Forest Inventory and Analysis National Program

Lichen Communities

Results

The plot work conducted in 1998-99 will provide the plot data needed for the construction of air quality and climate gradient models in the Pacific Northwest and California. Assessment of the status of these plots and long-term change will arise from these models. Supplemental (off-frame) plots for the gradient model of Oregon and Washington's west side have been completed, and the model is expected by late 2001. Field work for gradient models for California will begin in the summer of 2001, with gradient models expected by 2003. The plot results summarized below are useful for portraying landscape level patterns of species richness and community variation, but cannot be interpreted for air quality results until the completion of the gradient models.

Pacific Northwest

A total of 178 species were found in the 282 on-frame, off-frame and QA plots conducted in 1998 and 1999 (Fig. 1). The mean species richness per plot was 17 species, approximately 70% higher than that for California (10) and 89% higher than that in Idaho (9). In the 1998 data, the region west of the Cascades hosted approximately 60% higher total number of species than the east side. Beta diversities of 7 and 6 for the west-side and east-side respectively suggested that no more than 2 distinct lichen community types existed in either region. The mean lichen species richness in Washington's west side was approximately 13, while the mean in Oregon's west side was approximately 20. Plots in the Washington Cascades had generally lower species richness scores than those in the Oregon Cascades.

Air quality is likely to be involved in the low species richness scores found in many west-side sites in Oregon and Washington (Fig. 1), though final determination of the presence and extent of the problem will await the upcoming regional gradient model. In off-frame plots, sites in the urban areas of Seattle and Portland and the immediate vicinity had fairly low to intermediate species richness for this zone (9-17 species with mean of 12), and are probably hosting lower diversity than they would be in a clean air regime. Given the high proportion of hardwoods in the Willamette Valley and the high lichen diversity generally found on hardwoods (ca. 40 species at the 1999 Corvallis training, and a mean of 40 species in 18 special study plots south of Eugene), we might expect a higher diversity in this parts of this area given clean air conditions and/or favorable stand structures.

Forest structure is likely to be playing a role in the low diversity in some sites as well. The Oregon Cascades have generally medium to high diversity, although there are many presumably clean-air Cascadian sites whose diversity is low (<10 species). Species richness, where poor in this zone, appears to have been negatively influenced by the current forest age and/or structure. Of particular relevance, several other studies have demonstrated that young managed stands host relatively few species compared to mature forest, and likewise, densely stocked, dark stands host far fewer species than stands with open structure (Neitlich 1993, Neitlich and McCune 1997, Peck et al. 1997).

The 1998-9 findings greatly contributed to our knowledge of the region's flora. Many new point locations were found for the new Xanthoria species recently clarified by Louise Lindblom (1997) in her monograph of North American Xanthoria of North America. These species include X. fulva, X. hasseana, X. fallax, X. oregana, and X. polycarpa. The bulk of species on the eastern Pacific Northwest sampling grid which would have been formerly classified as X. fallax were in actuality X. fulva; likewise, the bulk of species in the Pacific Northwest's west-side formerly classified as X. fallax were in fact X. oregana.

Several species uncommon in our area were found including Hypogymnia duplicata, Hypogymnia oceanica (endemics of southeast Alaska and BC), and Bryoria nadvornikiana (typically in the boreal forest). Eight new datapoints were identified for the Forest Service's Survey and Manage category 1&3 species, some of the most sensitive macrolichen species in the Pacific Northwest . Additionally, the range of the recently described Physcia dimidiata, a foliose lichen of the Juniper woodland zone, was also expanded with point data through this survey. In 1999, crews were given information about rare coastal species in an effort to combine this survey effort with broader floristic data needs.

California

A total of 105 species were found in the 76 California on-frame, off-frame and QA plots in 1998 (Fig 2). Species richness was predictably low given the relatively dry climate, with a 1998 mean of 9.6 species per plot. Northwest and north central California had much higher species richness than any southern or eastern areas. The high beta diversity in the on-frame data indicates that several distinct lichen communities are likely to be present, a result consistent with the high diversity of California's geography and vegetation. The steep natural gradients in lichen community composition combined with the small sample size over a large area make inferences about anthropogenic impacts especially difficult prior to a gradient model. For instance, relatively high species richness in montane areas does not imply an absence of impacts to lichens there or imply conversely the presence of impacts at low elevations where species are fewer.

We should certainly expect pollution-related declines around large urban areas, and starting in 2002, we will sample urban/industrial and known clean air sites in California as part of a gradient model data set. Prior to that, we have several concerns about potential pollution effects on lichen communities:

• First, observational evidence of extremely low lichen abundance and diversity around the Bay Area in contrast to surrounding areas is suggestive of air quality impacts.
  
  
• Second, nitrification from fertilizer use in the Central Valley is likely to be playing a role in the abundance of nitrophilous species in the genera Xanthoria and Physcia seen in adjacent areas. In FIA monitoring, nitrophilous species tend to be highly associated with semi-desert ecoregion provinces. This association is due in part to the naturally high deposition of soil nitrogen via dust in semi-arid areas, although the extent to which anthropogenic sources have contributed to a bloom of these taxa is unknown. While a small group of lichen taxa respond positively to nitrogen enrichment, a much larger group exhibits deleterious effects including dieback, deformities, cancer-like growths, and dissociation of the algal and fungal partners of the lichen (Kauppi 1980).
  
  
• Third, we speculate that the air pollution plume from both Orange County (Los Angeles area) and the Bay Area is likely to have an effect on downwind oak woodland (Quercus spp.) communities. In clean air conditions, these should normally host a high diversity of lichens including the charismatic Ramalina menziesii. This species has been one of the most showy and abundant members of the oak woodlands, especially in fog zones (McCune and Geiser 1997), but is pollution sensitive and has declined due to poor air quality and habitat loss. Floristically, this oak community is of great importance, and is likely to hold equal or higher lichen diversity than the coniferous forests of the mid-elevations on the west side in clean air situations.

Several regionally uncommon species were found including Parmotrema austrosinense, and Bryoria tortuosa. The former species is rare in California, and known primarily from the South Coast Ranges (Hale and Cole 1988). In this study, the species was found surprisingly far north of there, just north of the Bay Area. B. tortuosa is uncommon generally, and was found close to the Oregon border. This lichen has become increasingly rare due to the destruction of its habitat in the interior, transitional areas at the edge of the mountains.

An interesting issue raised by California data is the sparseness of epiphytic lichens in the Eastern Sierra floristic province, even amidst a very robust population of rock-dwelling species. Plots ranged from 0-4 epiphytic species in this zone, in which air quality is surmised to be intermediate or clean. Diversities are similarly low throughout most of the High Sierra and White Mountains even though a large volume of old to ancient trees (e.g., Bristlecone Pine and Foxtail Pine >1500 years old) abound. By contrast, lichen communities in the east-side areas near Susanville are robust and diverse, resembling much more the east side lichen communities of the Pacific Northwest. Moisture regime is likely to be responsible, but in a manner that is currently unknown given the abundance of rock-dwelling species (e.g., Rhizoplaca spp., Xanthoria elegans, Caloplaca saxicola, Acarospora chlorophana, etc.). Host tree species may additionally play a role. For instance, lodgepole pine (Pinus contorta) is a relatively poor host for lichens even in the favorable climate of the western Cascades, and is one of the most common trees at mid to upper elevations in California's east side.