Quantifying the biologically possible range of steadystate soil and surface climates with climate model simulations

Authors:

Axel Kleidon

Abstract:

The terrestrial biosphere shapes the exchange fluxes of energy and mass at the land surface. The wide variety and diversity of plant form and functioning can potentially result in a wide variety of possible climatic conditions at the land surface and in the soil, which in turn feed back to more or less suitable conditions for terrestrial productivity. Here, I use sensitivity simulations to vegetation form and functioning with a global climate model to quantify this range of possible range of steady-states (“PROSS”) of the surface energy- and mass balances. The surface energy- and water balances over land are associated with substantial sensitivity to vegetation parameters, with precipitation varying by more than a factor of 2, and evapotranspiration by a factor of 5. This range in biologically possible climatic conditions results in drastically different values of vegetation productivity. Optimum conditions for maximum productivity are close to the simulated climate of present-day conditions. From these results we can conclude that a wide range of physical soil-surface conditions are biologically possible and that the actual state of the present-day is shaped strongly by the emergent characteristics and functioning of the terrestrial biosphere.

Reference:

  • Biologia (Bratislava), 61/Suppl. 19: S234-S239.
  • Weblink to publisher's web page.
  • Postprint of this manuscript (accepted version of the paper formatted by author).
  • BibTex entry.

Figure 1: Possible range of global mean land surface temperature and soil wetness within the rooting zone and the associated value of vegetation productivity. Each symbol represents the values of one sensitivity simulation.

Figure 2: Possible range of steady states of the global mean terrestrial carbon balance, in terms of the average amounts of carbon stored in vegetation biomass and the soil. The ”Desert World” simulation (black star) is, by definition, located at carbon pool sizes of zero kg C/m2.

Figure 3: Possible range of steady states of the terrestrial energy balance, in terms of annual means of net emission of longwave radiation and turbulent fluxes (sum of the sensible and latent heat fluxes).

Figure 4: Possible range of steady states of the terrestrial water balance, in terms of the annual means of precipitation and evapotranspiration. Also shown for comparison is the 1:1 line and a linear best fit line.

Figure 5: Conceptual diagram to illustrate how optimized vegetation responds to (top) perturbation and (bottom) climatic change.