Factors influencing the characteristics of fish assemblages in a large subtropical marine embayment

Mean number of species and density of fishes in nearshore shallow waters of Shark Bay, a large subtropical embayment, were c . seven and 19.5 times greater in seagrass than over bare sand, where protection from predators and the abundance of potential invertebrate prey were less. The number of fish species and density of fishes over bare sand were lower in nearshore than offshore waters, where there was a greater amount of organic material and thus presumably a greater density of benthic macroinvertebrate prey. Species composition in vegetated and unvegetated habitats differed markedly, with species such as Monacanthus chinensis, Apogon rueppellii and Pelates quadrilineatus being largely confined to seagrass, whereas others such as Pseudorhombus jenynsii, Torquigener whitleyi and Engyprosopon grandisquama were found predominantly or exclusively over bare sand. The ichthyofauna in beds of Posidonia australis , in which the canopy is uniformly dense, differed in composition and comprised a greater number of species and density of fishes than that in Amphibolis antarctica , in which an open space is present beneath the terminal clusters of relatively short leaves. Species composition in the beds of both of these seagrass species underwent well defined cyclical changes, caused by out-of-phase sequential changes in the densities of certain species. Such changes were less common over bare sand, where the ichthyofaunal composition was more variable. The number of species and density of fishes over bare sand were greater at night than during the day, reflecting, in part, a tendency for species such as A. rueppellii to move into unvegetated areas to feed at night, when the likelihood of predation by visual predators would be reduced. Within Shark Bay, ichthyofaunal composition is influenced most by habitat type (vegetated v . unvegetated), followed in general by water depth and then region in the bay and time of year.     

Postmortem Changes in Binding to the Muscarinic Receptor from Human Cerebral Cortex

Abstract: The effects of storage at 4°C on the antagonist and agonist binding properties of the muscarinic acetyl-choline receptor from fresh surgical and frozen autopsy samples from human cerebral cortex were studied. The number of 1-[³H]3-quinuclidinyl benzilate binding sites and their affinities were stable up to 51 h, both when stored as pieces of intact nonfrozen tissue and as a homogenate. The agonist binding properties as measured by the ability of the muscarinic agonist carbachol to compete with l-[³H]3-quinuclidinyl benzilate were also stable up to 51 h when the tissue was stored in the form of pieces. The affinity for carbachol decreased when the tissue was stored as a homogenate. The frozen autopsy samples showed no significant differences in binding properties in comparison with fresh neurosurgical tissue.     

美洲大蠊乙醇提取物对香烟引起小鼠肺脏氧化应激的干预效果研究

美洲大蠊提取物具有显著的抗肿瘤、抗菌和抗肝纤维化等作用,但是,其对肺脏抗氧化应激效果的研究未见报道,本文主要探讨美洲大蠊乙醇提取物对熏烟小鼠血液和肺脏抗氧化应激的效果.选用雌性KM小鼠28只,随机分为对照组、熏烟组、低剂量和高剂量美洲大蠊醇提物组各7只,除对照组灌胃生理盐水外,其他各组每天中午和下午采用烟熏处理,持续3...     

安宁河流域稻米生化品质与气候条件的关系

通过“合系39”在四川安宁河流域无控制的地理分期播种大田试验及稻米生化品质室内分析,定量研究了从穗前40d到成熟期各阶段气象条件对稻米生化品质的影响及关键时期,建立了稻米生化品质各组分与关键期平均温度、温度日较差和日照时数的综合关系模型．结果表明,气候生态条件对稻米生化品质各组分有重要影响,且不同组分的影响形式和关键时期不同．其组分与气候生态因子最显著相关的时段或在齐穗前,或在齐穗后,或从齐穗前持续到齐穗后．该模型于2002～2003年应用在安宁河流域优质稻生产决策中．累计推广优质稻7．3×10^4hm^2,较2001年增加3．0×10^4hm^2,农民增收2亿元,促进了优质稻的迅速发展．     

High and dry: post‐fire tree seedling establishment in subalpine forests decreases with post‐fire drought and large stand‐replacing burn patches

Aim Climate warming and increased wildfire activity are hypothesized to catalyse biogeographical shifts, reducing the resilience of fire‐prone forests world‐wide. Two key mechanisms underpinning hypotheses are: (1) reduced seed availability in large stand‐replacing burn patches, and (2) reduced seedling establishment/survival after post‐fire drought. We tested for regional evidence consistent with these mechanisms in an extensive fire‐prone forest biome by assessing post‐fire tree seedling establishment, a key indicator of forest resilience. Location Subalpine forests, US Rocky Mountains. Methods We analysed post‐fire tree seedling establishment from 184 field plots where stand‐replacing forest fires were followed by varying post‐fire climate conditions. Generalized linear mixed models tested how establishment rates varied with post‐fire drought severity and distance to seed source (among other relevant factors) for tree species with contrasting post‐fire regeneration adaptations. Results Total post‐fire tree seedling establishment (all species combined) declined sharply with greater post‐fire drought severity and with greater distance to seed sources (i.e. the interior of burn patches). Effects varied among key species groups. For conifers that dominate present‐day subalpine forests (Picea engelmannii, Abies lasiocarpa), post‐fire seedling establishment declined sharply with both factors. One exception was serotinous Pinus contorta, which did not vary with either factor. For montane species expected to move upslope under future climate change (Larix occidentalis, Pseudotsuga menziesii, Populus tremuloides) and upper treeline species (Pinus albicaulis), establishment was unrelated to either factor. Greater post‐fire tree seedling establishment on cooler/wetter aspects suggested local topographic refugia during post‐fire droughts. Main conclusions If future drought and wildfire patterns manifest as expected, post‐fire tree seedling establishment of species that currently characterize subalpine forests could be substantially reduced. Compensatory increases from lower montane and upper treeline species may partially offset these reductions, but our data suggest important near‐ to mid‐term shifts in the composition and structure of high‐elevation forests under continued climate warming and increased wildfire activity.     

哈克地区全新世生态环境演变与人类文化的发展轨迹

哈克遗址是呼伦贝尔地区一处重要的细石器遗址,对划分和确立东北地区细石器文化的类型及其渊源具有重要的价值。遗址位于海拉尔河东、北、南三面环绕而形成的半封闭式高平台小岛上,自下而上基本存在着四个时期的文化堆积,其中,包含细石器文化遗存的堆积物的厚度最大。岩性、岩相、碳酸钙含量检测和植物孢粉分析等方面的综合信息表明,全新世以来地层垂直沉积和气候变迁波动是同步发展的。人类依环境优劣而留居或迁徙,其文化发展从早到晚经历了新石器、辽至蒙元、明清时期的历史演变,变化始终伴随着气候的波动,表现出以适应为特征的生存与繁衍轨迹。     

THIS ARTICLE HAS BEEN RETRACTED: What caused the mid‐Holocene forest decline on the eastern Tibet‐Qinghai Plateau?

Aim Atmospheric CO₂ concentrations depend, in part, on the amount of biomass locked up in terrestrial vegetation. Information on the causes of a broad‐scale vegetation transition and associated loss of biomass is thus of critical interest for understanding global palaeoclimatic changes. Pollen records from the north‐eastern Tibet‐Qinghai Plateau reveal a dramatic and extensive forest decline beginning c. 6000 cal. yr bp . The aim of this study is to elucidate the causes of this regional‐scale change from high‐biomass forest to low‐biomass steppe on the Tibet‐Qinghai Plateau during the second half of the Holocene. Location Our study focuses on the north‐eastern Tibet‐Qinghai Plateau. Stratigraphical data used are from Qinghai Lake (3200 m a.s.l., 36°32′–37°15′ N, 99°36′–100°47′ E). Methods We apply a modern pollen‐precipitation transfer function from the eastern and north‐eastern Tibet‐Qinghai Plateau to fossil pollen spectra from Qinghai Lake to reconstruct annual precipitation changes during the Holocene. The reconstructions are compared to a stable oxygen‐isotope record from the same sediment core and to results from two transient climate model simulations. Results The pollen‐based precipitation reconstruction covering the Holocene parallels moisture changes inferred from the stable oxygen‐isotope record. Furthermore, these results are in close agreement with simulated model‐based past annual precipitation changes. Main conclusions In the light of these data and the model results, we conclude that it is not necessary to attribute the broad‐scale forest decline to human activity. Climate change as a result of changes in the intensity of the East Asian Summer Monsoon in the mid‐Holocene is the most parsimonious explanation for the widespread forest decline on the Tibet‐Qinghai Plateau. Moreover, climate feedback from a reduced forest cover accentuates increasingly drier conditions in the area, indicating complex vegetation–climate interactions during this major ecological change.     

Age-related changes of structures in cerebellar cortex of cat

We studied the structures of the cerebellar cortex of young adult and old cats for age-related changes, which were statistically analysed. Nissl staining was used to visualize the cortical neurons. The immunohistochemical method was used to display glial fibrillary acidic protein (GFAP)-immunoreactive (IR) astrocytes and neurofilament-immunoreactive (NF-IR) neurons. Under the microscope, the thickness of the cerebellar cortex was measured; and the density of neurons in all the layers as well as that of GFAP-IR cells in the granular layer was analysed. Compared with young adult cats, the thickness of the molecular layer and total cerebellar cortex was significantly decreased in old cats, and that of the granular layer increased. The density of neurons in each layer was significantly lower in old cats than in young adult ones. Astrocytes in old cats were significantly denser than in young adult ones, and accompanied by evident hypertrophy of the cell bodies and enhanced immunoreaction of GFAP substance. Purkinje cells (PCs) in old cats showed much fewer NF-IR dendrites than those in young adults. The above findings indicate a loss of neurons and decrease in the number of dendrites of the PCs in the aged cerebellar cortex, which might underlie the functional decline of afferent efficacy and information integration in the senescent cerebellum. An age-dependent enhancement of activity of the astrocytes may exert a protective effect on neurons in the aged cerebellum     

Responses of radial growth and stable carbon isotopes to climate in the northern Tianshan Mountains

Climate change has profound effects on forest ecosystems. Schrenk spruce (P. schrenkiana) is a natural conifer species endemic to the arid inland areas of Asia. In this study, the relationship between tree-ring parameters of P. schrenkiana and major meteorological factors were analyzed, and the main limiting factors for tree radial growth and stable carbon isotope fractionation were explored. Our results indicate that moisture stress before and during the growing season have an important influence on radial growth of P. schrenkiana, especially, the correlation coefficient between tree-ring width and vapor pressure deficit (VPD) from previous August to current July is as high as −0.622 (n = 51, p < 0.01). Collinearity analysis further supports the conclusion that the limiting factor for the radial growth of P. schrenkiana is moisture. Although the correlation analysis results show that the tree-ring δ¹³C_corr is significantly positively correlated with sunshine duration (SD), additional analysis based on first order difference variables suggests that the climate factor may not be the only limiting factor for the stable carbon isotope fractionation of tree rings in the Sayram Lake Basin. This lays the foundation for the assessment of forest management practices and carbon sink capacity in light of future climate change.