[Objective] This study aimed to investigate the influences of grazing and fencing on grassland productivity and carrying capacity of subtropical natural warmtemperature tussock. [Method] With the natural warm temperat...[Objective] This study aimed to investigate the influences of grazing and fencing on grassland productivity and carrying capacity of subtropical natural warmtemperature tussock. [Method] With the natural warm temperature tussock in Longli County of Guizhou Province as study area, monthly, seasonal and annual dynamics of grassland productivity were investigate continuously during 2010 -2012, and the data were analyzed. [Result] Under grazing and fencing conditions, grassland present biomass and forage growth of warm temperature tussock in Longli County of Guizhou Province both increased first and decreased, reaching the maximum from August to October. Fencing significantly improved the productivity of natural grassland but had little effect on the vegetation composition. [Conclusion] From the perspective of grass-livestock balance, the suitable stocking capacity of warm-temperature tussock in the central region of Guizhou Province was 3.45 -4.66 sheep/hm2 , which has high ecological efficiency and can be borne by farmers and herdsmen.展开更多
This paper provides the information on nesting biology of 20 bird species in alpine shrub (4000-4700 m a.s.l.) or alpine meadow-wasteland habitats (4300-4700 m a.s.l.) in Lhasa region,Tibet.Of these species,three are ...This paper provides the information on nesting biology of 20 bird species in alpine shrub (4000-4700 m a.s.l.) or alpine meadow-wasteland habitats (4300-4700 m a.s.l.) in Lhasa region,Tibet.Of these species,three are endemic to the Tibetan plateau and 17 widespread in altitudes.The data on these taxa are all new to the high-altitude environments,especially the upper limit of their breeding distribution.A few species are firstly reported with respect to nesting information in the world.The study will contribute our knowledge for natural history of birds occurring in the harsh,extreme habitats.展开更多
To solve the problem of lack of water in arid areas and barren soil in the process of ecological restoration, the growth and drought resistance of Sainfoin （Onobrychis vidifolia Scop.） was studied by inoculation of ...To solve the problem of lack of water in arid areas and barren soil in the process of ecological restoration, the growth and drought resistance of Sainfoin （Onobrychis vidifolia Scop.） was studied by inoculation of AMF （arbuscular rnycorrhizal fungi）, under drought stress. The results show that the inoculation of AMF can significantly improve the growth and mycorrhizal infection rate of Sainfoin and accelerate the absorption of water and nutrients by the roots compared with uninoculated plants. On the 40th day under drought stress, the relative water content, total nitrogen and total phosphorus content of the leaves of inoculated plants increased by 7.27%, 4.21% and 2.40%, respectively, the osmotic adjustment property in plant cells was improved, the protective enzyme system was improved and membrane lipid peroxida- tion was reduced. The inoculation of AMF can slow down the damage from drought, improve the drought resistance of Sainfoin, and will be of great significance to the ecologic restoration in arid areas.展开更多
The identification of easily measured plant functional types (PFTs) that consistently predict grazing response would be a major advance.The responses to grazing of individual traits and PFTs were analyzed along a graz...The identification of easily measured plant functional types (PFTs) that consistently predict grazing response would be a major advance.The responses to grazing of individual traits and PFTs were analyzed along a grazing gradient in an alpine shrub meadow on the Qinghai-Tibet Plateau,China.Three response types were identified;grazing increaser (GI),grazing decreaser (GD),and neutral (NE) for both traits and PFTs.Seven traits were measured:plant height,economic group,cotyledon type,plant inclination,growth form,life cycle,and vegetative structure.The first five were significantly affected by grazing.Ordinal regressions for grazing response of the seven traits showed that the best single predictors of response were growth form (including the attributes "Scattered","Bunched" or "Closely Bunched"),and plant inclination ("Rosette","Prostrate",or "Erect"),followed by economic group ("Shrub","Grass","Sedge","Legume","Forb",or "Harmful") and plant height ("Tall","Medium",or "Small").Within the four optimal traits,the summed dominance ratio (SDR) of small plants,forbs,rosette and bunched plants,invariably increased,while that of tall plants,shrubs,grasses,and erect plants decreased,when grazing pressure was enhanced.Canonical correspondence analysis (CCA) identified eleven explanatory PFTs based on 195 defined PFTs,by combining the different attributes of the four optimal traits.Among explanatory PFTs,the most valuable in predicting the community response to grazing were Tall×Shrub×Erect×Scattered and Small×Forb×Rosette,as these have the closest connections with grazing disturbance and include fewer species.Species richness,diversity,and community evenness,did not differ among grazing treatments because turnover occurred in component species and their relative abundances along the grazing gradient.We have demonstrated that a minimum set of PFTs resulting from optimal individual traits can provide consistent prediction of community responses to grazing in this region.This approach provides a more accurate indicator of change within a changing environment than do univariate measures of species diversity.We hope to provide a link between management practices and vegetation structure,forming a basis for future,large scale,plant trait comparisons.展开更多
Recent experiment has shown that the ABC-stacked trilayer graphene-boron nitride Moire super-lattice at half-filling is a Mort insulator. Based on symmetry analysis and effective band structure calculation, we propose...Recent experiment has shown that the ABC-stacked trilayer graphene-boron nitride Moire super-lattice at half-filling is a Mort insulator. Based on symmetry analysis and effective band structure calculation, we propose a valley-contrasting chiral tight-binding model with local Coulomb interaction to describe this Moire super-lattice system. By matching the positions of van Hove points in the low-energy effective bands, the valley-contrasting staggered flux per triangle is determined around π/2. When the valence band is half-filled, the Fermi surfaces are found to be perfectly nested between the two valleys. Such an effect can induce an inter-valley spiral order with a gap in the charge excitations, indicating that the Mott insulating behavior observed in the trilayer graphene-boron nitride Moire super-lattice results predominantly from the inter-valley scattering,展开更多
Arbuscular mycorrhizal fungi(AMF)can increase host plant nutrient uptake via their mycelium,thus promoting plant growth.AMF have always been associated with successful invasion of most exotic plant species.However,kno...Arbuscular mycorrhizal fungi(AMF)can increase host plant nutrient uptake via their mycelium,thus promoting plant growth.AMF have always been associated with successful invasion of most exotic plant species.However,knowledge regarding how AMF affect the success of plant invasion remains limited.Exotic Ambrosia artemisiifolia is an invasive and mycorrhizal plant species.A long-term field experiment was conducted to examine the differences in AMF diversity and composition in the roots of A.artemisiifolia and Setaria viridis subjected to interspecific competition during growth.A greenhouse experiment was also performed to test the effect of Funneliformis mosseae on the growth of these two species.Ambrosia artemisiifolia invasion caused AMF diversity to change in native S.viridis roots.Meanwhile,the relative abundance of F.mosseae was significantly higher in the roots of A.artemisiifolia than in those of S.viridis.The higher AMF colonization rate in the exotic species(A.artemisiifolia)than in the native species(S.viridis)was found in both the field and greenhouse experiments.The greenhouse experiment possibly provided that AMF advantaged to the growth of A.artemisiifolia,by influencing its photosynthetic capacity as well as its phosphorus and potassium absorption.These observations highlight the important relationship of AMF with the successful invasion of A.artemisiifolia.展开更多
Bush encroachment is widely distributed in arid and semi-arid regions, and it has a serious impact on livestock production, especially in Africa where livestock is a primary source for the livelihoods of many people. ...Bush encroachment is widely distributed in arid and semi-arid regions, and it has a serious impact on livestock production, especially in Africa where livestock is a primary source for the livelihoods of many people. In this study, methods of supervised classification and decision tree classification, and indexes of a land use change significance index（Ci） and a single land use dynamic degree, were applied to remote sensing imagery of Ethiopia for 1986–2016. The results show the dynamic characteristics of grassland bush encroachment in low altitude areas（pastures 1500 m above sea level） of Ethiopia in the 30 year period studied. The results revealed several interesting features of this phenomenon.（1） The area of bush encroachment showed an increasing trend, with a maximum of 3.74×10^3 km^2 in 2003, which represented 68.97% of the total area, and declined slightly from 2003~2016.（2） Among classification types, the area of severe shrub grassland was the largest, accounting for 28.36–49.10% of the total area, while the area of moderate bush encroachment accounted for 9.77–16.68%, and slight bush encroachment accounted for 5.52–7.57%.（3） The expansion rate of shrubby grassland was 0.74% for the 30 year period, while the average annual expansion rate was 2.16% for the 8 years from 1995–2003.（4） Forest land and grassland were the two main land use types of shrub grassland transformation in low altitude areas and bush encroachment changed large amounts of forest land into grassland due to shrub grassland management. The results of this study provide basic data for revealing the impacts of development processes on subsequent bush encroachment and can inform better management for the sustainable development of grasslands in low altitude systems.展开更多
Aims Classical theory predicts that herbivores impact herb assemblages and soil nitrogen(N)cycling through selective plant consumption and the deposition of N-rich waste,with effects dependent upon ecosystem N availab...Aims Classical theory predicts that herbivores impact herb assemblages and soil nitrogen(N)cycling through selective plant consumption and the deposition of N-rich waste,with effects dependent upon ecosystem N availability.Herbivores are predicted to accelerate N cycling when N availability is high and decelerate cycling when availability is low.However,experimental tests of these theories in natural systems are limited and have yielded contradictory results.California’s widespread chaparral shrublands provide a tractable system in which to test these theories.They are prone to periodic crown fire,which temporarily removes living shrub cover,deposits mineral N on soils and allows diverse herbaceous assemblages to dominate the landscape for 3–5 years.Chaparral is also increasingly vulnerable to herbaceous invasion;mammalian herbivory may limit the establishment of non-native herbs in the shrub understory.Methods We implemented a 2-year herbivore-exclosure experiment(Hopland,CA)to assess the impact of mammalian herbivory during early post-fire chaparral succession,both on herbaceous plant assemblages and soil N and C cycling.We predicted that,in high-N post-fire conditions,mammalian herbivory would not demonstrate a strong preference for N-fixing herbs,would accelerate N cycling and would reduce the abundance of non-native herbs.Important Findings Excluding mammalian herbivores increased herb standing biomass by 54%,but changed neither the relative abundance of N-fixing vs.non-N-fixing herbs nor any measure of N or C cycling.Herbivore impacts on nutrient cycling may not be significant over the 2-year time scale of the experiment and physical effects of herbivore activity could have counteracted the influence of plant litter and animal dung/urine inputs.Mammalian herbivores concentrated their feeding on typical non-native herbs,slightly decreasing their relative abundance;however,mammalian herbivory was not sufficient to stem the invasion of chaparral by invasive herbs or alter C and N cycling over the first 2 years after fire.展开更多
基金Supported by Project of Agricultural Research Project of Guizhou Province (QKHZ [2010] No.3045)Special Fund of Guizhou Academy of Agricultural Sciences (QNKYZX [2011] No.021)"Twelfth Five-Year" National Science and Technology Support Program (2011BAD17B03)~~
文摘[Objective] This study aimed to investigate the influences of grazing and fencing on grassland productivity and carrying capacity of subtropical natural warmtemperature tussock. [Method] With the natural warm temperature tussock in Longli County of Guizhou Province as study area, monthly, seasonal and annual dynamics of grassland productivity were investigate continuously during 2010 -2012, and the data were analyzed. [Result] Under grazing and fencing conditions, grassland present biomass and forage growth of warm temperature tussock in Longli County of Guizhou Province both increased first and decreased, reaching the maximum from August to October. Fencing significantly improved the productivity of natural grassland but had little effect on the vegetation composition. [Conclusion] From the perspective of grass-livestock balance, the suitable stocking capacity of warm-temperature tussock in the central region of Guizhou Province was 3.45 -4.66 sheep/hm2 , which has high ecological efficiency and can be borne by farmers and herdsmen.
基金the National Natural Sciences Foundation of China (Grant Nos. 39800016,30170156,30270216,30370241,30425036,30670337,and 30830019)
文摘This paper provides the information on nesting biology of 20 bird species in alpine shrub (4000-4700 m a.s.l.) or alpine meadow-wasteland habitats (4300-4700 m a.s.l.) in Lhasa region,Tibet.Of these species,three are endemic to the Tibetan plateau and 17 widespread in altitudes.The data on these taxa are all new to the high-altitude environments,especially the upper limit of their breeding distribution.A few species are firstly reported with respect to nesting information in the world.The study will contribute our knowledge for natural history of birds occurring in the harsh,extreme habitats.
基金provided by the Science and Technology Major Project of Shanxi Province (No. 20121101008), is gratefully acknowledged
文摘To solve the problem of lack of water in arid areas and barren soil in the process of ecological restoration, the growth and drought resistance of Sainfoin （Onobrychis vidifolia Scop.） was studied by inoculation of AMF （arbuscular rnycorrhizal fungi）, under drought stress. The results show that the inoculation of AMF can significantly improve the growth and mycorrhizal infection rate of Sainfoin and accelerate the absorption of water and nutrients by the roots compared with uninoculated plants. On the 40th day under drought stress, the relative water content, total nitrogen and total phosphorus content of the leaves of inoculated plants increased by 7.27%, 4.21% and 2.40%, respectively, the osmotic adjustment property in plant cells was improved, the protective enzyme system was improved and membrane lipid peroxida- tion was reduced. The inoculation of AMF can slow down the damage from drought, improve the drought resistance of Sainfoin, and will be of great significance to the ecologic restoration in arid areas.
基金supported by National Natural Science Foundation of China (Grant Nos. 30671490, and 31070382)
文摘The identification of easily measured plant functional types (PFTs) that consistently predict grazing response would be a major advance.The responses to grazing of individual traits and PFTs were analyzed along a grazing gradient in an alpine shrub meadow on the Qinghai-Tibet Plateau,China.Three response types were identified;grazing increaser (GI),grazing decreaser (GD),and neutral (NE) for both traits and PFTs.Seven traits were measured:plant height,economic group,cotyledon type,plant inclination,growth form,life cycle,and vegetative structure.The first five were significantly affected by grazing.Ordinal regressions for grazing response of the seven traits showed that the best single predictors of response were growth form (including the attributes "Scattered","Bunched" or "Closely Bunched"),and plant inclination ("Rosette","Prostrate",or "Erect"),followed by economic group ("Shrub","Grass","Sedge","Legume","Forb",or "Harmful") and plant height ("Tall","Medium",or "Small").Within the four optimal traits,the summed dominance ratio (SDR) of small plants,forbs,rosette and bunched plants,invariably increased,while that of tall plants,shrubs,grasses,and erect plants decreased,when grazing pressure was enhanced.Canonical correspondence analysis (CCA) identified eleven explanatory PFTs based on 195 defined PFTs,by combining the different attributes of the four optimal traits.Among explanatory PFTs,the most valuable in predicting the community response to grazing were Tall×Shrub×Erect×Scattered and Small×Forb×Rosette,as these have the closest connections with grazing disturbance and include fewer species.Species richness,diversity,and community evenness,did not differ among grazing treatments because turnover occurred in component species and their relative abundances along the grazing gradient.We have demonstrated that a minimum set of PFTs resulting from optimal individual traits can provide consistent prediction of community responses to grazing in this region.This approach provides a more accurate indicator of change within a changing environment than do univariate measures of species diversity.We hope to provide a link between management practices and vegetation structure,forming a basis for future,large scale,plant trait comparisons.
基金supported by the National Key Research and Development Program of MOST of China(2017YFA0302900)the National Natural Science Foundation of China(11474331)
文摘Recent experiment has shown that the ABC-stacked trilayer graphene-boron nitride Moire super-lattice at half-filling is a Mort insulator. Based on symmetry analysis and effective band structure calculation, we propose a valley-contrasting chiral tight-binding model with local Coulomb interaction to describe this Moire super-lattice system. By matching the positions of van Hove points in the low-energy effective bands, the valley-contrasting staggered flux per triangle is determined around π/2. When the valence band is half-filled, the Fermi surfaces are found to be perfectly nested between the two valleys. Such an effect can induce an inter-valley spiral order with a gap in the charge excitations, indicating that the Mott insulating behavior observed in the trilayer graphene-boron nitride Moire super-lattice results predominantly from the inter-valley scattering,
基金funded by the National Natural Science Foundation of China(grant no.31972343 and 31372000)Hebei National Natural Science Foundation(C2019201059)College of Life Science,Institute of Life Science and Green Development,Hebei University.
文摘Arbuscular mycorrhizal fungi(AMF)can increase host plant nutrient uptake via their mycelium,thus promoting plant growth.AMF have always been associated with successful invasion of most exotic plant species.However,knowledge regarding how AMF affect the success of plant invasion remains limited.Exotic Ambrosia artemisiifolia is an invasive and mycorrhizal plant species.A long-term field experiment was conducted to examine the differences in AMF diversity and composition in the roots of A.artemisiifolia and Setaria viridis subjected to interspecific competition during growth.A greenhouse experiment was also performed to test the effect of Funneliformis mosseae on the growth of these two species.Ambrosia artemisiifolia invasion caused AMF diversity to change in native S.viridis roots.Meanwhile,the relative abundance of F.mosseae was significantly higher in the roots of A.artemisiifolia than in those of S.viridis.The higher AMF colonization rate in the exotic species(A.artemisiifolia)than in the native species(S.viridis)was found in both the field and greenhouse experiments.The greenhouse experiment possibly provided that AMF advantaged to the growth of A.artemisiifolia,by influencing its photosynthetic capacity as well as its phosphorus and potassium absorption.These observations highlight the important relationship of AMF with the successful invasion of A.artemisiifolia.
基金China–Africa Joint Research Centre Project of the Chinese Academy of Sciences(SAJC201610)Science and Technology partnership ProgramMinistry of Science and Technology of China(KY201702010)
文摘Bush encroachment is widely distributed in arid and semi-arid regions, and it has a serious impact on livestock production, especially in Africa where livestock is a primary source for the livelihoods of many people. In this study, methods of supervised classification and decision tree classification, and indexes of a land use change significance index（Ci） and a single land use dynamic degree, were applied to remote sensing imagery of Ethiopia for 1986–2016. The results show the dynamic characteristics of grassland bush encroachment in low altitude areas（pastures 1500 m above sea level） of Ethiopia in the 30 year period studied. The results revealed several interesting features of this phenomenon.（1） The area of bush encroachment showed an increasing trend, with a maximum of 3.74×10^3 km^2 in 2003, which represented 68.97% of the total area, and declined slightly from 2003~2016.（2） Among classification types, the area of severe shrub grassland was the largest, accounting for 28.36–49.10% of the total area, while the area of moderate bush encroachment accounted for 9.77–16.68%, and slight bush encroachment accounted for 5.52–7.57%.（3） The expansion rate of shrubby grassland was 0.74% for the 30 year period, while the average annual expansion rate was 2.16% for the 8 years from 1995–2003.（4） Forest land and grassland were the two main land use types of shrub grassland transformation in low altitude areas and bush encroachment changed large amounts of forest land into grassland due to shrub grassland management. The results of this study provide basic data for revealing the impacts of development processes on subsequent bush encroachment and can inform better management for the sustainable development of grasslands in low altitude systems.
基金by the Joint Fire Science Program(GRIN 17-2-01-8)National Science Foundation(GRFP 2014177815)+1 种基金Philomathia Foundation,Garden Club of America Ecological Restoration FellowshipThe Stephens Lab(UC Berkeley)and Department of Integrative Biology(UC Berkeley).
文摘Aims Classical theory predicts that herbivores impact herb assemblages and soil nitrogen(N)cycling through selective plant consumption and the deposition of N-rich waste,with effects dependent upon ecosystem N availability.Herbivores are predicted to accelerate N cycling when N availability is high and decelerate cycling when availability is low.However,experimental tests of these theories in natural systems are limited and have yielded contradictory results.California’s widespread chaparral shrublands provide a tractable system in which to test these theories.They are prone to periodic crown fire,which temporarily removes living shrub cover,deposits mineral N on soils and allows diverse herbaceous assemblages to dominate the landscape for 3–5 years.Chaparral is also increasingly vulnerable to herbaceous invasion;mammalian herbivory may limit the establishment of non-native herbs in the shrub understory.Methods We implemented a 2-year herbivore-exclosure experiment(Hopland,CA)to assess the impact of mammalian herbivory during early post-fire chaparral succession,both on herbaceous plant assemblages and soil N and C cycling.We predicted that,in high-N post-fire conditions,mammalian herbivory would not demonstrate a strong preference for N-fixing herbs,would accelerate N cycling and would reduce the abundance of non-native herbs.Important Findings Excluding mammalian herbivores increased herb standing biomass by 54%,but changed neither the relative abundance of N-fixing vs.non-N-fixing herbs nor any measure of N or C cycling.Herbivore impacts on nutrient cycling may not be significant over the 2-year time scale of the experiment and physical effects of herbivore activity could have counteracted the influence of plant litter and animal dung/urine inputs.Mammalian herbivores concentrated their feeding on typical non-native herbs,slightly decreasing their relative abundance;however,mammalian herbivory was not sufficient to stem the invasion of chaparral by invasive herbs or alter C and N cycling over the first 2 years after fire.
