念青唐古拉山西段小冰期以来冰川变化

小冰期是指15世纪到20世纪早期之间一系列相对寒冷的气候波动阶段,研究小冰期以来的冰川规模变化,对于了解百年尺度上冰川变化及其气候指示意义具有重要意义。利用Google Earth和Arc GIS10.3研究了念青唐古拉山西段的现代冰川和小冰期冰川,统计了冰川的基本信息和小冰期以来的变化情况,分析了面积、高程、坡度和坡向因素对冰川变化的影响,探讨了平衡线高度变化的气候指示意义。结果表明:念青唐古拉山西段共发育现代冰川847条,总面积约689.71 km~2,共识别出小冰期冰川306条,总面积约746.12 km~2。小冰期以来冰川面积减少约31%,平衡线高度平均上升约58 m,冰川的面积、坡度和高程对冰川面积变化的解释率为71%,平衡线高度变化与印度季风关系密切。     

Complex dynamics of the population with a simple age structure

The effects of the following modes of density-dependent control of population growth: density-dependent birth rate, adult survival rate, juvenile survival rate are compared based on the mathematical model of population dynamics. It is shown that the most efficient mechanisms limiting population size are decreasing with the growth of the adult population birth rate and/or the decreasing survival rate of the offspring with the increase in their number. However, these same mechanisms are responsible for oscillations of the population size and its chaotic change. The density-dependence of the adult survival rate is not efficient in constraining the population growth, but it can substantially limit the magnitude of oscillations of the population size.     

On the importance of life history and age structure in biological invasions

The age specific patterns of reproduction and mortality dictated by the life history of an organism apply to potential invaders as well as resident species of an area, but whether certain life history traits are more invasive than others is an unresolved issue. We analyze a two-population system of an invading and a resident species and test the effects of age on the probability to invade when the organisms are iteroparous or semelparous. The life history characteristics of the populations are projected in Leslie matrices, and the probability that the invader exceeds different population sizes is calculated by Monte Carlo analysis. The simulations show that (a) the invasion probability of an iteroparous organism increases with age until the individuals introduced are mature for first reproduction, and then becomes independent of age; (b) the invasion probability is more age sensitive for iteroparous organisms with high juvenile mortality (Type III organisms) than for those with a lower (Type I); (c) invading semelparous organisms are most affected by competition from resident organisms; (d) variations in vital rates of semelparous residents have greater influence on the invasion probability of an iteroparous organism than variations in traits of the invader.     

Comparative study of the age and location dependence of some heavy metals in human hair from two Nigerian cities

The concentration of some heavy metals (lead, zinc and copper) were determined in the scalp hair of children (1–15 year) and active adults (16–40 year) in two Nigerian cities. The levels of zinc were found to be higher in children than in the adult population. There was a significant difference (P?=?0.05) between the two age groups. The levels of copper were all within the same range for the two age groups and independent of location. The levels of lead were generally higher in adults than in children. However, there was no significant difference (P?=?0.05) in the average concentrations of lead between the children and adult populations of the two cities. The regression analysis indicated a strong correlation (r?=?0.86) between zinc and copper.     

The fire frequency analysis branch of the pyrostatistics tree: sampling decisions and censoring in fire interval data

Statistical characterization of past fire regimes is important for both the ecology and management of fire-prone ecosystems. Survival analysis—or fire frequency analysis as it is often called in the fire literature—has increasingly been used over the last few decades to examine fire interval distributions. These distributions can be generated from a variety of sources (e.g., tree rings and stand age patterns), and analysis typically involves fitting the Weibull model. Given the widespread use of fire frequency analysis and the increasing availability of mapped fire history data, our goal has been to review and to examine some of the issues faced in applying these methods in a spatially explicit context. In particular, through a case study on the massive Cedar Fire in 2003 in southern California, we examine sensitivities of parameter estimates to the spatial resolution of sampling, point- and area-based methods for assigning sample values, current age surfaces versus historical intervals in generating distributions, and the inclusion of censored (i.e., incomplete) observations. Weibull parameter estimates were found to be roughly consistent with previous fire frequency analyses for shrublands (i.e., median age at burning of ~30–50 years and relatively low age dependency). Results indicate, however, that the inclusion or omission of censored observations can have a substantial effect on parameter estimates, far more than other decisions about specifics of sampling.

Accumulation of trace elements in the peripheral and central parts of two species of epiphytic lichens transplanted to a polluted site in Portugal

This paper compares the dynamics, i.e. the rates of change in element concentrations of young and older lichen thallus parts, of one foliose and one fruticose lichen, during a transplant experiment to a polluted site. Both lichen parts respond to environmental changes. Here, differential accumulation suggests that differential constitution leads to differential uptake and release, and/or the overall behaviour is partly due to internal translocation and regulation mechanisms within the whole lichen. For thallus parts, internal translocation should be taken into account as one more factor affecting lichen “memory length”. Young parts of the thallus presented higher rates of change, but different lichen parts accumulate different elements to different extents. Therefore tissue selection in monitoring may depend on the element of interest, and cannot be made into a generalized approach in survey set-ups: the choice depends on the element.     

基于地理探测器的湖南新石器时期聚落遗址人居环境适宜度评价

湖南地区是长江中游新石器时期文化发源地之一,为了更有效地了解新石器时期的人地关系,以高程、坡度、坡向、水体、地貌、土壤和植被类型这7个指标构建新石器时期聚落遗址人居环境模糊指数综合评价体系,运用地理探测器的因子探测法确定各要素的权重,在ArcGIS中将各因子的权重值进行加权叠加和综合等级类型分类,最终得到湖南新石器时期聚落遗址人居环境适宜度评价结果:宜居度中等以上的区域面积最大,总面积为18.59万km2,占湖南省总面积的87.77％;水体权重值占比最高;古人偏爱聚水而居,且集中分布在洞庭湖区域,湘、资、沅、澧周边沿干流分布或在河流的交汇区域分布;适宜度等级较高的遗址类型偏向于丘陵型、台地型和平原型;宜居度中等及以上的遗址多分布在地形较低、朝南、微斜坡、地貌、土壤和植被类型最为丰富的区域.本文可为今后史前聚落遗址分布与自然环境分析提供借鉴意义.     

农业对小冰期和现代我国七月气候的影响模拟

小冰期是数千年来最引人注目的一个冷期,也是近百年变暖的直接历史背景,该时期我国农业扩展范围已与现代相差无几。自然植被被农业植被替换,对区域水循环和气候变化都产生影响。比较冷暖时期该类影响之差别,有利于认识土地覆盖与气候的联系。文中利用全球和区域气候模式,考察小冰期和现代两种全球背景下我国区域土地覆盖变化对七月平均气候状况的影响。结果表明：小冰期夏季偏冷地区主要在北方,农业具有减缓小冰期大尺度降温的效应,而在较温暖且温度变化较小的华南和华中地区,农业则起一定的降温效应；农业对现代气候下的降水影响不大,但在小冰期背景下却导致降水减少     

Sexual selection and mating system in Zorotypus gurneyi Choe (Insecta: Zoraptera)

Body size is clearly an important factor influencing the outcome of agonistic contests, but is often weakly correlated with dominance ranks in Zorotypus gurneyi Choe (Insecta: Zoraptera). The study of the development and dynamics of dominance relations using artificially constructed colonies show that age, or tenure within the colony, is the prime determinant of dominance among males. Dominance hierarchies become relatively stable within 2 or 3 days and males that emerge later normally begin at the bottom of the hierarchy regardless of size. Males interact much more frequently when they are simultaneously introduced to each other than when they are allowed to emerge at different times. In the latter case, males that emerge late appear to recognize relative dominance of older males and avoid direct contests. Considering the high correlation between dominance rank and mating success, there is a strong selective advantage to males that emerge earlier and such pressure of sexual selection may be responsible for the difference in life history strategies between Z. gurneyi and its sympatric congener, Z. barberi Gurney, in central Panama.     

Driver aging and its effect on male and female single-vehicle accident injuries: some additional evidence

INTRODUCTION: This study explores the differences in injury severity between male and female drivers, and across the different age groups, in single-vehicle accidents involving passenger cars. METHOD: Given the occurrence of an accident, separate male and female multinomial logit models of injury severity (with possible outcomes of no injury, injury, and fatality) were estimated for young (ages 16 to 24), middle-aged (ages 25 to 64), and older (ages 65 and older) drivers. RESULTS: The estimation results show statistically significant differences in the factors that determine injury-severity levels between male and female drivers and among the different driver age groups. CONCLUSIONS: We discuss a number of plausible explanations for the observed age/gender differences and provide suggestions for future work on the subject. IMPACT ON INDUSTRY: A better understanding of age and gender differences can lead to improvements in vehicle and highway design to minimize driver injury severity. This paper provides some new evidence to help unravel this complex problem.