Role of forests in headwater control with changing environment and society

Abstract

Forest practices in headwater catchments are related to environmental and social contexts. The aim of this study is to analyse the changing protective functions of forests in the upper plain of the Jizera Mts. (North Bohemia, Czech Republic) since the second half of the 19th century. With time, forests have gradually changed from native stands to spruce plantations (Picea abies), introducing exotic conifers (more resistant to air pollution), and, recently, back to more diverse mixed stands. The priority in protective forest functions there shifted from flood protection to integrated control of water resources (quantity and quality). In the 1980s, forest – water interactions were degraded by consequences of extreme acid atmospheric deposition, forest die-back, and extensive clear-cut. In the Jizerka catchment, first signs of recovery were observed in the early 1990s, but, stream waters there are still affected by prolonged acidification. While reconstruction of stream water chemistry at Jizerka follows the drop of the acid deposition in some 5 years, the revival of stream biota takes 10–15 years. In 2071–2100, the projected climate change shows rising annual air temperatures by 3.0–4.6 °C, decreasing water yield by 65–123 mm, 60% drop in ‘minimum residual discharge’, and 20–30% rise in peak-flows. However, these projected environmental changes cannot substantially decline the high potential in water resource recharge, or, start reverse processes in recent recovery from acidification and radically affect the existence of planned mixed forests in the upper plain of the Jizera Mts.