Intensive soil tillage is a significant factor in soil organic matter decline in cultivated soils. Both cultivation abandonment and foregoing tillage have been encouraged in the past 30 years to reduce greenhouse gas ...Intensive soil tillage is a significant factor in soil organic matter decline in cultivated soils. Both cultivation abandonment and foregoing tillage have been encouraged in the past 30 years to reduce greenhouse gas emissions and soil erosion. However, the dynamic processes of soil organic carbon (SOC) in areas of either continuous cultivation or abandonment remain unclear and inconsistent.Our aims were to assess and model the dynamic processes of SOC under continuous tillage and after cultivation abandonment in the black soil of Northeast China. Soil profiles were collected of cultivated or abandoned land with cultivation history of 0–100 years. An isotope mass balance equation was used to calculate the proportion of SOC derived from corn debris (C_4) and from natural vegetation (C_3) to deduce the dynamic process. Approximately 40% of SOC in the natural surface soil (0–10 cm) was eroded in the first 5 years of cultivation, increasing to about 75% within 40 years, before a slow recovery. C_4 above 30 cm soil depth increased by 4.5%–5% or 0.11–0.12 g·kg^(-1) on average per year under continuous cultivation, while it decreased by approximately 0.34% annually in the surface soil after cultivation abandonment.The increase in the percentage of C_4 was fitted to a linear equation with given intercepts in the upper 30 cm of soil in cultivated land. A significant relationship between the change of C_4 and time was found only in the surface soil after abandonment of cultivation. These results demonstrate the loss and accumulation of corn-derived SOC in surface black soil of Northeast China under continuous tillage or cultivation abandonment.展开更多
Ye Shu-xian＇s proposal of ＂Road of Jade＂ brings forward a new way to study the origin of civilization. Jade replaced bronze as one of the major criterions of the birth of civilizations. Ye explains jade as a mystic...Ye Shu-xian＇s proposal of ＂Road of Jade＂ brings forward a new way to study the origin of civilization. Jade replaced bronze as one of the major criterions of the birth of civilizations. Ye explains jade as a mystical witchcraft which has a sacred power for the ancient people. Because the jade is produced in the water, and has the similar color with the sky, both of which have significance for the origin of life, jade is thus considered to be the origin of power. The notion of jade-god gave birth to the civilization in ancient China and triggered competition among the settlements, which in turn, advanced the development of civilization.展开更多
Based on the analyses on the quality of educational periodicals and the number of publications and citations in Chinese Social Sciences Citation Index(CSSCI),this paper intends to make an analysis and introduction of ...Based on the analyses on the quality of educational periodicals and the number of publications and citations in Chinese Social Sciences Citation Index(CSSCI),this paper intends to make an analysis and introduction of the general situation of Chinese educational journals and publications during 2000–2004.Results show that the quantity of educational periodicals and papers published in China,their influence,“impact factor”and the quantity of language varieties and quotation types are not completely compatible.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.4157301241571130041 U1612441)
文摘Intensive soil tillage is a significant factor in soil organic matter decline in cultivated soils. Both cultivation abandonment and foregoing tillage have been encouraged in the past 30 years to reduce greenhouse gas emissions and soil erosion. However, the dynamic processes of soil organic carbon (SOC) in areas of either continuous cultivation or abandonment remain unclear and inconsistent.Our aims were to assess and model the dynamic processes of SOC under continuous tillage and after cultivation abandonment in the black soil of Northeast China. Soil profiles were collected of cultivated or abandoned land with cultivation history of 0–100 years. An isotope mass balance equation was used to calculate the proportion of SOC derived from corn debris (C_4) and from natural vegetation (C_3) to deduce the dynamic process. Approximately 40% of SOC in the natural surface soil (0–10 cm) was eroded in the first 5 years of cultivation, increasing to about 75% within 40 years, before a slow recovery. C_4 above 30 cm soil depth increased by 4.5%–5% or 0.11–0.12 g·kg^(-1) on average per year under continuous cultivation, while it decreased by approximately 0.34% annually in the surface soil after cultivation abandonment.The increase in the percentage of C_4 was fitted to a linear equation with given intercepts in the upper 30 cm of soil in cultivated land. A significant relationship between the change of C_4 and time was found only in the surface soil after abandonment of cultivation. These results demonstrate the loss and accumulation of corn-derived SOC in surface black soil of Northeast China under continuous tillage or cultivation abandonment.
基金This paper is supported by General Financial Grant from the China Postdoctoral Science Foundation （Grant No.： 2013M542363）.
文摘Ye Shu-xian＇s proposal of ＂Road of Jade＂ brings forward a new way to study the origin of civilization. Jade replaced bronze as one of the major criterions of the birth of civilizations. Ye explains jade as a mystical witchcraft which has a sacred power for the ancient people. Because the jade is produced in the water, and has the similar color with the sky, both of which have significance for the origin of life, jade is thus considered to be the origin of power. The notion of jade-god gave birth to the civilization in ancient China and triggered competition among the settlements, which in turn, advanced the development of civilization.
文摘Based on the analyses on the quality of educational periodicals and the number of publications and citations in Chinese Social Sciences Citation Index(CSSCI),this paper intends to make an analysis and introduction of the general situation of Chinese educational journals and publications during 2000–2004.Results show that the quantity of educational periodicals and papers published in China,their influence,“impact factor”and the quantity of language varieties and quotation types are not completely compatible.
