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1.
利用2001—2018年的500 m分辨率的MOD13A1数据,计算每个像元的NDVI的变化趋势,并采用线性趋势分析法和相关性分析法,分析贵州省植被覆盖面积在18年间的时空变化特征;结合2001—2018年植被的降水利用效率与2010、2017年2期土地覆盖数据,研究不同土地覆盖类型的NDVI的特征. 研究结果表明:(1) 2001—2018年,贵州省的植被覆盖面积总体呈增加趋势,表明生态环境得以明显改善,以毕节、六盘水市最为显著;(2)从植被覆盖面积变化趋势来看,贵州省的植被改善区域大于退化区域,植被退化区主要集中在城镇扩张区;(3)贵州省的整体植被降水利用效率与植被覆盖面积的变化趋势不具有一致性;(4)贵州省的NDVI与同期降雨量、气温均呈现良好的相关性,而植被生长对气温变化不存在明显滞后性、对降雨量变化的滞后期为1个月,即植被生长对气温的敏感性高于降雨量;(5)在植被生长季,不同土地覆盖类型的NDVI具有不同的特征: NDVI(林地)>NDVI(耕地)>NDVI(草地)>NDVI(建设用地)>NDVI(水体).  相似文献   

2.
为确定2001-2011年间沈阳地区植被的分布特征和年际变化规律,采用NASA地球观测系统(EOS)提供的MODIS陆地植被指数产品MOD13A3,对沈阳地区进行分析,用归一化植被指数(NDVI)作为植被生长状态指标,以2001年植被指数为基准,用其它年份的植被指数与基准作差值处理,根据NDVI变化数据分级标准进行分级,分析了2001-2011年间沈阳地区植被的分布特征和年际变化规律.结果表明:沈阳地区植被覆盖密度由城区中心向周边逐渐增大;2001-2011年沈阳植被总体呈退化趋势;2002-2004年,沈阳城区边缘的植被有轻微退化外,其他地区植被均呈现中度和轻微改善;2005年以后沈阳市城区边缘的植被退化严重;在2008和2010年间,沈阳市周边地区如东陵区东南、苏家屯东南部、沈北新区西南部和于洪区东南部植被均有轻微和中度改善.  相似文献   

3.
淮河流域特殊的地理环境导致干旱灾害频发且持续时间长,严重影响该区域植被生长,而前人大多探讨了该区域气象干旱情况或植被生长状况,对二者之间的关系研究较少,且多采用气象站点降水资料进行干旱分析,不能充分反映降水时空分布的差异性。因此,基于MODIS NDVI遥感影像与TRMM 3B43卫星降水数据,采用降水距平百分率(P_a)作为气象干旱评价指标,分析了2001—2016年淮河流域植被NDVI与降水距平百分率的年际变化特征以及二者的相关性。结果表明:2001—2016年淮河流域植被NDVI总体呈现稳中有升的趋势,植被NDVI有所改善的区域比例为54.86%,NDVI基本不变的比例为43.25%,仅1.89%的NDVI出现退化。流域16年间以轻旱和中旱为主,较少出现重旱和特旱,干旱程度有所降低。植被NDVI和降水距平百分率呈正相关和负相关的区域分别占流域的61.31%和38.69%,正相关最显著的区域为河南省和安徽省的南部,而河南省东北部、安徽省西北部、山东省西部以及江苏省东部边界呈负相关关系。  相似文献   

4.
闫玉春  唐海萍 《自然科学进展》2008,18(5):2008546-2008551
通过实地样方调查及实验室分析对围封(ER)与持续放牧(GD)下内蒙古典型草原区退化草原群落的植被、土壤特征进行了测定,分析了围封后植被、土壤特征的恢复状况,揭示了退化草地生态系统恢复过程中的固碳潜力及其生物化学过程.结果表明:羊草(Leymus chinensis)草原退化变型——冷蒿(Artemisia frigida)草原经过18a围封,其植被和土壤特征得到明显恢复,地上组分总生物量是持续放牧草地的2.69倍,0—40cm土层中根系总生物量是持续放牧草地的1.55倍,表层(0—10cm)土壤粘、粉粒含量比持续放牧草地分别增加617.1%和394.7%,土壤有机碳、全氮、全磷含量分别增加为持续放牧草地的2.84,2.44和2.27倍,土壤容重比持续放牧草地降低了10.60%.在内蒙古典型草原区,长期过牧下的冷蒿草原恢复为以羊草为优势种的原生群落类型将具有较大的固碳潜力,在恢复过程中其地上植物组分、根系和土壤(0—40cm)的固碳潜力可分别达到65.58,241.77和2176.19g·m^-2,其植物——土壤系统总固碳潜力可达到2483.55g·m^-2.  相似文献   

5.
杨坤士  卢远  汤传勇 《科学技术与工程》2022,22(32):14148-14158
为探究我国南方丘陵山地流域植被覆盖度长时序变化情况,本研究基于1986—2020年Landsat系列影像数据,运用Google Earth Engine平台计算植被覆盖度FVC,利用Theil-Sen median趋势分析和Mann-Kendall 以及Hurst指数方法分析南流江流域植被覆盖度时空变化趋势特征。结果表明:南流江流域植被覆盖度高,植被覆盖度变化呈现明显的上升趋势。1986—2020年间,流域植被改善面积(58.23%)远远大于植被退化面积(8.29%),植被改善区域在流域中、下游表现最为显著,退化区域自流域上游而下依次减少。未来南流江植被覆盖度变化将呈现波动变化趋势,其中持续性改善面积占14.83%,持续性不变面积占12.25%,持续性退化面积占3.48%,余下69.44%面积为波动变化区域,流域植被覆盖变化与造林绿化工程及城市扩张发展息息相关。Google Earth Engine平台在遥感影像处理中有明显优势,它能在长时序、大尺度植被监测研究中发挥重要作用。  相似文献   

6.
基于时序NDVI的江西省植被覆盖时空变化分析   总被引:1,自引:0,他引:1  
基于NDVI时序遥感影像,分析了江西省1999年~2008年10年间的地表植被覆盖空间分布及其变化特征.研究表明,江西省10年来植被覆盖总体改善,但呈现出明显的空间分异性:西部和北部增长趋势明显,东部和南部部分地区以及部分城区呈退化趋势.结合土地覆盖分类数据分析发现,NDVI变化特征与土地覆盖类型密切相关,人类活动造成的土地利用类型变化是NDVI变化的重要驱动因素.  相似文献   

7.
基于植被净初级生产力(net primary productivity,NPP)和归一化植被指数(normalized difference vegetation index,NDVI)合成了综合草地等级指数(grassland degree index,GDI),计算了青藏高原2000-2015年草地质量变化的程度和速率,综合分析了草地退化的影响机制.研究表明:2000-2015年,青藏高原Ⅰ级(优质)草地区和Ⅳ级(劣质)草地区的面积比例基本保持不变;Ⅰ级草地区中约28.11%变为Ⅱ级;Ⅱ级草地区转化为Ⅰ级和Ⅲ级的比例分别为18.19%和21.53%;Ⅲ级草地区约有28.54%转变为Ⅳ级.由此可见,2000-2015年间,青藏高原草地经历了退化-恢复-退化的过程:高原北部大部分地区草地质量变化不明显,且呈现好转的趋势;南部和东部地区普遍出现草地退化现象,其中局部地区退化情况较为严重.  相似文献   

8.
基于3S技术的玛曲县草地植被覆盖度变化及其驱动力   总被引:5,自引:0,他引:5  
利用GIS空间统计分析、多元统计分析方法和改进的遥感二分像元估算模型估算了玛曲县高寒草地植被覆盖度。结果显示:玛曲县2000,2002,2004,2006,2008年的平均植被覆盖度依次为66.17%,56.41%,57.34%,77.38%,58.93%。玛曲县高寒草地植被覆盖度总体呈下降趋势,优等植被的退化比较严重。草地植被的演变情况主要由优等植被覆盖向劣等植被覆盖演变,进一步证实了玛曲县草地呈退化趋势。并对导致玛曲县高寒草地植被覆盖度变化的因素进行PCA分析,结果显示人为因素是导致玛曲县植被覆盖度变化的主要因素,进一步说明人类活动对玛曲高寒草地生态环境变化影响巨大。  相似文献   

9.
利用多源遥感数据,采用基于归一化植被指数的像元二分模型反演出1980、1998、2010、2014年4个时期的植被盖度,在此基础上分析并揭示黄河十大孔兑流域林草植被覆盖度的时空变化规律.结果表明:1)1980—2014年间,十大孔兑流域林草植被覆盖度呈现持续增加趋势,由1980年的9.29%提高至2014年的37.80%.1998年后,全流域林草植被盖度增加速率显著加快,林草植被盖度恢复主要表现为中等覆盖度的面积比例增加.2)近35年来,十大孔兑流域植被变化以稳定和完全恢复类型为主.研究区内完全恢复、恢复和轻微恢复3种植被变化类型占总面积的73.09%,严重退化、退化和轻微退化3种类型占总面积的2.72%.3)1980—2014年间,十大孔兑各个典型地理单元内林草植被盖度均呈增加趋势,除下游地区外均表现为1998年后林草植被盖度增加更为迅速.1980年,十大孔兑流域典型地理单元林草植被盖度由大到小排序为:上游西部、上游东部、下游、中游东部、中游西部.1998—2014年间典型地理单元林草植被盖度由大到小排序变化为:中游东部、上游东部、上游西部、中游西部、下游.1998年后实施的退耕还林(草)等工程是该地区植被覆盖度增加的主要原因.  相似文献   

10.
为了研究氮素添加对不同坡度退化高寒草地植被恢复的影响,对青海省三江源区果洛藏族自治州不同坡度(7°缓坡25°,陡坡25°)的退化高寒草地进行氮添加试验,以探讨外源氮添加技术在不同坡度退化高寒草地植被恢复中的适宜性。结果表明:氮添加能提高植被地上生物量、植被高度、多度、总盖度以及物种分盖度之和,氮添加与坡度间的交互作用能显著改变植被地上生物量和平均高度(P0.05);坡度间植被特征存在显著差异(P0.05),氮添加可促进禾草类物种优势度更低的缓坡地的植被恢复,而对禾草类物种相对重要值更高的陡坡地没有显著影响。在退化高寒草地的恢复中,外源氮添加的促进效应依赖于坡度,更适宜于缓坡退化高寒草地的植被恢复。  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

14.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

15.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

16.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

17.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

18.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

19.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

20.
The non-orthogonal localized molecular orbital(NOLMO)is the most localized representation of electronic degrees of freedom.As such,NOLMOs are thus potentially the most efficient for linear scaling calculations of electronic structures for large systems.However,direct ab initio calculations with NOLMO have not been fully implemented and widely used,partly because of the slow convergence issue in the optimization of NOLMO.We devel-  相似文献   

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