The impacts of different 03 concentration on the biomass and yield of rice were studied by using OTC-1 open-top chambers. Experimental treatments included the activated charcoal-filtered air. (CFA), 50 nl/L (CF50), 10...The impacts of different 03 concentration on the biomass and yield of rice were studied by using OTC-1 open-top chambers. Experimental treatments included the activated charcoal-filtered air. (CFA), 50 nl/L (CF50), 100 nl/L ( CF100) and 200 nl/L (CF200) concentrations of O-3. The O-3 treatments significantly decreased the total biomass per plant. The. elevated O-3 exposure resulted in a more decrease in the root growth than in the shoot growth. Assessments of yield characteristics at the final harvest revealed an O-3-induced decrease in the number of grains per plant, resulting from fewer ears per plant, fewer grains per ear and more unfilled grains per ear. The 1000 grain dry weight and the harvest index (HI) were not changed significantly under 50 nl/L or 100 nl/L O-3 exposure, but reduced by 17.0% and 4.8% by 200nl/L O-3 treatment, respectively. Compared to the CFA treatment, CF50, CF100 and CF200 treatments caused a 8.2%, 26.1%, 49.1% decrease of the grain yield per plant, and a 14.2%, 31.7%, 51.7% decrease of the total biomass per plant, respectively. Linear regression showed that the 7h - daily mean O-3 concentration exposure for 3 months ( July-September) and AOT40 ( cunulative exposure accumulation over threshold 40 nl/L) were well correlated with the relative grain yield. A yield loss of 10% was estimated to be at 46.9 nl/L O-3 for 7h-daily mean O-3 concentration exposure or at 12930nl/(L(.)h) O-3 for AOT40.展开更多
Predicting how human activity will influence the response of alpine grasslands to future warming has many uncertainties.In this study, a field experiment with controlled warming and clipping was conducted in an alpine...Predicting how human activity will influence the response of alpine grasslands to future warming has many uncertainties.In this study, a field experiment with controlled warming and clipping was conducted in an alpine meadow at three elevations（4313 m, 4513 m and 4693 m） in Northern Tibet to test the hypothesis that clipping would alter warming effect on biomass production.Open top chambers（OTCs） were used to increase temperature since July,2008 and the OTCs increased air temperature by approximately 0.9o C ~ 1.8o C during the growing in2012.Clipping was conducted three times one year during growing season and the aboveground parts of all live plants were clipped to approximately 0.01 m in height using scissors since 2009.Gross primary production（GPP） was calculated from the Moderate-Resolution Imaging Spectroradiometer GPP algorithm and aboveground plant production was estimated using the surface-measured normalized difference vegetation index in 2012.Warming decreased the GPP, aboveground biomass（AGB） and aboveground net primary production（ANPP） at all three elevations when clipping was not applied.In contrast, warming increased AGB at all three elevations, GPP at the two lower elevations and ANPP at the two higher elevations when clipping was applied.These findings show that clipping reduced the negative effect of warming on GPP, AGB and ANPP, suggesting that clipping may reduce the effect of climate warming on GPP, AGB and ANPP in alpine meadows on the Tibetan Plateau, and therefore, may be a viable strategy for mitigating the effects of climate change on grazing and animal husbandry on the Tibetan Plateau.展开更多
Biomass is an important component of global carbon cycling and is vulnerable to climate change. Previous studies have mainly focused on the responses of aboveground biomass and phenology to warming, while studies of r...Biomass is an important component of global carbon cycling and is vulnerable to climate change. Previous studies have mainly focused on the responses of aboveground biomass and phenology to warming, while studies of root architecture and of root biomass allocation between coarse and fine roots have been scarcely reported in grassland ecosystems. We conducted an open-top-chamber warming experiment to investigate the effect of potential warming on root biomass and root allocation in alpine steppe on the north Tibetan Plateau. The results showed that Stipa purpurea had significantly higher total root length, root surface area and tips than Carex moocroftii. However,there were no differences in total root volume, mean diameter and forks for the two species. Warming significantly increased total root biomass(27.60%), root biomass at 0–10 cm depth(27.84%) and coarse root biomass(diameter > 0.20 mm, 57.68%) in the growing season(August). However, warming had no significant influence on root biomass in the non-growing season(April). Root biomass showed clear seasonalvariations: total root biomass, root biomass at 0–10 cm depth and coarse root biomass significantly increased in the growing season. The increase in total root biomass was due to the enhancement of root biomass at 0–10 cm depth, to which the increase of coarse root biomass made a great contribution. This research is of significance for understanding biomass allocation, carbon cycling and biological adaptability in alpine grassland ecosystems under future climate change.展开更多
A field study was carried out to quantify plant growth and the foliar chemistry of transgenic Bacillus thuringiensis （Bt） cotton （cv. GK-12） exposed to ambient CO2 and elevated （double-ambient） CO2 for different...A field study was carried out to quantify plant growth and the foliar chemistry of transgenic Bacillus thuringiensis （Bt） cotton （cv. GK-12） exposed to ambient CO2 and elevated （double-ambient） CO2 for different lengths of time （1, 2 and 3 months） in 2004 and 2005. The results indicated that CO2 levels significantly affected plant height, leaf area per plant and leaf chemistry of transgenic Bt cotton. Significantly, higher plant height and leaf area per plant were observed after cotton plants that were grown in elevated CO2 were compared with plants grown in ambient CO2 for 1, 2 and 3 months in the investigation. Simultaneously, significant interaction between CO2 level x investigating year was observed in leaf area per plant. Moreover, foliar total amino acids were increased by 14%, 13%, 11% and 12%, 14%, 10% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 in 2004 and 2005, respectively. Condensed tannin occurrence increased by 17%, 11%, 9% in 2004 and 12%, 11%, 9% in 2005 in transgenic Bt cotton after being exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 for the same time. However, Bt toxin decreased by 3.0%, 2.9%, 3.1% and 2.4%, 2.5%, 2.9% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3months compared with ambient CO2 for same time in 2004 and 2005, respectively. Furthermore, there was prominent interaction on the foliar total amino acids between the CO2 level and the time of cotton plant being exposed to elevated CO2. It is presumed that elevated CO2 can alter the plant growth and hence ultimately the phenotype allocation to foliar chemistical components of transgenic Bt cotton, which may in turn, affect the plant-herbivore interactions.展开更多
In order to explore the response of soil respiration in grassland to global warming,we carried out a warming experiment with open top chambers(OTCs)in the subalpine meadow,Mount Wutai in north China.Our results showed...In order to explore the response of soil respiration in grassland to global warming,we carried out a warming experiment with open top chambers(OTCs)in the subalpine meadow,Mount Wutai in north China.Our results showed in the subalpine meadow across 2500-2700 m above the sea level(ASL),with OTCs,soil respiration increased by 2.00μmol·m^(-2)·s^(-1)as soil temperature increased by 1.25℃on average.Warming decreased soil moisture over the experiment periods except in October 2019 when snow melted in OTCs.Warming effect on soil respiration peaked at 178.31%in October 2019.In control and warming treatment,based on exponential regression equations,soil temperature alone accounted for 85.3%and 61.2%of soil respiration variation,respectively.In control treatment soil moisture alone explained 23.2%of soil respiration variation based on the power regression equation while in warming treatment they were not significantly correlated with each other.The response of soil respiration to warming relied on altitudes as well as the time of the year,but was not inhibited by soil moisture,labile carbon pool,and available nitrogen.We concluded soil temperature was the main factor influencing soil respiration,and global warming would stimulate soil respiration in the subalpine meadows of Mount Wutai in the future.Our analysis provided new data on characteristics and mechanisms of the response of soil respiration to warming,and helped to further understand the relationship between carbon cycle and climate change.展开更多
Aims Alpine ecosystems may experience larger temperature increases due to global warming as compared with lowland ecosystems.Information on physiological adjustment of alpine plants to temperature changes can provide ...Aims Alpine ecosystems may experience larger temperature increases due to global warming as compared with lowland ecosystems.Information on physiological adjustment of alpine plants to temperature changes can provide insights into our understanding how these plants are responding to current and future warming.We tested the hypothesis that alpine plants would exhibit acclimation in photosynthesis and respiration under long-term elevated temperature,and the acclimation may relatively increase leaf carbon gain under warming conditions.Methods Open-top chambers(OTCs)were set up for a period of 11 years to artificially increase the temperature in an alpine meadow ecosystem.We measured leaf photosynthesis and dark respiration under different light,temperature and ambient CO_(2)concentrations for Gentiana straminea,a species widely distributed on the Tibetan Plateau.Maximum rates of the photosynthetic electron transport(J_(max)),RuBP carboxylation(V_(cmax))and temperature sensitivity of respiration Q10 were obtained from the measurements.We further estimated the leaf carbon budget of G.straminea using the physiological parameters and environmental variables obtained in the study.Important findings 1)The OTCs consistently elevated the daily mean air temperature by;1.6℃and soil temperature by;0.5℃during the growing season.2)Despite the small difference in the temperature environment,there was strong tendency in the temperature acclimation of photosynthesis.The estimated temperature optimum of light-saturated photosynthetic CO_(2)uptake(A_(max))shifted;1℃higher from the plants under the ambient regime to those under the OTCs warming regime,and the Amax was significantly lower in the warming-acclimated leaves than the leaves outside the OTCs.3)Temperature acclimation of respiration was large and significant:the dark respiration rates of leaves developed in the warming regime were significantly lower than leaves from the ambient environments.4)The simulated net leaf carbon gain was significantly lower in the in situ le展开更多
Canola plants were fumigated in open-top chambers with ozone（O3）（120 ppb）under well-watered（WW）and water-stressed（WS）conditions for 4 weeks.Non-fumigated plants were also studied to facilitate comparison betwe...Canola plants were fumigated in open-top chambers with ozone（O3）（120 ppb）under well-watered（WW）and water-stressed（WS）conditions for 4 weeks.Non-fumigated plants were also studied to facilitate comparison between treatments for the same week and over time.Therefore,the treatments were：WW,WW-O3,WS and WS-O3.The fast chlorophyll a fluorescence transients OJIP for the four treatments emitted upon illumination of dark-adapted leaves were measured after week 1,2,3,4 and analysed by the JIP-test to evaluate the resulting changes in photosynthetic performance.Ozone fumigation led to a decline of total performance index（PI（total））in well-watered plants.The effect of O3 was minor under drought conditions,as revealed by a decrease of PI（total） by 3%.The PI（total） decreased as the treatment was prolonged,due to leaf ageing for all cases and the decline was more pronounced under WW-O3.Taking the average of all weeks,WW had the highest PI（total)and the lowest WW-O3（decrease by 27%）,while in WS and WS-O3,it was lower than WW（14 and 17%,respectively）.We found that the absorption（ABS）/reaction centre（RC）increases,while the maximum quantum yield of primary photochemistry（φ（Po））undergoes slight changes,and trapping（TR0）/RC closely followed the increase in ABS/RC.This indicates that O3and drought caused an increase in the functional antenna size.The maximum quantum yield of primary photochemistry showed slight differences for all treatments and over time,suggesting that this parameter is less sensitive to drought and O3 stress.Therefore,the more sensitive components of the photosynthetic electron transport chain appeared to be the probability that an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side（δ（Ro））and the RC density on a chlorophyll basis（RC/ABS）.展开更多
In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ i...In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.展开更多
Passive-warming, open-top chambers(OTCs) are widely applied for studying the effects of future climate warming on coastal wetlands. In this study, a set of six OTCs were established at a Phragmites wetland located in ...Passive-warming, open-top chambers(OTCs) are widely applied for studying the effects of future climate warming on coastal wetlands. In this study, a set of six OTCs were established at a Phragmites wetland located in the Yellow River Delta of Dongying City, China. With data collected through online transmission and in-situ sensors, the attributes and patterns of realized OTCs warming are demonstrated.The authors also quantified the preliminary influence of experimental chamber warming on plant traits.OTCs produced an elevated average air temperature of 0.8°C(relative to controls) during the growing season(June to October) of 2018, and soil temperatures actually decreased by 0.54°C at a depth of 5 cm and 0.46°C at a depth of 30 cm in the OTCs. Variations in diel patterns of warming depend greatly on the heat sources of incoming radiation in the daytime versus soil heat flux at night. Warming effects were often larger during instantaneous analyses and influenced OTCs air temperatures from-2.5°C to 8.3°C dependent on various meteorological conditions at any given time, ranging from cooling influences from vertical heat exchange and vegetation to radiation-associated warming. Night-time temperature depressions in the OTCs were due to the low turbulence inside OTCs and changes in surface soilatmosphere heat transfer. Plant shoot density, basal diameter, and biomass of Phragmites decreased by23.2%, 6.3%, and 34.0%, respectively, under experimental warming versus controls, and plant height increased by 4.3%, reflecting less carbon allocation to stem structures as plants in the OTCs experienced simultaneous wind buffering. While these passive-warming OTCs created the desired warming effects both to the atmosphere and soils, pest damages on the plant leaves and lodging within the OTCs were extensive and serious, creating the need to consider control options for these chambers and the replicated OTCs studies underway in other Chinese Phragmites marshes(Panjin and Yancheng).展开更多
Aims Relatively few studies so far have assessed how ongoing global warming will affect the photosynthetic performance of dryland plant species.We evaluated the effects of warming on the photosynthetic rates of 10 spe...Aims Relatively few studies so far have assessed how ongoing global warming will affect the photosynthetic performance of dryland plant species.We evaluated the effects of warming on the photosynthetic rates of 10 species with contrasting functional attributes,and whether their functional traits modulated photosynthetic responses to warming.Methods A common garden experiment was conducted over 2 years with distinct environmental conditions(drier vs.wetter year).The experiment was designed as a randomized block design with two treatments:warming(control vs.~2.9℃ temperature increase)and species(Agropyron cristatum,Festuca ovina,Lygeum spartum,Medicago sativa,Plantago lanceolata,Psoralea bituminosa,Sanguisorba minor,Hedysarum coronarium,Dorycnium pentaphyllum and Phlomis herba-venti).We linked functional traits measurements with temporal variations in photosynthetic responses to warming.Important Findings In the drier year,warming increased photosynthetic rates at the beginning of the growing season,suggesting a modification in the growing period(earlier spring).In the wetter year,functional traits modulated photosynthetic responses to warming.Larger species with shorter leaves(e.g.M.sativa)had higher photosynthetic rates under warming compared to smaller species with larger leaves(e.g.F.ovina).Our results highlight the importance of(i)studying photosynthetic responses along different years and(ii)considering functional traits when evaluating photosynthetic responses to climate change,particularly in stressful environments such as drylands.展开更多
Background:Elevated atmospheric CO_(2) has direct and indirect influences on ecosystem processes.The impact of elevated atmospheric CO_(2) concentration on carbon and nitrogen transformations,together with the microbi...Background:Elevated atmospheric CO_(2) has direct and indirect influences on ecosystem processes.The impact of elevated atmospheric CO_(2) concentration on carbon and nitrogen transformations,together with the microbial community,was evaluated with water hyacinth(Eichhornia crassipes)in an open-top chamber replicated wetland.The responses of nitrogen and carbon pools in water and wetland soil,and microbial community abundance were studied under ambient CO_(2) and elevated CO_(2)(ambient+200μL L^(−1)).Results:Total biomass for the whole plant under elevated CO_(2) increased by an average of 8%(p=0.022).Wetlands,with water hyacinth,showed a significant increase in total carbon and total organic carbon in water by 7%(p=0.001)and 21%(p=0.001),respectively,under elevated CO_(2) compared to that of ambient CO_(2).Increase in dissolved carbon in water correlates with the presence of wetland plants since the water hyacinth can directly exchange CO_(2) from the atmosphere to water by the upper epidermis of leaves.Also,the enrichment CO_(2) showed an increase in total carbon and total organic carbon concentration in wetland soil by 3%(p=0.344)and 6%(p=0.008),respectively.The total nitrogen content in water increased by 26%(p=0.0001),while total nitrogen in wetland soil pool under CO_(2) enrichment decreased by 9%(p=0.011)due to increased soil microbial community abundance,extracted by phospholipid fatty acids,which was 25%larger in amount than that of the ambient treatment.Conclusion:The study revealed that the elevated CO_(2) would affect the carbon and nitrogen transformations in wetland plant,water,and soil pool and increase soil microbial community abundance.展开更多
Low temperature is an important limiting factor for alpine ecosystems on the Tibetan Plateau. This study is based on data from on-site experimental warming platforms(open top chambers, OTC) at three elevations(4300 m,...Low temperature is an important limiting factor for alpine ecosystems on the Tibetan Plateau. This study is based on data from on-site experimental warming platforms(open top chambers, OTC) at three elevations(4300 m, 4500 m, 4700 m) on the Qinghai-Tibet Plateau. The carbon and nitrogen stoichiometry characteristics of plant communities, both above-ground and below-ground, were observed in three alpine meadow ecosystems in August and September of 2011 and August of 2012. Experimental warming significantly increased above-ground nitrogen content by 21.4% in September 2011 at 4500 m, and reduced above-ground carbon content by 3.9% in August 2012 at 4300 m. Experimental warming significantly increased below-ground carbon content by 5.5% in August 2011 at 4500 m, and the below-ground ratio of carbon to nitrogen by 28.0% in September 2011 at 4300 m, but reduced below-ground nitrogen content by 15.7% in September 2011 at 4700 m, below-ground carbon content by 34.3% in August 2012 at 4700 m, and the below-ground ratio of carbon to nitrogen by 37.9% in August 2012 at 4700 m. Experimental warming had no significant effect on the characteristics of community carbon and nitrogen stoichiometry under other conditions. Therefore, experimental warming had inconsistent effects on the carbon and nitrogen stoichiometry of plant communities at different elevations and during different months. Soil ammonium nitrogen and nitrate nitrogen content were the main factors affecting plant community carbon and nitrogen stoichiometry.展开更多
文摘The impacts of different 03 concentration on the biomass and yield of rice were studied by using OTC-1 open-top chambers. Experimental treatments included the activated charcoal-filtered air. (CFA), 50 nl/L (CF50), 100 nl/L ( CF100) and 200 nl/L (CF200) concentrations of O-3. The O-3 treatments significantly decreased the total biomass per plant. The. elevated O-3 exposure resulted in a more decrease in the root growth than in the shoot growth. Assessments of yield characteristics at the final harvest revealed an O-3-induced decrease in the number of grains per plant, resulting from fewer ears per plant, fewer grains per ear and more unfilled grains per ear. The 1000 grain dry weight and the harvest index (HI) were not changed significantly under 50 nl/L or 100 nl/L O-3 exposure, but reduced by 17.0% and 4.8% by 200nl/L O-3 treatment, respectively. Compared to the CFA treatment, CF50, CF100 and CF200 treatments caused a 8.2%, 26.1%, 49.1% decrease of the grain yield per plant, and a 14.2%, 31.7%, 51.7% decrease of the total biomass per plant, respectively. Linear regression showed that the 7h - daily mean O-3 concentration exposure for 3 months ( July-September) and AOT40 ( cunulative exposure accumulation over threshold 40 nl/L) were well correlated with the relative grain yield. A yield loss of 10% was estimated to be at 46.9 nl/L O-3 for 7h-daily mean O-3 concentration exposure or at 12930nl/(L(.)h) O-3 for AOT40.
基金funded by the National Natural Science Foundation of China(Grant No.41171084)the Natural Science Foundation of Tibet Autonomous Region(Response of species richness and aboveground biomass to warming in the alpine meadows of Tibet)
文摘Predicting how human activity will influence the response of alpine grasslands to future warming has many uncertainties.In this study, a field experiment with controlled warming and clipping was conducted in an alpine meadow at three elevations（4313 m, 4513 m and 4693 m） in Northern Tibet to test the hypothesis that clipping would alter warming effect on biomass production.Open top chambers（OTCs） were used to increase temperature since July,2008 and the OTCs increased air temperature by approximately 0.9o C ~ 1.8o C during the growing in2012.Clipping was conducted three times one year during growing season and the aboveground parts of all live plants were clipped to approximately 0.01 m in height using scissors since 2009.Gross primary production（GPP） was calculated from the Moderate-Resolution Imaging Spectroradiometer GPP algorithm and aboveground plant production was estimated using the surface-measured normalized difference vegetation index in 2012.Warming decreased the GPP, aboveground biomass（AGB） and aboveground net primary production（ANPP） at all three elevations when clipping was not applied.In contrast, warming increased AGB at all three elevations, GPP at the two lower elevations and ANPP at the two higher elevations when clipping was applied.These findings show that clipping reduced the negative effect of warming on GPP, AGB and ANPP, suggesting that clipping may reduce the effect of climate warming on GPP, AGB and ANPP in alpine meadows on the Tibetan Plateau, and therefore, may be a viable strategy for mitigating the effects of climate change on grazing and animal husbandry on the Tibetan Plateau.
基金supported by the National Natural Science Foundation of China (41571205)the Strategic Pilot Science and Technology Projects of Chinese Academy of Sciences (Grant No. XDB03030505, XDA05050506)
文摘Biomass is an important component of global carbon cycling and is vulnerable to climate change. Previous studies have mainly focused on the responses of aboveground biomass and phenology to warming, while studies of root architecture and of root biomass allocation between coarse and fine roots have been scarcely reported in grassland ecosystems. We conducted an open-top-chamber warming experiment to investigate the effect of potential warming on root biomass and root allocation in alpine steppe on the north Tibetan Plateau. The results showed that Stipa purpurea had significantly higher total root length, root surface area and tips than Carex moocroftii. However,there were no differences in total root volume, mean diameter and forks for the two species. Warming significantly increased total root biomass(27.60%), root biomass at 0–10 cm depth(27.84%) and coarse root biomass(diameter > 0.20 mm, 57.68%) in the growing season(August). However, warming had no significant influence on root biomass in the non-growing season(April). Root biomass showed clear seasonalvariations: total root biomass, root biomass at 0–10 cm depth and coarse root biomass significantly increased in the growing season. The increase in total root biomass was due to the enhancement of root biomass at 0–10 cm depth, to which the increase of coarse root biomass made a great contribution. This research is of significance for understanding biomass allocation, carbon cycling and biological adaptability in alpine grassland ecosystems under future climate change.
基金Supported by the State Key Basic Research and Development Plan of China （2006CB102002）the Innovation Program of the Chinese Academy of Sciences （KSCX2-YW-N-006）+1 种基金the National Natural Science Foundation of China （30571253 and 30621003） the Exoteric Foundation from the National Key Laboratory of Integrated Management of Pest Insects and Rodents （Chinese-IPM-0601）.
文摘A field study was carried out to quantify plant growth and the foliar chemistry of transgenic Bacillus thuringiensis （Bt） cotton （cv. GK-12） exposed to ambient CO2 and elevated （double-ambient） CO2 for different lengths of time （1, 2 and 3 months） in 2004 and 2005. The results indicated that CO2 levels significantly affected plant height, leaf area per plant and leaf chemistry of transgenic Bt cotton. Significantly, higher plant height and leaf area per plant were observed after cotton plants that were grown in elevated CO2 were compared with plants grown in ambient CO2 for 1, 2 and 3 months in the investigation. Simultaneously, significant interaction between CO2 level x investigating year was observed in leaf area per plant. Moreover, foliar total amino acids were increased by 14%, 13%, 11% and 12%, 14%, 10% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 in 2004 and 2005, respectively. Condensed tannin occurrence increased by 17%, 11%, 9% in 2004 and 12%, 11%, 9% in 2005 in transgenic Bt cotton after being exposed to elevated CO2 for 1, 2 or 3 months compared with ambient CO2 for the same time. However, Bt toxin decreased by 3.0%, 2.9%, 3.1% and 2.4%, 2.5%, 2.9% in transgenic Bt cotton after exposed to elevated CO2 for 1, 2 or 3months compared with ambient CO2 for same time in 2004 and 2005, respectively. Furthermore, there was prominent interaction on the foliar total amino acids between the CO2 level and the time of cotton plant being exposed to elevated CO2. It is presumed that elevated CO2 can alter the plant growth and hence ultimately the phenotype allocation to foliar chemistical components of transgenic Bt cotton, which may in turn, affect the plant-herbivore interactions.
基金Supported by Xinzhou Teachers University Project(2018KY02)Shanxi Province Colleges/Universities Discipline Group Construction Plan Project for Service and Industry Innovation"Ecology and Cultural Tourism Discipline Group for Mount Wutai"Program for the Philosophy and Social Sciences Research of Higher Learning Institutions of Shanxi(20210122)。
文摘In order to explore the response of soil respiration in grassland to global warming,we carried out a warming experiment with open top chambers(OTCs)in the subalpine meadow,Mount Wutai in north China.Our results showed in the subalpine meadow across 2500-2700 m above the sea level(ASL),with OTCs,soil respiration increased by 2.00μmol·m^(-2)·s^(-1)as soil temperature increased by 1.25℃on average.Warming decreased soil moisture over the experiment periods except in October 2019 when snow melted in OTCs.Warming effect on soil respiration peaked at 178.31%in October 2019.In control and warming treatment,based on exponential regression equations,soil temperature alone accounted for 85.3%and 61.2%of soil respiration variation,respectively.In control treatment soil moisture alone explained 23.2%of soil respiration variation based on the power regression equation while in warming treatment they were not significantly correlated with each other.The response of soil respiration to warming relied on altitudes as well as the time of the year,but was not inhibited by soil moisture,labile carbon pool,and available nitrogen.We concluded soil temperature was the main factor influencing soil respiration,and global warming would stimulate soil respiration in the subalpine meadows of Mount Wutai in the future.Our analysis provided new data on characteristics and mechanisms of the response of soil respiration to warming,and helped to further understand the relationship between carbon cycle and climate change.
基金Global environment research coordination systemMinistry of the Environment,Japan,to the project‘Early detection and prediction of climate warming based on long-term monitoring on the Tibetan Plateau’by a study of‘Model development for evaluating and predicting of global warming impacts using indicator species’from the Sumitomo Foundation.
文摘Aims Alpine ecosystems may experience larger temperature increases due to global warming as compared with lowland ecosystems.Information on physiological adjustment of alpine plants to temperature changes can provide insights into our understanding how these plants are responding to current and future warming.We tested the hypothesis that alpine plants would exhibit acclimation in photosynthesis and respiration under long-term elevated temperature,and the acclimation may relatively increase leaf carbon gain under warming conditions.Methods Open-top chambers(OTCs)were set up for a period of 11 years to artificially increase the temperature in an alpine meadow ecosystem.We measured leaf photosynthesis and dark respiration under different light,temperature and ambient CO_(2)concentrations for Gentiana straminea,a species widely distributed on the Tibetan Plateau.Maximum rates of the photosynthetic electron transport(J_(max)),RuBP carboxylation(V_(cmax))and temperature sensitivity of respiration Q10 were obtained from the measurements.We further estimated the leaf carbon budget of G.straminea using the physiological parameters and environmental variables obtained in the study.Important findings 1)The OTCs consistently elevated the daily mean air temperature by;1.6℃and soil temperature by;0.5℃during the growing season.2)Despite the small difference in the temperature environment,there was strong tendency in the temperature acclimation of photosynthesis.The estimated temperature optimum of light-saturated photosynthetic CO_(2)uptake(A_(max))shifted;1℃higher from the plants under the ambient regime to those under the OTCs warming regime,and the Amax was significantly lower in the warming-acclimated leaves than the leaves outside the OTCs.3)Temperature acclimation of respiration was large and significant:the dark respiration rates of leaves developed in the warming regime were significantly lower than leaves from the ambient environments.4)The simulated net leaf carbon gain was significantly lower in the in situ le
基金supported by the Cuomo Foundation through the partnership with the Intergovernmental Panel on Climate Change (IPCC) Scholarship Programmeby the Applied Centre for Climate and Earth Systems Science (ACCESS), South Africa
文摘Canola plants were fumigated in open-top chambers with ozone（O3）（120 ppb）under well-watered（WW）and water-stressed（WS）conditions for 4 weeks.Non-fumigated plants were also studied to facilitate comparison between treatments for the same week and over time.Therefore,the treatments were：WW,WW-O3,WS and WS-O3.The fast chlorophyll a fluorescence transients OJIP for the four treatments emitted upon illumination of dark-adapted leaves were measured after week 1,2,3,4 and analysed by the JIP-test to evaluate the resulting changes in photosynthetic performance.Ozone fumigation led to a decline of total performance index（PI（total））in well-watered plants.The effect of O3 was minor under drought conditions,as revealed by a decrease of PI（total） by 3%.The PI（total） decreased as the treatment was prolonged,due to leaf ageing for all cases and the decline was more pronounced under WW-O3.Taking the average of all weeks,WW had the highest PI（total)and the lowest WW-O3（decrease by 27%）,while in WS and WS-O3,it was lower than WW（14 and 17%,respectively）.We found that the absorption（ABS）/reaction centre（RC）increases,while the maximum quantum yield of primary photochemistry（φ（Po））undergoes slight changes,and trapping（TR0）/RC closely followed the increase in ABS/RC.This indicates that O3and drought caused an increase in the functional antenna size.The maximum quantum yield of primary photochemistry showed slight differences for all treatments and over time,suggesting that this parameter is less sensitive to drought and O3 stress.Therefore,the more sensitive components of the photosynthetic electron transport chain appeared to be the probability that an electron from the intersystem electron carriers is transferred to reduce end electron acceptors at the PSI acceptor side（δ（Ro））and the RC density on a chlorophyll basis（RC/ABS）.
基金founded by The National Science Foundation of China(No.40730634 andNo.40925002)
文摘In this study,effects of elevated air temperatures on thermal and hydrologic process of the shallow soil in the active layer were investigated. Open-top chambers(OTCs)were utilized to increase air temperatures 1-2℃ in OTC-1 and 3-5℃ in OTC-2 in the alpine meadow ecosystem on the Qinghai- Tibetan Plateau.Results show that the annual air temperatures under OTC-1 and OTC-2 were 1.21℃ and 3.62℃ higher than the Control,respectively.The entirely-frozen period of shallow soil in the active layer was shortened and the fully thawed period was prolonged with temperature increase.The maximum penetration depth and duration of the negative isotherm during the entirely-frozen period decreased, and soil freezing was retarded in the local scope of the soil profile when temperature increased.Meanwhile, the positive isotherm during the fully-thawed period increased,and the soil thawing was accelerated.Soil moisture under different manipulations decreased with the temperature increase at the same depth. During the early freezing period and the early fully- thawed period,the maximum soil moisture under the Control manipulation was at 0.2 m deep,whereas under OTC-1 and OTC-2 manipulations,the maximum soil moisture were at 0.4-0.5 m deep. These results indicate that elevated temperatures led to a decrease of the moisture in the surface soil.The coupled relationship between soil temperature and moisture was significantly affected by the temperature increase.During the freezing and thawing processes, the soil temperature and moisture under different manipulations fit the regression model given by the equationθV=a/{1+exp[b(TS+c)]}+d.
基金jointly funded by the Marine S&T Fund of Shandong Province for the Pilot National Laboratory for Marine Science and Technology (Qingdao)(2022QNLM 040003-3)the National Key R&D Program of China (2016YFE0109600)+3 种基金National Natural Science Foundation of China (U22A20558, 41240022, 41876057, 40872167, 41602143)China Geological Survey (1212010611402, GZH201200503, and DD20160144)by in-kind support from the Land Carbon ProgramLand Change Science R&D Program of the United States Geological Survey。
文摘Passive-warming, open-top chambers(OTCs) are widely applied for studying the effects of future climate warming on coastal wetlands. In this study, a set of six OTCs were established at a Phragmites wetland located in the Yellow River Delta of Dongying City, China. With data collected through online transmission and in-situ sensors, the attributes and patterns of realized OTCs warming are demonstrated.The authors also quantified the preliminary influence of experimental chamber warming on plant traits.OTCs produced an elevated average air temperature of 0.8°C(relative to controls) during the growing season(June to October) of 2018, and soil temperatures actually decreased by 0.54°C at a depth of 5 cm and 0.46°C at a depth of 30 cm in the OTCs. Variations in diel patterns of warming depend greatly on the heat sources of incoming radiation in the daytime versus soil heat flux at night. Warming effects were often larger during instantaneous analyses and influenced OTCs air temperatures from-2.5°C to 8.3°C dependent on various meteorological conditions at any given time, ranging from cooling influences from vertical heat exchange and vegetation to radiation-associated warming. Night-time temperature depressions in the OTCs were due to the low turbulence inside OTCs and changes in surface soilatmosphere heat transfer. Plant shoot density, basal diameter, and biomass of Phragmites decreased by23.2%, 6.3%, and 34.0%, respectively, under experimental warming versus controls, and plant height increased by 4.3%, reflecting less carbon allocation to stem structures as plants in the OTCs experienced simultaneous wind buffering. While these passive-warming OTCs created the desired warming effects both to the atmosphere and soils, pest damages on the plant leaves and lodging within the OTCs were extensive and serious, creating the need to consider control options for these chambers and the replicated OTCs studies underway in other Chinese Phragmites marshes(Panjin and Yancheng).
基金supported by the European Research Council under the European Community’s Seventh Framework Program(FP7/2007-2013)/ERC Grant agreement 242658(BIOCOM)support from the Salvador de Madariaga program of the Spanish Ministry of Education,Culture and Sports(PRX14/00225)during the writing of the manuscript.
文摘Aims Relatively few studies so far have assessed how ongoing global warming will affect the photosynthetic performance of dryland plant species.We evaluated the effects of warming on the photosynthetic rates of 10 species with contrasting functional attributes,and whether their functional traits modulated photosynthetic responses to warming.Methods A common garden experiment was conducted over 2 years with distinct environmental conditions(drier vs.wetter year).The experiment was designed as a randomized block design with two treatments:warming(control vs.~2.9℃ temperature increase)and species(Agropyron cristatum,Festuca ovina,Lygeum spartum,Medicago sativa,Plantago lanceolata,Psoralea bituminosa,Sanguisorba minor,Hedysarum coronarium,Dorycnium pentaphyllum and Phlomis herba-venti).We linked functional traits measurements with temporal variations in photosynthetic responses to warming.Important Findings In the drier year,warming increased photosynthetic rates at the beginning of the growing season,suggesting a modification in the growing period(earlier spring).In the wetter year,functional traits modulated photosynthetic responses to warming.Larger species with shorter leaves(e.g.M.sativa)had higher photosynthetic rates under warming compared to smaller species with larger leaves(e.g.F.ovina).Our results highlight the importance of(i)studying photosynthetic responses along different years and(ii)considering functional traits when evaluating photosynthetic responses to climate change,particularly in stressful environments such as drylands.
基金The research was supported by the Natural Science Fund Project of Jilin Provincial Department of Science and Technology in 2020the Jilin Agricultural University National Undergraduate Entrepreneurship Program in 2018the Jilin Agricultural University National Undergraduate Innovation Program in 2019.
文摘Background:Elevated atmospheric CO_(2) has direct and indirect influences on ecosystem processes.The impact of elevated atmospheric CO_(2) concentration on carbon and nitrogen transformations,together with the microbial community,was evaluated with water hyacinth(Eichhornia crassipes)in an open-top chamber replicated wetland.The responses of nitrogen and carbon pools in water and wetland soil,and microbial community abundance were studied under ambient CO_(2) and elevated CO_(2)(ambient+200μL L^(−1)).Results:Total biomass for the whole plant under elevated CO_(2) increased by an average of 8%(p=0.022).Wetlands,with water hyacinth,showed a significant increase in total carbon and total organic carbon in water by 7%(p=0.001)and 21%(p=0.001),respectively,under elevated CO_(2) compared to that of ambient CO_(2).Increase in dissolved carbon in water correlates with the presence of wetland plants since the water hyacinth can directly exchange CO_(2) from the atmosphere to water by the upper epidermis of leaves.Also,the enrichment CO_(2) showed an increase in total carbon and total organic carbon concentration in wetland soil by 3%(p=0.344)and 6%(p=0.008),respectively.The total nitrogen content in water increased by 26%(p=0.0001),while total nitrogen in wetland soil pool under CO_(2) enrichment decreased by 9%(p=0.011)due to increased soil microbial community abundance,extracted by phospholipid fatty acids,which was 25%larger in amount than that of the ambient treatment.Conclusion:The study revealed that the elevated CO_(2) would affect the carbon and nitrogen transformations in wetland plant,water,and soil pool and increase soil microbial community abundance.
基金The National Key Research and Development Program of China(2016YFC0502001,2016YFC0502005)Youth Innovation Promotion Association of Chinese Academy of Sciences(2020054)+2 种基金The National Natural Science Foundation of China(31600432)Bingwei Outstanding Young Talents Program of Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences(2018RC202)Tibet Science and Technology Major Projects of the Pratacultural Industry(XZ201901NA03)。
文摘Low temperature is an important limiting factor for alpine ecosystems on the Tibetan Plateau. This study is based on data from on-site experimental warming platforms(open top chambers, OTC) at three elevations(4300 m, 4500 m, 4700 m) on the Qinghai-Tibet Plateau. The carbon and nitrogen stoichiometry characteristics of plant communities, both above-ground and below-ground, were observed in three alpine meadow ecosystems in August and September of 2011 and August of 2012. Experimental warming significantly increased above-ground nitrogen content by 21.4% in September 2011 at 4500 m, and reduced above-ground carbon content by 3.9% in August 2012 at 4300 m. Experimental warming significantly increased below-ground carbon content by 5.5% in August 2011 at 4500 m, and the below-ground ratio of carbon to nitrogen by 28.0% in September 2011 at 4300 m, but reduced below-ground nitrogen content by 15.7% in September 2011 at 4700 m, below-ground carbon content by 34.3% in August 2012 at 4700 m, and the below-ground ratio of carbon to nitrogen by 37.9% in August 2012 at 4700 m. Experimental warming had no significant effect on the characteristics of community carbon and nitrogen stoichiometry under other conditions. Therefore, experimental warming had inconsistent effects on the carbon and nitrogen stoichiometry of plant communities at different elevations and during different months. Soil ammonium nitrogen and nitrate nitrogen content were the main factors affecting plant community carbon and nitrogen stoichiometry.
