A method for scaling vegetation dynamics: The ecosystem demography model (ED)
Authored by PR Moorcroft, GC Hurtt, SW Pacala
Date Published: 2001
DOI: 10.1890/0012-9615(2001)071[0557:amfsvd]2.0.co;2
Sponsors:
United States National Oceanic and Atmospheric Administration (NOAA)
United States National Science Foundation (NSF)
Platforms:
No platforms listed
Model Documentation:
Other Narrative
Mathematical description
Model Code URLs:
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Abstract
The problem of scale has been a critical impediment to incorporating
important fine-scale processes into global ecosystem models. Our
knowledge of fine-scale physiological and ecological processes comes
from a variety of measurements, ranging from forest plot inventories to
remote sensing, made at spatial resolutions considerably smaller than
the large scale at which global ecosystem models are defined. In this
paper, we describe a new individual-based, terrestrial biosphere model, which we label the ecosystem demography model (ED). We then introduce a
general method for scaling stochastic individual-based models of
ecosystem dynamics (gap models) such as ED to large scales. The method
accounts for the fine-scale spatial heterogeneity within an ecosystem
caused by stochastic disturbance events, operating at scales down to
individual canopy-tree-sized gaps. By conditioning appropriately on the
occurrence of these events, we derive a size-and agc-structured (SAS)
approximation for the first moment of the stochastic ecosystem model.
With this approximation, it is possible to, make predictions about the
large scales of interest from a description of the fine-scale
physiological and population-dynamic processes without simulating the
fate of every plant individually. We use the SAS approximation to
implement our individual-based biosphere model over South America from
15 degrees N to 15 degrees S, showing that the SAS equations are
accurate across a range of environmental conditions and resulting
ecosystem types. We then compare the predictions of the biosphere model
to regional data and to intensive data at specific sites. Analysis of
the model at these sites illustrates the importance of fine-scale
heterogeneity in governing large-scale ecosystem function, showing how
population and community-level processes influence ecosystem composition
and structure, patterns of aboveground carbon accumulation, and net
ecosystem production.
Tags
Plant-communities
Ecological consequences
Nutrient dynamics
Stomatal conductance
Recruitment limitation
Terrestrial biosphere model
Forest
succession
General-circulation models
Co2-induced
climate change
Tree populations