Outline of Quino Recovery Plan - The Xerces Society

per year) (Bytnerowicz et al. 1987, Fenn et al. 1996). Most nitrogen arrives
during the dry season as nitrate dryfall (particulate and ion deposition to
surfaces) produced by internal combustion engines. Soils in the most polluted
regions near Riverside have more than 80 parts per million (weight) extractable
nitrogen, a value more than 4 times that detected in natural, unpolluted soils
(Allen et al. 1998, Padgett et al. 1999).
Nitrogen fertilization experiments near Lake Skinner (where air pollution is
relatively low) demonstrated that after 4 years the cover and biomass of
nonnative grasses increased and native shrub canopy decreased (Allen et al.
2000). These experiments suggest that the rate of loss and degradation of Quino
checkerspot habitat will continue, and may increase, in and near nitrogen
polluted lands. Nitrogen deposition in southern California is less severe in
coastal than inland areas because prevailing winds move pollution inland
(Padgett et al. 1999). High emissions from nitrogen sources in Mexico could
threaten adjacent Quino checkerspot populations in California.
7. Effects of Increasing Atmospheric Carbon Dioxide Concentration
Increasing carbon dioxide gas has direct effects upon the vegetation and indirect
effects on associated insects. Atmospheric concentrations of carbon dioxide
have risen from a stable 270 parts per million volume prior to the 1900's, to 364
parts per million volume today, and continue to rise at a rate of 0.4 percent per
year (IPCC 1996). Unlike atmospheric nitrate or ammonium that deposit along
gradients from the source of emissions, carbon dioxide is globally mixed and
thus has global impacts (IPCC 1996). Carbon dioxide has been shown to affect
plants primarily through increased growth and photosynthesis rates, an increase
in leaf tissue (foliar) carbon to nitrogen ratio (C:N), and increased production of
carbon-based defense compounds (IPCC 1996, Coviella and Trumble 1999).
Increased plant productivity and biomass in chaparral (Oechel et al. 1995) and
coastal sage scrub will likely contribute to increased canopy closure and
reduction of habitat favored by the Quino checkerspot. Chemical changes in
plant tissue have been found to affect food quality for herbivores, and often
resulted in reduced performance of leaf-eating insects (reviews by Lindroth
1995, Bezemer and Jones 1998, Coviella and Trumble 1999, and Whittaker
1999).
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