S. Slovik, EARLY NEEDLE SENESCENCE AND THINNING OF THE CROWN STRUCTURE OF PICEA-ABIES AS INDUCED BY CHRONIC SO2 POLLUTION .1. MODEL DEDUCTION AND ANALYSIS, Global change biology, 2(5), 1996, pp. 443-458
Regarding time ranges of years, a rationale has been developed which i
s capable of explaining observed 'spruce decline' symptoms observed wh
en spruce is exposed to air containing ambient levels of SO2. It integ
rates and interrelates (i) ecophysiological data (tree morphology, ass
imilate partitioning, canopy turnover, senescence physiology, stomatal
conductance, canopy throughfall, sulphur metabolism, tonoplast sympor
t), (ii) pedological data (soil leaching, cation recycling, litter dec
omposition, forest nutrition), and (iii) meteorological data (site ele
vation, length of the annual trunk growth period, SO2-pollution). Furt
hermore, it can explain field observations at numerous sites of spruce
decline in central Europe where SO2 is implicated as a factor of fore
st decline: (i) thinning of the canopy structure; (ii) early needle se
nescence; (iii) cation deficiency; (iv) low SO2 tolerance at sites wit
h depleted soils in the mountains; (v) synergism of SO2 pollution and
acidic precipitation; (vi) recovery after liming, fertilization and af
ter decreasing SO2 pollution; and (vii) higher SO2 tolerances of decid
uous angiosperms. Different SO2 tolerance strategies are identified th
at are employed by more SO2-tolerant tree species. Ecophysiological SO
2 tolerance factors interact in a complex synergistic or antagonistic
manner. It is concluded that chronic SO2 pollution at ambient concentr
ations predisposes mainly evergreen gymnosperms to suffer under synerg
istic environmental stresses (frost, drought, pathogens, etc.). Thinni
ng of the crown structure is massive at extreme sites, where several s
tresses act simultaneously on the trees (depleted soils, high SO2 poll
ution, acidic rain, etc.). Mathematical formulations allow precise def
initions of terms such as cooperativity, synergism, antagonism, vitali
ty, predisposition, latency, etc. This universal rationale, which is a
pplicable to all tree species, is exemplified here for Norway spruce (
Picea abies [L.] Karst.). Integration of parameters yields an ordinary
differential equation, which can be solved analytically. It predicts
reversible dynamics of crown structures and gives an ecophysiological
background to 'damage'.