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The effect of drought on mycorrhizal production and very fine root system development of Norway spruce under natural and experimental conditions

Abstract:

Mycorrhizal growth rates were measured monthly, using a new method, in two neighouring plots of a natural spruce stand. One of the plots was irrigated while the other suffered from drought during the late summer and autumn months. Drought did not completely stop mycorrhizal growth. It caused a higher rate of root dormancy and a reduced elongation rate of the parent roots but an increased development of new mucorrhizal last order laterals. Thus, the branching density of the very fine root system was increased, even though fewer growing mycorrhizae were found in the non-irrigated plot during the dry period. Similar results were observed in a water-stress experiment with pot-cultures. After rewetting, elongation rate was stimulated and the number of growing mycorrhizae increased rapidly on the non-irrigated plot. Possible relationships between dry weight, distribution and branching density of growing fine root systems are presented. © 1988 Kluwer Academic Publishers.