Long-term studies (1871–2000) on acidification and recovery of lakes in the Bohemian Forest (central Europe)

This paper evaluates long-term changes in the atmospheric depositions of S and N compounds, lake water quality, and biodiversity at eight glacial lakes in the Bohemian Forest over the past 130 years. This time interval covers (i) the ‘background’ pre-acidification status of the lakes, (ii) a period of changes in the communities that can be partly explained by introduction of fish, (iii) a period of strong lake acidification with its adverse impacts on the communities, (iv) the lake reversal from acidity, which includes the recent status of the lakes. The lake water chemistry has followed—with a characteristic hysteresis—both the sharp increase and decline in the deposition trends of strong anions. Remarkable changes in biota have mirrored the changing water quality. Fish became extinct and most species of zooplankton (Crustacea) and benthos (Ephemeroptera and Plecoptera) retreated due to the lake water acidification. Independent of ongoing chemical reversal, microorganisms remain dominant in the recent plankton biomass as well as in controlling the pelagic food webs. The first signs of the forthcoming biological recovery have already been evidenced in some lakes, such as the population of Ceriodaphnia quadrangula (Cladocera) returning into the pelagial of one lake or the increase in both phytoplankton biomass and rotifer numbers in another lake.     

20th century acidification and warming as recorded in two alpine lakes in the Tatra Mountains (South Poland, Europe)

Sediment profiles of two alpine lakes located in the Tatra Mountains, the Toporowy Staw Ni?ni (TSN) and the Zielony Staw G?sienicowy (ZSG), were studied for their chronology, lithology, diatom and cladoceran remains. The sediment sequences, 50 cm long from TSN and 30 cm long from ZSG, were deposited during the last 1000 and 300 years, respectively. Vertical changes in lithology, diatom and Cladocera allow the reconstruction of three periods in the lakes' evolution: mild climatic conditions during Medieval Warm Period (MWP, only in TSN), severe conditions between the end of 14th and 19th centuries, identified as the Little Ice Age (LIA), and 20th century warming. The LIA was recorded in the sediments of both lakes in the form of intensified erosion and lower lake ecosystem productivity, as indicated by organic matter lower content, changes in diatom species composition, and decline in Daphnia.The 20th century was a time of acidification in both lakes. The scale of acidification was assessed based on the decline in diatom-inferred pH (DI-pH). DI-pH dropped by 1.2 pH units during the last century in TSN and by 0.4 pH unit in ZSG. The decline of DI-pH was noted in both lakes, but its intensity was clearly higher in TSN due to the lower acid neutralisation capacity (ANC) of this lake. The lower pH during the final decades of the 20th century was lethal to some water organisms while attracting others, such as Daphnia. The Daphnia population increased after the pH drop, probably due to the high food flexibility of this genus. A similar increase was not observed in ZSG, where planktonivorous fishes were introduced in the 1940s, which effectively limited the crustacean plankton density.     

Long-term phosphorus budgets and an examination of a steady-state mass balance model for central Ontario lakes

The objective of this study was to evaluate, modify if necessary, and calibrate a mass balance steady-state total phosphorus (TP) model for use in the Precambrian Shield area of Ontario. Hydrologic data, TP mass balances and lake concentrations data were collected between June 1978 and May 1992 from seven oligotrophic and oligomesotrophic lakes located on the Precambrian Shield in central Ontario. Two of the lakes (Dickie and Harp) had substantial shoreline development; four lakes had alkalinities <25 μ eql⁻¹. The gross settling or loss coefficient, v, was underestimated when internal load was ignored. Long-term mean v ranged about three-fold, from 4.7 m yr⁻¹ in Plastic Lake to 13.7 m yr⁻¹ in Dickie Lake with an average for six lakes of 7.9 m yr⁻¹. The exception was Harp Lake where v was 23.2 m yr⁻¹. The difference in v between heavily developed Dickie and Harp Lakes may have been due to the unusually thick glacial tills in the Harp catchment and their likely ability to retain at least some of the TP from septic effluent. The current inability to predict septic TP retention rates by soils/tills, the highly variable nature of soils/tills, and the decades required to reach equilibrium after installation leave environmental managers with little choice but to apply the “precautionary principle” to ensure adequate protection of inland recreational waters and assume that soils do not retain septic TP. There was no evidence that enhanced sedimentation of TP (“oligotrophication”) occurred in any of the three most acidic lakes. In fact, losses via sedimentation were lowest in these lakes. Average retention, R ((input-output)/input) of TP during the ice-free months of May to November was much higher than average R in winter (December–April) in all lakes. Lack of wind-induced mixing, low biological activity and thermal stratification caused by ice cover make it more likely that stream loads are discharged directly from lakes during winter. Seasonal variation in retention suggests that R and v should be higher in warmer climatic zones. There may be no globally valid v, although the data presented here suggest that a regionally applicable estimate of v may be appropriate. The model should only be calibrated with a long-term data set and should be only used to predict long-term, average responses to changes in average TP loading.     

Semi-natural Forested Landscape under a Bark Beetle Outbreak: A case study of the Bohemian Forest (Czech Republic)

Long-term and lasting human interference in forest ecosystems in the Bohemian Forest has resulted in the loss of some equilibrium mechanisms and hence increased susceptibility to ecological disturbances. Two methods for estimating bark beetle outbreaks in spruce forests are reported: an assessment of the susceptibility of individual trees to attack according to crown structure characteristics; and the use of remotely sensed data and image processing techniques to quantify changes in forest cover. The results document a significant increase in the area of highly damaged and dead forest classes, from 1% in 1987 to 16% in 1998, and a decrease in the area of healthy and moderately damaged spruce classes from 71% in 1987 to 52% in 1998. A possible approach to managing mountain Norway spruce ecosystems invaded by bark beetle in the Bohemian Forest is proposed.     

Semi-natural Forested Landscape under a Bark Beetle Outbreak: a case study of the Bohemian Forest (Czech Republic)

Long-term and lasting human interference in forest ecosystems in the Bohemian Forest has resulted in the loss of some equilibrium mechanisms and hence increased susceptibility to ecological disturbances. Two methods for estimating bark beetle outbreaks in spruce forests are reported: an assessment of the susceptibility of individual trees to attack according to crown structure characteristics; and the use of remotely sensed data and image processing techniques to quantify changes in forest cover. The results document a significant increase in the area of highly damaged and dead forest classes, from 1% in 1987 to 16% in 1998, and a decrease in the area of healthy and moderately damaged spruce classes from 71% in 1987 to 52% in 1998. A possible approach to managing mountain Norway spruce ecosystems invaded by bark beetle in the Bohemian Forest is proposed.     

Trends of phosphorus,nitrogen and chlorophyll a concentrations in Finnish rivers and lakes in 1975-2000

During recent decades the amounts of nutrients discharged to Finnish surface waters have markedly decreased. This has been achieved by considerable investments in water protection, which were made mainly to improve municipal and industrial wastewater purification. We investigated whether these water protection measures have decreased phosphorus and nitrogen concentrations in Finnish rivers and lakes. In addition, possible trends in chlorophyll a concentrations in lakes were studied. The data consisted of a total of over 68000 monitoring results of 22 rivers and 173 lakes (or sub-basins of lakes) with different types of catchment areas. The study period covered the years 1975-2000 and the non-parametric Kendall Tau b and Seasonal Kendall tests were applied for detecting trends. Decreasing nutrient concentration trends were typical in many lakes and rivers earlier polluted by municipal and industrial wastewaters. Increasing nutrient concentration trends were common in smaller rivers and lakes receiving diffuse loading from agriculture. The results show that the investments directed towards wastewater purification have effectively improved the quality of Finnish inland waters. However, no clear effects of decreasing non-point loading were found. Thus, more effective measures should be directed towards decreasing non-point source loading.     

2000—2020年国内外乡村景观研究热点

乡村是人居环境重要的组成部分,乡村景观是兼具多重价值的复合景观系统。“美丽乡村”与“乡村振兴”政策的推动与实施,对乡村景观的研究与建设提出了更高的要求。以Web of Science(WoS)核心合集数据库和中国知网(CNKI)为数据源,基于CiteSpace文献计量分析软件对2000—2020年国内外乡村景观研究热点进行分析。结果表明,国外乡村景观研究热点主要包括乡村景观生态系统服务、乡村景观评价、乡村景观管理与保护、乡村景观多样性,国内研究热点主要包括乡村景观规划设计、乡村景观政策、乡村旅游景观、乡村景观评价与保护。分析国内外乡村景观的研究背景及驱动因素,对比两者在研究视角、理论与方法3个方面的差异,为探究乡村景观未来可能的研究方向提供了基础,提出国内的乡村景观研究未来应持续关注乡村景观多种功能和价值,健全评价与保护机制,完善理论与方法框架。     

Quantifying the effects of forestry practices on the recovery of upland streams and lochs from acidification

Trends in long-term chemistry data are presented for 37 acidified upland streams and lochs, located in four areas (A, B, C and D) across Scotland, to provide a comparison between recovery rates of moorland catchments and forest catchments at different stages of the management cycle. For all sites, non-marine sulfate (nm-SO(4)) showed a significant decline in annual median concentrations, the greatest decline being in streams draining felled catchments, which showed a 50% greater decline than catchments with moorland or young, aggrading forests. A similar pattern was found for chloride (Cl) concentrations in Area C, which reflected the reduced interception of sea-salt aerosols following clearfelling. However, high elevation moorland sites in Area D also revealed significant declines in Cl while trends in aggrading forest sites in this area were insignificant. Alkalinity (ALK) and pH increased more at sites where felling had taken place than at moorland or young forest sites while aggrading forest catchments appeared to be most resistant to changes in pH and ALK. Associated with these acid-base changes was a corresponding decline in labile aluminium (Al-L) concentrations. The pattern of nitrate (NO(3)) change was especially affected by the timing of felling in forested catchments. Large negative trends in NO(3) at stream sites were associated with felling during the early part of the study period. This downward trend was further enhanced as NO(3) concentrations fell below pre-felling levels as the second rotation crop became established. Few forest sites showed significant increases in NO(3) due to felling in the latter part of the study period. Most moorland loch sites showed a small but significant increase in NO(3,) probably in response to similar increases in N deposition and/or climatic impacts. Dissolved organic carbon (DOC) increased significantly at both forest and moorland sites, however, the extent of these increasing trends appeared to be positively correlated with absolute DOC concentrations. Despite the complex response of streams and lochs during the various stages of the forest cycle, especially for NO(3), both forest and moorland catchments showed generally similar and rapid responses to reductions in S deposition. Nevertheless, forested sites are still more acid and have higher concentrations of toxic forms of Al than moorland sites. Although the proposed emission reductions in Europe are likely to result in a continuing decline in S and N loadings to catchments, the continuing policy of planting second rotation forests in these acidified catchments may, in the long-term, delay or halt chemical and biological recovery. However, in the short-term, any increase in the uptake of N deposition by aggrading forests should help to counteract the acidifying effects of a small increase in the interception of S and N compounds.     

Human impact on rural landscapes in central and northern Europe

To analyse human influences on rural landscapes in present-day central and northern Europe and also to investigate sustainable landscape development concepts, an IALE (International Association for Landscape Ecology) regional Conference on ‘Perspectives of Rural Landscapes in Europe' was held in Pärnu, Estonia on 20–27 June 1996. The conference was undertaken specifically to exchange information between planners, managers, decision makers and scientists in the region. In the last few years, rural landscapes in Europe have changed significantly. Due to restructuring of agriculture in the European Union (EU) countries and radical socio-economic changes in eastern and central Europe, landscape change will continue. This stimulates interest for landscape ecologists to study the processes connected with such rapid development and to analyse its socio-economic and ecological consequences. Different conference findings that resulted from six keynote speeches, 33 oral presentations, 21 posters and organised excursions (1-day conference excursion and 4-day post-conference excursion) are presented here. Thirteen papers published as part of this special issue of Landscape and Urban Planning, and summarised here, deal with general and methodological principles of the analysis of land use changes and related landscape evaluation, and also present case studies on land use changes from Estonia, Germany and Sweden.     

中国建筑杂志的当代图景(2000～2010)

文章从老刊布局、新刊创立和外刊介入三个方面,总结了21世纪以来的10年间中国建筑杂志的变化和发展,对建筑杂志的定位、内涵和媒介特征与文化特征进行阐释,分析了当代中国建筑杂志的变革、面临的困局和新的趋势,直面建筑杂志自身的局限性和当下发展中的阻滞力,表达了对中国建筑杂志未来发展的期待。     

Long-term trends in accumulated metals (Cd, Cu and Zn) and metallothionein in bivalves from lakes within a smelter-impacted region

Temporal monitoring studies are needed to detect long-term trends in ecosystem health. In the present study, we tested metallothionein (MT) as a potential biomarker for long-term variations in trace metal levels in lakes subject to atmospheric metal inputs from a nearby copper smelter. Over a 13-year period, we estimated on several occasions ambient free Cd2+, Cu2+ and Zn2+ concentrations at the sediment-water interface in six lakes with contrasting metal levels, and measured metal and metallothionein concentrations in gills of bivalves (Pyganodon grandis) living in these lakes. All but one of the study lakes had comparable drainage ratios, so inter-lake differences in hydrological export of metals from contaminated watersheds to receiving waters were likely minimal. Declines in the metal emissions from the smelter (especially for Cd and Zn) during the 1980s led to appreciable decreases in both calculated free Cd2+ ion concentrations in the study lakes (-59+/-21% between 1989 and 1998) and accumulated Cd levels in their clam populations (-46+/-12% between 1989 and 2002). Taking all lakes into account, MT concentrations in bivalves have comparatively dropped by 44% (+/-10%) since 1989. In contrast to what we found for Cd, there were no significant reductions in the calculated free Cu2+ and Zn2+ concentrations in the various lakes during our study period (-2 and -10%, respectively, with 95% confidence intervals spanning zero). Overall, observed decreases in MT in bivalves over time were best correlated with similar decreases in both ambient and accumulated Cd levels (r = 0.77, P = 0.0003 and r = 0.79, P < 0.0001, respectively, both P-values corrected for temporal autocorrelation), suggesting that long-term trends in gill MT concentrations in P. grandis may be useful as predictors of temporal changes in environmental Cd contamination in lakes.     

A numerical study of the interannual variability of the Adriatic Sea (2000-2002)

A free-surface, three-dimensional finite-difference numerical model based on the Princeton Ocean Model (POM) has been implemented in order to simulate the interannual variability of the Adriatic Sea circulation. The implementation makes use of an interactive surface momentum and heat flux computation that utilizes the European Centre for Medium-Range Weather Forecasts (ECMWF) 6-h analyses and the model predicted sea surface temperatures. The model is also nested at its open boundary with a coarse-resolution Mediterranean general circulation model, utilizing the same surface forcing functions. The simulation and analysis period spans 3 years (1 Jan 2000 to 31 Dec 2002) coinciding with the "Mucilage in the Adriatic and the Tyrrhenian" (MAT) Project monitoring activities. Model results for the simulated years show a strong interannual variability of the basin averaged proprieties and circulation patterns, linked to the atmospheric forcing variability and the Po river runoff. In particular, the years 2000 and 2002 are characterized by a weak surface cooling (with respect to the climatological value) and well-marked spring and autumn river runoff maxima. Conversely, 2001 is characterized by stronger wind and heat (autumn cooling) forcings but no river runoff autumn peak, even though the total amount of water inflow during winter and spring is sustained. The circulation is characterized by similar patterns in 2000 and 2002 but very different structures in 2001. During the latter, deep water is not formed in the northern Adriatic. A comparison with the observed data shows that the major model deficiencies are connected to the low salinity of the waters, probably connected to the missed inflow of salty Ionian waters of Aegean origin and to the numerical overestimation of the vertical mixing processes.     

大直径多联体筒仓滑模施工工法(YJGF45-2000)

中铁十二局集团有限公司在广西防城港粮食码头及中转库 5万ｔ筒仓工程中施工的 2组 6联体直径 1 4 5ｍ的联体仓 ,是目前国内多联体中直径最大的筒仓群。该筒仓群采用我局自制的 6联体滑模施工 ,施工中从模板设计、制作、组装、滑升到出模混凝土强度控制、混凝土配合比设计、出模混凝土随滑随抹工艺等都积累了丰富的经验 ,形成了一套完整的滑模施工技术。1　特点( 1 )采用大直径多联体滑模 ,实现多个大直径联体筒仓的滑升施工 ,可确保结构的整体性 ,缩短施工工期 ,保证工程质量。( 2 )利用滑模操作平台 ,采用降模法作封顶支撑平台 ,一台两用…     

Long-term monitoring (1960-2008) of the river-sediment transport in the Red River Watershed (Vietnam): Temporal variability and dam-reservoir impact

The Red River (China/Vietnam, A = 155,000 km²) is a typical humid tropics river originating from the mountainous area of Yunnan Province in China. Based on information on daily discharge (Q) and suspended particulate matter (SPM) concentration between 1960-2008 for the SonTay gauging station (outlet of the River and entry to the Delta) provided by the National Institute IMHE-MONRE, the mean annual SPM flux was estimated at 90 Mt/yr, corresponding to a sediment yield of 600 t/km²/yr. The temporal variability of annual SPM fluxes (ranging from 24 to 200 Mt/yr) is strongly related to the interannual hydrological conditions. However, some years of high water flow were not associated with high sediment fluxes, especially after 1989 when the HoaBinh dam came into operation. Therefore, the median discharge pre- (3389 m³/s) and post 1989 (3495 m³/s) are similar indicating there was little or no change between both periods. Sediment rating curves (power law-type; SPM = aQ^b) were fitted for both periods (1960-1989; 1990-2008). The analysis of the pre- and post-1989 sediment rating parameters (a, b) suggests a downshift of b-parameter values after 1989, attributed to a decrease of the sediment supply due to the commissioning of the HoaBinh dam. A single sediment rating curve derived from 1960-1989 data was used to simulate the annual variability of former sediment delivery, generating excellent cumulative flux estimates (error ~ 1%). In contrast, applying the same rating curve to the 1990-2008 data resulted in systematic and substantial (up to 109%) overestimation. This suggests that the HoaBinh dam reduces annual SPM delivery to the delta by half, implying important metal/metalloid storage behind the HoaBinh dam.     

Thinking about planning in the transitional countries of central and Eastern Europe

The transition of the countries of Central and Eastern Europe from communism to post‐communism raises many questions about how the process is to be understood. The applicability of democratization theory to Eastern Europe and the international context of transition are discussed. A preliminary sketch of the impact of transition on spatial planning and urban development indicates that the results of transition are likely to be very uneven.     

Effect of COD/SO(4)(2-) ratio and sulfide on thermophilic (55 degrees C) sulfate reduction during the acidification of sucrose at pH 6

This study investigated the effect of the COD/SO₄²⁻ ratio (4 and 1) and the sulfide concentration on the performance of thermophilic (55 °C) acidifying (pH 6) upflow anaerobic sludge bed reactors fed with sucrose at an organic loading rate of 4.5 g COD l_reactor⁻¹ day⁻¹. Sulfate reduction efficiencies amounted to 65% and 25-35% for the COD/SO₄²⁻ ratios of 4 and 1, respectively. Acidification was complete at all the tested conditions and the electron flow was similar at the two COD/SO₄²⁻ ratios applied. The stepwise decrease of the sulfide concentrations in the reactors with a COD/SO₄²⁻ ratio of 1 by N₂ stripping caused an immediate stepwise increase in the sulfate reduction efficiencies, indicating a reversible inhibition by sulfide. The degree of reversibility was, however, affected by the growth conditions of the sludge. Acidifying sludge pre-grown at pH 6, at a COD/SO₄²⁻ ratio of 9 and exposed for 150 days to 115 mg l⁻¹ sulfide, showed a slower recovery from the sulfide inhibition than a freshly harvested sludge from a full scale treatment plant (pH 7 and COD/SO₄²⁻=9.5) exposed for a 70 days to 200 mg l⁻¹ sulfide. In the latter case, the decrease of the sulfide concentration from 200 to 45 mg l⁻¹ (35 mg l⁻¹ undissociated sulfide) by N₂ stripping caused an immediate increase of the sulfate reduction efficiency from 35% to 96%.     

Concentrations of heavy metals and plant nutrients in water, sediments and aquatic macrophytes of anthropogenic lakes (former open cut brown coal mines) differing in stage of acidification.

Concentration of heavy metals (Al, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn) as well as macronutrients (N, P, K, Ca, Mg, S) were measured in water, bottom sediments and plants from anthropogenic lakes in West Poland. The collected plants were: Phragmites australis, Potamogeton natans, Iris pseudoacorus, Juncus effusus, Drepanocladus aduncus, Juncus bulbosus, Phalaris arundinacea, Carex remota and Calamagrostis epigeios. Two reference lakes were sampled for Nymphaea alba, Phragmites australis, Schoenoplectus lacustris, Typha angustifolia and Polygonum hydropiper. These plants contained elevated levels of Cd, Co, Cr, Cu and Mn, and part of the plants contained in addition elevated levels of Mn, Fe, Pb, Ni and Zn. Analyses of water indicated pollution with sulfates, Cd, Co, Ni. Zn, Pb and Cu, and bottom sediments indicated that some of the examined lakes were polluted with Cd, Co and Cr. Strong positive correlations were found between concentrations of Co in water and in plants and between Zn in sediments and plants, indicating the potential of plants for pollution monitoring for this metal. Heavy metal accumulation seemed to be directly associated with the exclusion of Ca and Mg.     

完善规划干线路网的实施方案（2000～2010年）

进入下一个世纪,天津将为完善规划路网继续做出坚持不懈的努力,为了使项目更加科学化,特提出了（2000～2010年）道路建设项目的实施方案,供领导和有关部门决策参考。