Germination and early establishment of lower salt-marsh species in grazed and mown salt marsh

Abstract. Lower salt-marsh species occur more in the grazed than in the mown sites of a salt marsh in Schiermonnikoog in the Netherlands. This was demonstrated by a sowing experiment which determined which characteristic of the stand structure, height of the canopy or percentage of bare soil, is responsible for this difference. The total number of seedlings which emerged was negatively related to the height of the canopy and positively to the percentage of bare soil. The survival of seedlings of Suaeda maritima and Plantago maritima could be explained by the height of the canopy and for the latter species also by the percentage of bare soil. The survival of Aster tripolium and Plantago maritima was higher in grazed than in mown sites. Since the amount of bare soil was higher than seemed necessary for germination and survival, it was concluded that the taller canopy was responsible for the absence of lower salt-marsh species in the mown sites.     

Seasonal flooding,soil salinity and primary production in northern prairie marshes

Hydrologic regime is an important control of primary production in wetland ecosystems. I investigated the coupling of flooding, soil salinity and plant production in northern prairie marshes that experience shallow spring flooding. Field experiments compared whitetop (Scolochloa festucacea) marsh that was: (1) nonflooded, (2) flooded during spring with 25 cm water and (3) nonflooded but irrigated with 1 cm water · day^–1. Pot culture experiments examined whitetop growth response to salinity treatments. The electrical conductivity of soil interstitial water (EC_e) at 15 cm depth was 4 to 8 dS· m^–1 lower in flooded marsh compared with nonflooded marsh during 2 years. Whitetop aboveground biomass in flooded marsh (937 g · m^–2, year 1; 969 g · m^–2, year 2) exceeded that of nonflooded marsh (117 g · m^–2 year 1; 475 g · m^–2, year 2). Irrigated plots had lower EC_e and higher aboveground biomass than nonflooded marsh. In pot culture, EC_e of 4.3 dS · m^–1 (3 g · L^–1 NaCl) reduced total whitetop biomass by 29 to 44% and EC_e of 21.6 dS · m^–1 (15 g · L^–1 NaCl) reduced biomass by more than 75%. Large reductions of EC_e and increases of whitetop growth with irrigation indicated that plants responded to changes in soil salinity and not other potential environmental changes caused by inundation. The results suggest that spring flooding controls whitetop production by decreasing soil salinity during spring and by buffering surface soils against large increases of soil salinity after mid-summer water level declines. This mechanism can explain higher marsh plant production under more reducing flooded soil conditions and may be an important link between intermittent flooding and primary production in other wetland ecosystems.     

Biogeochemical consequences of winter flooding in brook valleys

Climatic change has great impacts on stream catchments and their ecology. Expectations are that more extreme climate events will result in undesired flooding in stream catchments. In the Netherlands, former floodplains with a history of agricultural use are put into use again as flooding areas for the purpose of water retention. This study focuses on the effects of winter flooding on various plant site conditions in the soil, such as redox, nutrient, pH, and base status. We compared the effects on groundwater- and rainwater-dominated floodplains. Water chemistry (pH, EC, HCO₃, SO₄, Cl, Ca, Mg, Na, K, , NO₃, NH₄, and PO₄) and soil nutrients (Total N and P, and bio-available P) were monitored for one year, including a 3–4 month period with winter flooding. In both floodplains no direct effect of the flood-water chemistry was detected in the pore water, because the soil pores had become saturated with groundwater or rainwater, respectively, just before flooding, flood-water did not penetrate the soil. We found that the increase in pH and ammonium concentration in the rainwater floodplain were due to changes in redox status, resulting from the completely water-filled state of the soil pores during the flooding event. Furthermore, we noticed an increase in soil nutrient contents and a shift in plant species composition in the rainwater floodplain: the vegetation included more plant species characteristic for N-richness. Finally, we conclude that winter flooding has more drastic effects on biogeochemical conditions and vegetation composition in the atmotrophic conditions characteristic for low-order subcatchments than in lithotrophic conditions in the larger, higher-order subcatchments of the stream basin.     

GENDER AND ETHICS COMMITTEES: WHERE’S THE ‘DIFFERENT VOICE’?

Prominent international and national ethics commissions such as the UNESCO International Bioethics Committee rarely achieve anything remotely resembling gender equality, although local research and clinical ethics committees are somewhat more egalitarian. Under‐representation of women is particularly troubling when the subject matter of modern bioethics so disproportionately concerns women’s bodies, and when such committees claim to derive ‘universal’ standards. Are women missing from many ethics committees because of relatively straightforward, if discriminatory, demographic factors? Or are the methods of analysis and styles of ethics to which these bodies are committed somehow ‘anti‐female’? It has been argued, for example, that there is a ‘different voice’ in ethical reasoning, not confined to women but more representative of female experience. Similarly, some feminist writers, such as Evelyn Fox Keller and Donna Haraway, have asked difficult epistemological questions about the dominant ‘masculine paradigm’ in science. Perhaps the dominant paradigm in ethics committee deliberation is similarly gendered? This article provides a preliminary survey of women’s representation on ethics committees in eastern and western Europe, a critical analysis of the supposed ‘masculinism’ of the principlist approach, and a case example in which a ‘different voice’ did indeed make a difference.     

The relationship of vegetation to environmental factors in Wangsuk stream and Gwarim reservoir in Korea: II. Soil environments

This paper presents a quantitative account of vegetation–soil environmental factor relationships in the Wangsuk stream (WS) and the Gwarim reservoir (GR) in Korea. Vegetation and the following soil variables were investigated in May, August and October 2004: pH, conductivity, water content, organic matter, total nitrogen content, NH₄–N content, PO₄–P content, total Ca, Mg, K, and Na content, extractable Ca, Mg, K and Na content, soil texture, distance from the channel, and elevation above water level. Species richness, diversity and ratio of hydrophyte occupation in WS were different from those in GR. Species richness was higher in WS, whereas the ratio of hydrophyte occupation was higher in GR. There were large temporal and spatial variations in plant distribution in the riparian and aquatic zones of WS but only slight variations in those of GR. These differences might have arisen from differences in flooding regime, distance from the stream channel related to elevation above water level, and soil properties such as soil texture and available nutrients. The median values of organic matter, total nitrogen, NH₄–N, PO₄–P and extractable Ca, Mg, K and Na contents in the soil were higher in GR than in WS. Sandy loam and loamy sand were common soil types in WS and clay loam and sandy clay loam in GR. Ten vegetation groups in WS and six in GR were identified using TWINSPAN. DCCA indicated that the distance from the stream channel was most strongly related to plant distribution and this reflected the spatial distribution of plant species in WS. In both WS and GR, NH₄–N content in soil and soil texture were important factors for the distribution of species in May, August and October. Spatial and temporal heterogeneity of soil variables were related to species distribution.     

Clinical Efficacy and Compatibility of Allogeneic Avital Tissue Transplants Sterilized with a Peracetic Acid/Ethanol Mixture

In the course of the past 20 years a quantity of approximately 60,000 allogeneic avital tissue grafts sterilized with the peracetic acid–ethanol method (PES) were transplanted successfully. Based on a retrospective report of clinical experience of the years 1997–2001 on the overall scope of tissue grafts manufactured by the Tissue Banks of the University Hospital Charité and the German Institute for Cell and Tissue Replacement, the clinical efficacy and side effects of 18.3% (3.087/16.823) of all transplants were studied. Cancellous (1.601/3.087) and cortical (291/3.087) bone transplants as well as amnion (1.027/3.087) constituted the greatest part. In 91% of the examined patients (2.369/2.592) tissue integration ratios ranging from good up to very well could be observed. The transplant function of defect replacement or of a spacer respectively could be obtained for all types of tissue. The clinical effect caused by the transplant resulted in more than 99% of the transplants in primary integration or in the desired aim of the therapy (defect replacement, stabilization in case of palliative operations, etc.). In less than 1% (9/2.592) of cases a secondary healing occurred for cancellous bone transplantations or, revisional operations became necessary. In all cases severe side effects, in particular transmission of infectious diseases or transplant rejections, were not observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tolerance of switchgrass to extreme soil moisture stress: Ecological implications

Switchgrass (Panicum virgatum L.), a native of eastern and central North America, is a leading candidate as a dedicated biofuel feedstock in the US due to its broad adaptability, rapid growth rate, and ability to grow in low production soils. To begin to characterize the important agronomic and ecological traits related to environmental tolerance of switchgrass, we evaluated fitness under stressful growing conditions. We assessed the germination, establishment, performance, and reproductive potential of four common accessions, both upland and lowland ecotypes, at various levels of soil moisture availability (moisture deficit to flooded) in the greenhouse. Seeds emerged and established (55–90% survival) under all soil moisture conditions (−0.3 MPa to flooded). Transplants of lowland ecotypes performed as well in flooded conditions as in field capacity controls, though flooding reduced performance of upland ecotypes. Drought treatments (−4.0 and −11.0 MPa) reduced tiller length and number, leaf area, and biomass production by up to 80%. However, once established, all plants survived at −4.0 MPa and had the same proportion of tillers in flower as at field capacity. The ability of switchgrass to germinate, establish, and flower in low moisture and flooded conditions, particularly lowland ecotypes, may increase the range of environments suitable for biofuel cultivation, and can serve as a baseline for further ecological studies and genetic improvement.     

水淹对钉螺卵影响的透射电镜观察

春汛期钉螺繁殖期在洞庭湖现场进行水淹螺卵试验,观察螺卵结构的动态变化。结果显示,对照组螺卵胶膜由胶原纤维层和基底膜组成,卵细胞核大,呈圆形或椭圆形,染色质丰富,细胞内含丰富线粒体、内质网和分泌颗粒等。水淹１０ｄ时,结构尚未见明显变化;至２０ｄ时,胶膜胶原纤维横纹不清,断裂有空洞,线粒体肿胀,嵴结构不清,核内染色质减少;３０ｄ时,出现核固缩或崩解,线粒体消失。说明在螺卵发育期水淹能很快使其发生病理损     

Functioning and toxicity of artificial soil mixtures with metal-bearing sewage sludge

Various artificial soil mixtures were prepared by mixing two different toxic metals containing sewage sludge from Ljubljana and Maribor wastewater treatment plants with natural mineral soil. The plots with mixtures were exposed to field environmental conditions for a period of 1 year, after which we assessed soil toxicity (germination test with Lactuca sativa), potential metal phyto-accessibility (diethylenetriamine pentaacetic acid – DTPA extraction test), soil functioning (by soil enzymes activity) and conducted a field growth test with Lollium perenne L. as a metal bio-indicator plant. The metal phyto-accessibility extraction test (DTPA) showed lower values than the metal accumulation test with L. perenne L., which also showed higher metal concentrations in roots compared to leaves. With the exception of the mixture containing 30% (w/w) of sludge from the Ljubljana wastewater treatment plant, all mixtures containing more than 20% of sludge negatively affected root elongation of L. sativa seeds, indicating an increase in artificial soils toxicity. Increasing the ratio of sludge from the Ljubljana plant increased dehydrogenase and decreased phosphomonoesterase, while the addition of sludge from the Maribor plant increased phosphomonoesterase activity. Overall, the effect of sludge addition on artificial soil properties, toxicity and functioning not only depended on dosage but was also sensitive to the source and pre-treatment of the sewage sludge.     

What confines an annual plant to two separate zones along coastal topographic gradients?

We investigated the roles of flooding, salinity, and plant competition in creating a bimodal zonation pattern of the marsh dominant annual plant, Suaeda salsa, along coastal topographic gradients on the Pacific coast of northern China. In two consecutive years, we manipulated salinity and flooding, salinity, and competition for S. salsa seedlings that had been transplanted into the mudflat, the high marsh, and the upland, respectively. S. salsa plants that had been transplanted into the mudflat were completely eliminated in the non-elevated treatments whereas they performed much better in the 10 cm elevated treatments, regardless of salinity treatments. Although the performance of S. salsa transplanted into the high marsh did not differ between the fresh (watered) and the salt (control) treatments, S. salsa seedling emergence in the high marsh was nearly completely inhibited in the salt treatments. In contrast, a large number of S. salsa seedlings did emerge in the fresh treatments. S. salsa transplanted into the upland performed well when neighbors were removed, whereas it appeared to be strongly suppressed when neighbors were present. These data indicated that flooding, salinity, and competition all played a role in determining the zonation pattern of S. salsa. Furthermore, the importance of salinity was found to vary with life-history stage. Based on the results from these field manipulative experiments, we suggest that the marsh plant zonation paradigm may hold true for plant distributions along landscape-scale topographic gradients from mudflats to uplands in general. The relative importance of flooding, salinity, and competition, however, may vary at different elevations within a site and between sites. Handling editor: Pierluigi Viaroli     

辽西褐土施肥及养分循环再利用中长期试验Ⅳ.土壤肥力变化

经12年田间试验,各施肥处理耕层土壤的肥力变化表明,在保持农业系统养分循环再利用基础上,施用适量化肥以平衡土壤养分收支,不仅可实现作物高产,减少过剩养分进入环境,并可改善土壤肥力,表现为明显提高了耕层的有机C,N浓度,不过,在本例中欲保持较高的土壤有效P水平,恐需在平均土壤P收支基础上适当增加P肥施用量。     

In Vivo Measurement Using Microdialysis of the Release and Metabolism of 5-Hydroxytryptamine in Raphe Neurones Grafted to the Rat Hippocampus

The overflow and metabolism of serotonin (5-hydroxytryptamine; 5-HT) from transplants of embryonic medullary and mesencephalic raphe neurones in the previously 5-HT-denervated hippocampus have been analyzed in vivo using intracerebral dialysis. The average density of 5-HT-immunoreactive fibres in the grafted hippocampus was less than in nonlesioned hippocampus. Nonetheless, both basal and potassium-stimulated levels of 5-HT in the dialysates were restored to approximately normal after transplantation of medullary raphe cells, whereas mesencephalic implants resulted in over twice the 5-HT output observed in control hippocampus. However, 5-hydroxyindoleacetic acid (5-HIAA) overflow was increased only after grafting of mesencephalic raphe and then only to normal levels; medullary implants, by contrast, failed to enhance 5-HIAA output above that from lesion-only hippocampus. The evidence of a relative hyperactivity of the grafted neurones may explain the disproportionate improvements in various lesion-induced behavioural deficits after grafting of nervous tissue. In addition, differences in the presynaptic regulation of 5-HT release and metabolism are also apparent in the transplants; these variations are dependent on the precise origin of the serotoninergic cells.