Nutrient Cycling and Retention Along a Littoral Gradient in a Dutch Shallow Lake in Relation to Water Level Regime

Littoral zones are characterized by gradients in depth and vegetation biomass, influencing nutrient retention capacity. A field experiment was conducted in a Phragmites australis dominated littoral zone to investigate nutrient retention and its effect on surface water quality. Measurements were done in mesocosms where water levels could be manipulated. Nutrient status was investigated along a gradient perpendicular to the shore during two growing seasons, one with a stable water level and one with a gradually decreasing water level. Nutrient concentrations in sediment, soil pore water and surface water were significantly lower in the vegetated than in the unvegetated zone. The negative correlations of nutrients in sediment and water, with nutrient contents of the vegetation suggest a direct effect of the vegetation. Nutrient uptake and biomass of the vegetation was higher in continuously flooded soils than in seasonally emerging sediments higher along the littoral gradient, probably due to the increased salinity in drained zones. Denitrification rate was highest in the unvegetated zone and was positively related to water level. Flooded littoral zones did result in a higher nutrient retention than drained zones. On small scale, for an optimal nutrient retention a fluctuating regime is not necessarily better suited than a stable water level, but on a larger scale it can substantially increase the width of the vegetated zone. It is important to optimize conditions for helophyte growth since the positive effect of vegetation on nutrient retention, at least at local scale, has been demonstrated in this study.     

坡度对坡面土壤矿质氮素水蚀流失负荷的影响

坡度是影响坡面水土流失和土壤养分流失过程的重要因素。室内模拟降雨试验表明,当坡长一定时,不仅土壤侵蚀量存在一个“侵蚀临界坡度”,土壤矿质氮流失量随坡度变化也存在一个“养分流失临界坡度”。试验测定这2个临界坡度均在15°～20°之间。土壤矿质氮地表流失以随地表径流流失为主,约占总流失量的99%。坡面矿质氮总流失量的96%为硝态氮,硝态氮对径流中矿质氮总量的贡献率明显高于在侵蚀泥沙中的贡献率。采取一定的截流措施是控制坡面矿质氮流失的关键。     

黄土丘陵区植物功能性状沿气候梯度的变化规律

选取黄土丘陵区延河流域147个物种,对10个与植物形态、生理相关的叶片和细根功能性状(叶大小、叶长宽比、叶厚度、叶干重、比叶面积、叶组织密度、叶氮含量、细根比根长、细根组织密度和细根氮含量)进行了测定,并对功能性状与气候因子的关系进行了分析。结果表明:(1)水热条件是影响研究区植物功能性状的重要因子,其中降雨为主导因子。物种水平上,植物功能性状随着环境的变化而变化,如叶氮含量随着温度指标(最冷月均温、生长季均温、年均温、最热月均温、温度季节变化的增加而增加;(2)不同生长型功能性状在环境梯度下存在差异,表现为草本植物相对木本植物有更小的叶组织密度以及更大的叶面积、比叶面积、叶片氮含量、根氮含量和比根长,表明不同生活型植物对环境的适应能力明显不同;(3)不同类群植物对环境条件变化的响应不同,表现为适应方式的分异和趋同。该结果为探究黄土高原植物对环境的适应机制提供理论依据。     

东北地区不同纬度梯度农田土壤Olsen-P的分布特征

本文研究了中国东北地区不同纬度梯度农田土壤Olsen-P在0～100cm剖面中的分布特征。结果表明,除公主岭和大石桥外,其他各点土壤Olsen-P含量在0～20cm土层较高,20～40cm土层迅速下降,40～100cm各土层又逐渐升高,但底层要远低于表层。不同纬度梯度下各点0～20cm土层Olsen-P含量为暗棕壤>黑土>棕壤,高纬度地点Olsen-P含量具有高于低纬度地点的趋势;20～100cm各土层Olsen-P含量总体表现为黑土和暗棕壤相对较高,棕壤区偏低,没有明显的纬度分异现象。施肥等农田管理措施对0～20cm土壤Olsen-P含量有明显影响,其他土层Olsen-P含量可能主要受磷素运移特点和成土母质等因素影响。     

GIS Analysis of Surface Water Chemistry Susceptibility and Response to Industrial Air Pollution in the Kola Peninsula,Northern Russia

The Kola Peninsula (Figure 1) is the most industrially developed and urbanized region in the Russian North. The main pollution sources are the large smelters Severonickel and Pechenganickel, which are responsible for > 80 % of SO2 emission and nearly 100 % of the Ni and Cu emission in the region. The heterogeneous structure of the hydrologic network and geochemistry across the region cause natural variability in water chemistry. Due to moist and cool climate, large territories on the Kola are sensitive to acid precipitation, but around the smelters, geological peculiarities, erosion and alkaline dust emissions increase buffering capacity of waters to acidification. Lake and river monitoring implemented from 1989-1993 by the laboratory of water ecosystems, Institute of Northern Ecology Problems was a basis for GIS-analysis (ARC/VIEW-2.1) of the major constituents of water chemistry attributed to anthropogenic load in the region. After correction for sea salt, acid-neutralizing capacity (ANC) of waters was calculated. The highest concentrations of anthropogenic non-sea sulfates were confined to the districts with high cation concentrations (Na+ + K+ + Ca2+ + Mg2+) that reduced negative effects. The most vulnerable regions were found in the northern tundra and high mountain tundra.     

Reduced-Form Modelling of Surface Water and Soil Chemistry for the Tracking and Analysis Framework

A reduced-from modelling approach is used to predict soil and lake acidification as part of an integrated assessment of acid deposition effects and control strategies. The reduced-form model is based upon the mechanistic, lumped parameter watershed chemistry model, MAGIC (Model of Acidification of Groundwater in Catchments). Recent improvements to MAGIC are described, and its reduced-form representation in the Tracking and Analysis Framework (TAF), an integrated assessment model for decision and uncertainty analysis, is presented. Reduced-form models are developed for lake acid neutralising capacity (ANC), calcium, pH, and aluminium; and for soil base saturation. The model for lake ANC incorporates long-term depletion of the watershed acid neutralisation fraction, as is predicted to occur with MAGIC. In test calibrations for 33 representative watersheds in the Adirondacks, the resulting reduced-form model provides a close approximation to MAGIC, with average root mean square errors of 0.79 μeq l^-1 for ANC, 1.09 μeq l^-1 for calcium, 0.16 for pH, 2.52 μeq l^-1 for aluminium, and 0.09% for soil base saturation. In addition, improved fish viability models are incorporated in the integrated assessment model, and predictions are demonstrated for a future deposition reduction scenario for the Adirondack region.     

Sulphate Mobilization and Pore Water Chemistry in Relation to Groundwater Hydrology and Summer Drought in two Conifer Swamps on the Canadian Shield

Variations in sulphate (SO₄ ^2-) concentration of porewater and net SO₄ ^2- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO₄ ^2- mobilization and water level elevation relative to the peat surface, explaining variation in SO₄ ^2- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO₄ ^2- mobilization (10–70 mg SO₄ ^2- m^-2 d^-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO₄ ^2- concentrations in the surface water and porewater (30–50 mg L^-1), and elevated SO₄ ^2- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO₄ ^2- mobilization and concentrations of SO₄ ^2- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO₄ ^2- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO₄ ^2- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.     

沈阳南部沿城乡梯度土壤铅时空分布研究

对沈阳南部沿城乡梯度土壤铅含量的分布特征进行了研究。结果表明,全量Pb沿城乡梯度显著降低,但不同土层之间无显著差异。有效态Pb含量沿城乡梯度具有显著降低,并且在城市土壤中呈现较明显的季节性变化。另外,土壤有效态Pb含量在夏季郊区样品和秋季城市样品的层次之间也有显著变化。相关性分析表明,土壤理化性质如土壤质地、pH和CEC对全量及有效态Pb含量产生了一定影响,而人为等因素是影响土壤全量及有效态重金属的主要因素。     

水分对梯度法估算土壤表面CO_2扩散通量的影响

土壤水分是土壤CO2产生和传输的主要控制因子,对其进行研究可以更好的理解土壤水分对土壤碳通量的影响。梯度法是估算土壤CO2扩散通量的一种常见方法,该方法利用菲克第一定律计算土壤CO2扩散通量,其关键参数是气体扩散系数(DP)和CO2浓度梯度。本实验用放置在恒温室内的土柱研究土壤水分变化对梯度方法估算土壤表面CO2扩散通量的影响,利用Millington-Quirk模型对气体扩散率进行模拟。结果表明,土壤CO2浓度随着土壤深度的增加而增加,15 cm处的土壤CO2浓度平均值(1991.8μmol mol-1)明显大于5 cm处土壤CO2浓度平均值(1495.1μmol mol-1),土壤水分与两层土壤CO2浓度变化趋势具有一致性。在土壤温度保持相对稳定的情况下,CO2通量随体积含水量的变化而变化,在干燥或含水量很高的条件下土壤CO2通量较低,接近田间持水量时CO2通量最大;在大多数情况下,梯度法和动态气室法测得的土壤碳通量具有较好的一致性。     

Differences in the Rhizosphere Microbial Activity and Community Composition of Commelina communis along a Copper Contamination Gradient

We studied the effects of copper (Cu) phytoremediation on microbial community composition under laboratory conditions. A Cu accumulator, Commelina communis, was grown on a soil containing different gradients of Cu. Results showed that the biomass of C. communis grown with Cu differed from that of the control. Concentrations of Cu in the shoots of C. communis were 73.6, 160.9, and 319.1 mg kg^?1 under 200, 500, and 1000 mg kg^?1 Cu treatments, respectively. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprint analysis revealed that additions of Cu decreased the number of bands in the soil with C. communis or without plants. The principal component analysis explained 52.7% of the variance for the different rhizospheres of soil and Cu treatments in the soil samples. These results indicated significant effects on soil bacteria activity and community composition in the rhizosphere of C. communis and provided a basis for further studies of metal-accumulator plant effects on soil microorganisms.     

Soil Respiration Characteristics in Three Shrublands along an Elevation Gradient in a Semiarid Loess Plateau Mountain Area

Shrub is one of the major vegetation types distributed mostly in the mountainous area in China, and its vegetation carbon storage is approximately one-third of both forests and grasslands. It is essential to investigate how soil temperature (T_s) and soil water content (W_s) affect soil respiration (R_s) in this ecosystem. The purpose of this study was to understand the correlations of R_s with T_s, W_s, and other factors in the shrubs. In the current study, R_s was characterized in three shrublands (hereafter, shrub 1, shrub 2, and shrub 3, respectively) located in different elevations over a 4-year period at a biweekly interval in the eastern Loess Plateau (Shanxi province) of China. Our results showed that the trend of seasonal change of R_s was controlled mainly by T_s and W_s. The measured mean R_s over 4 years was 3.64 ± 2.83 (mean ± S.D.), 2.69 ± 2.05, and 4.41 ± 3.28 μmol carbon dioxide (CO₂) m^?2 s^?1 for shrubs 1, 2, and 3, respectively, exhibiting an increase trend with elevation increment. Over the season, R_s illustrated a significant change depending on the variation of T_s and W_s, with larger values appearing in summer when both T_s and W_s were high, and smaller values in winter or in summer whenever W_s was low. An exponential model (R_s = a e ^bTs) fitted well the relation between R_s and T_s for shrub 3, whereas linear (R_s = a W_s + b) and power (R_s = a W_s ^b) models of R_s to W_s fitted well for shrub 1. This indicated that at a lower elevation, W_s had a greater effect on R_s than that at a higher elevation. The reverse trend was true between R_s and T_s, i.e., at a higher elevation T_s had a greater effect on R_s than that at a lower elevation. The calculated Q₁₀ values of 1.61, 3.03, and 3.73 for shrubs 1, 2, and 3 increased to 2.25, 3.63, and 4.07, respectively (when the data in low W_s conditions were excluded from the analysis), showing that Q₁₀ increased with elevation increment. Furthermore, three two-variable models, one linear (R_s = a (T_s W_s) + b), and two nonlinear (R_s = a T_s ^b W_s ^c and R_s = a e^bTs W_s ^c), were also well developed to predict the dependency of R_s on both T_s and W_s. Our research results might have important implications for the estimation of soil carbon emissions of the shrublands in this region.     

Leaf Mineral Composition of Olive Varieties and Their Relation to Yield and Adaptation Ability

The amount of yield and adaptation of a cultivar to a new environment is strongly related to nutrient uptake ability. The aim of this study was to compare nutrient uptake ability of 21 local and/or standard olive varieties grown under Mediterranean climatic conditions. Elemental compositions of olive leaves were determined for two consecutive years. The highest yields were obtained from ‘Gemlik’, ‘Manzanilla’, ‘Memecik’, and ‘Hojiblanca’ varieties. Nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), and manganese (Mn) content of leaves were comparatively higher in the high-yielding year (2004) whereas iron (Fe) and copper (Cu) contents were lower. Nutrient uptake ability and usage efficiency of olive varieties were different. Mineral composition of leaves was variety dependent and different groups of varieties showed higher leaf concentration for each element. Therefore, it can be concluded that the variation in the nutrient uptake ability may be used as a criterion for adaptation of a variety to a new ecological environment.     

Evolution of Chemistry along the Bagmati Drainage Network in Kathmandu Valley

Two fungal strains producing ligninolytic enzymes and having the potential to decolorize distillery effluent were isolated from the soil of a distillery effluent contaminated site. DNA was isolated from the pure cultures of these fungi and polymerase chain reaction (PCR) amplification of their internal transcribed spacer (ITS) region of nuclear ribosomal DNA was carried out. Further, the DNA was sequenced and the comparison of generated sequence with database led to their identification as Penicillium pinophilum TERI DB1 and Alternaria gaisen TERI DB6 respectively. These two isolates along with one isolate of Pleurotus florida EM 1303 were assessed for their ligninolytic enzyme activity in culture filtrate as well as after solid state fermentation on two substrates wheat straw and corncob powder. Ergosterol was measured to assess the growth of fungi on solid media. Both P. pinophilum TERI DB1 and A. gaisen TERI DB6 were found to produce laccase, manganese-dependent peroxidases (MnP) and lignin peroxidases (LiP). The immobilized fungal biomass was then used for decolorization of the post biomethanated wastewater from the distillery. Reduction in color up to the magnitude of 86, 50 and 47% was observed with P. florida, P. pinophilum and A. gaisen respectively.     

Formation of a Groundwater Table by Trench Irrigation and Evapotranspiration in a Drained Peatland

To evaluate the coexistence of agricultural managements and wetland ecosystem conservation, the Bibai mire, an ombrotrophic mire in Hokkaido, Japan, was selected as an experimental site that had been affected by neighboring agricultural managements. Since the lowering of the level of the groundwater table in the peripheral area of the mire had threatened indigenous vegetations, keeping the groundwater table shallow by trench irrigation seemed to be an effective measure to recover the original vegetation. The objective of the present study was to quantify the amount of water and the effective area of trench irrigation required in a bamboo-invading area in a pristine mire. We constructed a trench 28 m long and irrigated at the rate of 2.22 m³ d⁻¹ in a bamboo-invading area in the mire. And to analyze the hydro-meteorological conditions under the trench irrigation, we measured the saturated hydraulic conductivity of the peat layer (3.8 × 10⁻³ cm s⁻¹), the evapotranspiration rate (2.80 mm d⁻¹), the depth of the non-irrigated groundwater table (0.15 m) and the surface gradient (0.00493). In addition, using the mass conservation equation and Darcy's law, we derived a steady state model of the level of the groundwater table formed by trench irrigation, which required the five parameters mentioned above. The irrigated water spread over a distance of only about 15 m to both sides of the trench. The model also estimated that the distance for the irrigated area was 14.6 m and we concluded that the irrigated area was limited within a distance of 20 m distances to both sides of the trench and that the irrigation rate per unit trench length did not exceed 0.12 m² d⁻¹ for realistic values of the evapotranspiration rate and the saturated hydraulic conductivity in peatland.     

Soil Water Chemistry and Revegetation of a Limed Clearcut in a Nitrogen Saturated Forest

A clearcut stand of Pinus sylvestris in Flanders (Belgium) was limed with 3 ton/ha dolomite and reforested with Acer pseudoplatanus and Fagus sylvatica. Soil water monitoring revealed an overall decrease of ion concentrations and an annual peak in September due to seasonal nitrification. Liming reduced concentrations of NO₃ ^- and Al³⁺ and raised concentrations of K⁺ and Mg²⁺ and the molar ratio of (Ca+Mg)/Al. Liming also stimulated release of SO₄ ^2-, which prevented a rise of pH, except during nitrification peaks. Liming had no effect on height increment of Fagus but stimulated Acer, which suffered from severe deficiencies of calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) without treatment. Nitrogen (N) was not growth-limiting for Fagus or Acer and liming had no effect on N concentrations in leaves of both species. Liming had a strong impact on ground vegetation. Nutrient-demanding species expanded while species that tolerate nutrient-poor conditions decreased. It is argued that changes in ground vegetation had a greater impact on reduction of NO₃ ^- concentration in soil water than increased tree growth.     

Crustacean Communities in Canada and Norway: Comparison of Species along A pH Gradient

Increased pH in acid lakes changes the crustacean fauna from communities dominated by acid-tolerant species to communities dominated by more acid-sensitive species. Studies from Canada (Killarney) and southeastern Norway (Østfold county) have demonstrated that planktonic and littoral crustaceans can be used as indicators of such recoveries. In both places the cladocerans Alona rustica and Acantholeberis curvirostris were found in acidic lakes, whereas Alona costata and the copepod Eucyclops macrurus were found in near neutral lakes. The calanoids Diaptomus minutus in North America and Eudiaptomus gracilis in Europe, both dominate in acidic water, and may ecologically be equivalent species. Sometimes the same species occur at different pH in the two continents. Bosmina longirostris and Alonella excisa may serve as examples, but a pertinent question is whether or not they are really the same species.     

Reacidification Effects on Water Chemistry and Plankton in a Limed Lake in Sweden

Water chemistry and plankton has been monitored in three Lakes in Tyresta National park SE of Stockholm since 1977. Liming operations started in Lake Långsjön and Lake Trehörningen in 1978 and were repeated every 3–5 years, while Lake Årsjön is an unlimed reference Lake. During 1991–1999, the annual pH median in Lake Långsjön and Lake Årsjön ranged between 6.6–7.1 and 5.2–5.8, respectively, and the composition of phyto- and zooplankton in these lakes did not change markedly. After a final treatment in 1991, the liming of Lake Trehörningen was terminated intentionally. As a result, pH decreased from an annual median 7.1 in 1991, to 6.1 in 1999 (5.8 in 1998). Total organic carbon (TOC) did not change markedly during this period, while the levels of calcium decreased. Metals, known to be influenced by acidification, especially cadmium, manganese and aluminium (Al), increased. The labile-inorganic forms of Al also reached higher levels, especially in 1998. Following the decreasing pH, the total number of phytoplankton taxa decreased by ca 40%. Among zooplankton, the cladocerans Holopedium gibberum, Diaphanosoma brachyurum and Daphnia longispina, common during the limed period, became rare.     

Predicting Phytoplankton Growth and Dynamics in Relation to Physico-chemical Characteristics of Water Body

Water, Air, & Soil Pollution - Cryptosporidium parvum oocysts may reach soil through direct deposition of human or animal fecal material, irrigation with raw wastewater or untreated effluents,...     

Crown Condition and Needle Chemistry of Norway Spruce in Relation to Critical Loads of Acidity in South-East Norway

This study shows that it is questionable if critical load modelling can contribute in the search for harmful effects of acid deposition on forest health at present. Critical loads forS and N deposition were calculated using the MAGIC and PROFILE models for more than 100 monitoring plots in Norway spruce forestin south-east Norway. The two models gave different results, likely due to differences in the models, including differences in the time spans applied. The PROFILE model gave considerably more plots with exceedance than the MAGIC model.At plots where the CL was exceeded, calcium/aluminium (Ca/Al) ratios in the soil solutions were low. However, very few of theseplots had possible harmful values of the Ca/Al-ratio. More than 50 yr seems in most cases to be needed to bring Ca/Al ratios below 1.0. Present deposition was better correlated with measured forest condition variables such as crown condition and needle chemistry,than with modelled exceedance according to any of the two methods. The deposition of S and N was weakly, negatively correlated to foliar concentrations of P and Ca, and positivelyto foliar N concentrations and crown density.