An integrated biosphere model of land surface processes, terrestrial carbon balance, and vegetation dynamics

TLDR

The authors develop the Integrated Biosphere Simulator (IBIS), a physically consistent model that unifies land surface biophysics, carbon fluxes, and vegetation dynamics for use in atmospheric modeling. IBIS employs a hierarchical, modular architecture with a common state description, performing hourly coupled simulations of surface water, energy, and carbon fluxes, integrating them annually to update leaf area index and biomass for nine plant functional types that compete for light and water. The model reproduces observed annual evapotranspiration, runoff, and net primary productivity, and its simulated vegetation dynamics qualitatively match secondary succession patterns and align well with potential natural vegetation maps.

Abstract

Here we present a new terrestrial biosphere model (the Integrated Biosphere Simulator ‐ IBIS) which demonstrates how land surface biophysics, terrestrial carbon fluxes, and global vegetation dynamics can be represented in a single, physically consistent modeling framework. In order to integrate a wide range of biophysical, physiological, and ecological processes, the model is designed around a hierarchical, modular structure and uses a common state description throughout. First, a coupled simulation of the surface water, energy, and carbon fluxes is performed on hourly timesteps and is integrated over the year to estimate the annual water and carbon balance. Next, the annual carbon balance is used to predict changes in the leaf area index and biomass for each of nine plant functional types, which compete for light and water using different ecological strategies. The resulting patterns of annual evapotranspiration, runoff, and net primary productivity are in good agreement with observations. In addition, the model simulates patterns of vegetation dynamics that qualitatively agree with features of the natural process of secondary succession. Comparison of the model's inferred near‐equilibrium vegetation categories with a potential natural vegetation map shows a fair degree of agreement. This integrated modeling framework provides a means of simulating both rapid biophysical processes and long‐term ecosystem dynamics that can be directly incorporated within atmospheric models.