Bioindication of air quality in forests of northern and central California using epiphytic macrolichen communities.

摘要

The unifying purpose of this dissertation was to describe, model, and map relationships between epiphytic macrolichen communities and air quality in forests of northern and central California. First, multivariate analyses were used to subdivide the large study area into three model areas with similar climate, topography, and lichen communities: the NW Coast, the greater Central Valley, and the greater Sierra Nevada. Dividing the study area helped to reduce within model-area environmental variability, which may otherwise overpower lichen community responses to more localized pollutant gradients.; We then developed a gradient model for the greater Central Valley using lichen community surveys from 98 forested sites. Non-metric multidimensional scaling related community composition to climate, geography, stand characteristics, and common anthropogenic pollutants including ammonia, nitrogen dioxide, ozone, and sulfur dioxide. One prominent lichen community gradient was related to ammonia deposition as evidenced by an index of known indicator species, the proportion of nitrophile abundance. We used the model to estimate relative ammonia deposition to each sampled forest. A second community gradient correlated with ozone, nitrogen dioxide, and a coast-to-inland humidity gradient. Because little is known about lichen community responses to ozone and nitrogen dioxide, we could not clearly differentiate pollution vs. climate effects along that gradient.; Lastly, we derived a gradient model for ammonia bioindication in the greater Sierra Nevada. We used nonlinear regression to correct the model for elevation effects, which appeared to confound the lichen community response to ammonia. We used the adjusted model to estimate relative ammonia deposition to 115 forested sites and geographic patterns were descriptively compared to preexisting direct monitoring data. Sources of noise and the underlying mechanism of the ammonia-nitrophile relationship are discussed. Ammonia bioindication is particularly important in California due to high emissions from automobile exhaust and agriculture. Furthermore, ammonia deposition is not measured directly by state or federal agencies. Other pollutants, like ozone and nitric acid, are also believed to be negatively affecting forest health in the region. More basic research is needed, however, to determine whether lichens are viable indicator species for these pollutants.