Incorporating parametric uncertainty into population viability analysis models

Uncertainty in parameter estimates from sampling variation or expert judgment can introduce substantial uncertainty into ecological predictions based on those estimates. However, in standard population viability analyses, one of the most widely used tools for managing plant, fish and wildlife populations, parametric uncertainty is often ignored in or discarded from model projections. We present a method for explicitly incorporating this source of uncertainty into population models to fully account for risk in management and decision contexts. Our method involves a two-step simulation process where parametric uncertainty is incorporated into the replication loop of the model and temporal variance is incorporated into the loop for time steps in the model. Using the piping plover, a federally threatened shorebird in the USA and Canada, as an example, we compare abundance projections and extinction probabilities from simulations that exclude and include parametric uncertainty. Although final abundance was very low for all sets of simulations, estimated extinction risk was much greater for the simulation that incorporated parametric uncertainty in the replication loop. Decisions about species conservation (e.g., listing, delisting, and jeopardy) might differ greatly depending on the treatment of parametric uncertainty in population models.     

The causes of piping in a set of abandoned agricultural terraces in southeast Spain

This study aims to identify some of the factors contributing to the piping process in abandoned terraces in seven sites located in the Murcia Region (southeast Spain). The local landscape has the appearance of badland geomorphology, possessing deep valleys which until the 1970s were terraced and cultivated. The terraces have now been abandoned to the piping process. The research focuses on the relationship between the size and position of pipes and the physical and geochemistry properties of the local highly dispersive marl lithology; and the extent to which the reworking of the materials for terrace cultivation has exacerbated piping erosion.Morphologically, the terracing in the stream beds has resulted in a series of gentle benches separated by steeper risers with variable ‘drop’, (riser height). A series of flat infiltration surfaces result, and because the resculpting produces a reduced bulk density infill with enhanced throughflow, infiltrating water is forced along steep hydraulic gradients to a low outfall at the base of the riser.Paralleling studies of land levelling and terrace abandonment in similar materials elsewhere, piping in the study area is shown to be closely related to the physical and chemical characteristics of the materials its sodicity and dispersive character. Considerable differences in structure, texture, mineralogical composition and material's surface crust and subsoil geochemical properties emerged from ‘site signature’ plots, and these results suggest that agricultural processes affect the dispersive character of the crust materials, presumably because agricultural activity increases the buffering effect of organic acids on the dispersed clay. This is supported by the observation that on the one site that was levelled but not used for agriculture, a stable organically-distinct crust like the abandoned agricultural sites has not formed. The changes to the material's aggregate stability and bulk density properties when terracing occurs is examined, but insufficient evidence is available from the data collected to unpick the causes of aggregate stability changes in the study plots. The way in which differences between crust and subsoil enhance infiltration is discussed, and the role of the terrace ‘drop’ in influencing hydraulic gradients and pipe development is illustrated. A possible index to describe the relationship between evacuated material volumes and the controlling parameters discussed above is tested.It is concluded that terracing which is intended as a conservation practice has, in dispersive materials, actually enhanced piping, leading to the abandonment of farming.     

管网基本定理及其数学模型

本文讨论水力模型的基本形式和管网中管件的定理，以及在水力分析中的应用。作者提出了管网部件的概念，并给出管件的定义及其组合基本定理。并指出根据基本定理的两个重要参数－管件的比例系数和指数系数，可以唯一确定管件任一断面的幂函数数学。文中也讨论基本定理的应用和管网水力学分析方法。     

国内管道防腐涂料的比较研究

结合我国管道建设的实际情况,管道防腐成为我国能源战略的重要部分。管道腐蚀带来了严重的经济损失,环境污染,影响了人类的生存环境。本文论述了管道防腐涂料的技术水平,防腐涂料的品种、特点以及他们性能的评估与结果,并建议厂家加大投入,抓紧高品质防腐涂料的研制、开发与生产,以适应市场的需要。     

The role of demographic compensation theory in incidental take assessments for endangered species

Many endangered species laws provide exceptions to legislated prohibitions through incidental take provisions as long as take is the result of unintended consequences of an otherwise legal activity. These allowances presumably invoke the theory of demographic compensation, commonly applied to harvested species, by allowing limited harm as long as the probability of the species’ survival or recovery is not reduced appreciably. Demographic compensation requires some density-dependent limits on survival or reproduction in a species’ annual cycle that can be alleviated through incidental take. Using a population model for piping plovers in the Great Plains, we found that when the population is in rapid decline or when there is no density dependence, the probability of quasi-extinction increased linearly with increasing take. However, when the population is near stability and subject to density-dependent survival, there was no relationship between quasi-extinction probability and take rates. We note however, that a brief examination of piping plover demography and annual cycles suggests little room for compensatory capacity. We argue that a population’s capacity for demographic compensation of incidental take should be evaluated when considering incidental allowances because compensation is the only mechanism whereby a population can absorb the negative effects of take without incurring a reduction in the probability of survival in the wild. With many endangered species there is probably little known about density dependence and compensatory capacity. Under these circumstances, using multiple system models (with and without compensation) to predict the population’s response to incidental take and implementing follow-up monitoring to assess species response may be valuable in increasing knowledge and improving future decision making.     

Evidence-based decisions on the use of predator exclosures in shorebird conservation

Conservation practitioners often rely on experience rather than scientific evidence when making management decisions. These experience-based measures can waste limited time and funding if the given conservation practice is ineffective. Unanalyzed conservation strategies may negatively impact the species that is being protected. The use of predator exclosures to increase hatching success in ground-nesting shorebirds has been studied for almost two decades, yet their effectiveness is still debated. In ecosystems where predation pressure is particularly strong, electrified exclosures have been adopted; however, there are no studies on their efficacy or potential negative impacts. We conducted a nest survival analysis for 10 years (1998-2007) of piping plover monitoring data to determine: 1) the effectiveness of predator exclosures and electrified predator exclosures, and 2) conditions associated with nest abandonments at electrified exclosures. We found that predator exclosures significantly increase nest hatching success. Electrified exclosures can also be very effective at increasing hatching success under certain conditions, but at sites with high human disturbance and red fox densities, the proportion of exclosed nests that are abandoned by parental adults becomes sizeable. The direct cause of nest abandonments remains unclear since fox behavior on beaches and the dynamics of foxes and plovers at exclosures have not been studied. Our results suggest that such information is necessary if conservation practitioners can make more informed use of this direct management measure.     

A quantitative framework to evaluate incidental take and endangered species population viability

Incidental take is the permitted unintended or collateral killing, harassment, or habitat destruction of a protected species under endangered species law and is permissible as long as the take does not jeopardize the species’ persistence in the wild. However, take is seldom addressed in a quantitative or population modeling context and the criterion of “jeopardy” has no universal, quantitative definition. To model the effect of incidental take on population viability, we modified an existing population model and simulated abundance, population growth, and quasi-extinction probability (the probability of falling below a predetermined abundance threshold) for Piping Plovers (Charadrius melodus) in the Great Plains, USA. The model incorporated environmental stochasticity and variation due to sampling variance. Eggs and chicks were taken out of the population as a “harvest” to simulate incidental take that currently occurs in the Missouri River system. We used least-squares regression and an AIC model selection approach to evaluate the population’s elasticity to incidental take covariates. Even in the absence of take the population declined by 7.5% annually. Population growth and final abundance were reduced and the probability of quasi-extinction was increased in simulations where egg take and chick take were applied. The model selection analysis indicated that incidental take of eggs and chicks depresses population viability and the probability of recovery of Piping Plovers in the Great Plains. Though the model was useful in putting take and jeopardy in a quantitative setting, the question remains as to whether permitted levels of take causes jeopardy for Piping Plovers since there are no decision standards defined by the USFWS. However, evaluating take in a quantitative framework, as we have, will make jeopardy decisions more explicit in terms of viability and recovery metrics.     

东北地区越冬日光温室蔬菜滴灌技术的应用

近年来东北地区日光温室种植蔬菜采用滴灌技术越来越多,本文通过日光温室滴灌设备的推广使用,简述大棚蔬菜滴灌系统的布局、管网设计、安装及应用效果。     

吉林省两种鸟类新纪录

红腹滨鹬和东方行乌均属鹆形目的小型水鸟,在吉林省一直没有记录。2009年5月在莫莫格国家级自然保护区大岗林场记录到了东方鹆,还记录到了卵与巢。8月在查干南泡记录到了红腹滨鹬。填补了这2种鸟在吉林省分布的空白。     

The effects of heat stress, predation risk and parental investment on Malaysian plover nest return times following a human disturbance

Waders leave nests and conduct distractive displays when approached by people. The time taken for waders to return to nests depends on numerous factors that affect the costs and benefits of incubation and anti-predator behavior. Understanding this trade-off may help assess the reproductive consequences of different nest return times and identify variables to consider in breeding disturbance studies. We subjected 73 Malaysian plover (Charadrius peronii) nests to standardized human disturbances and an analysis of covariance was used to determine how weather, time of day, embryonic age, weeks into breeding season and nest attendance (proportion of time adults incubated nests) influence nest return times. Egg temperatures were estimated using a regression model that predicted the temperature inside unshaded eggs from air temperature, cloud cover and time of day (r² = 0.88). We assessed the relationship between nest return times and hatch success. Plovers returned to nests faster at higher modeled egg temperature (P = 0.010), in the morning (P = 0.003), if they had younger clutches (P = 0.038), and if they had high nest attendance prior to the disturbance (P = 0.015). Pairs that returned to nests faster had lower hatch success (P = 0.021). This may be because pairs that spend more time distracting humans may also do so for predators. These results suggest that short nest return times may not indicate low fitness costs of disturbance. The thermal and predation environment in addition to nest return times should be taken into account when assessing the deleterious effects of human disturbance.