Desert plants take on unique physiologically adaptive mechanisms in response to an adverse environment. In this study, we determined the concentrations of leaf nitrogen(N), phosphorus(P), and calcium(Ca) fraction for ...Desert plants take on unique physiologically adaptive mechanisms in response to an adverse environment. In this study, we determined the concentrations of leaf nitrogen(N), phosphorus(P), and calcium(Ca) fraction for dominant species of Artemisia ordosica, A. frigida, Calligonum mongolicum, and Oxytropis aciphylla in the Alxa Desert and discussed seasonal changes of their leaf N:P ratio and Ca fraction. The results showed that, from May to September, the N:P ratios of A. ordosica and C. mongolicum gradually and significantly increased, while those of A. frigida, and O. aciphylla had an increase trend that was not significant; the physiologically active Ca of A. ordosica and A. frigida increased significantly,while that of C. mongolicum and O. aciphylla decreased significantly. The physiologically inert calcium of C. mongolicum increased extremely significantly, while that of others was not significant. There was a significantly positive correlation between the N:P ratio and physiologically active Ca for A. ordosica, and the N:P ratio was significantly and negatively correlated with physiologically active Ca for O. aciphylla. These findings revealed that the physiological regulation mechanism was different for the plants either in earlier stage or later stage of plant-community succession.展开更多
Shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to...Shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to 30% is characterized mainly by multifarious shrubs because herbaceous species are strongly restricted by the extreme drought climate,wind erosion,overgrazing and sand burial.Patterns in shrub species richness and species abundance in relation to environmental conditions were examined by DCA(detrended correspondence analysis) and interpreted by a biplot.The rela-tionships between species diversity and environmental factors were examined using regression analyses.Our results show that the distributions of the shrub species in response to environmental conditions can be grouped into four ecological types,corresponding with the biological traits of the shrubs and their responses to the gradients of soil texture and soil water content.Patterns in species richness and species abundance were mainly determined by the deeper soil water content,instead of the soil texture as hypothesized by numerous studies in semiarid grasslands.With exception of the deeper soil water content,soil organic matter and total N content were positively correlated with species abundance,while pH was negatively correlated with it.These findings imply that it is vital for cur-rent shrub diversity conservation to reduce agricultural water use in the middle reaches of the Heihe River,which supplies water for the lower reaches in the western parts of the plateau,and to reduce the amount of groundwater exploitation and urban and oasis water use,to increase the water supply from Helan Mountain to the eastern desert of the Alxa Plateau.展开更多
基金supported by the National Key R&D Program of China (2016YFC0500706)
文摘Desert plants take on unique physiologically adaptive mechanisms in response to an adverse environment. In this study, we determined the concentrations of leaf nitrogen(N), phosphorus(P), and calcium(Ca) fraction for dominant species of Artemisia ordosica, A. frigida, Calligonum mongolicum, and Oxytropis aciphylla in the Alxa Desert and discussed seasonal changes of their leaf N:P ratio and Ca fraction. The results showed that, from May to September, the N:P ratios of A. ordosica and C. mongolicum gradually and significantly increased, while those of A. frigida, and O. aciphylla had an increase trend that was not significant; the physiologically active Ca of A. ordosica and A. frigida increased significantly,while that of C. mongolicum and O. aciphylla decreased significantly. The physiologically inert calcium of C. mongolicum increased extremely significantly, while that of others was not significant. There was a significantly positive correlation between the N:P ratio and physiologically active Ca for A. ordosica, and the N:P ratio was significantly and negatively correlated with physiologically active Ca for O. aciphylla. These findings revealed that the physiological regulation mechanism was different for the plants either in earlier stage or later stage of plant-community succession.
基金Supported by National Key Technology R & D Program (Grant Nos. 2007BAD46B03, 2006BAD26B0201)National Natural Science Foundation of China (Gant No. 40825001)
文摘Shrub species are considered the dominant plants in arid desert ecosystems,unlike in semiarid steppe zones or in grassland ecosystems.On the Alxa Plateau,northern China,sparse vegetation with cover ranging from 15% to 30% is characterized mainly by multifarious shrubs because herbaceous species are strongly restricted by the extreme drought climate,wind erosion,overgrazing and sand burial.Patterns in shrub species richness and species abundance in relation to environmental conditions were examined by DCA(detrended correspondence analysis) and interpreted by a biplot.The rela-tionships between species diversity and environmental factors were examined using regression analyses.Our results show that the distributions of the shrub species in response to environmental conditions can be grouped into four ecological types,corresponding with the biological traits of the shrubs and their responses to the gradients of soil texture and soil water content.Patterns in species richness and species abundance were mainly determined by the deeper soil water content,instead of the soil texture as hypothesized by numerous studies in semiarid grasslands.With exception of the deeper soil water content,soil organic matter and total N content were positively correlated with species abundance,while pH was negatively correlated with it.These findings imply that it is vital for cur-rent shrub diversity conservation to reduce agricultural water use in the middle reaches of the Heihe River,which supplies water for the lower reaches in the western parts of the plateau,and to reduce the amount of groundwater exploitation and urban and oasis water use,to increase the water supply from Helan Mountain to the eastern desert of the Alxa Plateau.
