Continuity and discontinuity of the riparian vegetation along a fluvial corridor

The concept of continuity/discontinuity is applied to the riparian vegetation of the corridor of the River Adour (S.W. France), in order to precisely define longitudinal structure, and to test the degree of floristic continuity of the fluvial axis. The measure of floristic connectance along the river course is based on presence/absence data, and is applied to successive stretches of the river, at various resolution levels. This analysis shows that the River Adour corridor cannot be assumed to be floristically continuous. The observed discontinuities may correspond to two types of change in the riparian vegetation: zones of slow change (high level of floristic connectance) or zones of sharp change (low level of floristic connectance).     

“利他行为”新解

把利他行为和利己行为放在相对立的位置上，这是绝大多数人所持的观点，也是一些学者所推崇的观点。本文另辟蹊径，在分析把两者放在相对立的位置上理解利他行为所遇到困境的基础上，从利己行为和利他行为是一个由低层次到高层次不断深化和发展或者说是一个行为意义上的‘连续统”的角度，对利他行为作新的诊释。     

Organic Carbon and Total Iron Effect on Soil Vis-SWNIR Spectraand Quantification of Their Contents Using PLS R Models

ABSTRACT

Many factors could influence simultaneously soil spectra. We aimed to study the single effect of organic carbon and total iron in soil visible and short-wave near-infrared spectra and to quantify their contents. Two datasets of soil mixture samples were prepared by mixing, in various fractions, an organic carbon-rich material with a total iron-rich material and then with a total iron-poor material. For these two datasets, contents in organic carbon are quite similar but contents in total iron are significantly different. Results show that samples of the same dataset have the same overall spectral shape. Organic carbon has a decreasing effect that affects the whole spectral range without showing any specific absorption peaks. By contrast, total iron has specific absorption peaks. Spectra of the second dataset characterized by soil mixtures with higher total iron contents were more compact within the spectral bands 400–440 and 920–950 nm. Besides, continuum removal enables to exaggerate absorption peaks of wavelengths linked to total iron content. Partial Least Squares Regression (PLS R) models of both total organic carbon and total iron assign high coefficients to the wavelengths that are considered relevant and conversely low coefficients to those that are considered irrelevant. Both organic carbon content and total iron content were well predicted. For these models, coefficients of determination were superior to 0.9 and RMSE was closed to zero. The global models calibrated on all the samples demonstrated that PLS R was able to integrate sample heterogeneity.     

人地协同视角下的成都平原统筹城乡土地利用战略研究

基于人地协同视角,运用系统分析方法,诊断成都平原城乡统筹进程中的土地利用问题,提出区域土地利用战略框架。结果表明:成都平原人地关系整体上不协同,人地"剪刀差"负效应有扩大趋势、土地利用总体较粗放、土地利用规划与相关规划缺乏有效衔接、部分地域功能模糊、农村生境问题突出和非农就业不畅等,都是区域城乡统筹进程中人地关系协同发展的制约因素。基于此,应通过统筹区域土地利用战略、农村土地节约集约利用战略、农村土地生态整治修复战略和农村土地制度创新战略,构建统筹城乡土地利用战略体系,促进成都平原人地关系协同有序发展。     

基于连续统去除和偏最小二乘回归的油菜SPAD高光谱估算

【目的】探讨油菜叶绿素含量的高光谱估算方法,为实现油菜叶片叶绿素含量的高效、无损、大面积监测提供理论依据。【方法】以陕西省关中地区油菜叶片为研究对象,分别测定苗期、蕾薹期、开花期及角果期的叶片高光谱数据和SPAD值,提取各生育期连续统去除光谱和7类光谱吸收特征参数,分析原始光谱、连续统去除光谱、光谱吸收特征参数与SPAD值之间的相关关系,构建基于原始光谱特征波段、连续统去除光谱特征波段、光谱吸收特征参数的SPAD估算模型,并对模型精度进行验证。【结果】在可见光范围,光谱反射率由蕾薹期、开花期、苗期到角果期依次递增,最大吸收深度和吸收谷面积逐渐增大。利用连续统去除光谱特征波段与吸收特征参数,分别建立的油菜各生育期叶片SPAD估算模型均优于原始光谱。运用连续统去除光谱特征波段结合最优吸收特征参数构建的偏最小二乘回归估算模型,是进行油菜叶片SPAD估算的最优模型。【结论】连续统去除法对不同生育期油菜叶片叶绿素相对含量具有较好的预测能力,是估算油菜叶片SPAD值的一种实时高效方法。     

当代中国劳动力乡城流动中存在的问题及对策

分析了当代中国劳动力乡城流动中存在的一系列问题,并提出了相关的对策。     

影响苏北地区城乡收入差距的教育因素探析

阐述了苏北地区城乡收入差距的现状,从教育因素分析了受教育程度低和观念落后是城乡收入差距扩大重要原因。提出了加大苏北农村基础教育投入,加强农村的社会主义精神文明建设,提高农民的思想素质和文化素质,造就有文化、懂技术、会经营的新型农民,以缩小苏北地区城乡收入差距。     

基于粗糙集和信息熵的土地适宜性评价研究

将信息熵理论与粗糙集技术引入土地适宜性评价领域,通过计算指标的信息量,为指标权重的确定提供科学依据,从而有效地避免指标权重确定过程中的主观性。通过福建省武平县城乡建设用地适宜性评价的实际应用进一步验证该方法的有效性,为土地适宜性评价开拓一种新的思路。     

农村与城市的连续——打破“城中村”的禁锢

通过探究城市背景下的＂城中村＂现状及与国外城市村庄进行对比,寻找到打破＂城中村＂禁锢的设计方法,重拾霍华德的＂田园城市＂理论,最终实现农村与城市的可持续发展。     

滨海新区城乡一体化进程中农村产业升级的路径选择

运用查阅资料和实地调研相结合的方法,分析了天津滨海新区城乡一体化进程中农村产业发展现状,指出新区一体化进程中存在突破城乡二元结构困难、区域内经济发展不均衡、第三产业发展滞后等问题。并提出了相应的对策：优化农业产业结构,推动农业产业化,形成设施农业、园区农业、高端农业为主的滨海都市型农业模式,实现农业集约发展;合理布局农村工业结构,形成区域主导产业,发挥工业带动作用,实现工业调整发展;加快以服务业为主的第三产业建设,形成现代农村服务业体系,使现代服务业成为主导产业,实现第三产业飞跃发展。