Preliminary communication
The Reconstruction of the Water Regime in Lowland Forests in Support of Sustainable Management
Ivan Pilaš
; Hrvatski šumarski institut Jastrebarsko
Špela Planinšek
; Gozdarski inštitut Slovenije, Ljubljana, Slovenija
Abstract
Amongst the existing forest types in Europe, the specific biological function of water is nowhere more distinctive than in the lowland forest ecosystems. Consequently, no existing forest types are more shaped by historic hydrologic conditions, altered by manmade deviations from the natural water regime and vulnerable to consequences of global warming. The lowermost parts of the lowland forests, the wetlands, present the transitional zones between terrestrial and aquatic ecosystems i.e. ponds, lakes, streams and rivers. Nowadays, due to excessive urbanization and the spread of agriculture, the total area of lowland forests and wetlands has been significantly reduced. One of the largest complexes of alluvial floodplain wetlands and lowland forests in Europe are situated in the South-East Europe, in the Sava and Drava River basins, tributaries to the Danube River. The Sava River is a unique example of a river where the floodplains are still intact, supporting both flood alleviation and biodiversity. Continental lowland forests in Croatia cover an area of more than 200.000 ha with a significant role in forestry production, flood reduction, recharging groundwater reserves, as well as filtering pollutants. The natural forest vegetation consists of mainly hardwood tree species such as the common oak (Quercus roburL.), field ash (Fraxinus excelsior Vahl.), common hornbeam (Carpinus betulus L.) and softwood species such as black alder (Alnus glutinosa(L.) Geartn.), poplars (Populussp.) and willows (Salixsp.). For the biological diversity of lowland forests and attached wetlands is strongly important specific combination of hydrology and soils. The development of these forests in history was determined by regular seasonal alternations of groundwater tables (hydro period) and periodic flooding. This paper presents the possibilities for the re-establishment of the water regime of lowland forests as one option to reduce the impact of climate change in the future. To reduce negative impacts of anthropogenic alternations in the groundwater regime from the past and to attenuate slow down future very possible prolongation of droughts and water scarcity in the lowlands, various forest managerial and engineering practices could be considered. Basically, there are potentially two main contrasted measures of soil water balance manipulation: drainage of soils (through drainage ditches and channels) which contribute to decreasing the groundwater tables and forest management i.e. (tendering and thinning) which contribute to increased soil water content and increase in the groundwater level. Through these water table management practices, the amount of soil water required for the survival of lowland forests could be maintained to some degree to attenuate the negative hydrologic trends and natural hazards such as droughts. The comprehensive methodological review of activities that must precede such reconstruction activities are presented. As the initial segment all the major components of floodplain ecosystems – the morphology of the terrain, hydrography, soils stratigraphy, vegetation and anthropogenic influences – should be assessed. As a next step methodological options towards how to obtain the knowledge of the natural water regime prior anthropogenic hydrotechnical activities which caused the creation of the ecosystem in its current form are presented. For this purpose the morphology of hydromorphic soils i.e. relict indicators of natural water regime in lowland habitats are assessed. The next step includes the spatial determination of critical areas or hot spots, threatened by excessive falls in the groundwater level on which specific measures can be applied to return to natural water regime conditions (i.e. water retention in dry riverbeds).
Keywords
Lowland forests; water regime; groundwater; relict indicators; soil morphology; hydro-technical measures
Hrčak ID:
72322
URI
Publication date:
14.10.2011.
Visits: 2.571 *