The estimation of current state of Lake Ladoga using mathematical models

This paper describes a mathematical simulation model of the transformation of organic matter and biogenic compounds. The model is validated with observations made on Lake Ladoga. Despite the approximate nature of the biogenic load data, a good agreement is obtained between the calculated substance concentrations and available observations made during individual seasons for different areas of the lake. The model was developed by the author Leonov and this paper presents new model results with accurate formulations for nitrogen and carbon components. Comparison with observational data base collected during 1976–1979 shows that the model results provide good simulation of the annual seasonal changes in material concentrations in the identified regions of the lake.     

A Test of Two Annual Cover Crops for Controlling Phalaris arundinacea Invasion in Restored Sedge Meadow Wetlands

Abstract Rapid establishment by aggressive plants such as Phalaris arundinacea (reed canarygrass) often interferes with sedge meadow establishment in restored prairie pothole wetlands in the mid‐continental United States. Introducing a cover crop during community establishment might suppress P. arundinacea invasion in restored prairie potholes by reducing resource availability. We evaluated two potential cover crops, Echinochloa crusgalli (barnyardgrass) and Polygonum lapathifolium (nodding smartweed), for suppressing P. arundinacea invasion in an experimental wetland using replacement series competition experiments. Further, we assessed the effects of E. crusgalli and P. lapathifolium on sedge meadow establishment by sowing Carex hystericina, a common wetland sedge, as a third species at a constant density in the replacement experiments. Echinochloa crusgalli, compared with no cover crop, reduced P. arundinacea biomass by more than 1,000 g/m² (65%) after two growing seasons. Polygonum lapathifolium did not affect P. arundinacea biomass. Dense E. crusgalli canopies in the first year and thick E. crusgalli thatch in the second year substantially reduced light availability for P. arundinacea establishment. Echinochloa crusgalli also reduced C. hystericina biomass by more than 1,800 g/m² (99%) after two growing seasons. Carex hystericina biomass was similar in plots sown with E. crusgalli to P. arundinacea monocultures. Neither E. crusgalli nor P. lapathifolium is likely to improve sedge meadow restoration success. These trends were not sensitive to initial sowing density or elevation above water level. Without methods to suppress P. arundinacea invasions, sedge meadow restorations may often fail. Thorough site preparation to remove P. arundinacea propagule sources before restoration is essential.     

Using a Wetland Bioreactor to Remediate Ground Water Contaminated with Nitrate (mg/L) and Perchlorate (μg/L)

Wetland plants and their rhizospheric microorganisms were used to remove perchlorate from nitrate-contaminated ground water. A wetland bioreactor was constructed with the wetland plants Typha spp., Scirpus spp., and Cyperus spp. These plants provided a habitat and a food source for the indigenous denitrifying microorganisms presumed responsible for the perchlorate and nitrate removal. Ground water contaminated with nitrate (68 mg/L) was collected from a well and injected with concentrations of potassium perchlorate similar to those found in several local wells (50 and 100 μg/L). The water flowed continuously through the wetland bioreactor with hydraulic retention times (HRT) ranging from 0.5 to 400 h. Because microbial denitrification depends, in part, on the nature and amount of carbon available to the microorganisms, four carbon sources (dried leaf matter, dried algae, milk replacement starter, and sodium acetic acid) were evaluated. Analyses for perchlorate

This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.

Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-Eng-18. concentration in ground water were performed using negative electrospray mass spectrometry/mass spectrometry. Of the carbon sources tested, sodium acetic acid was the most efficient at accelerating the nitrate and perchlorate removal rates. The HRT required to remove perchlorate (100 μg/L) to below the detection limit, without carbon source amendment, was 4 d. With the addition of sodium acetic acid (0.26 g/L) the required HRT decreased to 0.5 d. These results suggest that denitrifying microorganisms, supported in a wetland bioreactor amended with a carbon source, remove perchlorate from nitrate contaminated ground water.     

Peat characteristics and groundwater geochemistry of calcareous fens in the Minnesota River Basin, U.S.A.

Calcareous fens in Minnesota are spring-seepage peatlands with adistinctive flora of rare calciphilic species. Peat characteristics andgroundwater geochemistry were determined for six calcareous fens in theMinnesota River Basin to better understand the physical structure andchemical processes associated with stands of rare vegetation. Onset of peataccumulation in three of the fens ranged from about 4,700 to 11,000 ¹⁴C yrs BP and probably resulted from acombination of climate change and local hydrogeologic conditions. Most peatcores had a carbonate-bearing surface zone with greater than 10%carbonates (average 27%, dry wt basis), an underlyingcarbonate-depleted zone with 10% or less carbonates (average4%), and a carbonate-bearing lower zone again with greater than10% carbonates (average 42%). This carbonate zonation washypothesized to result from the effect of water-table level on carbonateequilibria: carbonate precipitation occurs when the water table is above acritical level, and carbonate dissolution occurs when the water table islower. Other processes that changed the major ion concentrations inupwelling groundwater include dilution by rain water, sulfate reduction orsulfide oxidation, and ion adsorption or exchange. Geochemical modelingindicated that average shallow water in the calcareous fens during the studyperiod was groundwater mixed with about 6 to 13% rain water.Carbonate precipitation in the surface zone of calcareous fens could bedecreased by a number of human activities, especially those that lower thewater table. Such changes in shallow water geochemistry could alter thegrowing conditions that apparently sustain rare fen vegetation.     

武汉东湖若干种轮虫休眠卵的形态观察

休眠卵是轮虫在恶劣生态条件下形成的滞育结构。本研究用光学显微镜和扫描电子显微镜对东湖14种轮虫休眠卵形态进行了观察,其中关于尾突臂尾轮虫（Brachionuscaudatus,Barrois＆Daday）、方形臂尾轮虫（Bquadridentatus,hermann）、中型晶囊轮虫（Asplanchnaintermedia,Hudson）、顶生三肢轮虫（Filiniaterminalis,Plate）的休眠卵的形态特征尚未见过报道。这些休眠卵一般卵壳较厚,颜色较深,壳表面有纹饰。不同种轮虫的休眠卵形态、壳饰各不相同,具种的特异性,但在某些轮虫,即使同一种中休眠卵形态有时亦存在较大的差异。     

湿地的国内外研究进展

湿地的国内外研究进展王宪礼李秀珍（中国科学院沈阳应用生态研究所,１１００１５）ＡｄｖａｎｃｅｓｉｎＷｅｔｌａｎｄｓ’Ｒｅｓｅａｒｃｈｅｓ．ＷａｎｇＸｉａｎｌｉ,ＬｉＸｉｕｚｈｅｎ（ＩｎｓｔｉｔｕｔｅｏｆＡｐｐｌｉｅｄＥｃｏｌｏｇｙ,ＣｈｉｎｅｓｅＡ...     

武汉东湖水生植物群落演替的研究

 本文根据1992～1993年调查结果并结合前人研究资料,讨论了东湖水生植物群落30多年来的动态变化及其与富营养化和渔业养殖等因素的关系,提出了东湖水生植物群落的演替系列是从微齿眼子菜阶段→微齿眼子菜+大茨藻+金鱼藻+狐尾藻阶段→微齿眼子菜消失阶段→大茨藻阶段→大茨藻+狐尾藻+苦草阶段。同时,还从物种生理生态、补偿和再生能力、生活史及生殖对策、种间关系等方面探讨了水生植物群落演替的物种替代机制及其演替模式,为湖泊水生植被恢复、人工调控和优化提供理论依据。     

Size-dependent over-winter mortality of young-of-the-year roach, Rutilus rutilus

Over-winter survival of starved and fed young-of-the-year roach from two lakes in central Finland was examined in the laboratory between November 1992 and May 1993. The mortality rate of starving YOY roach (total length 38 ± 2 mm) from small (ca. 0.5 km²), eutrophic Lake Isojärvi was 50%, whilst roach (total length 32 ± 3 mm) from large Lake Päijänne (1106 km²) suffered 42% mortality. Mortality was size-dependent among roach from Lake Isojärvi, smaller individuals being more vulnerable. There was not strict size limit for survival as proposed previously. However, it seems that within populations approximately the same proportion of smallest roach died independent of the absolute lengths of the fish. Mortality of fed roach from both lakes was always < 5%. This good survival indicates indirectly the importance of energy reserves in wintering. Lipid and protein content of fasting roach from lake Isojärvi decreased during the winter. In the group of fasting roach from Lake Päijänne the amount of lipids stored increased between November and March and decreased thereafter. No change in protein content of fasting fish from Lake Päijänne was observed.     

Identifying wetland meadows in Grand Teton National Park using remote sensing and average wetland values

Six spectrally and ecologically distinct montane meadow community types were identified and mapped within Grand Teton National Park by analysis of Indian IRS-1B LISS-II imagery. A distinct to-xeric-hydric gradient among the meadow types was predicted by analysis of the satellite data. Thirty sites (five replicates for each of six meadow typ were selected for intensive field sampling. At each of the 30 sites, meadow vegetation was sampled in 20 m by 20 m square plots for canopy cover of all species. Using wetland indexes (on a scale of 1–5, where obligate wetland species = 1, facultative land = 2, facultative = 3, facultative upland = 4 and upland species = 5), average wetland values were calculated and ranged from 1.88 for A-type meadows and 2.86 for B meadows to 4.40, 4.49, 4.74, and 4.43 for C, D, E and F meadows, respectively. Because average wetland values of A and B meadows were < 3.00, they were determined to be indicative of wetlands. Eight out of ten obligate wetland plants had their greatest cover on A meadows (the wettest of the gradient) and had significant cover differe among meadow types using the non-parametric Kruskal-Wallis test. Average wetland values and plant species cover were used, in conjunction with remotely sensed data, to identify as wetlands 1,258 hectares of A meadows and 1,711 hectares of B meadows in Grand Teton National Park.     

Planning for the recovery of Lake Toolibin,Western Australia

Lake Toolibin, an intermittently flooded freshwater wetland in the southwest of Western Australia, is threatened by salinization due to extensive clearing within its catchment. The lake is a Wetland of International Importance under the Ramsar Convention because of the extensive stands of trees on the lake bed and its significance as a waterbird breeding site. Past research and monitoring have identified the causes of wetland vegetation and water quality decline and this information has been used to design a Recovery Plan for the lake. The plan is currently in the early stages of implementation and includes both short-term engineering measures to reduce salinity within the lake and long-term rehabilitation measures within the catchment. Community involvement in the recovery process is an integral part of the plan and ensures that recovery of the lake remains as the focus for ongoing catchment rehabilitation.