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Soumare A.,Cheikh Anta Diop University | Soumare A.,Laboratoire Communications Of Microbiologie Lcm | Sall S.N.,Saint Louis University | Sanon A.,Institute Of Recherche Pour Le Developpement Ird | And 5 more authors.
Applied Ecology and Environmental Research | Year: 2016

Eucalyptus camaldulensis has been the main exotic species planted in reforestation programs in the tropics due to its fast growth and adaptability to climate variations. Based on the premise that the conversion from natural grazed pastures to commercial Eucalyptus plantations generates significant changes in soil properties, we assessed the impact of this exotic plantation on soil chemical and biological indicators. The study was conducted in 6 plantations across Senegal following a decreasing rainfall gradient from south to north. The plantations were divided in three lots according to their age: young plantations (established in 2003, 6 years old); intermediate plantations (established in 1998, 11 years old) and old plantations (established in 1982 and 1983, 26 years old). Our results clearly showed that E. camaldulensis plants significantly modified soil pH and soil bacterial community at all sites regardless of the age of the plantation. Microbial biomass (assessed by substrate-induced respiration), community structure (assessed by denaturing gradient gel electrophoresis profiles) and function (assessed by Catabolic Response Profile using different substrates) were all significantly decreased. The acidifying effect of E. camaldulensis, the effect of high level of polyphenols and their impact on microbial communities and ecosystem functioning were discussed. © 2016, ALÖKI Kft., Budapest, Hungary.

Soumare A.,Cheikh Anta Diop University | Soumare A.,Laboratoire Communications Of Microbiologie Lcm | Manga A.,University Gaston Berger | Fall S.,Institute Senegalais Of Recherches Agricoles | And 5 more authors.
Agroforestry Systems | Year: 2014

This study aimed to test the effect of Eucalyptus litter on growth, roots symbioses status and nutrition of Sahelian acacia’s seedlings. Sangalkam sandy soil was amended with two levels (1 and 5 %) of Eucalyptus litter. As control of the effect of litter addition, sandy soil was amended with 1 and 5 % of maize litter. In addition, a control without amendment was established to highlight any changes caused by amendments. Eucalyptus litter impact on A. senegal, A. seyal and A. albida was determined by comparing plants grown in amended treatments to plants grown in both control treatments. Results indicated that Eucalyptus litter leads to changes in soil pH and phenol content. These changes negatively affect plant growth, their symbiotic status (mycorrhization, nodulation), and their nutrition (leaf chlorophyll content, total carbon, total nitrogen and phosphorus in shoots). Likewise, soil enzymatic activities were modified. Acid phosphatase was higher in Eucalyptus litter amended soil than in control while alkaline phosphatase was higher in control soil than in Eucalyptus litter amended soil. Positive correlations were recorded between roots symbioses and shoots mineral content suggesting that arbuscular mycorrhizal fungus and N-fixing symbiosis promote mineral uptake and storage in leaves. However, polyphenolic content of added litter was negatively linked to roots symbioses and growth of tested acacias. Results showed also, Eucalyptus litter impact on acacias growth was genotype and dose dependent. © 2014, Springer Science+Business Media Dordrecht.

Sene G.,Laboratoire Communications Of Microbiologie Lcm | Sene G.,Institute Senegalais Of Recherches Agricoles | Thiao M.,Laboratoire Communications Of Microbiologie Lcm | Thiao M.,Cheikh Anta Diop University | And 10 more authors.
Microbial Ecology | Year: 2013

Several fast-growing and multipurpose tree species have been widely used in West Africa to both reverse the tendency of land degradation and restore soil productivity. Although beneficial effects have been reported on soil stabilization, there still remains a lack of information about their impact on soil microorganisms. Our investigation has been carried out in exotic and native tree plantations of 28 years and aimed to survey and compare the abundance and genetic diversity of natural legume-nodulating rhizobia (LNR). The study of LNR is supported by the phylogenetic analysis which clustered the isolates into three genera: Bradyrhizobium, Mesorhizobium, and Sinorhizobium. The results showed close positive correlations between the sizes of LNR populations estimated both in the dry and rainy seasons and the presence of legume tree hosts. There were significant increases in Rhizobium spp. population densities in response to planting with Acacia spp., and high genetic diversities and richness of genotypes were fittest in these tree plantations. This suggests that enrichment of soil Rhizobium spp. populations is host specific. The results indicated also that species of genera Mesorhizobium and Sinorhizobium were lacking in plantations of non-host species. By contrast, there was a widespread distribution of Bradyrhizobium spp. strains across the tree plantations, with no evident specialization in regard to plantation type. Finally, the study provides information about the LNR communities associated with a range of old tree plantations and some aspects of their relationships to soil factors, which may facilitate the management of man-made forest systems that target ecosystem rehabilitation and preservation of soil biota. © 2012 Springer Science+Business Media, LLC.

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