Nitrogen cycling and feedbacks in a global dynamic land model
Stefan Gerber and his colleagues at Princeton Cooperative Institute for
Climate studies published a paper describing Nitrogen (N) cycling and
its feedbacks on terrestrial Carbon (C) in a new GFDL land model
LM3V-N. The new model simulates how nitrogen nutrient availability
affects carbon exchange between land and atmosphere, and improves
constraints on feedbacks among CO2, climate, and land dynamics in the
GFDL Earth System Models.
The new model captures features that are known to be essential from empirical
studies of forest and grassland ecosystems. It captures observed
changes in forest net primary productivity under elevated CO2 as in
free-air CO2 enrichment experiments (FACE). Modeled physical
disturbance (i.e. removal of plant biomass) induces carbon-nitrogen
(C-N) feedbacks expressed as increased soil nitrogen loss followed by
vegetation recovery and nitrogen limitation. This is in line with
theories and observations of successional vegetation dynamics.
Finally, in contrast to other leading models, the model predicts a
weakening of C-N feedbacks when ecosystem steady-state is approached.
The magnitude of the carbon feedback on climate change is one of the
largest uncertainties in making future climate projections. This
addition to the land model allows us to address this large
uncertainty. It offers a more realistic representation of real-world
terrestrial ecosystem dynamics.
Click here to access the manuscript that is in press.