MODELING COMPARISON TO EVALUATE THE IMPORTANCE OF PHENOLOGY AND SPRING FROST DAMAGE FOR THE EFFECTS OF CLIMATE-CHANGE ON GROWTH OF MIXED TEMPERATE-ZONE DECIDUOUS FORESTS
K. Kramer et al., MODELING COMPARISON TO EVALUATE THE IMPORTANCE OF PHENOLOGY AND SPRING FROST DAMAGE FOR THE EFFECTS OF CLIMATE-CHANGE ON GROWTH OF MIXED TEMPERATE-ZONE DECIDUOUS FORESTS, Climate research, 7(1), 1996, pp. 31-41
The importance of 3 phenological types of deciduous tree, and the effe
cts of the occurrence of frost damage on growth of mixed-species fores
ts, were evaluated using the models FORGRO and HYBRID, The climate cha
nge scenarios used were a doubling of the CO2 concentration (700 mu mo
l mol(-1)) and an increase in temperature ranging from 0 to 7 degrees
C. Both FORGRO and HYBRID are mechanistic models treating eco-physiolo
gical processes in detail. FORGRO highlights potential growth in manag
ed forests where all individuals of one species are of the same age an
d size, whereas HYBRID highlights growth in natural forests, including
regeneration and mortality of individual trees that differ in age and
size. Furthermore, the importance of inaccurate prediction of phenolo
gical events and frost hardiness for growth in mixed-species stands wa
s evaluated by comparing dynamic models to regression models. The dyna
mic models predict the timing of phenological events annually and the
progression of frost hardiness during dormancy, whereas the regression
models represent empirical relationships between the change in the av
erage date of phenological events with a rise in mean winter temperatu
re and the level of frost hardiness at the moment of leaf unfolding. T
he results of the climate change scenarios indicate for both FORGRO an
d HYBRID that: (1) the differences in net primary production (NPP) of
the 3 phenological types considered are enhanced when grown in a mixed
-species stand compared to a monospecies stand; and (2) the effects of
frost damage on growth are more prominent in mixed-species stands tha
n in monospecies stands. Regarding the accuracy of the dynamic approac
h compared to the regression approach for predicting the timing of lea
f unfolding and spring frost damage, the dynamic approach for leaf unf
olding results in a similar response of NPP to the regression approach
, both for the monospecies and the mixed-species situation. The dynami
c approach, however, yields larger differences in the NPP between the
phenological types because the model predicts a greater advancement of
leaf unfolding than does the regression approach. Comparing the regre
ssion approach to the dynamic approach with regard to frost hardiness,
the regression approach shows a greater frequency of frost damage; be
cause, according to the dynamic approach the minimum level of frost ha
rdiness is attained after the date of leaf unfolding, thus reducing th
is frequency.