Nutrient transfer functions: the site of integration between feeding behaviour and nutritional physiology

Summary. We describe and extend a graphical approach to quantitative nutrition that focuses on the interplay between behavioural and physiological components of nutritional regulation. The site of integration is the nutrient transfer function, which is the function describing the time course of nutrient transfer between serially connected nutritional compartments (e.g., from the gut to the blood). The relationship between the shape of the nutrient transfer function and the temporal patterns of feeding determines the values of two key quantitative parameters of nutrition: the rate ('power') and the efficiency of nutrient acquisition. The approach can be extended to consider, in addition to the short-term behavioural and physiological decisions made by animals, some ecological determinants and longer-term, life history consequences of such decisions. Most importantly, this category of models can provide insights into the interplay among the various nutrients in an animal's diet. We illustrate this using hypothetical examples, and also present preliminary data for the power-efficiency relationships of protein and digestible carbohydrates in locusts. Finally, we consider existing evidence for the various means available to these and other insects for regulating such relationships. Received 24 September 1997; accepted 9 December 1997.     

Spawning behaviour and sex hormone levels in adult and precocious brown trout (Salmo trutta L.) males and the effect of anosmia

Summary. In the present experiment the behaviour and endocrine status of males of the brown trout, Salmo trutta L., (Salmoniformes: Salmonidae) were studied when males were kept in a stream tank with a nest digging female. Groups of mature adult males and precocious intact or anosmic male parr were placed with the nesting female so that the group resembled a natural spawning situation with big anadromous fish acting as dominant males and precocious parr acting as “sneakers”. A control experiment was also run with only males without a female present. In intact parr there were significant positive correlations between the per cent of the total observation time spent with a female, milt volume, and plasma concentration of 17α, 20β-dihydroxy-4-pregnen-3-one. Anosmic parr had significantly lower volumes of strippable milt and gonadal steroid hormone levels compared with intact parr. However, no differences were found in the control experiment. Significantly fewer anosmic parr attended and courted the nesting female and those anosmic fish that attended the female had significantly lower plasma levels of gonadal hormones. Intact parr also displayed a greater number of agonistic acts against other parr without any difference in fighting ability. No differences in aggression occured in the control experiment. In adult males together with a female, post-experimental gonadal steroid hormone levels were higher than pre-experimental levels. Positive correlations between aggression and androgen hormone levels were observed in adult males. No differences in plasma hormone levels were observed between adult males and intact precocious males. The results show that olfactory occlusion results in low steroid hormone levels and milt volumes in precocious males placed in a spawning situation. The courting behaviour was also affected by anosmia. Odours from the nesting female may have caused the enhanced plasma hormone levels and stimulated the males to attend the female. Received 15 May 1997; accepted 29 June 1997.     

Restricted adaptive cluster sampling

Adaptive cluster sampling can be a useful design for sampling rare and patchy populations. With this design the initial sample size is fixed but the size of the final sample (and total sampling effort) cannot be predicted prior to sampling. For some populations the final sample size can be quite variable depending on the level of patchiness. Restricted adaptive cluster sampling is a proposed modification where a limit is placed on the sample size prior to sampling and quadrats are selected sequentially for the initial sample size. As a result there is less variation in the final sample size and the total sampling effort can be predicted with some certainty, which is impor- tant for many ecological studies. Estimates of density are biased with the restricted design but under some circumstances the bias can be estimated well by bootstrapping. © Rapid Science 1998     

Semi-parametric statistical approaches for space-time process prediction

The problem of estimation and prediction of a spatial-temporal stochastic process, observed at regular times and irregularly in space, is considered. A mixed formulation involving a non- parametric component, accounting for a deterministic trend and the effect of exogenous variables, and a parametric component representing the purely spatio-temporal random variation is proposed. Correspondingly, a two-step procedure, first addressing the estimation of the non- parametric component, and then the estimation of the parametric component is developed from the residual series obtained, with spatial-temporal prediction being performed in terms of suitable spatial interpolation of the temporal variation structure. The proposed model formula-tion, together with the estimation and prediction procedure, are applied using a Gaussian ARMA structure for temporal modelling to space-time forecasting from real data of air pollution concentration levels in the region surrounding a power station in northwest Spain.     

典型海岛生态系统服务及价值评估

海洋生态系统服务评估相关研究主要集中在特殊海洋生态系统的评估方面.海岛生态系统兼有陆地和海洋的生态系统特征,生态系统组成、结构复杂,很多的服务表现为岛陆互相交错,难以分别计量.选择庙岛群岛南五岛作为研究区域,研究了其生态系统服务,并进行了价值评估.结果表明:2003年庙岛群岛南五岛生态系统服务总价值为3.08×108元.其中,市场价值占到总服务价值的50.99%,与非市场价值基本持平.对于非市场生态系统服务,如气候调节、废弃物处理等,我们仅计算了目前人们已经认识到和容易计算的生态系统服务部分.因此,该研究仅为对庙岛群岛南五岛生态系统服务价值的保守估算.     

南麂列岛海域浮游植物的群落结构研究

于2006年4月～2007年3月采集浙江省南麂列岛海域水样,研究了浮游植物的种类组成、分布特征、季节动态以及赤潮生物的现状.共鉴定浮游植物93种,其中硅藻35属68种,甲藻11属21种,蓝藻1属2种以及金藻1属2种.浮游植物的优势种类在不同季节各有不同.南麂海域浮游植物细胞丰度较高,年平均细胞丰度达到319.03 cells/mL,高峰区集中分布在春季和夏季.对浮游植物群落的多项生态学指标进行了分析.     

Global sensitivity analysis of a process-based model for ammonia emissions from manure storage and treatment structures

The development of process-based models to estimate ammonia emissions from animal feeding operations (AFOSs) is sought to replace costly and time-consuming direct measurements. Critical to process-based model development is conducting sensitivity analysis to determine the input parameters and their interactions that contribute most to the variance of the model output. Global and relative sensitivity analyses were applied to a process-based model for predicting ammonia emissions from the surface of anaerobic lagoons for treating and storing manure. The objectives were to compare global sensitivity analysis (GSA) to relative (local) sensitivity analysis (RSA) on a process-based model for ammonia emissions. Based on the first-order coefficient, both GSA and RSA showed the model input parameters in order of importance in process model for ammonia emissions from lagoon surfaces were: (i) pH, (ii) lagoon liquid temperature, (iii) wind speed above the lagoon surface, and (iv) the concentration of ammoniacal nitrogen in the lagoon. The GSA revealed that interactions between model parameters accounted for over two-thirds of the model variance, a result that cannot be achieved using traditional RSA. Also, the GSA showed that parameter interactions involving liquid pH had more impact on the model output variance than the single parameters: (i) temperature, (ii) wind speed, or (iii) total ammoniacal nitrogen. This study demonstrates that GSA provides a more complete analysis of model input parameters and their interactions on the model output compared to RSA. A comprehensive tutorial regarding the application of GSA to a process model is presented.