夏季两种类型高温特征对比和舒适度评价

对上海金山1981—2010年湿热型高温和干热型高温的基本特征以及背景场特征进行分析,并结合人体舒适度讨论两类高温对人们生活工作影响的特点和规律。结果表明:1干热型高温由强大副高控制,地面处于高压顶后或顶前的晴空区;湿热型高温由较强副高控制,地面多处于低压底部,易受水汽影响。2干热年较湿热年,西太平洋副高偏西、偏强,南亚高压偏东、偏北、偏强,夏季风较强,尤其是南风分量偏强显著,下沉运动偏强。3湿热年纬圈方向900hPa以下为上升运动,利于对流活动的发生。4两类高温皆有全天持续热不舒适特点,白天湿度作用明显,湿热型高温持续极热特征突出,严重不舒适感强烈;夜间主要受温度影响,干热型高温造成不舒适感较大。     

Holocene Amazon rainforest–savanna dynamics and climatic implications: high‐resolution pollen record from Laguna Loma Linda in eastern Colombia

We present a high‐resolution pollen record of a 695‐cm‐long sediment core from Laguna Loma Linda, located at an altitude of 310 m in the transitional zone between the savannas of the Llanos Orientales and the Amazonian rainforest, about 100 km from the Eastern Cordillera. Based on eight AMS ¹⁴C ages, the record represents the last 8700 ¹⁴C yr BP. During the period from 8700 to 6000 ¹⁴C yr BP the vegetation was dominated by grass savanna with only a few woody taxa, such as Curatella and Byrsonima, present in low abundance. Gallery forest along the drainage system apparently was poorly developed. Compared with today, precipitation must have been significantly lower and seasonality stronger. During the period from 6000 to 3600 ¹⁴C yr BP, rainforest taxa increased markedly, reflecting an increase in precipitation. Rainforest and gallery forest taxa such as Moraceae/Urticaceae, Melastomataceae, Alchornea, Cecropia and Acalypha, were abundant, whereas Poaceae were reduced in frequency. From 3600 to 2300 ¹⁴C yr BP rainforest taxa continued to increase; Moraceae/Urticaceae became very frequent, and Myrtaceae and Myrsine became common. Savanna vegetation decreased continuously. We infer that precipitation was still increasing, and that the length of the annual dry period possibly shortened. From 2300 ¹⁴C yr BP onwards, grass savanna (mainly represented by Poaceae) expanded and Mauritia palms became frequent. This reflects increased human impact on the vegetation. Copyright © 2000 John Wiley & Sons, Ltd.     

我国海岸带环境蠕变问题的若干事实及其适应性研究

综述了我国海岸带环境蠕变问题的若干事实,如海平面上升、海水入侵、海岸侵蚀及风暴潮等灾害加剧,海洋污染,赤潮频发,渔业资源衰退,红树林遭受破坏,珊瑚礁生态环境退化,海草床生态环境退化以及滨海湿地锐减等。探讨了我国海岸带环境蠕变问题适应性研究体系的建立及未来亟待开展的研究工作。     

Fish assemblages in Tanzanian mangrove creek systems influenced by solar salt farm constructions

Deforestation of mangrove forests is common occurrence worldwide. We examined fish assemblage composition in three mangrove creek systems in Tanzania (East Africa), including two creeks where the upper parts were partly clear-cut of mangrove forest due to the construction of solar salt farms, and one creek with undisturbed mangrove forest. Fish were caught monthly for one year using a seine net (each haul covering 170 m²) within three locations in each creek, i.e. at the upper, intermediate and lower reaches. Density, biomass and species number of fish were lower in the upper deforested sites compared to the mangrove-fringed sites at the intermediate and lower parts in the two creeks affected by deforestation, whereas there were no differences among the three sites in the undisturbed mangrove creek system. In addition, multivariate analyses showed that the structure of fish assemblages varied between forested and clear-cut sites within the two disturbed creeks, but not within the undisturbed creek. Across the season, we found no significant differences except for a tendency of a minor increase in fish densities during the rainy season. At least 75% of the fishes were juveniles and of commercial interest for coastal fisheries and/or aquaculture. Mugil cephalus, Gerres oyena and Chanos chanos were the most abundant species in the forested sites. The dominant species in the clear-cut areas were M. cephalus and Elops machnata, which were both found in relatively low abundances compared to the undisturbed areas. The conversion of mangrove forests into solar salt farms not only altered fish assemblage composition, but also water and sediment conditions. In comparison with undisturbed areas, the clear-cut sites showed higher salinity, water temperature as well as organic matter and chlorophyll a in the sediments. Our results suggest that mangrove habitat loss and changes in environmental conditions caused by salt farm developments will decrease fish densities, biomass and species numbers as well as alter the overall fish assemblage composition in the salt farm area but not downstream in the creek.     

Possible effects of human impacts on epibenthic communities and coral rubble features in the marine Park of Bunaken (Indonesia)

Indo-Pacific coral reefs are considered among the most complex and biodiversified ecosystems in the world. Their existence is threatened by both natural and anthropogenic factors. Therefore, the assessment of anthropogenic disturbances is necessary to protect and manage these marine natural resources. In Bunaken Marine Park (North Sulawesi, Indonesia) epibenthic assemblages and coral rubble features at four impacted sites (each of them located close to villages and frequently exploited as recreational diving spots), and four well preserved sites (far from villages and scarcely frequented by divers), were investigated at 6, 12 and 18 m depth, in order to identify possible reef modifications. The assemblages were sampled by way of photographs. Coral rubble cover was estimated both by way of photographs and along belt transects, while grain size and the living fraction of the coral rubble were assessed by direct samples. The data showed significant differences between the study sites and between depths with regard to human activity. The hard coral cover and the assemblage heterogeneity are higher in control sites than in the impacted site where, especially in shallow water, the mechanical damage can strongly affect the assemblage structure.     

基于视觉特性的影像增强算法研究

遥感影像对比度调整是影像预处理中的关键部分。分析人的视觉特性发现：影像中不同区域特征变化被感知度有所差异。相对于高频区域及对角线方向,人眼更容易感觉到平缓部分的特征变化。以往的对比度增强算法并没有考虑这一视觉特性,提出了一种基于视觉特性的影像增强算法。实验表明,该算法在较好的保持影像细节特征的同时,改善了影像的对比度,得到了较好的视觉效果。     

基于高分辨率遥感影像的城市小区交通可达性评价——以厦门市为例

居住小区是与人们生活密切相关的单元,居住小区交通可达性是衡量小区环境好坏的一项重要指标。高分辨率遥感影像的空间分辨率可达到0.6m甚至更高,使得从居住小区的尺度研究交通可达性成为可能。本文从区域交通环境、路网可达性和设施可达性三个影响因子出发,根据高分辨率遥感影像的特点构建了居住小区交通可达性评价的指标体系,并对厦门市的实际情况进行实证分析,最后对选取的50个居住小区的交通可达性做出了综合评判。结果表明,利用高分辨率影像进行城市交通可达性评价是一种简便可行的方法。     

青海省长宁遗址沉积物元素对晚全新世人类活动和气候变化的响应

通过对青海省长宁遗址晚全新世沉积剖面OC、P、Ba、Mn、S、K2O、Pb、As、Al2O3、Fe2O3和Cu的化学成分分析及磁化率分析,研究了该时期沉积物元素含量对人类活动和气候变化的响应。结果表明,齐家文化时期(4300～3900aBP)至汉代(202BC—220AD)之间的气候恶化使沉积物中上述元素含量显著下降,齐家文化时期和汉代的人类活动也对沉积物元素含量产生了影响,不同方式的人类活动对沉积物元素含量的影响存在差异。     

鸭绿江河口地区沉积物的粒度变化及影响因素

通过对比鸭绿江河口不同地区柱状样的粒度参数及敏感组分变化规律,分析了河口不同地区沉积动力环境和沉积特征的差异;结合代表性柱状样的210Pb测年,分析了柱状样在不同时期自然和人类活动影响下的沉积特征变化。结果表明,西水道主要受潮流作用而含有泥沙互层,粒度参数变化小;西岸潮滩受潮流和波浪作用含有贝壳碎屑,并在顶部出现粗化层。近几十年来,鸭绿江河口地区沉积特征的变化主要由于人类活动对水沙入海通量的影响:1941年以前柱状样的波动沉积特征反映了河流山溪性特征;1941—1970(1980)年随水沙入海通量减少而呈现砂含量降低、粉砂增加的特征;1970(1980)—1990年由于水沙入海通量变化较小,而呈现沉积物组成和敏感组分保持稳定的特征;但1990年后随水沙入海通量的进一步降低,邻近河口区域的沉积物出现明显的粗化。     

地质学在关注人类活动的环境效应--兼谈黄河三角洲剖面炭屑分析与人类活动

人类活动的环境效应，很多大的国际研究计划都给予充分重视。炭屑分析是研究历史上人类活动的方法之一。黄河三角洲剖面炭屑分析，从自然变化背景中分离出了因人口增长和火灾造成的5个炭屑高峰值。这一结果说明，精细的高分辨率的研究工作，是探讨历吏上人类活动环境影响因子的前提。