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Abstract:
We describe an implementation of the Ecosystem Demography (ED) concept
in the Community Land Model. The structure of CLM(ED) and the
physiological and structural modifications applied to the CLM are
presented. A major motivation of this development is to allow the
prediction of biome boundaries directly from plant physiological traits
via their competitive interactions. Here we investigate the performance
of the model for an example biome boundary in eastern North America. We
explore the sensitivity of the predicted biome boundaries and ecosystem
properties to the variation of leaf properties using the parameter space
defined by the GLOPNET global leaf trait database. Furthermore, we
investigate the impact of four sequential alterations to the structural
assumptions in the model governing the relative carbon economy of
deciduous and evergreen plants. The default assumption is that the costs
and benefits of deciduous vs. evergreen leaf strategies, in terms of
carbon assimilation and expenditure, can reproduce the geographical
structure of biome boundaries and ecosystem functioning. We find some
support for this assumption, but only under particular combinations of
model traits and structural assumptions. Many questions remain regarding
the preferred methods for deployment of plant trait information in land
surface models. In some cases, plant traits might best be closely linked
to each other, but we also find support for direct linkages to
environmental conditions. We advocate intensified study of the costs and
benefits of plant life history strategies in different environments and
the increased use of parametric and structural ensembles in the
development and analysis of complex vegetation models.
