Tuesday, August 7, 2007

PS 32-158: Initial surveys of cryptogam communities in the northeastern Cascade range: The road to function

Robert G. Jespersen, University of Washington

Traditional models of alpine community organization have undergone revision in recent years as evidence accumulates in support of facilitation as a primary structuring force.  However, this recognition of the importance of biotic interactions has focused almost entirely on plant-plant relations.  In the North Cascade and Olympic ranges, thin layers of lichens and bryophytes are ubiquitous components of high-elevation communities, yet the ecological functions of these alpine cryptogam layers have largely escaped investigation.  In the summer of 2006 we initiated descriptive surveys of the alpine vascular and cryptogam floras on Snowshoe Mountain (7500’) in Washington State's Northeastern Cascades.  We randomly placed 200 0.25m2 quadrats and recorded percent cover of vascular plants and cryptogams, along with slope and aspect at the plot scale.  Ordination of these cover data with Nonmetric Multidimensional Scaling (NMDS) revealed several distinct cryptogam associations.  Of these, the Flavocetraria cucullata-Cetraria islandica-Thamnolia vermicularis and Lepraria neglecta-Polytrichum piliferum associations accounted for 12.5% and 18.4% of total vegetation cover alone.  Canonical Correspondence Analysis (CCA) was used to explore species-environment relationships using slope and aspect, in this case sine and cosine-converted to “northness” and “eastness.”  Results with these three variables as a second matrix were equivocal; all explained less than 5% of the variance in the species data, though Pearson correlation coefficients for were all significant (p < 0.05).  These descriptive surveys are the backdrop for manipulative work beginning in 2007; reciprocal removals of different cryptogam groups followed by intensive soil moisture, temperature, and plant-available N measurements will highlight the influences of cryptogams on the soil environment and be the first investigation to date of cryptogam effects on plant growth in the alpine.

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