Abstract Detail

Bryological and Lichenological Section/ABLS

RICE , STEVEN K [1], PILKINGTON, KYLE [2], ROBINSON, SEAN C [3].

Productivity and δ¹³C in Sphagnum mosses across climatic and nitrogen deposition gradients.

Sphagnum mosses are important producers in peatland systems, yet we understand little about the mechanisms that underlie differences in their productivity.  We measured growth and productivity of two hummock-forming peatland dominants, Sphagnum magellanicum and S. fuscum at three sites each in northern New York and in Maine that differ in both climate and nitrogen deposition.  Vertical growth, productivity, colony traits, plot characteristics and δ¹³C of plant tissue were measured in plots (mostly n=4) for each species per site.  Plots were situated in low to high hummocks and were established for the 2013 growing season.  Vertical growth was measured using brush wires (3 per plot) and productivity was estimated using the bulk density of the top 3 cm of plants below the capitulum in 10 cm diameter cores.  End of season δ¹³C values of mature branch tissue below the capitulum were also obtained.  Productivity ranged from 83.8 to 453.9 g m^-2 yr^-1.  ANOVA results indicated that S. fuscum had higher productivity than S. magellanicum (228 versus 153 g m^-2 yr^-1).  Although there was no difference between the two regions, sites within regions differed significantly.  Consequently, regional environmental differences in climate and N deposition were not as important as within region effects, which likely associate more with site-specific habitat differences than with climatic variation within the region.  The δ¹³C ANOVA test showed significant main effects of species and regions with S. fuscum (-28.5‰) having a less negative δ¹³C value than S. magellanicum (-29.6‰).  Regression analyses within each species revealed a negative relationship between vascular plant cover and δ¹³C for S. fuscum (R²=0.37; p<0.01), but not S. magellanicum, where δ¹³C had a negative relationship with water table depth (R²=0.36; p<0.01).  This pattern was also present for S. fuscum, but only at water table depths below 70 cm.  Neither species had a significant relationship between δ¹³C and any measure of growth or productivity.  Consequently, environmental factors like shading by vascular plants and water availability influence dynamics of short-term carbon uptake and result in differences in the seasonally integrated δ¹³C signal.  However, differences in productivity do not associate with variation in these same factors.  Instead, productivity may vary with differences in respiratory demands associated with nutrient acquisition, growth or with environmental stressors like drought or excess light.

1 - UNION COLLEGE, DEPT OF BIOLOGY, SCHENECTADY, NY, 12308, USA
2 - Union College, Dept of Biology, Schenectady, NY, 12308, USA
3 - SUNY Oneonta, Dept of Biology, Oneonta, NY, 13020, USA

Keywords:
carbon isotope discrimination
Sphagnum
productivity.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PBR006
Abstract ID:739
Candidate for Awards:None