Test of a behavior-based individual-based model: response of shorebird mortality to habitat loss.

In behavior-based individual-based models (IBMs), demographic functions are emergent properties of the model and are not built into the model structure itself, as is the case with the more widely used demography-based IBMs. Our behavior-based IBM represents the physiology and behavioral decision making of individual animals and, from that, predicts how many survive the winter nonbreeding season, an important component of fitness. This paper provides the first test of such a model by predicting the change in winter mortality of a charadriid shorebird following removal of intertidal feeding habitat, the main effect of which was to increase bird density. After adjusting one calibration parameter to the level required to replicate the observed mortality rate before habitat loss, the model predicted that mortality would increase by 3.65%, which compares well with the observed increase of 3.17%. The implication that mortality was density-dependent was confirmed by predicting mortality over a range of bird densities. Further simulations showed that the density dependence was due to an increase in both interference and depletion competition as bird density increased. Other simulations suggested that an additional area of mudflat, equivalent to only 10% of the area that had been lost, would be needed by way of mitigation to return mortality to its original level. Being situated at a high shore level with the flow of water in and out impeded by inlet pipes, the mitigating mudflat would be accessible to birds when all mudflats in the estuary were covered at high tide, thus providing the birds with extra feeding time and not just a small replacement mudflat. Apart from providing the first, and confidence-raising, test of a behavior-based IBM, the results suggest (1) that the chosen calibration procedure was effective; (2) that where no new fieldwork is required, and despite being parameter rich, a behavior-based IBM can be parameterized quickly (few weeks), and thus cheaply, because so many of the parameter values can be obtained from the literature and are embedded in the model; and (3) that behavior-based IBMs can be used to explore system behavior (e.g., the role of depletion competition and interference competition in density-dependent mortality).     

塔基图穆保护区——库克群岛的社区所属生态旅游明星

塔基图穆保护区 1996年创建于库克群岛的拉罗汤加岛 , 其目标是为了当前和未来生产者的利 益而对生物多样性实施保护 . 只有当地人民对其土地和资源拥有所有权 . 生态旅游将成为该 保护区的主要经济活动 . 在土地所有者同意和支持下 , 一个有指导的 " 大自然漫步 " 已经组 织起来 .     

Role of heavy polar organic compounds for water repellency of sandy soils

Separation and chemical characterisation of specific compounds responsible for soil water repellency has not previously been achieved. Here we describe the extraction, separation and analysis by gas chromatography-mass spectrometry of organic compounds found in wettable and water repellent sandy soils from the Netherlands and United Kingdom. Fatty acids (C₁₆–C₂₄), amides (C₁₄–C₂₄), alkanes (C₂₅–C₃₃), aldehydes/ketones (C₂₃–C₃₁) and complex ring-containing structures were detected in all samples. We found a greater abundance of high molecular mass polar compounds in the water repellent samples.     

The interpretation of planning appeals

The extent to which aggrieved applicants appeal against planning refusals varies between types of development, between regions and over time. So, too, though in lesser degree, does the extent to which appeals are successful. The paper seeks to explain these variations. It does so by arguing that the appeal rate varies with the support that central government ministers and their inspectors (the Central Planning Authority, CPA) give to the local planning authorities (LPAs), with appeal costs and with applicant and LPA willingness to renegotiate over refused applications. The appeal success rate is seen to be largely independent of the appeal rate and varies with potential appellants’ awareness of CPA policy and with their rationality.

It is concluded that appeal rate differences are best explained in terms of the CPA's support for the LPAs whether consideration is given to applications submitted nationally for different development types, to applications submitted in the eight English regions or to applications submitted in England and Wales over the period since 1974. Thus, CPA support for the LPAs is high in relation to change of use and householder developments but low in relation to development of the other major type; the CPA is less supportive of LPA policy in Yorkshire and Humberside and in East Anglia than in the other English regions, at least in the mid 1980s; and the CPA markedly reduced its support for the LPAs in England and Wales in the early 1980s.

It is also concluded that the low appeal success rate for minor residential development is the result of low appellant rationality, potential appellants being particularly determined to press their proposals against the odds. Appellant awareness of CPA policy and rationality may be comparable for the remaining development types since the appeal success rate shows little variation. Similarly, appellant awareness and rationality may be comparable in the eight English regions. In contrast, the appeal success rate in England and Wales as a whole has increased since 1974 perhaps because potential appellants are now more aware of CPA policy.     

High-temperature tolerance of photosynthesis in the red alga Chondrus crispus

Chondrus crispus (Stackhouse) is a perennial red seaweed, common in intertidal and shallow sublittoral communities throughout the North Atlantic Ocean. In the intertidal zone, C. crispus may experience rapid temperature changes of 10 to 20C° during a single immerison-emerision cycle, and may be exposed to temperatures that exceed the thermal limits for long-term survival. C. crispus collected year-round at Long Cove Point, Chamberlain, Maine, USA, during 1989 and 1990, underwent phenotypic acclimation to growth temperature in the laboratory. This phenotypic acclimation enhanced its ability to withstand brief exposure to extreme temperature. Plants grown at summer seawater temperature (20°C) were able to maintain constant rates of lightsaturated photosynthesis at 30°C for 9 h. In contrast, light-saturated photosynthetic rates of plants grown at winter seawater temperature (5°C) declined rapidly following exposure to 30°C, reached 20 to 25% of initial values within 10 min, and then remained constant at this level for 9 h. The degree of inhibition of photosynthesis at 30°C was also dependent upon light intensity. Inhibition was greatest in plants exposed to 30°C in darkness or high light (600 mol photons m^-2s^-1) than in plants maintained under moderate light levels (70 to 100 mol photons m^-2s^-1). Photosynthesis of 20°C-acclimated plants was inhibited by exposure to 30°C in darkness or high light, but the degree of inhibition was less than that exhibited by 5°C-grown plants. Not only was light-saturated photosynthesis of 20°C plants less severely inhibited by exposure to 30°C than that of 5°C plants, but the former also recovered faster when they were returned to growth conditions. The mechanistic basis of this acclimation to growth temperature is not clear. Our results indicate that there were no differences between 5 and 20°C-grown plants in the thermal stability of respiration, electron transport associated with Photosystems I or II, Rubisco or energy transfer between the phycobilisomes and Photosystem II. Overall, our results suggest that phenotypic acclimation to seawater temperature allows plants to tolerate higher temperatures, and may play an important role in the success of C. crispus in the intertidal environment.     

REVIEW OF DETERMINATION OF INSTREAM FLOW REQUIREMENTS WITH SPECIAL APPLICATION TO AUSTRALIA1

ABSTRACT: A critical examination of the techniques used to assess and specify environmental instream flow requirements is provided. The strengths and weaknesses of individual techniques are evaluated on both an absolute and a comparative basis. Particular attention is given to the problem of specifying environmental flow requirements in Australia where the hydrology has distinctly different characteristics to those in countries where most of the models for prediction of instream flow requirements were developed. Broad recommendations as to the suitability and use of the different techniques for different conditions are provided.     

Individual and group determinants of employee absenteeism: Test of a causal model

This study examined whether an employee's level of absenteeism was affected by age, organizational tenure, perceptions of interactional justice, affective and continuance commitment, and the perceived absence norm in the employees' work unit or department. One hundred and sixty-six nursing and food services employees in a mid-size chronic care hospital provided attitudinal and perceptual data on an employee survey. Absence data (absence frequency and total days absent) were collected during the 12-month period immediately following an employee survey. Hypothesized relations between the various individual- and group-level factors and employee absenteeism were specified in a structural model and tested using LISREL 7 (Joreskog and Sorbom, 1989). General support was found for the study hypotheses.     

THROUGHFALL pH: EFFECT OF PRECIPITATION : TIMING AND AMOUNT1

ABSTRACT: Precipitation, throughfall, and stream pH were measured weekly over a 27-week period in 1982 on the Little Millseat watershed in eastern Kentucky. The average pH values over the study period were 4.3, 4.9, and 6.4, respectively, indicating significant buffering as water moved from the atmosphere, through the deciduous canopy, and through or over the soil to the stream. Regression analysis demonstrated that the timing and amount of precipitation were important factors influencing the pH of the throughfall. Weekly precipitation and the three-week average precipitation were statistically significant variables, explaining 53 percent of the variance in the observed through- fall pH. Precipitation pH was not a statistically significant variable for this watershed and sampling period.