Bryological and Lichenological Section/ABLS
Clark, Theresa .
Filling grand gaps: expanding our knowledge of bryophyte diversity in Grand Canyon National Park.
Ecological diversity within Grand Canyon National Park (GRCA) encompasses a large proportion of the climatic, geologic, and biotic gradients found across the Colorado Plateau, an extensive, mile-high plateau located in the Four Corners region of the American Southwest. Although bryophyte abundance and diversity in this region is low relative to mesic systems, these bryophytes contribute substantially to plant biodiversity and many ecosystem services. The only extensive bryological work in GRCA was completed in the mid 1940's and consequently, bryophyte diversity in this park has remained largely underestimated. Furthermore, little is known about the community ecology of arid rock-inhabiting bryophytes, which comprise the most abundant and frequent bryophyte assemblages in the park. I expanded the known bryoflora of GRCA by 180% and thereby present a modern flora of 155 bryophyte taxa (153 species, 2 varieties). Notable records include 28 taxa newly reported for Arizona, 107 taxa new to GRCA, and three species undescribed or new to science. In summary, the bryoflora of GRCA is 1) distributed across the entire elevation gradient in low abundance but with high frequency, 2) is dominated by acrocarpous mosses found throughout western North America, and 3)is most diverse in the mixed conifer forests of Grand Canyon's North Rim. Secondly, I explored whether the richness, abundance, diversity, and composition of rock bryophyte communities differed significantly among the pinyon-juniper, ponderosa pine, and mixed conifer forests of GRCA. It was desirable to determine if forest type, a surrogate for climatic variation, could provide a simple framework for monitoring patterns in these bryophyte communities. Bryophyte abundance and richness were estimated using a 100 x 1 cm transect placed randomly on three rocks at each of 104 sites along trail corridors stratified by forest type. Three main findings emerged: 1) bryophyte richness, cover, and diversity differed significantly between two of the forest types, 2) community composition on rocks differed significantly among all forests, and 3) elevation and rock type (sandstone, limestone, and chert) were strongly related to bryophyte community composition. The majority of unexplained variation (80 - 90%) in these bryophyte responses was potentially due to rock microhabitat variability and the stochastic nature of bryophyte dispersal. My results suggest that forest type is not a sufficient framework for monitoring these bryophyte communities in GRCA. Overall, this floristic and ecological investigation provides a foundation for future research in the community dynamics of bryophytes in arid ecosystems of the American Southwest.
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1 - Northern Arizona University, Biology, 617 S. Beaver St. PO Box: 5640, Flagstaff, AZ, 86001, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 9th, 2012
Time: 3:30 PM