engleski

The groundwater regime - a decisive factor of pedunculate oak stability

This poster encompasses research undertaken in the framework of the "Permanent monitoring of ground and surface water in the lowland forest ecosystem" project. Monitoring was carried out in the Varoški lug forest at seven piezometric stations during the period 1988-1998. The aim of the research was to determine the correlation between the groundwater level and the forest decline on specific soil types. Soil types that predominate in the Varoški lug area are hydromorphic soils of the pseudogley and eugley types (hypogley, epigley and amphigley). During this period, extensive oak decline occurred, in particular during 1990, 1991 and 1993. The dominant cause of this decline was a lowering of the groundwater level. The ground water regime in the vegetation period was separated so that for each month, the median values were calculated. The relative values of the median of specific month were then correlated with the relative values of wood volume of the declined trees in twenty three compartments with the use of the Spearman rank order correlation method. A fairly good correlation was found (0.6-0.8) between the drop of groundwater and oak decline on the pseudogley type of soil in July, August, September and October. This clearly suggests that a prolonged dry phase of soil has a negative effect on oak stands. A significant fact is that a correlation exists (above 0.6) in April and May, at the outset of the vegetation period. This can be used as an early indicator of the intensity of decline in current year.

oak decline; groundwater; piezometers; pseudogley

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