A study of lichen coverage of different species in selected sites of San José City, Costa Rica.

Lichen coverage in tree trunks was measured as an estimate of pollution in three different locations of San José’s Central County and two additional sites, the University Campus Rodrigo Facio and Los Yoses Boulevard in Montes de Oca County. Lichen collects were also carried out in all sites for identification purposes. Differences in lichen coverage were found among sites (ANOVA Kruskal-Wallis: H = 26.667, 3 g.l., n = 60, p < 0.001) observing less coverage in two locations of San José’s Central County and los Yoses when compared to lichen coverage in University Campus Rodrigo Facio and the Parque Nacional. In addition, the lichen species found in the low cover sites, were different from those found in the other stations. Certain species seem more resistant to the vehicle gases and thus tend to colonize the most contaminated sites studied. These were members of the genus Physcia sp. and Dirinaria applanata predominantly foliose with narrow lobes, and members of the genus Lecanora a crustose lichen with relatively lower contact surface with the air. Overall, the average cover was 36%, higher than the 1997 value of 22% obtained by Monge-Nájera et al. (2002a). The reduction of lead in vehicle emissions and the introduction of the vehicular technical revision might be factors contributing to this finding. The building of parks and wide areas with high tree densities in urban settings not only contributes to pedestrian recreation but possibly also aids in mitigating the high levels of vehicle contamination produced in those regions.