Forest ecosystems on China's Loess Plateau are receiving increasing attention because of their special importance in carbon fixation and conservation of soil and water in the region.Soil respiration was investigat...Forest ecosystems on China's Loess Plateau are receiving increasing attention because of their special importance in carbon fixation and conservation of soil and water in the region.Soil respiration was investigated in Platycladus orientalis forest stands of the region at diurnal and seasonal scales.The daily and seasonal average values of soil respiration were 2.53μmol·m^(-2)·s^(-1)and 3.78μmol·m^(-2)·s^(-1),respectively.On a diurnal and seasonal scale,the variations of soil respiration in the P.orientalis forest show a one-peak pattern.The diurnal dynamics of soil respiration were mainly driven by soil temperature.However,the relationship between soil respiration and soil temperature was not significant,mainly because of the hysteresis effect of soil respiration on soil temperature.Soil moisture plays another dominant role in the ecosystem carbon balance,but was not affected by soil temperature in P.orientalis forest on the semiarid Loess Plateau.展开更多
Based on 15N tracer technique,absorption of different concentrations of ammonium nitrogen(N-NH^(4+)),nitrate nitrogen(N-NO^(3-))and glycine(NGly)by root of six species of alpine forage(Puccinellia tenuiflora,Poa crymo...Based on 15N tracer technique,absorption of different concentrations of ammonium nitrogen(N-NH^(4+)),nitrate nitrogen(N-NO^(3-))and glycine(NGly)by root of six species of alpine forage(Puccinellia tenuiflora,Poa crymophila,Festuca sinensis,Elymus nutans,Elymus sibiricus and Bromus inermis)was studied in a hydroponic culture.The uptake kinetic parameter was analyzed according to Michaelis-Menten equation.The Michaelis-Menten equation represents the velocity equation for the relationship between the initial rate of an enzymatic reaction and the substrate concentration.The result showed that the absorption range of ammonium nitrogen,nitrate nitrogen and glycine by root of six species of alpine plant were 1.1-20.9μmol·g^(-1)·h^(-1),0.4-3.4μmol·g^(-1)·h^(-1) and 0.1-3.7μmol·g^(-1)·h^(-1),which accounts for 68.8%-74.7%,12.0%-27.0%and 4.3%-13.4%of total absorptivity,respectively.The six kinds of P.tenuiflora,P.crymophila,F.sinensis,E.nutans,E.sibiricus and B.inermis showed significant difference in nitrogen absorption.At the same concentration,the absorption of nitrogen in different forms of the same herbage is different.The absorptive amount of ammonium nitrogen was the highest among them,then the glycine,the nitrate nitrogen was least absorbed.The results could provide a theoretical basis for nitrogen utilization in alpine forages.For example,P.tenuiflora showed a much higher ability of absorbing nitrogen nutrition in a high salt environment and could be a more suitable herbage to be planted in saline-alkali soil in the Qinghai-Tibet Plateau as compared with E.nutans.展开更多
基金National Natural Science Foundation of China （41201258） The Chinese Academy of Sciences through the West Light Foundation to Shi Wei-Yu and Strategic Priority Research Program （XDA05050202）
文摘Forest ecosystems on China's Loess Plateau are receiving increasing attention because of their special importance in carbon fixation and conservation of soil and water in the region.Soil respiration was investigated in Platycladus orientalis forest stands of the region at diurnal and seasonal scales.The daily and seasonal average values of soil respiration were 2.53μmol·m^(-2)·s^(-1)and 3.78μmol·m^(-2)·s^(-1),respectively.On a diurnal and seasonal scale,the variations of soil respiration in the P.orientalis forest show a one-peak pattern.The diurnal dynamics of soil respiration were mainly driven by soil temperature.However,the relationship between soil respiration and soil temperature was not significant,mainly because of the hysteresis effect of soil respiration on soil temperature.Soil moisture plays another dominant role in the ecosystem carbon balance,but was not affected by soil temperature in P.orientalis forest on the semiarid Loess Plateau.
基金This work was supported in parts by the Second Tibetan Plateau Scientific Expedition and Research(STEP)Program(2019QZKK0302)Qinghai Provinceʼs first batch of special funds for the central government to guide local scientific and technological development in 2021(2021ZY002)the National Natural Sciences Foundation of China(41761107).
文摘Based on 15N tracer technique,absorption of different concentrations of ammonium nitrogen(N-NH^(4+)),nitrate nitrogen(N-NO^(3-))and glycine(NGly)by root of six species of alpine forage(Puccinellia tenuiflora,Poa crymophila,Festuca sinensis,Elymus nutans,Elymus sibiricus and Bromus inermis)was studied in a hydroponic culture.The uptake kinetic parameter was analyzed according to Michaelis-Menten equation.The Michaelis-Menten equation represents the velocity equation for the relationship between the initial rate of an enzymatic reaction and the substrate concentration.The result showed that the absorption range of ammonium nitrogen,nitrate nitrogen and glycine by root of six species of alpine plant were 1.1-20.9μmol·g^(-1)·h^(-1),0.4-3.4μmol·g^(-1)·h^(-1) and 0.1-3.7μmol·g^(-1)·h^(-1),which accounts for 68.8%-74.7%,12.0%-27.0%and 4.3%-13.4%of total absorptivity,respectively.The six kinds of P.tenuiflora,P.crymophila,F.sinensis,E.nutans,E.sibiricus and B.inermis showed significant difference in nitrogen absorption.At the same concentration,the absorption of nitrogen in different forms of the same herbage is different.The absorptive amount of ammonium nitrogen was the highest among them,then the glycine,the nitrate nitrogen was least absorbed.The results could provide a theoretical basis for nitrogen utilization in alpine forages.For example,P.tenuiflora showed a much higher ability of absorbing nitrogen nutrition in a high salt environment and could be a more suitable herbage to be planted in saline-alkali soil in the Qinghai-Tibet Plateau as compared with E.nutans.
