Under conditions of a warmer climate,the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems.However,the above- and below-ground live biomass allocations among...Under conditions of a warmer climate,the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems.However,the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated.To determine the altitudinal patterns of above-/below-ground carbon allocation,we measured the root biomass and estimated the above-ground biomass(AGB) in a subalpine forest,treeline forest,alpine shrub,and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet.The AGB strongly declined with increasing elevation,which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain.The fine root biomass(FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest,whereas the coarse root biomass changed little with increasing altitudes,which led to a stable below-ground biomass(BGB) value across altitudes.Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland.Consequently,the root toshoot biomass ratio increased sharply with altitude,which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra.Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones,which should be considered when estimating carbon dynamics with shifting treelines.展开更多
Detrital minerals of 137 offshore and 22 river sediment samples collected from Qingdao coastal areas have been analyzed. Four mineral assemblage provinces can be classified by Q-mode cluster analysis. Factor analysis ...Detrital minerals of 137 offshore and 22 river sediment samples collected from Qingdao coastal areas have been analyzed. Four mineral assemblage provinces can be classified by Q-mode cluster analysis. Factor analysis identifies two major factors that account for the total variability in most common minerals: 1) based on the relationship of quartz, hornblende, actinolite, micas, and authigenic pyrite, 41.55% of the variability is related to sediment sources; 2) based on the relationship of epidote, garnet, sphere, and ilmenite, 23.21% can be related to strong hydrodynamic conditions that control transport and sedimentation. By comparing mineral compositions of river waters in the study area, the following four mineral provenances can be identified. The Qingdao-Laoshan nearshore area has a quartz-feldspar-epidote-hornblende-limenite-limonite-sphene assemblage, which is largely attributed to relict sediment and coastal erosion. The Jimo-Haiyang nearshore area has a quartz-feldspar-hornblende-epidote-limonite-mica-actinolite assemblage, derived largely from the Wulong River and Rushan River, and is also affected by the Huanghe River, while the Qianliyan Island area in the deeper offshore area separated by a mud belt has a similar assemblage. The Haiyang-Rushan nearshore area has a quartz-feldspar-hornblende-epidote-micas-limonite assemblage, indicating multiple sources from the Rushan River, the Wulong River, the Huanghe River, and coastal erosion. The central area, located in an eddy center, has a mica-authigenic pyrite-hornblende-quartz-feldspar assemblage, indicating multiple sources dominated by Huanghe River distal sediments.展开更多
Despite concerted efforts to create employment opportunities and the realized economic growth between 2000 and 2005, the unemployment rate in Namibia currently stands at 27.4%, according to the Labour Force Survey rel...Despite concerted efforts to create employment opportunities and the realized economic growth between 2000 and 2005, the unemployment rate in Namibia currently stands at 27.4%, according to the Labour Force Survey released in April 2013. The percentage of employed males in Namibia stands at 41.6% while that of employed females stand at 28.8% according to the National Human Resources Plan of May 2013. Analysts have put the blame on adverse climatic conditions, limited levels of skills, access to finance, and the structure of the economy. The frustration and discomfort caused by unemployment, especially among the youth, can threaten the country＇s peace and stability as it negatively impacts on the standard of living, crime rates, family happiness, and drug abuse.To date, studies on employment in Namibia have mainly concentrated on the micro and macro econometric approaches. It is important to examine how bio-demographic characteristics affect employment. This paper uses data from the 2010 Income and expenditure survey to establish the bio-demographic determinants of employment by fitting a binary logistic model. The outcome variable is employment status which is dichotomous. The independent variables which were guided by review of related literature and availability of data in the Income and Expenditure survey data set, included age-group, region, place of residence, marital status, education level, and gender. Results indicated that employment prospects in Namibia were influenced by the region, gender, marital status, and education level.展开更多
By using packed soil-core incubation experiments, we have studied stimulating effects of addition of external carbon （C） （glu- cose, 6.4 g C m 2） on heterotrophic respiration and microbial biomass C of a mature br...By using packed soil-core incubation experiments, we have studied stimulating effects of addition of external carbon （C） （glu- cose, 6.4 g C m 2） on heterotrophic respiration and microbial biomass C of a mature broadleaf and Korean pine mixed forest （BKPF） and an adjacent white birch forest （WBF） soil under different wetting intensities （55% and 80% WFPS, water-filled pore space） and nitrogen （N） supply （NH4C1 and KNO3, 4.5 g N m-e） conditions. The results showed that for the control, the cumulative carbon dioxide （CO2） flux from WBF soil during the 15-day incubation ranged from 5.44 to 5.82 g CO2-C m-2, which was significantly larger than that from BKPF soil （2.86 to 3.36 g CO2-C m 2）. With increasing wetting intensity, the cumulative CO2 flux from the control was decreased for the WBF soil, whereas an increase in the CO2 flux was observed in the BKPF soil （P 〈 0.05）. The addition of NH4C1 or KNO3 alone significantly reduced the cumulative CO2 fluxes by 9.2%-21.6 % from the two soils, especially from WBF soil at low wetting intensity. The addition of glucose alone significantly increased soil heterotrophic respiration, microbial biomass C （MBC）, and microbial metabolic quotient. The glucose-induced cumulative CO2 fluxes and soil MBC during the incubation ranged from 8.7 to 11.7 g CO2-C m-2 and from 7.4 to 23.9 g C m-2, which are larger than the dose of added C. Hence, the addition of external carbon can increase the decomposition of soil native organic C. The glucose-induced average and maximum rates of CO2 fluxes during the incubation were significantly in- fluenced by wetting intensity （WI） and vegetation type （VT）, and by WIxVT, NH4ClxVT and WIxVTxNH4C1 （P〈0.05）. The addition of NH4C1, instead of KNO3, significantly decreased the glucose-induced MBC of WBF soil （P〈0.05）, whereas adding NH4C1 and KNO3 both significantly increased the glucose-induced MBC of BKPF soil at high moisture （P〈0.05）. According to the differences in soil labile C pools, MBC and CO2 fluxes in the presence and absence of glucose, it can be concluded that the stimulating effects of glucose on soil heterotrophic respiration and MBC under temperate forests were dependent on vegetation type, soil moisture, and amount and type of the N added.展开更多
基金supported by the National Natural Science Foundation of China (41561011)the Natural Science Foundation of Jiangxi Province, China (20151BAB213029)
文摘Under conditions of a warmer climate,the advance of the alpine treeline into alpine tundra has implications for carbon dynamics in mountain ecosystems.However,the above- and below-ground live biomass allocations among different vegetation types within the treeline ecotones are not well investigated.To determine the altitudinal patterns of above-/below-ground carbon allocation,we measured the root biomass and estimated the above-ground biomass(AGB) in a subalpine forest,treeline forest,alpine shrub,and alpine grassland along two elevational transects towards the alpine tundra in southeast Tibet.The AGB strongly declined with increasing elevation,which was associated with a decrease in the leaf area index and a consequent reduction in carbon gain.The fine root biomass(FRB) increased significantly more in the alpine shrub and grassland than in the treeline forest,whereas the coarse root biomass changed little with increasing altitudes,which led to a stable below-ground biomass(BGB) value across altitudes.Warm and infertile soil conditions might explain the large amount of FRB in alpine shrub and grassland.Consequently,the root toshoot biomass ratio increased sharply with altitude,which suggested a remarkable shift of biomass allocation to root systems near the alpine tundra.Our findings demonstrate contrasting changes in AGB and BGB allocations across treeline ecotones,which should be considered when estimating carbon dynamics with shifting treelines.
基金the National Natural Science Foundation of China (Nos. 41376079, 41406081 and 41506107)Marine Geology Survey Project (Nos. GZH200900501 and GZH201100203)the Basic Fund of Ministry of Science Foundation of China (No. 2013FY112200)
文摘Detrital minerals of 137 offshore and 22 river sediment samples collected from Qingdao coastal areas have been analyzed. Four mineral assemblage provinces can be classified by Q-mode cluster analysis. Factor analysis identifies two major factors that account for the total variability in most common minerals: 1) based on the relationship of quartz, hornblende, actinolite, micas, and authigenic pyrite, 41.55% of the variability is related to sediment sources; 2) based on the relationship of epidote, garnet, sphere, and ilmenite, 23.21% can be related to strong hydrodynamic conditions that control transport and sedimentation. By comparing mineral compositions of river waters in the study area, the following four mineral provenances can be identified. The Qingdao-Laoshan nearshore area has a quartz-feldspar-epidote-hornblende-limenite-limonite-sphene assemblage, which is largely attributed to relict sediment and coastal erosion. The Jimo-Haiyang nearshore area has a quartz-feldspar-hornblende-epidote-limonite-mica-actinolite assemblage, derived largely from the Wulong River and Rushan River, and is also affected by the Huanghe River, while the Qianliyan Island area in the deeper offshore area separated by a mud belt has a similar assemblage. The Haiyang-Rushan nearshore area has a quartz-feldspar-hornblende-epidote-micas-limonite assemblage, indicating multiple sources from the Rushan River, the Wulong River, the Huanghe River, and coastal erosion. The central area, located in an eddy center, has a mica-authigenic pyrite-hornblende-quartz-feldspar assemblage, indicating multiple sources dominated by Huanghe River distal sediments.
文摘Despite concerted efforts to create employment opportunities and the realized economic growth between 2000 and 2005, the unemployment rate in Namibia currently stands at 27.4%, according to the Labour Force Survey released in April 2013. The percentage of employed males in Namibia stands at 41.6% while that of employed females stand at 28.8% according to the National Human Resources Plan of May 2013. Analysts have put the blame on adverse climatic conditions, limited levels of skills, access to finance, and the structure of the economy. The frustration and discomfort caused by unemployment, especially among the youth, can threaten the country＇s peace and stability as it negatively impacts on the standard of living, crime rates, family happiness, and drug abuse.To date, studies on employment in Namibia have mainly concentrated on the micro and macro econometric approaches. It is important to examine how bio-demographic characteristics affect employment. This paper uses data from the 2010 Income and expenditure survey to establish the bio-demographic determinants of employment by fitting a binary logistic model. The outcome variable is employment status which is dichotomous. The independent variables which were guided by review of related literature and availability of data in the Income and Expenditure survey data set, included age-group, region, place of residence, marital status, education level, and gender. Results indicated that employment prospects in Namibia were influenced by the region, gender, marital status, and education level.
基金financially supported jointly by the National Basic Research Program of China(Grant No.2010CB950602)the National Natural Science Foundation of China(Grant Nos.41175133,21228701,41275166,and 41321064)
文摘By using packed soil-core incubation experiments, we have studied stimulating effects of addition of external carbon （C） （glu- cose, 6.4 g C m 2） on heterotrophic respiration and microbial biomass C of a mature broadleaf and Korean pine mixed forest （BKPF） and an adjacent white birch forest （WBF） soil under different wetting intensities （55% and 80% WFPS, water-filled pore space） and nitrogen （N） supply （NH4C1 and KNO3, 4.5 g N m-e） conditions. The results showed that for the control, the cumulative carbon dioxide （CO2） flux from WBF soil during the 15-day incubation ranged from 5.44 to 5.82 g CO2-C m-2, which was significantly larger than that from BKPF soil （2.86 to 3.36 g CO2-C m 2）. With increasing wetting intensity, the cumulative CO2 flux from the control was decreased for the WBF soil, whereas an increase in the CO2 flux was observed in the BKPF soil （P 〈 0.05）. The addition of NH4C1 or KNO3 alone significantly reduced the cumulative CO2 fluxes by 9.2%-21.6 % from the two soils, especially from WBF soil at low wetting intensity. The addition of glucose alone significantly increased soil heterotrophic respiration, microbial biomass C （MBC）, and microbial metabolic quotient. The glucose-induced cumulative CO2 fluxes and soil MBC during the incubation ranged from 8.7 to 11.7 g CO2-C m-2 and from 7.4 to 23.9 g C m-2, which are larger than the dose of added C. Hence, the addition of external carbon can increase the decomposition of soil native organic C. The glucose-induced average and maximum rates of CO2 fluxes during the incubation were significantly in- fluenced by wetting intensity （WI） and vegetation type （VT）, and by WIxVT, NH4ClxVT and WIxVTxNH4C1 （P〈0.05）. The addition of NH4C1, instead of KNO3, significantly decreased the glucose-induced MBC of WBF soil （P〈0.05）, whereas adding NH4C1 and KNO3 both significantly increased the glucose-induced MBC of BKPF soil at high moisture （P〈0.05）. According to the differences in soil labile C pools, MBC and CO2 fluxes in the presence and absence of glucose, it can be concluded that the stimulating effects of glucose on soil heterotrophic respiration and MBC under temperate forests were dependent on vegetation type, soil moisture, and amount and type of the N added.
