珠海市耕地变化时空特征及其驱动力分析

在RS和GIS技术支持下,利用1990、1995、2000和2006年共4期Landsat TM卫星遥感数据,分析珠海市耕地数量和空间变化特征,并探讨耕地动态变化的驱动因子.结果表明:珠海市耕地面积在3个研究时段经历了"快速减少一缓慢增加一急剧减少"的变化过程,人均耕地面积持续减少;2000-2006年耕地的动态度最大,而1995-2000年耕地的动态度相对较小;耕地面积增加的主要来源是水域和林地,减少的去向主要是农业结构调整中耕地转变成水域和建设用地;经济发展、人口增加和农业结构调整是珠海市耕地变化的主导驱动因素,同时政策因素也起到了重要的导向作用.     

Reponses and sensitivities of maize phenology to climate change from 1981 to 2009 in Henan Province,China

With the global warming, crop phenological shifts in responses to climate change have become a hot research topic. Based on the long-term observed agro-meteorological phenological data (1981–2009) and meteorological data, we quantitatively analyzed temporal and spatial shifts in maize phenology and their sensitivities to key climate factors change using climate tendency rate and sensitivity analysis methods. Results indicated that the sowing date was significantly delayed and the delay tendency rate was 9.0 d·10a^-1. But the stages from emergence to maturity occurred earlier (0.1 d·10a^-1<θ<1.7 d·10a^-1, θ is the change slope of maize phenology). The length of vegetative period (VPL) (from emergence to tasseling) was shortened by 0.9 d·10a^-1, while the length of generative period (GPL) (from tasseling to maturity) was lengthened by 1.7 d·10a^-1. The growing season length (GSL) (from emergence to maturity) was lengthened by 0.4 d·10a^-1. Correlation analysis indicated that maize phenology was significantly correlated with average temperature, precipitation, sunshine duration and growing degree days (GDD) (p<0.01). Average temperature had significant negative correlation relationship, while precipitation, sunshine duration and growing degree days had significant positive correlations with maize phenology. Sensitivity analysis indicated that maize phenology showed different responses to variations in key climate factors, especially at different sites. The conclusions of this research could provide scientific supports for agricultural adaptation to climate change to address the global food security issue.     

横断山区植物区系的基本特点

横断山区植物区系的基本特点为,植物种类多,古老植物多,特有植物多,地理成分复杂,各地理成分联系复杂,植物分化强烈。     

CHARACTERIZATION OF THE EFFECT OF PEAK SHIFTS ON THE PERFORMANCE OF THE KALMAN FILTER IN MULTICOMPONENT ANALYSES

The effect of peak shifts on the performance of a Kalman filter multicomponent analysis algorithm hasbeen investigated.A series of Gaussian test systems were employed to characterize the concentrationestimation errors and the morphology of the on-line residuals(the innovations sequence).Both forwardand reverse filters were used in the generation of the innovations sequences.It was found that thedifference between the forward and reverse innovations sequences gave an accurate indication of thedirection and magnitude of the peak shift.A series of overlapped two-component systems were alsoinvestigated.Again,a correlation between the difference innovations and the degree of the responseshift was observed.The behavior of the Katman filter in fitting the shifted fluorescence emissionspectrum of benzo[a]pyrene was also examined.The response for henzo[a]pyrene in cyclohexanesolution was compared to that obtained on the surface of a reversed phase thin layer chromatographyplate.A red shift of 4 nm was detected for the surface spectrum by observing the difference innovationssequence.This approach holds promise for correction of response shifts in multicomponent systems.     

1975-2015年鄂尔多斯市沙漠化的时空演变过程

鄂尔多斯市地处温带草原向荒漠草原过渡的半干旱区,是中国沙漠化问题较为严重的区域之一,其土地沙漠化发展和逆转过程及影响因素在北方农牧交错带具有代表性。以7期Landsat卫星遥感数据为信息源提取沙漠化土地类型及程度的时空格局信息,分析了该地区自1975年以来的土地沙漠化过程,并结合气象及社会经济数据采用主成分分析法对驱动因子进行定量分析。结果表明：在脆弱生态环境背景下,鄂尔多斯市土地沙漠化受人口数量增加、过垦及过牧等人为因素的严重影响。不同时段土地沙漠化发展的方向与驱动力都有所不同,1975-2000年是土地沙漠化的急剧发展期,驱动力以人为因素为主导,自然因素为基础;2000-2015年是土地沙漠化的逆转期,驱动力以自然因素为主,人为因素为辅。     

基于旅游开发影响的五台山植被景观特征分析

以往旅游对植被影响的评价成果较多,但是旅游影响下植被景观与地理因子之间的关系报道较少。本文利用多种数量生态学方法探讨了五台山旅游开发与植被景观之间的生态关系。结果表明：① 旅游开发影响下五台山植被景观可分为单优乔木区、草本区、差级乔草区、中级乔草区、中级灌草区、良级灌草区、良级乔灌草区、优级乔灌草区、以及寺庙区、商业区或居民区9种类型。② 在除趋势对应分析中,第一轴与所有因子的相关性都较大,第二轴与旅游干扰度和海拔呈显著的负相关性。各植被景观类型的空间分布在一定程度上取决于关键性指标的空间格局。③ 除趋势典范对应分析方法能够大大提高植被景观特征与地理因子间的相关性,并将其直观地表达于排序图中。在植被景观特征与地理因子的关系上,第一轴上的相关系数是0.858_DCCA>0.828_DCA,第二轴上的相关系数是0.583_DCCA>0.501_DCA,这说明除趋势典范对应分析方法更优。     

基于价值变化的城乡不动产征收博弈分析研究

不动产征收前后价值变化研究对于不动产征收主体博弈分析具有重要的意义,也为不动产征收补偿价格评估提供了理论支持。主要通过城乡不动产征收前后价值变化以及被征收人利益损害的分析,探讨了不同目的下的中国不动产征收主体博弈模型及行为选择。研究认为:(1)基于预期收益原则的不动产征收价格评估为不动产征收补偿与征收增值收益分配提供了理论依据;(2)基于公共目的性征收分析表明被征收人的权益保护很大程度上依赖于政府的角色定位,基于非公共目的性征收分析表明由于增值利益分配的零和博弈冲突以及政府的惯性强势思维,对现有政策体制不可避免地带来一系列冲突;(3)基于公共目的性划分的不动产征收与国家收购两种类型有利于区别制定不动产征收政策,从而促进土地资源的合理流动与优化配置。     

Constructing the Klamath: Nature,Culture, and the Management of a Western River

Despite decades of scientific research, stakeholder negotiations, and policy proposals, management of the Klamath River in southern Oregon and northern California remains hotly contested. This research examines the sociocultural dimensions of proposed removal of four Klamath River dams. Using a social constructivist approach to analyze the discourse of public comments regarding dam removal, I find commenters rely on diverse ideas of nature and divergent problem framings, contest the role of science, and draw on embedded and meaningful sociocultural narratives to legitimize their management preferences. These discourses shape the terrain upon which management actions are perceived, valued, and contested, and make management actions meaningful beyond their immediate spatial and temporal context. Dam removal on the Klamath River is far more than an ecological problem amenable to a scientific or technical approach; instead, it is a complex project shot through with the sociocultural identities, visions, and narratives of all involved.     

农业产业集群的演化阶段与形成机理分析——以宁夏中宁县枸杞加工产业为例

在总结前人研究基础上,借鉴国内外农业产业集群研究的相关理论,以宁夏中宁县枸杞加工产业集群为例,运用企业资料和半结构式访谈法,探讨了农业产业集群的演化阶段和形成机理。研究发现:(1)中宁县枸杞加工产业集群遵循农业产业集群演化的一般发展规律,经历了培育期、成长期及形成期,在不同的发展阶段集群表现出不同特征。(2)地区独特的资源禀赋、历史文化、宏观制度等偶然因素激发集群最初形成,地理临近导致的集聚效应促使集群逐步成长,收益递增引发的路径依赖则进一步促进集群的形成。(3)由于收益递增、路径依赖及企业惯例,集群在演化过程中可能会陷入低效率的锁定状态。为了摆脱这种困境,首先,政府应推动企业间网络合作强度及知识流动,提升集群创新能力;其次,要加强集群与区外联系实现集群在全球价值链上的嵌入,保持集群持续的竞争力。研究结果可为农业产业集群形成及机理研究提供借鉴,为宁夏枸杞加工产业发展提供指导。