Aims Desert ecosystems are often characterized by patchy distribution of vascular plants,with biological soil crusts(BSC)covering interplant spaces.However,few studies have comprehensively examined the linkage between...Aims Desert ecosystems are often characterized by patchy distribution of vascular plants,with biological soil crusts(BSC)covering interplant spaces.However,few studies have comprehensively examined the linkage between BSC and vascular plants through nitrogen(N)or element translocation.the objective of this study was to evaluate the ecological roles of BSC on N translocation from soil to the domi-nant herb Erodium oxyrrhynchum bieb.(geraniaceae)in a temper-ate desert in China.Methods Isotopes(including 15N-glu,15N-NH4Cl and 15N-NaNo3)were used as a tracer to detect translocation of N in two types of desert soil(BSC covered;bare)to the dominant herb E.oxyrrhynchum.three different forms of 15N-enriched N compounds were applied as a point source to small patches of BSC and to bare soil.and we measured isotopes(14N and 15N)and obtained the concentration of labeled-15N in both vascular plants and soils at different distances from substrate application Important Findings Plants of E.oxyrrhynchum growing in BSC-covered plots accumulated moreδ15N than those growing in the bare soil.similarly,soil from b Ccovered plots showed a higher concentration of labeled-N irrespective of form of isotope,than did the bare soil.the concentration of dissolved organic N(15N-glu)in E.oxyrrhynchum was higher than that of dis-solved inorganic N(15N-NH4Cl and 15N-NaNo3).soil covered by BSC also accumulated considerably more dissolved organic N than bare soil,whereas the dominant form of 15N concentrated in bare soil was dissolved inorganic N.Correlation analysis showed that the concentra-tion of labeled-N in plants was positively related to the concentration of labeled-N in soils and the N%recorded in E.oxyrrhynchum.our study supports the hypothesis that BSC facilitates ^(15)N translocation in soils and vascular plants in a temperate desert of northwestern China.展开更多
We develop a fractional-degree expectation dependence which is the generalization of the first-degree and second-degree expectation dependence.The motivation for introducing such a dependence notion is to conform with...We develop a fractional-degree expectation dependence which is the generalization of the first-degree and second-degree expectation dependence.The motivation for introducing such a dependence notion is to conform with the preferences of decision makers who are mostly risk averse but would be risk seeking at some wealth levels.We investigate some tractable equivalent properties for this new dependence notion,and explore its properties,including the invariance under increasing and concave transformations,and the invariance under convolution.We also extend our results to a combined fractional-degree expectation dependence notion includingε-almost firstdegree expectation dependence.Two applications on portfolio diversification problem and optimal investment in the presence of a background risk illustrate the usefulness of the approaches proposed in the present paper.展开更多
基金National Basic Research Program of China(2014CB954202)the West Light Foundation of the Chinese Academy of Sciences(RCPY201101)the Xinjiang Province Outstanding Youth Talent Project(2013711013).
文摘Aims Desert ecosystems are often characterized by patchy distribution of vascular plants,with biological soil crusts(BSC)covering interplant spaces.However,few studies have comprehensively examined the linkage between BSC and vascular plants through nitrogen(N)or element translocation.the objective of this study was to evaluate the ecological roles of BSC on N translocation from soil to the domi-nant herb Erodium oxyrrhynchum bieb.(geraniaceae)in a temper-ate desert in China.Methods Isotopes(including 15N-glu,15N-NH4Cl and 15N-NaNo3)were used as a tracer to detect translocation of N in two types of desert soil(BSC covered;bare)to the dominant herb E.oxyrrhynchum.three different forms of 15N-enriched N compounds were applied as a point source to small patches of BSC and to bare soil.and we measured isotopes(14N and 15N)and obtained the concentration of labeled-15N in both vascular plants and soils at different distances from substrate application Important Findings Plants of E.oxyrrhynchum growing in BSC-covered plots accumulated moreδ15N than those growing in the bare soil.similarly,soil from b Ccovered plots showed a higher concentration of labeled-N irrespective of form of isotope,than did the bare soil.the concentration of dissolved organic N(15N-glu)in E.oxyrrhynchum was higher than that of dis-solved inorganic N(15N-NH4Cl and 15N-NaNo3).soil covered by BSC also accumulated considerably more dissolved organic N than bare soil,whereas the dominant form of 15N concentrated in bare soil was dissolved inorganic N.Correlation analysis showed that the concentra-tion of labeled-N in plants was positively related to the concentration of labeled-N in soils and the N%recorded in E.oxyrrhynchum.our study supports the hypothesis that BSC facilitates ^(15)N translocation in soils and vascular plants in a temperate desert of northwestern China.
文摘We develop a fractional-degree expectation dependence which is the generalization of the first-degree and second-degree expectation dependence.The motivation for introducing such a dependence notion is to conform with the preferences of decision makers who are mostly risk averse but would be risk seeking at some wealth levels.We investigate some tractable equivalent properties for this new dependence notion,and explore its properties,including the invariance under increasing and concave transformations,and the invariance under convolution.We also extend our results to a combined fractional-degree expectation dependence notion includingε-almost firstdegree expectation dependence.Two applications on portfolio diversification problem and optimal investment in the presence of a background risk illustrate the usefulness of the approaches proposed in the present paper.
