Vegetation-climate models

The investigation of biospheric feedbacks using coupled vegetation-climate models has just started. Therefore, it is too early to arrive at a conclusion, which, in its true sense, always implies some closure. Instead, I try to open this issue further. 

Foley J. A., Levis, S., Costa, M. H Doherty, R., Kutzbach, J. E., and Pollard, D. (in press). Vegetation as an interactive part of global climate models. Ecol. Applications. 

Crowley TJ, Baum SK (1997) Effect of vegetation on an ice-age climate model simulation. J Geophys Res 102 16463-16480... 

Several problems arise concerning current approaches to modeling vegetation response to altered climate. Current models that predict movements of whole biomes in response to climate 52-54) do not allow for different assemblages of species that have occurred under past climates 55) and that will probably occur under future climates 46). Furthermore, these models are... 

Information on the response of taxa to climate and the feedback between vegetation and soil nutrient availability should be synthesized and used to construct computer models operating at the same scale as GCM output 61). Such models should be able to do the following ... 

The main tools used to provide global projections of future climate are general circulation models (GCMs). These are mathematical models based on fundamental physical laws and thus constitute dynamical representations of the climate system. Computational constraints impose a limitation on the resolution that it is possible to realise with such models, and so some unresolved processes are parameterised within the models. This includes many key processes that control climate sensitivity such as clouds, vegetation and oceanic convection [19] of which scientific understanding is still incomplete. 

These values are significantly different from those that have been earlier calculated by RAIN-ASIA model (World Bank, 1994). These differences might be related to the much more detailed and comprehensive national data sets on geological, soil, climate (precipitation, temperature, evapotranspiration, runoff, etc.) and vegetation mapping, physico-chemical properties of soils and geological rocks. This allows the authors to calculate more precise values of all constituents used for maximum sulfur critical load calculation and mapping. 

Crutzen PJ, Carmichael GR. 1993. Modeling the influence of fires on atmospheric chemistry. Fire in the Environment The Ecological, Atmospheric and Climatic Importance of Vegetation Fires. Eds Crutzen PJ, Goldammer JG. John Wiley and Sons, LTD. 89-105. 

Detailed analyses of possible models of evaporation from the land surface that consider the different types of vegetation cover and changes of climatic parameters is given in the works by Bras (1990), Chock and Winkler (2000), and Karley et al. (1993). In particular, there are formulas to calculate evaporation as a function of the height and density of vegetation cover, wind speed, and temperature. For instance, the following dependence is proposed for the rate of complete evaporation ... 

---