The occurrence of bumper or poor grain harvests in ancient China plays an important role in explaining how past climate changes affected the economy.Because of the lack of long-term continuous and high-resolution quan...The occurrence of bumper or poor grain harvests in ancient China plays an important role in explaining how past climate changes affected the economy.Because of the lack of long-term continuous and high-resolution quantitative data for reconstructing the series of grain harvests in ancient China,understanding of the impacts and mechanisms involved in climate change is limited.This study presents a method designed for reconstructing grain harvest series by quantifying grain output levels based on the descriptions in historical documents.The method involves setting the grain output level for each year based on very specific meanings of different words,calculating a yield index based on the structure of each level and assessing grain yields(bumper or poor harvests)every 10 years.First,1636 records related to grain yields(including crop yields,food security,agricultural disasters,grain prices,grain storage and people's livelihoods)for each year were retrieved from history books called the Twenty-Four Histories.Second,using this method,a 10-year resolution graded grain harvest series from the Western Han Dynasty to the Five Dynasties(206 BC–960 AD)is reconstructed.Finally,the relationship between the variations in temperature and precipitation and the fluctuation of grain yields is examined.The results show that from the Western Han Dynasty to the Five Dynasties,bumper,average and poor harvest decades accounted for 33.3%,39.3%and 27.4%of the 1,166-year period,respectively.The grain yields during 206 BC–960 AD can be divided into three stages:a period of bumper harvests during 206–51 BC,poor harvests during 50 BC–590 AD and bumper harvests during 591–960 AD.Bumper harvest decades typically experienced a warm climate with normal or high levels of precipitation,while poor harvest decades had a cold and dry climate.A positive correlation was found between temperature and grain yield because a warm climate allows a full use of resources.The observed relationship between precipitation and grain yield indicated that both flooding and droughts cause poor harvests,which confirms that agricultural production in the monsoon climate of eastern China is greatly impacted by conditions of limited heat and extreme precipitation.展开更多
The paper presents the analysis of tendencies in water level changes in 32 lakes in Poland during 1976–2010.Series of monthly,seasonal,and annual precipitation and air temperature for 9 meteorological stations were a...The paper presents the analysis of tendencies in water level changes in 32 lakes in Poland during 1976–2010.Series of monthly,seasonal,and annual precipitation and air temperature for 9 meteorological stations were also studied.The trend analysis for all of the studied series of water levels in lakes showed high spatial and temporal variability.Series of annual water levels in the case of 6 lakes showed statistically significant increasing tendencies,and in 7 lakes,significant decreasing trends.Series of annual amplitudes in the majority of lakes(22) showed a decreasing trend,but they were statistically significant only in three cases.The tendencies for air temperature fluctuations are more statistically significant than precipitation.The key role in determining water level changes is played by local factors,particularly including human economic activity,obscuring the effect of natural factors on water level changes.The paper describes cases of changes in water levels in lakes under anthropopressure related to among others: agricultural irrigations,hydropower infrastructure,water transfers,navigation,or mining.展开更多
基金supported by the Major State Basic Research Development Program of China (973 Program) (Grant No. 2010CB950103)National Natural Science Foundation of China (Grant No. 41071127)Strategic Project of Science and Technology of the Chinese Academy of Sciences (Grant No. XDA05080102)
文摘The occurrence of bumper or poor grain harvests in ancient China plays an important role in explaining how past climate changes affected the economy.Because of the lack of long-term continuous and high-resolution quantitative data for reconstructing the series of grain harvests in ancient China,understanding of the impacts and mechanisms involved in climate change is limited.This study presents a method designed for reconstructing grain harvest series by quantifying grain output levels based on the descriptions in historical documents.The method involves setting the grain output level for each year based on very specific meanings of different words,calculating a yield index based on the structure of each level and assessing grain yields(bumper or poor harvests)every 10 years.First,1636 records related to grain yields(including crop yields,food security,agricultural disasters,grain prices,grain storage and people's livelihoods)for each year were retrieved from history books called the Twenty-Four Histories.Second,using this method,a 10-year resolution graded grain harvest series from the Western Han Dynasty to the Five Dynasties(206 BC–960 AD)is reconstructed.Finally,the relationship between the variations in temperature and precipitation and the fluctuation of grain yields is examined.The results show that from the Western Han Dynasty to the Five Dynasties,bumper,average and poor harvest decades accounted for 33.3%,39.3%and 27.4%of the 1,166-year period,respectively.The grain yields during 206 BC–960 AD can be divided into three stages:a period of bumper harvests during 206–51 BC,poor harvests during 50 BC–590 AD and bumper harvests during 591–960 AD.Bumper harvest decades typically experienced a warm climate with normal or high levels of precipitation,while poor harvest decades had a cold and dry climate.A positive correlation was found between temperature and grain yield because a warm climate allows a full use of resources.The observed relationship between precipitation and grain yield indicated that both flooding and droughts cause poor harvests,which confirms that agricultural production in the monsoon climate of eastern China is greatly impacted by conditions of limited heat and extreme precipitation.
文摘The paper presents the analysis of tendencies in water level changes in 32 lakes in Poland during 1976–2010.Series of monthly,seasonal,and annual precipitation and air temperature for 9 meteorological stations were also studied.The trend analysis for all of the studied series of water levels in lakes showed high spatial and temporal variability.Series of annual water levels in the case of 6 lakes showed statistically significant increasing tendencies,and in 7 lakes,significant decreasing trends.Series of annual amplitudes in the majority of lakes(22) showed a decreasing trend,but they were statistically significant only in three cases.The tendencies for air temperature fluctuations are more statistically significant than precipitation.The key role in determining water level changes is played by local factors,particularly including human economic activity,obscuring the effect of natural factors on water level changes.The paper describes cases of changes in water levels in lakes under anthropopressure related to among others: agricultural irrigations,hydropower infrastructure,water transfers,navigation,or mining.
