The influence of serum screening on the amniocentesis rate in women of advanced maternal age

We investigated the effect of maternal serum screening on the amniocentesis (AC) rate in women of advanced maternal age. The AC rate after maternal serum screening was compared in two groups of women with a singleton pregnancy, 855 women of 30–35 years and 98 of 36 years and older. In our population, 34·1 per cent of the women of 36 years or older were ‘screen-positive’ for Down syndrome. Only 41·2 per cent of these women chose to undergo AC as opposed to 88·2 per cent in the younger age group. Within the older age group, the tendency to avoid AC increased with increasing age. Maternal serum screening led to a significant decrease in the AC rate in the older women. In this group, a comparison between the ‘a priori’ and the calculated risk might have had more influence on the decision to undergo AC than being screen-positive or screen-negative as such. We conclude that maternal serum screening had a major effect on the AC rate in women of advanced maternal age. This is of importance in a society in which the average maternal age is steadily increasing.     

Female mate choice in the zebra finch — the effect of male beak colour and male song

Studies of female mate preference in zebra finches (Taenopygia guttata) have shown that male beak colour and song rate are important. However, the two characters are correlated. Here the effect of beak colour and song rate on female choice are examined independently. In mate choice tests involving two males, beak colour was manipulated artificially using nail varnish. The results showed that females showed a significant preference for males with a high song rate, but not with a red beak. Females did not prefer males with a red beak if song rate was low and females preferred males with orange beaks who expressed a high song rate. Female preference for males with red beaks was not found when beak and song characters were no longer correlated.     

果树光合作用研究进展

综述了果树光合作用的研究方法，观测仪器，日变化和季节变化，以及内在因素(种类、品种、年龄、叶位、叶绿素含量、酶系统)和外部因素(光照、CO2、温度、湿度、土壤、外用药剂)对果树光合作用的影响。     

农桐间作的养分循环

对农桐间作（以桐为主间作型）的养分循环规律进行了研究。结果表明，泡桐各器官营养元素的含量随季节而变化。对营养元素的年吸收量为４７１．９５９５ｋｇ／ｈｍ￣２，其中氮１５５．１４２９ｋｇ／ｈｍ￣２，磷８０．０８２１ｋｇ／ｈｍ￣２，钾８７．０３９４ｋｇ／ｈｍ￣２，钙１１９．４６０３ｋｇ／ｈｍ￣２，镁３０．２３４８ｋｇ／ｈｍ￣２。营养元素的年归还量为３３１．６１５５ｋｇ／ｈｍ￣２，其中氮１０２．５７２１ｋｇ／ｈｍ￣２，磷４３．２９２２ｋｇ／ｈｍ￣２．钾６３．６４９７ｋｇ／ｈｍ￣２，钙９７．３５８６ｋｇ／ｈｍ￣２，镁２４．７４２９ｋｇ／ｈｍ￣２。营养元素的循环率为７０、２６％，其中氮６６．１１％，磷５４．０６％，钾７３．１３％，钙８１．５０％，镁８１．８４％。     

米草光合作用速率季节变化及其对初级生产的影响

对江苏省滨海具盐沼生态系统中大米草和互花米草群落有关生理生态学指标进行了为期一年的定位观察和测定。结果表明：互花米草和大米草，地上生物量（干重）在９月达到最高值，分别为１７１４ｇ／ｍ￣２和４１９ｇ／ｍ￣２；叶绿素季节变化模式分别呈斜“Ｚ”型和扁“Ｗ”型。两种米草光合作用同化率６月明显高于９月．植物材料能含量变化从１２．５６ｋＪ／ｇ到２０．１０ｋＪ／ｇ。     

大亚湾惠州岸段城市化发展与海岸带生态系统保护协调研究

在分析海岸带生态系统结构、功能特点的基础上，指出大亚湾惠州岸段可持续发展的途径就是实现经济开发与海岸带生态环境保护之间的协调发展，为此，提出了区域生态－－经济系统综合效益表达工，并运用该表达式，从大亚湾海水环境保护的角度出发，得出了惠州大亚湾沿岸地区在１９９４年－２０１０年间工业发展的合理速度。     

Nitrogen accumulation and plant species replacement in three salt marsh systems in the Wadden Sea

Salt marsh development on the coastal barrier island of Schiermonnikoog (The Netherlands) was compared with two other salt marsh systems in the Wadden Sea. Accretion rate, nitrogen accumulation and changes in plant species composition were investigated using chronosequences. The age of the marsh was estimated from aerial photographs and old maps. In 7230 plots, the elevation of the marsh surface, the thickness of the sediment layer (clay) and the presence of plant species was recorded. In addition, the nitrogen pool was measured at each successional stage. Accretion rates were similar in the three salt marshes. Higher accretion rates were found at younger marshes. A strong linear relationship between nitrogen pool size and thickness of the clay layer was found for the three marshes. The accumulation rate of nitrogen is therefore strongly related to the accretion rate. Thus, more nitrogen is present in the sediment of later successional stages where more clay has accumulated. On the high salt marsh (55 cm+MHT),Ameria maritima disappeared andArtemisia maritima, Juncus gerardi andElymus athericus established at sites with a thicker clay layer. On the low salt marsh (25 cm+MHT),Plantago maritima, Puccinellia maritima andLimonium vulgare disappeared andAtriplex (Halimione) portulacoides established. Apparently, with the accumulation of clay and therefore of nitrogen, tall growing species take over in salt marshes not grazed by livestock.     

Optimum Nitrogen Use and Reduced Nitrogen Loss for Production of Rice and Wheat in the Yangtse Delta Region

A long-term field and lysimeter experiment under different amount of fertilizer-N application was conducted to explore the optimal N application rates for a high productive rice–wheat system and less N leaching loss in the Yangtse Delta region. In this region excessive applications of N fertilizer for the rice–wheat production has resulted in reduced N recovery rates and environment pollution. Initial results of the field experiments showed that the optimal N application rate increased with the yield. On the two major paddy soils (Hydromorphic paddy soil and Gleyed paddy soil) of the region, the optimal N application rate was 225–270 kg N hm^–2 for rice and 180–225 kg N hm^–2 for wheat, separately. This has resulted in the highest number of effective ears and Spikelets per unit area, and hence high yield. Nitrogen leaching in the form of NO ₃ ^– -N occurs mainly in the wheat-growing season and in the ponding and seedling periods of the paddy field. Its concentration in the leachate increased with the N application rate in the lysimeter experiment. When the application rate reached 225 kg N hm^–2, the concentration rose to 5.4–21.3 mgN l^–1 in the leachate during the wheat-growing season. About 60% of the leachate samples determined contained NO ₃ ^– -N beyond the criterion (NO ₃ ^– -N 10 mg l^–1) for N pollution. In the field experiment, when the N application rate was in the range of 270–315 kg hm^–2, the NO ₃ ^– -N concentration in the leachate during the wheat-growing season ranged from 1.9 to 11.0 mg l^–1. About 20% of the leachate samples reached close to, and 10% exceeded, the criterion for N pollution. Long-term accumulation of NO ₃ ^– -N from leaching will no doubt constitute a potential risk of N contamination of the groundwater in the Yangtse Delta Region.     

Relationship between filtration activity and food availability in the Mediterranean mussel <Emphasis Type="Italic">Mytilus galloprovincialis</Emphasis>

The filtration activity of the Mediterranean mussel, Mytilus galloprovincialis, was assessed under different concentrations and compositions of seston by using a new automated image acquisition and analysis system. This approach allowed for frequent and simultaneous measurements of valve gape and exhalant siphon area. Filtration rates were measured through clearance measurements whereas pumping rates were measured using hot-film probes. The average filtration rate (17.5 l g h⁻¹ DW⁻¹ for a 0.36 g DW mussel) recorded during the present study was higher than those available for Mytilus edulis when standardized to flesh dry weight but almost equivalent (17.5 l h⁻¹ g DW⁻¹ for a 53 mm shell length mussel) to those rates when standardized to shell length. Immediately after the addition of algal cells (Isochrysis galbana; 4.5 μm in size), valve gape, exhalant siphon area and filtration rate increased quickly as mussels reached their maximum filtration activity. These three parameters then gradually decreased until complete closure of the shell. The algal cell concentration inducing this transition was close to 800 cells ml⁻¹ and 0.5 μg Chl a l⁻¹. When algal concentration was maintained above this threshold by successive algal additions, both valve gape and exhalant siphon area remained maximal. Temporal changes in the exhalant siphon area were continuous as opposed to those of valve gape. Therefore, despite the significant correlation between these two parameters, valves and siphon were sometimes dissociated due to a reduction of the area or even a closure of the exhalant siphon while the valves remained open. The velocity of exhaled water tended to be constant irrespective of exhalant siphon area and thus pumping rates were a linear function of exhalant siphon area. Consequently, reductions in exhalant siphon area and pumping rate were almost similar in M. galloprovincialis. Our results thus clearly support the hypothesis that exhalant siphon area constitutes a better proxy of pumping rate than valve gape as already suggested for Mytilus edulis. Finally, the high filtration rates measured during the present study together with the high concentrations of inorganic matter (> 40 mg DW l⁻¹) requested to alter those rates suggest that the studied mussels were well adapted to oligotrophic waters featuring strong hydrodynamism and frequent sediment resuspension events.     

Using Demographic Invariants to Detect Overharvested Bird Populations from Incomplete Data

Abstract:  Conservation biology must be able to provide guidelines even when available data are incomplete, because data on rare and endangered species are usually limited. For instance, data on the effect of additional—human-induced—sources of mortality on vertebrate populations, such as bycatch of seabirds by longline fisheries, are typically incomplete. The importance of an additional source of mortality can be evaluated by comparing it with the maximum annual growth rate of the species of concern, and various authors have attempted to determine the maximum growth rate from incomplete data. We developed a procedure we call the "demographic invariant method" (DIM). First we determined that the maximum growth rate per generation does not vary, by recalling that it is a dimensionless number primarily independent of body weight and also by empirically establishing its near constancy over a restricted set of bird species for which reliable demographic information was available. This first step provided an implicit function linking generation time and maximum annual growth rate, from which we obtained the maximum annual growth rate as a simple function of generation time. From several different ways of obtaining estimates of generation time, we derived in turn several ways to estimate the maximum annual growth rate of a bird species from incomplete demographic data set. We applied our approach to the Black-footed Albatross (Phoebastria nigripes) and determined from incomplete data that longline fishery bycatch has a biologically significant impact on the growth potential of Black-footed Albatross populations. Our method can be applied broadly to the conservation and management of harvested bird populations.