The Net Primary Productivity and Water Use of Forests in the Geological Past

Abstract

Publisher Summary There is accumulating evidence that the concentration of atmospheric CO2 in the cretaceous and tertiary was greater, by an order of magnitude, than at present. This chapter discusses model description, which details about leaf gas exchange, canopy gas exchange, respiration, net primary productivity, and vegetation characteristics. Model tests, which details about canopy gas exchange, net primary productivity, and leaf gas exchange have been discussed. Mesozoic–Cenozoic Palaeosimulations, which details about forest productivity in the geological past, and forest water use in the geological past are explored. Cretaceous and Tertiary palaeo–atmospheres are a feature of plant–atmosphere interactions best determined from the stable carbon isotope composition of the fossil leaves themselves, but detailed analyses in this area are currently lacking. A model of terrestrial plant primary productivity is described, sensitive to inputs of temperature, irradiance, the relative humidity of the atmosphere and atmospheric concentrations of CO2 and O2. Despite some oversimplifying assumptions regarding the treatment of LAI and respiration, the resulting predictions of forest function in the geological past appear realistic when compared with a variety of geological and palaeobotanical data. Simulations with the model indicate that the atmospheric CO2 concentrations prevailing in the late Cretaceous and early Tertiary periods, in combination with the shallow equator–to–pole temperature gradients, offered considerable potential for supporting highly productive forests in polar and middle latitude regions.