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 共查询到19条相似文献，搜索用时 15 毫秒
1.
Quantitative relationship between pollen and vegetation in northern China   总被引：14，自引：0，他引：14  
205 surface pollen samples from different communities in Northern China were analyzed to understand the quantitative relationship between pollen and its original vegetation. Pollen analysis and vegetation investigation show that the pollen assemblages differ a lot in different vegetation regions. Arboreal pollen account for more than 30% in temperate broad-deciduous forests region. In temperate steppe regions, herb pollen percentages are more than 90%, where Artemisia and Chenopodiaceae are domi- nant pollen types with Artemisia percentages more than 30%. In temperate desert, Chenopodiaceae pollen percentages are more than Artemisia, where ferns are rare. Cyperaceae pollen percentages are more than 20% in sub-alpine or cold meadows. The relations between pollen percentages and vegeta- tion cover indicate that most arboreal pollen shows a close relationship with parent plant covers, most shrubby pollen types have more or less correlations, but most herbs do not show clear correlations. For arboreal pollen types, Picea pollen shows the closest correlation with spruce trees coverage, then is Quercus and Carpinus. Betula, Larix and Juglans have also high correlation coefficients with their plants coverage, but Betula pollen is of overrepresented pollen type and more than 40% in birch forest, while Larix and Juglans pollen is underrepresented and pollen percentages are more than 10% in Larix or Juglans pure forests. Pinus is of overrepresented pollen type, and pollen percentages have some relations with plants cover. Pine forest might present when Pinus pollen percentages are more than 30%. The relations between Ulmus and Populus pollen percentages and vegetation cover are not close, where they are mixed with other arbors, they cannot be recorded easily, but if their pollen percentages are more than 1%, Ulmus or Populus trees should exist. For shrubby pollen types, the correlation be- tween Vitex pollen percentages and vegetation cover is the highest, then is Corylus, Tamariaceae and Nitraria, and their pollen percentages are less than 1% where original plant are absent. Caragana and Spiraea pollen percentages have some relations with vegetation cover. The relations between pollen percentages and vegetation cover are not clear for Rosaceae and Saxifragaceae. For herb pollen types, Cyperaceae pollen has the closest correlation with vegetation cover, where pollen percentages are more than 20% when Cyperaceae are constructive or dominant species in vegetation, and pollen per- centages are less than 5% where Cyperaceae are not constructive or dominant species (cover less than 30%). Artemisia and Chenopodiaceae pollen percentages mainly have close relations with ecological regions. The relations between pollen percentages and cover are not clear for Gramineae, Legumi- nosae and Compositae.  相似文献   

2.
Study on vegetation ecological water requirement in Ejina Oasis   总被引：11，自引：0，他引：11  
The Ecological Water Requirement (EWR) of desert oasis is the amount of water required to maintain a normal growth of vegetation in the special ecosystems. In this study EWR of the Ejina desert oasis is estimated through the relational equation between normalized difference vegetation index (NDVI), productivity and transpiration coefficient, which was established by a combination of the RS, GIS, GPS techniques with the field measurements of productivity. The results show that about 1.53×108 m3 water would be needed to maintain the present state of the Ejina Oasis, and the ecological water requirement would amount to 3.49×108 m3 if the existing vegetation was restored to the highest productivity level at present. Considering the domestic water requirement, river delivery loss, oasis vegetation water con-sumption, farmland water demand, precipitation recharge, etc., the draw-off discharge of the Heihe River (at Longxin Mount) should be 1.93×108―2.23 ×108 m3 to maintain the present state of the Ejina Oasis, and 4.28×108―5.17×108 m3 to make the existing vegetation be restored to the highest productiv-ity level at present.  相似文献   

3.
Using China's ground observations, e.g., forest inventory, grassland resource, agricultural statistics, climate, and satellite data, we estimate terrestrial vegetation carbon sinks for China's major biomes between 1981 and 2000. The main results are in the following: (1) Forest area and forest biomass car- bon (C) stock increased from 116.5×106 ha and 4.3 Pg C (1 Pg C = 1015 g C) in the early 1980s to 142.8×106 ha and 5.9 Pg C in the early 2000s, respectively. Forest biomass carbon density increased form 36.9 Mg C/ha (1 Mg C = 106 g C) to 41.0 Mg C/ha, with an annual carbon sequestration rate of 0.075 Pg C/a. Grassland, shrub, and crop biomass sequestrate carbon at annual rates of 0.007 Pg C/a, 0.014― 0.024 Pg C/a, and 0.0125―0.0143 Pg C/a, respectively. (2) The total terrestrial vegetation C sink in China is in a range of 0.096―0.106 Pg C/a between 1981 and 2000, accounting for 14.6%―16.1% of carbon dioxide (CO2) emitted by China's industry in the same period. In addition, soil carbon sink is estimated at 0.04―0.07 Pg C/a. Accordingly, carbon sequestration by China's terrestrial ecosystems (vegetation and soil) offsets 20.8%―26.8% of its industrial CO2 emission for the study period. (3) Considerable uncertainties exist in the present study, especially in the estimation of soil carbon sinks, and need further intensive investigation in the future.  相似文献   

4.
As a result of serious soil erosion on the Loess Pla-teau of China, about 1.6 billion tons of silt discharge into the downstream and 0.4 billion tons deposit on the riverbed every year, causing serious threat to the life and property of the local people on both banks of the lower Yellow River[1]. Since the 1950s, the Chinese government has initiated the work on soil and water conservation and environmental management on the Loess Plateau and formulated the guiding principle of hillslope and …  相似文献   

5.
~~Holocene grassland vegetation, climate and human impact in central eastern Inner Mongolia1.Ye,D.Z.,Chou,J.E,Liu,J.Y.et al.,Causes of sand-stormy weather in northern China and control measures,Acta Geographica Sinica(in Chinese),2000,55(5):513-520. 2.Qiu,X.E,Zeng,Y.,Miao,Q.L.,Temporal spatial distribution as well as tracks and source areas of sand dust storms in China,Acta Geographica Sinica(in Chinese),2001,56(3):316-322. 3.Cui,H.T,Kong,Z.C,Preliminary analysis on the cli…  相似文献   

6.
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7.
This paper presents 16500-year-long high-resolution pollen and spore records from sediments of core 18287 on the continental slope of the southern South China Sea. In the period of 16.5―13.9 ka B.P., the low-mountain rainforest dominated the continental slope of the South China Sea. And in the period of 13.9―10.2 ka B.P., the lowland rainforest and ferns expanded greatly, while the low-mountain rainforest shrank, which indicated a warming at the last deglaciation. Also during this period, the pollen sedi-mentation rates reduced sufficiently. This might imply a rise of the sea level and therefore the sub-mergence of the shelf, resulting in the broadening of the distance between the source area and the slope. After 10.2 ka B.P, decreasing of the fern indicates the early Holocene (10.2―7 ka B.P.) is a cold period, while the increasing of fern marks the rising temperature (7―3.6 ka B.P.).  相似文献   

8.
During the late Pleistocene, a number of climatic fluctuations such as the Heinrich events were recorded in the climatic proxies in the Loess Plateau and in North China[1―7]. Most of these records were based on geophysical and geochemical evidence[1―4]. Therefore, more biologic evidence is necessary for explaining the regional ecosystems in response to climatic change in the Loess Plateau during this period since pollen re-cords in other areas presented strong evidence to cli-matic fluctu…  相似文献   

9.
Sporopollen analysis on a 346 cm peat record at Dahu, Jiangxi, chronologically constrained by 16 AMS 14C datings, provides an opportunity to reconstruct the vegetation evolution stages responding to cli-mate change in South China since the last glacial maximum. The result shows that during 18330-15630 cal a B.P., broad-leaved forest dominated the area, corresponding to mild, cool and fairly humid climate. At the interval of 15630-11600 cal a B.P., several evergreen broad-leaved species appeared within the broad-leaved forest, indicating moderate and humid condition. During early Holocene, broad-leaved evergreen forest community was constructed as Castanopsis/Lithorcarpus principally developed, suggesting a warm and humid scenario until 6000 cal a B. P. Since 6000 cal a B. P., abrupt forest deterioration happened with an contemporary increase of fern and herb communities, repre-senting a turnover to relatively cool and dry condition and as well, possible impact from human activi-ties. Meanwhile, several relatively cool and dry events can be identified in the sporopollen record, they can be correlated to the North Atlantic Heinrich event, YD and Holocene millennial-scale oscillations, implying that the low latitude climate was coupled with high latitude influences. Moreover, the varia-tions of temperature and humidity since LGM at Dahu were much smaller when compared with the re-cords in north monsoonal China.  相似文献   

10.
In this study, an EnKF-based assimilation algorithm was implemented to estimate root-zone soil moisture (RZSM) using the coupled LSP–DSSAT model during a growing season of corn. Experiments using both synthetic and field observations were conducted to understand effects of simultaneous state–parameter estimation, spatial and temporal update frequency, and forcing uncertainties on RZSM estimates. Estimating the state–parameters simultaneously with every 3-day assimilation of volumetric soil moisture (VSM) observations at 5 depths lowered the average standard deviation (ASD) and the root mean square error (RMSE) for RZSM by approximately 1.77% VSM (78%) and 2.18% VSM (93%), respectively, compared to the open-loop ASD where as estimating only states lowered the ASD by approximately 1.26% VSM (56%) and the RMSE by 1.66% VSM (71%). The synthetic case obtained RZSM estimates closer to the observations than the MicroWEX-2 case, particularly after precipitation/irrigation events. The differences in EnKF performance between MicroWEX-2 and synthetic observations may indicate other sources of errors in addition to those in parameters and forcings, such as errors in model biophysics.  相似文献   

11.
A series of dust pollen samples was collected along N-S transects in east China (18°N to 53°N latitudes). Sample sites extend from the cold-temperate zone in the north to the tropical region in the south. Pollen taxa characterize each region and reflect the natural and devastated vegetation as well as corre- sponding climatic zones. The quantitative pollen data can be used to estimate the spatial distribution of planted and introduced species. Valuable information of human disturbance of the natural forest is evaluated by quantitative comparison between dust pollen and in-situ pollen of protected forest. In addition, percentages of grass pollen vary regularly from north to south that is consistent with spatial distribution of net primary productivity in east China. Among all grasses, Artemisia and the Gramineae carry the clearest signal: their ratio increases northwards and therefore represent a suitable and con- venient tool for palaeoclimate reconstructions.  相似文献   

12.
Knowledge of long-term change in vegetation and climate in semi-arid/arid regions is essential for the study of current climate and development of mitigation strategies against severe drought. Here, a fossil pollen record of annually-varved core from Sugan Lake in interior Qaidam Basin was quantitatively analyzed to reconstruct changes in vegetation, floristic diversity and drought frequency. Results of biomization suggested that regional vegetation was desert vegetation with three short-term occupations of temperate steppe/xerophytic shrub during the last 2700 years. Floristic diversity generally increased/decreased with the expansion/degradation of desert vegetation. Moisture fluctuations showed three distinct stages(extremely dry between 742 BC and ~AD500, relatively wet with an increasing trend between ~AD500 and 1200 and relatively wet with frequent fluctuations after AD1200), interrupted by 14 drought events. Spectral analysis and continuous wavelet transform of moisture variation revealed 200-and 120-year cycles. According to cross-wavelet transform analysis, major drought frequency of ~200-year was explicitly correlated to solar activity. It's suggested that the centennial-scale drought frequency was mainly driven by solar activity, through modulation of large-scale atmospheric circulation. Furthermore, the effect of surface temperature–evaporation and uplifting/subsiding air flow should be notable. The climatic drought in interior Qaidam Basin could be intensified under the continuous global warming.  相似文献   

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14.
Spatiotemporal variations of Chinese Loess Plateau vegetation cover during 1981–2006 have been investigated using GIMMS and SPOT VGT NDVI data and the cause of vegetation cover changes has been analyzed, considering the climate changes and human activities. Vegetation cover changes on the Loess Plateau have experienced four stages as follows: (1) vegetation cover showed a continued increasing phase during 1981–1989; (2) vegetation cover changes came into a relative steady phase with small fluctuations during 1990–1998; (3) vegetation cover declined rapidly during 1999–2001; and (4) vegetation cover increased rapidly during 2002–2006. The vegetation cover changes of the Loess Plateau show a notable spatial difference. The vegetation cover has obviously increased in the Inner Mongolia and Ningxia plain along the Yellow River and the ecological rehabilitated region of Ordos Plateau, however the vegetation cover evidently decreased in the hilly and gully areas of Loess Plateau, Liupan Mountains region and the northern hillside of Qinling Mountains. The response of NDVI to climate changes varied with different vegetation types. NDVI of sandy land vegetation, grassland and cultivated land show a significant increasing trend, but forest shows a decreasing trend. The results obtained in this study show that the spatiotemporal variations of vegetation cover are the outcome of climate changes and human activities. Temperature is a control factor of the seasonal change of vegetation growth. The increased temperature makes soil drier and unfavors vegetation growth in summer, but it favors vegetation growth in spring and autumn because of a longer growing period. There is a significant correlation between vegetation cover and precipitation and thus, the change in precipitation is an important factor for vegetation variation. The improved agricultural production has resulted in an increase of NDVI in the farmland, and the implementation of large-scale vegetation construction has led to some beneficial effect in ecology. Supported by the National Natural Science Foundation of China (Grant No. 40671019) and the Knowledge Innovation Project of the Institute of Geographical Sciences and Natural Resources Research of Chinese Academy of Sciences  相似文献   

15.
Spatiotemporal variations of Chinese Loess Plateau vegetation cover during 1981-2006 have been investigated using GIMMS and SPOT VGT NDVI data and the cause of vegetation cover changes has been analyzed, considering the climate changes and human activities. Vegetation cover changes on the Loess Plateau have experienced four stages as follows: (1) vegetation cover showed a continued increasing phase during 1981―1989; (2) vegetation cover changes came into a relative steady phase with small fluctuations during 1990―1998; (3) vegetation cover declined rapidly during 1999―2001; and (4) vegetation cover increased rapidly during 2002―2006. The vegetation cover changes of the Loess Plateau show a notable spatial difference. The vegetation cover has obviously increased in the Inner Mongolia and Ningxia plain along the Yellow River and the ecological rehabilitated region of Ordos Plateau, however the vegetation cover evidently decreased in the hilly and gully areas of Loess Plateau, Liupan Mountains region and the northern hillside of Qinling Mountains. The response of NDVI to climate changes varied with different vegetation types. NDVI of sandy land vegetation, grassland and cultivated land show a significant increasing trend, but forest shows a decreasing trend. The results obtained in this study show that the spatiotemporal variations of vegetation cover are the outcome of climate changes and human activities. Temperature is a control factor of the seasonal change of vegetation growth. The increased temperature makes soil drier and unfavors vegetation growth in summer, but it favors vegetation growth in spring and autumn because of a longer growing period. There is a significant correlation between vegetation cover and precipitation and thus, the change in precipitation is an important factor for vegetation variation. The improved agricultural production has resulted in an increase of NDVI in the farmland, and the implementation of large-scale vegetation construction has led to some beneficial effect in ecology.  相似文献   

16.
Biogeotextiles can be used to facilitate the formation of vegetation cover and to reduce soil erosion.Studies have demonstrated that only biogeotextile or vegetation cover can greatly reduce soil erosion.However, information about the effects of the combination of biogeotextile and vegetation cover on soil erosion is still limited, despite that the combination is the commonly practical form for bare road slope protection. Experimental plots, consisting of a relatively loose surface layer and a c...  相似文献   

17.
The ecosystem services provided by forests modulate runoff generation processes, nutrient cycling and water and energy exchange between soils, vegetation and atmosphere. Increasing atmospheric CO2 affects many linked aspects of forest and catchment function in ways we do not adequately understand. Global levels of atmospheric CO2 will be around 40% higher in 2050 than current levels, yet estimates of how water and solute fluxes in forested catchments will respond to increased CO2 are highly uncertain. The Free Air CO2 Enrichment (FACE) facility of the University of Birmingham's Institute of Forest Research (BIFoR) is the only FACE in mature deciduous forest. The site specializes in fundamental studies of the response of whole ecosystem patches of mature, deciduous, temperate woodland to elevated CO2 (eCO2). Here, we describe a dataset of hydrological parameters – seven weather parameters at each of three heights and four locations, shallow soil moisture and temperature, stream hydrology and CO2 enrichment – retrieved at high frequency from the BIFoR FACE catchment.  相似文献   

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