Evaluating the sensitivity of wetlands to climate change with remote sensing techniques

Wetlands are valuable ecosystems that provide many valuable services, yet many of these important ecosystems are at risk because of current trends in climate change. The Prairie Pothole Region (PPR) in the upper‐midwest of the United States and south‐central Canada, characterized by glacially sculpted landscapes and abundant wetlands, is one such vulnerable region. According to regional/global climate model predictions, drought occurrence will increase in the PPR region through the 21st century and thus will probably cause the amount of water in wetlands to decline. Water surface area (WSA) of Kidder County, ND, from 1984–2011 was measured by classifying TM/ETM+(Landsat Thematic Mapper / Enhanced Thematic Mapper Plus) images through the modified normalized difference water index. We then developed a linear model based on the WSA of these wetlands and historical climate data and used this to determine the wetland sensitivity to climate change and predict future wetlands WSA in the PPR. Our model based on Palmer drought severity index (PDSI) of the current year (PDSI_{t ? 0}) and of the previous two years (PDSI_{t ? 2}) can explain 79% of the annual wetland WSA variance, suggesting a high sensitivity of wetlands to drought/climate change. We also predicted the PPR wetlands WSA in the 21st century under A1B scenario (a mid‐carbon emission scenario) using simulated PDSI based on Intergovernmental Panel on Climate Change AR4 22‐model ensemble climate. According to our prediction, the WSA of the PPR wetlands will decrease to less than half of the baseline WSA (defined as the mean wetlands WSA of the 2000s) by the mid of the 21st century, and to less than one‐third by the 2080s, and will then slightly increase in the 2090s. This considerable future wetland loss caused only by climate change provides important implication to future wetland management and climate adaptation policy. Copyright © 2012 John Wiley & Sons, Ltd.     

北京地区冻土时空分布特征

基于1981—2021年北京地区6个气象站的逐日最大冻土深度、平均气温、平均地表温度及5、10、15、20、40、80 cm地温等资料,分析了近40年北京地区最大冻土深度的时空分布特征及其与气温和地温的关系。结果表明：北京地区最大冻土深度总体呈变浅趋势,气候倾向率为-2.3 cm/10 a,各站点最大冻土深度变浅趋势从西到东呈逐渐减弱趋势。北京地区最大冻土深度与40、80 cm地温相关性最好,与地表温度相关性较差。选取2021至2022年北京地区冻土对比试验数据,评估测温式冻土自动观测仪观测精度,发现仪器安装至少一个冻融周期后与冻土人工观测吻合度更好,测温式冻土自动观测仪的观测精度与仪器安装位置的地下岩层、土质分布密切相关,需要在仪器稳定运行后根据当地实际优化算法和冻融阈值。     

西格陵兰Disko湾表层沉积硅藻组合研究

本文分析了西格陵兰Disko湾的表层沉积物硅藻,发现并统计了分属于39个属的78个硅藻种及其变种。应用对应分析方法,对Disko湾表层沉积硅藻组合进行了分类:组合Ⅰ为Fragilariopsis cylindrus-Fragilariopsis oceanica组合,主要分布在西格陵兰Disko湾南部的近岸和外海处;组合Ⅱ为Detonula confervaceae休眠孢子-Thalassiosira nordenskioeldii组合,都分布在Dis-ko湾北部海域。其中,根据海流等环境要素的不同,组合Ⅰ又可进一步划分为两个亚区:组合Ⅰa为F.cylindrus-F.oceanica-Pauliella taeniata组合,主要分布于沿岸海区;组合Ⅰb为F.cy-lindrus-F.oceanica-Thalassiosira antarcticavar.borealis休眠孢子-Thalassiosiracf.antarcticavar.borealis组合,分布于外海区域。     

基于深度学习的钨钼找矿靶区预测方法研究

随着矿产勘查工作由浅部矿向深部隐伏矿、由易识别矿向难识别矿发展,找矿难度日益增大,地质专家越来越重视新理论、新方法、新技术的应用。深度学习作为人工智能的前沿领域/技术,对于实现矿产资源预测“智能化预测评价”具有得天独厚的优势。本文以陕西省镇安县西部钨钼矿集区单元素化探异常原始数据为基础,提出了基于深度学习的钨钼矿产评价方法。该方法以归一化地球化学数据作为模型训练数据,通过深度学习中深度自编码网络方法实现异常值提取进而识别重点成矿有利地段,实现矿产资源找矿远景区定性预测。研究结果表明,在对957条单元素化探异常原始数据分类且做好模型标签后,整个过程在计算机的“黑盒子”中自动完成学习和预测,相较于传统预测研究方法,本文方法具有自动化程度高和客观性强的特征。此外,本文利用已知矿点构建训练数据集,采用随机森林方法对预测区进行矿产资源找矿靶区预测圈定,为进一步缩小找矿靶区范围提供科学依据。     

城市热岛效应监测方法研究进展

城市热岛效应是一种由于城市建筑及人们活动导致的热量在城区空间范围内聚集的现象,是城市气候最明显的特征之一.由于城市热岛影响因素以及相互关系的复杂性,为了精确细致地描述其时空分布,人们采用了多种方法来研究城市热岛现象,主要归纳为：气象站法、定点观测法、运动样带法、遥感测定法以及模拟预测等.最后,认为各种测定方法都存在一定的缺陷,建议多种测定方法综合运用.     

波浪荷载作用下海底隧道-孔隙海床的动力分析

孔隙海床在波浪荷载作用下其有效应力减小、孔隙水压力增加,这将影响孔隙海床中隧道的稳定性,因此,研究在波浪荷载作用下孔隙海床与隧道的动力响应具有重要的工程意义。本文基于Biot的动力固结理论和弹性动力学理论建立波浪荷载作用下孔隙海床与海底隧道的动力分析模型,并同时考虑海底隧道与海床之间的接触效应、边界效应等对海底隧道内力的影响。最后通过变换海床的变形模量、渗透系数和海底隧道的半径、埋深等,观察其对海床土孔隙水压力和海底隧道内力的影响,为海底隧道的设计提供依据。     

Landscape pattern evolution processes of alpine wetlands and their driving factors in the Zoige Plateau of China

Zoige Plateau wetlands are located in the northeastern corner of the Qinghai-Tibet Plateau.The landscape pattern evolution processes in the Zoige Plateau and their driving factors were identified by analyzing the dynamic changes in landscape modification and conversion and their dynamic rates of alpine wetlands over the past four decades.The results showed that the landscape conversion between wetlands and non-wetlands mainly occurred during the period from 1966 to 1986.The marsh wetland area converted from lake and river wetlands was larger because of swamping compared to other wetland landscapes.Meanwhile,the larger area of marsh wetlands was also converted to lake wetlands more than other types of wetlands.The modification processes mainly occurred among natural wetland landscapes in the first three periods.Obvious conversions were observed between wetland and nonwetland landscapes(i.e.,forestland,grassland,and other landscapes) in the Zoige Plateau.These natural wetland landscapes such as river,lake and marsh wetlands showed a net loss over the past four decades,whereas artificial wetland landscapes(i.e.,paddy field and reservoir and pond wetlands) showed a net decrease.The annual dynamic rate of the whole wetland landscape was 0.72%,in which the annual dynamic rate of river wetlands was the highest,followed by lake wetlands,while marsh wetlands had the lowest dynamic rate.The integrated landscape dynamic rate showed a decreasing trend in the first three periods.The changes in wetland landscape patterns were comprehensively controlled by natural factors and human activities,especially human activities play an important role in changing wetland landscape patterns.     

湖北辽瓦店遗址地层记录的环境变迁与人类活动的关系研究

用XRF和ICP-AES方法分别测试了湖北辽瓦店遗址地层样品的氧化物含量和地球化学元素含量,恢复了遗址地层中夏代文化层、东周文化层和明清文化层记录的环境变化和人类活动特征。结果表明:1)夏代文化层时期,气候温暖湿润,生态环境良好,人类活动与自然环境和谐度高,有原始的手工业活动记录。2)东周时期气候开始进入干旱期,干旱程度在上东周文化层中部逐渐加深(LOI=6.98%),到了上东周文化层顶部气候进入暖湿期。该层Cu含量的异常高值(0.31mg/g)和出土的青铜器表明本文化层反映了青铜社会的繁荣期,而P含量的高值(22.73mg/g)和动物骨屑则反映了该期人们驯养、捕猎动物的普遍性。3)明清时期的气候趋于干凉,明代文化层中部有短暂暖湿期,后又进入冷干期。清代文化层中下部有暖湿特征,之后重新进入干冷期。该层Ca(均值101.5mg/g),Mg(均值60.27mg/g),Zn和Pb的高含量表明遗址曾有过制陶(瓷)业的历史。另外,Mg和Ca含量的高值与耕作区、墙壁灰浆、生活垃圾堆积等人类活动相关。Ca和Mg含量在近现代层逐步升高揭示了人类活动逐渐增强的事实。地层的平均粒径自上东周文化层(<142cm)开始出现振荡,暗示汉江洪水和季节性山洪发生的频率不断增加,表明恶劣环境条件虽然促进了人类生产力水平的提高,但原始生态系统却遭到破坏,人类活动对自然环境的正反馈效应日益凸显。     

Threat from above! Assessing the risk from the Tonghua high-locality landslide in Sichuan,China

Landslides - In tectonically active steep mountain belts, such as those in west Sichuan in China, frequent landslide disasters can occur during the rainy season. High-locality landslides often...     

中国对虾体内20-羟基蜕皮酮含量与生长和性腺发育的关系

应用放射免疫分析法对完成变态后的中国对虾(Penaeus orientalis)体内20-羟基蜕皮酮(20-HE)含量进行了周年测定。5～6月,全虾抽提液中20-HE的质量分数以体长为0.8cm的仔虾为最高(47.96±3.94)×10~(-9)(m/m)。血淋巴中20-HE的质量浓度在6～8月(平均为22.66ng/mL)和11月(25.93±3.44ng/mL)较高,翌年3月最低,为8.29±1.40ng/mL。呈现出20-HE含量与蜕皮生长和促进卵母细胞早期发育及精子发生有关。