broj: 7-8/2001
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| IZVORNI ZNANSTVENI ČLANCI | ||
| Vučetić, M. | UDK 630* 111+431 | |
| Weather Conditions and Forest Fires on the Coastal Area of Croatia During 2000 pdf HR EN | 367 | |
| PREGLEDNI ČLANCI | ||
| Prpić, B. | UDK 630* 263 + 116 | |
| The Effects of Hydro-technical Interventions on the Stabilitv of Pedunculate Oak (Quercm robur L.) Stands in Croatia on the Example of the Novo Virje Hydro-power Station pdf HR EN | 379 | |
| Summary: The river valleys of Croatia are home to about 200,000 ha of lowland forests with a larger or smaller proportion of pedunculate oak. in dif-ferent humid sites of water valleys, pedunculate oak forma forest ecosystems in association with other plant species and the animal community. While these ecosystems differ in the composition of plant species, with a multitude of hvgrophytes, their common feature is a considerable participation of pedunculate oak in the tree layer.The direct ecological factor contributing to the growth of pedunculate oak is water which, whether below the minimum or above the maximum, leads to physiological weakening, and frequently to dying of the oak. In the sites of presently stable pedunculate oak middle-aged and older stands, water rela-tions are considered to be optimal. Among the tree species oflowlandforests, pedunculate oak is one of the most sensitive. Currently, about 30 % of pedunculate oak trees are endangered in Croatia, and they will desiccate before reaching their economic maturity. Pedunculate oak is capable of surviving climatic excesses, drought and very humid years. However, hydro-technical interventions in the forested area of the valleys resulting in abrupt changes, cause its decline in all forest ecosystems. CONCLUSIONS 1. Hydro-technical interventions in the woody areas of lowland forests cause changes in water relations in different sites of forest ecological svstems. These changes lead to a disturbed biological balance in forests and the dieback of pedunculate oak and other tree species. The experience of the forestry profession and science is a sum total of the awareness of unfavourable effects of hydro-technical and technical interventions under-taken since the beginning of the 20th century up to the present day. Lowland forests represent particularly rich and complex ecological svstems with high biological diversity of plant and animal species. The supply of forest trees with water, the dominant ecological factor of forest communities, is especially complex. This factor depends both on the phvsiological potential of the trees and river dynamics. What is particu-larly important are the different ways in which the pedunculate oak root systems are supplied with water in varying hydropedological soil units and in their transitions. The supply depends on the level of groundwater and its capillary movement in the ecological soil profile, which is different for almost any tree. It can be assumed with a high degree of certainty that almost every tree, and at leastgroups of trees, in the lowland forests of Podravina around Koprivnica and Đurđevac have their own way of supply with water, which is mainly in the form of groundwater. In order to maintain lowland forests, it is necessary to maintain the present state of water relations. 2. The 1990 Forest Act of the Repuhlic of Croatia and a 1997 by-law estima-ted the biological capital of the Koprivnica-Đurđevac lowland forests, comprising both the generally beneficial Functions and the raw material and energetic function, at 1,822,613,682 DM. This amount exceeds the total investment of 987,000,000 DM into the hydropower station Novo Virje. The annual increment of these forests amounts to 90,783 m3 which is 5,921,000 DM in market value. This amount does not comprise the valne of subsidiary forest products (hunting, forest fruit, mushrooms, medicinal herbs and others), as well as the valne of beneficial forest functions (carbon dioxide absorption, water and air cleansing, the influence of forests on the climate, maintenance of biodiversity, conservation of the genofund and others). Roughly, these come to at leasl 40 million DM using a method from a by-law in the Forest Act - The Forest Management Regulation NN 121/97. According to the available data, the monetarv value of electricitv provided by the hydropower station Novo Virje would be below that obtained from the annual increment of the forests it jeopardises. 3. The lowland area of Podravina around Koprivnica and Đurđevac constitutes outstanding natural wealth consisting of well-preserved lowland forests, the flow of the river Drava with its river islands, pebbly sandbanks and riparian forests, pastures and wet meadows, old Drava backwaters, as well as traditional agriculture, hedges and woodlands. The entire area is characterised with high biological diversity, while the ecotones, the bordering zones between different ecological systems, represent a particular rich plant and animal world. The natural lowland forests, with a renowned forest of Repaš on the left bank of the Drava, are highly valuable. There is a proposal to place this forest into the categorv of protected landscapes, but this proposal has not been processes yet due to a forced spatial plan with the Novo Virje hydropower station. We maintain that in the proposed Dunav, Drava, Mura Bioshpere Reserve, the lowland forests, including the forest of Repaš, would have a variety of very positive functions. These include natural-protective, tourist (ecological, hunting, peasant tourism), water-protective, hvdrological, climatic, anti-emission and genetic, as well as raw materials functions for the development of clean and ecologically acceptable timber processing industry. 4. The final study on the environmental impacts entitled: HE NOVO VIRJE: ACCEPTABLE GROUNDWATER REGIME FROM THE STANDPOINT OE PRESERVING FOREST ECOSYSTEMS is inadmissible because one basic factor was not respected. Namely, experience of a hundred vears shows that the existing water regime. influencing the development of middle-aged and older natural stands with pedunculate oak, is optimul for their growth. Furthermore, the calculation on the acceptable regime of groundwater is highly questionable, because the capillary movement of groundwater as an element of the mentioned calculation was obtained on the basis of estimated values, but without laboratory measurements. Also, the study encompassed only the forest of Repaš, which represents about 25 % of the forests to be affected by the erection of HE N. Virje. This forest differs from other forests by its vegetational composition and habi-iats, and therefore the results from Repaš cannot be applied to all the forests in the area. 5. Dieback of pedunculate oaks in the forest of Repaš occurring during the past decade is the consequence of synergistic effects of a gradual drop in groundwater levels caused by the erosion ofthe Drava riverbed. The ero-sion was brought about by the action of the upriver hydropower stations (Čakovec, Varaždin. Dubrava), but also of the simultaneous drought to w´hich lowland forest ecosystems have adapted through their long historv. Had the groundwater not dropped due to the erosion of the Drava riverbed, the pedunculate oak would have survived the drought with negligible consequences. Water management authorities should find a way of halting the erosion of riverbeds and thus create more natural conditions for the lowland forests downstream of the HE Dubrava. Key words: changes in water relations; climatic excesses; dieback of pedunculate oak; hydro-technical interventions; lowland forests of pedunculate oak | ||
| Šporčić, M., Vondra, V. | UDK 630* 945 | |
| Master´s Theses, Defended at the Faculty of Forestry in Zagreb, Upgrade Forestry pdf HR EN | 391 | |
| Grubešić, M. | UDK 630* 156 + 451 | |
| Waldbau und Wildverwalten mit Hinsicht auf die Probleme in deutschen Waldern pdf HR EN | 405 | |
| Zelić, J. | UDK 630* 288 | |
| The Role of Silkvvorm (Bombyx mori) and White Mulberry (Morus alba) in Silkvvorm Breeding and Sericulture pdf HR EN | 413 | |
| STRUČNI ČLANCI | ||
| Vukelić, M. | UDK 630* 902 + 233 | |
| Laudonov Gaj pdf HR EN | 425 | |
| Grospić, F. | UDK 630* 902 + 469 | |
| A Contribution to Assessing the Conditions in the Forestrv of Lika in the Second Part of the 19th Century pdf HR EN | 437 | |
| Božičević, I. | UDK 630* 648 | |
| A Model for Writing and Drawing up Forest Records for all Forest Enterprises in the Delnice Forest Administration pdf HR EN | 443 | |