Fourteen plots were chosen along with the altitude of 1600-2600 m in Guandi Mountain, Shanxi Province, China to investigate all the trees in the plots, and the species diversity indexes were calculated for analyzing t...Fourteen plots were chosen along with the altitude of 1600-2600 m in Guandi Mountain, Shanxi Province, China to investigate all the trees in the plots, and the species diversity indexes were calculated for analyzing the effects of altitudinal gradient on plant species diversity. The results showed that the order of dominant species from low altitude to high altitude is as Quercus liaotungensis Koidz, Pinus tabulaeformis, Betula platyphylla, B. albo-sinensis, Picea wilsonii, P. Meyeri and Larix principis-rupprechtii. With altitude increasing, the average height and DBH of the arbor firstly increase and then decrease, the maximal height and DBH of the arbor present the unimodal variable trend, the maximal height of coniferous and broad-leaved trees firstly increases and then decreases, the maximal DBH of broad-leaf trees has no clear fluctuation, and the maximal DBH of the needle-leaf trees decreases gradually. Moreover, in middle altitudinal communities （the altitude of 1900-2200 m）, the maximal height and DBH of the needle-leaf trees are larger than these of broad-leaf trees. Both Shannon-wiener index and Margalef index of the communities present the unimodal variable trend, with a peak in the mid-altitude. Plant species diversity in the mid-altitude （1900-2200 m） is higher than that of the low altitude （1600-1900 m） and the high altitude （2200-2600 m）. In addition, the unimodal variable trend of α species diversity is clearly correlated with the altitudinal gradient. The change of plant species diversity is significantly correlated with the altitudinal gradient, and also related to the community structure, the community composition, the feature of species and the human disturbance.展开更多
Electrocatalysis plays a vital role in technologies of energy and environment relevance,such as water electrolysis,fuel cells,synthesis of carbon and nitrogen-based fuels,etc.The volcano relations(VRs)are general and ...Electrocatalysis plays a vital role in technologies of energy and environment relevance,such as water electrolysis,fuel cells,synthesis of carbon and nitrogen-based fuels,etc.The volcano relations(VRs)are general and standard tools for predicting and understanding the activity trends of electrocatalysts.The modern electrocatalytic VRs are generally based on the kinetic models with the maximum free energy(△G^(0)_(max))of reaction steps as the rate-determining term(RDT),in which some important factors that crucially impact the reaction kinetics are missed,for examples,the surface structures and coverages of reaction intermediates and spectators,other free energy demanding steps than that associated with the △G^(0)_(max),and so on.In this perspective,we first give a brief introduction of the theoretical framework of current electrocatalytic VRs and the underlying problems in the oversimplifiedDG0max-based kinetic models,and then provide an account of our effort in constructing more rational VRs for electrocatalytic reactions.We introduce a new theoretical framework of electrocatalytic VRs based on kinetic model with the so-called energetic span(δE)serving as RDT.Since the surface-coverage effects and multiple free energy-demanding steps are considered,the VRs thus obtained show several new features such as strong potential dependence,asymmetric ascending and descending branches,relatively flat tops,and so on.The effectiveness of theδE-based VRs is verified for hydrogen and oxygen electrocatalytic reactions.Finally,research directions to further rationalize the electrocatalytic VRs are discussed.展开更多
Leaf morphological and stoichiometric characteristics are considered to represent both the interior inheritable characters in the plant and its adaptations to specific exterior environments. Rhododendron agglutinatum,...Leaf morphological and stoichiometric characteristics are considered to represent both the interior inheritable characters in the plant and its adaptations to specific exterior environments. Rhododendron agglutinatum,an evergreen alpine shrub species,occupies a wide range of habitats above timberline in the Miyaluo Natural Reserve,southwestern China. Along an altitudinal gradient ranging from 3700 to 4150 m,we measured leaf morphological characters including leaf dry matter content(LDMC),leaf dry mass per unit area(LMA),and one leaf area(OLA),as well as carbon(C) and nutrient(N,P) contents in leaves of three different age groups(juvenile leaves,mature leaves and senescent leaves). We also calculated the stoichiometric relationships among carbon and nutrients(C/N,C/P and N/P). Results showed thatboth age and altitude affected the leaf morphological and stoichiometric properties of R. agglutinatum. Mature leaves possessed the highest LDMC,LMA and C contents both on a dry mass basis and on a unit area basis. Younger leaves possessed higher contents of nutrients. OLA as well as ratios between carbon and nutrients(C/N,C/P) increased with ages. Juvenile leaves possessed lowest ratio between nitrogen and phosphorus. In juvenile leaves,nutrients increased with altitudinal elevation,whereas other traits decreased. In mature leaves,nutrients and their ratios with carbon showed consistent trends with juvenile leaves along increasing altitude,whereas LMA and carbon on a unit area basis showed opposite trends with juvenile leaves along increasing altitude. In senescent leaves,only content of phosphorus on a unit area basis and N/P were found linearly correlated with altitude. Our results demonstrated a clear pattern of nutrient distribution with aging process inleaves and indicated that a high possibility of N limitation in this region. We also concluded that younger leaves could be more sensitive to climate changes due to a greater altitudinal influence on the leaf traits in younger leaves than those in elder leaves.展开更多
The rockburst data of Huafeng and Da’anshan Mine were analysised in this paper. From the statistical results, we know that the relation between magnitude and frequency in rockburst is linear. Using this relation, the...The rockburst data of Huafeng and Da’anshan Mine were analysised in this paper. From the statistical results, we know that the relation between magnitude and frequency in rockburst is linear. Using this relation, the maximum magnitude and tendency of rockburst can be predicted.The theory can improve the quantitive prediction level in rockburst.展开更多
基金This paper was supported by Shanxi Natural Science Foun-dation (20001090)
文摘Fourteen plots were chosen along with the altitude of 1600-2600 m in Guandi Mountain, Shanxi Province, China to investigate all the trees in the plots, and the species diversity indexes were calculated for analyzing the effects of altitudinal gradient on plant species diversity. The results showed that the order of dominant species from low altitude to high altitude is as Quercus liaotungensis Koidz, Pinus tabulaeformis, Betula platyphylla, B. albo-sinensis, Picea wilsonii, P. Meyeri and Larix principis-rupprechtii. With altitude increasing, the average height and DBH of the arbor firstly increase and then decrease, the maximal height and DBH of the arbor present the unimodal variable trend, the maximal height of coniferous and broad-leaved trees firstly increases and then decreases, the maximal DBH of broad-leaf trees has no clear fluctuation, and the maximal DBH of the needle-leaf trees decreases gradually. Moreover, in middle altitudinal communities （the altitude of 1900-2200 m）, the maximal height and DBH of the needle-leaf trees are larger than these of broad-leaf trees. Both Shannon-wiener index and Margalef index of the communities present the unimodal variable trend, with a peak in the mid-altitude. Plant species diversity in the mid-altitude （1900-2200 m） is higher than that of the low altitude （1600-1900 m） and the high altitude （2200-2600 m）. In addition, the unimodal variable trend of α species diversity is clearly correlated with the altitudinal gradient. The change of plant species diversity is significantly correlated with the altitudinal gradient, and also related to the community structure, the community composition, the feature of species and the human disturbance.
文摘Electrocatalysis plays a vital role in technologies of energy and environment relevance,such as water electrolysis,fuel cells,synthesis of carbon and nitrogen-based fuels,etc.The volcano relations(VRs)are general and standard tools for predicting and understanding the activity trends of electrocatalysts.The modern electrocatalytic VRs are generally based on the kinetic models with the maximum free energy(△G^(0)_(max))of reaction steps as the rate-determining term(RDT),in which some important factors that crucially impact the reaction kinetics are missed,for examples,the surface structures and coverages of reaction intermediates and spectators,other free energy demanding steps than that associated with the △G^(0)_(max),and so on.In this perspective,we first give a brief introduction of the theoretical framework of current electrocatalytic VRs and the underlying problems in the oversimplifiedDG0max-based kinetic models,and then provide an account of our effort in constructing more rational VRs for electrocatalytic reactions.We introduce a new theoretical framework of electrocatalytic VRs based on kinetic model with the so-called energetic span(δE)serving as RDT.Since the surface-coverage effects and multiple free energy-demanding steps are considered,the VRs thus obtained show several new features such as strong potential dependence,asymmetric ascending and descending branches,relatively flat tops,and so on.The effectiveness of theδE-based VRs is verified for hydrogen and oxygen electrocatalytic reactions.Finally,research directions to further rationalize the electrocatalytic VRs are discussed.
基金supported by the National Natural Science Foundation of China (No.41071039)National Key Research and Development Program (No.2016YFC0502100)
文摘Leaf morphological and stoichiometric characteristics are considered to represent both the interior inheritable characters in the plant and its adaptations to specific exterior environments. Rhododendron agglutinatum,an evergreen alpine shrub species,occupies a wide range of habitats above timberline in the Miyaluo Natural Reserve,southwestern China. Along an altitudinal gradient ranging from 3700 to 4150 m,we measured leaf morphological characters including leaf dry matter content(LDMC),leaf dry mass per unit area(LMA),and one leaf area(OLA),as well as carbon(C) and nutrient(N,P) contents in leaves of three different age groups(juvenile leaves,mature leaves and senescent leaves). We also calculated the stoichiometric relationships among carbon and nutrients(C/N,C/P and N/P). Results showed thatboth age and altitude affected the leaf morphological and stoichiometric properties of R. agglutinatum. Mature leaves possessed the highest LDMC,LMA and C contents both on a dry mass basis and on a unit area basis. Younger leaves possessed higher contents of nutrients. OLA as well as ratios between carbon and nutrients(C/N,C/P) increased with ages. Juvenile leaves possessed lowest ratio between nitrogen and phosphorus. In juvenile leaves,nutrients increased with altitudinal elevation,whereas other traits decreased. In mature leaves,nutrients and their ratios with carbon showed consistent trends with juvenile leaves along increasing altitude,whereas LMA and carbon on a unit area basis showed opposite trends with juvenile leaves along increasing altitude. In senescent leaves,only content of phosphorus on a unit area basis and N/P were found linearly correlated with altitude. Our results demonstrated a clear pattern of nutrient distribution with aging process inleaves and indicated that a high possibility of N limitation in this region. We also concluded that younger leaves could be more sensitive to climate changes due to a greater altitudinal influence on the leaf traits in younger leaves than those in elder leaves.
文摘The rockburst data of Huafeng and Da’anshan Mine were analysised in this paper. From the statistical results, we know that the relation between magnitude and frequency in rockburst is linear. Using this relation, the maximum magnitude and tendency of rockburst can be predicted.The theory can improve the quantitive prediction level in rockburst.
