Landscapes as patches of plant functional types: An integrating concept for climate and ecosystem models

Abstract

While most land models developed for use with climate models represent vegetation as discrete biomes, this is, at least for mixed life‐form biomes, inconsistent with the leaf‐level and whole‐plant physiological parameterizations needed to couple these biogeophysical models with biogeochemical and ecosystem dynamics models. In this paper, we present simulations with the National Center for Atmospheric Research land surface model (NCAR LSM) that examined the effect of representing vegetation as patches of plant functional types (PFTs) that coexist within a model grid cell. This approach is consistent with ecological theory and models and allows for unified treatment of vegetation in climate and ecosystem models. In the standard NCAR LSM the PFT composition and leaf area for each grid cell are obtained by classifying grid cells as 1 of 28 possible biomes. Here, we develop a data set from 1‐km satellite data that provides each model grid cell a unique PFT composition and leaf area for each PFT. Global simulations at 3° × 3° spatial resolution showed that ground temperature, ground evaporation, and northern high‐latitude winter albedo exhibited direct responses to these landscape changes, which led to indirect effects such as in soil moisture and sensible and latent heat fluxes. Additional simulations at 2° × 2° and 1° × 1° spatial resolution showed that low‐resolution simulations masked landscape heterogeneity in both approaches but the satellite‐based, continuous representation of vegetation reduced model sensitivity to resolution. It is argued that the use of spatially continuous distributions of coexisting PFTs is a necessary step to link climate and ecosystem models.

An Urban Parameterization for a Global Climate Model. Part II: Sensitivity to Input Parameters and the Simulated Urban Heat Island in Offline Simulations

“…To investigate the model's ability to reproduce this relationship, the model was run for a single North American site for 1 yr at height-to-width ratios from 0.5 to 3.0 [uncoupled from an atmospheric model and forced by observations of atmospheric variables as in Bonan et al (2002)]. In the absence of observed U.S. city characteristics to model this relationship, some assumptions were made.…”

“…Urban ecosystems can significantly alter the radiative, thermal, moisture, and aerodynamic characteristics of the land surface (Landsberg 1981;Oke 1987;Bonan 2002;Arnfield 2003). As a consequence of these changes, urban climates can differ significantly from surrounding natural ecosystems, often resulting in urban heat islands (e.g., Landsberg 1981).…”

Impact of vegetation feedback on the temperature and its diurnal range over the Northern Hemisphere during summer in a 2 × CO2 climate

“…Detailed information on the model is documented in Collins et al (2004; and will not be repeated here. Land-surface processes in CAM3 are calculated by the Community Land Model version 3 (CLM3; Oleson et al 2004) that calculates the heat, moisture, and momentum fluxes between land surfaces and atmosphere as well as the thermal and hydrologic processes at the surface and the interior of near-surface soil layer (Bonan et al 2002;Oleson et al 2004;Dickinson et al 2006). A comprehensive discussion on CLM and the surface flux calculations have been provided in Oleson et al (2004).…”

“…These seven primary PFTs are further refined to tropical, temperate, and boreal deciduous or evergreen trees, C3 and C4 grasses, and evergreen and deciduous shrubs by bioclimatic rules . In each PFT, leaf phenology in the CLM3 is prescribed, and the seasonal course of leaf area index (LAI) for each PFT is derived through interpolating the monthly PFT-specific LAI from National Oceanic and Atmospheric Administration (NOAA)-Advanced Very High-Resolution Radiometer (AVHRR) data as described by Bonan et al (2002).…”

Comparison of satellite‐derived TOA shortwave clear‐sky fluxes to estimates from GCM simulations constrained by satellite observations of land surface characteristics

“…The default version of CCSM3 utilises the CLM3 where land surface characteristics are specified using the standard NCAR land surface parameters as described in Oleson et al (2004). The description of physical processes and the land surface boundary data are evaluated through climate simulations with the CLM and the CCSM in Bonan et al (2002) and Dickinson et al (2006). The improved physical processes of CLM3 and the representation of land surface boundary conditions had overall helped to improve CCSM3.…”