VEGETATION ZONATION IN A FORMER TIDAL AREA - A VEGETATION-TYPE RESPONSE MODEL-BASED ON DCA AND LOGISTIC-REGRESSION USING GIS

We studied the effect of flooding frequency on the vegetation of the n orthern part of the Delta region in the southwestern Netherlands under different grazing and soil conditions using Detrended Correspondence Analysis. We found grazing and frequency of flooding to be the most im portant environmental factors that determine zonation of vegetation ty pes in the area. We used logistic regression to describe the probabili ty of occurrence of 25 vegetation types in relation to the frequency o f flooding under grazed and ungazed conditions. We implemented the veg etation response model in a Geographical Information System so as to c alculate new vegetation maps of outer dike areas under different flood ing regimes. The model will be used for evaluation of the effects of d ifferent sluice management schemes on outer dike plant zonation in the research area.