基于改进层次分析法的城中村火灾风险评估及防控对策研究

为更好的预防与控制城中村火灾风险,本文将事故树、层次分析法、模糊综合评价相结合,通过FTA建立AHP模型,从防火能力、灭火能力、安全疏散能力、安全管理水平4个维度出发构建了城中村火灾风险评估指标体系,并计算了各评价指标权重,通过实例研究证明,该方法能够较好的分析评价城中村火灾风险安全等级,最后提出相对应的对策与建议,有利于城中村火灾风险的预防与控制,为提高城中村火灾消防安全管理水平奠定了理论基础。     

浅谈景星镇新农村生态建设中绿化树种选择

以"村容整洁"为核心的村庄绿化是新农村生态建设重要内容。绿化树种选择应优先选择乡土树种,兼顾经济、环境效益与景观的统一。     

基于梯度提升回归树算法的地面臭氧浓度估算

将机器学习中的梯度提升回归树（GBRT）算法应用到中国地区地面O₃浓度制图中,利用地面O₃浓度观测数据,结合WRF气象数据、MODIS植被归一化指数以及高程人口数据建立训练预测数据集.通过反向变量选择法选取模型最佳特征变量对其进行训练,十折交叉验证结果：决定系数R²=0.89、均方根误差RMSE=4.75μg/m³.同时对全国O₃人口暴露水平进行评估.结果表明：在暴露强度上,我国人口加权O₃浓度值排在前5的省依次是山东、河南、江苏、河北、上海,均值浓度为94.48μg/m³.在暴露持续时间上,非达标天数最多的5个省依次是河南、山东、河北、宁夏、北京,一年内有42%的天数处于非达标的状态.     

Effects of recreational use on forested sites

Impact of recreational activities on soil and vegetation was evaluated in eight forested camping and picnic areas in southern Rhode Island. Forest vegetation consists of mixed-oak and white pine stands. Soils are of granitic glacial till or outwash origin and textures range from loamy sand to find sandy loam. Recreational use resulted in significant compaction of soils as indexed by soil penetration resistance and bulk density. Evidence indicates that compaction influences bulk densities to a depth of about 12.7 cm. Rates of water infiltration are less on recreation areas. Soil water accretion and depletion during the growing season are less rapid on recreation sites than on control sites. Differences are attributed to reduced infiltration, percolation, and rooting activity. Much of the ground surface on recreation areas is devoid of vegetation. The surface consists primarily of bare mineral soil, rock, or litter. The plants most commonly present are grasses. Native ground cover vegetation including tree seedlings, ericaceous shrubs and herbs has been eliminated or greatly reduced by trampling. Damage to tree trunks is common in recreation areas. White pine radial growth and scarlet oak height growth were significantly less on recreation sites. Scarlet oak appears intolerant to heavy recreation use.     

叶面喷施磁处理复合肥对新红星（Starkrimson）苹果树营养元素的影响

叶面喷施磁处理复合肥对新红星（Ｓｔａｒｋｒｉｍｓｏｎ）苹果树营养元素的影响程文林，杨佩芳，刘和，陈晓春，高美英（山西农业大学大谷０３０８０１）关键词磁处理复合肥，根外追肥，新红星苹果树，营养元素ＥＦＦＥＣＴＯＦＭＡＧＮＥＴＩＺＥＤＣＯＭＰＯＵＮＤＦＥ...     

决策树法在投标决策中的应用

为了提高施工企业的中标概率,获取更多的利润,减少决策失误.本文对决策树法的基本理论、适用条件、绘制方法及选取最佳方案进行了探索.     

我国桐油发展战略与对策

桐油是我国的特产资源，其价值之高，用途之广，早已引起许多国家的重视；其化学结构之特殊，化学性质之活泼，引起许多化学工作者的兴趣，而致力于桐油化学科学的研究。我国种植油桐历史修久，远在公元前六世纪有文记载。新中国成立后，党 和政府非常重视，周总理曾亲自主持全国油桐工作会议，油桐得到了空前发展。     

Predicting a ‘tree change’ in Australia's tropical savannas: Combining different types of models to understand complex ecosystem behaviour

In this study, key ecological modelling limitations of a process-based simulation model and a Bayesian network were reduced by combining the two approaches. We demonstrate the combined modelling approach with a case study investigating increases in woody vegetation density in northern Australia's tropical savannas. We found that by utilising the strengths of a simulation model and a Bayesian network we could both forecast future change in woody vegetation density and diagnose the reasons for current vegetation states. The local conditions of climate, soil characteristics and the starting population of trees were found to be more important in explaining the likelihood of change in woody vegetation density compared to management practices such as grazing pressure and fire regimes. We conclude that combining the strengths of a process and BN model allowed us to produce a simple model that utilised the ability of the process model to simulate ecosystem processes in detail and over long time periods, and the ability of the BN to capture uncertainty in ecosystem response and to conduct scenario, sensitivity and diagnostic analysis. The overall result was a model that has the potential to provide land managers with a better understanding of the behaviour of a complex ecosystem than simply utilising either modelling approach in isolation.     

Evaluation of Heritage Trees for Conservation and Management in Guangzhou City (China)

The recent fast pace of urbanization in China and other developing countries has exerted pressure on urban trees, which constitute a key urban environmental asset. The most outstanding trees should be treated as natural-cum-cultural heritage. Guangzhou Citys growth has threatened its rich urban-tree endowment, a diversified assemblage of 200,000 trees represented by 254 species and located in three major habitats: roadside, park, and institutional grounds. Mainly based on age and performance, 348 trees were officially designated as heritage specimens. They were evaluated in the field for tree dimensions, habitat, performance, and landscape contribution, to establish enhanced conservation and management strategies. With only 25 species, heritage trees were dominated by five cultivated natives and encompass some of the citys rare species; some common urban-forest species were not represented. Older districts and roadside habitats, despite their compact town plan and limited growing space, had the largest tree dimensions and largest share of heritage trees. Many heritage trees were large with long life expectancy and the potential for biomass expansion, and had pivotal cityscape impacts where they occur. Old neighborhoods, traditional haven for the arborescent treasure, are being changed by construction activities and periodic typhoon and windstorm damages. Increasing development density could degrade the heritage trees and their growing space, and reduce tree quality and life span. Upgrading the statutory-administrative systems and arboricultural care can enhance long-term survival of the precious natural-cum-cultural heritage. The experience of Guangzhou in identifying and preserving its high-quality urban trees can provide management strategies for other cities.     

Optimal hardwood tree planting and forest reclamation policy on reclaimed surface mine lands in the Appalachian coal region

We study the optimal hardwood tree planting decision on reclaimed surface coal mines in the Appalachian region using a mine operator-focused, expected cost model that recognizes costs of preparing the site for tree planting, unit costs of planting seedlings, and opportunity costs of reforestation treatments and the performance bond. We also consider the possibility of failed initial attempts by incorporating the probability of reforestation success, based on empirical seedling ,survival rates and regulated tree survival standards, as well as fixed and unit costs of returning for additional planting. Optimal planting levels from 319 to 780 trees per acre and expected costs from $1049 to $2338 were found using simulations over a range of unit planting costs, fixed costs of replanting, tree survival standards, and interest rates. Further simulations compared optimal planting across un-weathered gray sandstone and weathered brown sandstone substrate materials, finding gray sandstone to be associated with lower expected costs. We conclude that optimal planting density and expected reforestation cost are sensitive to economic parameters, regulations, and planting substrate materials; and those policies influencing these factors may have substantial impact on reforestation outcomes and the choice of post-mining land use by mine operators. Our study provides a framework for understanding forest reclamation decisions that incorporates incentives faced by the mine operators who develop and implement the plans for mine reclamation, including forestry.