Comparison of recent vegetation and diaspore banks along abiotic gradients in brackish coastal lagoons

Submerged vegetation and diaspore banks were investigated in three shallow brackish lagoons along the German southern Baltic Sea coast. The distribution of vegetation and diaspores was analysed at three depths (0.5, 1.0, 1.5 m) on three transects in each lagoon along salinity and nutrient gradients. Thirteen taxa of submerged vegetation were identified in three lagoons: 8 angiosperms and 5 charophytes. The diaspore analysis yielded 11 taxa of submerged diaspore types: 7 angiosperm taxa and 4 charophyte taxa groups.Salinity and nutrient gradients are the key factors governing the distribution of the vegetation and diaspore banks here. Statistical analysis (SIMPER) of vegetation and diaspore bank show differences in dissimilarities, i.e. Bray-Curtis similarities subtracted from 100, between the lagoon parts and between the lagoons. These differences increased with increasing intensity of the salinity and nutrient gradients. We argue that the diaspore bank reflects the former vegetation gradients shaped primarily by salinity gradients, whereas the present vegetation gradients are more affected by eutrophication. Vegetation surveys and diaspore bank analyses therefore supplement each other, and their combined use provides insight into former as well as recent gradients in the vegetation and the factors governing these gradients.     

Characterization of thermal power-plant fly ash for agronomic purposes and to identify pollution hazards

Ash samples were collected from a dumping site (fly ash) and an electrostatic precipitator (ESP ash) of a 440 MW thermal power plant for characterization. Analysis of ash samples showed that the major matrix elements in fly ash were Si and Al, together with significant percentages of K, Fe, Ca and Mg. Some of the biologically-toxic elements, Ni, Cr, Pb, B and Mo, were also present in substantial amounts. Ash collected directly from electrostatic precipitator (ESP ash) was finer in texture, lower in pH and generally richer in nutrients than the ash collected from dumping sites (fly ash). The saturation moisture percentages of both the ashes were higher, but the bulk density was lower, than the normal cultivated soils. Calcium was the dominant cation of the exchange complex, followed by Mg²⁺, Na⁺ and K⁺. Contents of available sulphur were quite high. Among DTPA extractable micronutrients, only iron was present in significant amounts, but the contents of hazardous constituents were very low. Compositions of watersoluble constituents of both the ashes were substantially affected by water: fly ash ratio and decreased with dilution. The rate of release of sodium was found to be much less than calcium and magnesium.     

Plant uptake and phytotoxicity of boron in Australian fly ashes

Summary French bean (Phaseolus vulgaris cv. Redland Pioneer) and Rhodes grass (Chloris gayana cv. Pioneer) were grown in glasshouse experiments to examine the potential for phytotoxicity of B in a range of Australian fly ashes. In each experiment, the ashes used were either untreated, leached or adjusted to pH 6.5 and subsequently leached.In the first eperiment, the yield and B status of plants grown on five fly ashes mixed (5 and 10% by weight) with an acid-washed sand were measured and, with the exception of one ash, yield differences among ash sources and among ash treatments were attributed to differences in the degree of B toxicity. In a subsequent experiment, a fly ash with properties representative of most Australian ashes was mixed (0, 15, 30, 70 and 100% by weight) with a sandy loam, and the yield and mineral composition of plants grown on these mixtures determined. Although the available water capacity of the soil was substantially increased by fly ash addition, incorporating large proportions of untreated fly ash resulted in poor plant growth primarily due to B toxicity. In both experiments, leaching the ash reduced the potential for B toxicity, whereas adjustment of the pH to 6.5 and subsequent leaching of the fly ash resulted in plants with normal levels of B.There were marked differences in both the tissue levels of B and the extent of B toxicity symptoms between the two species. Rhodes grass appeared to be able to tolerate higher B contents in the growing medium by taking up much less of the element than French bean. The results indicate that phytotoxicity of B would be a major problem in establishing vegetation on ash dams and in the agronomic utilization of unweathered fly ashes in Australia.     

Regime shifts in vegetation composition of Baltic Sea coastal lagoons

Vegetation communities, morphometric and water quality variables were sampled in 62 undisturbed coastal lagoons along a natural land-uplift gradient in the northern Baltic Sea. The lagoons had a morphological inlet threshold reflecting habitat isolation (i.e. the diminished connectedness of the lagoon to the sea) and located in different parts of the archipelago (corresponding to altering wave exposure). We used indirect multivariate methods to find changes in vegetation composition, and axes derived from the analyses were used in correlation and stepwise multiple regression analyses together with environmental variables. Habitat isolation proved to be the strongest predictor for vegetation composition. To identify significant change-points we used a method, which detects regime shifts by accounting for differences in chronological series and gives a regime shift index. Significant shifts in habitat isolation, average depth and total nitrogen were followed by shifts in species variables (i.e. dominant species, cover and species richness) and salinity, total phosphorus and turbidity. Of the species, especially Chara tomentosa showed a shift of high magnitude. Also a shift in wave exposure mirroring position of lagoons in the archipelago structured the species, but this division was seen only for less isolated lagoons. Our results suggest that lagoons are primarily structured by habitat isolation forming two structurally different regimes: one of less isolated lagoons dominated by a diverse array of vascular plants and marine algae of both outer and inner archipelago characters, and one with isolated lagoons dominated by high vegetation cover and dominance of Chara. In addition, vegetation seemed to stabilize water quality in the isolated regime by reducing turbidity and phosphorus, indicating a potential feed-back mechanism and a shift in structuring disturbances from abiotic to biotic factors with habitat isolation.     

Coal fly ash as an amendment to container substrate for Spathiphyllum production

Coal fly ash, possessing alkalinity and containing some essential mineral elements, could be an alternative to lime amendment and a nutrient source of container substrates for ornamental plant growth. This study examined physiochemical properties of three fly ashes collected from Florida, Michigan, and North Carolina and container substrates formulated by incorporating commercial dolomite and the three fly ashes, respectively into a soilless basal substrate. The basal, dolomite- and fly ash-amended substrates were used to grow peace lily (Spathiphyllum Schott 'Ty's Pride'), a popular ornamental foliage plant, in 15-cm diameter containers in a shaded greenhouse. Electrical conductivities and pH of the substrates were monitored monthly. Plant canopy heights and widths, shoot fresh and dry weights were recorded five months after transplanting, and tissue nutrient contents were measured. Three fly ashes and the commercial dolomite were able to raise pH of the basal substrate from 3.8 to about 6.8. Canopy heights and widths as well as shoot fresh and dry weights of plants produced from fly ash-amended substrates were comparable to those produced from dolomite-amended substrate but significantly different from those produced from the basal substrate. On an average, five necrotic leaves appeared from plants produced in the basal substrate; however, less than one necrotic leaf occurred on plants produced in either dolomite- or fly ash-amended substrates. As a result, the quality grade of plants grown in the basal substrate was low, and plants were not marketable. Additionally, electrical conductivities of fly ash-amended substrates were consistently higher during the course of plant growth, suggesting that, in addition to neutralizing pH, the amended fly ashes provide nutrients for peace lily growth, which was confirmed by high nutrient contents in plant shoots. This study demonstrates that the three fly ashes can be alternatives to commercial dolomites used as amendments to soilless substrates for ornamental plant production. Utilization of fly ashes as container substrate amendments should represent a new market for the beneficial use of coal combustion byproducts.     

A recently landlocked brackish-water lagoon of Lake Tanganyika: physical and chemical characteristics,and spatio-temporal distribution of phytoplankton

Monthly measurements of physical and chemical characteristics were made at two localities in the eastern part of a recently landlocked lagoon of Lake Tanganyika. Variables analysed were: temperature, pH, conductivity, sodium, potassium, magnesium, calcium, carbonate, bicarbonate, chloride and sulphate. Large seasonal fluctuations of salinity were recorded (1.68–8.21 g l^–1). The seasonal water input controlled algal seasonality mainly through its effect on salinity and indirectly through its influence on nutrient concentration by dissolution and dilution of the excrements of the numerous cattle and other organic matter. Phytoplankton was mainly composed of Cyanophyta and Euglenophyta. Euglenophyta dominated during the dry periods with high salinity and probably very high nutrient levels, while Cyanophyta preferred moderate salt and nutrient concentrations during the rainy periods. The phytoplanktonic community was composed of a large number of perennial and a reduced quantity of annual organisms.A spatial study of the recently landlocked lagoon revealed an ascending salinity gradient, principally due to a sodium bicarbonate/carbonate enrichment, between locations near the lake and more inland situated stations. These facts point to a lake water supply and a salt concentration by evaporation in the swamps. Proportionally lower magnesium, calcium and potassium values were recorded at high salinities, due to chemical precipitation and biotic factors.A blue-green algal bloom was observed in the eastern water-body (salinity: 4.64 g l^–1); simultaneously an important development of diatoms dominated the western water-body (salinity: 2.18 g l^–1). No significant differences in morphometry, exposure, water temperature or nutrient levels (nitrate, nitrite, ammonia, orthophosphate) were observed. The relatively low salinity and high nutrient concentration in the western water-body probably favoured diatom development during the rainy season. The relatively higher salinity in the eastern water-body during the rainy season was probably responsible for the dominance of blue-green algae through its negative influence on silica concentration and notwithstanding the high inorganic nitrogen concentration.     

Spatiotemporal Variation of Bacterial Community Composition and Possible Controlling Factors in Tropical Shallow Lagoons

Bacterial community composition (BCC) has been extensively related to specific environmental conditions. Tropical coastal lagoons present great temporal and spatial variation in their limnological conditions, which, in turn, should influence the BCC. Here, we sought for the limnological factors that influence, in space and time, the BCC in tropical coastal lagoons (Rio de Janeiro State, Brazil). The Visgueiro lagoon was sampled monthly for 1 year and eight lagoons were sampled once for temporal and spatial analysis, respectively. BCC was evaluated by bacteria-specific PCR-DGGE methods. Great variations were observed in limnological conditions and BCC on both temporal and spatial scales. Changes in the BCC of Visgueiro lagoon throughout the year were best related to salinity and concentrations of NO ₃ ^? , dissolved phosphorus and chlorophyll-a, while changes in BCC between lagoons were best related to salinity and dissolved phosphorus concentration. Salinity has a direct impact on the integrity of the bacterial cell, and it was previously observed that phosphorus is the main limiting nutrient to bacterial growth in these lagoons. Therefore, we conclude that great variations in limnological conditions of coastal lagoons throughout time and space resulted in different BCCs and salinity and nutrient concentration, particularly dissolved phosphorus, are the main limnological factors influencing BCC in these tropical coastal lagoons.     

Species richness of crustacean zooplankton and trophic structure of brackish lagoons in contrasting climate zones: north temperate Denmark and Mediterranean Catalonia (Spain)

We sought to identify environmental factors influencing crustacean zooplankton species richness in brackish lagoons and to elucidate whether crustacean zooplankton species richness and trophic structure of brackish lagoons differ among two regions with contrasting temperatures. We sampled 35 and 42 brackish lagoons (salinity ranging from 0.3 to 55‰) in Mediterranean Catalonia (NE Spain) and northern-temperate Denmark, respectively. No significant differences were found in total crustacean zooplankton species richness or cladoceran richness between the climatic regions. Calanoid richness was higher in Denmark than in Catalonia, while cyclopoid richness was higher in Catalonia. Salinity was the most important variable associated with zooplankton species richness in both regions, richness of total zooplankton species, cladocerans and cyclopoids being negatively related with salinity. In both regions, a shift occurred from dominance of large filter feeding cladoceran species at low salinities to copepods and small cladoceran species at higher salinities. Cladoceran richness increased with increasing total phosphorus, but was not influenced by total nitrogen or chlorophyll-a. Trophic structure in Mediterranean brackish lagoons showed a more pronounced seasonal variation than in north temperate brackish lagoons. Our results imply that the indirect effects of climate warming, such as changes in salinity and hydrology, will have a larger impact on brackish lagoon ecosystems than the increase in temperature per se.     

Fish community structure in lakeshore lagoons on long point,lake Erie,Canada

Synopsis The interaction of fluctuating water level and the Long Point topography is discussed with regard to the formation of lake-shore lagoons and their subsequent invasion by fishes. The species composition of fish communities in these lagoons was determined by 12 collections from lagoons (23 m² to 25 ha) which yielded 33 fish species. The relationship of the number of fish species to lagoon area was lognormal; that is, with increasing lagoon area the number of species rose rapidly at first but soon decreased sharply, probably limited by the number of species capable of surviving in the habitat. The marked effect of area on species number in small lagoons is considered in the context of a hypothetical seasonal pattern of occasional invasion and continuous extinction.A sequence of reproductive guilds was found. In beach lagoons psammophils and lithophils were dominant. In a large vegetated lagoon in the interior phytophils and speleophils were dominant. This sequence was paralleled by an increase in the proportion of guarding and nesting species in the communities. The sequence was disrupted in the small interior lagoons where adaptations for survival were more important than reproductive strategy.     

Effects of Water Level Management on Autumn Staging Waterbird and Macrophyte Diversity in Three Danish Coastal Lagoons

Many Danish wetlands frequently experience algae blooms and oxygen deficiencies because of eutrophication caused by enhanced nitrogen and phosphorous levels. As a consequence, wetland managers have focused on improving water quality, but often without considering the suitability of wetlands for waterbirds. In this study, managers improved water quality in two Danish lagoons by opening a floodgate to the sea. We studied the responses of autumn staging waterbirds and submerged vegetation, to resultant higher water replacement rates and water levels. A third lagoon with no change in management was studied for comparisons. Lagoons with rise in water levels experienced declines in bird species diversity, a decline in benthivore species abundances and an increase in herbivore species abundances. Macrophyte biomass increased but seagrass diversity was low due to high salinity. The lagoon with no changes in management control had high and stable waterbird diversity and bird-days spent was increasing during the study period. Explanations for this were diverse typography and low water levels. Furthermore, the macrophyte community was more diverse due to low salinity. In order to improve both water quality and to increase waterbird diversity in the managed lagoons, we suggest water levels should be managed actively during peak migration in autumn. This could secure more shallow-water areas to waders and create better congruence between appropriate water levels and timing of peak bird migration in autumn. The rest of the year the floodgate should be left open in order to secure a high water quality.     

荒漠植物不同功能群性状特征及其与土壤环境的关系

研究不同功能群植物性状差异及其与土壤环境关系对于充分掌握植物的环境适应策略至关重要。以艾比湖流域为研究区,利用荒漠植物的植物高度、叶片碳、氮、磷、硫、钾、钙、钠、镁含量等9个性状,将高、低土壤水盐环境下的植物划分为5个功能群,分析不同功能群的植物组成、性状差异及其与土壤环境的关系。结果表明：(1)不同土壤水盐环境下,其植物功能群组成不同;其中白刺、胡杨和罗布麻在两个土壤水盐环境下的功能群中均存在。(2)植物的功能性状在不同土壤水盐环境下也发生了适应性的变化。高土壤水盐环境下3个功能群的植物高度、叶片碳、氮、磷和钙含量显著高于低土壤水盐环境功能群(P<0.05);低土壤水盐环境下2个功能群的植物叶片硫、钠和镁含量高于高土壤水盐环境功能群。(3)土壤含水量(SVWC)、电导率(EC)、pH以及土壤磷含量对荒漠植物功能性状影响较大。在高土壤水盐环境下,EC、pH与植物高度,叶片钾、钙含量正相关,与叶片硫含量负相关;在低土壤水盐环境下,SVWC、EC与植物高度呈显著正相关(P<0.05)。研究有助于理解荒漠植物对极端环境的适应对策,为保护荒漠地区生物多样性提供理论依据。     

Evaluation of various agro-wastes for traditional black soap production

The agricultural wastes, cocoa-pod husks, palm-bunch waste, sorghum chaff and groundnut shells, which are normally thrown away have been used in the production of black soap. Unlike other soaps which are made from oils and chemicals, black soap is made from oils and agro-wastes ashes. Chemical analysis indicated that the liquid extract from the ashes of the different agro-wastes used contained various amounts of potassium and sodium compounds. The most common ingredient in the agro-wastes was potassium carbonate. The amount of potassium carbonate was 56.73 +/- 0.16% in cocoa-pod ash, 43.15 +/- 0.13% in palm-bunch ash, 16.65 +/- 0.05% in groundnut shell ash and 12.40 +/- 0.08% in sorghum chaff ash. Soaps made from the agro-wastes ashes had excellent solubility, consistency, cleansing and lathering abilities.     

Ostracods and environmental variability in lagoons and deltas along the north-western Mediterranean coast (Gulf of Lions,France and Ebro delta,Spain)

The aim of this paper is to characterize various lagoon and delta environments through the analysis of ostracod fauna. Various aquatic environments from the Mediterranean coastline of the Gulf of Lions (Languedoc-Roussillon, France) and Ebro delta (Catalonia, Spain) were studied. The sample sites (60) are different in terms of marine and fluvial influence. Environmental parameters (salinity, water depth, sedimentary texture, plant cover) were measured and compiled from available data in order to characterize the biotopes. We interpreted the species distribution as related to the degree of isolation from the sea, the hydrological internal currents and the proximity of river mouths. Moreover, the assemblage composition seems influenced by the lagoon vegetation growth. These data can be used for the palaeoenvironmental reconstructions, particularly in Holocene deltaic context where the mobility of river mouths and the forming and evolution of sand bars and lagoons are recurring issues.     

Initial crop growth in soil collected from a closed animal waste lagoon

In the 21st century, remediation of the soil beneath animal waste lagoons will become an important issue, as they are closed due to environmental regulations or to abandonment. The possibility of growing crops in the soil, which has high concentrations of ammonium-N, has not been studied. The objective of this experiment was to determine if crop species would germinate and grow in lagoon soil. Soil was gathered from a lagoon that had received wastes from swine (Sus scrofa) and beef (Bos taurus) since 1968. Eight crops were grown in greenhouse pots containing the lagoon soil: winter barley (Hordeum vulgare L. 'Weskan'); field corn (Zea mays L., Cargill's hybrid 7997); 'Plainsman' winter rapeseed [Brassica napus L. spp. oleifera (Metzg.) Sinsk. f. biennis]; soybean [Glycine max (L.) Merr. 'KS 4694'); forage sorghum [Sorghum bicolor (L.) Moench 'Norkan']; sunflower (Helianthus annuus L. 'Hysun 354'); and winter wheat (Triticum aestivum L.)--two cultivars: '2137' and 'Turkey.' Plants were grown for 35 days in lagoon soil or an agricultural soil (Haynie very fine sandy loam; coarse-silty, mixed, superactive, calcareous, mesic Mollic Udifluvent) obtained from a field near the closed lagoon. Ammonium-N (average value of 692 mg/kg) was about 70-85 times greater than the average value of 8-10 mg/kg NH4-N in Kansan soils. The lagoon soil was nonsodic and had a salinity ranking of "medium" with an electrical conductivity averaging 2.29 dS/m. The high ammonium-N concentration in the lagoon soil was not inhibitory to emergence and growth. The eight crops grew taller in the lagoon soil than in the agricultural soil. Except for '2137' wheat, dry weight was higher in the lagoon soil than in the agricultural soil. The results showed that the lagoon soil is not detrimental to early growth of eight crops.     

Human impacts and the status of water quality in the Bundala RAMSAR wetland lagoon system in Southern Sri Lanka

The brackish coastal wetlands in the Bundala National Park, the only RAMSAR site of southern Sri Lanka, are an important waterfowl habitat and economic zone. Bundala Lagoon, one of the three key lagoons of the Bundala wetlands, remains largely intact and relatively pristine, but the other two interconnected lagoons, namely, Embilikala and Malala, are impacted by drainage from 25.6 km² of upstream agricultural lands. Seasonal variations of water quality of the three lagoons and the key processes affecting water quality and quantity in these lagoons were studied during three agricultural seasons, to better understand the characteristics of the system. Bundala Lagoon, which was not affected by agriculture, recorded the highest ammonia and total nitrogen concentrations and the lowest phosphorus levels. Higher phosphorus levels in Embilikala Lagoon were related to the upstream agricultural activities with 65% of its total phosphorus measured being reactive phosphorous. Phosphorus additions occurred during the early months of the paddy cultivating seasons. Processes affecting the water quality of the Embilikala-Malala lagoon system included agricultural drainage, livestock additions, and breaching of the sand bar between Malala Lagoon and the sea. The salinity level of the Bundala Lagoon was higher than the others due to the connection to the sea, salt farms in the western part, and less dilution of salt from relatively low surface runoff and rainwater. All three lagoons reported pH levels conducive to most aquatic species. The primary production by phytoplankton in the lagoons of the Bundala wetland was phosphorus limited regarding their ratios of nitrogen to phosphorus. This study provides an overview of the present status of the lagoons of the wetland. Further work is needed to evaluate the impact of the external nutrient and water inputs on the flora and fauna of the lagoon environments. Suitable management practices to ensure the sustainability of the lagoon ecosystem can be derived through this increased understanding.     

Limitations to vegetation establishment and growth in biofiltration swales

Limitations to vegetation establishment and abundance in biofiltration swales (also called biofilters or bioswales), vegetated storm-water facilities intended to improve runoff water quality, was studied through field monitoring and greenhouse experimentation. The various environmental factors influencing vegetation and organic litter abundance was investigated in eight bioswales in western Washington state, including three that were retrofitted. A nested 4×4 factorial greenhouse experiment tested the response of four turfgrass species commonly seeded in bioswales to three inundation regimes plus a control. In the greenhouse experiment and in the field, persistent inundation significantly suppressed germination and growth. Field monitoring further revealed that heavy shade overwhelms all other environmental factors. Where light is adequate, vegetation and organic litter biomass is strongly and inversely related to the proportion of time bioswales are inundated above 2.5-cm depth during the driest time of year (summer). For most bioswales, flow velocity and hydraulic loading during storm events appear too large to permit sedimentation of silt and clay particles, even with dense vegetation and abundant organic litter. Thus, herbaceous vegetation abundance may not provide a good indication of bioswale treatment performance, and actual storm-water treatment may be much poorer than is generally anticipated from previous studies.     

Vegetation indicators of salinity in northern Queensland

Abstract The possibility that plants could serve as indicators of underlying soil salinity in northern Queensland, Australia, was investigated using 2197 site observations recorded during a land resources inventory of the Dalrymple Shire. The area surveyed intersects three biogeographical regions: the desert uplands, the Einasleigh uplands and the northern brigalow belt. The three dominant plant species in the lower, middle, and upper vegetation strata were recorded, along with laboratory measurements of electrical conductivity down each soil profile. Correspondence analysis, generalized additive models and clustering were used to investigate the relationship between plant occurrence, climatic and edaphic factors. The results of these statistical analyses strongly suggest a relationship between salinity and brigalow plant communities. A generalized additive model to predict soil salinity from environmental variables including vegetation data is presented.     

Nest site preferences of the Woodlark (Lullula arborea) and its association with artificial nest predation

The Woodlark is an insectivorous bird, which is listed as a priority species in Switzerland. In Valais, a stronghold of this species in the country, the birds breed in intensively managed vineyards and show a preference for parcels with ground vegetation during territory establishment. As a ground-breeder, the species is highly vulnerable to nest predation by avian and mammal predators. The aims of our study were firstly to investigate nest site preferences of the woodlark within vineyards and secondly to compare the predation risk of artificial nests dependent of ground vegetation structure. Our results point out that the Woodlark prefers patches of tall and dense ground cover within vegetated vineyard parcels and avoids parcels that have been treated with herbicides. In a follow-up experiment we conducted a study comparing the predation rate of artificial nests between bare parcels (<20% vegetated area) and vegetated parcels (>40% vegetated area). Artificial nests equipped with one quail egg were distributed pairwise between two adjacent parcels that fulfilled the upper criteria and were monitored by trail cameras during 10–12 days. Predation rate was generally low (4 predation events) and only occurred in bare parcels. These data indicate that conspicuousness of avian nests may be decreased in vegetated parcels and that the amount of vegetation can lower the predation risk on ground breeding birds - another indication for the importance of ground vegetation for a successful conservation of the endangered Woodlark in Swiss vineyards.     

海涂区不同植被类型下土壤盐渍剖面及其电磁感应响应特征

针对滨海滩涂区植被类型与土壤盐渍化间的内在联系,以黄河三角洲典型海涂区为研究对象,结合电磁感应仪EM38与田间采样,分析了不同植被类型下土壤盐渍剖面分布特征,并对各植被类型下土壤盐渍剖面的电磁感应响应特征进行了比较.结果表明：研究区土壤盐分具有较强的表聚性与变异强度,水平磁感式表观电导率(EM_h)对浅层土壤盐分响应较好,而垂直磁感式表观电导率(EM_v)对深层土壤盐分的响应优于EM_h;土壤盐渍剖面分为表聚型、底聚型和平均型3类,表聚型盐渍剖面主要为光板地和盐蒿地,底聚型的地表植被以棉花为主,平均型主要为杂草,且土壤盐分表聚强度为光板地>盐蒿地>杂草地>棉花地;随着植被类型由棉花—杂草—盐蒿—光板地变化,各剖面的EM_v/EM_h值逐渐降低.经非参数检验,植被类型与电磁感应响应特征具有显著相关性,且不同植被类型的EM_v/EM_h分布特征差异明显.     

几种粉煤灰对磷素吸附与解吸特性的研究

通过吸附解吸和培养试验, 研究了几种粉煤灰对磷素吸附与解吸特性.结果表明,粉煤灰的全磷含量和有效磷含量分别为0.545～4.540 g·kg^-1和19.55～163.0 mg·kg^-1,显著高于土壤,粉煤灰对磷吸附量随着加入溶液磷浓度的增加而增加,但其吸附率随着加入溶液磷浓度的增加而减少;粉煤灰的吸磷率比土壤高,但其解吸率低.这主要是由于粉煤灰比土壤存在更多的磷吸附位点且结合能大,不易解吸.Langmuir方程、Freundlich方程和Temkin方程都能很好地拟合粉煤灰对磷吸附,其中Langmuir方程的MBC、Freundlich方程的a和Temkin方程的k2都可以表征粉煤灰对磷吸附能力, MBC、a和k2值越大,则吸磷能力越强.不同来源的粉煤灰的MBC、a和k2值不同,其大小顺序为：湘潭电厂(5 167.7,4 056.2,831.5)>岳阳纸厂(1 650.7,2 803.4,711.9)>华能电厂(303.0,1 677.6,368.7)>株洲电厂(76.2,464.2, 211.0) > 洞庭氮肥厂(34.7,413.48,213.8).粉煤灰对磷吸附固定作用随粉煤灰含水量的增加有增大的趋势.粉煤灰对磷吸附主要是专性吸附和化学沉淀反应,所以在施用粉煤灰改良土壤或利用粉煤灰制造复混肥时,须考虑粉煤灰对磷的固定作用及粉煤灰含水量的影响.