Duncan Menge

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Research

Much of my research aims to figure out when, where, and especially why nutrients such as nitrogen (N) and phosphorus (P) control plant growth and other ecosystem processes.

Although we know a lot about nature, there is still a lot we do not know, particularly in complex systems with many interconnecting parts (like ecosystems).

Ecosystem paradoxes:
Often our intuition for how the real world "should" work is at odds with, well, the real world. For example, nitrogen fixing plants (plants like beans, peas, alders, and a bunch of others that can access atmospheric N2 gas by forming symbioses with bacteria) "should" outcompete non-fixing plants when N controls plant growth and vice versa, which would produce ecosystems with a Goldilocks-style "just right" amount of nitrogen.  Although lakes seem to work this way, unpolluted forests do not.
  • Temperate forests are N-poor, yet with the exception of very young forests, they have no N fixing trees.  Why are N fixing trees absent?
  • Tropical forests are N-rich, and contain many potentially N fixing trees.  Is the N coming from N fixation?  If so, why?  If not, why are N fixers so common?
I use a variety of methods to address these questions, from mathematical models to field observations and experiments to data synthesis and analysis to laboratory analysis.
Why is this relevant?
  • Climate change: Plant growth happens via photosynthesis, which is the main way carbon dioxide (CO2) is removed from the atmosphere.  Atmospheric CO2 is the leading cause of climate change, so understanding what controls CO2 removal from the atmosphere is critical to solving the climate problem.  For more on climate change, the IPCC website and Climate Central are great places to learn about current climate science and more.
  • Other environmental problems: When nutrients do not control plant growth, they are more likely to accumulate in soils, leak out into waterways, or go into the atmosphere.  This can cause 
    • soil and water acidification, which can harm animals and plants directly,
    • algal blooms, which can harm animals by causing dangerously low oxygen levels in water,
    • direct warming, since various forms of N are also greenhouse gases
  • Economic issues: We spend a lot of money and energy on nutrients (fertilizers).  The more we know about nutrient cycling, the better we can tune fertilization levels, which improves cost efficiency.
For a summary of these and related topics, see the Millennium Ecosystem Assessment.

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