on grounded substrates. Peak above-ground biomass ranged from 456 to 848 g m?2, generally in response to the successional and nutrient status of the oxbow lake. Sites returned to an earlier stage of succession by flooding had larger stems and greater biomass.  相似文献   

10.
Ranunculus kadzusensis is an endangered aquatic plant species that commonly reproduces in the rice paddies of Korea and Japan during winter and early spring. Here, we investigated the effects of main aquatic environmental factors—light, temperature, and water depth—on its growth, with the goal of seeking information that will contribute to its in situ conservation. As the amount of shading increased, biomass, maximum shoot length, number of branches, flowers, and fruits, main stem diameter, and maximum leaf length decreased. Although seed germination occurred under a 12-h photoperiod and at either 30/20°C (day/night) or 20/15°C, most plants died at the higher temperature. Survival was 0% for surface-grown plant sets when tested in a wintertime pond experiment. The rate of maximum shoot extension was greatest for plants grown at depths of 50 and 100 cm versus those at 20 cm. Thus, we demonstrated that R. kadzusensis is intolerant of high temperatures and shade, which may explain why its growth is limited to paddies with no shading and where temperatures are low early in the year, before rice cultivation begins.  相似文献   

11.
Chemical properties of waters and their seasonal changes were studied in Mizorogaike Pond, a system of pond and floating mat. The following six sites including contrasting habitats and water conditions were monitored to assess nutrient dynamics in the system: 1) a pool on the mat, 2) margin of aSphagnum cuspidatum community, 3) an artificial ‘well’ (water layer beneath the floating mat), 4) aMenyanthes trifoliata community in a hollow, and 5) & 6) two sites in the open water. On the floating mat, the water around theSphagnum community had lower pH values, while that in theM. trifoliata community had higher pH values. This difference was related to the influence of flood water, the extent of which was determined by the microtopography. Seasonal changes in water chemistry on the mat suggested that pond water flooding the mat in late autumn and winter is important for the nutrient supply to the mat surface vegetation in this system. Water chemistry of the ‘well’ suggested that the diffusion of inorganic nitrogen occurs from beneath the peat layer. Two types of cluster analysis based on the mean values for chemical variables and the patterns of fluctuation in these variables were performed. The six sites were classified into similar groups which were identified by water type (pool, hollow, well and open water) by both types of analysis. The results showed that a common kind of perturbation should operate in determining the status of nutrient dynamics in the various water types.  相似文献   

12.
A pond with a surface area of 0.94 ha and a maximum depth of 1.6 m, situated on land owned by a wastewater treatment plant in Olsztynek (Poland), was filled with water from underground springs in the pond bottom. Twice during the production season, the pond was fed with sewage which had been biologically treated in sequencing batch reactors (SBR). No commercial feed or medicinal products were applied to the pond and natural feed in the pond was the only source of nutrition for the fish. After the production season, pikeperch and carp fingerlings (aged 0+), weighed 8.4 ± 1.2 g fish?1 and 62.1 ± 13.6 g fish?1, respectively.The microbiological examinations included tests of the pond water and the contents of the digestive tract, skin mucus and the muscles of the fingerlings. In the water the total cell count, heterotrophic bacteria count at a temperature of 22 °C and 37 °C (HPC 22 °C and 37 °C), coliforms, fecal coliforms, Streptococcus faecalis, Salmonella sp. and Aeromonas hydrophila, were recorded. The same groups of bacteria were noted in the analyzed fish tissue without the total cell count. In addition, the antibiotic sensitivity of A. hydrophila, isolated from all the examined environments, was tested.The low count of all examined groups of bacteria in the pond water was noted. The common carp tissues were more contaminated than the pikeperch tissues, but the microbial quality of both species was satisfactory. A. hydrophila strains proved to be highly sensitive to the tested antibiotics. The results of this study indicate that a high microbiological quality in the fingerlings was achieved thanks to the seasonal feeding of pond water by treated sewage.  相似文献   

13.
New potential sites for the critically-endangered, aquatic carnivorous plantAldrovanda vesiculosa L. (Droseraceae) were selected in North and South Bohemia (Czech Republic) and both its seasonal growth dynamics and overwintering rate were investigated. Groups of either 5 or 10 plants were planted in 1×1 m nylon enclosures in selected shallow, dystrophic waters at the end of May. Plant growth characteristics and water chemistry were investigated at 2 to 5 week intervals over the 1994 growing season inside ten enclosures placed at six sites. Within seven enclosures at three sites, the seasonal growth was very fast and 38–141 turions developed from the initial five plants. Water at these sites was mesotrophic with a high concentration of CO2 above 0.1 mmol.l?1 and pH between 6.2 and 7.6. At the other three sites, plant growth was very poor. The fastest plant propagation was found between late June and mid-August and corresponded with the warmest seasonal period. During this period, the doubling time of the total number of shoot apices was 16.4–34.9 days. Turions developed in mid-September and sank to the bottom by mid-October. In some enclosures, the turions overwintered on the wet bottom whereas they were submersed in the other ones. Though the turions were subject to frosts of up to ?20°C, none died due to the frosts. Grazing of turions by ducks or small rodents was found at some sites. The overwintering rate of turions at sites varied from 0 to 70% and was not related to seasonal growth rate. Most turions floated to the surface and germinated during late April-early May. It is suggested that considerable turion losses in stable, naturalAldrovanda stands are compensated for by fast seasonal shoot growth and branching which leads to the recovery of an abundant plant population.  相似文献   

14.
Phenol is a commonly found organic pollutant in industrial wastewaters. Its ecotoxicological significance is well known and, therefore, the compound is often required to be removed prior to discharge. In this study, plant-bacterial synergism was established in floating treatment wetlands (FTWs) in an attempt to maximize the removal of phenol from contaminated water. A common wetland plant, Typha domingensis, was vegetated on a floating mat and augmented with three phenol-degrading bacterial strains, Acinetobacter lwofii ACRH76, Bacillus cereus LORH97, and Pseudomonas sp. LCRH90, to develop FTWs for the remediation of water contaminated with phenol. All of the strains are known to have phenol-reducing properties, and grow well in FTWs. Results showed that T. domingensis was able to remove a small amount of phenol from the contaminated water; however, bacterial augmentation enhanced the removal potential significantly, i.e., 0.146 g/m2/day vs. 0.166 g/m2/day, respectively. Plant biomass also increased in the presence of bacterial consortia; and inoculated bacteria displayed successful colonization/survival in the rhizosphere, root interior and shoot interior of the plant. Similarly, highest reduction in chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and total organic carbon (TOC) was achieved by the combined application of plants and bacteria. The study demonstrates that the plant-bacterial synergism in a FTW may be a more effective approach for the remediation of phenol-contaminated water.  相似文献   

15.
Hourly drift samples were collected once each month over a 24 hour period for 10 months at the mouth of a channel returning heated coolant water from a steam electric generating station to a 330 ha reservoir. Most benthic macroinvertebrates existed at lower densities on the bottom of the channel than in the reservoir. No organisms were found in the channel during summer months when water temperatures reached 42.2°C. The most abundant organisms drifting from the channel were Chaoborus larvae which probably were drawn from the reservoir, through the condensors of the power plant, and down the effluent channel. The maixmum drift rate for Chaoborus larvae occured in August (8.91 × 104 mg/day) while the minimum rate occurred in December (3.92 × 102 mg/day). Chaoborus larvae exhibited a diurnal periodicity in drift corresponding to their nightly emergence from bottom sediments in the reservoir.  相似文献   

16.
Effects of aquatic vegetation type on denitrification   总被引:1,自引:0,他引:1  
In a microcosm 15N enrichment experiment we tested the effect of floating vegetation (Lemna sp.) and submerged vegetation (Elodea nuttallii) on denitrification rates, and compared it to systems without macrophytes. Oxygen concentration, and thus photosynthesis, plays an important role in regulating denitrification rates and therefore the experiments were performed under dark as well as under light conditions. Denitrification rates differed widely between treatments, ranging from 2.8 to 20.9 ??mol N m?2 h?1, and were strongly affected by the type of macrophytes present. These differences may be explained by the effects of macrophytes on oxygen conditions. Highest denitrification rates were observed under a closed mat of floating macrophytes where oxygen concentrations were low. In the light, denitrification was inhibited by oxygen from photosynthesis by submerged macrophytes, and by benthic algae in the systems without macrophytes. However, in microcosms with floating vegetation there was no effect of light, as the closed mat of floating plants caused permanently dark conditions in the water column. Nitrate removal was dominated by plant uptake rather than denitrification, and did not differ between systems with submerged or floating plants.  相似文献   

17.
A natural grassland in northeastern China dominated by Leymus chinensis (Trin.) was subject to drought treatments to determine the seasonal dynamics in resource partitioning to shoot and storage organs in response to drought. The growing season was divided into six stages according to the phenology of L. chinensis. Plant samples of L. chinensis were collected at each stage to determine biomass, gross calorific value, relative water content, and key mineral contents of plant parts, including rhizomes, roots, leaves, and stems. Resource partitioning to shoot and storage organs as measured by biomass, gross calorific value, and N, K+, and Na+ contents varied significantly among phenologic stages. Drought treatment (natural precipitation, 50–60 % of field capacity) significantly reduced biomass, gross calorific value, relative water content of shoot, and N and K+ contents in both shoot and storage organs, but it enhanced rhizome : shoot ratio and Na+ content. A negative correlation in biomass, gross calorific value, and K+ and Na+ contents between shoot and storage organs was found throughout the growing season, which may have been accentuated by drought when soil moisture was limited. Our results indicate that resource partitioning to storage plays an important role in regulating plant growth of L. chinensis, especially under drought conditions.  相似文献   

18.
The aim of this study was to analyze and model how biomass is allocated to the leaves, stems, and roots of perennial grass (reed canary grass, Phalaris arundinacea L., hereafter RCG) under elevated temperature (ET) (+approx. 3 °C) and CO2 (approx. 700 μmol mol?1) and with variable groundwater levels (high to low water levels) in a boreal environment. For this purpose, RCG plants were grown in environmentally controlled chambers over two growing seasons (April–September of 2009 and 2010), and the plant organ biomass (leaves, stems, and roots) was measured seven times over the entire growing season. The results showed that biomass production was mainly allocated to the leaves (LMF) and stems (SMF) early in the growing season, to the stems in the middle of the growing season, and to the roots (RMF) later in the growing season. Compared to ambient conditions, ET treatments increased LMF and SMF, and decreased RMF over the growing season under well-water conditions. Under low groundwater level, ET treatments decreased LMF and increased RMF throughout the growing season, and increased SMF in early periods and then decreased later in the growing season. CO2 enrichment did not significantly affect the seasonal allocation pattern between plant organs. The effect of the groundwater level on biomass allocation was stronger than that of the climatic treatments. In conclusion, plant phenology controlled the seasonal course of biomass allocation in RCG and climatic treatments affected biomass allocation to each of the three plant organs, while the direction and extent of climate-related changes in biomass allocation depended on the availability of groundwater. The influence of groundwater level appeared to be crucial for the carbon gain regarding the production of RCG biomass for energy purpose and the concurrent sequestration of carbon in soils under changing climate in the mire sites used to cultivate RCG.  相似文献   

19.
The growth of Salvinia molesta D.S. Mitchell, as affected by phosphorus supply and water temperature, was studied in a greenhouse using controlled water temperature baths at 16, 19 and 22°C. For significant responses to the phosphorus treatments to be obtained it was found necessary to use P-deficient plant propagules (containing <0.01% P on a dry matter basis). For these plants the highest relative growth rate and dry matter production occurred at 22°C when they received 10.01 mg PO4P l?1, but this was not significantly different from that of plants receiving 1.01 mg PO4-P l?1. Over a period of 21 days for plants receiving 0.02 mg PO4 l?1 the biomass increased 4-fold at 19°C and 6-fold at 22°C. In contrast, for plants receiving 10.01 mg PO4-P l?1 biomass was increased 20-fold at 19°C and 32-fold at 22°C. At the latter temperature, when receiving 60.01 mg PO4-P l?1, plants concentrated up to 1.3% of phosphorus on a dry matter basis, suggesting a possible use as a biological filter and purifier of contaminated waters.  相似文献   

20.
Data on the distribution of root biomass are critical to understanding the ecophysiology of vegetation communities. This is particularly true when models are applied to describe ecohydrology and vegetation function. However, there is a paucity of such information across continental Australia. We quantified vertical and horizontal root biomass distribution in a woodland dominated by Angophora bakeri and Eucalyptus sclerophylla on the Cumberland Plains near Richmond, New South Wales. The site was characterised by a duplex (texture contrast) soil with the A horizon (to 70 cm) consisting of loamy sand and the B horizon (to > 10 m) consisting of sandy clay. The topsoil had a smaller bulk density, a smaller water holding capacity but a larger organic component and a larger hydraulic conductivity in comparison to the subsoil. Root biomass was sampled to 1.5 m depth and declined through the soil profile. Whilst total biomass in the B horizon was relatively small, its contribution to the function of the trees was highly significant. Coarse roots accounted for approximately 82% of the root mass recovered. Lateral distribution of fine roots was generally even but coarse roots were more likely to occur closer to tree stems. Variation in tree diameter explained 75% of the variation in total below-ground biomass. The trench method suggested the belowground biomass was 6.03?±?1.21 kg m?2 but this method created bias towards sampling close to tree stems. We found that approximately 68% of root material was within a 2 m radius of tree stems and this made up 54% of the total number of samples but in reality, only approximately 5 to 10% of the site is within a 2 m radius of tree stems. Based on these proportions, our recalculated belowground biomass was 2.93?±?0.59 kg m?2. These measurements provide valuable data for modeling of ecosystem water use and productivity.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号