青稞是藏族人民的主要食粮,青藏高原昼夜不对称增温明显,为了降低这种不对称增温对藏区未来粮食安全预测存在的不确定性,本研究在拉萨农业生态试验站以冬青一号为试验材料,采用FATI(Free Air Temperature Increase)田间开放式增温系统...青稞是藏族人民的主要食粮,青藏高原昼夜不对称增温明显,为了降低这种不对称增温对藏区未来粮食安全预测存在的不确定性,本研究在拉萨农业生态试验站以冬青一号为试验材料,采用FATI(Free Air Temperature Increase)田间开放式增温系统进行了为期两个生长季节(即2018–2019和2019–2020年)的昼夜不对称增温试验(即全天增温AW、白天增温DW、夜间增温NW和对照CK),以期探讨不对称增温对西藏冬青稞生长特性和产量的影响。结果表明:与对照相比,三种不同增温处理对冬青稞的物候期的影响显著,均导致各物候期提前,全生育期缩短,影响程度表现为AW>NW>DW,并且不同增温处理均使得冬青稞从播种到抽穗期的间隔缩短,抽穗期到完熟期间隔增加,AW效果最为明显,且达到统计显著水平(P<0.05);在生长前中期,冬青稞地上生物量和株高在不同增温影响下均有提高的趋势,生长后期,NW处理明显高于其他处理。此外,增温使得完熟期叶和茎鞘的分配比重下降,根和穗的分配比上升;AW、NW和DW增温处理产量两年平均提高了16.4%、24.6%和9.5%,其中2019–2020年NW处理较对照达到显著水平(t=–2.541,P=0.026);产量构成方面,有效穗数和千粒重有提高的趋势,每穗粒数除AW处理外有提高的趋势,穗长和结实率除NW处理外有降低的趋势。因此,昼夜不对称增温对西藏冬青稞的影响不同。展开更多
Plant traits and individual plant biomass allocation of 57 perennial herbaceous species,belonging to three common functional groups (forbs,grasses and sedges) at subalpine (3700 m ASL),alpine (4300 m ASL) and subniva...Plant traits and individual plant biomass allocation of 57 perennial herbaceous species,belonging to three common functional groups (forbs,grasses and sedges) at subalpine (3700 m ASL),alpine (4300 m ASL) and subnival (≥5000 m ASL) sites were examined to test the hypothesis that at high altitudes,plants reduce the proportion of aboveground parts and allocate more biomass to belowground parts,especially storage organs,as altitude increases,so as to geminate and resist environmental stress.However,results indicate that some divergence in biomass allocation exists among organs.With increasing altitude,the mean fractions of total biomass allocated to aboveground parts decreased.The mean fractions of total biomass allocation to storage organs at the subalpine site (7%±2% S.E.) were distinct from those at the alpine (23%±6%) and subnival (21%±6%) sites,while the proportions of green leaves at all altitudes remained almost constant.At 4300 m and 5000 m,the mean fractions of flower stems decreased by 45% and 41%,respectively,while fine roots increased by 86% and 102%,respectively.Specific leaf areas and leaf areas of forbs and grasses deceased with rising elevation,while sedges showed opposite trends.For all three functional groups,leaf area ratio and leaf area root mass ratio decreased,while fine root biomass increased at higher altitudes.Biomass allocation patterns of alpine plants were characterized by a reduction in aboveground reproductive organs and enlargement of fine roots,while the proportion of leaves remained stable.It was beneficial for high altitude plants to compensate carbon gain and nutrient uptake under low temperature and limited nutrients by stabilizing biomass investment to photosynthetic structures and increasing the absorption surface area of fine roots.In contrast to forbs and grasses that had high mycorrhizal infection,sedges had higher single leaf area and more root fraction,especially fine roots.展开更多
Accurate quantification of aboveground biomass of grasslands in alpine regions plays an important role in accurate quantification of global carbon cycling.The monthly normalized difference vegetation index（NDVI）,enh...Accurate quantification of aboveground biomass of grasslands in alpine regions plays an important role in accurate quantification of global carbon cycling.The monthly normalized difference vegetation index（NDVI）,enhanced vegetation index（EVI）,mean air temperature（Ta）,≥5℃ accumulated air temperature（AccT）,total precipitation（TP）,and the ratio of TP to AccT（TP/AccT） were used to model aboveground biomass（AGB） in grasslands on the Tibetan Plateau.Three stepwise multiple regression methods,including stepwise multiple regression of AGB with NDVI and EVI,stepwise multiple regression of AGB with Ta,AccT,TP and TP/AccT,and stepwise multiple regression of AGB with NDVI,EVI,Ta,AccT,TP and TP/Acc T were compared.The mean absolute error（MAE） and root mean squared error（RMSE） values between estimated AGB by the NDVI and measured AGB were 31.05 g m^（-2） and 44.12 g m^（-2）,and 95.43 g m^（-2） and 131.58 g m^（-2） in the meadow and steppe,respectively.The MAE and RMSE values between estimated AGB by the AccT and measured AGB were 33.61 g m^（-2） and 48.04 g m^（-2） in the steppe,respectively.The MAE and RMSE values between estimated AGB by the vegetation index and climatic data and measured AGB were 28.09 g m^（-2） and 42.71 g m^（-2）,and 35.86 g m^（-2） and 47.94 g m^（-2）,in the meadow and steppe,respectively.The study finds that a combination of vegetation index and climatic data can improve the accuracy of estimates of AGB that are arrived at using the vegetation index or climatic data.The accuracy of estimates varied depending on the type of grassland.展开更多
In order to understand whether or not the response of vegetation indices and biomass production to warming varies with warming magnitude,an experiment of field warming at two magnitudes was conducted in an alpine mead...In order to understand whether or not the response of vegetation indices and biomass production to warming varies with warming magnitude,an experiment of field warming at two magnitudes was conducted in an alpine meadow on the northern Tibetan Plateau beginning in late June,2013.The normalized difference vegetation index（NDVI）,green normalized difference vegetation index（GNDVI） and soil adjusted vegetation index（SAVI） data were obtained using a Tetracam Agricultural Digital Camera in 2013–2014.The gross primary production（GPP） and aboveground plant biomass（AGB） were modeled using the surface measured NDVI and climatic data during the growing seasons（i.e.June–September） in 2013–2014.Both low and high warming significantly increased air temperature by 1.54 and 4.00°C,respectively,and significantly increased vapor pressure deficit by 0.13 and 0.31 kP a,respectively,in 2013-2014.There were no significant differences of GNDVI,AGB and ANPP among the three warming treatments.The high warming significantly reduced average NDVI by 23.3%（-0.06）,while the low warming did not affect average NDVI.The low and high warming significantly decreased average SAVI by 19.0%（-0.04） and 27.4%（-0.05）,respectively,and average GPP by 24.2%（i.e.0.21 g C m^（-2） d^（-1）） and 44.0%（i.e.0.39 g C m^（–2） d^（-1））,respectively.However,the differences of the average NDVI,SAVI,and GPP between low and high warming were negligible.Our findings suggest that a greater drying may dampen the effect of a higher warming on vegetation indices and biomass production in alpine meadow on the northern Tibetan Plateau.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
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The Natural Science Foundation of China (31370458)The Science and Technology Service Network Project of Chinese Academy of Sciences (KFJ-STS-QYZD-117)+1 种基金The Local Project Guided by the Central Government (YDZX20195400004717)The Key Project of Dazi District of Tibet Autonomous Region (XZDZKJ-2021-01)。
文摘青稞是藏族人民的主要食粮,青藏高原昼夜不对称增温明显,为了降低这种不对称增温对藏区未来粮食安全预测存在的不确定性,本研究在拉萨农业生态试验站以冬青一号为试验材料,采用FATI(Free Air Temperature Increase)田间开放式增温系统进行了为期两个生长季节(即2018–2019和2019–2020年)的昼夜不对称增温试验(即全天增温AW、白天增温DW、夜间增温NW和对照CK),以期探讨不对称增温对西藏冬青稞生长特性和产量的影响。结果表明:与对照相比,三种不同增温处理对冬青稞的物候期的影响显著,均导致各物候期提前,全生育期缩短,影响程度表现为AW>NW>DW,并且不同增温处理均使得冬青稞从播种到抽穗期的间隔缩短,抽穗期到完熟期间隔增加,AW效果最为明显,且达到统计显著水平(P<0.05);在生长前中期,冬青稞地上生物量和株高在不同增温影响下均有提高的趋势,生长后期,NW处理明显高于其他处理。此外,增温使得完熟期叶和茎鞘的分配比重下降,根和穗的分配比上升;AW、NW和DW增温处理产量两年平均提高了16.4%、24.6%和9.5%,其中2019–2020年NW处理较对照达到显著水平(t=–2.541,P=0.026);产量构成方面,有效穗数和千粒重有提高的趋势,每穗粒数除AW处理外有提高的趋势,穗长和结实率除NW处理外有降低的趋势。因此,昼夜不对称增温对西藏冬青稞的影响不同。
基金supported by the National Science & Technology Pillar Program (Grant Nos. 2007BAD80B03 and 2007BAC06B01)a West Light Joint Scholar-ship from the Chinese Academy of Sciences in 2008the National Natural Science Foundation of China (Grant Nos. 40771074 and 30700080)
文摘Plant traits and individual plant biomass allocation of 57 perennial herbaceous species,belonging to three common functional groups (forbs,grasses and sedges) at subalpine (3700 m ASL),alpine (4300 m ASL) and subnival (≥5000 m ASL) sites were examined to test the hypothesis that at high altitudes,plants reduce the proportion of aboveground parts and allocate more biomass to belowground parts,especially storage organs,as altitude increases,so as to geminate and resist environmental stress.However,results indicate that some divergence in biomass allocation exists among organs.With increasing altitude,the mean fractions of total biomass allocated to aboveground parts decreased.The mean fractions of total biomass allocation to storage organs at the subalpine site (7%±2% S.E.) were distinct from those at the alpine (23%±6%) and subnival (21%±6%) sites,while the proportions of green leaves at all altitudes remained almost constant.At 4300 m and 5000 m,the mean fractions of flower stems decreased by 45% and 41%,respectively,while fine roots increased by 86% and 102%,respectively.Specific leaf areas and leaf areas of forbs and grasses deceased with rising elevation,while sedges showed opposite trends.For all three functional groups,leaf area ratio and leaf area root mass ratio decreased,while fine root biomass increased at higher altitudes.Biomass allocation patterns of alpine plants were characterized by a reduction in aboveground reproductive organs and enlargement of fine roots,while the proportion of leaves remained stable.It was beneficial for high altitude plants to compensate carbon gain and nutrient uptake under low temperature and limited nutrients by stabilizing biomass investment to photosynthetic structures and increasing the absorption surface area of fine roots.In contrast to forbs and grasses that had high mycorrhizal infection,sedges had higher single leaf area and more root fraction,especially fine roots.
基金National Natural Science Foundation of China(31600432)National Key Research Projects of China(2016YFC0502005+3 种基金2016YFC0502006)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)Science and Technology Plan Projects of Tibet Autonomous Region(Forage Grass Industry)National Science and Technology Plan Project of China(2013BAC04B01,2011BAC09B03,2007BAC06B01)
文摘Accurate quantification of aboveground biomass of grasslands in alpine regions plays an important role in accurate quantification of global carbon cycling.The monthly normalized difference vegetation index（NDVI）,enhanced vegetation index（EVI）,mean air temperature（Ta）,≥5℃ accumulated air temperature（AccT）,total precipitation（TP）,and the ratio of TP to AccT（TP/AccT） were used to model aboveground biomass（AGB） in grasslands on the Tibetan Plateau.Three stepwise multiple regression methods,including stepwise multiple regression of AGB with NDVI and EVI,stepwise multiple regression of AGB with Ta,AccT,TP and TP/AccT,and stepwise multiple regression of AGB with NDVI,EVI,Ta,AccT,TP and TP/Acc T were compared.The mean absolute error（MAE） and root mean squared error（RMSE） values between estimated AGB by the NDVI and measured AGB were 31.05 g m^（-2） and 44.12 g m^（-2）,and 95.43 g m^（-2） and 131.58 g m^（-2） in the meadow and steppe,respectively.The MAE and RMSE values between estimated AGB by the AccT and measured AGB were 33.61 g m^（-2） and 48.04 g m^（-2） in the steppe,respectively.The MAE and RMSE values between estimated AGB by the vegetation index and climatic data and measured AGB were 28.09 g m^（-2） and 42.71 g m^（-2）,and 35.86 g m^（-2） and 47.94 g m^（-2）,in the meadow and steppe,respectively.The study finds that a combination of vegetation index and climatic data can improve the accuracy of estimates of AGB that are arrived at using the vegetation index or climatic data.The accuracy of estimates varied depending on the type of grassland.
基金National Natural Science Foundation of China(31600432)National Key Research Projects of China(2016YFC0502005+3 种基金2016YFC0502006)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 Science and Technology Plan Projects of Tibet Autonomous Region(Forage Grass Industry)the National Science and Technology Plan Project of China(2013BAC04B01,2011BAC09B03,2007BAC06B01)
文摘In order to understand whether or not the response of vegetation indices and biomass production to warming varies with warming magnitude,an experiment of field warming at two magnitudes was conducted in an alpine meadow on the northern Tibetan Plateau beginning in late June,2013.The normalized difference vegetation index（NDVI）,green normalized difference vegetation index（GNDVI） and soil adjusted vegetation index（SAVI） data were obtained using a Tetracam Agricultural Digital Camera in 2013–2014.The gross primary production（GPP） and aboveground plant biomass（AGB） were modeled using the surface measured NDVI and climatic data during the growing seasons（i.e.June–September） in 2013–2014.Both low and high warming significantly increased air temperature by 1.54 and 4.00°C,respectively,and significantly increased vapor pressure deficit by 0.13 and 0.31 kP a,respectively,in 2013-2014.There were no significant differences of GNDVI,AGB and ANPP among the three warming treatments.The high warming significantly reduced average NDVI by 23.3%（-0.06）,while the low warming did not affect average NDVI.The low and high warming significantly decreased average SAVI by 19.0%（-0.04） and 27.4%（-0.05）,respectively,and average GPP by 24.2%（i.e.0.21 g C m^（-2） d^（-1）） and 44.0%（i.e.0.39 g C m^（–2） d^（-1））,respectively.However,the differences of the average NDVI,SAVI,and GPP between low and high warming were negligible.Our findings suggest that a greater drying may dampen the effect of a higher warming on vegetation indices and biomass production in alpine meadow on the northern Tibetan Plateau.
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.
