Title: Woody vegetation for integrated gully erosion control in Tigray, Ethiopia - focus on seedling establishment and treatment
Authors: Reubens, Bert
Poesen, Jean
Nyssen, Jan
Zenebe, Amanuel
Haile, Mitiku
Deckers, Jozef A.
Muys, Bart #
Issue Date: 2008
Conference: 2nd International Conference on Eco-engineering: the use of vegetation to improve slope stability edition:2 location:Beijing, China date:14-17 July 2008
Abstract: In the highlands of northern Ethiopia, land degradation is dramatic, with loss of topsoil by water erosion and water-induced gully erosion and landslides as most important processes. The protective role of vegetation has been proven in many studies, and especially plant roots could play an important role in slope stabilisation and erosion control. In this context there is a need for scientific research to better understand the effects of vegetation and their roots on geomorphologic processes in this and other semi-arid regions.
The aim of this research is to better understand woody vegetation implementation possibilities for gully erosion control, in a practice-oriented approach.
A field trial is set up in Tigray (Ethiopia) for in situ evaluation of seedling establishment in and around gullies. In this experimental setup it is examined for seedlings of Acacia etbaica, Sesbania sesban and Dodonea angustifolia which growing conditions are most suited and what level of protection is needed. Two experimental sites are selected: one on a soil consisting mainly of sandy colluvium on top of a cambic vertisol, and one on a vertisol. Two irrigation treatments are applied and in addition 24 random selected specimens receive no water at all. Half of the seedlings have an open bamboo shelter, protecting the young plants against too heavy sunlight, sediment, flood and damage by e.g. rabbits or birds. This treatment also follows the observation that establishment of seedlings is facilitated under shrub canopies. Seedlings are furthermore planted on three different gully positions: i.e. top, side wall and floor, each experiencing specific position-related stress conditions. Seedling planting and initial measurements took place in August 2006. Seedling survival is evaluated every week, and a detailed description of vegetation characteristics takes place every two months. Land use, detailed topography, gully characteristics, runoff discharge, changes in sediment deposition characteristics in the gully, and several climatic as well as soil characteristics are also evaluated.
Although the experiment is still going on, some promising intermediate results were obtained so far. Overall survival rate after 10 months is 86%, with mortality mainly caused by flooding in the gully floor. Sesbania appears to be fastest growing, with an average growth of 19.5 cm/month (23 cm/month in the rainy season). Eight months after germination, this species already produced new seedlings in the sediment-rich gully floor. Soil type has a serious influence on growth performance: e.g. for Sesbania 30 cm/month on the vertisol and only 9 cm/month on the sandy soil. Other effects remain to be analysed in more detail. Acacia etbaica has the interesting characteristic of resprouting after complete coverage by sediment deposition. The seedlings which received no water generally survived the first drought period well.
Publication status: published
KU Leuven publication type: IMa
Appears in Collections:Division Forest, Nature and Landscape Research
Division of Geography & Tourism
Division Soil and Water Management
# (joint) last author

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