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.
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 | 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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