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| Matzner, E; Murach, D: Soil changes induced by air pollutant deposition and their implication for forests in Central Europe, Water, Air and Soil Pollution, 85, 63-76 (1995) | |
Abstract:
A survey of leaf and needle losses of European forests in 1993 revealed that 23% of the total forested area
had defoliation of more than 25%. The focus of this defoliation is in Central Europe, namely in Poland, Slowakia,
Czech Republic, and Germany. The annual surveys of leaf losses and discoloration indicated only small changes
during the last years for the coniferous forests in Germany. However, the increasing leaf losses of oak and beech
during the last years were alarming.
Evaluating the potential relation between air pollutant deposition, soil changes and forest damage, we focus here
on the recent changes in deposition and soil conditions, and their implication on tree root development and drought
susceptability of trees.
While deposition of SO42, tC and Ca 2+ in many Central European forests decreased in the last decade, input of
NH4 + and NO 3" remained high or even increased. The H + load of many forest soils today is thus still high compared
to weathering rates, but the proportion of the H + load resulting from turnover of deposited N has increased. Recent
effects of changing depositions on acid forest soils were: depletion of soil M-pools, release of formerly stored soil
SO ?, accumulation of N in soil organic matter, increasing N availability to trees and decreasing concentration of
Ca ~+ in the soil solution.
We hypothesise that soil acidification and increased N availability will decrease the free root biomass of trees
and shift the rooting zone to upper soil layers. Increased above ground growth, observed in many areas of Europe,
will furthermore decrease the root/shoot ratio. This development will finally cause increased drought suseeptability
of trees and is thus of destabilizing nature. The proposed chain of events might be overlapped by other effects of air
pollutants on forest ecosystems, namely direct effects of gases on leaves, nutritional inbalances, and interactions with
pests.
Key words: Forest damage, soil acidity, N-saturation, acid deposition, root growth, drought |
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