Effects of forest thinning on the streamwater chemistry of two forest watersheds in the Bavarian Alps

Journal article


Publication Details

Author(s): Bäumler R
Journal: Forest Ecology and Management
Publisher: Elsevier
Publication year: 1999
Pages range: 119-128
ISSN: 0378-1127
Language: English


Abstract


Two well-buffered mountain forest watersheds were studied with regard to streamwater chemistry and the impact of forest thinning. The areas are located in the Bavarian Alps near lake Tegernsee, 50 km southwest of Munich. In order to get information about the influence of disturbances on the streamwater chemistry 40% of the trees were removed from one watershed after two years of monitoring. The trees were removed by crane to avoid soil damage and erosion. The second watershed was used as a reference. The output at the weirs is characterized, in general, by a strong export of silicate, alkali and alkaline earth cations, and bicarbonate. Acidity and nitrogen accumulate in the watersheds. Both areas are subject to a continuously increasing load of acidity. The acidity is mainly buffered by cation exchange and silicate hydrolysis. This is indicated by continuously decreasing pH values and the dominance of Ca2+ and silicic acid in the streamwater. Strong changes in the water chemistry along the flowpath indicate that rainwater will be stored in the system for sometime, and water derived from the headwater areas influences the discharge. During precipitation events the new rainwater replaces pre-event water, stored in soils, which had a longer contact time with the biotic and abiotic soil matrix. Acute effects of the selective harvest are leveled in the streamwater by multiple buffer reactions. The discharge of the disturbed watershed was increased by the reduction of interception and transpiration. Increased rates of mineralization and acidity loads caused an increase in ion concentration and solution load in the discharge from the disturbed area. NH4/+ showed the strongest effects compared to the reference area and the pre-event period. The changes in the runoff returned to pre-event conditions about one year after the disturbance.



FAU Authors / FAU Editors

Bäumler, Rupert Prof. Dr.
Professur für Geographie

Last updated on 2018-09-08 at 05:24