Considering a detailed hydrologic model in the land surface scheme helps to improve the simulation of regional hydro-climatology. A hydrologic model, which includes spatial heterogeneities in precipitation and infiltr...Considering a detailed hydrologic model in the land surface scheme helps to improve the simulation of regional hydro-climatology. A hydrologic model, which includes spatial heterogeneities in precipitation and infiltration, is constructed and incorporated into the land surface scheme BATS. Via the coupled-model (i.e., a regional climate model) simulations, the following major conclusions are obtained: the simulation of surface hydrology is sensitive to the inclusion of heterogeneities in precipitation and infiltration; the runoff ratio is increased after considering the infiltration heterogeneity, a result which is more consistent with the observations of surface moisture balance over humid areas; the introduction of the parameterization of infiltration heterogeneity can have a greater influence on the regional hydro-climatology than the precipitation heterogeneity; and the consideration of the impermeable fraction for the region reveals some features that are closer to the trend of aridification over northern China.展开更多
Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that to...Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that topography,as a proxy for resource availability,plays an important role in shaping tree species distributions in tropical forests.However,the association between growth stages and habitats types has not been considered in this analysis.Our aim was to examine the differences among different habitat types to determine whether tree species show similar species-habitat associations at young and mature life stages.Methods We used multivariate regression tree analysis to examined species-habitat associations among eight topographically defined habitats.The results were tested with a torus-translation test and canonical correspondence analysis(CCA)for 74 species in a 15 ha karst tropi-cal seasonal rain forest at the Nonggang National Natural Reserve in south China.We considered two life stages(young and mature)of trees species that showed a positive association with topography.Important Findings We found marked differences in community characteristics and number of associations among the eight habitats.Of the 74 species subjected to torus-translation test,63 had significant positive and 70 had significant negative associations with one or more of the eight habitats.Positive associations were more frequent in higher elevation habitats and negative associations were more frequent in lower eleva-tion habitats.This suggests that edaphic and hydrological variation related to topography play important roles in habitat partitioning in heterogeneous karst forests.For the 63 tree species with significant positive associations to at least one habitat,40 of them had the same positive association at young and mature life stages.The CCA revealed that the six topographic variables considered had consistent relation-ships with species distribution among all individuals and their two life stages.This indicates that most of t展开更多
According to the instantaneous growth rate (dN/dt) of E. coli CVCC249 growing in batch culture, the entire growth progress was distinguished into four phases: accelerating growth phase, constant growth phase, decelera...According to the instantaneous growth rate (dN/dt) of E. coli CVCC249 growing in batch culture, the entire growth progress was distinguished into four phases: accelerating growth phase, constant growth phase, decelerating growth phase; declining phase, in each of which obvious variation in physiological; biochemical properties was detected, including total DNA, total protein,; MTT-dehydrogenase activity, etc., that led to difference in their antibiotic susceptivity. Antibiotic susceptivity of the population sampled from each phase was tested by Concentration-killing Curve (CKC) approach following the formula N=N 0/{1+exp[r·(x-BC 50)]}, showing as normal distribution at the individual cell level for an internal population, in which the median bactericidal concentration BC 50 represents the mean level of susceptivity, while the bactericidal span BC 199=(2lnN 0)/r indicates the variation degree of the antibiotic susceptivity. Furthermore, tested by CKC approach, the antibiotic susceptivity of E. coli CVCC249 population in each physiological phase to gentamicin or enoxacin was various: susceptivity of the population in the constant growth phase; declining phase all increased compared with that in the accelerating growth phase for gentamicin but declined for enoxacin. The primary investigations revealed that the physiological phase should be taken into account in the context of antibiotic susceptivity; research into antimicrobial mechanism. However there are few reports concerned with this study. Further research using different kinds of antibiotics with synchronized continuous culture of different bacterial strains is required.展开更多
基金This work was jointly supported by the National Natural Science Foundation of China under Grant No. 40205012, and 40201048, the Chinese NKBRSF Project G1999043400 and the Foundation of the China Ministry of Education (Grant No. 20010284027). The computat
文摘Considering a detailed hydrologic model in the land surface scheme helps to improve the simulation of regional hydro-climatology. A hydrologic model, which includes spatial heterogeneities in precipitation and infiltration, is constructed and incorporated into the land surface scheme BATS. Via the coupled-model (i.e., a regional climate model) simulations, the following major conclusions are obtained: the simulation of surface hydrology is sensitive to the inclusion of heterogeneities in precipitation and infiltration; the runoff ratio is increased after considering the infiltration heterogeneity, a result which is more consistent with the observations of surface moisture balance over humid areas; the introduction of the parameterization of infiltration heterogeneity can have a greater influence on the regional hydro-climatology than the precipitation heterogeneity; and the consideration of the impermeable fraction for the region reveals some features that are closer to the trend of aridification over northern China.
基金National Natural Science Foundation of China(Grant Nos.31500342,31300359)the Guangxi Natural Science Foundation(2015GXNSFBA139050)the 2014‘Western Light’Project of the Chinese Academy of Sciences,and CFERN&GENE Award Funds on Ecological Paper.
文摘Aims Tropical and subtropical karst forests of south China are under increas-ing pressure from over-exploitation causing widespread habitat degra-dation and biodiversity loss.Previous research has demonstrated that topography,as a proxy for resource availability,plays an important role in shaping tree species distributions in tropical forests.However,the association between growth stages and habitats types has not been considered in this analysis.Our aim was to examine the differences among different habitat types to determine whether tree species show similar species-habitat associations at young and mature life stages.Methods We used multivariate regression tree analysis to examined species-habitat associations among eight topographically defined habitats.The results were tested with a torus-translation test and canonical correspondence analysis(CCA)for 74 species in a 15 ha karst tropi-cal seasonal rain forest at the Nonggang National Natural Reserve in south China.We considered two life stages(young and mature)of trees species that showed a positive association with topography.Important Findings We found marked differences in community characteristics and number of associations among the eight habitats.Of the 74 species subjected to torus-translation test,63 had significant positive and 70 had significant negative associations with one or more of the eight habitats.Positive associations were more frequent in higher elevation habitats and negative associations were more frequent in lower eleva-tion habitats.This suggests that edaphic and hydrological variation related to topography play important roles in habitat partitioning in heterogeneous karst forests.For the 63 tree species with significant positive associations to at least one habitat,40 of them had the same positive association at young and mature life stages.The CCA revealed that the six topographic variables considered had consistent relation-ships with species distribution among all individuals and their two life stages.This indicates that most of t
基金Supported by the Natural Science Foundation of Shandong Province, China (Grant No. Y2005C58)the Natural Key Technology R&D Program of China (Grant No. 2006BAK02A03-6)the Youth Scientific Research Foundation of Shandong Academy of Agricultural Science (2005YQ035)
文摘According to the instantaneous growth rate (dN/dt) of E. coli CVCC249 growing in batch culture, the entire growth progress was distinguished into four phases: accelerating growth phase, constant growth phase, decelerating growth phase; declining phase, in each of which obvious variation in physiological; biochemical properties was detected, including total DNA, total protein,; MTT-dehydrogenase activity, etc., that led to difference in their antibiotic susceptivity. Antibiotic susceptivity of the population sampled from each phase was tested by Concentration-killing Curve (CKC) approach following the formula N=N 0/{1+exp[r·(x-BC 50)]}, showing as normal distribution at the individual cell level for an internal population, in which the median bactericidal concentration BC 50 represents the mean level of susceptivity, while the bactericidal span BC 199=(2lnN 0)/r indicates the variation degree of the antibiotic susceptivity. Furthermore, tested by CKC approach, the antibiotic susceptivity of E. coli CVCC249 population in each physiological phase to gentamicin or enoxacin was various: susceptivity of the population in the constant growth phase; declining phase all increased compared with that in the accelerating growth phase for gentamicin but declined for enoxacin. The primary investigations revealed that the physiological phase should be taken into account in the context of antibiotic susceptivity; research into antimicrobial mechanism. However there are few reports concerned with this study. Further research using different kinds of antibiotics with synchronized continuous culture of different bacterial strains is required.
