K. Kramer et Gmj. Mohren, SENSITIVITY OF FORGRO TO CLIMATIC-CHANGE SCENARIOS - A CASE-STUDY ON BETULA-PUBESCENS, FAGUS-SYLVATICA AND QUERCUS-ROBUR IN THE NETHERLANDS, Climatic change, 34(2), 1996, pp. 231-237
The impacts of the climate change predictions of four general circulat
ion models (GFDL, GISS, OSU and UKMO) on net primary production (NPP)
of Betula pubescens, Fagus sylvatica and Quercus robur in The Netherla
nds were analysed using the process-based model FORGRO. FORGRO is a mo
del suitable to simulate growth of managed mono-species stands. For th
e GCMs mentioned, both transient and equilibrium 2 x CO2 scenarios of
temperature and precipitation change were evaluated and compared with
responses under current climate. It was found that the NPP increases i
n the transient scenarios, but remains the same or declines in the 2 x
CO2 scenarios. This is because respiration increases more with rising
temperature than photosynthesis. During the transient scenarios this
effect gradually increases, while in the 2 x CO2 scenario this effect
is operating over the entire simulation period. If water limitation is
taken into account, then the NPP of the reference scenario is reduced
. In both the transient and 2 x CO2 scenarios this water limitation is
annulated, resulting in a stronger response of NPP compared to the si
tuation without water limitation. This enhancement of the response is
most pronounced in the transient scenario due to the gradual effect of
temperature on respiration. Similar results were obtained with a vers
ion of FORGRO in which the photosynthesis module of HYBRID (PGEN) is i
ncorporated, although the response in FORGRO-PGEN is usually higher th
an that of FORGRO. This is because the response of photosynthesis to C
O2 rises with increasing temperature as defined in the PGEN-model, but
not according to FORGRO.