Understanding the hydrological processes of forest ecosystems in Tibetan Plateau is crucial for protecting water resources and the environment, especially considering that evapotranspiration is the most dominant hydro...Understanding the hydrological processes of forest ecosystems in Tibetan Plateau is crucial for protecting water resources and the environment, especially considering that evapotranspiration is the most dominant hydrologic process in most forest systems. SHAW, as a physically based, hydrological model, provides a useful tool for understanding and analyzing evapotranspiration processes. Using the measured data of a faber fir forest ecosystem in eastern Tibetan Plateau, this paper assessed the model performance in simulating evapotranspiration and variability and transferability of the model parameters. Comparison of the simulated results by SHAW to the measured data showed that SHAW performed satisfactorily. Based on analyzing the simulated results by the calibrated and validated SHAW, some ET characteristics of faber fir forest ecosys-tem in the eastern Tibetan Plateau were found: 1) Daily plant transpiration is low, and daily ET mainly comes from surface evaporation including canopy, litter and soil evaporation. Peak ET rate was approxi-mately 4mm/day, occurring around late July. 2) Solar radiation is the most important factor accounting for daily ET variation, while air temperature is the secondary, wind speed and air relative humidity are minor and soil water storage is the least important among all the related factors. 3) The ratio of annual ET to pre-cipitation for the faber fir forest ecosystem in eastern Tibetan Plateau is low (18%) compared with the other forest ecosystems owing to high-elevation, high atmospheric humidity and low annual temperature.展开更多
The content characteristics of 16 elements(Al,Ca,Cr,Cu,Fe,K,Li,Mg,Mn,Mo,Na,Ni,P,Pb,Sr,and Zn) in 23 plant species collected from the Qinghai-Tibetan Plateau permafrost region were investigated using ICP-OES.Results sh...The content characteristics of 16 elements(Al,Ca,Cr,Cu,Fe,K,Li,Mg,Mn,Mo,Na,Ni,P,Pb,Sr,and Zn) in 23 plant species collected from the Qinghai-Tibetan Plateau permafrost region were investigated using ICP-OES.Results show that the average contents of Ca,K,Mg,Fe and P were higher than 1,000 mg/kg,those of Al,Na,Zn and Cr ranged between 10-1,000 mg/kg and those of Cu,Li,Pb and Mo were less than 10 mg/kg.The levels of Al,Ca,K,Mg and Na were within the scope of the reported terrestrial plant element content,those of Sr,Fe and Cr were higher than the average of the terrestrial plants and the maximum content of Mn was higher than the upper limit of the reported Mn content.The main character of the element content was of the Ca>K type,however,in terms of Cyperaceae species the element content character was K>Ca type.The contents of Ca,Li,Mg and Sr in Gramineae and Cyperaceae species were higher than those in other species and the contents of Ca,K,Mg,Fe,P,Al and Na in all collected plants were higher than those of other elements.Zn had weak variability with the lowest coefficient(i.e.,7.81%),while other elements had strong variability.The ratio of maximum content to minimum content indicated Ca and K had less change than other elements in the Qinghai-Tibetan Plateau permafrost region.Element content of alpine vegetation in the Qinghai-Tibetan Plateau permafrost region mainly shows a positive correlation,among which the correlation coefficient between Al and Pb,Al and Fe,Mo and Cr,Pb and Fe,Sr and Li were higher than 0.9,and negative correlation had no statistical significance.The correlation between Al and Fe,Mg,Mn in the Qinghai-Tibetan Plateau permafrost region were consistent with that reported in Kunlun Mountains.展开更多
Carbon fluxes were measured using a static chamber technique in an alpine steppe in the Qinghai-Tibet Plateau from July 2000 to July 2001.It was shown that carbon emissions decreased in autumn and increased in spring ...Carbon fluxes were measured using a static chamber technique in an alpine steppe in the Qinghai-Tibet Plateau from July 2000 to July 2001.It was shown that carbon emissions decreased in autumn and increased in spring of the next year,with higher values in growth seasons than in winters.An exponential correlation(Ecarbon = 0.22(exp(0.09T) + ln(0.31P + 1)),R2 = 0.77,P < 0.001) was shown between carbon emissions and environmental factors such as temperature(T) and precipitation(P).Using the daily temperature(T) and total precipitation(R),annual carbon emission from soil to the atmosphere was estimated to be 79.6 g C/m2,46% of which was emitted by microbial respiration.Considering an average net primary production of 92.5 g C/m2 per year within the 2 year experiment,alpine steppes can take up 55.9 g CO2-C/m2 per year.This indicates that alpine steppes are a distinct carbon sink,although this carbon reservoir was quite small.展开更多
Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope (δD and δ18O) values of different components such as plant xylem water, precipitation and river w...Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope (δD and δ18O) values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species (Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum) in three typical ecosystems (forest, shrub and desert) were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was in fluenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.展开更多
Aims Numerous studies have showed that the balance between negative and positive plant–plant interactions shifted along environmental gradients.But little is known how the positive or negative plant–plant interactio...Aims Numerous studies have showed that the balance between negative and positive plant–plant interactions shifted along environmental gradients.But little is known how the positive or negative plant–plant interactions varied with temporal fluctuating habitat conditions and plant ontogenetic phases.Methods In a 2-year experiment,the four perennial grasses(Kobresia humilis,Stipa aliena,Elymus nutans and Saussurea superba)were grown under four interaction treatments(no root or shoot interaction,only shoot interaction,only root interaction,root and shoot interaction).Intensity of above-and belowground interactions is proposed to vary with the fluctuation of seasonal climatic conditions and soil available nutrients.Here we report measurements of above-and belowground interactions during entire growing season.Correlation between plant interaction intensity and seasonal soil available N as well as habitat climate conditions was also performed.Important findings Our experiment found that root interactions had negative effect on plant growth for the four species during growing season.However,both negative and positive shoot interactions occurred among the four species.Despite there being shoot facilitative effect for E.nutans and S.superba,the full interaction was negative,suggested that root interaction take more important role on plant growth than that of shoot interaction.The interaction between root and shoot effect varied as a function of species identity and growth phases.The weak correlation of plant interaction intensity to habitat environmental factors suggested that plant ontogenetic characteristics may be primary factors causing temporal variation in plant interaction.展开更多
Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests(known as bomb-14C).Soil organic matter...Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests(known as bomb-14C).Soil organic matter was physically separated into light and heavy fractions.The concentration spike of bomb-14C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil.Based on the depth of the bomb-14C spike,the carbon sequestration rate was determined to be 38.5 g C/m2 per year for the forest soil and 27.1 g C/m2 per year for the alpine meadow soil.Considering that more than 60% of soil organic carbon(SOC) is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau,these alpine ecosystems might partially contribute to "the missing carbon sink".展开更多
文摘Understanding the hydrological processes of forest ecosystems in Tibetan Plateau is crucial for protecting water resources and the environment, especially considering that evapotranspiration is the most dominant hydrologic process in most forest systems. SHAW, as a physically based, hydrological model, provides a useful tool for understanding and analyzing evapotranspiration processes. Using the measured data of a faber fir forest ecosystem in eastern Tibetan Plateau, this paper assessed the model performance in simulating evapotranspiration and variability and transferability of the model parameters. Comparison of the simulated results by SHAW to the measured data showed that SHAW performed satisfactorily. Based on analyzing the simulated results by the calibrated and validated SHAW, some ET characteristics of faber fir forest ecosys-tem in the eastern Tibetan Plateau were found: 1) Daily plant transpiration is low, and daily ET mainly comes from surface evaporation including canopy, litter and soil evaporation. Peak ET rate was approxi-mately 4mm/day, occurring around late July. 2) Solar radiation is the most important factor accounting for daily ET variation, while air temperature is the secondary, wind speed and air relative humidity are minor and soil water storage is the least important among all the related factors. 3) The ratio of annual ET to pre-cipitation for the faber fir forest ecosystem in eastern Tibetan Plateau is low (18%) compared with the other forest ecosystems owing to high-elevation, high atmospheric humidity and low annual temperature.
基金by National Natural Science Foundation of China (No. 31100337)National Basic Research Program of China (No. 2005CB422005)
文摘The content characteristics of 16 elements(Al,Ca,Cr,Cu,Fe,K,Li,Mg,Mn,Mo,Na,Ni,P,Pb,Sr,and Zn) in 23 plant species collected from the Qinghai-Tibetan Plateau permafrost region were investigated using ICP-OES.Results show that the average contents of Ca,K,Mg,Fe and P were higher than 1,000 mg/kg,those of Al,Na,Zn and Cr ranged between 10-1,000 mg/kg and those of Cu,Li,Pb and Mo were less than 10 mg/kg.The levels of Al,Ca,K,Mg and Na were within the scope of the reported terrestrial plant element content,those of Sr,Fe and Cr were higher than the average of the terrestrial plants and the maximum content of Mn was higher than the upper limit of the reported Mn content.The main character of the element content was of the Ca>K type,however,in terms of Cyperaceae species the element content character was K>Ca type.The contents of Ca,Li,Mg and Sr in Gramineae and Cyperaceae species were higher than those in other species and the contents of Ca,K,Mg,Fe,P,Al and Na in all collected plants were higher than those of other elements.Zn had weak variability with the lowest coefficient(i.e.,7.81%),while other elements had strong variability.The ratio of maximum content to minimum content indicated Ca and K had less change than other elements in the Qinghai-Tibetan Plateau permafrost region.Element content of alpine vegetation in the Qinghai-Tibetan Plateau permafrost region mainly shows a positive correlation,among which the correlation coefficient between Al and Pb,Al and Fe,Mo and Cr,Pb and Fe,Sr and Li were higher than 0.9,and negative correlation had no statistical significance.The correlation between Al and Fe,Mg,Mn in the Qinghai-Tibetan Plateau permafrost region were consistent with that reported in Kunlun Mountains.
基金Supported by the National Basic Research Program (2005CB422005)the Pre-studies Project of National Basic Research Program(2005CCA05500)
文摘Carbon fluxes were measured using a static chamber technique in an alpine steppe in the Qinghai-Tibet Plateau from July 2000 to July 2001.It was shown that carbon emissions decreased in autumn and increased in spring of the next year,with higher values in growth seasons than in winters.An exponential correlation(Ecarbon = 0.22(exp(0.09T) + ln(0.31P + 1)),R2 = 0.77,P < 0.001) was shown between carbon emissions and environmental factors such as temperature(T) and precipitation(P).Using the daily temperature(T) and total precipitation(R),annual carbon emission from soil to the atmosphere was estimated to be 79.6 g C/m2,46% of which was emitted by microbial respiration.Considering an average net primary production of 92.5 g C/m2 per year within the 2 year experiment,alpine steppes can take up 55.9 g CO2-C/m2 per year.This indicates that alpine steppes are a distinct carbon sink,although this carbon reservoir was quite small.
基金the National Key Basic Research Program (NKBRP,2005CB422005)"Knowledge Innovation Engineering" of the Chinese Academy of Sciences (No. KZCX3-SW-339-04)
文摘Plant water sources were estimated by two or three compartment linear mixing models using hydrogen and oxygen isotope (δD and δ18O) values of different components such as plant xylem water, precipitation and river water as well as soil water on the Tibetan Plateau in the summer of 2005. Four dominant species (Quercus aquifolioides, Pinus tabulaeformis, Salix rehderiana and Nitraria tangutorum) in three typical ecosystems (forest, shrub and desert) were investigated in this study. Stable isotope ratios of the summer precipitations and the soil water presented variations in spatial and temporal scales. δ18O values of N. tangutorum xylem water were constant in the whole growth season and very similar to those of deep soil water. Water sources for all of the plants came from both precipitations and soil water. Plants switched rapidly among different water sources when environmental water conditions changed. Rainwater had different contributions to the plants, which was in fluenced by amounts of precipitation. The percentage of plant xylem water derived from rainwater rose with an increase in precipitation. Water sources for broad-leaved and coniferous species were different although they grew in the same environmental conditions. For example, the broad-leaved species Q. aquifolioides used mainly the water from deep soil, while 92.5% of xylem water of the coniferous species P. tabulaeformis was derived from rainwater during the growth season. The study will be helpful for us to fully understand responses of species on the Tibetan Plateau to changes in precipitation patterns, and to assess accurately changes of vegetation distribution in the future.
基金National Natural Science Foundation of China(grant no.30600070)the National Basic Research program of China(grant no.2005CB422005).
文摘Aims Numerous studies have showed that the balance between negative and positive plant–plant interactions shifted along environmental gradients.But little is known how the positive or negative plant–plant interactions varied with temporal fluctuating habitat conditions and plant ontogenetic phases.Methods In a 2-year experiment,the four perennial grasses(Kobresia humilis,Stipa aliena,Elymus nutans and Saussurea superba)were grown under four interaction treatments(no root or shoot interaction,only shoot interaction,only root interaction,root and shoot interaction).Intensity of above-and belowground interactions is proposed to vary with the fluctuation of seasonal climatic conditions and soil available nutrients.Here we report measurements of above-and belowground interactions during entire growing season.Correlation between plant interaction intensity and seasonal soil available N as well as habitat climate conditions was also performed.Important findings Our experiment found that root interactions had negative effect on plant growth for the four species during growing season.However,both negative and positive shoot interactions occurred among the four species.Despite there being shoot facilitative effect for E.nutans and S.superba,the full interaction was negative,suggested that root interaction take more important role on plant growth than that of shoot interaction.The interaction between root and shoot effect varied as a function of species identity and growth phases.The weak correlation of plant interaction intensity to habitat environmental factors suggested that plant ontogenetic characteristics may be primary factors causing temporal variation in plant interaction.
基金Supported by the National Natural Science Foundation of China (30590384)State Key Basic Research and Development Plan of China (2005CB422005)+1 种基金Key Project of the Chinese Academy of Sciences (KZCX3-SW-339-04)Open Fund of State Key Laboratory of ESPRE, Beijing Normal University(08-KF-04, 070401)
文摘Soil carbon sequestration was estimated in a conifer forest and an alpine meadow on the Tibetan Plateau using a carbon-14 radioactive label provided by thermonuclear weapon tests(known as bomb-14C).Soil organic matter was physically separated into light and heavy fractions.The concentration spike of bomb-14C occurred at a soil depth of 4 cm in both the forest soil and the alpine meadow soil.Based on the depth of the bomb-14C spike,the carbon sequestration rate was determined to be 38.5 g C/m2 per year for the forest soil and 27.1 g C/m2 per year for the alpine meadow soil.Considering that more than 60% of soil organic carbon(SOC) is stored in the heavy fraction and the large area of alpine forests and meadows on the Tibetan Plateau,these alpine ecosystems might partially contribute to "the missing carbon sink".
