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Wang H.,CAS Research Center for Eco Environmental Sciences | Wang H.,Beijing Academy of Agriculture and Forestry Sciences | Zhou W.,CAS Research Center for Eco Environmental Sciences | Zhou W.,University of California at Davis | And 5 more authors.
Environmental Pollution | Year: 2012

The O 3 uptake in 17 adult trees of six urban species was evaluated by the sap flow-based approach under free atmospheric conditions. The results showed very large species differences in ground area scaled whole-tree ozone uptake (FO 3), with estimates ranging from 0.61 ± 0.07 nmol m -2 s -1 in Robinia pseudoacacia to 4.80 ± 1.04 nmol m -2 s -1 in Magnolia liliiflora. However, average FO 3 by deciduous foliages was not significantly higher than that by evergreen ones (3.13 vs 2.21 nmol m -2 s -1, p = 0.160). Species of high canopy conductance for O 3 (GO 3) took up more O 3 than those of low GO 3, but that their sensitivity to vapour pressure deficit (D) were also higher, and their FO 3 decreased faster with increasing D, regardless of species. The responses of FO 3 to D and total radiation led to the relative high flux of O 3 uptake, indicating high ozone risk for urban tree species. © 2011 Elsevier Ltd. All rights reserved.


Wang H.,CAS Research Center for Eco Environmental Sciences | Ouyang Z.-Y.,CAS Research Center for Eco Environmental Sciences | Zheng H.,CAS Research Center for Eco Environmental Sciences | Ren Y.-F.,CAS Research Center for Eco Environmental Sciences | Gao F.-Y.,Beijing Teaching Botanical Garden
Chinese Journal of Applied Ecology | Year: 2011

In order to clarify the environmental factors affecting the water use of typical urban tree species Magnolia liliiflora, an investigation was conducted on the responses of M. liliiflora whole-tree sap flow to the air temperature, air relative humidity, radiation, wind speed, soil temperature and water content, and precipitation in Beijing from April to October, 2008. The eight environmen-tal factors affecting M. liliiflora whole-tree sap flow could be divided into three categories, i. e. , evaporative demand index, soil index, and precipitation index. The evaporative demand index (air temperature, air relative humidity, total radiation, wind speed, and vapor pressure deficit) could explain 60% of the variation in the sap flow of individual trees, which presented S-type change trend, i. e. , the sap flow reached an asymptote where higher light and evaporative demands could not cause sap flow to increase further. Soil index (soil temperature and water content) and precipitation index (precipitation amount) had little influence on the sap flow.


Wang H.,CAS Research Center for Eco Environmental Sciences | Wang H.,Beijing Academy of Agriculture and Forestry Sciences | Wang X.,CAS Research Center for Eco Environmental Sciences | Zhao P.,CAS Institute of Botany | And 4 more authors.
Journal of Environmental Sciences (China) | Year: 2012

Transpiration patterns of Aesculus chinensis in relation to explanatory variables in the microclimatic, air quality, and biological phenomena categories were measured in Beijing, China using the thermal dissipation method. The highest transpiration rate measured as the sap flux density of the trees took place from 10:00 am to 13:00 pm in the summer and the lowest was found during nighttime in the winter. To sort out co-linearity, principal component analysis and variation and hierarchical partitioning methods were employed in data analyses. The evaporative demand index (EDI) consisting of air temperature, soil temperature, total radiation, vapor pressure deficit, and atmospheric ozone (O3), explained 68% and 80% of the hourly and daily variations of the tree transpiration, respectively. The independent and joint effects of EDI variables together with a three-variable joint effect exerted the greatest influences on the variance of transpiration rates. The independent effects of leaf area index and atmospheric O3 and their combined effect exhibited minor yet significant influences on tree transpiration rates. © 2012 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences.


Zhang H.,CAS Research Center for Eco Environmental Sciences | Sun X.,CAS Research Center for Eco Environmental Sciences | Yao Y.,CAS Research Center for Eco Environmental Sciences | Wan W.,CAS Research Center for Eco Environmental Sciences | And 14 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2014

The ozone in the stratosphere protects the earth from harm due to ultraviolet radiation, while the ozone in the troposphere might do harm to human beings. Ozone below certain concentration can sterilize the air and do good to organisms, but high ozone concentration does harm to terrestrial ecosystems. Very high ozone concentrations were firstly found as pollutant in the smog of Los Angeles and its toxic effect upon plants received more attention. The rapid urbanization in China has caused the emission of large amounts of NOx and VOCs (the main precursors to O3 formation). Ambient ozone concentration has been the most serious air pollution among many cities in China. In this study, our objectives are: to discern the distribution pattern of ground-level ozone in Beijing; to find whether plants were injured by ambient ozone in Beijing; and to detect the distribution pattern of the damaged plants in this region. We used passive sampler to monitor ozone concentrations at 10 sites in the city and suburb of Beijing from July 1st to August 30 in 2012 and surveyed the foliar ozone symptoms on the basis of the Forest Health Expert Advisory System from August 15 to 19. The results indicated that the ozone concentrations in mountain regions were significantly higher than those in plain regions around Beijing. In the plain region, the ozone concentration in the green belt adjacent to main motorways was lower than that in parks. The mean ozone concentrations in the mountain, the park and the green belt near to main motorway were: 105.39 µg/ m3,68.49 µg/ m3 and 56.54 µg/ m3. Except for the green belt of motorway, 18 species showed typical ozone symptoms both in mountain and in plain regions. These plants are: Parthenocissus quinquefolia, Juglans regia, Ailanthus altissima, Pharbitis purpurea, Morus alba, Ulmus pumila, Sophora japonica, Sophora japonica f. flavi-rameus, Hibiscus syriacus, Kerria japonica, Hyptis suaveolens, Cassia tora, Populus tomentosa, Salix caprea, Sanguisorba sitchensis, Rhus typhina, Glycine max, Helianthus annuus. Ailanthus altissima was native and popular in mountain and plain around Beijing and its ozone symptoms was easy to diagnose. Therefore, Ailanthus altissima might work as bio-indicator of ozone in Beijing. © 2014, Science Press. All rights reserved.


Wang H.,CAS Research Center for Eco Environmental Sciences | Wang H.,Beijing Academy of Agriculture and Forestry Sciences | Ouyang Z.Y.,CAS Research Center for Eco Environmental Sciences | Ren Y.F.,CAS Research Center for Eco Environmental Sciences | And 5 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2013

The accelerating global urbanization caused severe air pollutions. In Beijing, the air pollution has been exacerbated due to the wide-spread construction activities and increasing number of vehicles. The increasing concentration of ozone (O3) in the troposphere has been recognized as a source of air pollution, due to its adverse effects on human health and plant and animal growth, and its contribution to global climate change. O3 is known to impact forest trees in many ways including morphological and histological injuries, decreasing photosynthesis, increasing respiration, and alteration of carbon allocation and water balance. Considerable researches have been conducted to investigate ozone uptake by urban forests at the regional scale. On the other hand, trees are able to improve urban air quality by taking up and removing gaseous pollutants, and the O3 uptake by urban forests at the regional scale has been extensively studied. However, research on O3 uptake by urban trees at the canopy scale is rare. The main objectives of this study are: (1) to quantify the whole-tree O3 uptake by Robinia pseudoacacia, one of urban greening tree species in Beijing; and (2) to examine how O3 flux in R. pseudoacacia trees is regulated by the stomata and environmental conditions. In this study, the whole-tree O3 uptake in R. pseudoacacia trees during spring and summer was estimated based on sap flow measurements and the data of micro-climate and ambient O3 concentration were also collected. The diurnal ozone uptake rate (FO3) by R. pseudoacacia showed a single peak pattern with the maximum rate occurring at around 15:00 pm. The diurnal FO3 showed a narrow peak during summer and a wide peak during autumn. The most obvious increase in accumulated stomatal ozone flux(AFst)occurred around noon time. FO3 showed a seasonal pattern with higher values found in summer than in autumn. The increase in AFst was most obvious in summer than in autumn. The diurnal and seasonal patterns of O3 uptake were related to the temporal variations of ambient air O3 concentrations and canopy conductance (GO3). Ambient air O3 concentration showed a similar diurnal and seasonal pattern to FO3. Under a given ambient air O3 concentrations, the whole-tree FO3 was dependent on canopy conductance, and hereby was further influenced by the vapour pressure deficit (D) and total radiation (Rs). GO3 decreased exponentially with increasing D. High D caused low GO3, and thus low FO3 in spite of relatively high ambient air O3 concentrations. On the contrary, GO3 was high under low D conditions, and thus FO3 was high in spite of relatively low ambient air O3 concentrations. However, FO3 was relatively low under very low D conditions, such as in early mornings, which may be attributed to the weak photosynthesis and small stomatal apertures in the early morning at this time. Moreover, GO3 decreased rapidly with increasing Rs when Rs was higher than 600 W/m2. Similarly, ambient air O3 concentration decreased with increasing Rs when Rs was higher than 800 W/m2. Therefore, FO3 exhibited an asymmetric single-peak pattern: FO3 slightly increased with increasing Rs when Rs was below 800 W/m2, however, it decreased rapidly with increasing Rs when Rs was higher than 800 W/m2. The annual O3 uptake by R. pseudoacacia trees estimated in our study was 0.16 g/m2, which was much lower than the values estimated from the Urban Forest Effects Model. This difference suggests the necessity to consider the O3 uptake flux on canopy level when evaluate the O3 risks on urban trees.

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