风浪作用下水生植物对水流结构的影响——以太湖中两种典型沉水植物为例   总被引：1，自引：3，他引：1       下载免费PDF全文

张英豪  赖锡军  张琳  姚昕  邓焕广 《水科学进展》1990,31(3):441-449

为研究风浪作用下水生植物对水流结构的影响，选取太湖中两种典型沉水植物（苦草与马来眼子菜）为研究对象，分别对苦草植物斑块与马来眼子菜植物斑块内外水体的瞬时流速进行野外现场测量，利用瞬时流速的能量谱分布将波浪流速与紊动流速分离，分别分析水生植物对时均流速、波浪流速以及紊动能的影响。风浪影响下，水体中存在流向与测量时近水面处盛行风向一致的水流；波浪流速以垂向流速为主，且波浪流速自水面向床底逐渐减小；紊动能在水面处达到最大值，并向床底方向逐渐减小。与无植被条件相比，苦草与马来眼子菜的存在减小了时均流速、波浪流速以及紊动能。两种植物形态上的差异，导致其对水流结构的影响不同：苦草叶片阻流面积在冠层中部达到最大，使得时均流速与波浪流速在苦草中部位置的减小程度最大；马来眼子菜叶片主要集中于冠层顶部（水面附近），其对时均流速以及波浪流速的减小作用在水面处达到最大。  相似文献   

灌木植被分布区阻力特性理论及试验研究   总被引：1，自引：2，他引：1       下载免费PDF全文

陆彦  王唯旭  陆永军  宋云涛  鄢栋梁 《水科学进展》1990,31(4):556-564

为探明河道灌木植被分布区阻水规律，对灌木植被主干、分枝产生的水流阻力特性及其定量特征进行研究。提出原型植被体积修正系数和灌木植被水力半径确定方法，理论推导灌木植被阻力系数计算公式，并结合水槽试验建立植被阻力系数与植被水力半径为特征长度的植被雷诺数之间的关系式。研究结果表明：引入原型植被体积修正系数和灌木植被水力半径使灌木植被阻力计算更为准确；植被阻力系数与植被雷诺数之间呈指数函数关系，随植被雷诺数的增加呈单调减小的趋势，与水槽试验结果吻合很好。  相似文献   

利用NOAA－AVHRR资料提取水体信息的初步研究     

杨忠恩  骆剑承  徐鹏炜 《国土资源遥感》1995,6(1):31-34

本文讨论了应用NOAA-AVHRR资料来提取水体信息的方法。采用AVHRR一、二通道(下面简写为CH1、CH2)获得的地面反射率数据构成的归一化植被指数(NDVI)来识别水体,并初步提出了应用模糊数学的方法提取混合像元中的水体面积信息的技术思路。  相似文献   

植物物候遥感监测精度影响因素研究综述   总被引：5，自引：1，他引：4  

范德芹  赵学胜  朱文泉  郑周涛 《地理科学进展》2016,35(3):304-319

基于植物物候的遥感监测对于研究植被对气候变化的响应具有重要的科学价值。本文在阐述植物物候遥感监测原理及其通用技术流程的基础上,分别从植被类型及其所处的地理条件、遥感数据源及其预处理、植物物候遥感识别方法和植物物候遥感监测结果评价4个方面分析了影响植物物候遥感监测精度的因素,并针对当前研究中存在的不足,探讨了提高植物物候遥感监测精度的可行性途径,即建立高分辨率的近地面遥感定点观测及数据共享网络,发展普适性更强的卫星遥感时序数据去噪及植被指数曲线重建方法,寻求稳定性更高的植物物候期遥感识别方法,探索综合运用地面观测、遥感监测与模型模拟实现物候观测空间尺度拓展的可能性。  相似文献   

森林景观模型研究新进展及其应用   总被引：1，自引：0，他引：1  

奚为民  戴尔阜  贺红士 《地理科学进展》2016,35(1):35-46

森林景观模型(forest landscape models)是基于森林动态机制和干扰作用在景观尺度上模拟和预测森林时空变化特征的计算机模型。该类模型越来越多地用于森林规划、经营管理、生态资源保护与恢复及全球气候变化研究。本文通过对大量文献资料的整理,对森林景观模型的概念、尺度、类型、方法、应用和最新研究进展进行了综述。随着计算机、地理信息系统、遥感等技术的迅猛发展,森林景观模型将会越来越多地与地理信息系统、规划经营管理决策等紧密结合,未来将向服务性决策模型方向发展。  相似文献   

Soil water deficit and vegetation restoration in the refuse dumps of the Heidaigou open-pit coal mine, Inner Mongolia, China   总被引：1，自引：0，他引：1  

Lei Huang  Peng Zhang  YiGang Hu  Yang Zhao 《寒旱区科学》2016,8(1):22-35

The sustainability of ecosystem restoration of refuse dumps in open-pit coal mines depends on plant species selection, their configuration, and the optimal usage of water resources. This study is based on field experiments in the northern refuse dump of the Heidaigou open-pit coal mine in Inner Mongolia of China established in 1995. Eight plant configurations, including trees, shrubs, grasses, and their combinations, as well as the adjacent community of natural vegetation, were selected. The succession of the revegetated plants, soil water storage, the spatiotemporal distribution of plant water deficits degree and its compensation degree were also studied. Results indicated that the vegetation cover (shrubs and herbaceous cover), richness, abundance, soil nutrients (soil organic matter, N and P), and biological soil crust coverage on the soil surface are significantly influenced by the vegetation configurations. The average soil water storage values in the shrub+grass and grass communities throughout the growing season are 208.69 mm and 206.55 mm, which are the closest to that of in the natural vegetation community (215.87 mm). Plant water deficits degree in the grass and shrub+grass communities were the lowest, but the degrees of water deficit compensation in these configuration were larger than those of the other vegetation configurations. Differences in plant water deficit degree and water compensation among the different configurations were significant (P<0.05). Plant water deficit degrees were predominantly minimal on the surface, increased with increasing soil depth, and remained stable at 80 cm soil depth. The soil moisture compensation in the natural vegetation, shrub+grass, and grass communities changed at 10%, while that in other vegetation communities changed between 20% and 40%. Overall, we conclude that the shrub+grass and grass configuration modes are the optimal vegetation restoration models in terms of ecohydrology for future ecological engineering projects.  相似文献   

夏玉米生长过程曲线重建研究——以鹤壁市为例     

李颖  李耀辉  王金鑫 《气象与环境科学》2016,39(4):7-13

增强型植被指数(EVI)时间序列数据(即植被生长曲线)是整个生育期内植被各种生物学特征的综合反映。由于太阳位置、大气、地表和传感器位置与性能等的影响,根据遥感数据计算的EVI值往往比实际值偏低(存在大量噪声),并不能反映植被生长的真实情况,应用前需进行去噪重建工作。针对目前生长曲线重建研究大多是针对MODIS等国外遥感数据的情况,在综合分析重建方法的基础上,利用风云3号卫星的MERSI中分辨率遥感卫星数据构建鹤壁市夏玉米的EVI生长过程曲线。首先,用最大值合成法(MVC)对原始EVI时间序列数据进行初步的去云处理。接着,利用基于时间域的Savitzky-Golay滤波(简称SG滤波)对该EVI序列进行进一步的平滑去噪处理,结果发现,在噪声点EVI数值提高了,但同时在其他不是噪声点的地方EVI的值降低了。针对这种不合理的情况,利用基于SG迭代滤波取上包络线的改进方法进行处理,很好地克服了上述缺陷,在非噪声点EVI数值适当提高,且曲线平滑,达到了生长曲线重建的目的。然后,采用基于频率域的小波变换方法进行实验对比,结果发现,小波变换存在着与经典SG滤波类似的缺陷,而且在曲线末端存在突变情况。经过比较分析发现,针对研究区的实际情况,改进SG迭代滤波是较优的去噪方法。  相似文献   

黄土区切沟对不同植被下土壤水分时空变异的影响   总被引：2，自引：0，他引：2       下载免费PDF全文

张晨成  邵明安  王云强  贾小旭 《水科学进展》2016,27(5):679-686

为掌握切沟对土壤水分时空变异的影响,选取水蚀风蚀交错区两个典型切沟样点为研究对象。采用时间序列分析和经典统计学方法,从土壤水分时间变化特征和空间分布格局两方面探讨。结果表明:距沟道不同距离下土壤储水量差异明显。300 cm处样点可作为测定尺度下土壤储水量平均值。土壤水分在垂直方向上的变异受植被特征影响,沟道影响较小。坡面土壤储水量的空间分布呈现不同的分布格局。坡顶风速大,土壤水分蒸发快,坡中处土壤储水量最高,为949.9 mm,距切沟越近土壤水分快速散失,坡下土壤水分接近4%,亏缺严重。杏树地土壤储水量远高于柠条地,柠条地土壤储水量分布较为单一。土壤蒸发、植被、沟道等因素使得坡面土壤水分分布更加复杂。  相似文献   

Submerged vegetation complexity modifies benthic infauna communities: the hidden role of the belowground system          下载免费PDF全文

Vanessa González‐Ortiz  Luis Gonzalo Egea  Rocio Jiménez‐Ramos  Francisco Moreno‐Marín  José Lucas Pérez‐Lloréns  Tjeerd Bouma  Fernando Brun 《Marine Ecology》2016,37(3):543-552

Marine plants provide a variety of functions with high economic and ecological values in ecosystems. The above‐ (AG) and below‐ground (BG) systems increase the structural complexity of plants, which also enhance faunal abundance and diversity. The ecological role of the AG compartment in structuring inter‐tidal macrobenthic communities has been widely studied; however, this is not the case for the BG compartment. This study addressed the effects of variation in vegetation complexity (in both AG and BG systems) on associated macrobenthic infauna with respect to abundance, species richness, composition, weight and body type. To achieve this aim, a field experiment using artificial vegetation mimics was carried out using replicated treatments with different AG‐BG complexity ratios. We found a significant increase in the density and the number of taxa of macrobenthic infaunal species in plots with vegetation mimics compared with unvegetated areas, regardless of either AG or BG complexity. This effect was found even when AG parts were not present (i.e. when only BG parts were used). Furthermore, a positive relationship between structural complexity and diversity was recorded. Variation in one or both plant compartments was strongly related to diversity changes in the associated macrobenthic infauna. In conclusion, our experimental set‐up provides the first evidence that the BG compartment is at least as important as the AG compartment in controlling diversity in inter‐tidal vegetated areas because it was able to strongly affect community structure even when the AG system was totally absent.  相似文献   

Strengthened African summer monsoon in the mid-Piacenzian     

Ran Zhang  Zhongshi Zhang  Dabang Jiang  Qing Yan  Xin Zhou  Zhigang Cheng 《大气科学进展》2016,33(9):1061-1070

Using model results from the first phase of the Pliocene Model Intercomparison Project (PlioMIP) and four experiments with CAM4, the intensified African summer monsoon (ASM) in the mid-Piacenzian and corresponding mechanisms are analyzed. The results from PlioMIP show that the ASM intensified and summer precipitation increased in North Africa during the mid-Piacenzian, which can be explained by the increased net energy in the atmospheric column above North Africa. Further experiments with CAM4 indicated that the combined changes in the mid-Piacenzian of atmospheric CO₂ concentration and SST, as well as the vegetation change, could have substantially increased the net energy in the atmospheric column over North Africa and further intensified the ASM. The experiments also demonstrated that topography change had a weak effect. Overall, the combined changes of atmospheric CO₂ concentration and SST were the most important factor that brought about the intensified ASM in the mid-Piacenzian.  相似文献