大兴安岭北部多年冻土区落叶松和樟子松生长的气候响应差异研究   总被引：3，自引：2，他引：1  

张轩文  杨丽  刘晓宏  张秋良  王文志  曾小敏  吴国菊 《冰川冻土》2017,39(1):165-174

以大兴安岭北部根河、呼中和汗马冻土区落叶松和樟子松为样本,建立了五个树轮宽度年表,并计算获取了五个样点的树轮截面积指数（BAI）序列。树轮BAI-气候响应关系分析表明,气温为这一地区落叶松和樟子松生长的主要限制因子;但落叶松和樟子松对气候变化的响应存在差异。落叶松BAI与3月平均气温,樟子松BAI与前一年12月至当年4月平均气温均呈显著负相关。考虑到水热综合影响,落叶松BAI控制因子由1957-1990年与其呈显著正相关的1月份SPEI转变为1991-2013年与其呈显著正相关的1-4月SPEI和与其呈显著负相关的3月份平均气温;樟子松BAI控制因子则由1957-1990年与其呈显著负相关的2月和8月份平均气温转变为1991-2013年与其呈显著正相关的7月份降水量和6-7月SPEI。结果表明,在全球变暖背景下,水热环境改变使得冻土区树木生长限制因子发生变化。  相似文献   

树轮记录的西北季风边缘区干旱变化     

张芬  陈巧湄  苏佳佳  邓洋  高琳琳  勾晓华 《冰川冻土》2017,39(2):245-251

祁连山东部位于亚洲季风西北边缘区,对气候变化十分敏感。由于该区位于半干旱区,降水的变化直接影响人类社会经济的发展,所以研究该区干旱变化情况及其机制非常重要。 利用采自祁连山东部西北季风边缘、地处半干旱区的吐鲁沟地区的油松树轮样芯,建立了树轮宽度年表,时间跨度为1866-2003AD。树轮宽度年表与气象因子相关分析结果显示树木生长主要响应生长季内的降水和干旱变化。该年表与附近区域利用树轮宽度重建的帕尔默干旱指数（PDSI）进行对比,结果显示严重的干旱时间发生在1920s-1930s、1966年、1974年、1982年和1990s和21世纪初。多窗谱分析研究表明,该区年表序列存在显著的2~4 a周期（P<0.05）,该周期与ENSO变率吻合,与在贺兰山、祁连山其他地区、兴隆山及贵清山研究结果一致,表明这些区域可能受共同气候因子的影响。  相似文献   

Forecasting bivalve landings with multiple regression and data mining techniques: The case of the Portuguese Artisanal Dredge Fleet     

《Marine Policy》2017

This paper develops a decision support tool that can help fishery authorities to forecast bivalve landings for the dredge fleet accounting for several contextual conditions. These include weather conditions, phytotoxins episodes, stock-biomass indicators per species and tourism levels. Vessel characteristics and fishing effort are also taken into account for the estimation of landings. The relationship between these factors and monthly quantities landed per vessel is explored using multiple linear regression models and data mining techniques (random forests, support vector machines and neural networks). The models are specified for different regions in the Portugal mainland (Northwest, Southwest and South) using six years of data 2010–2015). Results showed that the impact of the contextual factors varies between regions and also depends on the vessels target species. The data mining techniques, namely the random forests, proved to be a robust decision support tool in this context, outperforming the predictive performance of the most popular technique used in this context, i.e. linear regression.  相似文献   

New Relationship for Estimation of Wave Overtopping on Vertical Walls     

ESKANDARI Hojjatollah  KAMALIAN Ulrich Reza 《海洋工程》2017,31(1):48-54

Soft computing tools in the form of combination of multiple nonlinear regression and M5'' model tree were used for estimation of overtopping rate at the vertical coastal structures. For reliable and precise estimation of overtopping rate, the experimental data available in the database CLASH were used. The dimensionless overtopping rate was estimated in terms of conventional dimensionless parameters including the relative crest freeboard R_c/H_s, seabed slope tanθ, deep water wave steepness S_om, surf similarity ξ_om and local relative water depth h_t/H_s. The accuracy of the new model was compared with other existing models and also evaluated with some field measurements. The results indicated that the model presented in this paper is more accurate than other existing models. With statistical parameters, it is shown that the accuracy of predictions in the new model is better than that of other models.  相似文献   

塔里木灌区香梨树腐烂病害发生成因     

李茂春 《沙漠与绿洲气象(新疆气象)》2012,6(4):48-51

本文根据2001～2011年对塔里木灌区香梨树腐烂病害的观测调查情况,结合当地农业气候条件进行对比分析,找出香梨树腐烂病害加重形成的因素。通过连续11年的跟踪观测、调查资料结合对灌区香梨树腐烂病害的发生规律进行研究分析,香梨树腐烂病害的发生、发展与气候、土壤、虫害、田间管理等有密切关系。本文针对各种不同情况香梨树腐烂病害的发生、发展,提出相应的预防对策措施,为今后灌区香梨树腐烂病害的防治提供有利依据。  相似文献   

吉林和龙第二林场铁矿床地质特征及找矿方向     

张宏  贾楠  赵际新  孙雪峰  冯修云 《吉林地质》2010,29(4):62-65,69

该铁矿床产于中太古界夹皮沟群三道沟组地层中,与桦甸市老牛沟铁矿、桦甸市头道岔铁矿及和龙市官地铁矿相同,均为沉积变质型铁矿床。空间上矿体呈条带,受地层控制,该矿床的找矿成果对指导区域铁矿地质找矿具有实际应用意义。  相似文献   

矿区煤及矸石压占灾害决策树分类提取方法     

李方方  马超  徐小波  马红花 《地质灾害与环境保护》2010,21(4):73-76

矿业活动为现代工业提供物质基础的同时,极大扰动矿区原有生态结构。煤与矸石压占是矿区多种地质灾害的一种,煤与矸石压占直接造成矿区珍贵的土地资源的浪费,同时,煤与矸石自燃、淋溶、扬尘以及天然放射性对矿区环境有严重影响。近年来,遥感技术以其大范围、实时性等技术优势,在探索矿业活动与生态保护共同途径方面做了大量有益的尝试,尤其在地质灾害监测预警方面体现了广阔应用前景。本文通过对矿区遥感影像的一系列处理(如图像校正,图像增强,图像分类),探索性地采用基于人工智能的决策树分类方法,有效地排除掉同谱异物的现象的影响,高精度地提取出矿区煤与矸石堆放场,为统计煤与矸石压占,预知煤与矸石自燃,判断煤与矸石淋溶、扬尘以及天然放射性对周围环境的影响,以及为今后煤与矸石场的选址规划,提供第一手定量化的地理属性资料。  相似文献   

A Sustainability Initiative to Quantify Carbon Sequestration by Campus Trees     

《The Journal of geography》2012,111(5):173-183

Abstract

Over 3,900 trees on a university campus were inventoried by an instructor-led team of geography undergraduates in order to quantify the carbon sequestration associated with biomass growth. The setting of the project is described, together with its logistics, methodology, outcomes, and benefits. This hands-on project provided a team of students with several learning opportunities including an introduction to carbon sequestration, basic arboriculture, field-based measurements, mapping, geographic information systems, and biogeography concepts. A GIS geodatabase was produced containing information on tree location, species, size, biomass, carbon content, and annual CO₂ sequestration, which was later customized for integration into campus facilities management.  相似文献   

混合式球面退化剖分模型的设计与编码     

李正国  包全福  张永生  靳彩娇 《测绘科学技术学报》2012,(4):289-293

为了解决球面退化四叉树格网(DQG)模型孔径较大、格网单元面积分布不均匀以及三角格网单元应用不完全四叉树剖分的问题,通过控制单元面积的思路设计了一种格网单元孔径更小、分布更均匀的四边形(中低纬地区)与三角形(高纬地区)的混合格网模型——混合式球面退化格网模型(MSDG);并对所有格网单元利用四叉树进行编码。通过对格网单元的几何属性统计分析发现,该格网模型的几何属性与DQG模型相比,其单元面积变化更小、分布更加均匀稳定。  相似文献   

ID3决策树推理模型及其在道路网选取中的应用     

郭敏  钱海忠  黄智深  刘海龙  鞠金春 《测绘科学技术学报》2012,(4):308-312

介绍了自动制图综合中知识推理的研究现状及存在的问题,指出了借鉴人工智能优秀技术成果提升自动综合智能化水平是解决当前问题的重要途径之一。对ID3智能算法的基本原理进行了详细介绍,提出基于ID3决策树的知识推理模型。将该模型引入到道路网智能化选取当中。对该模型应用到道路网自动选取的合理性进行了论述,并进行了实验验证。在对实验结果进行详细分析的基础上,探讨了该算法应用于道路网选取的优势和不足,指出了进一步研究的方向。  相似文献