Monday, September 17, 2012

Weekly Tuesday Smithsonian Seminar Sept 18

Tuesday seminar September 18, 2012 at the Earl S. Tupper Conference Center, Ancon, Panama site of the old Tivoli Guest House.  Announcing the STRI Tuesday afternoon seminar for September 18, 2012 at 4:00 pm in the Earl S. Tupper auditorium:  
Speaker: Jordan Mayor, STRI and NSF International Postdoctoral Fellow
Title:  Using natural abundance stable isotope ratios to understand ecosystem nitrogen cycling in boreal and tropical forests

Abstract:  Plant and ecosystem ecologists are increasingly interested in using stable isotopes as nondestructive tracers that integrate how plants today and in the past have interacted with and responded to their abiotic and biotic environments. Nitrogen isotopes are informative because biological and physical processes alter the ratio of heavy to light nitrogen isotopes (15N:14N) and these effects can be traced along the soil-fungal-plant continuum. A major limitation to many studies using these metrics has been the inability to differentiate underlying causes of 15N variability. My approach has overcome this limitation through the detailed isotopic analysis of individual forms of soil N.

Studying the nitrogen cycle is particularly important as humans have doubled the amount of N in the biosphere and it is limiting net primary productivity and associated carbon balance in many ecosystems. The main themes in ecosystem 15N research will be presented and addressed in four case-studies the author has worked in. These will include highlights from: 1) an Alaskan black spruce forest reliant on ectomycorrhizal fungi for their N sources, 2) a global meta-analysis of fungal isotope patterns to elucidate trophic dynamics, 3) the patterns and processes following 13 years of N and phosphorus treatments in the Gigante Fertilization Experiment, and 4) an isotopic labeling experiment conducted in montane rainforests in western Panama.

Upcoming seminars:  

September 25:  Taegan McMahon, STRI and USF
Disease and amphibian declines:  alternative hosts and possible solutions

October 2:  Egbert Leigh, STRI
The intellectual history of STRI

October 9:  Dave Marvin, University of Michigan
Is elevated CO2 a cause of increasing tropical lianas?

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