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青藏高原植被覆盖对水热条件年内变化的响应及其空间特征 总被引：7，自引：0，他引：7
利用1982-2000年NOAA/AVHRR卫星的NDVI数据(时间分辨率旬,空间分辨率8 km×8 km),结合同时期的气温和降水资料,基于时滞互相关方法和GIS工具,分析了青藏高原植被覆盖对水、热条件年内变化的时滞响应及其空间特征。结果如下:①除高寒荒漠、森林外,青藏高原植被NDVI与同期旬均温和旬降水相关性均呈高度正相关。其中,中等覆盖度的植被受水、热影响表现更为强烈。②青藏高原植被NDVI对气温和降水有滞后效应,且滞后水平存在空间差异,高原北部(柴达木盆地、昆仑山北冀)和高原南部植被对降水、和温度的响应比较迟缓,而高原中、东部地区植被对温度和降水的响应比较敏感。③不同植被类型对水热条件的响应程度也存在差异,由高到低依次是草甸、草原、灌丛、高寒垫状植被、荒漠,最后是森林。 相似文献
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Accurate quantification of aboveground biomass of grasslands in alpine regions plays an important role in accurate quantification of global carbon cycling. The monthly normalized difference vegetation index (NDVI), enhanced vegetation index (EVI), mean air temperature (Ta), ≥5℃ accumulated air temperature (AccT), total precipitation (TP), and the ratio of TP to AccT (TP/AccT) were used to model aboveground biomass (AGB) in grasslands on the Tibetan Plateau. Three stepwise multiple regression methods, including stepwise multiple regression of AGB with NDVI and EVI, stepwise multiple regression of AGB with Ta, AccT, TP and TP/AccT, and stepwise multiple regression of AGB with NDVI, EVI, Ta, AccT, TP and TP/AccT were compared. The mean absolute error (MAE) and root mean squared error (RMSE) values between estimated AGB by the NDVI and measured AGB were 31.05 g m-2 and 44.12 g m-2, and 95.43 g m-2 and 131.58 g m-2 in the meadow and steppe, respectively. The MAE and RMSE values between estimated AGB by the AccT and measured AGB were 33.61g m-2 and 48.04 g m-2 in the steppe, respectively. The MAE and RMSE values between estimated AGB by the vegetation index and climatic data and measured AGB were 28.09 g m-2 and 42.71 g m-2, and 35.86 g m-2 and 47.94 g m-2, in the meadow and steppe, respectively. The study finds that a combination of vegetation index and climatic data can improve the accuracy of estimates of AGB that are arrived at using the vegetation index or climatic data. The accuracy of estimates varied depending on the type of grassland. 相似文献
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An overall greening over the Tibetan Plateau(TP) in recent decades has been established through analyses of remotely sensed Normalized Difference Vegetation Index(NDVI), though the regional pattern of the changes and associated drivers remain to be explored. This study used a satellite Leaf Area Index(LAI) dataset(the GLASS LAI dataset) and examined vegetation changes in humid and arid regions of the TP during 1982–2012. Based on distributions of the major vegetation types, the TP was divided roughly into a humid southeastern region dominated by meadow and a dry northwestern region covered mainly by steppe. It was found that the dividing line between the two regions corresponded well with the lines of mean annual precipitation of 400 mm and the mean LAI of 0.3. LAI=0.3 was subsequently used as a threshold for investigating vegetation type changes at the interanual and decadal time scales: if LAI increased from less than 0.3 to greater than0.3 from one time period to the next, it was regarded as a change from steppe to meadow, and vice versa. The analysis shows that changes in vegetation types occurred primarily around the dividing line of the two regions, with clear growth(reduction) of the area covered by meadow(steppe), in consistency with the findings from using another independent satellite product. Surface air temperature and precipitation(diurnal temperature range) appeared to contribute positively(negatively) to this change though climate variables displayed varying correlation with LAI for different time periods and different regions. 相似文献
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青藏高原植被NDVI对气候因子响应的格兰杰效应分析 总被引：3，自引：1，他引：3
多变的气候和复杂的地理环境使得青藏高原植被对气候变化响应敏感,因此分析高原植被与气候因子之间的动态关系对气候变化研究和生态系统管理具有重要意义。论文基于1982—2012年青藏高原气象数据(气温、降水)以及GIMMS NDVI3g遥感数据,在像素级别上运用格兰杰因果关系检验方法,在月尺度和季节尺度上分析了高原植被NDVI(主要是草原)与平均气温、降水量之间的响应情况及因果关系。研究表明：① 月尺度上NDVI与平均气温之间、NDVI与降水量之间的时序平稳性比例高于季节尺度,月尺度下达到平稳性的植被区域分别占99.13%和98.68%,季节尺度下分别占64.01%和71.97%;② 月尺度下高原平均气温和降水量对NDVI影响的滞后期都集中在第12~13个月,荒漠草原、典型草原和草甸3种植被类型的滞后期一致,季节尺度下平均气温和降水量对NDVI影响的滞后期主要分布在第3~4和第6个季度,3种植被类型的滞后期差异性较大;③ 月尺度下,青藏高原约98.95%的植被覆被区的平均气温是引起NDVI变化的格兰杰原因,反之,大部分地区(约89.05%,除高原东南区域)内NDVI也是引起平均气温变化的格兰杰原因;季节尺度下,青藏高原中部以外植被区域(约92.03%)内的平均气温是引起NDVI变化的格兰杰原因,而在东部和西部部分地区(约50.55%)中NDVI也是引起平均气温变化的格兰杰原因;④ 月尺度下,高原东北和西北地区(约72.05%)内的降水量是引起NDVI变化的格兰杰原因,大部分地区(约94.86%,除东南部少量区域)中NDVI是引起降水量变化的格兰杰原因;季节尺度下,高原东南部(约61.43%)地区内的降水量是引起NDVI变化的格兰杰原因,高原中东部地区(约48.98%)中NDVI是引起降水量变化的格兰杰原因。总之,高原植被NDVI与气温、降水的相互作用显著,彼此均可构成格兰杰因果效应,但总体上气候因子的影响程度大于植被的反馈作用,月尺度的效应区域大于季节尺度的效应区域。 相似文献
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1982~2013年青藏高原高寒草地覆盖变化及与气候之间的关系 总被引：7，自引：2，他引：5
利用GIMMS NDVI数据和地面气象站台观测数据,对青藏高原1982~2013年高寒草地覆盖时空变化及其对气象因素的响应进行研究,结果表明：青藏高原高寒草地生长季NDVI表现为从东南到西北逐渐减少的趋势,近32 a来,整个高原草地生长季NDVI呈上升趋势,增加速率为0.000 3/a (p<0.05);高寒草地生长季NDVI年际变化具有空间异质性,整体为增加趋势,呈增加趋势的面积约占研究区域面积的75.3%,其中显著增加的占26.0% （p<0.05）,类型主要为分布在青藏高原东北部地区的高寒草甸;比例为4.7%,草地类型主要为高寒草原,主要分布在高原西部地区;基于生态地理分区的分析显示,青藏高原草地与降水、温度的相关关系具有明显的空间差异,高寒草地生长季NDVI均值与降水呈显著正相关,对降水的滞后效应显著;高原东北部温度较高,热量条件较好,降水为高寒草地生长季NDVI变化的主导因子;东中部地区降水充沛,温度则为高寒草地生长的制约因子;南部地区降水和温度都较适宜,均与高寒草地生长季NDVI相关性显著(p< 0.05),共同作用于草地的生长;中部和西部地区,气候因子与高寒草地生长季NDVI关系均不显著。 相似文献
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高寒草甸土壤有机碳储量及其垂直分布特征 总被引：24，自引：0，他引：24
青藏高原是全球变化的敏感区。高寒草甸草原是青藏高原上最主要的放牧利用草地资源之一。选择青藏高原东北隅海北站内具有代表性的高寒草甸土壤进行高分辨率采样,测定土壤根系和有机碳含量。研究得出,青藏高原高寒草甸土壤贮存有巨大的根系生物量 (23544.60 kg ha-1~27947 kg ha-1) 和土壤有机碳 (21.52 GtC);自然土壤表层 (0~10 cm) 储存了整个剖面土壤有机碳总量的30%左右。比较发现,高寒草甸土壤的有机碳平均贮存量 (23.17×104 kgCha-1) (0~60 cm) 较相应深度的热带森林土壤、灌丛土壤和草地土壤的有机碳贮存量高约1~5倍多。在全球碳预算研究中,青藏高原高寒草甸土壤有机碳库不可忽视。随着全球变暖,表层土壤有机碳分解释放的CO2将增加。为了减少高寒草甸生态系统的碳排放,应加强高寒草甸土壤地表覆被的保护,合理种植深根系植物。这对减缓全球大气CO2浓度升高的速率以及可持续开发高寒草甸的生态服务功能都具有重要意义。 相似文献
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高寒草甸是广布于青藏高原的主要植被类型,它是青藏高原大气与地面之间生物地球化学循环的重要构成部分,在区域碳平衡中起着极为重要的作用。基于对青藏高原主要高寒草甸生态系统类型CO2通量研究方面的综述,系统分析了高寒草甸生态系统CO2通量日、季、年等不同时间尺度的变化特征以及温度、光合有效辐射、降水等主要环境因子对高寒草甸生态系统CO2通量的影响;同时,结合其他地区草地生态系统,就青藏高原三种典型高寒草甸生态系统类型源汇效应和Q10值进行了比较;最后,结合青藏高原高寒草甸生态系统CO2通量研究的现实与需要,提出了当前存在一些不确定性和有待深入研究的问题。 相似文献
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The temporal and spatial changes of NDVI on the Tibetan Plateau, as well as the relationship between NDVI and precipitation, were discussed in this paper, by using 8-km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 1999. Monthly maximum NDVI and monthly rainfall were used to analyze the seasonal changes, and annual maximum NDVI, annual effective precipitation and growing season precipitation (from April to August) were used to discuss the interannual changes. The dynamic change of NDVI and the corre-lation coefficients between NDVI and rainfall were computed for each pixel. The results are as follows: (1) The NDVI reached the peak in growing season (from July to September) on the Tibetan Plateau. In the northern and western parts of the plateau, the growing season was very short (about two or three months); but in the southern, vegetation grew almost all the year round. The correlation of monthly maximum NDVI and monthly rainfall varied in different areas. It was weak in the western, northern and southern parts, but strong in the central and eastern parts. (2) The spatial distribution of NDVI interannual dynamic change was different too. The increase areas were mainly distributed in southern Tibet montane shrub-steppe zone, western part of western Sichuan-eastern Tibet montane coniferous forest zone, western part of northern slopes of Kunlun montane desert zone and southeastern part of southern slopes of Himalaya montane evergreen broad-leaved forest zone; the decrease areas were mainly distributed in the Qaidam montane desert zone, the western and northern parts of eastern Qinghai-Qilian montane steppe zone, southern Qinghai high cold meadow steppe zone and Ngari montane desert-steppe and desert zone. The spatial distribution of correlation coeffi-cient between annual effective rainfall and annual maximum NDVI was similar to the growing season rainfall and annual maximum NDVI, and there was good relationship between NDVI and rainfall in the meadow and grassland with medium vegetation cover, and the effect of rainfall on vegetation was small in the forest and desert area. 相似文献
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青藏高原植被覆盖变化与降水关系 总被引：15，自引：6，他引：9
The temporal and spatial changes of NDVI on the Tibetan Plateau, as well as the relationship between NDVI and precipitation, were discussed in this paper, by using 8-km resolution multi-temporal NOAA AVHRR-NDVI data from 1982 to 1999. Monthly maximum NDVI and monthly rainfall were used to analyze the seasonal changes, and annual maximum NDVI, annual effective precipitation and growing season precipitation (from April to August) were used to discuss the interannual changes. The dynamic change of NDVI and the corre- lation coefficients between NDVI and rainfall were computed for each pixel. The results are as follows: (1) The NDVI reached the peak in growing season (from July to September) on the Tibetan Plateau. In the northern and western parts of the plateau, the growing season was very short (about two or three months); but in the southern, vegetation grew almost all the year round. The correlation of monthly maximum NDVI and monthly rainfall varied in different areas. It was weak in the western, northern and southern parts, but strong in the central and eastern parts. (2) The spatial distribution of NDVI interannual dynamic change was different too. The increase areas were mainly distributed in southern Tibet montane shrub-steppe zone, western part of western Sichuan-eastern Tibet montane coniferous forest zone, western part of northern slopes of Kunlun montane desert zone and southeastern part of southern slopes of Himalaya montane evergreen broad-leaved forest zone; the decrease areas were mainly distributed in the Qaidam montane desert zone, the western and northern parts of eastern Qinghai-Qilian montane steppe zone, southern Qinghai high cold meadow steppe zone and Ngari montane desert-steppe and desert zone. The spatial distribution of correlation coeffi- cient between annual effective rainfall and annual maximum NDVI was similar to the growing season rainfall and annual maximum NDVI, and there was good relationship between NDVI and rainfall in the meadow and grassland with medium vegetation cover, and the effect of rainfall on vegetation was small in the forest and desert area. 相似文献
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On the Tibetan Plateau, the alpine meadow is the most widespread vegetation type. The alpine meadow has a low biological productivity and low vegetation coverage in the growing season. The daytime NEE between the atmosphere and the alpine meadow ecosystem was influenced by solar radiation. To analyze the characteristics of change in NEE and to calculate the parameters related to photosynthesis and respiration in different solar radiation environments, the NEE measurements were taken in Damxung from July to August in 2003, 2004, 2005 and 2006 using the eddy covariance technique. Solar radiation was grouped into three levels according to the net radiation, which was more than 155 W m-2 d-1 on clear days, 144±5 W m-2 d-1 on partly cloudy days and less than 134 W m-2 d-1 on cloudy days. The diurnal relationships between NEE and PAR varied with differences in solar radiation, which was a rectangular hyperbola form on clear days, two different concave curves on partly cloudy days and an irregular triangle form on cloudy days. The mean CO2 absorption rate showed a decreasing trend with increasing solar radiation. The daytime absorption maximum occurred around 10:00 on clear days with an average of slightly less –0.2 mg m-2 d-1, around 11:00 on partly cloudy days with an average of about –0.2 mg m-2 d-1, and around 12:00 on cloudy days with an average of about –0.25 mg m-2 d-1. As solar radiation increased, the Amax and the Q10 decreased. However, the R10 increased and the maximum of the α occurred on partly cloudy days. The optimum net solar radiation was about 134–155 W m-2 d-1, which induced a PAR of about 1800-2000 μmol m-2 s-1 and soil temperature at a depth of 5 cm of about 14℃. Therefore, on the Tibetan Plateau, the alpine meadow ecosystem will have a higher carbon absorption potential while solar radiation decreases in the future. 相似文献
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基于植被盖度和高度的不同退化程度高寒草地地上生物量估算 总被引：1，自引：0，他引：1
由于气候变化和不合理的人类活动，20世纪80年代以来青藏高原高寒草地发生严重退化。地上生物量是评价草地退化的直观指标。通常采用植被盖度和高度来估算草地地上生物量，但草地退化后，植被盖度和高度与地上生物量之间的关系是否会发生变化目前还不清楚，这影响着退化草地生物量估算的精度。通过多元回归分析研究了青藏高原中部和东北部高寒草甸、高寒草原在不同退化程度下植被盖度和高度与地上生物量的关系。结果表明：（1）高寒草甸与高寒草原地上生物量整体上及不同退化阶段都没有显著差异（P>0.05）。（2）随着退化程度的加剧植被盖度和高度对地上生物量的影响也发生改变，体现在未退化阶段地上生物量主要受植被高度影响，退化后主要受植被盖度影响。（3）无论是高寒草甸还是高寒草原分退化程度的回归模型估算结果都较不分退化程度模型估算的生物量更接近实测值。我们建议在退化高寒草地研究中采用盖度和高度估算生物量时，根据退化阶段采用不同的估算模型。 相似文献
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Pollen-based reconstructions of Holocene vegetation and climatic change of Tibetan Plateau 
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下载免费PDF全文 A synthesis of Holocene pollen records from the Tibetan Plateau shows the history of vegetation and climatic changes during the Holocene. Palynological evidences from 24 cores/sections have been compiled and show that the vegetation shifted from subalpine/alpine conifer forest to subalpine/alpine evergreen sclerophyllous forest in the southeastern part of the plateau; from alpine steppe to alpine desert in the central, western and northern part; and from alpine meadow to alpine steppe in the eastern and southern plateau regions during the Holocene. These records show that increases in precipitation began about 9 ka from the southeast, and a wide ranging level of increased humidity developed over the entire of the plateau around 8-7 ka, followed by aridity from 6 ka and a continuous drying over the plateau after 4-3 ka. The changes in Holocene climates of the plateau can be interpreted qualitatively as a response to orbital forcing and its secondary effects on the Indian Monsoon which expanded northwards 相似文献
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The nutritional quality of grasslands is closely related to recruitment of young and population dynamics of livestock and wild herbivores. However, the response of nutritional quality to climate warming has not been fully understood in the alpine meadow on the Tibetan Plateau, especially in the Northern Tibet. Here, we investigated the effect of experimental warming ( beginning in 2008) on nutritional quality in three alpine meadows (site A: 4313 m, B: 4513 m and C: 4693 m) in the Northern Tibet. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude ash (Ash), ether extract (EE) and water-soluble carbohydrate (WSC) were examined in 2018-2019. Experimental warming only increased the content of CP by 27.25%, ADF by 89.93% and NDF by 41.20%, but it decreased the content of Ash by 57.76% in 2019 at site B. The contents of CP and WSC both increased with soil moisture (SM). The content of CP decreased with vapor pressure deficit (VPD). The combined effect of SM and VPD was greater than air temperature (Ta) in controlling the variations of the CP content, ADF content and nutritional quality. Compared to Ta, VPD explained more of the variation in NDF and Ash content. All of these findings suggest that warming effects on nutritional quality may vary with site and year, and water availability may have a stronger effect on the nutritional quality than temperature in the alpine meadow of the Northern Tibet. 相似文献
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为分析不同高寒植物群落优势种的光合特性，探究影响光合作用的主要环境因子，选择若尔盖高原同纬度同海拔的沼泽湿地、湿草甸和干草甸样地，对比研究典型植物群落优势种木里苔草（Carex muliensis）、四川嵩草（Kobresia setchwanensis）和垂穗披碱草（Elymus nutans）光合日变化。结果表明：（1）由于水分条件差异显著（P<0.05），沼泽湿地优势种木里苔草的净光合速率（Pn）日变化呈单峰趋势，而湿草甸和干草甸优势种Pn则为双峰曲线，存在光合“午休”现象。（2）水分利用效率（WUE）日均值表现为干草甸优势种 > 湿草甸优势种 > 沼泽湿地优势种；各群落优势种光能利用效率（LUE）日均值无显著差异。（3）沼泽湿地优势种Pn主要受光合有效辐射（PAR）、气温（Ta）和空气相对湿度（RH）的影响；干草甸Ta和PAR为主要环境因子，湿草甸影响优势种Pn的主导因素为PAR。 相似文献
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Evapotranspiration is the key driving factor of the earth’s water cycle, and an important component of surface water and energy balances. Therefore, it also reflects the geothermal regulation function of ecohydrological process. The Qinghai-Tibet Plateau is the birthplace of important rivers such as the Yangtze River and the Yellow River. The regional water balance is of great significance to regional ecological security. In this study, ARTS, a dual- source remote sensing evapotranspiration model developed on a global scale, is used to evaluate the actual evapotranspiration (ET) in the Qinghai-Tibet Plateau from 1982 to 2014, using meteorological data interpolated from observations, as well as FPAR and LAI data obtained by satellite remote sensing. The characteristics of seasonal. interannual and dynamic changes of evapotranspiration were analyzed. The rates at which meteorological factors contribute to evapotranspiration are calculated by sensitivity analysis and multiple linear regression analysis, and the dominant factors affecting the change of evapotranspiration in the Qinghai-Tibet Plateau are discussed. The results show that: (1) The estimated values can explain more than 80% of the seasonal variation of the observed values (R2 = 0.80, P < 0.001), which indicates that the model has a high accuracy. (2) The evapotranspiration in the whole year, spring, summer and autumn show significant increasing trends in the past 30 years, but have significant regional differences. Whether in the whole year or in summer, the southern Tibetan Valley shows a significant decreasing trend (more than 20 mm per 10 years), while the Ali, Lhasa Valley and Haibei areas show increasing trends (more than 10 mm per 10 years). (3) Sensitivity analysis and multiple linear regression analysis show that the main factor driving the interannual change trend is climate warming, followed by the non-significant increase of precipitation. However, vegetation change also has a considerable impact, and together with climate factors, it can explain 56% of the interannual variation of evapotranspiration (multiple linear regression equation R2 = 0.56, P < 0.001). The mean annual evapotranspiration of low-cover grassland was 26.9% of high-cover grassland and 21.1% of medium-cover grassland, respectively. Considering significant warming and insignificant wetting in the Qinghai-Tibet Plateau, the increase of surface evapotranspiration will threaten the regional ecological security at the cost of glacial melting water. Effectively protecting the ecological security and maintaining the sustainable development of regional society are difficult and huge challenges. 相似文献
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黄河源区高寒草地土壤有机碳储量及分布特征 总被引：14，自引：0，他引：14
选择位于黄河源区的青海省果洛藏族自治州为研究区,利用第二次全国土壤普查所得的土壤剖面数据以及55个典型土壤剖面的地理位置、土层深度、有机质含量、面积、理化分析数据和1:50万数字化土壤类型图,在GIS的支持下利用土壤类型法对黄河源区草地土壤碳库进行了估算。结果表明,黄河源区土壤碳密度较高,平均土壤有机碳密度为29.97 kg/m2,高寒草地土壤有机碳库主要由高山草甸土和高山草原土的有机碳库构成,研究区土壤有机碳总储量达15×108tC。区域草地土壤有机碳密度及储量呈明显的水平和垂直分异规律。 相似文献