Soil microbes play important roles in terrestrial ecosystem carbon and nitrogen cycling. Climatic warming and elevated CO2 are two aspects of climatic change. In this study, we used a meta-analysis approach to synthes...Soil microbes play important roles in terrestrial ecosystem carbon and nitrogen cycling. Climatic warming and elevated CO2 are two aspects of climatic change. In this study, we used a meta-analysis approach to synthesise observations related to the effects of warming and elevated CO2 on soil microbial biomass and community structure. Ecosystem types were mainly grouped into forests and grasslands. Warming methods included open top chambers and infrared radiators. Experimental settings included all-day warming, daytime warming and nighttime warming. Warming increased soil actinomycetes and saprotrophic fungi, while elevated CO2 decreased soil gram-positive bacteria(G+). Mean annual temperature and mean annual precipitation were negatively correlated with warming effects on gram-negative bacteria(G–) and total phospholipid fatty acid(PLFA), respectively. Elevation was positively correlated with the warming effect on total PLFA, bacteria, G+ and G–. Grassland exhibited a positive response of total PLFA and actinomycetes to warming, while forest exhibited a positive response in the ratio of soil fungi to bacteria(F/B ratio) to warming. The open top chamber method increased G–, while the infrared radiator method decreased the F/B ratio. Daytime warming rather than all-day warming increased G–. Our findings indicated that the effects of warming on soil microbes differed with ecosystem types, warming methods, warming times, elevation and local climate conditions.展开更多
Enclosure is one of the most widely used management tools for degraded alpine grassland on the northern Tibetan Plateau, but the responses of different types of grassland to enclosure may vary, and research on these r...Enclosure is one of the most widely used management tools for degraded alpine grassland on the northern Tibetan Plateau, but the responses of different types of grassland to enclosure may vary, and research on these responses can provide a scientific basis for improving ecological conservation. This study took one site for each of three grassland types(alpine meadow, alpine steppe and alpine desert) on the northern Tibetan Plateau as examples, and explored the effects of enclosure on plant and soil nutrients by comparing differences in plant community biomass, leaf-soil nutrient content and their stoichiometry between samples from inside and outside the fence. The results showed that enclosure can significantly increase all aboveground biomass in these three grassland types, but it only increased the 10–20 cm underground biomass in the alpine desert. Enclosure also significantly increased the leaf nutrient content of the dominant plants and contents of total nitrogen(N), total potassium(K), and organic carbon(C) in 10–20 cm soil in alpine desert, thus changing the stoichiometry between C, N and P(phosphorus). However, enclosure significantly increased only the N content of dominant plant leaves in alpine steppe, while other nutrients and stoichiometries of both plant leaves and soil did not show significant differences in alpine meadow and alpine steppe. These results suggested that enclosure has differential effects on these three types of alpine grasslands on the northern Tibetan Plateau, and the alpine desert showed the most active ecological conservation in the responses of its soil and plant nutrients.展开更多
Pennisetum centrasiaticum is widely distributed in arid and semi-arid areas of Tibet. Its rhizome system is developed and has strong resistance to adversity. In this study, the physiological characteristics and drough...Pennisetum centrasiaticum is widely distributed in arid and semi-arid areas of Tibet. Its rhizome system is developed and has strong resistance to adversity. In this study, the physiological characteristics and drought resistance of P.centrasiaticum seedlings from 12 drought-stressed sites in Tibet were examined at the Lhasa Plateau Ecosystem Research Station of the Chinese Academy of Sciences. PEG-6000 solution with five levels of water potential(0, –0.7, –1.4, –2.1, and –2.8 MPa) was used to simulate drought stress, and malondialdehyde(MDA), proline(Pro) and chlorophyll contents were determined. The balance between production and elimination of reactive oxygen species in P.centrasiaticum was destroyed, leading to membrane lipid peroxidation and the production of MDA, and accelerating the decomposition of chlorophyll. P.centrasiaticum absorbed water from the outside to resist drought by secreting proline and other osmotic regulating substances. The Pro and chlorophyll contents in P.centrasiaticum showed a temporary rising trend, and then decreased with the decrease in water potential. MDA content increased with the decrease in water potential. By using the membership function method, the drought resistance of P.centrasiaticum seedlings from the 12 areas was evaluated, and the results showed that the drought resistance at the sites went from strong to weak in this order: Xietongmen > Linzhou > Sog > Damxung > Tingri > Namling > Gyirong > Linzhi > Purang > Dingjie > Longzi > Sa’gya. The drought resistance of P.centrasiaticum was strong in Xietongmen, Linzhou and Sog. Whether P.centrasiaticum from these three areas is suitable for cultivation in arid and semi-arid areas of Tibet needs further study.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
Vapor pressure deficit（VPD） is an important parameter in modelling hydrologic cycles and vegetation productivity. Meteorological stations are scarce in remote areas,which often results in imprecise estimations of VP...Vapor pressure deficit（VPD） is an important parameter in modelling hydrologic cycles and vegetation productivity. Meteorological stations are scarce in remote areas,which often results in imprecise estimations of VPD on the Tibetan Plateau. Moderate Resolution Imaging Spectroradiometer（MODIS） provides evapotranspiration data,which may offer the possibility of scaling up VPD estimations on the Tibetan Plateau. However,no studies thus far have estimated VPD using MODIS evapotranspiration data on the Tibetan Plateau. Therefore,this study used MODIS potential evapotranspiration（PET） to estimate VPD in alpine meadows,alpine steppes,croplands,forests and shrublands for the year,spring,summer,autumn and winter in 2000-2012. A series of root-meansquared-error（RMSE） and mean-absolute-error（MAE） values were obtained for correlating measured VPD and estimated VPD using MODIS PET data for each listed time period and vegetation type： whole year（0.98-2.15 hPa and 0.68-1.44 hPa）,spring（0.95-2.34 hPa and 0.72-1.54 hPa）,summer（1.39-2.60 hPa and 0.89-1.96 hPa）,autumn（0.78-1.93 hPa and 0.56-1.36 hPa）,winter（0.48-1.40 hPa and 0.36-0.98 hPa）,alpine steppes（0.48- 1.39 hPa and 0.36-1.00 hPa）,alpine meadows（0.58-1.39 hPa and 0.44-0.90 hPa）,croplands（1.10-2.55 hPa and 0.82-1.74 hPa）,shrublands（0.98-1.90 hPa and 0.78-1.37 hPa）,and forests（1.40-2.60 hPa and 0.98-1.96 hPa）,respectively. Therefore,MODIS PET may be used to estimate VPD,and better results may be obtained if future studies incorporate vegetation types and seasons when the VPD data are estimated using MODIS PET on the Tibetan Plateau.展开更多
基金National Natural Science Foundation of China(31600432,41571042)The National Key Research Projects of China(2017YFA0604801)+2 种基金The Youth Innovation Research Team Project of Key Laboratory of Ecosystem Network Observation and Modeling(LENOM2016Q0002)Chinese Academy of Science Western Light Talents Program(Response of livestock carrying capability to climatic change and grazing in the alpine meadow of Northern Tibetan Plateau)Tibet Science and Technology Major Projects of Pratacultural Industry
文摘Soil microbes play important roles in terrestrial ecosystem carbon and nitrogen cycling. Climatic warming and elevated CO2 are two aspects of climatic change. In this study, we used a meta-analysis approach to synthesise observations related to the effects of warming and elevated CO2 on soil microbial biomass and community structure. Ecosystem types were mainly grouped into forests and grasslands. Warming methods included open top chambers and infrared radiators. Experimental settings included all-day warming, daytime warming and nighttime warming. Warming increased soil actinomycetes and saprotrophic fungi, while elevated CO2 decreased soil gram-positive bacteria(G+). Mean annual temperature and mean annual precipitation were negatively correlated with warming effects on gram-negative bacteria(G–) and total phospholipid fatty acid(PLFA), respectively. Elevation was positively correlated with the warming effect on total PLFA, bacteria, G+ and G–. Grassland exhibited a positive response of total PLFA and actinomycetes to warming, while forest exhibited a positive response in the ratio of soil fungi to bacteria(F/B ratio) to warming. The open top chamber method increased G–, while the infrared radiator method decreased the F/B ratio. Daytime warming rather than all-day warming increased G–. Our findings indicated that the effects of warming on soil microbes differed with ecosystem types, warming methods, warming times, elevation and local climate conditions.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19050502,XDA20010201)The National Key Research Projects of China(2017YFA0604801,2016YFC0502001)The National Natural Science Foundation of China(31770477)。
文摘Enclosure is one of the most widely used management tools for degraded alpine grassland on the northern Tibetan Plateau, but the responses of different types of grassland to enclosure may vary, and research on these responses can provide a scientific basis for improving ecological conservation. This study took one site for each of three grassland types(alpine meadow, alpine steppe and alpine desert) on the northern Tibetan Plateau as examples, and explored the effects of enclosure on plant and soil nutrients by comparing differences in plant community biomass, leaf-soil nutrient content and their stoichiometry between samples from inside and outside the fence. The results showed that enclosure can significantly increase all aboveground biomass in these three grassland types, but it only increased the 10–20 cm underground biomass in the alpine desert. Enclosure also significantly increased the leaf nutrient content of the dominant plants and contents of total nitrogen(N), total potassium(K), and organic carbon(C) in 10–20 cm soil in alpine desert, thus changing the stoichiometry between C, N and P(phosphorus). However, enclosure significantly increased only the N content of dominant plant leaves in alpine steppe, while other nutrients and stoichiometries of both plant leaves and soil did not show significant differences in alpine meadow and alpine steppe. These results suggested that enclosure has differential effects on these three types of alpine grasslands on the northern Tibetan Plateau, and the alpine desert showed the most active ecological conservation in the responses of its soil and plant nutrients.
基金The National Key Research and Development Program of China(2016YFC0502005)The Tibet Science and Technology Major Projects of the Pratacultural Industry(XZ201901NA03)+1 种基金The Lhasa Industrial Integration Project(XCKJ004)Research and Demonstration on the De-velopment Model of Forage Industry in Dagze County(LSKJ2018006)。
文摘Pennisetum centrasiaticum is widely distributed in arid and semi-arid areas of Tibet. Its rhizome system is developed and has strong resistance to adversity. In this study, the physiological characteristics and drought resistance of P.centrasiaticum seedlings from 12 drought-stressed sites in Tibet were examined at the Lhasa Plateau Ecosystem Research Station of the Chinese Academy of Sciences. PEG-6000 solution with five levels of water potential(0, –0.7, –1.4, –2.1, and –2.8 MPa) was used to simulate drought stress, and malondialdehyde(MDA), proline(Pro) and chlorophyll contents were determined. The balance between production and elimination of reactive oxygen species in P.centrasiaticum was destroyed, leading to membrane lipid peroxidation and the production of MDA, and accelerating the decomposition of chlorophyll. P.centrasiaticum absorbed water from the outside to resist drought by secreting proline and other osmotic regulating substances. The Pro and chlorophyll contents in P.centrasiaticum showed a temporary rising trend, and then decreased with the decrease in water potential. MDA content increased with the decrease in water potential. By using the membership function method, the drought resistance of P.centrasiaticum seedlings from the 12 areas was evaluated, and the results showed that the drought resistance at the sites went from strong to weak in this order: Xietongmen > Linzhou > Sog > Damxung > Tingri > Namling > Gyirong > Linzhi > Purang > Dingjie > Longzi > Sa’gya. The drought resistance of P.centrasiaticum was strong in Xietongmen, Linzhou and Sog. Whether P.centrasiaticum from these three areas is suitable for cultivation in arid and semi-arid areas of Tibet needs further study.
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.
基金National Key Research and Development Program of China(2017YFA0604801 2016YFC0502006)+5 种基金National Natural Science Foundation of China(41571042 31600432)Chinese Academy of Science Western Light Talents Program(Response of livestock carrying capability to climatic change and grazing in the alpine meadow of Northern Tibetan Plateau)the Youth Innovation Research Team Project of Key Laboratory of Ecosystem Network Observation and Modeling(LENOM2016Q0002)Natural Science Foundation of Tibet Autonomous Region(Response of species richness and above-ground biomass to warming in the alpine meadow of Tibet)Science and Technology Plan Projects of Tibet Autonomous Region(Forage Grass Industry)
文摘Vapor pressure deficit（VPD） is an important parameter in modelling hydrologic cycles and vegetation productivity. Meteorological stations are scarce in remote areas,which often results in imprecise estimations of VPD on the Tibetan Plateau. Moderate Resolution Imaging Spectroradiometer（MODIS） provides evapotranspiration data,which may offer the possibility of scaling up VPD estimations on the Tibetan Plateau. However,no studies thus far have estimated VPD using MODIS evapotranspiration data on the Tibetan Plateau. Therefore,this study used MODIS potential evapotranspiration（PET） to estimate VPD in alpine meadows,alpine steppes,croplands,forests and shrublands for the year,spring,summer,autumn and winter in 2000-2012. A series of root-meansquared-error（RMSE） and mean-absolute-error（MAE） values were obtained for correlating measured VPD and estimated VPD using MODIS PET data for each listed time period and vegetation type： whole year（0.98-2.15 hPa and 0.68-1.44 hPa）,spring（0.95-2.34 hPa and 0.72-1.54 hPa）,summer（1.39-2.60 hPa and 0.89-1.96 hPa）,autumn（0.78-1.93 hPa and 0.56-1.36 hPa）,winter（0.48-1.40 hPa and 0.36-0.98 hPa）,alpine steppes（0.48- 1.39 hPa and 0.36-1.00 hPa）,alpine meadows（0.58-1.39 hPa and 0.44-0.90 hPa）,croplands（1.10-2.55 hPa and 0.82-1.74 hPa）,shrublands（0.98-1.90 hPa and 0.78-1.37 hPa）,and forests（1.40-2.60 hPa and 0.98-1.96 hPa）,respectively. Therefore,MODIS PET may be used to estimate VPD,and better results may be obtained if future studies incorporate vegetation types and seasons when the VPD data are estimated using MODIS PET on the Tibetan Plateau.
