An experiments were carried out with treatments differing in nitrogen supply （0, 5 and 15 g N/m^2） and CO2 levels （350 and 700 μmol/mol） using OTC （open top chamber） equipment to investigate the biomass of Cala...An experiments were carried out with treatments differing in nitrogen supply （0, 5 and 15 g N/m^2） and CO2 levels （350 and 700 μmol/mol） using OTC （open top chamber） equipment to investigate the biomass of Calamagrostis angustifolia and soil active carbon contents after two years. The results showed that elevated CO2 concentration increased the biomass of C. angustifolia and the magnitude of response varied with each growth period. Elevated CO2 concentration has increased aboveground biomass by 16.7% and 17.6% during the jointing and heading periods and only 3.5% and 9.4% during dough and maturity periods. The increases in belowground biomass due to CO2 elevation was 26.5%, 34.0% and 28.7% during the heading, dough and maturity periods, respectively. The responses of biomass to enhanced CO2 concentrations are differed in N levels. Both the increase of aboveground biomass and belowground biomass were greater under high level of N supply （15 g N/m^2）. Elevated CO2 concentration also increased the allocation of biomass and carbon in root. Under elevated CO2 concentration, the average values of active carbon tended to increase. The increases of soil active soil contents followed the sequence of microbial biomass carbon （10.6%） 〉 dissolved organic carbon （7.5%） 〉 labile oxidable carbon （6.6%） 〉 carbohydrate carbon （4.1%）. Stepwise regressions indicated there were significant correlations between the soil active carbon contents and plant biomass. Particularly, microbial biomass carbon, labile oxidable carbon and carbohydrate carbon were found to be correlated with belowground biomass, while dissolved organic carbon has correlation with aboveground biomass. Therefore, increased biomass was regarded as the main driving force for the increase in soil active organic carbon under elevated CO2 concentration.展开更多
The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil resp...The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil respiration during seedling growth of Pinus sylvestris vat. sylvestriformis. During the four growing seasons （May-October） from 1999 to 2003, the seedlings were exposed to elevated concentrations of CO2 in open-top chambers. The total soil respiration and contribution of root respiration were measured using an LI-6400-09 soil CO2 flux chamber on June 15 and October 8, 2003. To separate root respiration from total soil respiration, three PVC cylinders were inserted approximately 30 cm deep into the soil in each chamber. There were marked diurnal changes in air and soil temperatures on June 15. Both the total soil respiration and the soil respiration without roots showed a strong diurnal pattern, increasing from before sunrise to about 14：00 in the afternoon and then decreasing before the next sunrise. No increase in the mean total soil respiration and mean soil respiration with roots severed was observed under the elevated CO2 treatments on June 15, 2003, as compared to the open field and control chamber with ambient CO2. However, on October 8, 2003, the total soil respiration and soil respiration with roots severed in the open field were lower than those in the control and elevated CO2 chambers. The mean contribution of root respiration measured on June 15, 2003, ranged from 8.3% to 30.5% and on October 8, 2003, from 20.6% to 48.6%.展开更多
This paper studies the CO2 distribution of soil atmosphere in the Shilin National Park. The measurement sites were chosen according to different topographic features and different vegetations. Seven measurement sites ...This paper studies the CO2 distribution of soil atmosphere in the Shilin National Park. The measurement sites were chosen according to different topographic features and different vegetations. Seven measurement sites on 3 cross sections were chosen to pass through 3 karstic depressions or on the slopes of depressions. All measurement results show soils with pH values lower than 7.0 (from 5.4 to 6.6). There are 2 cases for the pH values of soil in different topographic features: the pH values of 2 profiles on the ridges or upper slopes of depressions are lower than those in the depressions; and the pH values of 2 soil profiles on the slopes of depressions are higher than those in the depressions. Most samples show relatively low humidity and CO2 contents on the ridges or slopes of depressions compared with soil profiles in the depressions. High CO2 contents occur at depths from ?40 to ?80 cm and high and dense grassland shows high CO2 contents in the soil atmosphere. Grass roots may grow and are distributed mainly at depths from ?20 to ?40 cm; while tree roots predominantly as deep as ?60 cm even ?80 cm. The influences of pine, cypress and eucalyptus on soil CO2 have been studied. Soil CO2 influenced by pine and cypress are generally concentrated in an area surrounding the tree with a diameter of 1 m and the strongly influenced distance is 50 cm. Eucalyptus will strongly affect the CO2 contents in an area with a diameter of 2 m, especially 1 m distant from the tree. The highest concentration of soil CO2 at a depth of ?30 and 100 cm from the tree reaches 92000 ppm.展开更多
Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture wh...Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture when the possible effects of elevated CO2 concentration on trees are assessed. In this study, we grew Cinnamomum camphora seedlings under two CO2 concentrations （350 μmol/mol and 500μmnol/mol） and three soil moisture levels [80%, 60% and 40% FWC （field water capacity）] to focus on the effects of exposure of trees to elevated CO2 on underground and aboveground plant growth, and its dependence on soil moisture. The results indicated that high CO2 concentration has no significant effects on shoot height but significantly impacts shoot weight and ratio of shoot weight to height under three soil moisture levels. The response of root growth to CO2 enrichment is just reversed, there are obvious effects on root length growth, but no effects on root weight growth and ratio of root weight to length. The CO2 enrichment decreased 20.42%, 32.78%, 20.59% of weight ratio of root to shoot under 40%, 60% and 80% FWC soil water conditions, respectively. And elevated CO2 concentration significantly increased the water content in aboveground and underground parts. Then we concluded that high CO2 concentration favours more tree aboveground biomass growth than underground biomass growth under favorable soil water conditions. And CO2 enrichment enhanced lateral growth of shoot and vertical growth of root. The responses of plants to elevated CO2 depend on soil water availability, and plants may benefit more from CO2 enrichment with sufficient water supply.展开更多
CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal...CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal variations of CO_(2) concentrations in deep loess, this paper takes Qingliangsi Gully watershed in northwestern Shanxi Province, China as an example to sys‐tematically study soil CO_(2)concentration and its spatio-temporal variations and carbon sink significance under different watershed locations and different land use types. Results show that: (1) The release potential of the loess soil is larger in the depth range of 2 m, which is much more likely to be the CO_(2) release area. (2) Grassland and forest are more advanta‐geous in terms of soil microbial activity and soil carbon reserve compared with farmland. In addition, the change of land use type from farmland to grassland can increase soil organic carbon reserve, which is of far-reaching significance to the global carbon cycle. This is especially true in an area like the Loess Plateau with densely covered hills, gullies, and serious soil erosion in an area of 64×104 km2. (3) In the study area, the diurnal concentration of soil CO_(2) at different depths shows a weak "high-low-high-low" trend from 08:00 to 07:00 next day;and in deep soil it has a lag time compared with the daily change of temperature, generally about 4−12 h, which may be caused largely by the more compact loess structure. It is worth pointing out that the Loess Plateau in China, with a thickness of the loess of tens to hundreds of meters, has the most abundant soil resources in the world, and also stores a large amount of terrestrial soil carbon, which carries the hope of promoting the research of global carbon cycle.展开更多
A study was conducted to determine the responses of soil enzymes （invertase, polyphenol oxidase, catalase, and dehydrogenase） to long-term CO2 enrichment at the Research Station of Changbai Mountain Forest Ecosystem...A study was conducted to determine the responses of soil enzymes （invertase, polyphenol oxidase, catalase, and dehydrogenase） to long-term CO2 enrichment at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences （42°24＇N, 128°28＇E; 738 m in elevation） in the northeast China during 1999-2006. Three treatments of the CO2 enrichment, designed as 500 μmol·mol-1 CO2 open-top chamber （OTC）, ambient control chamber and unchambered field （approx. 370 μmol·mol^-1CO2）, were conducted with Pinus koraiensis and Pinus sylvestriformis tree species. Soil sampling was made and analyzed separately in spring, summer and autumn in 2006 after the soil enzymes were exposed to elevated CO2 concentration （500 μmol·mol^-1） for eight growing seasons. Results showed that, at elevated CO2 concentration （500 μmol·mol^-1）, the activities of invertase （except for the summer samples of P. koraiensis） presented a remarkable decline in all growing seasons, while the activities of dehydrogenase had an increase but only part of the results was remarkable; the activities of polyphenol oxidase in P. sylvestriformis rhizosphere showed a remarkable decrease; the catalase activities increased in spring, while in turn were decline in other seasons. This study also revealed that the soil enzyme activities are significantly correlated with the tree species under the CO2 enhancement.展开更多
Diospyros texana (Texas persimmon) is a secondary species in most Juniperus ashei/Quercus fusiformis woodlands in central Texas. It has high density, but plants are mostly in the community understory. Light response c...Diospyros texana (Texas persimmon) is a secondary species in most Juniperus ashei/Quercus fusiformis woodlands in central Texas. It has high density, but plants are mostly in the community understory. Light response curves at ambient and elevated levels of CO<sub>2</sub> and temperature were measured for D. texana. The A<sub>net</sub> (photosynthetic rate) increased significantly as both light level and CO<sub>2</sub> levels increased but not temperature. The A<sub>max</sub> (maximum photosynthetic rate) of D. texana in full sun at elevated levels of CO<sub>2</sub> was increased for all treatments. Stomatal conductance increased with levels of CO<sub>2</sub> but only if the interaction was removed from the model. Intercellular levels of CO<sub>2</sub> increased with both temperature and CO<sub>2</sub> treatments as did water use efficiency (WUE). Furthermore, light saturation (L<sub>sat</sub>) increased with CO<sub>2</sub> treatments and light compensation (L<sub>cp</sub>) increased with temperature. The dark respiration (R<sub>d</sub>) increased with both temperature and CO<sub>2</sub> treatments. Markov population models suggested D. texana populations would remain ecologically similar in the future. However, sub-canopy light levels and herbivory should be considered when examining population projections. For example, Juniperus ashei juveniles are not recruited into any canopy unless there are high light levels. Herbivory reduces the success of Quercus juveniles from reaching the canopy. These factors do not seem to be a problem for D. texana juveniles which would allow them to reach the canopy without need of a high light gap and are not prevented by herbivory. Thus, Juniperus/Quercus woodlands will change in the future to woodlands with D. texana a more common species.展开更多
To improve the understanding of the CO_(2) exchange and the cycling of energy and water between the land surface and atmosphere over a typical hilly forest in southeastern China,a long-term field experimental observat...To improve the understanding of the CO_(2) exchange and the cycling of energy and water between the land surface and atmosphere over a typical hilly forest in southeastern China,a long-term field experimental observatory was established in Huainan,Anhui Province.Here,the authors briefly describe the three parts of ongoing research activities:the environmental monitoring at the site,the meteorological observations on a high tower,and particularly the intensive measurement of soil-vegetation-atmosphere interaction on a lower tower.Specifically,the diurnal variation of basic meteorological variables on a typical clear day(13 July 2018),and their temporal variation in the first three months of the low tower’s operation(4 June to 31 August 2018),and in combination with simultaneous data from the high tower,are analyzed.Results show that the data demonstrate reasonable variabilities,and the variables exhibit significant diurnal variation,characteristics of summer values,and considerable differences in summer months.The daily and monthly average albedos above the forest canopy were both 0.13.The daily average soil CO_(2) concentration was 1726 and 4481 ppm at 2 and 10 cm,respectively.The soil CO_(2) concentration changed with soil volumetric moisture contents,but showed a weak correlation with soil temperature in summer 2018.As the observatory continues to run and data continue to be collated,further investigation of the long-term variation of monsoon characteristics should be performed in the future.The experiment is useful in ecosystem and atmosphere interaction research,as well as for the development and evaluation of climate models,in the transitional climate zone of the Huaihe River basin.展开更多
基金supported by the Chinese Academy of Sciences (No KZCX2-YW-309)the National Basic Research Program (973) of China (No 2004CB418507)
文摘An experiments were carried out with treatments differing in nitrogen supply （0, 5 and 15 g N/m^2） and CO2 levels （350 and 700 μmol/mol） using OTC （open top chamber） equipment to investigate the biomass of Calamagrostis angustifolia and soil active carbon contents after two years. The results showed that elevated CO2 concentration increased the biomass of C. angustifolia and the magnitude of response varied with each growth period. Elevated CO2 concentration has increased aboveground biomass by 16.7% and 17.6% during the jointing and heading periods and only 3.5% and 9.4% during dough and maturity periods. The increases in belowground biomass due to CO2 elevation was 26.5%, 34.0% and 28.7% during the heading, dough and maturity periods, respectively. The responses of biomass to enhanced CO2 concentrations are differed in N levels. Both the increase of aboveground biomass and belowground biomass were greater under high level of N supply （15 g N/m^2）. Elevated CO2 concentration also increased the allocation of biomass and carbon in root. Under elevated CO2 concentration, the average values of active carbon tended to increase. The increases of soil active soil contents followed the sequence of microbial biomass carbon （10.6%） 〉 dissolved organic carbon （7.5%） 〉 labile oxidable carbon （6.6%） 〉 carbohydrate carbon （4.1%）. Stepwise regressions indicated there were significant correlations between the soil active carbon contents and plant biomass. Particularly, microbial biomass carbon, labile oxidable carbon and carbohydrate carbon were found to be correlated with belowground biomass, while dissolved organic carbon has correlation with aboveground biomass. Therefore, increased biomass was regarded as the main driving force for the increase in soil active organic carbon under elevated CO2 concentration.
基金Project supported by the Knowledge Innovation Project of the Chinese Academy of Sciences (No.KZCX2-YW-416)National NaturM Science Foundation of China (No.90411020)
文摘The objectives of this study were to investigate the effect of higher CO2 concentrations （500 and 700 μmol mol^-1） in atmosphere on total soil respiration and the contribution of root respiration to total soil respiration during seedling growth of Pinus sylvestris vat. sylvestriformis. During the four growing seasons （May-October） from 1999 to 2003, the seedlings were exposed to elevated concentrations of CO2 in open-top chambers. The total soil respiration and contribution of root respiration were measured using an LI-6400-09 soil CO2 flux chamber on June 15 and October 8, 2003. To separate root respiration from total soil respiration, three PVC cylinders were inserted approximately 30 cm deep into the soil in each chamber. There were marked diurnal changes in air and soil temperatures on June 15. Both the total soil respiration and the soil respiration without roots showed a strong diurnal pattern, increasing from before sunrise to about 14：00 in the afternoon and then decreasing before the next sunrise. No increase in the mean total soil respiration and mean soil respiration with roots severed was observed under the elevated CO2 treatments on June 15, 2003, as compared to the open field and control chamber with ambient CO2. However, on October 8, 2003, the total soil respiration and soil respiration with roots severed in the open field were lower than those in the control and elevated CO2 chambers. The mean contribution of root respiration measured on June 15, 2003, ranged from 8.3% to 30.5% and on October 8, 2003, from 20.6% to 48.6%.
基金granted by the National Natural Foundation of China(No.40071017)the Shilin Research Foundation of China(No.199903)
文摘This paper studies the CO2 distribution of soil atmosphere in the Shilin National Park. The measurement sites were chosen according to different topographic features and different vegetations. Seven measurement sites on 3 cross sections were chosen to pass through 3 karstic depressions or on the slopes of depressions. All measurement results show soils with pH values lower than 7.0 (from 5.4 to 6.6). There are 2 cases for the pH values of soil in different topographic features: the pH values of 2 profiles on the ridges or upper slopes of depressions are lower than those in the depressions; and the pH values of 2 soil profiles on the slopes of depressions are higher than those in the depressions. Most samples show relatively low humidity and CO2 contents on the ridges or slopes of depressions compared with soil profiles in the depressions. High CO2 contents occur at depths from ?40 to ?80 cm and high and dense grassland shows high CO2 contents in the soil atmosphere. Grass roots may grow and are distributed mainly at depths from ?20 to ?40 cm; while tree roots predominantly as deep as ?60 cm even ?80 cm. The influences of pine, cypress and eucalyptus on soil CO2 have been studied. Soil CO2 influenced by pine and cypress are generally concentrated in an area surrounding the tree with a diameter of 1 m and the strongly influenced distance is 50 cm. Eucalyptus will strongly affect the CO2 contents in an area with a diameter of 2 m, especially 1 m distant from the tree. The highest concentration of soil CO2 at a depth of ?30 and 100 cm from the tree reaches 92000 ppm.
基金Project supported by the National Natural Science Foundation of China (Nos. 30170161 and 90102015) and the Doctoral Disciplines Programs Foundation of Ministry of Education of China (No. 20030335043)
文摘Forest plays very important roles in global system with about 35% land area producing about 70% of total land net production. It is important to consider both elevated CO2 concentrations and different soil moisture when the possible effects of elevated CO2 concentration on trees are assessed. In this study, we grew Cinnamomum camphora seedlings under two CO2 concentrations （350 μmol/mol and 500μmnol/mol） and three soil moisture levels [80%, 60% and 40% FWC （field water capacity）] to focus on the effects of exposure of trees to elevated CO2 on underground and aboveground plant growth, and its dependence on soil moisture. The results indicated that high CO2 concentration has no significant effects on shoot height but significantly impacts shoot weight and ratio of shoot weight to height under three soil moisture levels. The response of root growth to CO2 enrichment is just reversed, there are obvious effects on root length growth, but no effects on root weight growth and ratio of root weight to length. The CO2 enrichment decreased 20.42%, 32.78%, 20.59% of weight ratio of root to shoot under 40%, 60% and 80% FWC soil water conditions, respectively. And elevated CO2 concentration significantly increased the water content in aboveground and underground parts. Then we concluded that high CO2 concentration favours more tree aboveground biomass growth than underground biomass growth under favorable soil water conditions. And CO2 enrichment enhanced lateral growth of shoot and vertical growth of root. The responses of plants to elevated CO2 depend on soil water availability, and plants may benefit more from CO2 enrichment with sufficient water supply.
基金supported by the National Natural Science Foundation, Grant No. 41671213the Fundamental Research Funds for the Central Universities, No. GK201803055Shaanxi prov‐ince Postdoctoral Science Foundation No. 2016 BSHEDZZ27.
文摘CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal variations of CO_(2) concentrations in deep loess, this paper takes Qingliangsi Gully watershed in northwestern Shanxi Province, China as an example to sys‐tematically study soil CO_(2)concentration and its spatio-temporal variations and carbon sink significance under different watershed locations and different land use types. Results show that: (1) The release potential of the loess soil is larger in the depth range of 2 m, which is much more likely to be the CO_(2) release area. (2) Grassland and forest are more advanta‐geous in terms of soil microbial activity and soil carbon reserve compared with farmland. In addition, the change of land use type from farmland to grassland can increase soil organic carbon reserve, which is of far-reaching significance to the global carbon cycle. This is especially true in an area like the Loess Plateau with densely covered hills, gullies, and serious soil erosion in an area of 64×104 km2. (3) In the study area, the diurnal concentration of soil CO_(2) at different depths shows a weak "high-low-high-low" trend from 08:00 to 07:00 next day;and in deep soil it has a lag time compared with the daily change of temperature, generally about 4−12 h, which may be caused largely by the more compact loess structure. It is worth pointing out that the Loess Plateau in China, with a thickness of the loess of tens to hundreds of meters, has the most abundant soil resources in the world, and also stores a large amount of terrestrial soil carbon, which carries the hope of promoting the research of global carbon cycle.
基金This research was supported by National Basic Research Program of China (No.2002CB412502)Project of Key Pro-gram of the National Science Foundation of China (No.90411020)Natural Science Foundation of China (No.30400051)
文摘A study was conducted to determine the responses of soil enzymes （invertase, polyphenol oxidase, catalase, and dehydrogenase） to long-term CO2 enrichment at the Research Station of Changbai Mountain Forest Ecosystems, Chinese Academy of Sciences （42°24＇N, 128°28＇E; 738 m in elevation） in the northeast China during 1999-2006. Three treatments of the CO2 enrichment, designed as 500 μmol·mol-1 CO2 open-top chamber （OTC）, ambient control chamber and unchambered field （approx. 370 μmol·mol^-1CO2）, were conducted with Pinus koraiensis and Pinus sylvestriformis tree species. Soil sampling was made and analyzed separately in spring, summer and autumn in 2006 after the soil enzymes were exposed to elevated CO2 concentration （500 μmol·mol^-1） for eight growing seasons. Results showed that, at elevated CO2 concentration （500 μmol·mol^-1）, the activities of invertase （except for the summer samples of P. koraiensis） presented a remarkable decline in all growing seasons, while the activities of dehydrogenase had an increase but only part of the results was remarkable; the activities of polyphenol oxidase in P. sylvestriformis rhizosphere showed a remarkable decrease; the catalase activities increased in spring, while in turn were decline in other seasons. This study also revealed that the soil enzyme activities are significantly correlated with the tree species under the CO2 enhancement.
文摘Diospyros texana (Texas persimmon) is a secondary species in most Juniperus ashei/Quercus fusiformis woodlands in central Texas. It has high density, but plants are mostly in the community understory. Light response curves at ambient and elevated levels of CO<sub>2</sub> and temperature were measured for D. texana. The A<sub>net</sub> (photosynthetic rate) increased significantly as both light level and CO<sub>2</sub> levels increased but not temperature. The A<sub>max</sub> (maximum photosynthetic rate) of D. texana in full sun at elevated levels of CO<sub>2</sub> was increased for all treatments. Stomatal conductance increased with levels of CO<sub>2</sub> but only if the interaction was removed from the model. Intercellular levels of CO<sub>2</sub> increased with both temperature and CO<sub>2</sub> treatments as did water use efficiency (WUE). Furthermore, light saturation (L<sub>sat</sub>) increased with CO<sub>2</sub> treatments and light compensation (L<sub>cp</sub>) increased with temperature. The dark respiration (R<sub>d</sub>) increased with both temperature and CO<sub>2</sub> treatments. Markov population models suggested D. texana populations would remain ecologically similar in the future. However, sub-canopy light levels and herbivory should be considered when examining population projections. For example, Juniperus ashei juveniles are not recruited into any canopy unless there are high light levels. Herbivory reduces the success of Quercus juveniles from reaching the canopy. These factors do not seem to be a problem for D. texana juveniles which would allow them to reach the canopy without need of a high light gap and are not prevented by herbivory. Thus, Juniperus/Quercus woodlands will change in the future to woodlands with D. texana a more common species.
基金supported by the National Natural Science Foundation of China[grant number 41575092]the National Key Research and Development Program[grant number 2018YFC1506600]。
文摘To improve the understanding of the CO_(2) exchange and the cycling of energy and water between the land surface and atmosphere over a typical hilly forest in southeastern China,a long-term field experimental observatory was established in Huainan,Anhui Province.Here,the authors briefly describe the three parts of ongoing research activities:the environmental monitoring at the site,the meteorological observations on a high tower,and particularly the intensive measurement of soil-vegetation-atmosphere interaction on a lower tower.Specifically,the diurnal variation of basic meteorological variables on a typical clear day(13 July 2018),and their temporal variation in the first three months of the low tower’s operation(4 June to 31 August 2018),and in combination with simultaneous data from the high tower,are analyzed.Results show that the data demonstrate reasonable variabilities,and the variables exhibit significant diurnal variation,characteristics of summer values,and considerable differences in summer months.The daily and monthly average albedos above the forest canopy were both 0.13.The daily average soil CO_(2) concentration was 1726 and 4481 ppm at 2 and 10 cm,respectively.The soil CO_(2) concentration changed with soil volumetric moisture contents,but showed a weak correlation with soil temperature in summer 2018.As the observatory continues to run and data continue to be collated,further investigation of the long-term variation of monsoon characteristics should be performed in the future.The experiment is useful in ecosystem and atmosphere interaction research,as well as for the development and evaluation of climate models,in the transitional climate zone of the Huaihe River basin.
