Joshua Tree National Park AQRV's
Surface waters are rare in Joshua Tree NP and include a number of fan palm oases where water occurs naturally at or near the surface, and occasional springs. Surface waters in the park may be sensitive to enrichment (i.e., fertilization) from nitrogen deposition. Enrichment could result in algae blooms and decreased dissolved oxygen and water quality. No studies have been conducted to assess enrichment effects in park waters. Surface waters do not exhibit any of the characteristics (low ANC, low alkalinity) normally associated with sensitivity to acidification from atmospheric deposition. Base cations in soils and rocks occur in sufficient quantities to neutralize acidity from nitrogen or sulfur deposition.
Fauna/Wildlife
Impacts to wildlife from air pollution in the park have not been directly studied. However, vegetation changes caused by air pollution may affect wildlife dependent on that vegetation.
Night Skies
Dark night skies are considered an important air quality related value at Joshua Tree NP, possessing value as a cultural, scenic, natural, and scientific resource. Air pollution and poor quality outdoor lighting degrade night skies, lessening a viewer's ability to see stars and other astronomical objects, and altering the nocturnal scene. Use of high quality lighting that produces very little scattered light can greatly improve the night sky. Reduction of haze from air pollution can also improve the night sky.
Soils
Soils in Joshua Tree NP may be sensitive to atmospheric deposition of nitrogen compounds. In some areas of the country, elevated nitrogen deposition has been shown to alter soil nutrient cycling. Near the park, soil nitrogen levels are significantly elevated due to high levels of atmospheric deposition. Studies are being conducted to evaluate the effects of excess nitrogen on soil dynamics in Joshua Tree NP.
Vegetation in Joshua Tree NP is being affected by the high levels of air pollution in the park. Excess nitrogen deposition is contributing to increases in exotic grasses and overall plant biomass, resulting in increased risk of fire. Fire frequency increases when plant biomass exceeds about one ton per hectare (2.5 acres). In the park this biomass threshold is predicted to be exceeded when nitrogen deposition is at 6.5 kilograms per hectare per year. This amount of nitrogen deposition is the critical load for increased fire frequency, and is currently exceeded in many areas of the park. Fires alter park ecosystems by reducing the diversity and density of native shrubs. In addition, high levels of ozone may cause foliar injury and growth effects. Several plant species that occur in Joshua Tree NP are known to be sensitive to ozone.
In addition, high levels of ozone may cause foliar injury and growth effects. Several plant species that occur in Joshua Tree NP are known to be sensitive to ozone.
- Ozone Sensitive Plant Species Listed by Park
- Ozone Sensitive Plant Species on NPS and U.S. FWS Lands
- Ozone Bioindicators on NPS and U.S. FWS Lands
Visibility
Visibility is a sensitive AQRV at Joshua Tree NP. Visibility impairment (haze) due to fine particle pollution has been frequently documented at Joshua Tree NP and in areas throughout southern California.