Environmental change and raw material selection strategies at Taoshan: a terminal Late Pleistocene to Holocene site in north‐eastern China     

《第四纪科学杂志》2017,32(5):553-563

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中小城市公共自行车出行模式与驱动机制研究     

王陆一  吴健生  李卫锋 《地球信息科学学报》2019,21(1):25-35

公共自行车在促进交通可持续发展、方便居民出行等方面意义重大。本文以广东省惠州市惠城区和惠阳区、韶关市区公共自行车为研究对象,利用时间序列数据分析、层次聚类、地理可视化等方法探究出行模式,利用随机森林算法分析出行行为的影响因素及其重要性程度。研究发现,惠州市惠城区和韶关市的公共自行车出行行为有规律、成规模,站点呈现生活居住、工作就业等类型;惠州市惠城区自行车使用目的多元,包括通勤、短途办事、公交接驳等,韶关市中,通勤是主要出行目的。惠州市惠阳区受到骑行道路限制,公共自行车使用率低。本研究可以为提高公共自行车系统运营效率、引导慢行交通政策制定、评估城市用地布局提供参考和建议,也能为其他区域公共自行车的研究提供借鉴作用。  相似文献   

Discrimination of species composition types of a grazed pasture landscape using Sentinel-1 and Sentinel-2 data     

《International Journal of Applied Earth Observation and Geoinformation》2020

Species composition is one of the important measurable indices of alpha diversity and hence aligns with the measurable Essential Biodiversity Variables meant to fulfil the Aichi Biodiversity Targets by 2020. Graziers also seek for pasture fields with varied species composition for their livestock, but visual determination of the species composition is not practicable for graziers with large fields. Consequently, this study demonstrated the capability of Sentinel-1 Synthetic Aperture Radar (S1) and Sentinel-2 Multispectral Instrument (S2) to discriminate pasture fields with single-species composition, two-species composition and multi-species composition for a pastoral landscape in Australia. The study used K-Nearest Neighbours (KNN), Random Forest (RF) and Support Vector Machine (SVM) classifiers to evaluate the strengths of S1-alone and S2-alone features and the combination of these S1 and S2 features to discriminate the composition types. For the S1 experiment, KNN which was the reference classifier achieved an overall accuracy of 0.85 while RF and SVM produced 0.74 and 0.89, respectively. The S2 experiment produced accuracies higher than the S1 in that the overall performance of the KNN classifier was 0.87 while RF and SVM were 0.93 and 0.89, respectively. The combination of the S1 and S2 features elicited the highest accuracy estimates of the classifiers in that the KNN classifier recorded 0.89 while RF and SVM produced 0.96 and 0.93, respectively. In conclusion, the inclusion of S1 features improve the classifiers created with S2 features only.  相似文献   

Discrimination of different sea ice types from CryoSat-2 satellite data using an Object-based Random Forest (ORF)     

Su Shu  Xiaoyi Shen  Zhanchi Liu  Qiuhua Tang  Haili Li 《Marine Geodesy》2020,43(3):213-233

Abstract

Sea ice type is one of the most sensitive variables in Arctic sea ice monitoring, and it is important for the retrieval of ice thickness. In this study, we analyzed various waveform features that characterize the echo waveform shape and Sigma0 (i.e., backscatter coefficient) of CryoSat-2 synthetic aperture radar altimeter data over different sea ice types. Arctic and Antarctic Research Institute operational ice charts were input as reference. An object-based random forest (ORF) classification method is proposed with overall classification accuracy of 90.1%. Accuracy of 92.7% was achieved for first-year ice (FYI), which is the domain ice type in the Arctic. Accuracy of 76.7% was achieved at the border of FYI and multiyear ice (MYI), which is better than current state-of-the-art methods. Accuracy of 83.8% was achieved for MYI. Results showed the overall accuracy of the ORF method was increased by ～8% in comparison with other methods, and the classification accuracy at the border of FYI and MYI was increased by ～10.5%. Nevertheless, ORF classification performance might be influenced by the selected waveform features, snow loading, and the ability to distinguish sea ice from leads.  相似文献   

Effects of forest cover change on catchment evapotranspiration variation in China     

Tingting Ning  Zhi Li  Qi Feng  Wen Chen  Zongxing Li 《水文研究》2020,34(10):2219-2228

Several large-scale revegetation programs in China have resulted in significant changes in forest cover (ΔF) during the past three decades. As forests have important effects on catchment hydrology, evaluating the effects of ΔF on hydrology is essential. Using data from 44 catchments across China, this study derived a rational analytical equation to link changes in actual evapotranspiration (ΔET) with those in F within the Budyko framework, and further quantified the effects of ΔF on ET variation during 1976–2015. The elasticity of ET to ΔF was found to be the greatest in the dry catchments in northwest China, followed by the humid catchments in south China, and was the smallest in the subhumid and semiarid catchments in north China. F averaged across all the catchments has increased, and has further led to the increase in ET. The F-ET relationship has become more prominent in the recent decade (2006–2015), with 68.0% of the catchments showing an average increase in F of 4.5% and a resultant average increase in ET of 8.2% compared with the baseline period (1976–1985). These results are helpful for quantitative assessment of hydrological responses to afforestation, especially in water-limited regions.  相似文献   

基于特征空间优化的随机森林算法在GF-2影像湿地分类中的研究   总被引：1，自引：0，他引：1  

詹国旗  杨国东  王凤艳  辛秀文  国策  赵强 《地球信息科学学报》2018,20(10):1520-1528

由于季节性的植被动态和水文波动,湿地遥感影像分类常常比较困难。本文采用优化特征空间的随机森林算法（Random Forest）对吉林省白城市通榆县东部地区预处理后的GF-2影像进行湿地分类研究,具体分为2步：① 对研究区遥感影像进行多尺度分割和对象特征的提取。针对一些学者获取最佳分割尺度时仍受主观因素影响较大的情况,本文通过改进全局最优分割方法来获得最佳分割尺度。② 在最优分割的基础上,基于特征重要性对随机森林分类算法的特征空间进行优化,以得到最佳的随机森林分类结果,并与相同条件下（同数据、同分割尺度、同训练样本,同特征空间）的K-NN、SVM、CART 3种算法以及未优化特征空间的RF算法的分类结果进行了比较。结果表明,基于优化特征空间的RF算法的分类结果总精度和Kappa系数分别为93.038%和0.9177,而K-NN、SVM和CART 3种分类算法的分类结果的总精度分别为83.357%、78.068%、77.136%,未优化特征空间的RF算法分类结果总精度为90.937%。相较于K-NN、SVM、CART 3种分类算法,RF算法在GF-2湿地影像数据中具有更好的分类性能,同时优化特征空间的RF算法精度有所提高,在湿地资源管理中可以发挥非常重要的作用。  相似文献   

Tree Planting:How Fast Can It Accelerate Post-fire Forest Restoration?——A Case Study in Northern Da Hinggan Mountains,China     

LI Xiuzhen  HE Hong S  WANG Xugao  XIE Fuju  HU Yuanman  LI Yuehui 《中国地理科学(英文版)》2010,20(6):481-490

In 1987,a catastrophic fire burned over 1330000 ha in the densely forested area of the Da Hinggan Mountains in the northeastern China.After the fire,intensive management including burned trunk harvesting and coniferous tree planting had been conducted to accelerate forest restoration.To study the long term effect of these activities on forest recovery,we used a simulation modeling approach to study long-term(300 years) forest dynamics under current planting and natural regeneration scenarios.Results indicat...  相似文献   

Forest ecosystem services and their values in Beijing   总被引：5，自引：3，他引：2  

Gaodi Xie  Wenhua Li  Yu Xiao  Biao Zhang  Chunxia Lu  Kai An  Jixing Wang  Kang Xu  Jinzeng Wang 《中国地理科学(英文版)》2010,20(1):51-58

As the most important ecosystem in Beijing, the forest supports a lot of ecosystem services to local and around communities, which plays a key role in the maintenance of urban ecological security.However, the valuation on the forest ecosystem services based on regional scale could not provide precise and reasonable values for forestry sector management.In this study, we estimated the magnitudes and economic values of the forest ecosystem services in Beijing at sublot level.The economic value of forest ecosystem services in Beijing was estimated to be 19 339.71×10 6 yuan(RMB) in 2004.Among all the ecosystem services indicators we estimated in this study, only fruit, timber and part of the recreation(which only include the tourism income from the forest parks and scenic areas, but not include that from other forest types) were measured in the social economic system.As estimated in this study, more than 82.19% of the economic value of forest ecosystem services could not be measured in the socio-economic statistical system.The importance of forest ecosystem services in Beijing to human welfare was underestimated by the socio-economic system.Therefore, the policies about the eco-compensation of forest ecosystem services should be established to maintain the sustainable supply of the forest ecosystem services in Beijing.  相似文献   

固原市森林多功能研究:潜力、挑战及利益权衡(英文)     

Hannes Jochen KOENIG 《资源与生态学报(英文版)》2010,(4):300-310

水土流失、人口激增和水资源短缺是制约中国西部固原市农村地区可持续发展的关键因素。为此,中国政府从1999年底开始实行退耕还林工程并于2003年完成第一阶段的计划任务。该工程以生态恢复为首要任务,同时兼顾减轻农村贫困及加快经济发展的目标。本研究旨在评估3种森林管理政策情景对当地可持续发展的潜在贡献和弊端,研究首先应用参与式影响评估框架(FoPIA)设定了3种森林管理政策情景,然后针对各个情景下土地利用的变化,进行了土地利用变化的影响评估。3种情景分别为"生态林"、"经济林(以种植水果为主的复合农林业)"和"生物能源林"。通过与当地利益相关者座谈,界定了与固原市可持续发展相关的9项重要森林功能,包括3项社会功能,即提供就业机会、生活质量、森林可达性;3项经济功能,即木材收入、非木材林产品收入、林业相关产业和服务收入;3项生态功能,即提供生物性资源、提供非生物性资源、生态过程维持。研究进一步通过多学科专家讨论和专家知识,评估了不同情景对森林功能的影响,探索了当地不同可持续发展目标间的权衡关系。结果显示:生态林可以达到生态恢复的首要目标,但是社会功能和经济功能较低;水果经济林对社会经济贡献大但对环境改善作用较小;生物能源林可以同时兼顾社会、经济和环境功能,但是在当地缺乏实践经验。基于专家观点,讨论了各情景的优势、劣势、机会和风险。研究发现,生态林树种选择需要重新考虑,并优先采用本土树种;水果经济林在经营得当情况下能促进社会经济发展;生物能源林在农户或村落尺度上提供清洁能源方面潜力巨大。  相似文献   

Trends of tropical deforestation in Southeast Mexico     

José Reyes Díaz‐Gallegos  Jean‐François Mas  Alejandro Velázquez 《Singapore journal of tropical geography》2010,31(2):180-196

We assessed deforestation in Southeast Mexico (a surface area of 29 000 km² in seven states) through the comparison of land use/land cover maps at a scale of 1:250 000. This facilitated mapping of the land use/land cover change (LULCC) processes and calculation of the rates of change and the change matrix for the period 1978–2000. An original method was used to assess the accuracy of the LULCC map. The verification sites were selected through a stratified random sampling and were corroborated with aerial photographs for 1978 and 2000. Error matrices were elaborated using both hard and fuzzy set approaches in order to take into account the errors related to generalization of the map in fragmented landscapes. The results showed an average annual deforestation rate of 1.1 per cent which represents an average annual loss of 190 000 ha of forest, or an estimated total reduction of 4.2 million ha over 22 years. Furthermore, deforestation processes are concentrated in some areas such as Yucatan and Chiapas states, which registered major forest conversions to grassland and slash‐burning. The overall accuracy of the LULCC map, assessed with hard and fuzzy set approaches, was 72 per cent and 88 per cent respectively.  相似文献