DOI number:10.5194/bg-11-5987-2014
Abstract:Persistent divergences among the predictions of complex carbon-cycle modelsinclude differences in the sign as well as the magnitude of the response ofglobal terrestrial primary production to climate change. Such problems withcurrent models indicate an urgent need to reassess the principles underlyingthe environmental controls of primary production. The global patterns ofannual and maximum monthly terrestrial gross primary production (GPP) byC3 plants are explored here using a simple first-principles model basedon the light-use efficiency formalism and the Farquhar model for C3photosynthesis. The model is driven by incident photosynthetically activeradiation (PAR) and remotely sensed green-vegetation cover, with additionalconstraints imposed by low-temperature inhibition and CO2 limitation.The ratio of leaf-internal to ambient CO2 concentration in the modelresponds to growing-season mean temperature, atmospheric dryness (indexed bythe cumulative water deficit, Δ E ) and elevation, based on an optimalitytheory. The greatest annual GPP is predicted for tropical moist forests, butthe maximum (summer) monthly GPP can be as high, or higher, in boreal ortemperate forests. These findings are supported by a new analysis of CO2flux measurements. The explanation is simply based on the seasonal andlatitudinal distribution of PAR combined with the physiology ofphotosynthesis. By successively imposing biophysical constraints, it is shownthat partial vegetation cover – driven primarily by water shortage –represents the largest constraint on global GPP.
Discipline:Natural Science
First-Level Discipline:Ecology
Translation or Not:no
Included Journals:SCI