Ozone uptake by adult urban trees based on sap flow measurement

Wang, Hua; Zhou, Weiqi; Wang, Xiaoke; Gao, Fuyuan; Zheng, Hua; Tong, Lei; Ouyang, Zhiyun

doi:10.1016/j.envpol.2011.11.026

Cited by 26 publications

(15 citation statements)

References 65 publications

(94 reference statements)

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“…A logical way to improve air quality is the reduction of emissions of air pollutants (Duncan et al, 2016;EEA, 2016), but it has been suggested that urban vegetation, especially trees, which can absorb and capture air pollutants with their large leaf area, could be also used to clean polluted urban air (Beckett et al, 2000;Nowak et al, 2006). For example, gases such as NO 2 (Chaparro-Suarez et al, 2011;Hu et al, 2016;Rondón & Granat, 1994;Takahashi et al, 2005) and O 3 (Hu et al, 2016;Manes et al, 2012;Wang et al, 2012) are absorbed from air through the stomata into the leaf interior of a plant. Such uptake of air pollutants by urban plants is often considered to result in effective ambient air quality improvement in city-scale and consequently to provide an important ecosystem service (e.g.…”

Section: Introductionmentioning

confidence: 99%

Trees in urban parks and forests reduce O3, but not NO2 concentrations in Baltimore, MD, USA

Yli‐Pelkonen

Scott

Viippola

et al. 2017

Atmospheric Environment

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Trees and other vegetation absorb and capture air pollutants, leading to the common perception that they, and trees in particular, can improve air quality in cities and provide an important ecosystem service for urban inhabitants. Yet, there has been a lack of empirical evidence showing this at the local scale with different plant configurations and climatic regions. We studied the impact of urban park and forest vegetation on the levels of nitrogen dioxide (NO 2) and ground-level ozone (O 3) while controlling for temperature during early summer (May) using passive samplers in Baltimore, USA. Concentrations of O 3 were significantly lower in treecovered habitats than in adjacent open habitats, but concentrations of NO 2 did not differ significantly between tree-covered and open habitats. Higher temperatures resulted in higher pollutant concentrations and NO 2 and O 3 concentration were negatively correlated with each other. Our results suggest that the role of trees in reducing NO 2 concentrations in urban parks and forests in the Mid-Atlantic USA is minor, but that the presence of tree-cover can result in lower O 3 levels compared to similar open areas. Our results further suggest that actions aiming at local air pollution mitigation should consider local variability in vegetation, climate, microclimate, and traffic conditions.

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Section: Introductionmentioning

confidence: 99%

Trees in urban parks and forests reduce O3, but not NO2 concentrations in Baltimore, MD, USA

Yli‐Pelkonen

Scott

Viippola

et al. 2017

Atmospheric Environment

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“…Considering the radial variation of sap flux density, the generalized Gaussian function in describing the radial profile of gymnosperm sap flux density [53] was applied to calculate the mean sap flux density (J tree , g cm −2 s −1 ) for each sampled tree by the measured sap flux density (J) and the corresponding relative sapwood depth (i.e., the ratio of the measuring depth to the sapwood depth) (see details in Litvak et al [54] and Wang et al [55]). The validity of this function for Pinus tabuliformis could be justified by observations of Sun et al [56] and Wang et al [47], and we assumed that possible estimation uncertainties generated by unknown thinning effects on radial profiles were minor.…”

Section: Sap Flow Measurements and Transpiration Calculationmentioning

confidence: 99%

Sparse Pinus Tabuliformis Stands Have Higher Canopy Transpiration Than Dense Stands Three Decades After Thinning

Chen

Zhang

Chen

et al. 2020

Forests

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Hydrological effects of forest thinning have been studied at small watershed scales using the paired watershed approach since the 1920s. However, how forest transpiration, a critical component of evapotranspiration, changes decades after thinning is not well understood despite its importance for modifying drought resilience of forest ecosystem under climate change. In a semi-arid mountainous area of northern China, we measured growing season sap flow of Pinus tabuliformis, a widely planted afforestation species, in 44-year-old monoculture plantation stands with low (983 stems ha−1), medium (1688 stems ha−1), and high (2160 stems ha−1) density. Three decades after thinning, diameters at breast height (DBH) were larger in sparse stands than in dense stands. While its relation with sapwood area was density independent, the accompanying high sapwood area at the tree level for sparse stands resulted the highest stand sapwood area in the medium density stand (33.26 m2 ha−1), rather than in the high density stand (29.84 m2 ha−1). Similar to short-term studies, sparse stands demonstrated higher sensitivity to climatic fluctuations and drought depressions than dense ones. Nevertheless, stand density had no effect on the isohydric strategy of Pinus tabuliformis. Contrary to the positive relation between stand density and stand canopy transpiration soon after thinning, sparse stands exhibited higher growing season canopy transpiration than dense stands three decades later. In the dry year 2014, these density differences were relatively most pronounced, with July-September transpiration totals of 56.7 mm, 31.1 mm, and 22.1 mm in the low, medium, and high density stands, respectively. Our findings highlighted that stand density was not an appropriate indicator of thinned forest transpiration over long time scales. Interactions between soil droughts and thinning on forest transpiration need to be further clarified, especially in longer periods of time.

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“…Most previous studies conducting modelling-based evaluation, such as observations of 86 cities in Canada, 10 metropolitan cities in Italy, and areas in Florence (Italy) and Strasbourg (France) [14][15][16][17], demonstrated that urban forests are capable of reducing O3 levels. In addition, studies using sap flow measurements and eddy covariance systems to investigate the effect of urban trees on O3 showed that urban trees can remove O3 though the canopy stomata uptake and non-stomatal deposition [18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal Ozone Level Variation in Urban Forests in Shenzhen, China

Duan¹,

Wang²,

Pei³

et al. 2019

Preprint

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Research Highlights: This study is among the first to investigate ozone levels in urban forests in China. It establishes that urban forest air quality in Yuanshan Forest Park, Shenzhen, is suitable for recreational activities and identifies spatial, seasonal, and diurnal O3 patterns and relationships with micrometeorological parameters, suggesting the possibility of manipulating relevant forest characteristics to reduce O3 levels. Background and Objectives: An understanding of O3 levels of urban forest environments is needed to assess potential effects on human health and recreational activities. Such studies in China are scarce. This study investigated urban forest O3 levels to improve understanding and support residents engaging in forest recreational activities. Materials and Methods: We monitored O3 levels in 2015–2016 for three urban forests representing common habitats (foothill, valley, and ridge) in Yuanshan Forest Park, Shenzhen, and for an adjacent square. Results: The overall mean daily and daily maximum 8-h mean (MDA8) O3 concentrations were highest for the ridge forest and lowest for the valley forest. Each forest’s O3 concentrations were highest in summer. Diurnally, forest O3 concentrations peaked between 13:00 and 17:00 and reached a minimum between 03:00 and 09:00. The correlation between forest O3 concentrations and air temperature (AT) was strongly positive in summer and autumn but negative in spring. In each season, O3 concentration was negatively correlated with relative humidity (RH). No MDA8 or hourly O3 concentrations in the forests exceeded National Ambient Air Quality Standard Grade I thresholds (100 and 160 μg m−3, respectively). Conclusions: O3 accumulation is present in ridge urban forest in all seasons. Foothill and valley urban forests have better air quality than ridge forestation. Urban forest air quality is better in spring and autumn than in summer and is better from night-time to early morning than from noon to afternoon.

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Ozone uptake by adult urban trees based on sap flow measurement

Cited by 26 publications

References 65 publications

Trees in urban parks and forests reduce O3, but not NO2 concentrations in Baltimore, MD, USA

Trees in urban parks and forests reduce O3, but not NO2 concentrations in Baltimore, MD, USA

Sparse Pinus Tabuliformis Stands Have Higher Canopy Transpiration Than Dense Stands Three Decades After Thinning

Spatiotemporal Ozone Level Variation in Urban Forests in Shenzhen, China

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