OOS 29-1 - Beyond Jenny’s state factors: Do biotic interactions determine nitrogen fixation and emergent ecosystem properties?

Wednesday, August 9, 2017: 1:30 PM
Portland Blrm 257, Oregon Convention Center
Lars O. Hedin, Ecology and Evolutionary Biology, Princeton University, Princeton, NJ and Mingzhen Lu, Ecology and Evolutionary Biology, Princeton Univiersity, Princeton, NJ

There is much evidence that external state factors influence ecosystem properties, including nitrogen fixation. But, I will here ask whether such a state-factor view may fail to offer the “whole story” of symbiotic nitrogen fixation, and how this process varies across biomes, time, and as a function of increasing atmospheric CO2. I will first review a few fundamental patterns of how nitrogen fixing plants and fixation vary across the land biosphere, and examine how these patterns compare against the traditional state-factor view. I will then use a new adaptive dynamics model that focuses on a very different class of ecosystem dynamics: the local-scale competitive interactions between plants, and the feedbacks that emerge from these interactions at the ecosystem scale.


I will offer evidence that local biotic interactions may be essential for understanding the distribution, the functional properties, and the emergent consequences of symbiotic nitrogen fixers within ecosystems. I will show that a world without these local interactions would both look and function very differently than today’s world. Finally, I will speculate about the interaction between atmospheric CO2 levels and the emergent ecosystem dynamics imposed by nitrogen fixation, with particular emphasis on the biome-specific distribution of nutrient cycles and net primary production.