The investigation was conducted on the spatial and temporal distributions of soil organic mater （SOM） in the mixed plantations of alder （Aluns crernastogyne） and cypress （Cupressus funebris ） （MPAC）, which dis...The investigation was conducted on the spatial and temporal distributions of soil organic mater （SOM） in the mixed plantations of alder （Aluns crernastogyne） and cypress （Cupressus funebris ） （MPAC）, which distributed in the hilly areas of central Sichuan Basin （HACSB）. The results show that： （1） the spatial distribution of SOM among different sites at the same age are not significant before 15-year-old, but significant at 20-year-old, and not significant again after 25-year-old; （2） the SOM contents in 0-15 cm and 15-30 cm layers increase sharply from 10- to 15-year-old, and decline gradually from 15- to 30- year-old; the SOM contents of the 30-year-old PCP were 80. 38% and 78.42% higher than that of the 10-year-old, but 29.16% and 53.37% lower than that of 15-year-old in the 0-15 cm and 15-30 cm layers, respectively. The decrease of SOM contents would lead to the degradation of soil fertility and the decline of forest productivity.展开更多
By means of analysing the historical data of flood-drought grade series in the past 2000 years(A.D.0-1900),especially in the last 5000 years (1470-1900) , this paper revealed the spatial-temporaldistribution features ...By means of analysing the historical data of flood-drought grade series in the past 2000 years(A.D.0-1900),especially in the last 5000 years (1470-1900) , this paper revealed the spatial-temporaldistribution features of severe flood and drought in Yellow River Valley. Statistical methods of varianceanalysis, probability transition and the principles of scale correspondence were employed tocomprehensively predicate 90's tendency of severe flood and drought in the Yellow River Valley. In addi-tion, this paper pointed out the possible breaching dikes, sectors and the flooding ranges by future's se-vere flood, meanwhile estimating the associated economic losses and impact to environment.展开更多
By using RS and GIS technology,the ecological risk index ( ERI) was constructed based on the analysis of land use change and structural characteristics in urbanization watershed of Songhua River in Harbin section. Aft...By using RS and GIS technology,the ecological risk index ( ERI) was constructed based on the analysis of land use change and structural characteristics in urbanization watershed of Songhua River in Harbin section. Afterwards,the spatial distribution and change characteristics maps of ERI obtained by using block Kriging were analyzed to reveal the spatial and temporal evolution characteristics,change rules and formation mechanisms of ecological risk based on land use under the background of urbanization,and to minimize land use risk during urbanization process. The results showed that during the past 18 years,moderate ecological risk level was major,while proportion of high ecological risk was the lowest,and the area of higher and lower ecological risk region changed most greatly; high and higher ecological risk were focused on urban region and the transition zone from urban to suburban region,while low and lower ecological risk mainly distributed in forestland with higher vegetation coverage,water bodies,grassland,shrub land and so on. Meanwhile,the transition zone from high to low ecological risk was very obvious. In addition,ecological risk became slightly worse in some region due to the transformation from cropland to residential and urban land,while it became slightly better in other regions because of the transformation from cropland to forestland; the center of gravity in lower ecological risk region shifted most greatly,while the shift was the smallest in high ecological risk region,namely 12. 31 and 0. 57 km respectively.展开更多
文摘The investigation was conducted on the spatial and temporal distributions of soil organic mater （SOM） in the mixed plantations of alder （Aluns crernastogyne） and cypress （Cupressus funebris ） （MPAC）, which distributed in the hilly areas of central Sichuan Basin （HACSB）. The results show that： （1） the spatial distribution of SOM among different sites at the same age are not significant before 15-year-old, but significant at 20-year-old, and not significant again after 25-year-old; （2） the SOM contents in 0-15 cm and 15-30 cm layers increase sharply from 10- to 15-year-old, and decline gradually from 15- to 30- year-old; the SOM contents of the 30-year-old PCP were 80. 38% and 78.42% higher than that of the 10-year-old, but 29.16% and 53.37% lower than that of 15-year-old in the 0-15 cm and 15-30 cm layers, respectively. The decrease of SOM contents would lead to the degradation of soil fertility and the decline of forest productivity.
文摘By means of analysing the historical data of flood-drought grade series in the past 2000 years(A.D.0-1900),especially in the last 5000 years (1470-1900) , this paper revealed the spatial-temporaldistribution features of severe flood and drought in Yellow River Valley. Statistical methods of varianceanalysis, probability transition and the principles of scale correspondence were employed tocomprehensively predicate 90's tendency of severe flood and drought in the Yellow River Valley. In addi-tion, this paper pointed out the possible breaching dikes, sectors and the flooding ranges by future's se-vere flood, meanwhile estimating the associated economic losses and impact to environment.
基金Supported by the National"863"Project(2006AA12Z104)Natural Science Foundation of Heilongjiang Province,China(F201137)Natural Science Foundation for Distinguished Young Scholars of Heilongjiang University(QL200640)
文摘By using RS and GIS technology,the ecological risk index ( ERI) was constructed based on the analysis of land use change and structural characteristics in urbanization watershed of Songhua River in Harbin section. Afterwards,the spatial distribution and change characteristics maps of ERI obtained by using block Kriging were analyzed to reveal the spatial and temporal evolution characteristics,change rules and formation mechanisms of ecological risk based on land use under the background of urbanization,and to minimize land use risk during urbanization process. The results showed that during the past 18 years,moderate ecological risk level was major,while proportion of high ecological risk was the lowest,and the area of higher and lower ecological risk region changed most greatly; high and higher ecological risk were focused on urban region and the transition zone from urban to suburban region,while low and lower ecological risk mainly distributed in forestland with higher vegetation coverage,water bodies,grassland,shrub land and so on. Meanwhile,the transition zone from high to low ecological risk was very obvious. In addition,ecological risk became slightly worse in some region due to the transformation from cropland to residential and urban land,while it became slightly better in other regions because of the transformation from cropland to forestland; the center of gravity in lower ecological risk region shifted most greatly,while the shift was the smallest in high ecological risk region,namely 12. 31 and 0. 57 km respectively.
