News Dr. NSENGIMANA Venuste, GTI alumnus, presented his Ph. D. thesis for the award of the degree of Doctor (PhD) in Agronomy and Bioengineering

On November 20th 2018, Dr. NSENGIMANA Venuste presented his Ph. D. thesis and was awarded the degree of Doctor in Agronomy and Bioengineering by the University of Liège, Gembloux Agro-Bio Tech. The title of his thesis is: ‘Use of Soil and Litter Arthropods as Biological Indicators of Soil Quality in Southern Rwanda’.

Source CEBioS
Release date 27/11/2018
Geographical coverage Li├Ęge, Belgium
Keywords thesis, biological indicator, soil quality, Rwanda

Abstract:

To assess soil quality under different land uses by the use of soil and litter arthropods as biological indicators, a research was conducted in the Arboretum of Ruhande and the Rubona agricultural research station in southern Rwanda. Soil and litter arthropods were collected by pitfall sampling technique and identified to the family level. Ants (Hymenoptera: Formicidae) were identified to species le vel. Soil cores were collected and analyzed for soil organic carbon, total nitrogen, available phosphorus, pH, aggregate stability, cation exchange capacity, electrical conductivity, silt, and clay and sand soil textures. C:N ratios were calculated from the mass of carbon to the mass of nitrogen. Higher levels of total nitrogen, soil organic carbon, and clay and silt soil texture were found in native and exotic tree species. Higher levels of cation exchange capacity, pH, and electrical conductivity were found in native tree species and banana plantations, while higher levels of available phosphorus, aggregate stability and sand soil texture were found in coffee and banana plantations. The analysis of the abundance of collected soil and litter arthropods indicated higher abundance of the most of identified families in native and exotic tree species than in the varieties of coffee and banana plantations. Families of Scolopendridae, Trombiculidae, Eosentomidae, Formicidae and Staphylinidae showed strong correlation with soil physicochemical properties. Formicidae highly occurred in all land uses and discriminated between clay, sand, aggregate stability, pH, available phosphorus, electrical conductivity and cation exchange capacity. The ecological functions of identified families contribute to the soil quality through predation, decomposition, bioturbation and phytophagous that increase soil organic matter and facilitate water retention and soil aeration. The taxonomy of ants to species level indicated 30 species belonging to 14 genera, and four subfamilies, theFormicinae, Dorylinae, Myrmicinae and Ponerinae. These species correlated with soil properties in different ways, but their ecological functions that contribute to soil quality are not yet well documented. We recommend further studies to be replicated in other land uses and ecological zones of Rwanda, to include the impact of climate variability, altitudinal variation, functional diversity, metal and soil microbiology and the taxonomy of the entire community composition of collected soil and litter arthropods to species level in order to generalize these findings.

 

The full thesis is available on the ULiège ORBI.