Effects of changes in tree species composition on water flow dynamics--Model applications and their limitations

• Published in: Plant and soil 2004-07, Vol.264 (1-2), p.13-24
• Main Authors: Armbruster, M, Seegert, J, Feger, K.H
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Catchments; coniferous forests; continuous cropping; deciduous forests; Deciduous trees; Earth sciences; Earth, ocean, space; Exact sciences and technology; Fagus sylvatica; forest ecosystems; Forest hydrology; forest management; Forest management. Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration; Forest soils; Forest stands; forest trees; Forestry; Fundamental and applied biological sciences. Psychology; Hydrologic models; Hydrology; Hydrology. Hydrogeology; Interception; Mixed forests; Mixed stands; Mountains; Picea abies; Pine trees; Plant species; plant-water relations; Precipitation; pure stands; Retention capacity; Root distribution; silvicultural practices; Soil dynamics; Soil moisture; Soil permeability; Soil water; Species composition; species diversity; Stand types and stand dynamics. Silvicultural treatments. Tending of stands. Natural regeneration; Stream discharge; Stream flow; Synecology; Terrestrial ecosystems; Transpiration; Trees; Water flow; watershed hydrology; Watersheds
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1023/B:PLSO.0000047716.45245.23

Water-plant relations play a key role in the water cycling in terrestrial ecosystems. Consequently, changes in tree species composition may have distinct effects on the water retention capacity as well as on the pattern of streamflow generation. Such changes may result from modified interception properties and transpiration related to differences in canopy properties and root distribution. In order to evaluate the potential hydrological effects of the current silvicultural conversion from monocultural conifer stands into mixed or pure deciduous stands the hydrological model BROOK90 was applied to two forested upland catchments in Germany. The Rotherdbach catchment (9.4 ha, 93 yr-old Norway spruce) is situated in the Eastern Ore Mountains. The Schluchsee catchment (11 ha, 55-yr-old Norway spruce) is located in the higher altitudes of the Black Forest. The calibrated model is capable to describe rather well the temporal variation of streamflow but also the portions of the individual flow components. Data for a beech scenario were adapted for each site using a standard parameter set for deciduous trees provided by BROOK90. The annual discharge in the fictional beech stand at Rotherdbach is 30 to 50% higher compared to spruce with an increase of soil moisture and especially the slow streamflow components. This mainly results from low interception rates during winter time. In contrast, the spruce stand has a permanently higher interception rate. Effects of tree species conversion are moderate at Schluchsee. The annual discharge of a fictional beech stand at Schluchsee is 7 to 14% higher compared to spruce. There in contrast to Rotherdbach, effects of tree species conversion on soil moisture dynamics are small since vertical percolation in the highly permeable soil dominates and precipitation is abundant. Practical forestry will favorably establish mixed beech-spruce rather than pure beech stands. However, it is critical to simulate mixed stands with BROOK90. Therefore, a simple summation of model results from spruce and beech according to their respective area in a fictional mixed stand can only be a first approximation. Advanced hydrological simulation of mixed stand conditions should regard interactions of tree species and spatial parameter distribution. However, this is not yet feasible due to a distinct lack of information. As a consequence, there is a strong need to collect relevant hydrological and ecophysiological data in mixed stands in the future.