The Groundwater Regime of Some Meadow Communities in North-West Croatia

Im vorliegenden Beitrag werden Ergebnisse dreijähriger Untersuchungen der Grundwasserverhältnisse unter einigen Wiesengesellschaften in Nordwestkroatien dargestellt, und zwar in Ononido-Arrhenatheretum und Bromo-Cynosuretum cristati aus dem Arrhenatherion-, im Deschampsietum cespitosae aus dem Deschampsion- und in Succisa pratensis-Juncus conglomeratus-Gesellschaft aus dem Molinion-Verband. Die Ergebnisse zeigten grosse Schwankungen der Grundwasseroberfläche in den ersten drei Gesellschaften bei einem verhältnismässig tiefen Grundwasserstand. In der Vegetationsperiode befand sich in der Mehrzahl der untersuchten Bestände die Grundwasseroberfläche im Durchschnitt tiefer als 200 cm unter der Bodenoberfläche. Für den Wasserhaushalt in der Vegetationsperiode spielt im Wurzelraum Grundwasser demnach keine oder wenigstens eine viel kleinere Rolle als Regenwasser und zeitweise auf der Bodenoberfläche stagnierendes Überschwemmungswasser (besonders im Deschampsietum, seltener und kürzer auch im Cynosuretum). In der Succisa pratensis-Juncus conglomeratus-Gesellschaft schwankte die Grundwasseroberfläche viel weniger, und der mittlere Grundwasserstand während der Vegetationsperiode war um etwa 100 cm unter der Bodenoberfläche. Floristische Zusammensetzung und pflanzensoziologische Gliederung der untersuchten Wiesen werden in der pflanzensoziologischen Tabelle und die Grundwasser-Ganglinien in Diagrammen dargestellt.U livadnim zajednicama Ononido-Arrhenatheretum elatioris i Bromo-Cynosuretum cristati iz sveze Arrhenatherion, Deschampsietum cespitosae iz sveze Deschampsion, te u zajednici Succisa pratensis-Juncus conglomeratus iz sveze Molinion izvršena su trogodišnja istraživanja režima podzemne vode u široj okolici Zagreba, u dolini rijeke Krapine u Hrvatskom Zagorju i u dolini rijeke Kupe u široj okolici Karlovca (si. 1). Fitocenološki sastav i raščlanjivanje istraživanih livada prikazani su na fitocenološkoj tabeli (tab. 1). Dubina na kojoj se nalazila razina podzemne vode u profilu tla mjerena je bušenjem »holandskim svrdlom« promjera 8 cm, a kolebanje razine prikazano je na dijagramima (si. 3—12) i tab. 2. Rezultati istraživanja pokazali su da je u istraživanim sastojinama asoc. Arrhenatheretum, Cynosuretum i Deschampsietum kolebanje razine podzemne vode veliko, a u vegetacijskoj sezoni podzemna voda u većini sastojina nalazila se prosječno dublje od 200 cm ispod površine tla, pa se može zaključiti da podzemna voda u području istraživanja gdje je klima humidna (si. 2) nije od bitnog značenja za vodni režim tih zajednica u zoni rizosfere u vrijeme vegetacijske sezone. Znatno manje kolebanje podzemne vode bilo je u zajednici Succisa pratensis-Juncus conglomeratus (si. 10, tab. 2), a u vegetacijskoj sezoni nalazila se podzemna voda u prosjeku na dubini od oko 100 cm, pa se može zaključiti da je veće njezino značenje u području istraživanja za taj tip livada.A three-year investigation into the groundwater regime of the larger area of Zagreb, of the valley of the river Krapina in Hrvatsko Zagorje and the river valley of the Kupa in the larger environs of Karlovac (Fig. 1) involved the meadow communities Ononido-Arrhe- natheretum and Bromo-Cynosuretum cristati from the alliance Arrhe- natherion, Deschampsietum cespitosae (all. Deschampsion) and the community Succisa pratensis-Juncus conglomeratus (all. Molinion) (Tab. 1). The groundwater level in the profile of the soil was measured by boring with a drill 8 cm in diameter, and the oscillations of the level are shown in diagrams and tab. (Figs. 3—12 and Table 2). The results have shown considerable oscillations in the ground- water level of the assoc. Ononido-Arrhenatheretum, Bromo-Cynosuretum and Deschampsietum, and that during the vegetation season the groundwater level was on the average over 200 cm below the surface of the soil in the majoriti of the stands studied. Hence, it can be concluded that the groundwater in the area investigated where the climate is humid (Fig. 2) is not of great importance for the water regime in the rhizosphere zone during the vegetation season in the investigated meadow stands of these communities. Oscillations in the groundwater level were noticeably smaller in the Succisa pratensis-Juncus conglomeratus-community (Fig. 10, Table 2) and during the vegetation period the groundwater surface was on the average at a depth of 100 cm below the surface of the soil; consequently, the groundwater level should be considered of greater significance to this type of meadow vegetation in the area investigated