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1.
AN OVERVIEW ON THE URBAN-RURAL INTERACTION IN THE PAST 50 YEARS IN CHINA   总被引:4,自引:0,他引:4  
1INTRODUCTIONBydefinitionurbanizationistheprocessofruralareaschangingintourbanareasinnatureforasoci-etyitisanaturallyhistoricalprocessofthetransitionfromatraditionalruraloragriculturalsocietytoamodernizedurbansocietyGAO1991.Inbriefitrepresentsa…  相似文献   

2.
1INTRODUCTIONGeothermalanomalyisaphenomenonthatunder-groundtemperatureandgeothermalgradientincreasesmuchmoreintheareathanitssurroundingsXIA1979.Thisisanormalglobalphysicalphenomenonintheactiveandthelatentvolcanicarea.Duringthewarningsignperiodofan…  相似文献   

3.
I.INTRODUCTIONCitiesarethesymbolsofhuman’scivilization,thespatialcariersofeconomyandthesourcesofregionaleconomicactivities(Gu...  相似文献   

4.
1INTRODUCTIONJianghanPlainisoneoftheimportantbasesofChina′sagriculturalproductivitylocatedinthemiddleChangjiangRivervalleyofcentralChina.TheJianghanplainapproximately6.6×104km2inareaandover30millioninpopulationistherenowned“countryoffishandrice"in…  相似文献   

5.
STUDY ON WETLAND LOSS AND ITS REASONS IN CHINA   总被引:2,自引:2,他引:0  
1INTRODUCTIONWetlandsaretheecosystemswithmanyfunctionsandhavebeenprovidinguswitharangeoffunctionsandbenefitssuchaswatersupplyflowregulationsendimentretentionmoderationofclimatepreventionofsalinewaterintrusionetc.Althoughwetlandoccupyonlyabout6%…  相似文献   

6.
1INTRODUCTIONNoonecandoubtthatoneofthemostexcitingsoundsinnineteenthcenturyAmericawasthewhistleofalocomotive.ThroughoutthewholecenturyespeciallyinthesecondhalfrailroadsplayedadramaticroleintransformingtheAmericanwestfromabarrenlandintoapopulatedone…  相似文献   

7.
INTRODUCTIONChlorinehastwonaturallyoccuringstableisotopes, 35Cland 37Cl.Severalstudiesreportedthevariationsintheisotopiccompositionofchlorineinnature.However,intheearlyyearsOwenandSchaeffer(1955)reportednoobservabledifferenceinthe 37Cl35Clratiosintensamplesex…  相似文献   

8.
1INTRODUCTIONInecosystemfragileecoenvironmentisdefinedasthe“interface"betweentwoormoresystemsofmatterenergystructureorfunctionandthetransitionregionextendingfromthisinterfaceNIU1989.ThefragileecoenvironmentoftheSongnenPlainissitu-atedonsuch…  相似文献   

9.
1INTRODUCTIONTheremarkablesocialandeconomicchangeinthePearlRiverZhujiangDeltaPRDsincethelate1970shasmadeitafocalpointinreformeraacademiccircles.ManystudieshavebeendoneonthePRDitsregionaleconomicdevelopmentandrestructuringLIN1997LINetal.1995…  相似文献   

10.
I.INTRODUCTIONThereisaclosecorelationbetweenthelocationofalandparcelanditsvalue.Arealestateexpertoncestatedthatthefactorsdete...  相似文献   

11.
Soil respiration is CO2 evolution process from soil to atmosphere, mainly produced by soil micro-organism and plant roots. It is affected not only by biological factors (vegetation, micro-organism, etc.) and environmental factors (temperature, moisture, pH, etc.), but also more and more strongly by man-made factors. Based on literature survey, main factors affecting soil respiration were reviewed. The relationship of soil respiration to latitude and to mean annual temperature were analyzed by using the data measured from forest vegetation in the world. As a result, soil respiration rate decreased exponentially with an increase of latitude, and increased with increasing temperature. Following the relationship between soil respiration and temperature, Q10 value (law of Van Hoff) was obtained as 1.57 in the global scale. This project was supported by National Natural Science Foundation of China to FJY (No. 3940003).  相似文献   

12.
Soil respiration from decomposing aboveground litter is a major component of the terrestrial carbon cycle. However, variations in the contribution of aboveground litter to the total soil respiration for stands of varying ages are poorly understood. To assess soil respiration induced by aboveground litter, treatments of litter and no litter were applied to 5-, 10-, and 20-year-old stands of Populus davidiana Dode in the sandstorm source area of Beijing-Tianjin, China. Optimal nonlinear equations were applied to model the combined effects of soil temperature and soil water content on soil respiration. Results showed that the monthly average contribution of aboveground litter to total soil respiration were 18.46% ± 4.63%, 16.64% ± 9.31%, and 22.37% ± 8.17% for 5-, 10-, and 20-year-old stands, respectively. The relatively high contribution in 5- and 20-year-old stands could be attributed to easily decomposition products and high accumulated litter, respectively. Also, it fluctuated monthly for all stand ages due to substrate availability caused by phenology and environmental factors. Litter removal significantly decreased soil respiration and soil water content for all stand ages (p < 0.05) but not soil temperature (p > 0.05). Variations of soil respiration could be explained by soil temperature at 5-cm depth using an exponential equation and by soil water content at 10-cm depth using a quadratic equation, whereas soil respiration was better modeled using the combined parameters of soil temperature and soil water content than with either soil temperature or soil water content alone. Temperature sensitivity (Q 10) increased with stand age in both the litter and the no litter treatments. Considering the effects of aboveground litter, this study provides insights for predicting future soil carbon fluxes and for accurately assessing soil carbon budgets.  相似文献   

13.
运用数值模拟建立青藏高原兹格塘错流域土壤、植被、气候等的空间和属性数据库;接着,借助分布式流域尺度水文模型(SWAT模型),对兹格塘错1956—2006年间的流量进行模拟实验;最后,反演50年来兹格塘错流域水文过程,测试流域温度、降水和蒸发组合的敏感因子对湖泊水量变化的效应,探讨50年来湖泊水量对气候变化的响应。模拟实验的边界条件设置为自然地形、土壤、植被覆盖,其中土壤资料包括有机质含量、粒径等理化参数。模拟结果表明:兹格塘错的年平均流量为6.3m3/s,流量高峰集中在8月至10月,并且由于融雪补给的关系,3月出现另一个流量高峰;模拟结果与遥感解译所得到的结果吻合较好。敏感实验表明:兹格塘错流域内温度、降水和蒸发组合的敏感因子实验具有高原特征,即高原湖泊的水文过程和湖泊流量变化有着较为敏感的响应关系;兹格塘错流量受降水的影响最大,随着降水的增加,流量有所增加;在温度升高的情况下,流域蒸发量增加速度大,兹格塘错流量增加的效应不明显,而在冷湿模式下,流域蒸发量降低,兹格塘错流量增加显著。  相似文献   

14.
Vegetation cover is the main factor of soil loss prevention. The C-factor of the RUSLE (Revised Universal Soil Loss Equation) was predicted with NDVI, ground data and exponential regression equation for mountain rangelands of Kyrgyzstan. Time series of C-factor, precipitation and temperature were decomposed into seasonal and trend components with STL (seasonal decomposition by loess) to assess their interrelations. C-factor, precipitation and temperature trend components indicated significant lagged correlation, whereas seasonal components indicated more complex relations with climate factors which can be promoting as well as limiting factors for vegetation development, depending on the season. Rainy springs and hot summers may increase soil loss dramatically, whereas warm and dry springs with rainy summers can decrease it. Steep slopes indicated higher soil loss ratio, whereas flat areas were better protected by vegetation.  相似文献   

15.
三北地区是我国重要的生态屏障,分析2000—2019年三北防护林体系建设工程(简称:三北工程)区植被恢复时空变化状况,厘定人类活动与气候要素对植被恢复的贡献,探究植被恢复对土壤风蚀影响,评估植被恢复潜力空间,可为三北防护林体系建设工程未来规划管理和科学施策提供参考。本文在选取植被覆盖度和植被净初级生产力表征植被恢复状况基础上,利用地面数据,结合模型模拟,定量评估了2000—2019年三北防护林体系建设工程区植被恢复程度及其对土壤风蚀的影响,并对植被恢复潜力进行探究。研究结果表明:(1) 2000—2019年植被恢复程度高、较高的面积,占总面积的35.29%和13.16%,主要分布在黄土高原区及北部区域和风沙区与东北华北平原农区的部分地区。人类活动与气候因素对植被恢复贡献率为10.45%和89.55%;(2)土壤风蚀以轻度侵蚀和微度侵蚀为主,呈逐年下降趋势,剧烈侵蚀面积减少了66.45%,防风固沙服务得到进一步提升。植被恢复程度与土壤风蚀模数呈负相关关系,植被恢复程度较好有助于降低土壤风蚀模数;(3)三北工程区森林、草地和荒漠生态系统仍有8.16%的恢复潜力,内蒙古高原北部部分地区、哈顺...  相似文献   

16.
Vegetation restoration has been proposed as an effective method for increasing both plant biomass and soil carbon(C) stocks. In this study, 204 publications(733 observations) were analyzed, focusing on the effects of vegetation restoration on soil organic carbon(SOC) in China. The results showed that SOC was increased by 45.33%, 24.43%, 30.29% and 27.98% at soil depths of 0–20 cm, 20–40 cm, 40–60 cm and 60 cm after vegetation restoration, respectively. Restoration from both cropland and non-cropland increased the SOC content. The conversion of non-cropland was more efficient in SOC accumulation than the conversion of cropland did, especially in 40 cm layers. In addition, the conversion to planted forest led to greater SOC accumulation than that to other land use did. Conversion period and initial SOC content extended more influence on soil C accumulation as the main factors after vegetation restoration than temperature and precipitation did. The SOC content significantly increased with restoration period after long-term vegetation restoration( 40 yr), indicating a large potential for further accumulation of carbon in the soil, which could mitigate climate change in the near future.  相似文献   

17.
Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO2 levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO2 budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest (SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements. Research was conducted over one year in Xishuangbanna during May, June, July and October 2015 (wet season) and January and March 2016 (dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha-1 yr-1 in natural forest and 11.7 and 5.7 Mg C ha-1 yr-1 in rubber plantation. Using a linear mixed effects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.  相似文献   

18.
六盘水市土壤侵蚀时空特征及影响因素分析   总被引:1,自引:0,他引:1  
六盘水市是我国生态地位极其重要,水土流失又较为严重的城市。近些年,六盘水市实施了一系列生态工程,为了定量分析六盘水市土壤侵蚀状况及其影响因素,本文基于RUSLE模型,利用降雨数据、遥感影像数据、土地利用数据等,对贵州省六盘水市1990-2015年土壤侵蚀模数和土壤侵蚀量进行定量模拟,分析其时空动态变化,利用地理探测器定量分析影响因素,并进行空间相关性分析,结果表明: ① 六盘水市土壤侵蚀以微度和中度侵蚀为主。土壤侵蚀严重地区主要分布在北盘江流域与南盘江流域交界处以及喀斯特山地地区,煤矿开采使植被覆盖等抑制土壤侵蚀因子减少作用,使局部地区土壤侵蚀程度加剧。② 1990-2010年平均土壤侵蚀模数整体为下降趋势,2010-2015年为上升趋势。其中2000年平均土壤侵蚀模数最大,2010年平均土壤侵蚀模数最小。该变化由降雨可蚀性因子和植被覆盖度因子综合影响所致。③ 植被覆盖度因子和多年平均降雨量因子是影响区域土壤侵蚀空间分布的重要因素。未利用土地、植被覆盖度小于0.3、坡度在25°以上和降雨量在1543~1593 mm之间的地区为高风险侵蚀区域。④ 植被覆盖度与土壤侵蚀在空间上全部呈负相关性,降雨因子与土壤侵蚀在空间上存在负相关性和正相关性。⑤ 土壤侵蚀改善区域大多分布在生态工程区域内,生态工程建设能够改善土壤侵蚀情况,不同生态工程保护侧重点不同导致土壤侵蚀改善程度不同。退耕还林还草工程对六盘水市土壤侵蚀的改善具有重要意义,六盘水市更宜退耕还林。  相似文献   

19.
Seasonal snow is one of the most important influences on the development and distribution of permafrost and the hydrothermal regime in surface soil. Alpine meadow, which constitutes the main land type in permafrost regions of the Qinghai-Tibet Plateau, was selected to study the influence of seasonal snow on the temperature and moisture in active soil layers under different vegetation coverage. Monitoring sites for soil moisture and temperature were constructed to observe the hydrothermal processes in active soil layers under different vegetation cover with seasonal snow cover variation for three years from 2010 to 2012. Differences in soil temperature and moisture in areas of diverse vegetation coverage with varying levels of snow cover were analyzed using active soil layer water and temperature indices. The results indicated that snow cover greatly influenced the hydrothermal dynamics of the active soil layer in alpine meadows. In the snow manipulation experiment with a snow depth greater than 15 cm, the snow cover postponed both the freeze-fall and thawrise onset times of soil temperature and moisture in alpine LC (lower vegetation coverage) meadows and of soil moisture in alpine HC (higher vegetation coverage) meadows; however, the opposite response occurred for soil temperatures of alpine HC meadows,where the entire melting period was extended by advancing the thaw-rise and delaying the freeze-fall onset time of the soil temperature. Snow cover resulted in a decreased amplitude and rate of variation in soil temperature, for both alpine HC meadows and alpine LC meadows, whereas the distinct influence of snow cover on the amplitude and rate of soil moisture variation occurred at different soil layers with different vegetation coverages. Snow cover increased the soil moisture of alpine grasslands during thawing periods. The results confirmed that the annual hydrothermal dynamics of active layers in permafrost were subject to the synergistic actions of both snow cover and vegetation coverage.  相似文献   

20.
典型地物波谱库的数据体系与波谱模拟   总被引:21,自引:0,他引:21  
本文讨论典型地物波谱知识库的数据体系与地物波谱模拟的相关问题 ,并给出波谱知识库支持的农业定量遥感应用示例。波谱知识库的数据体系强调波谱参数与环境参数的配套 ,波谱数据测量是在相关规范的支持下完成的 ,质量控制贯穿于数据采集的全过程。波谱模拟通过遥感物理模型完成 ,模拟波谱计算包括地表参数的时间、空间扩展与遥感物理模型运算。最后以作物生长模型结合植被组分光谱模型和冠层遥感模型为核心 ,构造了定量遥感的农业示例。  相似文献   

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