Soil-plant dynamics of water, nitrogen and sulfur: A study on indigenous and exotic tree species in Munessa Forest, Ethiopia
type: CreativeWork
description: Forest plantations are necessary to counteract the destruction of tropical montane forests. Sustainable forestry requires comprehensive knowledge of tree effects on site conditions and nutrient cycling, but substantial information is lacking even for widely-planted species. In my work, I aimed at identifying such plant effects on ecosystem dynamics, focussing on water, nitrogen (N) and sulfur (S), which included the development of a stable-isotope methodology for S. Based on a characterization of the soils of the study area at the Main Ethiopian Rift Valley escarpment, experimental plots were set up in neighbouring stands of a natural forest dominated by Podocarpus falcatus and in plantations of Cupressus lusitanica and Eucalyptus globulus. All investigations on the ecology of these trees were conducted on the same single-tree centred plots in a combination of time series of natural parameters with isotope tracer experiments, employing inorganic 15N tracers and litter labelled with 34S. Soils of the region reflected the influence of climate and relief, while the homogeneous bedrock caused no influence throughout the region. Methodological work to improve d34S analysis was a precondition for the ecological study on S dynamics. Technical adjustments to the analytical system including a liquid-nitrogen trap reduced the amount of S required for reliable d34S determination by a factor of six compared to the conventional procedure. Soil-plant water dynamics were strongly related to the root system. P. falcatus with high fine root biomass to below 1 m depth appeared active in redistributing soil water. Its physiological response to changing soil moisture with a marked reduction in transpiration (by a factor of six) at dry conditions had a further balancing effect. P. falcatus and C. lusitanica expanded their root systems substantially in the dry season, shifting to deeper layers. Seasonality was very weakly expressed for root biomass and depth of water uptake under E. glob…
abstract: Forest plantations are necessary to counteract the destruction of tropical montane forests. Sustainable forestry requires comprehensive knowledge of tree effects on site conditions and nutrient cycling, but substantial information is lacking even for widely-planted species. In my work, I aimed at identifying such plant effects on ecosystem dynamics, focussing on water, nitrogen (N) and sulfur (S), which included the development of a stable-isotope methodology for S. Based on a characterization of the soils of the study area at the Main Ethiopian Rift Valley escarpment, experimental plots were set up in neighbouring stands of a natural forest dominated by Podocarpus falcatus and in plantations of Cupressus lusitanica and Eucalyptus globulus. All investigations on the ecology of these trees were conducted on the same single-tree centred plots in a combination of time series of natural parameters with isotope tracer experiments, employing inorganic 15N tracers and litter labelled with 34S. Soils of the region reflected the influence of climate and relief, while the homogeneous bedrock caused no influence throughout the region. Methodological work to improve d34S analysis was a precondition for the ecological study on S dynamics. Technical adjustments to the analytical system including a liquid-nitrogen trap reduced the amount of S required for reliable d34S determination by a factor of six compared to the conventional procedure. Soil-plant water dynamics were strongly related to the root system. P. falcatus with high fine root biomass to below 1 m depth appeared active in redistributing soil water. Its physiological response to changing soil moisture with a marked reduction in transpiration (by a factor of six) at dry conditions had a further balancing effect. P. falcatus and C. lusitanica expanded their root systems substantially in the dry season, shifting to deeper layers. Seasonality was very weakly expressed for root biomass and depth of water uptake under E. glob…
author: Fritzsche, Florian
date published: 2006-02-08
date modified: 2026-07-27T18:49:26Z
provider: Universität Bayreuth
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Universität Bayreuth