In this study,short-term gully retreat was monitored from the active gullies selected in representative black soil area,using differential global positioning system(GPS).With the support of geographic information syst...In this study,short-term gully retreat was monitored from the active gullies selected in representative black soil area,using differential global positioning system(GPS).With the support of geographic information system(GIS),multi-temporal digital elevation models(DEM) were constructed from the data collected by GPS and used for further analysis.Based on the analysis of multi-temporal DEM,we discussed the erosion-deposition characteristics within gully and a developing model for black soil gully area of Northeast China was proposed.The results are:(1) The analysis of the monitored gully data in 2004 indicated that the retreat of gully head reached more than 10 m,gully area extended 170-400 m2,net gully eroded volume 220-320 m3,and gully erosion modulus 2200-4800 t?km?2?a?1.(2) Compared with the mature gully the initial gully grows rapidly,and its erosion parameters are relatively large.The erosion parameters have not only to do with flow energy,but also with the growth phase.(3) There are significant seasonal differences in gully erosion parameters.The extension of gully area and width dominates in winter and spring without marked net erosion while changes mainly occur in gully head and net erosion in rainy season.(4) It is remarkable for freeze-thaw erosion in the black soil area of NE China.The gully wall of SG2 extended 0.45 m under freeze-thaw effect in 2004,and the distance of gully head retreated maximally 6.4 m.(5) Due to freeze-thaw action and snowmelt,gully is primarily in the interior adjustment process in winter and early spring.There are much more depositions compared with that during rainy season,which can almost happen throughout the gully,while erosion mostly occurs near head,esp.for gullies having a relatively long history of development.On the other hand,the process of energy exchange with exterior dominates in rainy season.It is considered that this cyclic process is an important mechanism for gully growth in high latitude or/and high attitude regions.展开更多
Long time monitoring is acquired to obtain the displacement data for displacement-based geotechnical material back analysis, and these data are hard to be measured under some special condition, such as earthquake. For...Long time monitoring is acquired to obtain the displacement data for displacement-based geotechnical material back analysis, and these data are hard to be measured under some special condition, such as earthquake. For a simple homogeneous slope, the position of a critical failure surface is determined by value of c/tan ~b. Utilizing upper bound theorem of limit analysis, the external work rate and internal energy for normal slope under earthquake forces are given, and the formula for minimum safety factor is derived. On this basis, the equation of slip surface and the surface depth of a given position are solved. In this way, the strength parameter can be analyzed by known slip surface depth. For practical use, the surface depth for a given slope under varying strength parameter is presented. Finally, two examples are given to show its simplicity and effectiveness.展开更多
The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have...The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have been drawn; the difference of calibration results between Hokkaido and Honshu region in Japan is investigated. And calibration results of different directions, different epicenter distances and different magnitudes are probed into. The result shows that the location of earthquakes on the Shanghai seismic array is greatly improved.展开更多
Within the context of a never ended Cold War in the energy field, the discoveries of natural gas resources in the Southern Eastern Mediterranean definitely create new impetus for the resolution of the longstanding Cyp...Within the context of a never ended Cold War in the energy field, the discoveries of natural gas resources in the Southern Eastern Mediterranean definitely create new impetus for the resolution of the longstanding Cyprus issues. After the failure of the last negotiations talks in July 2017, there is common strategic reason that calls for a mutually accepted resolution among all the parties involved. The situation calls to put aside national feelings and the burden of history and move forward. What is of crucial importance is not only the maintenance of international peace and regional stability but also the enhancement of the welfare of the people of this turbulent region. Whether the path of reason will be followed is remained to be seen.展开更多
Peucedanum aucheri Boiss. (Apiaceae) is a herbaceous wild plant native to Iran and is used in Iranian folk medicine as a diuretic and for the treatment of kidney disorders. Phytochemical investigation of different e...Peucedanum aucheri Boiss. (Apiaceae) is a herbaceous wild plant native to Iran and is used in Iranian folk medicine as a diuretic and for the treatment of kidney disorders. Phytochemical investigation of different extracts prepared from the aerial part of P. aucheri Boiss. resulted to the isolation of two main flavonol glycosides from methanolic extract. Using comprehensive spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and mass spectroscopy, chemical structure of isolated compounds were determined as kaempfrol-3-o-rutinoside (nicotiflorin) and isorhamnetin-3-o-rutinoside (narcissin). Although narcissin has previously been isolated from P. ruthenicum, to the best of our knowledge, isolation of nicotiflorin from Peucedanum genus is reported for the first time.展开更多
Carbon (C) stocks and sequestration rates were determined for oak-hickory forests in Ohio, USA. The models we developed show that the patterns of C sequestration rates follow what we expect in total and merchantable...Carbon (C) stocks and sequestration rates were determined for oak-hickory forests in Ohio, USA. The models we developed show that the patterns of C sequestration rates follow what we expect in total and merchantable volume increment. The current annual increment (CAI) and the mean annual increment (MAI) peaks at ages 23 and 46 years, respectively, for total aboveground C. The peak CAI and MAI for the aboveground C peaks at ages 26 and 53 years, respectively. The 5-year periodic MAI for both total aboveground C and aboveground portion of merchantable trees occurs at age 30 years, occurring simultaneously with the 5-year periodic MAI for total and merchantable volume. Knowing that C sequestration occurs in similar patterns to volume growth is helpful in transitioning from traditional volume-based management to carbon-based management.展开更多
Aims Seasonal variations in species richness,aboveground net primary productivity(ANPP)and stability under resource enrichment are frequently ignored.This study explores how the impacts of resource enrichment on speci...Aims Seasonal variations in species richness,aboveground net primary productivity(ANPP)and stability under resource enrichment are frequently ignored.This study explores how the impacts of resource enrichment on species richness,ANPP and stability vary among seasons in semi-arid grasslands.Methods We conducted a 3-year experiment in an Inner Mongolia grassland to determine the effects of resource input(water[W],nitrogen[N])on species richness,community ANPP and stability using seasonal sampling during the growing season(2013–2015).Structural equation modeling(SEM)was used to examine the relative importance of resource input on community stability via mechanistic pathways in each month and the whole growing season.Important Findings Resource inputs did not affect community ANPP in May and June,while N and/or NW enhanced ANPP in July and August.Resource inputs generally did not affect species richness,asynchrony or community stability in most of the time.Positive responses of perennial bunchgrasses(PB)to N and/or NW treatments contributed to the increased community ANPP in July and August.Species asynchrony may be the major mechanism contributing to community stability in May and June and the entire growing season,and PB stability is potentially the primary factor controlling community stability in July and August under resource enrichment.Our results indicate that season and resource availability could interact to regulate species richness,community ANPP and stability in semi-arid grasslands.These findings have important implications for management practices in semi-arid grasslands in order to mitigate the impact of land use and global change.展开更多
Nitrogen(N)deposition,precipitation and their interaction affect plant invasions in temperate ecosystems with limiting N and water resources,but whether and how they affect plant invasions in subtropical native commun...Nitrogen(N)deposition,precipitation and their interaction affect plant invasions in temperate ecosystems with limiting N and water resources,but whether and how they affect plant invasions in subtropical native communities with abundant N and precipitation remains unclear.We constructed in situ artificial communities with 12 common native plant species in a subtropical system and introduced four common invasive plant species and their native counterparts to these communities.We compared plant growth and establishment of introduced invasive species and native counterparts in communities exposed to ambient(CK),N addition(N+),increased precipitation(P+)and N addition plus increased precipitation(P+N+).We also investigated the density and aboveground biomass of communities under such conditions.P+alone did not enhance the performance of invasive species or native counterparts.N+enhanced only the aboveground biomass and relative density of invasive species.P+N+enhanced the growth and establishment performance of both invasive species and native counterparts.Most growth and establishment parameters of invasive species were greater than those of native counterparts under N+,P+and P+N+conditions.The density and aboveground biomass of native communities established by invasive species were significantly lower than those of native communities established by native counterparts under P+N+conditions.These results suggest that P+may magnify the effects of N+on performance of invasive species in subtropical native communities where N and water are often abundant,which may help to understand the effect of global change on plant invasion in subtropical ecosystems.展开更多
基金Key Project for National Natural Science Foundation of China,No.40235056The Ph.D. Programs Foundation of Ministry of Education of China, No.20030027015+3 种基金China Postdoctoral Science Foundation,No.20070410482Doctoral Foundation of University of Jinan,No.B0620National Natural Science Foundation of China,No.40672158Key Subject Foundation Supported by Shandong Province
文摘In this study,short-term gully retreat was monitored from the active gullies selected in representative black soil area,using differential global positioning system(GPS).With the support of geographic information system(GIS),multi-temporal digital elevation models(DEM) were constructed from the data collected by GPS and used for further analysis.Based on the analysis of multi-temporal DEM,we discussed the erosion-deposition characteristics within gully and a developing model for black soil gully area of Northeast China was proposed.The results are:(1) The analysis of the monitored gully data in 2004 indicated that the retreat of gully head reached more than 10 m,gully area extended 170-400 m2,net gully eroded volume 220-320 m3,and gully erosion modulus 2200-4800 t?km?2?a?1.(2) Compared with the mature gully the initial gully grows rapidly,and its erosion parameters are relatively large.The erosion parameters have not only to do with flow energy,but also with the growth phase.(3) There are significant seasonal differences in gully erosion parameters.The extension of gully area and width dominates in winter and spring without marked net erosion while changes mainly occur in gully head and net erosion in rainy season.(4) It is remarkable for freeze-thaw erosion in the black soil area of NE China.The gully wall of SG2 extended 0.45 m under freeze-thaw effect in 2004,and the distance of gully head retreated maximally 6.4 m.(5) Due to freeze-thaw action and snowmelt,gully is primarily in the interior adjustment process in winter and early spring.There are much more depositions compared with that during rainy season,which can almost happen throughout the gully,while erosion mostly occurs near head,esp.for gullies having a relatively long history of development.On the other hand,the process of energy exchange with exterior dominates in rainy season.It is considered that this cyclic process is an important mechanism for gully growth in high latitude or/and high attitude regions.
基金Project(2013CB036004) supported by the National Basic Research Program of ChinaProject(51178468) supported by the National Natural Science Foundation of ChinaProject(2013zzts047) supported by the Fundamental Research Funds for Central Universities,China
文摘Long time monitoring is acquired to obtain the displacement data for displacement-based geotechnical material back analysis, and these data are hard to be measured under some special condition, such as earthquake. For a simple homogeneous slope, the position of a critical failure surface is determined by value of c/tan ~b. Utilizing upper bound theorem of limit analysis, the external work rate and internal energy for normal slope under earthquake forces are given, and the formula for minimum safety factor is derived. On this basis, the equation of slip surface and the surface depth of a given position are solved. In this way, the strength parameter can be analyzed by known slip surface depth. For practical use, the surface depth for a given slope under varying strength parameter is presented. Finally, two examples are given to show its simplicity and effectiveness.
基金the State Key Marine Geological Laboratory of Tongji University,China
文摘The paper proposes the calibration theory and methods for the Shanghai seismic array and analyzes the calibration results. As a result, the calibration results for the seismic array based on 2 typical earthquakes have been drawn; the difference of calibration results between Hokkaido and Honshu region in Japan is investigated. And calibration results of different directions, different epicenter distances and different magnitudes are probed into. The result shows that the location of earthquakes on the Shanghai seismic array is greatly improved.
文摘Within the context of a never ended Cold War in the energy field, the discoveries of natural gas resources in the Southern Eastern Mediterranean definitely create new impetus for the resolution of the longstanding Cyprus issues. After the failure of the last negotiations talks in July 2017, there is common strategic reason that calls for a mutually accepted resolution among all the parties involved. The situation calls to put aside national feelings and the burden of history and move forward. What is of crucial importance is not only the maintenance of international peace and regional stability but also the enhancement of the welfare of the people of this turbulent region. Whether the path of reason will be followed is remained to be seen.
文摘Peucedanum aucheri Boiss. (Apiaceae) is a herbaceous wild plant native to Iran and is used in Iranian folk medicine as a diuretic and for the treatment of kidney disorders. Phytochemical investigation of different extracts prepared from the aerial part of P. aucheri Boiss. resulted to the isolation of two main flavonol glycosides from methanolic extract. Using comprehensive spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and mass spectroscopy, chemical structure of isolated compounds were determined as kaempfrol-3-o-rutinoside (nicotiflorin) and isorhamnetin-3-o-rutinoside (narcissin). Although narcissin has previously been isolated from P. ruthenicum, to the best of our knowledge, isolation of nicotiflorin from Peucedanum genus is reported for the first time.
基金McIntire-Stennis Funds allocated through the McIntire-Stennis Forestry Research Act, USA (OHO00037-MS)
文摘Carbon (C) stocks and sequestration rates were determined for oak-hickory forests in Ohio, USA. The models we developed show that the patterns of C sequestration rates follow what we expect in total and merchantable volume increment. The current annual increment (CAI) and the mean annual increment (MAI) peaks at ages 23 and 46 years, respectively, for total aboveground C. The peak CAI and MAI for the aboveground C peaks at ages 26 and 53 years, respectively. The 5-year periodic MAI for both total aboveground C and aboveground portion of merchantable trees occurs at age 30 years, occurring simultaneously with the 5-year periodic MAI for total and merchantable volume. Knowing that C sequestration occurs in similar patterns to volume growth is helpful in transitioning from traditional volume-based management to carbon-based management.
基金This work was supported by the National Natural Science Foundation of China(31630010 and 31320103916).
文摘Aims Seasonal variations in species richness,aboveground net primary productivity(ANPP)and stability under resource enrichment are frequently ignored.This study explores how the impacts of resource enrichment on species richness,ANPP and stability vary among seasons in semi-arid grasslands.Methods We conducted a 3-year experiment in an Inner Mongolia grassland to determine the effects of resource input(water[W],nitrogen[N])on species richness,community ANPP and stability using seasonal sampling during the growing season(2013–2015).Structural equation modeling(SEM)was used to examine the relative importance of resource input on community stability via mechanistic pathways in each month and the whole growing season.Important Findings Resource inputs did not affect community ANPP in May and June,while N and/or NW enhanced ANPP in July and August.Resource inputs generally did not affect species richness,asynchrony or community stability in most of the time.Positive responses of perennial bunchgrasses(PB)to N and/or NW treatments contributed to the increased community ANPP in July and August.Species asynchrony may be the major mechanism contributing to community stability in May and June and the entire growing season,and PB stability is potentially the primary factor controlling community stability in July and August under resource enrichment.Our results indicate that season and resource availability could interact to regulate species richness,community ANPP and stability in semi-arid grasslands.These findings have important implications for management practices in semi-arid grasslands in order to mitigate the impact of land use and global change.
基金funded by the National Natural Science Foundation of China(31460165,31960282)Natural Science Foundation of Guangxi Province(2018GXNSFAA281112)Guangxi Key Laboratory of Plant Conservation and Restoration Ecology in Karst Terrain(19-050-6).
文摘Nitrogen(N)deposition,precipitation and their interaction affect plant invasions in temperate ecosystems with limiting N and water resources,but whether and how they affect plant invasions in subtropical native communities with abundant N and precipitation remains unclear.We constructed in situ artificial communities with 12 common native plant species in a subtropical system and introduced four common invasive plant species and their native counterparts to these communities.We compared plant growth and establishment of introduced invasive species and native counterparts in communities exposed to ambient(CK),N addition(N+),increased precipitation(P+)and N addition plus increased precipitation(P+N+).We also investigated the density and aboveground biomass of communities under such conditions.P+alone did not enhance the performance of invasive species or native counterparts.N+enhanced only the aboveground biomass and relative density of invasive species.P+N+enhanced the growth and establishment performance of both invasive species and native counterparts.Most growth and establishment parameters of invasive species were greater than those of native counterparts under N+,P+and P+N+conditions.The density and aboveground biomass of native communities established by invasive species were significantly lower than those of native communities established by native counterparts under P+N+conditions.These results suggest that P+may magnify the effects of N+on performance of invasive species in subtropical native communities where N and water are often abundant,which may help to understand the effect of global change on plant invasion in subtropical ecosystems.