Introduction:Among the most dangerous pollutants is PM_(2.5),which can directly pass through human lungs and move into the blood system.The use of nature-based solutions,such as increased vegetation cover in an urban ...Introduction:Among the most dangerous pollutants is PM_(2.5),which can directly pass through human lungs and move into the blood system.The use of nature-based solutions,such as increased vegetation cover in an urban landscape,is one of the possible solutions for reducing PM_(2.5) concentration.Our study objective was to understand the importance of green spaces in pollution reduction.Methods:Daily PM_(2.5) concentrations were manually collected at nine monitoring stations in Nanjing over a 534-day period from the air quality report of the China National Environmental Monitoring Center(CNEMC)to quantify the spatiotemporal change of PM_(2.5) concentration and its empirical relationship with vegetation and landscape structure in Nanjing.Results:The daily average,minimum,and maximum PM_(2.5) concentrations from the nine stations were 74.0,14.2,and 332.0μg m^(−3),respectively.Out of the 534 days,the days recorded as“excellent”and“good”conditions were found mostly in the spring(30.7%),autumn(25.6%),and summer(24.5%),with only 19.2% of the days in the winter.High PM_(2.5) concentrations exceeding the safe standards of the CNEMC were recorded predominately during the winter(39.3-100.0%).Our hypothesis that green vegetation had the potential to reduce PM_(2.5) concentration was accepted at specific seasons and scales.The PM_(2.5) concentration appeared very highly correlated(R2>0.85)with green cover in spring at 1-2 km scales,highly correlated(R2>0.6)in autumn and winter at 4 km scale,and moderately correlated in summer(R2>0.4)at 2-,5-,and 6-km scales.However,a non-significant correlation between green cover and PM_(2.5) concentration was found when its level was>75μg m^(−3).Across the Nanjing urban landscape,the east and southwest parts had high pollution levels.Conclusions:Although the empirical models seemed significant for spring only,one should not devalue the importance of green vegetation in other seasons because the regulations are often complicated by vegetation,meteorological conditions,and human activities.展开更多
Aims Recent studies revealed convergent temperature sensitivity of ecosys-tem respiration(Re)within aquatic ecosystems and between terrestrial and aquatic ecosystems.We do not know yet whether various terres-trial eco...Aims Recent studies revealed convergent temperature sensitivity of ecosys-tem respiration(Re)within aquatic ecosystems and between terrestrial and aquatic ecosystems.We do not know yet whether various terres-trial ecosystems have consistent or divergent temperature sensitivity.Here,we synthesized 163 eddy covariance flux sites across the world and examined the global variation of the apparent activation energy(Ea),which characterizes the apparent temperature sensitivity of and its interannual variability(IAV)as well as their controlling factors.Methods We used carbon fluxes and meteorological data across FLUXNET sites to calculate mean annual temperature,tempera-ture range,precipitation,global radiation,potential radiation,gross primary productivity and Re by averaging the daily values over the years in each site.Furthermore,we analyzed the sites with>8 years data to examine the IAV of Ea and calculated the standard deviation of Ea across years at each site to character-ize IAV.Important Findings The results showed a widely global variation of Ea,with significantly lower values in the tropical and subtropical areas than in temperate and boreal areas,and significantly higher values in grasslands and wetlands than that in deciduous broadleaf forests and evergreen for-ests.Globally,spatial variations of Ea were explained by changes in temperature and an index of water availability with differing contribution of each explaining variable among climate zones and biomes.IAV and the corresponding coefficient of variation of Ea decreased with increasing latitude,but increased with radiation and corresponding mean annual temperature.The revealed patterns in the spatial and temporal variations of Ea and its controlling factors indicate divergent temperature sensitivity of Re,which could help to improve our predictive understanding of Re in response to climate change.展开更多
基金the funding support from the Land Cover and Land Use Program of National Aeronautics and Space Administration(NASA)through the grant to Michigan State University(NNX15AD51G).
文摘Introduction:Among the most dangerous pollutants is PM_(2.5),which can directly pass through human lungs and move into the blood system.The use of nature-based solutions,such as increased vegetation cover in an urban landscape,is one of the possible solutions for reducing PM_(2.5) concentration.Our study objective was to understand the importance of green spaces in pollution reduction.Methods:Daily PM_(2.5) concentrations were manually collected at nine monitoring stations in Nanjing over a 534-day period from the air quality report of the China National Environmental Monitoring Center(CNEMC)to quantify the spatiotemporal change of PM_(2.5) concentration and its empirical relationship with vegetation and landscape structure in Nanjing.Results:The daily average,minimum,and maximum PM_(2.5) concentrations from the nine stations were 74.0,14.2,and 332.0μg m^(−3),respectively.Out of the 534 days,the days recorded as“excellent”and“good”conditions were found mostly in the spring(30.7%),autumn(25.6%),and summer(24.5%),with only 19.2% of the days in the winter.High PM_(2.5) concentrations exceeding the safe standards of the CNEMC were recorded predominately during the winter(39.3-100.0%).Our hypothesis that green vegetation had the potential to reduce PM_(2.5) concentration was accepted at specific seasons and scales.The PM_(2.5) concentration appeared very highly correlated(R2>0.85)with green cover in spring at 1-2 km scales,highly correlated(R2>0.6)in autumn and winter at 4 km scale,and moderately correlated in summer(R2>0.4)at 2-,5-,and 6-km scales.However,a non-significant correlation between green cover and PM_(2.5) concentration was found when its level was>75μg m^(−3).Across the Nanjing urban landscape,the east and southwest parts had high pollution levels.Conclusions:Although the empirical models seemed significant for spring only,one should not devalue the importance of green vegetation in other seasons because the regulations are often complicated by vegetation,meteorological conditions,and human activities.
基金‘One hundred Talent’award and‘Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues’of the Chinese Academy of Sciences(XDA05050601 to S.N.)Terrestrial Carbon Program at the Office of Science+1 种基金US Department of Energy(DE-FG02-006ER64317)U.S.National Science Foundation(NSF)(DEB 0444518,DEB 0743778,DEB 0840964,DBI 0850290,EPS 0919466 to Y.L.).
文摘Aims Recent studies revealed convergent temperature sensitivity of ecosys-tem respiration(Re)within aquatic ecosystems and between terrestrial and aquatic ecosystems.We do not know yet whether various terres-trial ecosystems have consistent or divergent temperature sensitivity.Here,we synthesized 163 eddy covariance flux sites across the world and examined the global variation of the apparent activation energy(Ea),which characterizes the apparent temperature sensitivity of and its interannual variability(IAV)as well as their controlling factors.Methods We used carbon fluxes and meteorological data across FLUXNET sites to calculate mean annual temperature,tempera-ture range,precipitation,global radiation,potential radiation,gross primary productivity and Re by averaging the daily values over the years in each site.Furthermore,we analyzed the sites with>8 years data to examine the IAV of Ea and calculated the standard deviation of Ea across years at each site to character-ize IAV.Important Findings The results showed a widely global variation of Ea,with significantly lower values in the tropical and subtropical areas than in temperate and boreal areas,and significantly higher values in grasslands and wetlands than that in deciduous broadleaf forests and evergreen for-ests.Globally,spatial variations of Ea were explained by changes in temperature and an index of water availability with differing contribution of each explaining variable among climate zones and biomes.IAV and the corresponding coefficient of variation of Ea decreased with increasing latitude,but increased with radiation and corresponding mean annual temperature.The revealed patterns in the spatial and temporal variations of Ea and its controlling factors indicate divergent temperature sensitivity of Re,which could help to improve our predictive understanding of Re in response to climate change.
