分析了32种常见绿化树种释放的挥发性有机物,探究植物源挥发性有机物特征及其和臭氧、二次有机气溶胶生成潜势的关系,并筛选出城市绿化中低生成潜势树种.结果显示,臭氧生成潜势与烃类、酯类、醇类、酮类、醛类的释放量显著相关(P<0.0...分析了32种常见绿化树种释放的挥发性有机物,探究植物源挥发性有机物特征及其和臭氧、二次有机气溶胶生成潜势的关系,并筛选出城市绿化中低生成潜势树种.结果显示,臭氧生成潜势与烃类、酯类、醇类、酮类、醛类的释放量显著相关(P<0.01),这五类化合物占臭氧生成潜势总变化的60.3%.二次有机气溶胶生成潜势与烃类、醇类、醛类和酯类的释放量显著相关(P<0.01),这四类化合物占二次有机气溶胶总变化的73.2%.臭椿(Ailanthus altissima)和樱花(Cerasus serrulata var. lannesiana)对臭氧和二次有机气溶胶生成潜势相对较弱,豆科和杨柳科包含的12个树种对臭氧和二次有机气溶胶生成潜势相对较强.展开更多
Controlled grazing is considered a good management strategy to maintain or increase the live weight of livestock and to reduce vegetation degradation of rangelands. The present study investigated soil characteristics,...Controlled grazing is considered a good management strategy to maintain or increase the live weight of livestock and to reduce vegetation degradation of rangelands. The present study investigated soil characteristics, aboveground vegetation biomass dynamics and controlled grazinginduced changes in the live weight of local ewes in the semi-arid rangeland of Ahmadun, Ziarat, Balochistanprovince of Pakistan. An area of 115 ha was protected from livestock grazing in April 2014. In June 2015, soil characteristics within 0-30 cm depth i.e. soil organic matter(SOM), mineral nitrogen, p H and texture in controlled and uncontrolled grazing sites were assessed. Aboveground vegetation biomass measured in early(June) and late summer(August) in 2015 and 2016. The nutritional value i.e. crude protein, phosphorus(P), neutral detergent fiber(NDF), acid detergent fiber(ADF), calcium(Ca), magnesium(Mg) and potassium(K) of dominantplant species were assessed at the beginning of experiment in 2015. Vegetation cover of controlled and uncontrolled grazing sites was also measured during the two years of the study period using the Veg Measure software. From June to November in2015 and 2016, controlled and uncontrolled livestock grazing sites were grazed on a daily basis by local ewes with a stocking rate of 2 and 1 head ha^(-1) respectively. Results reveal that the organic matter contents of coarse-textured, slightly alkaline soil of the study site were in the range of 9.4-17.6 g kg^(-1) soil and showed a strong positive correlation with aboveground vegetation biomass. The biomass of plants was 56.5% and 33% greater at controlled than uncontrolled grazing site in 2015 and 2016 respectively and plant cover was also higher at controlled than uncontrolled grazing site in both years The nutrient contents were significantly(P<0.05)lower in grasses than shrubs. In both years, the controlled grazing increased the weight gain of ewes about two folds compared to the uncontrolled grazing.The results indicate that controlled grazing improved the vegetation biomass production and small ruminant productivity.展开更多
Biogenic isoprene is an important precursor of tropospheric ozone(O_(3)).Here,a coupled chemistry-vegetation model was used to quantify the contributions of isoprene emissions to surface O_(3)pollution on the global s...Biogenic isoprene is an important precursor of tropospheric ozone(O_(3)).Here,a coupled chemistry-vegetation model was used to quantify the contributions of isoprene emissions to surface O_(3)pollution on the global scale during 2000-2019.The biogenic isoprene emissions showed high values in mid-low latitudes and seasonal peaks in the summer hemispheres.They promote global surface O_(3)concentrations by 1.75 ppbv annually with regional hotspots of 4.39 ppbv(8.8%)in China and 5.36 ppbv(11.1%)in the U.S.in boreal summer.In the past two decades,isoprene emissions increased by 1.32 TgC yr^(−1)(0.67%yr^(−1))in the Northern Hemisphere but decreased by 0.71 TgC yr^(−1)(0.44%yr^(−1))in the Southern Hemisphere.Such changes of isoprene made opposite contributions to the surface O_(3)trend,with 0.26 ppbv yr^(−1)in eastern China but−0.32 ppbv yr^(−1)in the southeastern U.S.due to the changes in the background regime of chemical reactions.The impact of anthropogenic changes on the O_(3)trend is consistent with that of biogenic isoprene,but two to four times stronger in magnitude.This study revealed that the effective control of anthropogenic NO_(x)emissions could mitigate regional O_(3)pollution even with the increased isoprene emissions under global warming.展开更多
文摘分析了32种常见绿化树种释放的挥发性有机物,探究植物源挥发性有机物特征及其和臭氧、二次有机气溶胶生成潜势的关系,并筛选出城市绿化中低生成潜势树种.结果显示,臭氧生成潜势与烃类、酯类、醇类、酮类、醛类的释放量显著相关(P<0.01),这五类化合物占臭氧生成潜势总变化的60.3%.二次有机气溶胶生成潜势与烃类、醇类、醛类和酯类的释放量显著相关(P<0.01),这四类化合物占二次有机气溶胶总变化的73.2%.臭椿(Ailanthus altissima)和樱花(Cerasus serrulata var. lannesiana)对臭氧和二次有机气溶胶生成潜势相对较弱,豆科和杨柳科包含的12个树种对臭氧和二次有机气溶胶生成潜势相对较强.
基金supported by the USAID under Agriculture Innovation Program (AIP) Pakistansupported by the ICARDA and the CGIAR Research Program on Livestock (CRP Livestock)
文摘Controlled grazing is considered a good management strategy to maintain or increase the live weight of livestock and to reduce vegetation degradation of rangelands. The present study investigated soil characteristics, aboveground vegetation biomass dynamics and controlled grazinginduced changes in the live weight of local ewes in the semi-arid rangeland of Ahmadun, Ziarat, Balochistanprovince of Pakistan. An area of 115 ha was protected from livestock grazing in April 2014. In June 2015, soil characteristics within 0-30 cm depth i.e. soil organic matter(SOM), mineral nitrogen, p H and texture in controlled and uncontrolled grazing sites were assessed. Aboveground vegetation biomass measured in early(June) and late summer(August) in 2015 and 2016. The nutritional value i.e. crude protein, phosphorus(P), neutral detergent fiber(NDF), acid detergent fiber(ADF), calcium(Ca), magnesium(Mg) and potassium(K) of dominantplant species were assessed at the beginning of experiment in 2015. Vegetation cover of controlled and uncontrolled grazing sites was also measured during the two years of the study period using the Veg Measure software. From June to November in2015 and 2016, controlled and uncontrolled livestock grazing sites were grazed on a daily basis by local ewes with a stocking rate of 2 and 1 head ha^(-1) respectively. Results reveal that the organic matter contents of coarse-textured, slightly alkaline soil of the study site were in the range of 9.4-17.6 g kg^(-1) soil and showed a strong positive correlation with aboveground vegetation biomass. The biomass of plants was 56.5% and 33% greater at controlled than uncontrolled grazing site in 2015 and 2016 respectively and plant cover was also higher at controlled than uncontrolled grazing site in both years The nutrient contents were significantly(P<0.05)lower in grasses than shrubs. In both years, the controlled grazing increased the weight gain of ewes about two folds compared to the uncontrolled grazing.The results indicate that controlled grazing improved the vegetation biomass production and small ruminant productivity.
基金supported by the National Key Research and Development Program of China[grant number 2023YFF0805403]the National Natural Science Foundation of China[grant number 41975155].
文摘Biogenic isoprene is an important precursor of tropospheric ozone(O_(3)).Here,a coupled chemistry-vegetation model was used to quantify the contributions of isoprene emissions to surface O_(3)pollution on the global scale during 2000-2019.The biogenic isoprene emissions showed high values in mid-low latitudes and seasonal peaks in the summer hemispheres.They promote global surface O_(3)concentrations by 1.75 ppbv annually with regional hotspots of 4.39 ppbv(8.8%)in China and 5.36 ppbv(11.1%)in the U.S.in boreal summer.In the past two decades,isoprene emissions increased by 1.32 TgC yr^(−1)(0.67%yr^(−1))in the Northern Hemisphere but decreased by 0.71 TgC yr^(−1)(0.44%yr^(−1))in the Southern Hemisphere.Such changes of isoprene made opposite contributions to the surface O_(3)trend,with 0.26 ppbv yr^(−1)in eastern China but−0.32 ppbv yr^(−1)in the southeastern U.S.due to the changes in the background regime of chemical reactions.The impact of anthropogenic changes on the O_(3)trend is consistent with that of biogenic isoprene,but two to four times stronger in magnitude.This study revealed that the effective control of anthropogenic NO_(x)emissions could mitigate regional O_(3)pollution even with the increased isoprene emissions under global warming.
