Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollu...Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollution. Physicochemical characteristics of ambient particles settling upon leaf surfaces of eleven roadside plants at four sites of Beijing were studies. Results showed that density of particles on the leaf surfaces greatly varied with plant species and traffic condition. Fraxinus chiuensis, Sophora japonica Ailanthus altissima, Syringa oblata and Prunus persica, had larger densities of particles among the tall species. Due to resuspension of road dust, the densities of particles of Euonymus japonicns and Parthenocissus quinquefolia with low sampling height were 2-35 times to other taller tree species. For test plant species, micro-roughness of leaf surfaces and density of particles showed a close correlation. In general, the larger micro-roughness of leaf surfaces is, the larger density of particles is. Particles settling upon leaf surfaces were dominantly PM30 （particulate matter less than 10 μm in aerodynamic diameter; 98.4%） and PM2.5 （particulate matter less than 2.5 μm in aerodynamic diameter; 64.2%） which were closely relative to human health. Constant elements of particles were C, O, K, Ca, Si, Al, Mg, Na, Fe, S, Cl and minerals with higher content were SiO2, CaCO3, CaMg（CO3）2, NaCI and 2CASO4. H2O, SiO2. CaCO3 and CaMg（CO3）2 mainly came from resuspension of road dust. 2CaSO4. H2O was produced by the reaction between CaCO3 derived from earth dust or industrial emission and SO2, H2SO4 or sulfate. NaCl was derived from sea salt.展开更多
In order to investigate the dynamic evolution of the sandy land-lake-vegetation landscape in Songnen Sandy Land(SSL)and its response to climate change and human activities,the distribution pattern,evolution,and drivin...In order to investigate the dynamic evolution of the sandy land-lake-vegetation landscape in Songnen Sandy Land(SSL)and its response to climate change and human activities,the distribution pattern,evolution,and driving mechanisms of the landscape were analyzed based on Landsat satellite images and meteorological and socio-economic data during 1980–2020.The results indicate that the area of sandy land exhibited an upward fluctuation during the last 40 yr,with a net increase of 251.75 km^(2) at an increment rate of 3.80%/10 yr.The lake area also exhibited an upward fluctuation,with a net increase of 1200.95 km^(2) at an increment rate of 20.42%/10 yr.Vegetation coverage decreased by 2633.30 km^(2),with areas of low vegetation coverage exhibiting a trend of initial decline and subsequent increase,areas of medium vegetation coverage showed an upward fluctuation,and areas of high vegetation coverage showed a trend of initial increase and subsequent decrease,with overall changes of–0.67%/yr,1.12%/yr,and 0.17%/yr,respectively.The relationships between sandy land,lakes,and vegetation coverage were significant,with areas of sandy land and low vegetation coverage showing the strongest correlation.The dynamic evolution of landscape is controlled by regional climatic and socio-economic factors,with socio-economic factors as the first principal component contributing up to 59.64%.展开更多
Quaternary aeolian environment researches were mainly conducted by analyzing the information carriers, extracting valuable evidences about aeolian environment changes, so to presume and reconstruct paleoenvironments. ...Quaternary aeolian environment researches were mainly conducted by analyzing the information carriers, extracting valuable evidences about aeolian environment changes, so to presume and reconstruct paleoenvironments. This paper formulated progress in Quaternary aeolian environment research using dune-morphological records, sedimentological records and bio-fossils records, as well as advances about chronology; presented that people should pay more attention to further synthetic study of multi-types of records including dune morphology, size, formation time, sediment supply, and their relations with wind regime in future, especially the research on dating method.展开更多
Based on the tree ring width index of Pinus tabulaeformis, precipitation in the last 140 years was recon-structed at south margin of the Tengger Desert. The results indicated that there were obvious fluctuations of dr...Based on the tree ring width index of Pinus tabulaeformis, precipitation in the last 140 years was recon-structed at south margin of the Tengger Desert. The results indicated that there were obvious fluctuations of dry-wet changes in precipitation: two wet periods occurred during 1868―1876 and 1932―1939, and two dry periods during 1877―1894 and 1924―1932, however, the years 1887 and 1888 were a little wet. There were small changes in precipita-tion during 1895―1923 and 1940―2000. As compared to the average, the maximum increasing range of precipitation amounted to 56% during the wet periods, and 42% during the dry periods. And the range of variability of precipitation exceeded 30% in 19 years. There was no obvious consistent drying or wetting trend in the last 140 years. But since 1940 fluctuating scope of precipitation tended to be smaller, while the frequency of the fluctuation tended to be larger. Power spectrum analyses suggested that precipitation of south mar-gin of the Tengger Desert had significant periodicities of 2.46―2.64 a and quasi periodicity of 11.67 a.展开更多
Environments in arid and semiarid regions are extremely sensitive to climate changes. High wind activity in these regions has resulted in an extensively developed arid geomorphology, but past environmental changes are...Environments in arid and semiarid regions are extremely sensitive to climate changes. High wind activity in these regions has resulted in an extensively developed arid geomorphology, but past environmental changes are poorly understood because of the absence of relatively high-resolution proxies. The accumulation characteristics of nebkhas, which have developed extensively in these regions, can be used as a method of reconstructing environmental changes. Here we summarized recent advances in research on the formation, development, and sediment characteristics of nebkhas and their significance to environmental changes in arid and semiarid regions. Based on the studies of our colleagues, we suggested that research on nebkha formation can provide distinct clues about environmental changes in arid and semiarid regions; however, continued studies are needed.展开更多
To better understand the key role of biological soil crusts(BSCs) in redistribution processes of limited water resources in semi-arid sandy ecosystems,surface runoff over BSCs in a sandy area in the southern Mu Us san...To better understand the key role of biological soil crusts(BSCs) in redistribution processes of limited water resources in semi-arid sandy ecosystems,surface runoff over BSCs in a sandy area in the southern Mu Us sandy area was observed in this study.The results indicated that runoff occurred twice among six rainfall events during the experimental period.Runoff yields varied among types of BSCs,and that they increased in the following order:light algae crusts,dark algae crusts and moss crusts.These findings showed that runoff yields were increasing with the development of BSCs.The percentage of runoff in individual rainfall events increased from light algae crusts to moss crusts,which indicated that the redistribution ratios of different types of BSCs differed.Surface runoff of BSCs may be influenced by rainfall,rain intensity,degree of water saturation of the BSCs before the rain and degree of development of BSCs.Formation of BSCs on the surface of sand dunes changed the spatial distribution pattern of water in this semi-arid sandy ecosystem,which increased the heterogeneity of resources such as water and nutrients.Therefore,making appropriate disturbances of BSCs during storm season is beneficial to maintaining the balance of natural resources in the semi-arid sandy ecosystem.展开更多
Little work has been done on stemflow for desert shrubs in China. This study measured stemflow in two shrubs of Salix psammophila C. Wang et Chang Y. Yang and Artemisia sphaerocephala Krasch in Mu Us sandy land and es...Little work has been done on stemflow for desert shrubs in China. This study measured stemflow in two shrubs of Salix psammophila C. Wang et Chang Y. Yang and Artemisia sphaerocephala Krasch in Mu Us sandy land and established a relationship between stemflow and canopy characteristics, rainfall amount and intensity. During the experimental period, the amount of stemflow for S. psammophila and A. sphaerocephala accounted for 7.6% and 2.7% of the gross rainfall respectively. Statistical analysis showed that there was a significant positive linear correlation between rainfall and stemflow for the two shrubs; while the relationship between stemflow percentage and rainfall suggested that there existed a rainfall depth threshold of 3―5 mm for S. psammophila and 5―7 mm for A. sphaerocephala. Stemflow percentage positively increased with rainfall depth increasing before the rainfall depth threshold values had been reached but showed stability after the threshold. A stepwise regression analysis suggested that the shrubs with more branches, larger crown volume and smaller branch angle inclination tended to collect more volumes of stemflow. Moreover, stemflow amount and percentage increased with the maximum rain intensity increasing in 10 minutes (I10) and the stemflow percentage tended to increase quickly with I10 when it was less than 3.0 mm h-1 for S. psammophila and 2.0 mm h-1 for A. sphaero- cephala, and then showed stable trend with increasing of I10.展开更多
基金The National Natural Science Foundation of China (No. 30570338) the Natural Science Foundation of Beijing (No. 6053026) andthe Ministry of Education, China(No. 20040027020).
文摘Particulate pollution is a serious health problem throughout the world, exacerbating a wide range of respiratory and vascular illnesses in urban areas. Urban plants play an important role in reducing particulate pollution. Physicochemical characteristics of ambient particles settling upon leaf surfaces of eleven roadside plants at four sites of Beijing were studies. Results showed that density of particles on the leaf surfaces greatly varied with plant species and traffic condition. Fraxinus chiuensis, Sophora japonica Ailanthus altissima, Syringa oblata and Prunus persica, had larger densities of particles among the tall species. Due to resuspension of road dust, the densities of particles of Euonymus japonicns and Parthenocissus quinquefolia with low sampling height were 2-35 times to other taller tree species. For test plant species, micro-roughness of leaf surfaces and density of particles showed a close correlation. In general, the larger micro-roughness of leaf surfaces is, the larger density of particles is. Particles settling upon leaf surfaces were dominantly PM30 （particulate matter less than 10 μm in aerodynamic diameter; 98.4%） and PM2.5 （particulate matter less than 2.5 μm in aerodynamic diameter; 64.2%） which were closely relative to human health. Constant elements of particles were C, O, K, Ca, Si, Al, Mg, Na, Fe, S, Cl and minerals with higher content were SiO2, CaCO3, CaMg（CO3）2, NaCI and 2CASO4. H2O, SiO2. CaCO3 and CaMg（CO3）2 mainly came from resuspension of road dust. 2CaSO4. H2O was produced by the reaction between CaCO3 derived from earth dust or industrial emission and SO2, H2SO4 or sulfate. NaCl was derived from sea salt.
基金Under the auspices of National Natural Science Foundation of China(No.41871022)Natural Science Foundation of Jilin Province(No.20210101398JC)。
文摘In order to investigate the dynamic evolution of the sandy land-lake-vegetation landscape in Songnen Sandy Land(SSL)and its response to climate change and human activities,the distribution pattern,evolution,and driving mechanisms of the landscape were analyzed based on Landsat satellite images and meteorological and socio-economic data during 1980–2020.The results indicate that the area of sandy land exhibited an upward fluctuation during the last 40 yr,with a net increase of 251.75 km^(2) at an increment rate of 3.80%/10 yr.The lake area also exhibited an upward fluctuation,with a net increase of 1200.95 km^(2) at an increment rate of 20.42%/10 yr.Vegetation coverage decreased by 2633.30 km^(2),with areas of low vegetation coverage exhibiting a trend of initial decline and subsequent increase,areas of medium vegetation coverage showed an upward fluctuation,and areas of high vegetation coverage showed a trend of initial increase and subsequent decrease,with overall changes of–0.67%/yr,1.12%/yr,and 0.17%/yr,respectively.The relationships between sandy land,lakes,and vegetation coverage were significant,with areas of sandy land and low vegetation coverage showing the strongest correlation.The dynamic evolution of landscape is controlled by regional climatic and socio-economic factors,with socio-economic factors as the first principal component contributing up to 59.64%.
基金Undertheauspicesof the National Natural Science Foundation of China (No. 40271114, 40471013)
文摘Quaternary aeolian environment researches were mainly conducted by analyzing the information carriers, extracting valuable evidences about aeolian environment changes, so to presume and reconstruct paleoenvironments. This paper formulated progress in Quaternary aeolian environment research using dune-morphological records, sedimentological records and bio-fossils records, as well as advances about chronology; presented that people should pay more attention to further synthetic study of multi-types of records including dune morphology, size, formation time, sediment supply, and their relations with wind regime in future, especially the research on dating method.
基金supported by the Na tional Natural Science Foundation of China(Grant No.40271114)the Specialized Research Fund for the Doctoral Program of Higher Educa-tion of China(Grant No.20040027024)the National Key Projects for Basic Scientific Research(Grant No.G2000048701).
文摘Based on the tree ring width index of Pinus tabulaeformis, precipitation in the last 140 years was recon-structed at south margin of the Tengger Desert. The results indicated that there were obvious fluctuations of dry-wet changes in precipitation: two wet periods occurred during 1868―1876 and 1932―1939, and two dry periods during 1877―1894 and 1924―1932, however, the years 1887 and 1888 were a little wet. There were small changes in precipita-tion during 1895―1923 and 1940―2000. As compared to the average, the maximum increasing range of precipitation amounted to 56% during the wet periods, and 42% during the dry periods. And the range of variability of precipitation exceeded 30% in 19 years. There was no obvious consistent drying or wetting trend in the last 140 years. But since 1940 fluctuating scope of precipitation tended to be smaller, while the frequency of the fluctuation tended to be larger. Power spectrum analyses suggested that precipitation of south mar-gin of the Tengger Desert had significant periodicities of 2.46―2.64 a and quasi periodicity of 11.67 a.
基金National Natural Science Foundation of China, No.41071008
文摘Environments in arid and semiarid regions are extremely sensitive to climate changes. High wind activity in these regions has resulted in an extensively developed arid geomorphology, but past environmental changes are poorly understood because of the absence of relatively high-resolution proxies. The accumulation characteristics of nebkhas, which have developed extensively in these regions, can be used as a method of reconstructing environmental changes. Here we summarized recent advances in research on the formation, development, and sediment characteristics of nebkhas and their significance to environmental changes in arid and semiarid regions. Based on the studies of our colleagues, we suggested that research on nebkha formation can provide distinct clues about environmental changes in arid and semiarid regions; however, continued studies are needed.
基金supported by the National Natural Science Foundation of China (401171002)the Fundamental Research Funds for Central Universities
文摘To better understand the key role of biological soil crusts(BSCs) in redistribution processes of limited water resources in semi-arid sandy ecosystems,surface runoff over BSCs in a sandy area in the southern Mu Us sandy area was observed in this study.The results indicated that runoff occurred twice among six rainfall events during the experimental period.Runoff yields varied among types of BSCs,and that they increased in the following order:light algae crusts,dark algae crusts and moss crusts.These findings showed that runoff yields were increasing with the development of BSCs.The percentage of runoff in individual rainfall events increased from light algae crusts to moss crusts,which indicated that the redistribution ratios of different types of BSCs differed.Surface runoff of BSCs may be influenced by rainfall,rain intensity,degree of water saturation of the BSCs before the rain and degree of development of BSCs.Formation of BSCs on the surface of sand dunes changed the spatial distribution pattern of water in this semi-arid sandy ecosystem,which increased the heterogeneity of resources such as water and nutrients.Therefore,making appropriate disturbances of BSCs during storm season is beneficial to maintaining the balance of natural resources in the semi-arid sandy ecosystem.
基金Supported by the National Natural Science Foundation of China (Grant No. 40571023)the Foundation for the Author of National Excellent Doctoral Disserta-tion of China for Dr. Xiao-Yan Li (Grant No. 200426)the National Key Tech-nologies R&D Program (Grant No. 2006BAD26B07)
文摘Little work has been done on stemflow for desert shrubs in China. This study measured stemflow in two shrubs of Salix psammophila C. Wang et Chang Y. Yang and Artemisia sphaerocephala Krasch in Mu Us sandy land and established a relationship between stemflow and canopy characteristics, rainfall amount and intensity. During the experimental period, the amount of stemflow for S. psammophila and A. sphaerocephala accounted for 7.6% and 2.7% of the gross rainfall respectively. Statistical analysis showed that there was a significant positive linear correlation between rainfall and stemflow for the two shrubs; while the relationship between stemflow percentage and rainfall suggested that there existed a rainfall depth threshold of 3―5 mm for S. psammophila and 5―7 mm for A. sphaerocephala. Stemflow percentage positively increased with rainfall depth increasing before the rainfall depth threshold values had been reached but showed stability after the threshold. A stepwise regression analysis suggested that the shrubs with more branches, larger crown volume and smaller branch angle inclination tended to collect more volumes of stemflow. Moreover, stemflow amount and percentage increased with the maximum rain intensity increasing in 10 minutes (I10) and the stemflow percentage tended to increase quickly with I10 when it was less than 3.0 mm h-1 for S. psammophila and 2.0 mm h-1 for A. sphaero- cephala, and then showed stable trend with increasing of I10.
