• Giant Sequoia Trees

    Sequoia & Kings Canyon

    National Parks California

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  • The Generals Highway "Road Between the Parks" is OPEN

    The section of road between Lodgepole (Sequoia) and Grant Grove (Kings Canyon) is open. Call 559-565-3341 (press 1, 1) for 24-hour road updates.

  • Be Prepared! Tire Chains or Cables May Be Required in the Parks at Any Time

    All vehicles must carry chains or cables when entering a chain-restricted area. It's the law (CA Vehicle Code, Section 605, Sections 27450-27503). Road conditions may change often. For road conditions, call 559-565-3341 (press 1, 1). More »

  • You May Have Trouble Calling Us

    We are experiencing technical problems receiving incoming phone calls. We apologize for the inconvenience. Please send us an email to SEKI_Interpretation@nps.gov or check the "More" link for trip-planning information. More »

  • Vehicle Length Limits in Sequoia National Park (if Entering/Exiting Hwy 198)

    Planning to see the "Big Trees" in Sequoia National Park? If you enter/exit via Hwy. 198, please pay close attention to vehicle length advisories for your safety and the safety of others. More »

Air Quality -- Ozone

Two pine trees, one with thin yellowed needles, the other with thick green needles

Two neighboring pines of the same species respond differently to ozone, exhibiting genetic variability. The pine on the left shows needle damage from ozone and the one on the right appears healthy.

NPS Photo

Good and Bad Ozone

Ozone is made of three joined oxygen atoms, and it is found both in the Earth's upper atmosphere and at ground level. Ozone can be helpful or harmful, depending on where it is found:

Good ozone occurs naturally in the Earth's upper atmosphere (stratosphere)- 10 to 30 miles above the Earth's surface - where it shields us from harmful ultraviolet rays.

Bad ozone forms near the ground (lower troposphere) when pollutants from cars, power plants, and other sources react chemically. Sunlight provides the energy that drives this chemical reaction, so the amount of ozone in the atmosphere is highest on summer afternoons.

Ozone may be the most damaging pollutant here. Individual ponderosa and Jeffrey pine trees that are ozone-sensitive show extensive injury to their foliage at present ozone levels. For example, one study found that nearly 90% of Jeffrey pines in or near the Giant Forest showed visible signs of ozone injury. Compared to ozone-resistant individuals, ozone-sensitive pines have lower photosynthetic rates, lose their needles earlier, and have diminished annual ring growth. In contrast to pines, mature giant sequoias seem to be relatively resistant to present ozone levels. However, newly emerged sequoia seedlings are suspected to be more vulnerable to ozone injury.

 
These pine needles demonstrate chlorotic mottling (or a yellowing effect), characteristic of ozone damage. Ozone damages chlorophyll in the needles, reducing or destroying their ability to photosynthesize (or make food for the plant).

These pine needles demonstrate chlorotic mottling (or a yellowing effect), characteristic of ozone damage. Ozone damages chlorophyll in the needles, reducing or destroying their ability to photosynthesize (or make food for the plant).

NPS Photo

We humans are very vulnerable to ozone damage too. It can irritate the human respiratory system causing coughing, irritation in the throat, and/or an uncomfortable sensation in the chest. The elderly and those with pre-existing respiratory problems (e.g. asthma, bronchitis) are more vulnerable to these effects.

For further information, visit the Environmental Protection Agency AirNow Web Site.

Did You Know?

Low fire burns through a grove during a prescribed burn.

Fire is an essential part of Sierra forest ecology. Plants and animals have adapted to the periodic, low-intensity fires that naturally occur here. In fact, sequoias need fire to open their cones and release the seeds, and to leave cleared beds of ash where they sprout and grow best.