GIS支持下岷江上游土壤侵蚀动态研究

利用TM数据,采用3S技术和通用土壤侵蚀方程(RUSLE)研究岷江上游地区3个典型时期的土壤侵蚀动态,并对影响侵蚀的主要因子进行初步分析.结果表明,研究区3个时期侵蚀面积分别占研究区总面积的1.28%、1.84%和1.70%;年平均侵蚀模数分别为832.64、1048.74和1362.11t.km-2,以微度侵蚀、轻度侵蚀为主,伴有少量的中度侵蚀.侵蚀面积比较小,侵蚀程度比较轻.侵蚀与坡度呈显著正相关,侵蚀大多发生在>25°的区域,1986年占总侵蚀量的93.65%,1995年为93.81%,2000年为92.71%;在海拔上,中山、亚高山、高山以及干旱河谷是侵蚀发生的主要地带,1986年占总侵蚀量的98.21%,1995年为97.63%,2000年为99.27%;不同类型的植被直接影响到侵蚀的发生,灌木林地以及新退耕的疏林地是3个时期侵蚀的主要发生地,过度放牧导致草场退化,也产生了微度侵蚀;侵蚀的发生和土壤类型密切相关,燥褐土、石灰性褐土最易发生侵蚀,是控制侵蚀的重点区域;人口的增长、户数的增加是侵蚀发生的驱动因子,人口与户数增长导致资源需求压力的增大,侵蚀呈线性增加.

基于TM的渤海海岸带1988~2000年生态环境变化

海岸带作为海陆之间的过渡地带,是全球生态环境最为复杂和特殊之处。研究海岸带土地利用变化对于了解该区域生态环境演变具有重要意义。利用1988和2000年的Landsat-TM数据,在GIS技术支持下,通过一系列空间分析,得到渤海海岸带土地利用/土地覆盖变化,结合社会经济统计资料分析该区域生态环境的动态变化情况及其驱动因素。结果表明,1988~2000年,由于渤海海岸带社会经济的快速发展,海岸带土地利用格局发生了巨大的变化。耕地大面积减少,城乡工矿用地、养殖池塘、盐田急剧扩张;林地、湿地等具有重要生态价值的土地类型面积显著下降。表明强烈的人类活动已经使自然生态系统受到破坏,渤海海岸带生态环境质量总体上呈现下降趋势。

基于TM影像的表层土壤有机碳空间格局

土壤有机碳是土壤肥力的核心指标之一,理解其空间分布格局对促进精准农业的发展和科学施肥具有重要意义。本研究旨在检验TM影像结合地面采样数据分析黑龙江省黑土分布区表层土壤有机碳空间分布格局的可行性。结果表明:1)表层土壤有机碳浓度与TM5波段呈显著正相关(r=0.553,P<0.01),与TM4、TM5波段影像像素值之间满足二次多项式回归关系(R2=0.6791,P<0.05);2)回归模型对表层土壤有机碳空间分布格局具有较好的预测效果(R2=0.7097,P<0.05);3)海拔高于200m的地区表层土壤有机碳浓度显著高于海拔低于200m的地区(P<0.05)。

基于TM影像和统计分析的林分参数估测研究(英文)

林业研究中的主要兴趣点之一在于通过经验或半经验模型建立林分参数与遥感影像数据间的相互关系来估测林分参数。基于覆盖美国佛罗里达州东北Duval县的遥感数据和两块样地清查数据,论文探讨了所选林分参数与TM影像光谱DN值间的相关性。相关性分析结果表明,单波段或植被指数对林分参数的解释能力低于50%,为此构建了林分参数与影像多波段间多元回归模型来估测林分参数。预测结果通过另一组数据验证,除林分密度外,其它参数估测可信度达75%以上。论文最后探讨了预测模型不足和需改进的地方,并指出该研究有助于更好地理解影像光谱值和林分参数间的关系。图1表2参9。

松辽平原中部地区农田防护林立地分类及质量评价的研究

本文利用多元回归和逐步回归分析方法,确定了影响松辽平原中部地区农田防护林生长的主导因子,南部类型区为土壤含盐量多少,北部类型区为有机质和水分。并采用综合多因子方法对本地区的立地类型进行分类。同时根据土地指数和TM数字图像信息评价了立地质量。

近30年来青海三江源地区草地退化的时空特征

在20世纪70年代中后期MSS图像、90年代初期TM图像和2004年TM/ETM图像支持下,通过三期遥感影像的直接对比分析,获得了三江源地区草地退化空间数据集,并在此基础上分析了70年代以来青海三江源地区草地退化的主要时空特征。结果表明:三江源地区草地退化是一个在空间格局上影响范围大,在时间过程上持续时间长的连续变化过程。研究发现,三江源草地退化的格局在70年代中后期已基本形成,70年代中后期至今,草地的退化过程一直在继续发生,总体上不存在90年代至今的草地退化急剧加强现象。草地退化的过程在不同区域和地带有明显不同的表现,如在湿润半湿润地带的草甸类草地上,发生着草地破碎化先导,随后发生覆盖度持续降低,最后形成黑土滩的退化过程;在干旱、半干旱地带的草原类草地上,发生着覆盖度持续降低,最后形成沙地和荒漠化草地的退化过程。三江源地区草地退化具有明显的区域差异,草地退化可以分为7个区,各区草地退化在类型、程度、范围与时间过程方面具有明显不同的特点。

Analysis of spatio-temporal dynamic pattern and driving forces of urban land in China in 1990s using TM images and GIS

China has witnessed fast urban growth in the recent decade. This study analyzes spatio-temporal characteristics of urban expansion in China using satellite images and regionalization methods. Landsat TM images at three time periods, 1990/1991, 1995/1996, and 1999/2000, are interpreted to get 1:100000 vector land use datasets. The study calculates the urban land percentage and urban land expansion index of every 1 km(2) cell throughout China. The study divides China into 27 urban regions to conceive dynamic patterns of urban land changes. Urban development was achieving momentum in the western region, expanding more noticeably than in the previous five years, and seeing an increased growth percentage. Land use dynamic changes reflect the strong impacts of economic growth environments and macro-urban development policies. The paper helps to distinguish the influences of newly market-oriented forces from traditional administrative controls on China's urban expansion. (c) 2005 Elsevier Ltd. All rights reserved.

Uncertainties in estimates of cropland area in China: a comparison between an AVHRR-derived dataset and a Landsat TM-derived dataset

The large uncertainties in estimates of cropland area in China may have significant implications for major cross-cutting themes of global environmental change-food production and trade, water resources, and the carbon and nitrogen cycles. Many earlier studies have indicated significant under-reporting of cropland area in China from official agricultural census statistics datasets. Space-borne remote sensing analyses provide an alternative and independent approach for estimating cropland area in China. In this study, we report estimates of cropland area from the National Land Cover Dataset (NLCD-96) at the 1:100,000 scale, which was generated by a multi-year National Land Cover Project in China through visual interpretation and digitization of Landsat TM images acquired mostly in 1995 and 1996. We compared the NLCD-96 dataset to another land cover dataset at I-km spatial resolution (the IGBP DIScover dataset version 2.0), which was generated from monthly Advanced Very High Resolution Radiometer (AVHRR)-derived Normalized Difference Vegetation Index (NDVI) from April, 1992 to March, 1993. The data comparison highlighted the limitation and uncertainty of cropland area estimates from the DIScover dataset. (C) 2003 Elsevier Science B.V. All rights reserved.

The characteristics of land cover and macroscopical ecology changes in the source region of three rivers in Qinghai-Tibet plateau during last 30 years

We obtained four phases of land cover spatial data sets by interpreting MSS images of middle and late 1970s and three phases of TM images of late 1980s, 2004 and 2008 based on field investigation in Three Rivers' Source Region. We analyzed the temporal and spatial characteristics of land cover and macro ecological changes in Three Rivers' Source Region in Qinghai-Tibet plateau since middle and late 1970s. Indicated by land cover condition index change rate and land cover change index, land cover and macroscopical ecological condition degenerated (7090 period Zc -0.63, LCCI -0.58)-obviously degenerated (9004 period, Zc -0.94, LCCI -1.76)-slightly meliorated (0408 period, Zc 0.06, LCCI 0.33). This course was jointly driven by climate change, grassland stocking pressure and implement of ecological construction project.

Synthesis and Luminescent Properties of LaAlO3:RE3+ (RE = Tm, Tb) Nanocrystalline Phosphors via a Sol-Gel Process

LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors were prepared through a Pechini-type sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photoluminescence, and cathodoluminescence (CL) spectra were utilized to characterize the synthesized phosphors. The XRD results reveal that the fully crystalline pure LaAlO3 Phase can be obtained at 800 degrees C. The FE-SEM image indicates that the phosphor samples are composed of aggregated spherical particles with sizes ranging from 40 to 80 nm. Under the excitation of ultraviolet light (230 nm) and low-voltage electron beams (1-3 kV), the LaAlO3:Tm3+ and LaAlO3:Tb3+ phosphors show the characteristic emissions of Tb3+ (D-1(2)-> H-3(6,4),F-3(4) transitions) and Tm3+ (D-5(3,4)-> F-7(6,5,4,3) transitions) respectively. The CL of the LaAlO3:Tm3+ phosphors have high color purity and comparable intensity to the Y2SiO5:Ce3+ commercial product, and the CL colors of Tb3+-doped LaAlO3 phosphors can be tuned from blue to green by changing the doping concentration of Tb3+ to some extent.

Self-assembled 3D flowerlike Lu2O3 and Lu2O3 : Ln(3+) (Ln = Eu, Tb, Dy, Pr, Sm, Er, Ho, Tm) microarchitectures: Ethylene glycol-mediated hydrothermal synthesis and luminescent properties

Three-dimensional flowerlike Lu2O3 and Lu2O3:Ln(3+) (Ln = Eu, Th, Dy, Pr, Sm, Er, Ho, Tm) microarchitectures have been successfully synthesized via ethylene glycol (EG)-mediated hydrothermal method followed by a subsequent heat treatment process. X-ray diffraction, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectra, thermogravimetric and differential thermal analysis, elemental analysis, inductively coupled plasma atomic absorption spectrometric analysis, ion chromatogram analysis, X-ray photoelectron spectra, scanning electron microscopy, transmission electron microscopy, photoluminescence spectra as well kinetic decays, and cathodoluminescence spectra were used to characterize the samples. Hydrothermal temperature, EG, and CH3COONa play critical roles in the formation of the lutetium oxide precursor microflowers. The reaction mechanism and the self-assembly evolution process have been proposed. The as-formed lutetium oxide precursor could transform to Lu2O3 With their original flowerlike morphology and slight shrinkage in the size after postannealing process.

Four New Lanthanide-Nitronyl Nitroxide (Ln(III)=Pr-III, Sm-III, Eu-III, Tm-III) Complexes and a Tb-III Complex Exhibiting Single-Molecule Magnet Behavior

Five new complexes based on rare-earth-radical [Ln(hfac)(3)(NIT-5-Br-3py)](2) (Ln=Pr (1), Sm (2), Eu (3), Tb (4), Tm (5); hfac = hexafluoroacetylacetonate; NIT-5-Br-3py = 2-(4,4,5,5-tetramethyl-3-oxylimidazoline-1-oxide)-5-bromo-3-pyridine) have been synthesized and characterized by X-ray crystal diffraction. The single-crystal structures show that these complexes have similar structures, in which a NIT-5-Br-3py molecule acts as a bridging ligand linking two Ln(III) ions through the oxygen atom of the N-O group and nitrogen atom from the pyridine ring to form a four-spin system. Both static and dynamic magnetic properties were measured for complex 4, which exhibits single-molecule magnetism behavior.

Highly uniform and monodisperse beta-NaYF4 : Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprism crystals: Hydrothermal synthesis and luminescent properties

beta-NaYF4:Ln(3+) (Ln = Eu, Tb, Yb/Er, and Yb/Tm) hexagonal microprisms with remarkably uniform morphology and size have been synthesized via a facile hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. It is found that sodium citrate as a shape modifier introduced into the reaction system plays a critical role in the shape evolution of the final products. Furthermore, the shape and size of the products can be further manipulated by adjusting the molar ratio of citrate/RE3+ (RE represents the total amount of Y3+ and the doped rare earth elements such as Eu3+, Tb3+, Yb3+/Er3+, or Yb3+/Tm3+). Under the excitation of 397 nm ultraviolet light, NaYF4:xEu(3+) (x = 1.5, 5%) shows the emission lines of Eu3+ corresponding to D-5(0-3) -> F-7(J) (J = 0-4) transitions from 400 to 700 nm (whole visible spectral region) with different intensity, resulting in yellow and red down-conversion (DC) light emissions, respectively.