Dataset Information

Evidence of recovery of Juniperus virginiana trees from sulfur pollution after the Clean Air Act.

ABSTRACT: Using dendroisotopic techniques, we show the recovery of Juniperus virginiana L. (eastern red cedar) trees in the Central Appalachian Mountains from decades of acidic pollution. Acid deposition over much of the 20th century reduced stomatal conductance of leaves, thereby increasing intrinsic water-use efficiency of the Juniperus trees. These data indicate that the stomata of Juniperus may be more sensitive to acid deposition than to increasing atmospheric CO2. A breakpoint in the 100-y δ(13)C tree ring chronology occurred around 1980, as the legacy of sulfur dioxide emissions declined following the enactment of the Clean Air Act in 1970, indicating a gradual increase in stomatal conductance (despite rising levels of atmospheric CO2) and a concurrent increase in photosynthesis related to decreasing acid deposition and increasing atmospheric CO2. Tree ring δ(34)S shows a synchronous change in the sources of sulfur used at the whole-tree level that indicates a reduced anthropogenic influence. The increase in growth and the δ(13)C and δ(34)S trends in the tree ring chronology of these Juniperus trees provide evidence for a distinct physiological response to changes in atmospheric SO2 emissions since ∼1980 and signify the positive impacts of landmark environmental legislation to facilitate recovery of forest ecosystems from acid deposition.

SUBMITTER: Thomas RB

PROVIDER: S-EPMC3780865 | biostudies-literature | 2013 Sep

REPOSITORIES: biostudies-literature

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Evidence of recovery of Juniperus virginiana trees from sulfur pollution after the Clean Air Act.

Thomas Richard B RB Spal Scott E SE Smith Kenneth R KR Nippert Jesse B JB

Proceedings of the National Academy of Sciences of the United States of America 20130903 38

Using dendroisotopic techniques, we show the recovery of Juniperus virginiana L. (eastern red cedar) trees in the Central Appalachian Mountains from decades of acidic pollution. Acid deposition over much of the 20th century reduced stomatal conductance of leaves, thereby increasing intrinsic water-use efficiency of the Juniperus trees. These data indicate that the stomata of Juniperus may be more sensitive to acid deposition than to increasing atmospheric CO2. A breakpoint in the 100-y δ(13)C tr ...[more]

PMID: 24003125

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Project description:BackgroundMotor vehicles, including public transit buses, are a major source of air pollution in New York City (NYC) and worldwide. To address this problem, governments and transit agencies have implemented policies to introduce cleaner vehicles into transit fleets. Beginning in 2000, the Metropolitan Transit Agency began deploying compressed natural gas, hybrid electric, and low-sulfur diesel buses to reduce urban air pollution.ObjectiveWe hypothesized that bus fleet changes incorporating cleaner vehicles would have detectable effects on air pollution concentrations between 2009 and 2014, as measured by the New York City Community Air Survey (NYCCAS).MethodsDepot- and route-specific information allowed identification of areas with larger or smaller changes in the proportion of distance traveled by clean buses. Data were assembled for 9670 300 m × 300 m grid cell areas with annual concentration estimates for nitrogen oxide (NO), nitrogen dioxide (NO2), and black carbon (BC) from NYCCAS. Spatial error models adjusted for truck route presence and total traffic volume.ResultsWhile concentrations of all three pollutants declined between 2009 and 2014 even in the 39.7% of cells without bus service, the decline in concentrations of NO and NO2 was greater in areas with more bus service and with higher proportional shifts toward clean buses. Conversely, the decline in BC concentration was slower in areas with more bus service and higher proportional clean bus shifts.SignificanceThese results provide evidence that the NYC clean bus program impacted concentrations of air pollution, particularly in reductions of NO2. Further work can investigate the potential impact of these changes on health outcomes in NYC residents.Impact statementUrban air pollution from diesel-burning buses is an important health exposure. The New York Metropolitan Transit Agency has worked to deploy cleaner buses into their fleet, but the impact of this policy has not been evaluated. Successful reductions in air pollution are critical for public health.

Dataset Information

Evidence of recovery of Juniperus virginiana trees from sulfur pollution after the Clean Air Act.

Publications

Evidence of recovery of Juniperus virginiana trees from sulfur pollution after the Clean Air Act.

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