Alliances in winter flocks of willow tits; effects of rank on survival and reproductive success in male-female associations

Summary The value of being dominant in winter flocks of willow tits may not only be a matter of personal survival for males, although their survival probability was highest among flock members. Winter flocks of willow tits contain male-female subunits, and the dominant pair may be viewed as an alliance based on mutual benefits. Dominant males provide their mates with protection in winter, and females return the help in reproductive success. Survival was directly related to rank only within sexes. Mates of dominant males survived significantly better than low-ranked males even though these females were subordinate to these males in direct interactions. Mates of dominant males were relatively spared from costs of low rank as they were subject to aggression less often than expected. Presumably dominant males prevented such attacks, as they excluded other flock members from high tree sections where their mates fed. Males should gain from improving the survival probability of their mates since it was not always possible to replace lost mates in spring populations having a male-biased sex ratio. Dominance in avian winter flocks may thus have more indirect effects than merely to improve the personal survival probability through resource priority. The benefits of being a dominant suggest that subordinate willow tits join groups because there is no space available for them to take up a territory as dominants.     

Temporal induction pattern of hepatic cytochrome P450 1A in thermally acclimated dab (Limanda limanda) treated with 3,3′,4,4′-Tetrachlorobiphenyl (CB77)

Mature male dab (Limanda limanda) acclimated at 10° and 16°C were orally administered a single dose of 0.5 mg/kg 3,3′,4,4′-tetrachlorobiphenyl (CB77). At both temperatures, levels of cytochrome P450 1A (CYP1A) protein and 7-ethoxyresorufin O-deethylase (EROD) activity showed a two to six fold induction 40 days after CB77 treatment compared to control groups. Maximum responses of both EROD activity and CYP1A protein for the warm-acclimated fish were observed at 5 days after treatment. For the cold-acclimated fish a slow, progressive elevation for both EROD activity and CYP1A protein was observed and maximum responses were measured 40 days after treatment. Absolute EROD activity and CYPIA protein levels of fish from both temperatures were equally high at 40 days after treatment. Since in the control groups EROD activity and CYP1A protein levels were higher in the cold-acclimated fish, the magnitude of induction was higher in the warm acclimated ones. The highest concentrations of CB77 in muscle of fish from both temperatures were found at 5 and 10 days after treatment. The liver somatic index (LSI) showed 1.5 fold significantly higher values for the fish acclimated at 10°C.     

Cost-benefit ratio and empirical examination of the acceptance of heathland maintenance in the Lueneburg heath nature reserve

The cost-benefit ratio of heathland maintenance measures was assessed in the Lueneburg Heath nature reserve in North-West Germany. This nature reserve contains large areas of heathland and is of substantial ecological and historical importance. The heathland can only be preserved by regular maintenance. For this assessment the costs of the maintenance measures were traced and a survey of visitors was carried out. The willingness-to-pay of the visitors for the heathland maintenance was determined as an assessment of the benefit created. Furthermore, the social acceptance of each maintenance measure was examined as this variable can influence the economic data considerably. These aspects represent a basis for the assessment of the net costs and benefits and for the calculation of the net present value (NPV) provided by the maintenance of the area. The results show a substantial positive net benefit of the heathland maintenance as a whole and varying acceptance of the different maintenance measures.     

Removal of Phosphorus in Constructed Wetlands with Horizontal Sub-Surface Flow in the Czech Republic

The major processes responsible for phosphorus (P) removal in constructed wetlands with horizontal sub-surface flow (HSF CWs) are adsorption, precipitation and plant uptake if the biomass is harvested. The filtration materials frequently used in HSF CWs, i.e., gravel or crushed rock, provide only limited adsorption and plants are not regularly harvested. As a result, the removal of P in HSF CWs is usually low and typically amounts to only 40 to 60% during the treatment of municipal or domestic sewage. The average inflow and outflow P concentrations for vegetated beds of Czech HSF CWs were 6.6 mg L^-1 and 3.6 mgL^-1, respectively. The average P removal was 45.7%. Despite a wide fluctuation of inflow phosphorus loading rates in the Czech CWs (10.9 – 356 g P m^-2 a^-1) the retention of P is well predictable. The CWs in the Czech Republic are relatively new and therefore, it is not possible to evaluate long-time performance of P removal. However, results from systems that have been in operation for longer periods (maximum of 9 years) indicate that P removal decreases over years probably as a result of limited sorption capacity. The amount of P removed by aboveground Phragmites biomass is very low and usually does not exceed 5% of the total removed P in the beginning of operation. As the sorption decreases over years and macrophyte biomass increases at the same time the importance of P bound in biomass becomes higher but it rarely exceeds the level of 20% of the total P removed.     

UNCERTAINTY OF EXTREME FLOOD ESTIMATES INCORPRATING HISTORICAL DATA1

ABSTRACT: The ability to predict extreme floods is an important part of the planning process for any water project for which failure will be very costly. The length of a gage record available for use in estimating extreme flows is generally much shorter than the recurrence interval of the desired flows, resulting in estimates having a high degree of uncertainty. Maximum likelihood estimators of the parameters of the three parameter lognormal (3PLN) distribution, which make use of historical data, are presented. A Monte Carlo study of extreme flows estimated from samples drawn from three hypothetical 3PLN populations showed that inclusion of historical flows with the gage record reduced the bias and variance of extreme flow estimates. Asymptotic theory approximations of parameter variances and covariances calculated using the second and mixed partial derivatives of the log likelihood function agreed well with Monte Carlo results. First order approximations of the standard deviations of the extreme flow estimates did not agree with the Monte Carlo results. An alternative method for calculating those standard deviations, the “asymptotic simulation” method, is described. The standard deviations calculated by asymptotic simulation agree well with the Monte Carlo results.     

Technique for assessing erosion risk from mountain footpaths

One of the most pressing problems facing wilderness managers in the ecologically fragile Drakensberg Mountains, South Africa, is that of path erosion, since it detracts from the wilderness experience and is very costly to remediate. As increasing demand for wilderness and outdoor recreation places greater pressure on paths and trails, it will be necessary to increase path network size and capacity, and it is important that new paths are routed such that maintenance requirements are minimal. This study describes the development of a technique based on the site and environmental variables of rainfall, topographic slope, and lithology, which enables assessment of path erosion risk before paths are planned and constructed. The technique was tested on a path at the Drakensberg resort of Loteni, and showed good correlation with actual path degradation. When used as a tool in path network planning, it can aid in the selection of low-maintenance routes and also help in planning maintenance budgets.     

Overview of case studies on recovery of aquatic systems from disturbance

An extensive review of the published literature identified more than 150 case studies in which some aspect of resilience in freshwater systems was reported. Approximately 79% of systems studied were lotic and the remainder lentic. Most of the stressor types were chemical with DDT (N=29) and rotenone (N=15) the most common. The most common nonchemical stressors were logging activity (N=16), flooding (N=8), dredging (N=3), and drought (N=7). The variety of endpoints to which recovery could be measured ranged from sparse data for phytoplankton (N=13), periphyton (N=6), and macrophytes (N=8) to relatively more data for fish (N=412) and macroinvertebrates (N=698). Unfortunately the same characteristics were rarely measured consistently among sites. For example, with respect to fish, more than 30 different species were studied and recovery was measured in many ways, most commonly on the basis of: (1) first reappearance of the species, (2) return time of predisturbance densities, and (3) return time of predisturbance average individual size. Based on these criteria, all systems in these studies seem to be resilient to most disturbances with most recovery times being less than three years. Exceptions included when (1) the disturbance resulted in physical alteration of the existing habitat, (2) residual pollutants remained in the system, or (3) the system was isolated and recolonization was suppressed.     

两维缺陷分析:用于保护规划和实施生物多样性政策的有效手段

在景观水平的管理中,为了保护具有代表性和连接成片的生境网络,以达到维持生物多样性的目的,就必须在不同规模上将保护、经营和生境恢复等几项工作有机结合.我们认为将自然和社会科学融为一体的两维缺陷分析方法是实施生物多样性政策的有效工具.这个工具把与生物相关的"水平"生态学问题与"垂直"的制度体制和其它社会问题有机结合考虑.以森林生物多样性为例,本文将演示如何将与生物多样性保护有关的生态学和制度等方面的问题综合考虑,从而促进整个区域发展的环境可持续性.尤其,我们用区域性缺陷分析方法,即先确定对"绿色基础设施"起功能性连接作用的重点森林类型和生境模型,以此作为工具进行"水平"缺陷分析.就"垂直"范围而论,通过鉴别政策实施中的体制性障碍我们指出社会科学如何用于在实际景观范围内评估生物多样性政策实施是否成功.研究表明,多学科间的合作方法能应用于其它各类环境,包括其它陆生生物和水生生态系统,在这些生态系统中,重要栖息地的连接性、对栖息地丧失的非线性响应,以及社会和经济问题在同一景观内交织在一起.