Water-use efficiency(WUE) is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored t...Water-use efficiency(WUE) is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored the linkage between alteration in vegetation and WUE. Here, we analyzed the responses of leaf WUE, ecosystem carbon and water exchanges, ecosystem WUE, and plant community composition changes under normal conditions and also under extra 15% or 30% increases in annual precipitation in a temperate desert ecosystem of Xinjiang, China. We found that leaf WUE and ecosystem WUE showed inconsistent responses to increasing precipitation. Leaf WUE consistently decreased as precipitation increased. By contrast, the responses of the ecosystem WUE to increasing precipitation are different in different precipitation regimes: increasing by 33.9% in the wet year(i.e., the normal precipitation years)and decreasing by 4.1% in the dry year when the precipitation was about 30% less than that in the wet year.We systematically assessed the herbaceous community dynamics, community composition, and vegetation coverage to explain the responses of ecosystem WUE, and found that the between-year discrepancy in ecosystem WUE was consistent with the extent to which plant biomass was stimulated by the increase in precipitation. Although there was no change in the relative significance of ephemerals in the plant community, its greater overall plant biomass drove an increased ecosystem WUE under the conditions of increasing precipitation in 2011. However, the slight increase in plant biomass exerted no significant effect on ecosystem WUE in 2012. Our findings suggest that an alteration in the dominant species in this plant community can induce a shift in the carbon-and water-based economics of desert ecosystems.展开更多
Carbon dioxide fluxes of Kobresia humilis and Potentilla fruticosa shrub meadows,two typical ecosystems in the Qinghai-Tibet Plateau,were measured by eddy covari-ance technology and the data collected in August 2003 w...Carbon dioxide fluxes of Kobresia humilis and Potentilla fruticosa shrub meadows,two typical ecosystems in the Qinghai-Tibet Plateau,were measured by eddy covari-ance technology and the data collected in August 2003 were employed to analyze the relations between carbon dioxide fluxes and environmental factors of the ecosystems.August is the time when the two ecosystems reach their peak leaf area indexes and stay stable,and also the period when the net carbon absorptions of Kobresia humilis and Potentilla fruticosa shrub meadows reach 56.2 g C·m^(-2)and 32.6 g C·m^(-2),with their highest daily carbon dioxide absorp-tions standing at 12.7μmol·m^(-2)·s^(-1)and 9.3μmol·m^(-2)·s^(-1),and their highest carbon discharges at 5.1μmol·m^(-2)·s^(-1)and 5.7μmol·m^(-2)·s^(-1),respectively.At the same photosynthetic photo flux densities(PPFD),the carbon dioxide-uptake rate of the Kobresia humilis meadow is higher than that of the Potentilla fruticosa shrub meadow;where the PPFD are higher than 1,200μmol·m^(-2)·s^(-1).The carbon dioxide uptake rates of the two ecosystems declined as air temperature increased,but the carbon dioxide uptake rate of the Kobresia humilis meadow decreased more quickly(-0.086)than that of the Potentilla fruticosa shrub meadow(-0.016).Soil moistures exert influence on the soil respirations and this varies with the vegetation type.The daily carbon dioxide absorptions of the ecosystems increase with increased diurnal temperature differences and higher diurnal temperature differences result in higher carbon dioxide exchanges.There exists a negative correlation between the vegetation albedos and the carbon dioxide fluxes.展开更多
基金supported by the Science Fund for Distinguished Young Scholars in the Xinjiang Uygur Autonomous Region (QN2015JQ007)
文摘Water-use efficiency(WUE) is a key plant functional trait that plays a central role in the global cycles of water and carbon. Although increasing precipitation may cause vegetation changes, few studies have explored the linkage between alteration in vegetation and WUE. Here, we analyzed the responses of leaf WUE, ecosystem carbon and water exchanges, ecosystem WUE, and plant community composition changes under normal conditions and also under extra 15% or 30% increases in annual precipitation in a temperate desert ecosystem of Xinjiang, China. We found that leaf WUE and ecosystem WUE showed inconsistent responses to increasing precipitation. Leaf WUE consistently decreased as precipitation increased. By contrast, the responses of the ecosystem WUE to increasing precipitation are different in different precipitation regimes: increasing by 33.9% in the wet year(i.e., the normal precipitation years)and decreasing by 4.1% in the dry year when the precipitation was about 30% less than that in the wet year.We systematically assessed the herbaceous community dynamics, community composition, and vegetation coverage to explain the responses of ecosystem WUE, and found that the between-year discrepancy in ecosystem WUE was consistent with the extent to which plant biomass was stimulated by the increase in precipitation. Although there was no change in the relative significance of ephemerals in the plant community, its greater overall plant biomass drove an increased ecosystem WUE under the conditions of increasing precipitation in 2011. However, the slight increase in plant biomass exerted no significant effect on ecosystem WUE in 2012. Our findings suggest that an alteration in the dominant species in this plant community can induce a shift in the carbon-and water-based economics of desert ecosystems.
文摘Carbon dioxide fluxes of Kobresia humilis and Potentilla fruticosa shrub meadows,two typical ecosystems in the Qinghai-Tibet Plateau,were measured by eddy covari-ance technology and the data collected in August 2003 were employed to analyze the relations between carbon dioxide fluxes and environmental factors of the ecosystems.August is the time when the two ecosystems reach their peak leaf area indexes and stay stable,and also the period when the net carbon absorptions of Kobresia humilis and Potentilla fruticosa shrub meadows reach 56.2 g C·m^(-2)and 32.6 g C·m^(-2),with their highest daily carbon dioxide absorp-tions standing at 12.7μmol·m^(-2)·s^(-1)and 9.3μmol·m^(-2)·s^(-1),and their highest carbon discharges at 5.1μmol·m^(-2)·s^(-1)and 5.7μmol·m^(-2)·s^(-1),respectively.At the same photosynthetic photo flux densities(PPFD),the carbon dioxide-uptake rate of the Kobresia humilis meadow is higher than that of the Potentilla fruticosa shrub meadow;where the PPFD are higher than 1,200μmol·m^(-2)·s^(-1).The carbon dioxide uptake rates of the two ecosystems declined as air temperature increased,but the carbon dioxide uptake rate of the Kobresia humilis meadow decreased more quickly(-0.086)than that of the Potentilla fruticosa shrub meadow(-0.016).Soil moistures exert influence on the soil respirations and this varies with the vegetation type.The daily carbon dioxide absorptions of the ecosystems increase with increased diurnal temperature differences and higher diurnal temperature differences result in higher carbon dioxide exchanges.There exists a negative correlation between the vegetation albedos and the carbon dioxide fluxes.
