Syndynamical Relations on the Permanent Plot of Grassland Vegetation in the Area of Middle Posavlje (Croatia)

Im vorliegenden Beitrag werden die Ergebnisse achtjähriger Forschungen auf der Dauerfläche Nr. 8, die schon elf Jahre (1978—1988) existiert, besprochen. Veränderungen der Flora und die Vegetationssukzession auf der Fläche sind Folgen verschiedener anthropo-zoogener Einflüsse. Die Dauerfläche Nr. 8 befindet sich im Gebiet der mittleren Sava-Ebene (Leskovaöa, Försterei Okuöani), und zwar im westlichen Randgebiet des Weidekomplexes der Gesellschaft Trifolio-Agrostietum stoloniferae. Ihre Grösse beträgt 3 ha (es handelt sich eigentlich um drei kontinuierte Flächen von je 1 ha — 8/1, 8/2 und 8/3). Verschiedene anthropo-zoogene Einflüsse (Mahd, Weide, Versumpfung, Schwarzwildwühlen) haben Veränderungen der Flora und eine Vegetationssukzession verursacht. Die Sukzession bewegte sich in mehreren Richtungen und zwar: zur Wiesengesellschaft Bromo-Cynosuretum cristati, zur Ruderalgeseilschaft Polygono-Bidentetum, zur Sumpfgesellschaft Scirpo-Phragmitetum und zum Gebüsch (»sibljak«). Das Gebüsch entwickelt sich weiter in Richtung der Waldgesellschaft Genisto elatae-Quercetum roboris, die in der Nähe der Dauerfläche verbreitet ist. Die floristische Zusammensetzung auf der Dauerfläche (1978—1988), ebenfalls die Sukzessionsflächen, wurden nach Landoll (1977) analysiert.Trajna ploha br. 8 smještena je 1978. godine unutar traynjackog kompleksa na području srednjeg Posavlja — Leskovača (šumarija Okučani). Ima površinu od 3 ha (8/1, 8/2, 8/3) na kojoj su bili predviđeni različiti antropogeni utjecaji na vegetaciju (košnja, ispaša) te prirodna sukcesija. »O stanje« vegetacije (1978) pripadalo je zajednici Trifolio- Agrostietum stoloniferae. Floristički je sastav na trajnoj plohi br. 8 istraživan osam godina (1978, 1979, 1980, 1981, 1983, 1985, 1987 i 1988), tijekom njezina jedana- estgodišnjeg postojanja (1978—1988). Antropo-zoogeni utjecaji (košnja, ispaša, hidromelioracija, rovanje divljih svinja) na pojedinim dijelovima trajne plohe (br. 8) znatno su promijenili biljni pokrov i uzrokovali sukcesiju vegetacije. U proteklom su razdoblju na trajnoj plohi zabilježene 164 vrste (tab. 1). Broj vrsta u pojedinoj fitocenološkoj snimci, te u pojedinim dijelovima plohe znatno varira (tab. 1, 2 i 3.). Dominantni životni oblik na trajnoj plohi br. 8 su hemikryptophyta (H). Taj je životni oblik i inače bitan za vegetaciju umjerenog podneblja. Značajke staništa na temelju ekoloških indeksa po Landoltu (1977), si. 3 i 4, u skladu su sa stvarnim promjenama i zapažanjima na površini plohe i upozoravaju na razlike među zajednicama. Sukcesija na trajnoj plohi br. 8 tipična je za travnjačku vegetaciiu nizinskih, kontinentalnih dijelova Hrvatske, izazvana različitim prirodnim i antropo-zoogenim utjecajima (tab. 3).The permanent plot no. 8 was established in 1978 in the grassland complex in the area of Middle Posavlje — Leskovaca (forester’s office Okučani). Over its area of 3 ha (8/1, 8/2, 8/3) the different anthropogenic influences on the vegetation (mowing, pasture) as well as natural succession were taken into account. The association Trifolio-Agrostietum stoloniferae presented the »O—stage«. Floristical composition on the permanent plot no. 8 were investigated over eight years (1978, 1979, 1980, 1981, 1983, 1985, 1987 and 1988) during its eleven years’ persistence. Anthropogenic and zoogenic influences (mowing, pasture, hydromeliorations, rooting up by wild boars) considerably changed the plant cover of some parts of the permanent plot and caused the vegetation succession. So far, 164 plant species have been noted on the permanent plot. The number of species in a single vegetational record, as well as the number of species on the parts of plot varied considerably (Tab. 1, 2, 3). Hemicryptophytes were prevailing on the permanent plot, coinciding with the general type of life form spectrum for the vegetation of temperate zone. An analysis of ecological indicator values according to Landoll (1977) corresponded with the results of field investigation. The succesion on the permanent plot no. 8 is typical of the grassland vegetation of lowland, continental regions of Croatia, under the influence of different natural, anthropogenic and zoogenic factors (Tab. 3)