阿尔泰山历史时期气候水文变化特征分析

通过分析总结在中国阿尔泰山区域已取得的树轮气候学和树轮水文学研究成果,选取了5条气温重建序列,3条降水重建序列和2条径流量重建序列,对各序列在全频域、低频域和高频域的相关系数、序列的阶段变化、极值年份、周期等特征展开了讨论和对比,并对阿尔泰山气候的年代际变化进行了分析。结果表明：（1）目前在阿尔泰山开展的气温重建中,重建时段均在树木生长季内,5条气温重建序列显示在1690年代-1700年代、1730年代、1780年代-1790年代为偏冷时期,1710年代-1720年代、1800年代-1830年代、1940年代-1960年代及1990年代以来为偏暖时期。有3条序列指示1830年为暖年,1698年、1784年、1911年、1985-1986年为冷年。（2）3条降水重建序列显示,1830年代-1860年代经历了一段降水量相对平稳的时期,1870年代-1900年代为持续时间最长的干旱时期,1900年为干旱年。（3）2条径流量重建序列显示,1730年代和1810年代-1820年代为丰水期,1750年代和1870年代-1890年代为枯水期,降水量对哈巴河径流量有较大影响。（4）年代际气候变化分析显示,阿尔泰山在1830年代-1990年代以暖干为主,1990年代以后进入了暖湿时期。     

Developing an Event Tree for probabilistic hazard and risk assessment at Vesuvius

Probabilistic characterizations of possible future eruptive scenarios at Vesuvius volcano are elaborated and organized within a risk-based framework. In the EXPLORIS project, a wide variety of topics relating to this basic problem have been pursued: updates of historical data, reinterpretation of previous geological field data and the collection of new fieldwork results, the development of novel numerical modelling codes and of risk assessment techniques have all been completed. To achieve coherence, many diverse strands of evidence had to be unified within a formalised structure, and linked together by expert knowledge. For this purpose, a Vesuvius ‘Event Tree’ (ET) was created to summarise in a numerical-graphical form, at different levels of detail, all the relative likelihoods relating to the genesis and style of eruption, development and nature of volcanic hazards, and the probabilities of occurrence of different volcanic risks in the next eruption crisis. The Event Tree formulation provides a logical pathway connecting generic probabilistic hazard assessment to quantitative risk evaluation. In order to achieve a complete parameterization for this all-inclusive approach, exhaustive hazard and risk models were needed, quantified with comprehensive uncertainty distributions for all factors involved, rather than simple ‘best-estimate’ or nominal values. Thus, a structured expert elicitation procedure was implemented to complement more traditional data analysis and interpretative approaches. The structure of the Vesuvius Event Tree is presented, and some of the data analysis findings and elicitation outcomes that have provided initial indicative probability distributions to be associated with each of its branches are summarized. The Event Tree extends from initiating volcanic eruption events and hazards right through to human impact and infrastructure consequences, with the complete tree and its parameterisation forming a quantitative synoptic framework for comprehensive hazard evaluation and mapping of risk impacts. The organization of the Event Tree allows easy updating, as and when new information becomes available.     

Rings of radio continuum,Co, Hα and magnetic fields in galaxies

Abstract

Observations are reviewed that indicate the existence of rotating rings in a number of galaxies that possess poloidal magnetic fields in their nuclear regions, including our own Galaxy. Jets from these, possibly aligned with the poloidal field, may also be present. The role of these rings in dynamo processes is briefly discussed.     

Annual temperatures during the last 2485 years in the mid-eastern Tibetan Plateau inferred from tree rings

By combining living trees and archaeological wood, the annual mean temperatures were reconstructed based on ring-width indices of the mid-eastern Tibetan Plateau for the past 2485 years. The climate variations revealed by the reconstruction indicate that there were four periods to have average temperatures similar to or even higher than that mean of 1970 to 2000 AD. A particularly notable rapid shift from cold to warm, we call it the “Eastern Jin Event”, occurred from 348 AD to 413 AD. Calculation results show that the temperature variations over the mid-eastern Tibetan Plateau are not only representative for large parts of north-central China, but also closely correspond to those of the entire Northern Hemisphere over long time scales. During the last 2485 years, the downfall of most major dynasties in China coincides with intervals of low temperature. Compared with the temperature records in other regions of China during the last 1000 years, this reconstruction from the Tibetan Plateau shows a significant warming trend after the 1950s. Supported by National Natural Science Foundation of China (Grant Nos. 40525004, 40599420, 40890051), National Basic Research Program of China (Grant Nos. 2007BAC30B00, 2004CB720200, 2006CB400503) and the Swedish International Development Cooperation Agency (SIDA, Grant to Hans W. Linderholm)     

Estimating tree abundance from remotely sensed imagery in semi-arid and arid environments: bringing small trees to the light

The analysis of remotely sensed images provides a powerful method for estimating tree abundance. However, a number of trees have sizes that are below the spatial resolution of remote sensing images, and as a result they cannot be observed and classified. We propose a method for estimating the number of such sub-resolution trees on forest stands. The method is based on a backwards extrapolation of the size-class distribution of trees as observed from the remotely sensed images. We apply our method to a tree database containing around 13,000 tree individuals to determine the number of sub-resolution trees. While the proposed method is formulated for estimating tree abundance from remotely sensed images, it is generally applicable to any database containing tree canopy surface area data with a minimum size cut-off.     

秦岭南坡佛坪1789年以来1~4月平均温度重建

采用秦岭南坡陕西佛坪龙草坪、光头山、三个包及三官庙建立的秦岭冷杉、油松和铁杉树轮宽度、密度年表, 分析树木生长对气候要素变化的响应关系, 重建了佛坪1789年以来1~4月平均温度变化, 并对其进行了变化特征分析。结果表明, 各样点的树木生长明显受生长季前期温度影响, 呈较为显著的正相关关系。利用多个样点的年表并引入主分量分析方法建立回归方程, 显著地提高了回归方程的稳定性和显著性, 进而提高了重建结果的可信度。功率谱分析结果表明, 佛坪1~4月平均温度变化具有显著的3~4年周期。而滑动t检验、滑动F检验和Lepage检验结果表明, 18世纪后期以来于1896年前后发生了10年时间尺度的方差突变, 表现为温度波动幅度的变化。     

Identifying barriers to effective management of widespread invasive alien trees: Prosopis species (mesquite) in South Africa as a case study

Biological invasions are a major driver of ecological and social change globally. The negative effects of these invasions have led to the initiation of programs to manage these invasions across the world. Management aims to reduce impacts and in some cases improve the benefits that some invasive species can provide. This study assesses the barriers that hinder the effective management of widespread tree invasions, drawing insights from a case study of invasions of Prosopis species (mesquite) in South Africa. We used questionnaire surveys and focussed workshops to identify barriers and adaption responses in four key stakeholder groups involved in different stages of management. More than 100 barriers were identified, most of them relating to social issues. Key barriers related to limited knowledge, insufficient funds, conflicts of interest, the ecology of the genus and the nature of the invaded land, as well as poor planning, co-ordination and co-operation, and a lack of prioritisation. There were marked differences in how stakeholders perceived the importance of some barriers. Most Farmers (>80%) placed high importance on a lack of planning, and poor management as important barriers, while few Managers (<20%) regarded these as important; this reflects different views about the context in which management projects operate. Workshops identified more barriers and, overall, provided greater insights into the dimensions of barriers. The questionnaires were, however, useful for providing quantitative data which helped to rank the importance of barriers amongst stakeholders. Although adaptation responses were identified, not all barriers are conducive to simple solutions. Among the most intractable barriers were the lack of adequate funds and factors relating to the ecology of Prosopis species. Problems such as adopting new clearing methods and strategic planning need to be overcome to improve the effectiveness of control with the available funds.     

基于机器学习的滑坡灾害易发性评价——以三峡库区为例

三峡库区滑坡灾害分布广、数量多、规模大、危害严重,因此开展滑坡灾害易发性评价对该地的地灾防治与处理具有重要参考意义。本文提取了地层岩性、地质构造、坡度、坡向、曲率、斜坡形态、植被指数、水系等17 个因子,选用逻辑回归模型、支持向量机模型、集成学习的梯度提升迭代决策树模型和深度学习中的长短期记忆神经网络与卷积神经网络耦合模型四个机器学习模型进行滑坡灾害易发性评价,选取最优评价模型,完成三峡库区的易发性分区评价,总结研究区易发性空间区划特性。对比四种模型的AUC（Area Under Curve）精度可以得出结论：GBDT模型（Gradient Boosting Decision Tree Model）的AUC精度相对较高,优于其他三个模型,更适合三峡库区的滑坡易发性研究。GBDT的易发性评价结果显示：研究区内极高易发性区域和高易发性区域主要集中于渝东、鄂西一带以及长江沿岸和支流沿岸。研究结果是对整个库区的易发性进行评价,可为后续库区的防灾减灾提供参考。     

Reconstruction of the Past Climate From Tree Rings Over Western Himalaya, India

RECONSTRUCTION OF THE PAST CLIMATE FROM TREE RINGS OVER WESTERN HIMALAYA, INDIA     

基于树轮生理模型的雪岭云杉径向生长的模拟研究

雪岭云杉(Picea schrenkiana)是天山山区重要的造林树种,为了解天山山区森林上限树木径向生长对气候环境的响应机制,运用树轮气候学方法,通过采自天山东部巴里坤山雪岭云杉林上限的树芯样本建立的树轮宽度标准化年表,采用VS-oscilloscope模型,模拟雪岭云杉的径向生长过程并揭示了过去55 a以来该过程与环境因子的关系。结果表明:(1)模拟得到的树轮宽度指数与实际树轮宽度指数相关系数为0.645(P<0.01)。两者变化趋势具有较好的一致性,表明模型取得了较好的模拟效果。(2)树木径向生长主要限制因子是4～5月和7～8月的土壤湿度,温度是决定树木生长季开始的主要影响因子,而温度决定的生长速率在宽窄轮的形成上并不明显。(3)模拟的树轮宽度指数与生长结束日期的相关系数是-0.413(P<0.01),说明生长季节的结束日期对树轮宽度的增长有一定的影响。(4)自1984年以来,随着区域气温的逐渐上升,树木生长季的长度有延长的趋势,而树木径向生长却发生衰退现象,1984年以来气温的升高可能是树木生长衰退的主要原因。因而研究从生理角度揭示天山东部森林上限树木径向生长过程中...