During January to February in 2008,severe ice-snows occurred on 2.09×10^6 km^2 of south China and caused tremendous damage to the forests.Stem damage and crown debris input from the ice-snow in a Cunninghamia lan...During January to February in 2008,severe ice-snows occurred on 2.09×10^6 km^2 of south China and caused tremendous damage to the forests.Stem damage and crown debris input from the ice-snow in a Cunninghamia lanceolata stand in northern Guangdong Province,China,were investigated to determine the extent of ice-snow damage to trees and the nutrient distribution characteristics on woodland.Icicles were produced on branches and leaves of the C.lanceolata trees by sleets,resulting in all live trees were damaged by stem breakage.A strong positive correlation was found between the broken position of trees and diameter at breast height（DBH）.Nutrient concentrations varied according to components of crown debris.Total nutrient concentration graded in the following order：leaves 〉stembark 〉branches 〉stemwood.Crown debris input from ice-snows was 19.11 t·ha^-2,and branches,stemwood,leaves and stembark accounted for 37%,28%,27% and 8%,respectively.Nutrient distributions between components of crown debris differed drastically in 2008.The contribution of leaves to total nutrient accumulation of crown debris was 70%,whereas branches,stemwood and stembark contributed 13%,7% and 10%,respectively.Accumulations of N,P and K by the woodland were 105 067.9 t·ha^-2 in 2008,and the nutrients of crown debris,litter and the stand soil accounted for 0.18%,0.03% and 99.79%,respectively.The order of nutrient accumulation in leaves,branches,stembark,stemwood of crown debris and litter was N〉K〉P,but the nutrients stored in the soil were in the order of K 〉N 〉P.The N and P concentrations of litter in 2009 were greater than those in 2008,whereas its K concentration was smaller than that of the latter.N and P concentrations of stemwood and stembark in 2009 were slightly greater than those in 2009,whereas their K concentration was smaller than the latter.The N and P accumulations of stemwood and stembark of crown debris in 2009 were close to those in 2008,whereas their K accumulation was slightly smaller than the latter.The N,P and K accumulations of litter in 2009 was greater than those in 2008.展开更多
The ice melting performance of three types of deicers, including sodium chloride, calcium chloride and sodium acetate, were tested in laboratory under different temperature conditions, and their effects on asphalt mix...The ice melting performance of three types of deicers, including sodium chloride, calcium chloride and sodium acetate, were tested in laboratory under different temperature conditions, and their effects on asphalt mixture were evaluated from the point of the stripping resistance of asphalt mixture. Unsaturated Marshall samples were exposed to freeze-thaw cycling while immersed in the deicer solutions of different concentrations. After the freeze-thaw cycles, Cantabro tests were performed, and Cantabro loss was adopted to characterize the stripping resistance of asphalt mixture. The test results show that calcium chloride has the best comprehensive ice melting performance, and all deicers have detrimental effect on the stripping resistance of asphalt mixture at different degrees. The damage degree depends on deicer types and their concentration in the solution. Deicer solutions with about 2% concentration cause the greatest loss of stripping resistance due to serious freeze-thaw damage. Sodium acetate causes greater loss of stripping resistance than sodium chloride and calcium chloride at the same concentration.展开更多
Since 194os, Mount Uludag （Bithynian Olympus） has been considered famous with winter sports center in Turkey. In addition, it is one of the rare places because of its plant diversity and is also one of the important...Since 194os, Mount Uludag （Bithynian Olympus） has been considered famous with winter sports center in Turkey. In addition, it is one of the rare places because of its plant diversity and is also one of the important plant areas of Turkey. The ski run constructions are rapidly increased in the past decades in the alpine and subalpine belts of the mountain. Rate of nitrogen mineralization and some properties of soft were investigated in the soils of the three ski runs and undisturbed neighborhood forest sites. These ski runs are at the upper part of the forest belt in the mountain. Abies bornmuelleriana forest community is the postclimax and very sensitive to destruetion. The rates of the nitrogen mineralization in the soils were determined in controlled conditions （60% water-holding capacity, 20℃）. Nitrification and nitrogen mineralization were in the ski run inside where the natural recovery started, increased compared with the outside of the ski runs. Waterholding capacity, organic carbon, and total nitrogen were decreased in the massive damaged ski run, and due to these changes, the rates of mineralization and nitrification were also decreased.展开更多
A phytosociological study of a weed community dominated by Hydrocotyle mannii and Centella asiatica was carried out in Kampala, the capital city of Uganda from 2000 to 2002. The Zurich-Montpellier School of Phytosocio...A phytosociological study of a weed community dominated by Hydrocotyle mannii and Centella asiatica was carried out in Kampala, the capital city of Uganda from 2000 to 2002. The Zurich-Montpellier School of Phytosociology method was used with special emphasis on floristic and synecological structure as well as on dynamic aspects. This community was found to grow on shady moist roadsides and is about 15 cm high. In total, 54 species were recorded; most of them are annual, anemochorous and widespread. The Hydrocotyle mannii and Centella asiatica community is described as a new weed association： Hydocotylo-Centelletum asiaticae Mosango ass. nova.. Hydrocotyle mannii, Centella asiatica, Dichondra repens and Sida veronicifolia have been recognized as the character species of this association. The Hydrocotylo-Centelletum is a pioneer association. It has been ascribed to the alliance Eleusinion indicae Leonard 1950 which includes plant communities growing on shady roadsides. In terms of ecological succession, it appears to be evolving to the Asystasia gangetica herbaceous fallow association which belongs to the alliance Panicion maximi. It belongs to the order Ruderali-Euphorbietalia Schmitz 1971 and the class Ruderali-Manihotetea Leonard in Taton 1949.展开更多
Aims Species diversity–productivity relationships in natural ecosystems have been well documented in the literature.However,biotic and abiotic factors that determine their relationships are still poorly understood,es...Aims Species diversity–productivity relationships in natural ecosystems have been well documented in the literature.However,biotic and abiotic factors that determine their relationships are still poorly understood,especially under future climate change scenarios.Methods Randomized block factorial experiments were performed in three meadows along an elevational gradient on Yulong Mountain,China,where open-top chambers and urea fertilizer manipulations were used to simulate warming and nitrogen addition,respectively.Besides species diversity,we measured functional diversity based on five traits:plant height,specific leaf area and leaf carbon,nitrogen and phosphorus contents.Several abiotic factors relating to climate(air temperature and precipitation)and soil chemistry(pH,organic carbon concentration,total nitrogen concentration and phosphorus concentration)were also measured.Generalized linear mixed-effect models were used to investigate the responses of species diversity and productivity to elevation,warming,nitrogen addition and their interactions.The effects of biotic and abiotic factors on the direction and magnitude of their relationship were also assessed.Important Findings Species diversity decreased with increasing elevation and declined under warming at mid-elevation,while productivity decreased with increasing elevation.Functional richness,maximum air temperature,soil pH and their interactions showed strong but negative influences on the species diversity–productivity relationship;the relationship shifted from positive to neutral and then to slightly negative as these sources of variation increased.Our study highlights the negative effects of short-term warming on species diversity and emphasizes the importance of both biotic and abiotic drivers of species diversity–productivity relationships in mountain meadow communities.展开更多
文摘During January to February in 2008,severe ice-snows occurred on 2.09×10^6 km^2 of south China and caused tremendous damage to the forests.Stem damage and crown debris input from the ice-snow in a Cunninghamia lanceolata stand in northern Guangdong Province,China,were investigated to determine the extent of ice-snow damage to trees and the nutrient distribution characteristics on woodland.Icicles were produced on branches and leaves of the C.lanceolata trees by sleets,resulting in all live trees were damaged by stem breakage.A strong positive correlation was found between the broken position of trees and diameter at breast height（DBH）.Nutrient concentrations varied according to components of crown debris.Total nutrient concentration graded in the following order：leaves 〉stembark 〉branches 〉stemwood.Crown debris input from ice-snows was 19.11 t·ha^-2,and branches,stemwood,leaves and stembark accounted for 37%,28%,27% and 8%,respectively.Nutrient distributions between components of crown debris differed drastically in 2008.The contribution of leaves to total nutrient accumulation of crown debris was 70%,whereas branches,stemwood and stembark contributed 13%,7% and 10%,respectively.Accumulations of N,P and K by the woodland were 105 067.9 t·ha^-2 in 2008,and the nutrients of crown debris,litter and the stand soil accounted for 0.18%,0.03% and 99.79%,respectively.The order of nutrient accumulation in leaves,branches,stembark,stemwood of crown debris and litter was N〉K〉P,but the nutrients stored in the soil were in the order of K 〉N 〉P.The N and P concentrations of litter in 2009 were greater than those in 2008,whereas its K concentration was smaller than that of the latter.N and P concentrations of stemwood and stembark in 2009 were slightly greater than those in 2009,whereas their K concentration was smaller than the latter.The N and P accumulations of stemwood and stembark of crown debris in 2009 were close to those in 2008,whereas their K accumulation was slightly smaller than the latter.The N,P and K accumulations of litter in 2009 was greater than those in 2008.
基金The Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120092110053)
文摘The ice melting performance of three types of deicers, including sodium chloride, calcium chloride and sodium acetate, were tested in laboratory under different temperature conditions, and their effects on asphalt mixture were evaluated from the point of the stripping resistance of asphalt mixture. Unsaturated Marshall samples were exposed to freeze-thaw cycling while immersed in the deicer solutions of different concentrations. After the freeze-thaw cycles, Cantabro tests were performed, and Cantabro loss was adopted to characterize the stripping resistance of asphalt mixture. The test results show that calcium chloride has the best comprehensive ice melting performance, and all deicers have detrimental effect on the stripping resistance of asphalt mixture at different degrees. The damage degree depends on deicer types and their concentration in the solution. Deicer solutions with about 2% concentration cause the greatest loss of stripping resistance due to serious freeze-thaw damage. Sodium acetate causes greater loss of stripping resistance than sodium chloride and calcium chloride at the same concentration.
基金supported by the United Nations Development,Global Environment Facility,Small Grants Programme
文摘Since 194os, Mount Uludag （Bithynian Olympus） has been considered famous with winter sports center in Turkey. In addition, it is one of the rare places because of its plant diversity and is also one of the important plant areas of Turkey. The ski run constructions are rapidly increased in the past decades in the alpine and subalpine belts of the mountain. Rate of nitrogen mineralization and some properties of soft were investigated in the soils of the three ski runs and undisturbed neighborhood forest sites. These ski runs are at the upper part of the forest belt in the mountain. Abies bornmuelleriana forest community is the postclimax and very sensitive to destruetion. The rates of the nitrogen mineralization in the soils were determined in controlled conditions （60% water-holding capacity, 20℃）. Nitrification and nitrogen mineralization were in the ski run inside where the natural recovery started, increased compared with the outside of the ski runs. Waterholding capacity, organic carbon, and total nitrogen were decreased in the massive damaged ski run, and due to these changes, the rates of mineralization and nitrification were also decreased.
文摘A phytosociological study of a weed community dominated by Hydrocotyle mannii and Centella asiatica was carried out in Kampala, the capital city of Uganda from 2000 to 2002. The Zurich-Montpellier School of Phytosociology method was used with special emphasis on floristic and synecological structure as well as on dynamic aspects. This community was found to grow on shady moist roadsides and is about 15 cm high. In total, 54 species were recorded; most of them are annual, anemochorous and widespread. The Hydrocotyle mannii and Centella asiatica community is described as a new weed association： Hydocotylo-Centelletum asiaticae Mosango ass. nova.. Hydrocotyle mannii, Centella asiatica, Dichondra repens and Sida veronicifolia have been recognized as the character species of this association. The Hydrocotylo-Centelletum is a pioneer association. It has been ascribed to the alliance Eleusinion indicae Leonard 1950 which includes plant communities growing on shady roadsides. In terms of ecological succession, it appears to be evolving to the Asystasia gangetica herbaceous fallow association which belongs to the alliance Panicion maximi. It belongs to the order Ruderali-Euphorbietalia Schmitz 1971 and the class Ruderali-Manihotetea Leonard in Taton 1949.
基金This study was financially supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB31000000)the National Natural Science Foundation of China(31500335).
文摘Aims Species diversity–productivity relationships in natural ecosystems have been well documented in the literature.However,biotic and abiotic factors that determine their relationships are still poorly understood,especially under future climate change scenarios.Methods Randomized block factorial experiments were performed in three meadows along an elevational gradient on Yulong Mountain,China,where open-top chambers and urea fertilizer manipulations were used to simulate warming and nitrogen addition,respectively.Besides species diversity,we measured functional diversity based on five traits:plant height,specific leaf area and leaf carbon,nitrogen and phosphorus contents.Several abiotic factors relating to climate(air temperature and precipitation)and soil chemistry(pH,organic carbon concentration,total nitrogen concentration and phosphorus concentration)were also measured.Generalized linear mixed-effect models were used to investigate the responses of species diversity and productivity to elevation,warming,nitrogen addition and their interactions.The effects of biotic and abiotic factors on the direction and magnitude of their relationship were also assessed.Important Findings Species diversity decreased with increasing elevation and declined under warming at mid-elevation,while productivity decreased with increasing elevation.Functional richness,maximum air temperature,soil pH and their interactions showed strong but negative influences on the species diversity–productivity relationship;the relationship shifted from positive to neutral and then to slightly negative as these sources of variation increased.Our study highlights the negative effects of short-term warming on species diversity and emphasizes the importance of both biotic and abiotic drivers of species diversity–productivity relationships in mountain meadow communities.
