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1.
Land use effects on climate in China as simulated by a regional climate model   总被引：17，自引：0，他引：17  
A regional climate model (RegCM3) nested within ERA40 re-analyzed data is used to investigate the climate effects of land use change over China. Two 15-year simulations (1987―2001), one with current land use and the other with potential vegetation cover without human intervention, are conducted for a domain encompassing China. The climate impacts of land use change are assessed from the difference between the two simulations. Results show that the current land use (modified by anthropogenic ac- tivities) influences local climate as simulated by the model through the reinforcement of the monsoon circulation in both the winter and summer seasons and through changes of the surface energy budget. In winter, land use change leads to reduced precipitation and decreased surface air temperature south of the Yangtze River, and increased precipitation north of the Yangtze River. Land use change signifi- cantly affects summer climate in southern China, yielding increased precipitation over the region, de- creased temperature along the Yangtze River and increased temperature in the South China area (south-end of China). In summer, a reduction of precipitation over northern China and a temperature rise over Northwest China are also simulated. Both daily maximum and minimum temperatures are affected in the simulations. In general, the current land use in China leads to enhanced mean annual precipitation and decreased annual temperature over south China along with decreased precipitation over North China.  相似文献   

2.
To date, few research have been reported on the evolution of C3/C4 vegetation in southern China, and the main mechanism influencing the evolution of C3/C4 vegetation is unclear. That makes it difficult for researchers to understand the competition mechanism of C3 and C4 plants under different climate environments and its relationship with the climate factors. It is also not conducive for researchers to assess the influence of future climate change on regional C3/C4 vegetation. Exactly, C3/C4 vegetation change in the regional-scale will have a significant impact on the global carbon cycle and agricultural production.Therefore, it is especially important to reconstruct the evolutionary history of C3/C4 vegetation in southern China and clarify the influencing mechanism of climate change. In this study, we systematically analyzed stable carbon isotope(δ13 C) of the longchain n-alkanes in sediment samples from eight lakes and four peat profiles in southern China, to reconstruct the spatiotemporal evolution of C3/C4 vegetation in these regions since the Last Glacial Maximum(LGM) and to investigate the climate factors that affect the C4 plant abundance change in the research area. The integrated long-chain n-alkane(C27–C33) stable carbon isotope results of samples from Zhanjiang Huguangyan Maar Lake, Xingyun Lake, Lugu Lake and Dingnan peat showed that, from the LGM to the Early Holocene, C4 plant relative abundance exhibited a gradually increasing trend from 21% to 34%. In the Middle Holocene, the C4 plant abundance significantly declined and reached a lowest value of 10%. In space, the C4 plant abundance generally exhibited a gradually declining trend from south to north in the LGM and the Early Holocene, while it showed an opposite trend in the Holocene Climate Optimum(6.0 cal ka BP). It reflected that the main influencing factor on C4 plants spatial distribution was changing from temperature to precipitation. This study indicated that temperature was the dominant factor affecting C4 plant distribution in southern China, however, when the temperature condition was appropriate, an increase in precipitation(especially more spring precipitation) would reduce the competitive advantages of C4 plants. Therefore, the combination of temperature and seasonal precipitation was the important factor that determines the C3/C4 vegetation proportion change in the southern China. Under the premise that the temperature will rise and precipitation will increase in the future, the reduction of a competitive advantage for the C4 plants could affect agricultural production in China.  相似文献   

3.
As an important part of the regional environment, the wet-dry climate condition is determined by precipitation and potential evapotranspiration(expressed as ETo). Based on weather station data, this study first calculated ETo by using the FAO56Penman-Monteith model. Then, the dryness index K(ratio of ETo to precipitation) was used to study the spatio-temporal variation of the wet-dry condition in China from 1961 to 2015; moreover, dominant climatic factors of the wet-dry condition change were discussed. The annual precipitation and ETo of the Qinling-Huaihe line were close to a balance(K≈1.0). The annual precipitation in most areas exceeded the ETo in the south of this line and the east of Hengduan Mountains(K1.0), where the climate is wet.Furthermore, the precipitation in the northwest inland areas of China, where the climate is dry, was markedly lower than ETo(K≥4.0). The overall annual K of China fluctuated around the 55-year mean and its linear trend was not significant. However, a relatively wet period of about 10 yr(1987–1996) was recorded. The overall annual K of China showed strong cyclicality on the time scale of 3, 7–8, 11 and 26–28 yr, and regional differences of the annual K trends and cyclicality were large. The degrees of wetness in the Northwest China and western Qinghai-Tibet Plateau were substantially increased, whereas the degrees of dryness in the Yunnan-Guizhou Plateau, Sichuan Basin, and Loess Plateau were markedly increased. The linear trend of the annual K in most regions of China was not significant, and the annual K of most areas in China showed strong cyclicality on the 8–14 yr time scale.Precipitation was the dominant factor of wet-dry condition change in most areas, especially in North China, where the annual K change was highly correlated with precipitation.  相似文献   

4.
A case study on the responses of streamflow to climate change in the Toutun River basin was carried out based on data analysis of streamflow, precipitation, and temperatures during the past 50 years.Temporal series of the streamflow change in the Toutun River basin was analyzed and tested using the Mann-Kendall nonparametric test. Results revealed that the annual runoff of the Toutun River had been in a monotonic decreasing trend for the past 50 years. Compared with the 1950s and 1960s, the annual runoff in the 1990s decreased by 4.0×105 m3 and 7.2×105 m3. The precipitation did not show monotonic trend during the past 50 years, but the annual temperature increased by 1.12℃ since the 1950s. Further data analysis indicated that the monthly runoff of the Toutun River decreased significantly from August to October, with precipitation displaying the similar pattern of seasonal change. Analysis suggests that the reduction of streamflow in the Toutun River basin is possibly caused by the seasonal change of precipitation, especially the precipitation reduction in summer, and temperature increases.  相似文献   

5.
Land use and land cover change(LUCC)is one of the important human forcing on climate.However,it is difficult to infer how LUCC will affect climate in the future from the effects of previous LUCC on regional climates in the past.Thus,based on the land cover data recommended by the Coupled Model Intercomparison Project Phase 5(CMIP5),a regional climate model(Reg CM4)was used to investigate the climate effects of future land use change over China.Two 15-year simulations(2036–2050),one with the current land use data and the other with future land cover scenario(2050)were conducted.It is noted that future LUCC in China is mainly characterized by the transition from the grassland to the forest.Results suggest that the magnitudes and ranges of the changes in temperature and precipitation caused by future LUCC show evident seasonality,which are more prominent in summer and autumn.Significant response of climate to future LUCC mainly happens in Northeast China,North China,the Hetao Area,Eastern Qinghai-Tibetan Plateau and South China.Further investigation shows that future LUCC can also produce significant impacts on the atmospheric circulation.LUCC results in abnormal southwesterly wind over extensive areas from the Indian peninsula to the coasts of the South China Sea and South China through the Bay of Bengal.Furthermore,Indian tropical southwest monsoons and South Sea southwest monsoons will both be strong,and the abnormal water vapor convergence from the South China Sea and the Indian Ocean will result in more precipitation in South China.  相似文献   

6.
Through analysis of the distribution pattern and changing characteristics of atmospheric aerosols over the East Asia region during warm seasons in recent 20 a and beyond as well as their possible interac- tive relationship with a variety of meteorological elements, it is found that the high-value zone of aerosol optical depth derived from the Total Ozone Mapping Spectrometer (TOMS), its significant negative correlation zones in terms of sunshine duration (SD) and surface air temperature (SAT) and its significant positive correlation zones with low-level cloud amount (LCC) are co-located in the South China region during warm periods. Based on this finding, the region is referred to as a "significant impact zone" (SI zone) affected by aerosols. Then, a comparative analysis is made on variation differ- ences of observed SAT, SD and LCC, etc. in different regions. It is also found that the LCC is increased and the SD is decreased within the "SI zone" over eastern China during the warm season. These characteristics are more evident than those beyond the zone, while the warming trend within the zone is evidently weaker than that outside it. Studies show that since recent 20 a, under the influence of aerosols, the LCC tend to increase substantially with a clear decrease of SD and an unnoticeable warming trend within the "SI zone". Comparing with the climate change beyond the zone, the difference is significant. Therefore, the effects of atmospheric aerosols on climate is possibly one of the contri- butions to the difference of climate change existed between the southern and northern parts of the Eastern China during a warm season.  相似文献   

7.
Spatiotemporal dynamic simulation of grassland carbon storage in China   总被引：1，自引：0，他引：1  
Based on the Terrestrial Ecosystem Model(TEM 5.0), together with the data of climate(temperature, precipitation and solar radiation) and environment(grassland vegetation types, soil texture, altitude, longitude and latitude, and atmospheric CO2 concentration data), the spatiotemporal variations of carbon storage and density, and their controlling factors were discussed in this paper. The results indicated that:(1) the total carbon storage of China's grasslands with a total area of 394.93×104 km2 was 59.47 Pg C. Among them, there were 3.15 Pg C in vegetation and 56.32 Pg C in soil carbon. China's grasslands covering 7.0–11.3% of the total world's grassland area had 1.3–11.3% of the vegetation carbon and 9.7–22.5% of the soil carbon in the world grasslands. The total carbon storage increased from 59.13 to 60.16 Pg C during 1961–2013 with an increasing rate of 19.4 Tg C yr~(-1).(2) The grasslands in the Qinghai-Tibetan Plateau contributed most to the total carbon storage during 1961–2013, accounting for 63.2% of the total grassland carbon storage, followed by Xinjiang grasslands(15.8%) and Inner Mongolia grasslands(11.1%).(3) The vegetation carbon storage showed an increasing trend, with the average annual growth rate of 9.62 Tg C yr~(-1) during 1961–2013, and temperature was the main determinant factor, explaining approximately 85% of its variation. The vegetation carbon storage showed an increasing trend in most grassland regions, however, a decreasing trend in the central grassland in the southern China, the western and central parts of the Inner Mongolian grasslands as well as some parts on the Qinghai-Tibetan Plateau. The soil carbon storage showed a significantly increasing trend with a rate of 7.96 Tg C yr~(-1), which resulted from the interaction of more precipitation and low temperature in the 1980 s and 1990 s. Among them, precipitation was the main determinant factor of increasing soil carbon increases of China's grasslands.  相似文献   

8.
The global climate warming accelerated in the 1980s has become a focus in the world. Based on the month by month and year by year temperature data from 160 representative stations throughout the country during 1951-1999, this paper analyses annual and four seasons' temperature variations of China since the 1980s. It was found out that the non-equalibrium response with relative great regional and seasonal differences is represented in the country's climate warming. In regional changes a trend of "warm in the north and cold in the south" occurs whereas in seasonal changes, the characters of "warm in winter and cool in summer" present. Significant verification of the temperature variations conducted in terms of mathematical statistics reveals that a confidence level of over 95% has been basically reached in areas north of the Yangtze River. Meanwhile, according to data of diurnal mean temperature steadily passing through accumulated temperature ≥10℃ from 335 stations since 1951 or since the founding of the stations in the early 1950s to 1999, comparative analysis of the data of the last 19 years with that of the first 30 years was conducted and the accumulated temperature ≥10℃ and the variation range of the persistent number of days ≥10℃ were obtained. It was concluded that a general northward shift of central subtropics, north subtropics, warm temperate zone, mesothermal zone and frigid temperate zone of eastern China was observed. The northward shift of north subtropics and warm temperate zone was obvious but changes of south subtropics and marginal tropics were insignificant. In western China, in addition to southwestern Yunnan, the Qinghai-Tibet Plateau and western Inner Mongolia where the temperature zones of each either shifted northward or trended to move upward, not much changes were found in other areas or they shifted southward slightly and declined.  相似文献   

9.
Based on daily precipitation data of more than 2000 Chinese stations and more than 50 yr, we constructed time series of extreme precipitation based on six different indices for each station: annual and summer maximum(top-1) precipitation,accumulated amount of 10 precipitation maxima(annual, summer; top-10), and total annual and summer precipitation.Furthermore, we constructed the time series of the total number of stations based on the total number of stations with top-1 and top-10 annual extreme precipitation for the whole data period, the whole country, and six subregions, respectively. Analysis of these time series indicate three regions with distinct trends of extreme precipitation:(1) a positive trend region in Southeast China,(2) a positive trend region in Northwest China, and(3) a negative trend region in North China. Increasing(decreasing)ratios of 10–30% or even 30% were observed in these three regions. The national total number of stations with top-1 and top-10 precipitation extremes increased respectively by 2.4 and 15 stations per decade on average but with great inter-annual variations.There have been three periods with highly frequent precipitation extremes since 1960:(1) early 1960 s,(2) middle and late 1990 s,and(3) early 21 st century. There are significant regional differences in trends of regional total number of stations with top-1 and top-10 precipitation. The most significant increase was observed over Northwest China. During the same period, there are significant changes in the atmospheric variables that favor the decrease of extreme precipitation over North China: an increase in the geopotential height over North China and its upstream regions, a decrease in the low-level meridional wind from South China coast to North China, and the corresponding low moisture content in North China. The extreme precipitation values with a50-year empirical return period are 400–600 mm at the South China coastal regions and gradually decrease to less than 50 mm in Northwest China. The mean increase rate in comparison with 20-year empirical return levels is 6.8%. The historical maximum precipitation is more than twice the 50-year return levels.  相似文献   

10.
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11.
Carbon preference index (CPI) of long-chain n-alkanes preserved in surface soil increases gradually from southeastern China to the north margin of Loess Plateau.Along this latitudinal transect,the CPI value correlates to relative humidity,precipitation,and temperature with a negative linear relationship,respectively,whereas the correlation of CPI to temperature is relatively weak.In the Wuyi,Shennongjia,and Tianshan Mountains,CPI values do not change systemically with altitude increasing (or temperature decreasing).However,mean value of CPI for the individual mountain increases in turn from the humid mountain to the arid.These results jointly suggest that aridity (or humidity) is a dominate climate factor in altering soil CPI value.High CPI values of geological records therefore indicate the arid paleoclimate.Though long-chain n-alkanes in soil are derived mainly from leaf wax of terrestrial vascular plants,the regular latitudinal variations of soil CPI might not be caused by the change of vegetation.We speculate that increased long-chain n-alkanes from microbes and/or enhanced biodegradation in the humid climate lead to the decrease of soil CPI.  相似文献   

12.
Based on Argo sea surface salinity(SSS) and the related precipitation(P), evaporation(E), and sea surface height data sets, the climatological annual mean and low-frequency variability in SSS in the global ocean and their relationship with ocean circulation and climate change were analyzed. Meanwhile, together with previous studies, a brief retrospect and prospect of seawater salinity were given in this work. Freshwater flux(E-P) dominated the mean pattern of SSS, while the dynamics of ocean circulation modulated the spatial structure and low-frequency variability in SSS in most regions. Under global warming, the trend in SSS indicated the intensification of the global hydrological cycle, and featured a decreasing trend at low and high latitudes and an increasing trend in subtropical regions. In the most recent two decades, global warming has slowed down, which is called the"global warming hiatus". The trend in SSS during this phase, which was different to that under global warming, mainly indicated the response of the ocean surface to the decadal and multi-decadal variability in the climate system, referring to the intensification of the Walker Circulation. The significant contrast of SSS trends between the western Pacific and the southeastern Indian Ocean suggested the importance of oceanic dynamics in the cross-basin interaction in recent decades. Ocean Rossby waves and the Indonesian Throughflow contributed to the freshening trend in SSS in the southeastern Indian Ocean, while the increasing trend in the southeastern Pacific and the decreasing trend in the northern Atlantic implied a long-term linear trend under global warming. In the future, higher resolution SSS data observed by satellites, together with Argo observations, will help to extend our knowledge on the dynamics of mesoscale eddies, regional oceanography, and climate change.  相似文献   

13.
Wu  Haibin  Li  Qin  Yu  Yanyan  Sun  Aizhi  Lin  Yating  Jiang  Wenqi  Luo  Yunli 《中国科学:地球科学(英文版)》2019,62(8):1269-1278
Quantitative paleoclimatic reconstruction is crucial for understanding the operation and evolution of the global climate system.For example,a quantitative paleoclimatic reconstruction for the Last Glacial Maximum(18±2 ka~(14)C,LGM)is fundamental to understanding the evolution of Earth’s climate during the last glacial-interglacial cycle.Previous quantitative palaeoclimate reconstructions in China are generally based on statistical comparison of modern pollen assemblages and modern climate data.These methods are based on the premise that vegetation-climate interactions remain the same through time,and implicitly assume that the interactions are independent of changes in seasonality and atmospheric CO_2concentration.However,these assumptions may not always be valid,which may affect the reconstructions.Here,we present the results of a quantitative study of the LGM climate of China based on an improved inverse vegetation model which incorporates physiological processes combined with a new China Quaternary Pollen Database.The results indicate that during the LGM,mean annual temperature(ANNT),mean temperature of the coldest month(MTCO)and mean temperature of the warmest month in China were lower by～5.6±0.8,～11.0±1.6 and～2.6±0.9°C,respectively,compared to today,and that the changes in ANNT were mainly due to the decrease of MTCO.The ANNT decrease in southern China was～5.5±0.5°C.Mean annual precipitation was lower by～46.3±17.8 mm compared to today and was especially low in northern China(～51.2±21.4 mm)due to the decrease in summer rainfall.Comparison of our results with recent outputs from paleoclimatic modelling reveals that while the latter are broadly consistent with our estimated changes in mean annual climatic parameters,there are substantial differences in the seasonal climatic parameters.Our results highlight the crucial importance of developing seasonal simulation on paleoclimatic models,as well as the need to improve the quality of paleoclimatic reconstructions based on proxy records from geological archives.  相似文献   

14.
The geographical distribution of dominant plant species in China was georeferenced and climatic variables were interpolated into all grids.Accordingly,the percentage distributions of principal pollen taxa based on 1860 surface pollen sites in China were selected and the related climate values were interpolated with the same method. The geographical and climatic comparison between the two data-sets indicated that the climate threshold of most pollen taxa from surface pollen is coherent with plant distributions. The climatic envelopes of dominant plant are mostly accordant with those of pollen taxa at certain levels. However, some distinct offsets of the climate ranges exist between the two datasets for most pollen taxa identified at family level, such as Ericaceae,Asteraceae, Poaceae and Chenopodiaceae. The present study provides for the first time rich information on temperature and precipitation in relation to pollen and plant distribution based on the datasets on a continental scale useful for global ecological modeling and Quaternary palaeoclimate reconstruction.  相似文献   

15.
Climate change characterized by increasing temperature is able to affect precipitation regime and thus surface hydrology.However,the manner in which river sediment loads respond to climate change is not well understood,and related assessment regarding the effect of climate change on sediment loads is lacking.We present a quantitative estimate of changes in sediment loads(from 1.5 Gt yr-1 pre-1990 to 0.6 Gt yr-1 from 1991-2007) in response to climate change in eight large Chinese rivers.Over the past decades,precipitation change coupled with rising temperatures has played a significant role in influencing the sediment delivery dynamics,although human activities, such as reservoir construction,water diversion,sand mining and land cover change,are still the predominant forces. Lower precipitation coupled with rising temperatures has significantly reduced sediment loads delivered into the sea in semi-arid climates（4-61%）.In contrast,increasingly warmer and wetter climates in subtropical zones has yielded more sediment（0.4-11%）,although the increase was offset by human impact.Our results indicate that,compared with mechanical retention by reservoirs,water reduction caused by climate change or human withdrawals has contributed more sediment reduction for the rivers with abundant sediment supply but limited transport capacity（e.g.,the Huanghe）.Furthermore,our results indicate that every 1%change in precipitation has resulted in a 1.3%change in water discharge and a 2%change in sediment loads.In addition,every 1%change in water discharge caused by precipitation has led to a 1.6%change in sediment loads,but the same percentage of water discharge change caused largely by humans would only result in a 0.9%change in sediment loads.These figures can be used as a guideline for evaluating the responses of sediment loads to climate change in similar climate zones because future global warming will cause dramatic changes in water and sediment in river basins worldwide at rates previously unseen.  相似文献   

16.
Cheng  Ying  Liu  Hongyan  Wang  Hongya  Chen  Deliang  Ciais  Philippe  Luo  Yao  Wu  Xiuchen  Yin  Yi 《中国科学:地球科学(英文版)》2021,64(10):1774-1783
Although alpine ecosystems have been commonly recognized as sensitive to recent climate change, few studies have examined its impact on the long-term productivity of vegetation and soil erosion. Using paleoecological records, these two aspects were examined in the alpine zone of the Taibai Mountains(elevation, 3767 m) in monsoon-dominated East Asia since the middle Holocene. Proxies for the productivity of vegetation and severity of soil erosion from high-resolution alpine lacustrine records show that the productivity and soil erosion were closely related to mean annual temperature and summer precipitation from the East Asian Summer Monsoon(EASM), respectively. Specifically, when the mean annual temperature was low and precipitation was abundant, during 5800–4000 calendar years before the present(cal. yr BP), the alpine ecosystem was characterized by low vegetation productivity and severe soil erosion. However, the productivity increased and soil erosion decreased from 4000 cal. yr BP onwards. These results highlight the role of paleoecological evidence in studying ecosystem services on longer time scales, which is significant in making policies for sustainable development under climate change in regions for which such long-term monitoring data are not available.  相似文献   

17.
Using the digital telemetric seismic waveform data of Chengdu and Kunming, this article studies the focal mechanism solutions and the apparent stress values of a large number of small earthquakes, and then analyzes the dynamic variation of regional stress fields and the spatio-temporal distribution of apparent stress values. The annual variation values of the azimuth of average principal stress field before the May 12, 2008 M_S8.0 Wenchuan earthquake in the Sichuan-Yunnan region were 58° from 2003 to 2004, 85° from 2003 to 2005,61° from 2006 to 2007 and 90° from 2006 to April 2008 respectively. In recent years, deflection or disturbances occurred in the azimuth of the average principal stress field in the Sichuan-Yunnan region. Analysis shows that this may be related to the change of stress field states of crustal blocks before and after the December 26, 2004 M_S9.0 Sumatra earthquake and the 2008 M_S8.0 Wenchuan earthquake. The ratio of thrust-type earthquakes in the Sichuan-Qinghai block was on the higher side in the period from 2006 to 2007, and the source faulting type of the regional moderate and small earthquakes had changed before the M_S8.0 Wenchuan earthquake. The change of state of the stress field is consistent with the changes in block displacement fields revealed by GPS data and the crustal shortening velocity vertical to the Longmenshan fault zone. Based on the radiation energy calculated from all bands of the seismic waveform, the value of apparent stress σ_app is obtained. The fluctuation shape of the fitting trend of the apparent stress is related to the intensity of regional seismicity. It reveals that the micro-dynamic fluctuation process of the regional stress value is similar to the azimuth transition of the regional principal compressive stress field, which can be used to probe for pregnant physical processes. Areas with a higher value of apparent stress σ_app are possible areas of potential seismic risk. It can be seen from the spatial distribution of the medium and short-term apparent stress σ_app before the M_S8.0 Wenchuan earthquake, the Longmenshan fault zone is in a low stress distribution area, and the relatively high apparent stress is in the peripheral area. These images may show medium and short-term locking phenomena near the seismogenic tectonics of the M_S8.0 Wenchuan earthquake. For example, changes with time of the focal parameter consistency of the sub-blocks in Sichuan and Yunnan Provinces, continual increase of thrust-type earthquakes in the Sichuan-Qinghai block and the appearance of spatial distribution areas of high apparent σ_app stress. The work on this aspect was continued after the M_S8.0 Wenchuan earthquake, and the results seem to be shown a clearer relationship between these phenomena and future great earthquakes.  相似文献   

18.
Tan  Liangcheng  Liu  Wen  Wang  Tianli  Cheng  Peng  Zang  Jingjie  Wang  Xiqian  Ma  Le  Li  Dong  Lan  Jianghu  Edwards  R. Lawrence  Cheng  Hai  Xu  Hai  Ai  Li  Gao  Yongli  Cai  Yanjun 《中国科学:地球科学(英文版)》2020,63(10):1622-1632
Evaluating anthropogenic impacts on regional vegetation changes during historical time is not only important for a better understanding of the Anthropocene but also valuable in improving the vegetation-climate models. In this study, we analyzed stable isotopes(δ~(18)O, δ~(13)C) and trace elements(Mg/Ca, Sr/Ca) of a stalagmite from Huangchao Cave in central Shandong, northern China.~(230)Th and AMS~(14)C dating results indicate the stalagmite deposited during 174BC and AD1810, with a hiatus between AD638 and 1102. Broad similarities of the δ~(18)O and trace elements in the stalagmite suggest they are reliable precipitation indexes. The δ~(13)C of the stalagmite, a proxy of vegetation change, was generally consistent with local precipitation and temperature variations on a centennial-scale before the 15th century. It typically varied from –9.6‰ to –6.3‰, indicating climate controlled C3 type vegetation during this period. However, a persistent and marked increasing trend in the δ~(13)C record was observed since the 15th century, resulting in δ~(13)C values from –7.7‰ to –1.6‰ in the next four centuries. This unprecedented δ~(13)C change caused by vegetation deterioration cannot be explained by climate change but is fairly consistent with the dramatically increasing population and farmland in Shandong. We suggest that the increasing deforestation and reclamation in central Shandong began to affect vegetation in the mountain region of central Shandong since the 15th century and severely destroyed or even cleared the forest during the 16th–18th century.  相似文献   

19.
Combining the temperature and precipitation data from 77 climatological stations and the climatic and hydrological change data from three headstreams of the Tarim River: Hotan, Yarkant, and Aksu in the study area, the plausible association between climate change and the variability of water resources in the Tarim River Basin in recent years was investigated, the long-term trend of the hydrological time series including temperature, precipitation, and stream-flow was detected, and the possible association between the El Nino/Southern Oscillation (ENSO) and these three kinds of time series was tested. The results obtained in this study show that during the past years, the temperature experienced a significant monotonic increase at the speed of 5%, nearly 1℃rise; the precipitation showed a significant decrease in the 1970s, and a significant increase in the 1980s and 1990s, the average annual precipitation was increased with the magnitude of 6.8 mm per decade. A step change occurred in both temperature and  相似文献   

20.
Historical case studies of climate change impacts and the resulting social responses can provide analogies for better understanding the impacts of current and future climate changes.Around the turn of the 19th century,the climate of the North China Plain experienced a shift from a relatively warm stage in the 18th century to a colder stage in the 19th century,which was characterised by a much colder climate and more frequent and severe floods and droughts.Historical information about refugees,social disorder,grain transportation,and disaster relief on the North China Plain in 1780-1819 is collected from the Veritable Records of the Qing Dynasty(a collection of official records).The mechanism of climate change affecting the food security of the society,as indicated by the development of a refugee problem around the turn of the 19th century,is analyzed by examining the social vulnerability.There are four basic findings:(1) In the 40 years from 1780-1819,the society on the North China Plain was unstable and characterised by a significant deterioration of the refugee situation.The number of refugees increased markedly,and their behaviour became increasingly violent.In the 1780s,most of the disaster victims chose to stay at their residences waiting for relief.From 1790 to 1800,hundreds of thousands of refugees migrated to northeast China.In the 1810s,the frequency of farmer rebellions increased sharply.(2) The increase in instability corresponded to the climatic cooling over the same time period.The increased instability was a result of the negative impacts of climate change accumulating and transmitting to the social level.(3) For food security,a precondition for the negative impacts of climate change on human society was the vulnerability of the regional socioeconomic system,which had a high sensitivity and low capacity to respond.This vulnerability could be described by the following three observations:① The regional balance of supply and demand for food was in a critical state,which led to a high sensitivity and dramatic reduction in yield that was caused by climate change;② the capacity for disaster relief efforts by the government was too low to meet the needs of crisis management;③ the capacity for refugees’ resettlement in eastern Inner Mongolia and northeast China,which both border the North China Plain,was severely restricted by climatic conditions or the quarantine policy.(4) It is estimated that climate change caused the social vulnerability to reach a critical level approximately 20 years earlier on the North China Plain.  相似文献   

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