通讯机构：
[Zhang, X; Yan, WD ] C;Cent South Univ Forestry & Technol, Fac Life Sci & Technol, Changsha 410004, Peoples R China.;Natl Engn Lab Appl Technol Forestry & Ecol South C, Changsha 410004, Peoples R China.;Key Lab Urban Forest Ecol Hunan Prov, Changsha 410004, Peoples R China.;Lutou Natl Stn Sci Observat & Res Forest Ecosyst, Yueyang 414000, Peoples R China.
关键词：
CO2 flux;urban;eddy covariance;footprint model
摘要：
Understanding the spatial and temporal variations of urban carbon dioxide fluxes (F-CO2) and their influencing factors is crucial for solving urban climate problems and promoting the development of low-carbon cities. In this study, the carbon dioxide flux (F-CO2) in Changsha City, China, was analyzed using the eddy covariance technique and flux footprint model. The results showed that the extent of the flux footprint within the observation site was mostly limited to 500 m. Diurnal variation of F-CO2 showed a regular pattern influenced by plant photosynthesis and traffic flow. Meanwhile, photosynthesis was directly regulated by photosynthetically active radiation and indirectly regulated by air temperature and water vapor pressure differences. The average value of F-CO2 was lower during the daytime than at night, indicating the high vegetation cover (43.5%) in the study area. In addition, there were spatial characteristics of F-CO2 in each wind direction due to different surface land use in the study area. Notably, a decreasing trend in carbon dioxide content was observed after the area covered by vegetation was 1.8 times the area of buildings and major roads combined. These findings guide climate management, urban planning, and sustainable development toward a low-carbon society.
作者机构：
[Liang, Xiaocui; Chen, Yazhen; Xu, Yichen; Yan, Wende; Zhang, Rui; Yan, Ying; Qin, Shixin] Cent South Univ Forestry & Technol, Fac Life Sci & Technol, Changsha, Hunan, Peoples R China.;[Liang, Xiaocui; Chen, Yazhen; Xu, Yichen; Yan, Wende] Natl Engn Lab Appl Technol Forestry & Ecol South C, Changsha, Hunan, Peoples R China.;[Liang, Xiaocui; Yan, Wende] Key Lab Urban Forest Ecol Hunan Prov, Changsha, Hunan, Peoples R China.;[Liang, Xiaocui; Yan, Wende] Lutou Natl Stn Sci Observat & Res Forest Ecosyst H, Yueyang, Peoples R China.;[Liang, Xiaocui; Yan, Wende] Key Lab Subtrop Forest Ecol Hunan Prov, Changsha, Hunan, Peoples R China.
通讯机构：
[Liang, XC; Yan, WD ] C;Cent South Univ Forestry & Technol, Fac Life Sci & Technol, Changsha, Hunan, Peoples R China.;Natl Engn Lab Appl Technol Forestry & Ecol South C, Changsha, Hunan, Peoples R China.;Key Lab Urban Forest Ecol Hunan Prov, Changsha, Hunan, Peoples R China.;Lutou Natl Stn Sci Observat & Res Forest Ecosyst H, Yueyang, Peoples R China.
摘要：
As a major source of air pollution, particulate matter (PM) and associated toxic trace elements pose potentially serious threats to human health and environmental safety. As is known that plants can reduce air PM pollution. However, the relationship between PM of different sizes and toxic trace elements in foliar PM is still unclear. This study was performed to explore the association between PM of different sizes (PM2.5, PM10, PM>10) and toxic trace elements (As, Al, Cu, Zn, Cd, Fe, Pb) as well as the correlation among toxic trace elements of six roadside plant species (Cinnamomum camphora, Osmanthus fragrans, Magnolia grandiflora, Podocarpus macrophyllus, Loropetalum chinense var. rubrum and Pittosporum tobira) in Changsha, Hunan Province, China. Results showed that P. macrophyllus had the highest ability to retain PM, and C. camphora excelled in retaining PM2.5. The combination of P. macrophyllus and C. camphora was highly recommended to be planted in the subtropical city to effectively reduce PM. The toxic trace elements accumulated in foliar PM varied with plant species and PM size. Two-way ANOVA showed that most of the toxic trace elements were significantly influenced by plant species, PM size, and their interactions (P < 0.05). Additionally, linear regression and correlation analyses further demonstrated the homology of most toxic trace elements in foliar PM, i.e., confirming plants as predictors of PM sources as well as environmental monitoring. These findings contribute to urban air pollution control and landscape configuration optimization.
作者机构：
[Wang, Xiaojun; Wang, Wancai; Zhang, C; Zhang, Chao] Northwest A&F Univ, State Key Lab Soil Eros & Dryland Farming Loess Pl, Xianyang 712100, Peoples R China.;[Peng, Yuanying] Lewis Univ, Coll Arts & Sci, Romeoville, IL 60446 USA.;[Farooq, Taimoor Hassan; Yan, Wende; Chen, Yazhen; Liang, Xiaocui] Cent South Univ Forestry & Technol, Coll Life Sci & Technol, Changsha 410004, Peoples R China.;[Farooq, Taimoor Hassan; Yan, Wende; Chen, Yazhen; Liang, Xiaocui] Natl Engn Lab Appl Forest Ecol Technol Southern Ch, Changsha 410004, Peoples R China.;[Zhang, C; Zhang, Chao; Lei, Shilong] Chinese Acad Sci & Minist Water Resources, Inst Soil & Water Conservat, Xianyang 712100, Peoples R China.
通讯机构：
[Chen, XY ] G;[Zhang, C ] N;[Yan, WD ] C;Northwest A&F Univ, State Key Lab Soil Eros & Dryland Farming Loess Pl, Xianyang 712100, Peoples R China.;Cent South Univ Forestry & Technol, Coll Life Sci & Technol, Changsha 410004, Peoples R China.
关键词：
nutrient;stoichiometry;Masson pine;Slash pine;karst region
摘要：
Ecological stoichiometry plays important roles in understanding the nutrient constraints on tree growth and development, as well in maintaining ecosystem services in forests, yet the characteristics of carbon:nitrogen:phosphorous (C:N:P) stoichiometry in forests under karst environment have not been sufficiently evaluated. In this study, concentration, distribution, stocks of Nitrogen (N) and Phosphorous (P), and ecological stoichiometry were studied in three common forest types: Masson pine natural forests (MPNF), Masson pine plantation forests (MPPF), and Slash pine plantation forests (SPPF) in a karst region of southwestern China. Results showed that N concentrations were higher in overstory than in understory and litter in the studied forests. However, P concentration was relatively low in overstory component of the forested ecosystems. Meanwhile, the N and P concentrations were higher in SPPF in the stem and litter, while these contents were higher in MPPF and MPNP in the overstory and understory. The N and P stocks ranged from 5.7-6.2 t ha(-1), and 0.5-0.6 t ha(-1) in the examined forests. The ecological stoichiometry of C:N:P in the three forest types was similar in litter (46-49:2:1), and relatively steady in soil (250-320:13-16:1) and tree leaf (100-200:14-20:1). Soil P status was the primary limiting factor in affecting tree growth in MPPF and SPPF (N:P ratio > 16), while both N and P conditions were the main restrictive factors in MPNP (N:P ratio = 15) in the study area. Our study provides scientific references and useful datasets of C:N:P stoichiometry for sustainable management of forest ecosystems in karst regions.
