Luc Abbadie | University Pierre and Marie Curie (original) (raw)

Papers by Luc Abbadie

Owusu-Bennoah, E., 113 Pallant, E., 273 Pendery, BM, 265 P~ rez-Soba, M., 231 Pinochet, J., 223

Plant and Soil, 1992

Field experiments about denitrification and nitrification processes have been performed in a wet ... more Field experiments about denitrification and nitrification processes have been performed in a wet savanna of West Africa (Lamto, Côte d&amp;amp;amp;amp;#x27;Ivoire). Two scales have been chosen: (i) a topographic gradient including the main forest and savanna environments; (ii) a soil profile taking into account roots and fauna effects. Denitrifying potential activity was only recorded in the surface soil: it was higher

Plant and Soil, 1996

In Lamto (C6te d'Ivoire), the savanna is a patchy environment as far as soil is concerned: tree c... more In Lamto (C6te d'Ivoire), the savanna is a patchy environment as far as soil is concerned: tree clumps and termite mounds lead to higher nutrient contents than in the surrounding savanna. Mature Borassus aethiopum (Mart.) specimens are tall palm trees dominating the community, with aerial parts located out of these nutrient-rich patches.

Plant and Soil, 1993

The effect of tree clumps on soil characteristics was investigated in a humid savanna (Lamto, C6te

Oecologia, 2001

Grazing has traditionally been viewed as detrimental to plant growth, but it has been proposed th... more Grazing has traditionally been viewed as detrimental to plant growth, but it has been proposed that under certain conditions, grazing may lead to compensatory or overcompensatory growth. However, comprehensive information on the relative role of the main functional processes controlling the response of net primary production (NPP) to grazing is still lacking. In this study, a modelling approach was used to quantify the relative importance of key functional processes in the response of annual canopy NPP to grazing for a West African humid grassland. The PEPSEE-grass model, which represents radiation absorption, NPP, water balance and carbon allocation, was used to compute total and aboveground NPP in response to grazing pressure. Representations of grazing and mineral nitrogen input to the canopy were simplified to focus on the vegetation processes implemented and their relative importance. Simulations were performed using a constant or resource-driven root/shoot allocation coefficient, and dependence or independence of conversion efficiency of absorbed light into dry matter on nitrogen availability. There were three main results. Firstly, the response of NPP to grazing intensity emerged as a complex result of both positive and negative, and direct and indirect effects of biomass removal on light absorption efficiency, soil water availability, grass nitrogen status and productivity, and root/shoot allocation pattern. Secondly, overcompensation was observed for aboveground NPP when assuming a nitrogen-dependent conversion efficiency and a resource-driven root/shoot allocation. Thirdly, the response of NPP to grazing was mainly controlled by the effect of plant nitrogen status on conversion efficiency and by the root/shoot allocation pattern, while the effects of improved water status and reduced light absorption were secondary.

Journal of Geophysical Research, 1995

Heterogeneity of soil characteristics and potential microbial activities were measured in several... more Heterogeneity of soil characteristics and potential microbial activities were measured in several humid tropical West African ecosystems and in one dry savanna ecosystem in order to explain the high spatial variability of NO fluxes observed in the field. At the landscape scale, the variability of NO emission rates in the humid zone is mainly a function of topographic position and vegetation type. The highest NO fluxes occur in the downslope nutrient-rich environment (forest) which exhibits high denitrification potential and high total mineral N accumulation. NO fluxes are low in humid savanna environments which exhibit no detectable potential denitrification. Local structures such as mounds colonized by hypogeous termites exhibit an accelerated nitrogen cycling relative to their surroundings. Ammonium is quickly converted to nitrate; the soil has high potential rates of denitrification with correspondingly high NO emissions. NO fluxes are also high in dry savanna soils with high nitrification potentials but low denitrification potentials, suggesting that NO at these sites was produced during nitrification rather than denitrification. These results underscore the importance of considering the mechanisms driving spatial variability and the need to account for them in large-scale extrapolations. Among the soil characteristics studied, denitrification potentials provide a reliable indication of high NO fluxes for the humid sites, but not for the dry sites. 1. et al., 1988; Bakwin et al., 1990; Matson et al., 1990; Davidson et al., 1991, 1993; Serra et al., 1994], but very few values of NO emission from natural tropical savannas were available. Delmas and Servant [1987] presented NO-emission rates from Copyright 1995 by the American Geophysical Union. Paper number 95JD01923. 0148-0227/95/95JD-01923. tropical forest and savanna soils in central C6te d'Ivoire. High [Johansson et al., 1988; Johansson and Sanhueza, 1988], medium IRondon et al., 1993], and low NO-emission rates [Sanhueza et al., 1990] have been reported in savannas of Venezuela for soils with high, medium, or low N-nutrient contents, respectively. As for all nitrogen-cycling processes, spatial heterogeneity of nitrogen fluxes from terrestrial ecosystems is high [Schimel et al., 1988; Matson et al., 1990; Ambus and Christensen, 1994; D. Serqa et at., Emission of nitrogen monoxide from African tropical ecosystems: spatial variability at local and regional scale, submitted to Journal of Geophysical Research, 1995, hereinafter referred to as D. Serca et at., 1995], so that extrapolation of local measurements to the ecosystem level and to the regional scale is difficult. In this context the factors contributing to that spatial variability need to be betfer understood. Yoshinari [1993] recently reviewed processes responsible for nitrogen oxide emission in tropical soils. Emission of nitrogen monoxide can result from nitrification, denitrification, or chemodenitrification in soils [Firestone and Davidson, 1989; Remde and Conrad, 1991; Serra et al., 1994] and the rates of emission depend on soil characteristics such as water content, diffusion, temperature, and acidity ISlemr and Seiler, 1991; Rondon et al., 1993] in relation to edaphic, climatic, and vegetation factors [Galbally, 1989]. Generally, for a given soil, saturation allows 23,133 23,134 LEROUX ET AL.: NO EMISSION FROM WEST AFRICAN SAVANNAS where extensive studies on mound characteristics have been conducted [Abbadie et al., 1992]. A complementary experiment was carried out in a 3-year-old dry fallow savanna at Banizoumbou (13ø5'N and 3øE, Niger).

Journal of Agronomy and Crop Science, 2007

Free-living nitrogen (N) fixation can be important for sustainable soil fertility, particularly i... more Free-living nitrogen (N) fixation can be important for sustainable soil fertility, particularly in extensively managed soils with low abundance of leguminous plant species. However, the factors affecting free N 2 -fixation in situ are still poorly documented. We investigated the role of microbial active biomass activity, particularly substrateinduced respiration (SIR) and net N mineralization, on the free-living N 2 fixation in soils under a semi-natural grassland ecosystem in France. Analysis of replicated bulk soil and rhizospheric soil samples obtained from sites experiencing contrasting grazing regimes revealed highly significant negative relationships (P < 0.01) between free-living N 2 -fixation and SIR or N-mineralization with a significant rhizosphere effect. The study has demonstrated that the activity of free-living N 2 -fixers is more important in soils having low active microbial biomass and low N-mineralization rates in these permanent grasslands.

Environmental Microbiology, 2006

Management by combined grazing and mowing events is commonly used in grasslands, which influences... more Management by combined grazing and mowing events is commonly used in grasslands, which influences the activity and composition of soil bacterial communities. Whether observed effects are mediated by management-induced disturbances, or indirectly by changes in the identity of major plant species, is still unknown. To address this issue, we quantified substrate-induced respiration (SIR), and the nitrification, denitrification and free-living N 2 -fixation enzyme activities below grass tufts of three major plant species ( Holcus lanatus, Arrhenatherum elatius and Dactylis glomerata ) in extensively or intensively managed grasslands. The genetic structures of eubacterial, + ) available to plants and N conservation at the ecosystem level. Ecosystem-scale 1006 A. K. Patra et al.

Ecological Monographs, 2005

Enhancement of soil nitrogen (N) cycling by grazing has been observed in many grassland ecosystem... more Enhancement of soil nitrogen (N) cycling by grazing has been observed in many grassland ecosystems. However, whether grazing affects the activity only of the key microbial functional groups driving soil N dynamics or also affects the size (cell number) and/or composition of these groups remains largely unknown. We studied the enzyme activity, size, and composition of five soil microbial communities (total microbial and total bacterial communities, and three functional groups driving N dynamics: nitrifiers, denitrifiers, and free N 2 fixers) in grassland sites experiencing contrasting sheep grazing regimes (one light grazing [LG] site and one intensive grazing [IG] site) at two topographical locations. Enzyme activity was determined by potential carbon mineralization, nitrification, denitrification, and N 2 fixation assays. The size of each community (except N 2 fixers) was measured by the most-probable-number technique. The composition of the total soil microbial community was characterized by phospholipid fatty acid analysis (PLFA), and the genetic structure of the total bacterial community was assessed by ribosomal intergenic spacer analysis. The genetic structures of the ammonia-oxidizing, nitrate-reducing, and N 2fixing communities were characterized by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) or by polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) targeting group-specific genes. Greater enzyme activities, particularly for nitrification, were observed in IG than in LG sites at both topographical locations. The numbers of heterotrophs, nitrifiers, and denitrifiers were higher in IG than in LG sites at both topographical locations. The amplitude of changes in community size was higher than that of community enzyme activity. Phospholipid and nucleic acid analyses showed that the composition/structure of all the communities, except nitrate reducers, differed between IG and LG sites at both locations. For each community, changes in activity were correlated with changes in the occurrence of a few individual PLFAs or DNA fragments. Our results thus indicate that grazing enhances the activity of soil microbial communities but also concurrently induces changes in the size and composition/structure of these communities on the sites studied. Although the generality of our conclusions should be tested in other systems, these results are of major importance for predicting the effects of future disturbances or changed grazing regimes on the functioning of grazed ecosystems.

Applied Soil Ecology, 2011

Revista Brasileira de Ciência do Solo, 2003

Espécies de eucalipto e acácia são amplamente utilizadas em plantios agroflorestais e reflorestam... more Espécies de eucalipto e acácia são amplamente utilizadas em plantios agroflorestais e reflorestamentos. Com o intuito de comparar a reconstituição das camadas orgânicas do solo, i.e., dos horizontes húmicos, estabelecendo-se uma relação com propriedades edáficas, sob plantações de Acacia mangium e Eucalyptus grandis, foram feitas coletas dos horizontes holorgânicos e hemiorgânicos do solo. Os referidos plantios encontravam-se na região de Tabuleiros Terciários no norte do estado do Espírito Santo e pertenciam à Reserva Natural da Vale do Rio Doce. As coletas foram feitas quando os plantios tinham sete anos de idade, em quatro estações. Acacia mangium apresentou maior estoque de folhiço (10 t ha -1 , em média), tanto na camada L, de folhas inteiras, como na camada F, de folhas fragmentadas, do que Eucalyptus grandis (5 t ha -1 , em média). O material foliar em acácia apresentou menor relação C/N que o de eucalipto, cerca da metade, decorrente dos maiores teores de nitrogênio. Quanto às análises químicas de carbono e nutrientes, no solo sob Acacia mangium, foram observadas, de modo geral, maiores quantidades destes elementos que no solo sob Eucalyptus grandis (e.g., carbono: 1,74 dag kg -1 vs 1,23 dag kg -1 e cálcio: 3,34 cmol c kg -1 vs 2,75 cmol c kg -1 ). O conjunto destes resultados evidencia que os aportes orgânicos sob Acacia mangium em relação a Eucalyptus grandis foram responsáveis pela maior incorporação de matéria orgânica e nutrientes ao solo. Estes dados, no entanto, comparados aos obtidos em estudos na floresta primária, mostraram que o carbono e os nutrientes do solo, em ambas as plantações, são menores que na floresta, evidenciando que, após sete anos de plantio, os teores de fertilidade e matéria orgânica do subhorizonte A 11 não estavam restabelecidos.