Aims Natural 15N abundance provides integrated information about nitrogen(N)input,transformation and output,indirectly reflecting N cycling traits within terrestrial ecosystems.However,relationships between natural 15...Aims Natural 15N abundance provides integrated information about nitrogen(N)input,transformation and output,indirectly reflecting N cycling traits within terrestrial ecosystems.However,relationships between natural 15N abundance and N cycling processes are poorly understood in China.Here,our primary objectives were to(i)examine the effects of grazing at varying levels of intensity on d15N of soils and plants in a semi-arid grassland;(ii)detect the relationships between d15N of soils and four major N cycling processes(i.e.mineralization,nitrification,denitrification and ammonia volatilization);and(iii)determine whether d15N of soils can be used as an indicator of N cycling in this semi-arid grassland.Methods The field experiment was conducted within the long-term(17-year)grazing enclosures in a semi-arid grassland in Inner Mongolia.Five grazing intensities(0.00,1.33,2.67,4.00 and 5.33 sheep ha1)were designed.d15N values of topsoils(0–10 cm),surface soils(0–2 cm)and plants were measured in 2006.Differences in d15N of soils and plants between the five grazing intensities were examined.Rates of four soil N cycling processes were measured periodically during the 2005 and 2006 growing seasons.The d15N values of topsoils were linked to the four N cycling processes to investigate their relationships.Important Findings The d15N values of topsoils(5.20–5.96&)were substantially higher than the d15N values of plants(2.51–2.93&)and surface soils(1.44–2.92&)regardless of grazing intensities.The 15N-depleted N losses during microbial decomposition of organic matter in concert with the downward movement of residual substrate over time are the possible causes of higher d15N values in topsoils than in surface soils.In addition,the d15N values of topsoils were positively correlated with the d15N values of both plants and surface soils.Grazing,especially the high-intensity grazing(5.33 sheep ha1),resulted in a significant decrease in d15N of surface soils.However,no statistically significant variations in d15N of topsoil展开更多
Detailed studies on geophysical data and metallogeny of the Qinling region reveal the relationship between the deep crust-mantle structure and the distribution of mineral deposits. In the East Qinling, the Mesoznic mi...Detailed studies on geophysical data and metallogeny of the Qinling region reveal the relationship between the deep crust-mantle structure and the distribution of mineral deposits. In the East Qinling, the Mesoznic mineralization intensity is mainly controlled by the Lushan deep fault zone. The differences of mineral deposit types between the East and West Qinling are related to the distinction of rheological adjusting actions of the crust-mantle. The three-dimensional structure of grade separation bridge pattern controls the distribution of mineral deposits, especially to the distribution of Mesozoic large deposits.展开更多
基金State Key Basic Research and Development Program of China(2010CB833502)Chinese Academy of Sciences(KZCX2-XB2-01).
文摘Aims Natural 15N abundance provides integrated information about nitrogen(N)input,transformation and output,indirectly reflecting N cycling traits within terrestrial ecosystems.However,relationships between natural 15N abundance and N cycling processes are poorly understood in China.Here,our primary objectives were to(i)examine the effects of grazing at varying levels of intensity on d15N of soils and plants in a semi-arid grassland;(ii)detect the relationships between d15N of soils and four major N cycling processes(i.e.mineralization,nitrification,denitrification and ammonia volatilization);and(iii)determine whether d15N of soils can be used as an indicator of N cycling in this semi-arid grassland.Methods The field experiment was conducted within the long-term(17-year)grazing enclosures in a semi-arid grassland in Inner Mongolia.Five grazing intensities(0.00,1.33,2.67,4.00 and 5.33 sheep ha1)were designed.d15N values of topsoils(0–10 cm),surface soils(0–2 cm)and plants were measured in 2006.Differences in d15N of soils and plants between the five grazing intensities were examined.Rates of four soil N cycling processes were measured periodically during the 2005 and 2006 growing seasons.The d15N values of topsoils were linked to the four N cycling processes to investigate their relationships.Important Findings The d15N values of topsoils(5.20–5.96&)were substantially higher than the d15N values of plants(2.51–2.93&)and surface soils(1.44–2.92&)regardless of grazing intensities.The 15N-depleted N losses during microbial decomposition of organic matter in concert with the downward movement of residual substrate over time are the possible causes of higher d15N values in topsoils than in surface soils.In addition,the d15N values of topsoils were positively correlated with the d15N values of both plants and surface soils.Grazing,especially the high-intensity grazing(5.33 sheep ha1),resulted in a significant decrease in d15N of surface soils.However,no statistically significant variations in d15N of topsoil
文摘Detailed studies on geophysical data and metallogeny of the Qinling region reveal the relationship between the deep crust-mantle structure and the distribution of mineral deposits. In the East Qinling, the Mesoznic mineralization intensity is mainly controlled by the Lushan deep fault zone. The differences of mineral deposit types between the East and West Qinling are related to the distinction of rheological adjusting actions of the crust-mantle. The three-dimensional structure of grade separation bridge pattern controls the distribution of mineral deposits, especially to the distribution of Mesozoic large deposits.
