Cryptogam communities in forest and steppe ecosystems of Oregon, USA Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/rr172164f

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  • I focus on addressing knowledge gaps relating to management of cryptogams in Oregon's public lands in Pseudotsuga menziesii-Tsuga heterophylla forests on the west side of the Cascade Range and dryland steppe in the Cascade Range's rainshadow. While a great deal of research has illustrated the importance of late-successional forests for maintaining biodiversity in the Pacific Northwest of North America, over 76% of the forests in the region are less than 100 years old. To preserve landscape-level biodiversity, forest managers are increasingly interested in how young stands can be manipulated to favor late-successional species. At two sites in moist conifer forests of western Oregon, lichen community monitoring plots were established prior to treatment and resampled approximately 10 years after alternative thinning treatments aimed at promoting late-successional strucural characteristics. At both sites, hardwood gaps and open-grown trees were positively associated with cyanolichen species richness. At one site, thinned plots hosted more Bryoria, Candelaria concolor, Leptogium polycarpum, Peltigera collina, Nephroma laevigatum and Physcia tenella than had been observed prior to thinning. I concluded that thinning treatments retaining remnants, open-grown trees and hardwood gaps have potential to favor lichen communities rich in cyanolichen and alectorioid species. In the same sites, I sought to understand how stand-level gradients in canopy structure relate to dominant forest floor bryophyte and lichen species composition and abundance. At the one site, I found no strong associations between forest floor communities and stand structural characteristics. At the the other, lichens, particularly Cladonia, were negatively associated with canopy cover whereas bryophyte abundance was positively associated with Tsuga basal area. This relationship was stronger in the thinned stands, which had a different community composition than those left unthinned. Overall, the forest floor communities were fairly homogeneous at both sites and relationships with stand structural variables were subtle, indicating that thinning did not have a strong impact. Biological soil crusts are ecosystem engineers in arid and semi-arid habitats; they affect soil chemistry, stability, and vegetation. Little is known about regional variation in biotic crust communities of North America. I explored how biotic crust lichen community composition and richness related to vascular plant, soil and climate characteristics in Oregon. In 59 0.4-ha plots, I found 99 biotic crust lichen taxa, one-third of which were observed only once, 33 of which occurred in only one plot and seven of which were new to Oregon. I compiled records from herbaria and other studies to evaluate the rarity of 124 biotic crust lichen species and conclude that 37 are rare or uncommon. Many of these appear to be associated with calcareous substrates. I modeled occurrences in relation to climate and soil variables for four uncommon biotic crust lichens: Acarospora schleicheri, Fuscopannaria cyanolepra, Rhizocarpon diploschistidina, and Texosporium sancti-jacobi. Based on climate and soils, I mapped regions of Oregon that may support new populations of these species and overlay habitats unsuitable for biotic crusts due to development and agriculture. These species, except Fuscopannaria cyanolepra, are strongly associated with the fine soils along the Columbia and Treasure Valleys that are most intensively used for agriculture. Biotic crust lichen communities rich in cyanolichens characterized Juniperus stands whereas warm grasslands were home to regionally uncommon species including Texosporium sancti-jacobi and Rhizocarpon diploschistidina. I discerned biotic crust communities in sandy Artemisia tridentata ssp. wyomingensis sites from those loamy A. arbuscula sites. Hotspots of biotic crust diversity were geographically scattered, weakly negatively associated with abundance of shrubs of disturbed sites, Gutierrezia and Chrysothamnus. The poorest sites for biotic crust lichen richness were heavily grazed, burned plots with Gutierrezia in the grassy north, unstable steep talus slopes at the center, and sandy, grazed sites with Chrysothamnus in the southern portion of our region. Overall, regional patterns in biotic crust lichen communities were strongly associated with vegetation, soils, and climate. I hope that my findings will promote intentional management of epiphytic and forest floor cryptogams of western Oregon forests and monitoring of biotic lichen communities in eastern Oregon.
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