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1.
青藏高原植被变化特征及其对气候变化的影响 总被引：2，自引：0，他引：2
利用1982-2001年美国国家航天航空局(NASA)的归一化植被指数(NDVI)资料以及55个青藏高原地区气象台站实测的最高气温、最低气温、平均气温和降水资料,初步分析了青藏高原地区各季节植被变化特征及其对气候变化的影响,通过分析发现,各季节青藏高原地区NDVI均以增长为主.特别是高原南部、北部和西部等地区增加明显,高原中东部地区植被有所减少.通过相关分析和台站概率相关分析发现,高原冬季和春季NDVI与后期春季和夏季的最高气温、最低气温、平均气温和降水有较好的正相关关系,但有的表现在相关系数比较显著,有的表现为概率相关较明显. 相似文献
2.
《中国海洋大学学报(英文版)》2020,19(4)
Facilitated by the high-throughput sequencing(HTS) technique, the importance of protists to aquatic systems has been widely acknowledged in the last decade. However, information of protistan biotic interactions and seasonal dynamics is much less known in the coast ecosystem with intensive anthropic disturbance. In this study, year-round changes of protist community composition and diversity in the coastal water of Yantai, a city along the northern Yellow Sea in China, were investigated using HTS for the V4 region of 18 S rDNA. The interactions among protist groups were also analyzed using the co-occurrence network. Data analyses showed that Alveolata, Chlorophyta, and Stramenopiles are the most dominant phytoplanktonic protists in the investigated coastal area. The community composition displayed strong seasonal variation. The abundant families Dino-Group-I-Clade-1 and Ulotrichales_X had higher proportions in spring and summer, while Bathycoccaceae exhibited higher ratios in autumn and winter. Alpha diversities(Shannon and Simpson) were the highest in autumn and the lowest in spring(ANOVA test, P 0.05). Nutrients(SiO_4~(2-), PO_4~(3-)), total organic carbon(TOC), and pH seemed to drive the variation of alpha diversity, while temperature, PO_4~(3-) and TON were the most significant factors influencing the whole protist community. Co-variance network analyses reveal frequent co-occurrence events among ciliates, chlorophytes and dinoflagellate, suggesting biotic interactions have been induced by predation, parasitism and mixotrophy. 相似文献
3.
The distinctive estuary hydrodynamics and nutrient input make the estuary ecosystem play a key role in lake ecosystems. The Nanfei River and Zhaohe River are two main inlets of Chaohu Lake, Anhui, East China. We selected estuaries of the two rivers as representative areas to study temporal and spatial changes of bacterial communities. In August (summer) and November (autumn) 2016 and February (winter) and May (spring) 2017, 16 water and sediment samples were collected from the estuaries. Physicochemical characteristics indicate significant differences in the nutritional status and eutrophication index of the estuaries due mainly to organic input. Examination of the number of operational taxonomic units, the diversity index, the community composition, and redundancy analysis revealed the following. First, the existence of varying degrees of seasonal differences in the distribution of almost all bacteria. In addition, the species diversity in the sediment samples was higher than that in the water samples, and the dominant species differed also among these samples. Second, a large number of unknown genera were detected, especially in the sediment samples, such as unclassified Xanthomonadales incertae sedis, unclassified Anaerolineaceae, and unclassified Alcaligenaceae. Last, TP, TN, and TOC were the main influential factors that affected the bacterial community structure. 相似文献
4.
Tan-guang Gao Shi-chang Kang Ting-jun Zhang Da-qing Yang Jian-guo Shang Xiang Qin 《山地科学学报》2017,14(12):2458-2470
Stream temperatures are sensitive to climate change and runoff regime variations. A comprehensive understanding on the effects of glacial melting on the stream temperatures are important in the Tibetan Plateau, of which contains the largest ice volume outside Polar Regions. This study documented the high-resolution stream temperature thermal regimes from glacier-fed and non-glacial rivers at four sites, versus a high-resolution glacier mass balance monitoring at Zhadang glacier, during summer melt seasons from 2007-2009 in the Nam Co basin of southern Tibetan Plateau. The results showed mean summer stream temperature and magnitude of daily thermal variation were lower at all sites when compared with alpine glacierized environments at lower latitudes. Mean stream temperatures for glacier-fed rivers(4.0℃ to 6.5℃)were minimum and least variable near the glacier terminus with increasing toward downstream(+0.13℃ km~(–1) to +0.28℃ km~(–1)). Meanwhile, stream temperature in 2008 was similar to that in 2007 and2009. For the non-glacial rivers, mean stream temperatures was about 9.0℃ with significantly warmer in summer months in 2009 and 2007 than that in 2008. These differences indicated that stream temperature was strongly influenced by discharge and precipitation. Particularly, the glacier mass balance played a large role on the stream temperature directly when the glacier melt contributed more than 50% of the glacial river runoff. Our results demonstrated the stream thermal variability from southern Tibetan rivers and provided new insight into the influence of glacier mass balance on stream thermal variability in high-altitude river system. 相似文献
5.
Changes in the thermal and hydraulic regime within the active layer in the Qinghai-Tibet Plateau 总被引：1，自引：1，他引：0
The change trends of air temperature,precipitation and evaporation from 1999 to 2008 shows that the climate in the Qinghai-Tibet Plateau permafrost region had become warmer.The analysis of the systematic active-layer data monitoring network along the Qinghai-Tibet Highway indicated that the active-layer thickness had been increasing and the soil temperature was rising.The soil temperature was rising in winter but not at the end of spring or during the entire summer.With thickening and warming of the active layer,the liquid water content of the active layer had an obvious downward migration and liquid water content in the top horizons decreased,but in the deeper horizons it increased. 相似文献
6.
Jun-ren Xian Guo-peng Chen Yin-zhan Liu Xiao-xun Xu Zhan-biao Yang Wan-qin Yang 《山地科学学报》2017,14(2):346-355
Understanding of treeline ecotone ecophysiological adaptation to climate warming is still very limited. Furthermore, it is difficult to predict which plant species could dominate in the future. For this reason, a study was conducted in the treeline ecotone, East Tibetan Plateau to detcct the adaptation of the dwarf willow (Salix eriostachya) to experimental warming. Compared to ambient conditions, the experimental warming advanced the bud break by 12 days, delayed the leaf abscission by 20 days, and prolonged the growing period by 28 days. It also increased photosynthesis (47%), number of leaves (333%), leaf area (310%), and carbon sequestration of the dwarf willow. Experimental warming did not affect carbon use efficiency, but decreased water use efficiency significantly. Experimental warming enhanced the clonal ramets of Salix eriostachya (+ 3.7 shrubs m-2). The frequent air temperature fluctuations had minor effect on Salix eriostachya. Based on these findings, we highlighted that Salix eriostachya could dominate in the community treeline ecotone of east Tibetan Plateau in the future climate warming scenario. 相似文献
7.
Investigation of dissolved organic carbon (DOC) and particulate organic carbon (POC) at 12 stations in Yantal Sishili Bay in May, August, and November of 1997 and March and May of 1998 showed that DOC concentrations varied from 1.14 mg/L to 5.35 mg/L; that the average values at all staticrLs ineach entise varied from 1.52 mg/L to 2.12 mg/L; that POC concentrafions varied from 0.049 mg/L to 1.411mg/L; and averaged 0.159 mg/L to 0.631 mg/L in each cruise. Horizontal distribution of DOC was influ-enced by factors such as continental input, organism activity, temperature, aquieulture environment, etc. The higher POC concentration occurred along the coast. The vertical distribution of DOC and POC changed obviously in spring and summer, but not obviously in autumn and winter. DOC concentration was highest in summer and POC in spring; both were lowest in winter. The seasonal change of DOC was con-sistent with primary productivity seasonal variation, and that of POC was consistent with ehlorophyll-a sea-sanal variation. The seasonal change trend of the C/N ratio of dissolved organic matter was obvious, but the C/N ratio of particulate organic matter had no such trend. 相似文献
8.
Numerical Study of Water and Suspended Matter Exchange Between the Yellow Sea and the East China Sea 总被引：3，自引：1，他引：2
INTRODUCTIONTheYellowSeaandtheEastChinaSea (ECS)aremarginalseasofthenorthwestPacificandhaveexpansivecontinentalshelves .TheuniqueandstrikingfeaturesoftheYellowSeaandtheECSarethattheyhavestrongtidalcurrent;aresubjecttostrongmonsooninfluence ;andreceiveinflowfromthebiggestriverinChina ,theChangjiangRiver ;andthatthefamouswesternboundarycurrent,theKuroshio ,passesthroughtheECS ,withitsbranchesintrudingupwardintothecontinentalshelfareas.Generallyspeaking ,thewaterexchangecapacityofthe… 相似文献
9.
《山地科学学报》2017,(2)
Understanding of treeline ecotone ecophysiological adaptation to climate warming is still very limited. Furthermore, it is difficult to predict which plant species could dominate in the future. For this reason, a study was conducted in the treeline ecotone, East Tibetan Plateau to detect the adaptation of the dwarf willow(Salix eriostachya) to experimental warming. Compared to ambient conditions, the experimental warming advanced the bud break by 12 days, delayed the leaf abscission by20 days, and prolonged the growing period by 28 days.It also increased photosynthesis(47%), number of leaves(333%), leaf area(310%), and carbon sequestration of the dwarf willow. Experimental warming did not affect carbon use efficiency, but decreased water use efficiency significantly.Experimental warming enhanced the clonal ramets of Salix eriostachya(+ 3.7 shrubs m-2). The frequent air temperature fluctuations had minor effect on Salix eriostachya. Based on these findings, we highlighted that Salix eriostachya could dominate in the community treeline ecotone of east Tibetan Plateau in the future climate warming scenario. 相似文献
10.
《中国海洋湖沼学报》2017,(4)
Coastal wetlands play an important role in the global carbon cycle.Large quantities of sediment deposited in the Changjiang(Yangtze) estuary by the Changjiang River promote the propagation of coastal wetlands,the expansion of saltmarsh vegetation,and carbon sequestration.In this study,using the Chongming Dongtan Wetland in the Changjiang estuary as the study area,the spatial and temporal distribution of soil organic carbon(SOC) stocks and the influences of sedimentation and vegetation on the SOC stocks of the coastal wetland were examined in 2013.There was sediment accretion in the northern and middle areas of the wetland and in the Phragmites australis marsh in the southern area,and sediment erosion in the Scirpus mariqueter marsh and the bare mudflat in the southern area.More SOC accumulated in sediments of the vegetated marsh than in the bare mudflat.The total organic carbon(TOC) stocks increased in the above-ground biomass from spring to autumn and decreased in winter;in the below-ground biomass,they gradually increased from spring to winter.The TOC stocks were higher in the below-ground biomass than in the above-ground biomass in the P.australis and Spartina altemiflora marshes,but were lower in the below-ground biomass in S.mariqueter marsh.Stocks of SOC showed temporal variation and increased gradually in all transects from spring to winter.The SOC stocks tended to decrease from the high marsh down to the bare mudflat along the three transects in the order:P.australis marsh S.alterniflora marsh S.mariqueter marsh bare mudflat.The SOC stocks of the same vegetation type were higher in the northern and middle transects than in the southern transect.These results suggest that interactions between sedimentation and vegetation regulate the SOC stocks in the coastal wetland in the Changjiang estuary. 相似文献
11.
According to palaeoclimatic and modern instrumental data, numerous studies have indicated that the Arctic climate has undergone a significant warming during the past 100 years, and this may lead to significant impact on the fragile lake ecosystem. In this study, we collected a lake sediment core from the Ny-(A)lesund of Svalbard and determined the concentrations of four pigments including chlorophyll derivatives, total carotenoids, oscillaxanthin and myxoxanthophyll in the sediments. Combined with other physical and chemical proxies such as calcium carbonate, total organic carbon, biogenic silicon etc., we have reconstructed the historical changes of lacustrine primary productivity in Ny-(A)lesund, especially for the past 100 years. The results showed that during the period of Little Ice Age (LIA), the climate was unfavorable for the growth of the lake algae, and thus the lacustrine productivity declined. This result was supported by the relatively low contents of pigment and biogenic silica in the sediments. In contrast, the contents of total organic carbon (TOC) and sediment pigments increased significantly in the upper 5 cm (~1890AD), reflecting the rapid growth of the lake algae, thus the great increase of lacustrine primary productivity, corresponding to the warming climate after LIA. However, the biogenic silica in the upper sediments still had a relatively low level, and this might be related to the growth competition with other algae species. Over the past 100 years, the ratio of Osc/Myx in the sediments decreased continuously, indicative of durative increase of myxoxanthophyll in blue-green algal pigments, and this might imply that the human activity had enhanced the nutrition level of the lake in the Arctic region. 相似文献
12.
青藏高原冬季降水的气候特征认识对高原冬季雪灾的防御有着重要意义。基于青藏高原54个气象站1971~2010年冬季(12~2月)逐月降水量资料,利用现代统计方法分析了青藏高原冬季降水的时空分布特征及突变现象,利用经验正交函数(EOF)和旋转经验正交函数(REOF)概括出高原冬季降水的6种主要空间分布型以及区域性特征进行分析。结果表明:冬季降水分布不均匀,偏东偏南部降水量相对较多,冬季降水在12月最少,2月最多;EOF对青藏高原地区冬季降水分解为6种模态,全区一致型、南北部型、东西部型、川西型、高原腹地型和西部型模态;EOF第1模态时间系数表明高原大部分地区冬季降水在20世纪90年代有显著增加、且存在14年左右的周期变化特征。REOF分析表明,高原地区冬季降水的局地特征显著,而高原腹地与中东部地区变化特征显示了高原冬季降水的主要变化特征,与EOF分析第1模态的变化特征较为一致。 相似文献
13.
14.
利用1982年1月-2001年12月青藏高原植被归一化指数(NDVI)和NCEP/NCAR再分析月平均资料,应用相关分析、奇异值分解(SVD)和经验正交分解(EOF)的方法,分析了青藏高原冬季的NDVI变化与南亚夏季风的关系.通过分析表明,高原植被与南亚地区850hPa纬向风场和纬向风垂直切变(U850hPa-U200hPa)有比较好的正相关关系.用纬向风垂直切变EOF分析的第一特征向量对应的时间系数定义一个南亚夏季风指数(EOFI),该系数与高原冬季NDVI相关较好,而且能较好地反映南亚夏季风的变化. 相似文献
15.
A three-dimensional ecosystem model, using a PIC (Particle-In-Cell) method, is developed to reproduce the annual cycle and seasonal variation of nutrients and phytoplankton biomass in Laizhou Bay. Eight state variables, i.e., DIN (dissolved inorganic nitrogen), phosphate, DON (dissolved organic nitrogen), DOP (dissolved organic phosphorus), COD (chemical oxygen demand), chlorophyll-a (Chl-a), detritus and the zooplankton biomass, are included in the model. The model successfully reproduces the observed temporal and spatial variations of nutrients and Chl-a biomass distributions in the bay. The nutrient concentrations are at high level in winter and at low level in summer. Double-peak structure of the phytoplankton (PPT) biomass exists in Laizhou Bay, corresponding to a spring and an autumn bloom respectively. Several numerical experiments are carried out to examine the nutrient limitation, and the importance of the discharges of the Yellow River and Xiaoqinghe River. Both DIN limitation and phosphate limitation exist in some areas of the bay, with the former being more significant than the latter. The Yellow River and Xiaoqinghe River are the main pollution sources of nutrients in Laizhou Bay. During the flood season, the algal growth is inhibited in the bay with the Yellow River discharges being excluded in the experiment, while in spring, the algal growth is enhanced with the Xiaoqinghe River excluded. 相似文献
16.
Soil carbon stock and flux in plantation forest and grassland ecosystems in Loess Plateau,China 总被引：1，自引：1，他引：0
Carbon sequestration occurs when cultivated soils are re-vegetated. In the hilly area of the Loess Plateau, China, black locust(Robinia pseudoacacia) plantation forest and grassland were the two main vegetation types used to mitigate soil and water loss after cultivation abandonment. The purpose of this study was to compare the soil carbon stock and flux of these two types of vegetation which restored for 25 years. The experiment was conducted in Yangjuangou catchment in Yan′an City, Shaanxi Province, China. Two adjacent slopes were chosen for this study. Six sample sites were spaced every 35–45 m from summit to toe slope along the hill slope, and each sample site contained three sampling plots. Soil organic carbon and related physicochemical properties in the surface soil layer(0–10 cm and 10–20 cm) were measured based on soil sampling and laboratory analysis, and the soil carbon dioxide(CO2) emissions and environmental factors were measured in the same sample sites simultaneously. Results indicated that in general, a higher soil carbon stock was found in the black locust plantation forest than that in grassland throughout the hill slope. Meanwhile, significant differences in the soil carbon stock were observed between these two vegetation types in the upper slope at soil depth 0–10 cm and lower slope at soil depth 10–20 cm. The average daily values of the soil CO2 emissions were 1.27 μmol/(m2·s) and 1.39 μmol/(m2·s) for forest and grassland, respectively. The soil carbon flux in forest covered areas was higher in spring and less variation was detected between different seasons, while the highest carbon flux was found in grassland in summer, which was about three times higher than that in autumn and spring. From the carbon sequestration point of view, black locust plantation forest on hill slopes might be better than grassland because of a higher soil carbon stock and lower carbon flux. 相似文献
17.
Warming trend in northern East China Sea in recent four decades 总被引：2，自引：0，他引：2
Global warming has become a notable trend especially since an abrupt climate change in 1976. Response of the East China Sea (ECS) to the global warming trend, however, is not well understood because of sparse long-term observation. In this paper, hydrographic observation data of 1957–1996 are collected and reviewed to study climatological variability in northern ECS. Significant warming trends are found in both summer and winter. In summer, the average SST is about 0.46°C higher during the period of 1977-19... 相似文献
18.
By using Season-reliant Empirical Orthogonal Function (S-EOF) analysis, three dominant modes of the spatial-temporal evolution of the drought/flood patterns in the rainy season over the east of China are revealed for the period of 1960-2004. The first two leading modes occur during the turnabout phase of El Nino-Southern Oscillation (ENSO) decaying year, but the drought/flood patterns in the rainy season over the east of China are different due to the role of the Indian Ocean (IO). The first leading mode appears closely correlated with the ENSO events. In the decaying year of El Nino, the associated western North Pacific (WNP) anticyclone located over the Philippine Sea persists from the previous winter to the next early summer, transports warm and moist air toward the southern Yangtze River in China, and leads to wet conditions over this entire region. Therefore, the precipitation anomaly in summer exhibits a ’Southern Flood and Northern Drought’ pattern over East China. On the other hand, the basin-wide Indian Ocean sea surface temperature anomaly (SSTA) plays a crucial role in prolonging the impact of ENSO on the second mode during the ENSO decaying summer. The Indian Ocean basin mode (IOBM) warming persists through summer and unleashes its influence, which forces a Matsuno-Gill pattern in the upper troposphere. Over the subtropical western North Pacific, an anomalous anticyclone forms in the lower troposphere. The southerlies on the northwest flank of this anticyclone increase the moisture transport onto central China, leading to abundant rainfall over the middle and lower reaches of the Yangtze River and Huaihe River valleys. The anomalous anticyclone causes dry conditions over South China and the South China Sea (SCS). The precipitation anomaly in summer exhibits a ’Northern Flood and Southern Drought’ pattern over East China. Therefore, besides the ENSO event the IOBM is an important factor to influence the drought/flood patterns in the rainy season over the east of China. The third mode is positively correlated with the tropical SSTA in the Indian Ocean from the spring of preceding year(-1) to the winter of following year(+1), but not related to the ENSO events. The positive SSTA in the South China Sea and the Philippine Sea persists from spring to autumn, leading to weak north-south and land-sea thermal contrasts, which may weaken the intensity of the East Asia summer monsoon. The weakened rainfall over the northern Indian monsoon region may link to the third spatial mode through the ’Silk Road’ teleconnection or a part of circumglobal teleconnection (CGT). The physical mechanisms that reveal these linkages remain elusive and invite further investigation. 相似文献
19.
Ruxi River is a tributary of the Three Gorges Reservoir. This study examined the temporal and spatial dynamics in particle size characteristics and the associated nutrients and contaminants of the fluvial suspended and deposited sediments along the Ruxi River. Temporal variations in the particle size distribution of the suspended sediment are controlled mainly by differences in sediment source during different seasons. Total organic carbon(TOC), total nitrogen(TN) and total phosphorous(TP) in the 62μm fraction of the suspended sediment exhibit considerably higher concentrations in spring,indicating high probability of algal blooms in the backwater areas. Downstream trends in the nutrient contents of 62 μm deposited sediments imply the greatest potential for eutrophication in the backwater ends, where highest nutrient concentrations were detected. Assessment of metal contamination shows that the sediments deposited in the water-level fluctuation zone were moderately to strongly contaminated by Cadmium(Cd), with a considerably high potential ecological risk. The findings reported have emphasized the impacts of reservoir impoundment on aquatic and/or terrestrial environment in this region. More information on physical, chemical and biological processes of sediment and sediment-associated materials are needed for developing environmentally and ecologically sound policies of water and sediment management. 相似文献
20.
Antarctic sea-ice oscillation index with a seesaw pattern is defined using NCEP/NCAR reanalysis girds data of monthly Antarctica sea-ice concentration from 1979 to 2002. The relationships between the index of winter and the summer precipitations in China as well as the onset date of the summer East Asia monsoon are presented. The study result shows that the grids of correlation coefficients passed 5% confidence level between Antarctic sea-ice oscillation index and Antarctic sea-ice concentration are more than 1/3 of all grids of Antarctica sea-ice, that means the index can represent 1/3 sea-ice area. The winter index has a significant correlation with abnormal summer (June-August) precipitation in China. The area of positive correlation lies in the Yangtze River basin and its south, and that of negative correlation lies mainly in the north of Yangtze River basin. While the winter index is positive (negative), the onset date of South China Sea monsoon is earlier (later), with a probability of 79% (80%). Consequently, a conceptual model is given in term of discussing the possible process between the winter Antarctic sea ice and the monsoon precipitation in China. 相似文献