绿色屋顶径流氮磷浓度分布及赋存形态

为了解绿色屋顶暴雨径流的氮磷浓度分布及赋存形态,在重庆大学构建了两种绿色屋顶,于2009年9月至2011年10月期间进行了绿色屋顶和对照屋面的暴雨径流水质监测。研究结果表明,绿色屋顶暴雨径流pH值在7.7左右,氨氮浓度满足地表水环境质量标准Ⅲ类标准;总氮、总磷、硝酸根的平均浓度分别为3.6—4.4 mg/L、0.17—0.28 mg/L和3.1—3.7 mg/L,均高于降雨雨水浓度;与对照屋面暴雨径流相比,同时期的绿色屋顶暴雨径流中总氮、氨氮和总磷浓度较低,而硝酸根、磷酸根浓度较高。绿色屋顶暴雨径流水质的季节差异明显,夏季污染物浓度较低,而春秋季节污染物浓度较高;总体上看,随绿色屋顶运行时间的延长,暴雨径流中总氮和硝酸根浓度逐渐降低,而总磷和磷酸盐浓度则呈现出一定的波动性。气象因素、降雨雨水水质与绿色屋顶暴雨径流水质的相关性分析表明,气温越高、前期干旱时间越长,越有利于绿色屋顶径流中氨氮浓度的降低;绿色屋顶径流中的总磷和氨氮主要来自降雨。研究结果为绿色屋顶的科学构建和城市暴雨径流管理提供了重要参考。     

Seed dynamics linked to variability in movement of tidal water

Question: Community structure may be influenced by patterns of dispersed seeds (seed rain) because they contribute to the template of plant community development. We explored factors influencing seed rain in a system dominated by tidal water, where direction and magnitude of water flow are difficult to predict, unlike many other hydrochorous systems where water flow is directional. We posed three main questions: (1) are patterns in seed rain linked to effects of hydrodynamic variability; (2) do these patterns in seed rain reflect distribution of seed sources and seed production; and (3) what are the implications for the assembly of tidal communities? Location: Salt marshes on the Wadden island of Schier‐monnikoog, The Netherlands. Methods: Species compositions of vegetation, seed rain, seed production and driftlines along a chronosequence of communities were compared. We also studied seed movement by sowing Astroturf® mats with seeds and checking for seeds remaining after a single tidal inundation. Results: Storm surges had a significant effect on seed‐rain patterns as the highest density and diversity of captured seeds were found during a stormy period. Seed rain of the youngest communities was more influenced by storms than that of older communities. Patterns in seed rain generally followed similar patterns in the distribution of established plants, and seed production. Conclusions: Results suggested mostly local dispersal of seeds. However, there was some evidence of long‐distance dispersal occurring during storm surges in younger communities that are regularly inundated with tidal water. The possible role of seed retention in constraining community development, rather than dispersal per se, is further discussed.     

Effects of the occurrence of a cyclone and the dominance of a bamboo species on the dynamics of subtropical forest fragments

With the intensification of global warming, the occurrence of large‐scale natural events is becoming even more common in tropical regions, which can impact the structure of plant communities. In this study, we evaluated the isolated and combined effects of an extratropical cyclone and the dominance of a native bamboo species (Merostachys skvortzovii) on floristic composition, diversity, demographic rates and the increment of trees in Atlantic Forest fragments in Southern Brazil. In 2014 (T1) and 2016 (T2), we sampled 56 plots of 200 m² for the effects of an extratropical cyclone in 2009 (T0). We also evaluated another 60 plots of the same size not in the direct path of this cyclone. Half of the plots in each group were covered by dense groupings of bamboos, as a result of past human activities, which could potentially limit natural regeneration. We observed an increase in richness and diversity indices (H′ and 1/D) from the first (T0) to the following assessments (T1 an T2) on the sites affected by the cyclone, when compared to non‐affected sites. After the cyclone, both density and basal area they decreased, but there was an increase in recruitment, mortality, turnover rates and basal area, as well as basal increment. The diameter increment on surviving individuals was higher in cyclone‐affected sites than in non‐affected sites. Bamboo cover did not affect richness or demographic rates (except mortality between T0 and T1). Natural impacts of this nature can lead to significant alterations of demographic rates, allowing the input of new species and influencing the pace of demographic processes.     

Venom effects on monoaminergic systems

The monoamines, dopamine, epinephrine, histamine, norepinephrine, octopamine, serotonin and tyramine serve many functions in animals. Many different venoms have evolved to manipulate monoaminergic systems via a variety of cellular mechanisms, for both offensive and defensive purposes. One common function of monoamines present in venoms is to produce pain. Some monoamines in venoms cause immobilizing hyperexcitation which precedes venom-induced paralysis or hypokinesia. A common function of venom components that affect monoaminergic systems is to facilitate distribution of other venom components by causing vasodilation at the site of injection or by increasing heart rate. Venoms of some scorpions, spiders, fish and jellyfish contain adrenergic agonists or cause massive release of catecholamines with serious effects on the cardiovascular system, including increased heart rate. Other venom components act as agonists, antagonists or modulators at monoaminergic receptors, or affect release, reuptake or synthesis of monoamines. Most arthropod venoms have insect targets, yet, little attention has been paid to possible effects of these venoms on monoaminergic systems in insects. Further research into this area may reveal novel effects of venom components on monoaminergic systems at the cellular, systems and behavioral levels.     

Ovarian follicular differentiation with prepubertal gonadotropin surges and gonadotropin priming in mice

Preantral follicles were mechanically isolated from the ovaries of 1.5 to 8 week old mice and cultured in vitro for 4 days in the presence or absence of either activin A or FSH. Plasma gonadotropin, estradiol and immunoreactive (IR) inhibin levels were measured. Cultured follicles showed stepwise changes in response to recombinant human (rh) FSH, with no response until 11 days, a gradual increase from 2 weeks, culminating in a strong response to rhFSH at 8 weeks. The response to activin A was vice versa. It enhanced the effect of rhFSH on preantral follicular growth of up to 4-week-old mice, but inhibited the effect of rhFSH in 8-week-old mice. The peak of the prepubertal gonadotropin surge was observed on day 11. Seven-day-old mice were treated with either luteinizing hormone releasing hormone (LHRH) or rhFSH or human chorionic gonadotropin (hCG) for 3 consecutive days from day 7, and follicles were collected on day 11. Those follicles showed enhanced response to rhFSH, no response to activin A, and an enhanced response to the combination of rhFSH and activin A, suggesting that the chronological changes in follicular response are a result of the prepubertal gonadotropin surge.     

Sequential patterns of colonization of coarse woody debris by Ips pini (Say) (Coleoptera: Scolytidae) following a major ice storm in Ontario

Abstract

• 1 It is widely known that many bark and wood‐boring beetle species use nonresistant coarse woody debris (CWD) created by disturbances; however, the ability of these secondary species to cause mortality in healthy trees following a build‐up of their populations remains unclear. We characterized the pattern of colonization by Ips pini (Say) following a major ice storm that created large amounts of CWD varying in resistance to colonization (i.e. ranging from snapped tops with no resistance to heavily damaged trees with intact root systems). A major question was how the beetles responded to the different types of storm‐damaged material and whether healthy undamaged trees were colonized and killed following increases in beetle populations.
• 2 Six red pine, Pinus resinosa Ait., plantations in eastern Ontario were monitored from 1998 to 2001 inclusive: three with high storm damage (approximately 120 m³/ha CWD) and three with minimal damage (approximately 20 m³/ha CWD). Transects (200 × 2 m) were sampled yearly in each plantation to assess the type and amount of damaged pine brood material colonized by the pine engraver beetle, I. pini.
• 3 Beetles preferentially infested the most nonresistant material available each year (i.e. all snapped tops in year 1, all standing snags, up‐rooted trees and many bent trees by year 2, but still less than 50% of trees blown over but with intact root systems by year 3). By years 3 and 4, the majority (approximately 75%) of severely damaged trees (with > 50% crown loss) died prior to beetle colonization.
• 4 The size of the beetle population tracked the abundance of available woody material from year‐to‐year within a plantation; populations were very large in the first 2 years, and declined significantly in the last 2 years.
• 5 Healthy standing red pines were apparently resistant to colonization by the beetles, despite the significant build‐up in their populations. Hence, the results of the present study suggest that native bark beetle populations will not cause further tree mortality following such a disturbance in this region.

     

A potential role of modulating inositol 1,4,5-trisphosphate receptor desensitization and recovery rates in regulating ovulation

Regulation of the human menstrual cycle is a frequency dependent process controlled in part by the pulsatile release of gonadotropin releasing hormone (GnRH) from the hypothalamus. The binding of GnRH to gonadotroph cells in the pituitary stimulates inositol 1,4,5-trisphosphate (IP3) mediated release of calcium from the endoplasmic reticulum, resulting in calcium oscillations and the secretion of luteinizing hormone (LH). A sudden increase in serum LH concentrations known as the LH surge triggers ovulation. Here we model the intracellular calcium dynamics of gonadotroph cells by adapting the model of Li and Rinzel (J. Theor. Biol. 166 (1994) 461) to include the desensitization of IP3 receptors to IP3. Allowing the resensitization rate of these receptors to vary over the course of the cycle suffices to explain the LH surge in both the normal menstrual cycle, and in the treatment of Kallmann's syndrome (a condition where endogenous production of GnRH is absent).     

山东半岛滨海沙滩前缘的野生植物

滨海沙滩是以海水影响为基本过程的地貌类型,适应这种环境的植物类群与适生于内陆的沙地植物可能存在巨大差别。在野外调查的基础上,分析了山东半岛滨海沙滩前缘的植物种类及其种间关系。结果表明：（1）滨海沙滩前缘具有独特的优势种库,包括沙钻苔草（Carex kobomugi）、肾叶打碗花（Calystegia soldanella）、粗毛鸭嘴草（Ischaemum bartatum）、单叶蔓荆（Vitex trifolia var.simplicifolia）、矮生苔草（Carex pumila）和沙引草（Messerschmidia sibirica）等;（2）优势种库的成员都是潜在优势种,它们之间主要呈抑制效应,对库外物种几乎没有抑制效应,甚至有互补或互利效应。在进化过程中,这些潜在优势种可能已适应风暴潮的干扰,不会因受风暴潮灾害而灭亡。当植物适应风暴潮后,滨海沙滩不再是灾难环境,反而变为适宜生境。为持续利用这些物种,不仅要保护其赖以生存的天然生境,还要开展引种栽培,消除人们对野生资源的采挖动机。根据物种间的天然联系,栽培时宜将具有互利或互补关系的物种间混种植,不宜将具有抑制关系的物种间混种植。     

沙尘暴的危害及农业防治措施

沙尘暴是一种灾害性天气现象,它的发生与地表植被状况有密切关系,冬春季节农田裸露和退化草地植被覆盖度低是沙尘暴的主要沙尘来源,采用农业措施整治裸露农田和退化草地是沙尘源治理的关键。本文从沙尘暴的时空分布特征、沙尘暴成因、沙尘暴的危害和沙尘暴的农业防治措施等方面进行了论述,强调了以农业措施作为沙尘源治理技术核心的观点。农业措施主要包括:(1)调整农业种植结构,改变北方目前单一的种植方式,推广粮草混作技术、粮草间作套种、草田轮作,将牧草和越冬作物(冬小麦、冬牧70黑麦等)引入农田耕作系统,增加农田冬春季节的地表覆盖;(2)推广保护性耕作制度,通过免耕、提高留茬量和留茬高度,增加冬春季根茬固土能力和地表秸秆覆盖;(3)加强草原保护和建设,通过严禁新的草原开垦,严格限制超载放牧,禁止滥采滥挖,推广分区轮牧和舍饲圈养,加大围栏封育的力度等措施恢复和重建草原植被;(4)发展集约化农牧业,推广集约化种植和养殖技术,把人们的生产活动集中在条件较好的土地上,减少沙化农田和草地压力。