Background Globally increasing atmospheric nitrogen(N) deposition has altered soil phosphorus(P) transforma-tions and availability, and thereby influenced structure and function of terrestrial ecosystems. Edaphic char...Background Globally increasing atmospheric nitrogen(N) deposition has altered soil phosphorus(P) transforma-tions and availability, and thereby influenced structure and function of terrestrial ecosystems. Edaphic characteristics and chemical form of deposited N could be important factors determining impacts of N deposition on soil P transfor-mations, yet the underlying mechanisms remain largely unknown. Objectives of this study were to examine how min-eral-N and amino N differently affect P fractions, and identify key soil properties determining N addition impacts on soil P transformations. Considering that amino N is an important component of deposited N and forest soils vary greatly in different regions, the results of present study can guide the management of forests across different soils under ongoing N deposition scenarios.Methods We conducted a 60-day laboratory experiment to investigate the effects of N addition(NH4NO3and gly-cine) on soil P fractions and related biochemical properties in four representative forest soils(brown, yellow brown, aeolian sandy, and red soils) in China. Glycine and NH4NO3were separately added at three rates(5, 10 and 20 g N m–2yr–1).Results Firstly, the percent changes in organic P fractions with N addition were significantly greater than changes in inorganic P fractions across all soils. Secondly, the percent changes in P fractions with glycine and NH4NO3addi-tions were significantly correlated across all soils and treatments. However, glycine addition had significantly greater impacts on organic P fractions than NH4NO3addition in the aeolian sandy and red soils with low organic carbon content. Thirdly, P fractions responded differently to N addition among the four soils. N-induced changes in microbial biomass and phosphatase activities, p H, exchangeable Ca2+and Mg2+contributed differently to the changes in P frac-tions with N addition in the four soils.Conclusions The different responses of P fractions to N addition in the four soils were mainly generated by the dif-ferences in extent of microbial N limitation, acid buffering capacity, and cation exchange capacity among the soils. The different impacts of mineral and amino N on soil P fractions can be ascribed to their divergent effects on soil p H, microbial biomass and activities.展开更多
We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input...We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input intensity when an acousto-optic modulator is applied to shift the laser frequency from the resonance. We show the stabilization of a strong 795- nm laser detuned up to 550 MHz from the 87Rb 5S1/2 F=2→5P1/2F'=2 transition. The locking range can be modifed by controlling the bufer gas pressure. A laser line width of 2 MHz is achieved over 10 min.展开更多
基金supported by the National Natural Science Foundation of China(Grant number 41877341)sub-project of the National Key Research and Development Program of China(Grant number 2022YFD2301403-4).
文摘Background Globally increasing atmospheric nitrogen(N) deposition has altered soil phosphorus(P) transforma-tions and availability, and thereby influenced structure and function of terrestrial ecosystems. Edaphic characteristics and chemical form of deposited N could be important factors determining impacts of N deposition on soil P transfor-mations, yet the underlying mechanisms remain largely unknown. Objectives of this study were to examine how min-eral-N and amino N differently affect P fractions, and identify key soil properties determining N addition impacts on soil P transformations. Considering that amino N is an important component of deposited N and forest soils vary greatly in different regions, the results of present study can guide the management of forests across different soils under ongoing N deposition scenarios.Methods We conducted a 60-day laboratory experiment to investigate the effects of N addition(NH4NO3and gly-cine) on soil P fractions and related biochemical properties in four representative forest soils(brown, yellow brown, aeolian sandy, and red soils) in China. Glycine and NH4NO3were separately added at three rates(5, 10 and 20 g N m–2yr–1).Results Firstly, the percent changes in organic P fractions with N addition were significantly greater than changes in inorganic P fractions across all soils. Secondly, the percent changes in P fractions with glycine and NH4NO3addi-tions were significantly correlated across all soils and treatments. However, glycine addition had significantly greater impacts on organic P fractions than NH4NO3addition in the aeolian sandy and red soils with low organic carbon content. Thirdly, P fractions responded differently to N addition among the four soils. N-induced changes in microbial biomass and phosphatase activities, p H, exchangeable Ca2+and Mg2+contributed differently to the changes in P frac-tions with N addition in the four soils.Conclusions The different responses of P fractions to N addition in the four soils were mainly generated by the dif-ferences in extent of microbial N limitation, acid buffering capacity, and cation exchange capacity among the soils. The different impacts of mineral and amino N on soil P fractions can be ascribed to their divergent effects on soil p H, microbial biomass and activities.
基金supported by the National Natural Science Foundation of China(Nos.60925022,10804097,and 11104243)the National "973" Program of China(No.2013CB329501)the Fundamental Research Funds for the Central Universities(No.2012FZA3001)
文摘We experimentally demonstrate a simple modulation-free scheme for ofset locking the frequency of a laser using bufer gas-induced resonance. Our scheme excludes the limitation of low difraction efciency and laser input intensity when an acousto-optic modulator is applied to shift the laser frequency from the resonance. We show the stabilization of a strong 795- nm laser detuned up to 550 MHz from the 87Rb 5S1/2 F=2→5P1/2F'=2 transition. The locking range can be modifed by controlling the bufer gas pressure. A laser line width of 2 MHz is achieved over 10 min.
