Recent succession of the pedunculate oak and narrow-leaved ash forest in the unflooded part of Gornji Srem

In the unflooded part of the river Sava, Bosut and Studva bottom lands in Gornji Srem (forest sections Moroviæ and Višnjiæevo), the following succession series are clearly differentiated on large areas: forests of narrow-leaved ash (Fraxinetum angustifoliae Jov. et Tom.1979. s.l) on ((/(-(/(-gley ( forests of pedunculate oak and narrow-leaved ash (Fraxino-Quercetum roboris Jov. et Tom.1979. s.l) on humogley, humosemigley and semigley ( forests of pedunculate oak, hornbeam and ash (Carpino-Fraxino-Quercetum roboris Jov. et Tom. 1979, s.l) on semigley, brown forest soil and soil lessive Forest of pedunculate oak and narrow-leaved ash, which is an intermediary stage of the ecological succession series, is also differentiated into three ecological units (subassociations), which are the developmental phases of the association - primary, optimal and terminal – Forest of pedunculate oak and ash with hygrophilic accessories (Fraxino-Quercetum roboris hygrophyllum) on moderately moist hydromorphic black soils (humogley, ecological (-gley) is the primary phase, ecologically and syn-dynamically related to the terminal phase of the previous stage – forest of narrow-leaved ash with sedge (Fraxinetum angustifoliae caricetosum remotae) on (/(-gley. The dominant edificator is narrow-leaved ash, while pedunculate oak is in the subdominant position Moister meadow black soils are characterised by intensive moisture, because already at the depth of 20/30-50 cm, the process of gleying occurs. Underground water stagnates at the depth of 80-120 cm – Typical forest of pedunculate oak and ash (Fraxino-Quercetum roboris typicum) on the drier varieties of humosemigley is the optimal phase in the development of the association, with a slowed down dynamism. Both edificators are in their ecological and coenological optima, i.e. the conditions of their development are excellent In the drier hygromorphic black soils the level of underground water is about 40 cm lower than the moister variety, so that the stagnating underground water occurs at the depth of 120-160 cm. However, thanks to capillary rise, the tree root system has abundant moisture. Simultaneously, the physical properties of the soil are more favourable, so the ecological productivity potential is very high – Forest of pedunculate oak and ash with field maple and Tartar maple (Fraxino-Quercetum roboris aceretosom) on semigleys is the terminal phase, syn-dynamically and spatially related to the following phase – forest of pedunculate oak, hornbeam and ash with sedge (Carpino-Fraxino-Quercetum roboris caricetosum remotae) on semigleys to semigleys lessive in the unflooded zone. Pedunculate oak undertakes the role of the dominant edificator, while ash is retreating The depth of the stagnating ground water is 150/160-200 cm and the soils are significantly lighter, so that capillary rise is twice as difficult. This is not unfavourable to pedunculate oak, which reaches its ecological optimum even in the less moist communities with hornbeam in the terrestrial conditions, but it hinders the development of the more hygrophilic narrow-leaved ash and thus accelerates the syn-dynamic processes of the transition to the following, drier stage The study of the dynamism of pedunculate oak and narrow-leaved ash forests, one of the most widely distributed and most productive ecosystems in Gornji Srem, should direct, advance and facilitate the carrying out of all operations on its enhancement.