Stable coexistence of contrasted nitrification statuses in a wet tropical savanna ecosystem

Abstract

Summary 1.Wet tropical savannas are characterized by strong environmental constraints-particularly low soil nutrient availability-associated with high plant productivity. Nitrogen recycling, and especially nitrification, is supposed to be a strong determinant of the balance between conservation and loss of nutrients at the ecosystem level. Savanna facies dominated by the grass Hyparrhenia diplandra (Andropogoneae) are known to exhibit low levels of nitrification and thus avoid nitrate losses. 2. By comparing two sites in the Lamto area (Côte d'Ivoire, West Africa) with similar soil physico-chemical characteristics and equally dominated by H. diplandra (80% of the grass cover), it was demonstrated that, within this facies, nitrification is highly heterogeneous, with a 240-fold variation in potential nitrification within a specific site. 3. In order to test whether these differences can be considered as permanent in this ecosystem, nitrate reductase activities were compared on H. diplandra plantlets from the two sites, cultivated under identical conditions in the presence of nitrate. The leaves of plants originating from the high nitrification site were always able to reduce nitrate at a significantly higher rate than those from the low nitrification site. This observation indicates a long-term adaptation of the plants and stable nitrification behaviour. 4. Lamto can thus be considered as a contrasted dual ecosystem relative to its nitrogen cycle. The two sites studied therefore constitute useful models to assess the determinism of nitrification in wet savannas and the role of this process on nitrogen retention in such ecosystems.

Repression of potential nitrification activities by matgrass sward species

“…The results of the current study confirm studies from Lata et al (1999Lata et al ( , 2000Lata et al ( , 2004 on natural and semi-natural vegetation, and enlarge the view that not only crop plant species can exude BNI (Subbarao et al 2007a, b;Zakir et al 2008). As was shown by Subbarao et al (2006Subbarao et al ( , 2007cSubbarao et al ( , 2009a exudates from the roots of the grass species Brachiaria humidicola and Leymus racemosus were able to influence the activity of nitrifying bacteria.…”

“…Zakir et al (2008) found an increasing effect of ammonium and plant age on the release of nitrification-inhibiting compounds from the roots of Sorgum bicolor. Lata et al (1999) discovered a strong correlation between the variation in potential nitrification rate and the characteristics of nitrogen nutrition of grasses in savannas. Mature grassland systems have the ability to inhibit nitrification or have a balanced inhibition-stimulation impact (Lata et al 2000).…”

“…Up to now, several indications for exudation of BNI have been demonstrated in crop plant species (Subbarao et al 2007a, b;Zakir et al 2008;Subbarao et al 2009a, b) and Hyparrhenia sp. dominated savannas (Lata et al 1999(Lata et al , 2000(Lata et al , 2004. In the current article, we focus on the vegetation level.…”

Potential for biological nitrification inhibition to reduce nitrification and N2O emissions in pasture crop–livestock systems

“…The BNI function in plants thus can exert a positive influence on NUE agronomic by reducing N loss associated with nitrification-denitrification 2013b). Recent modeling studies suggest that tropical grasses that inhibit nitrification exhibit a twofold greater productivity than those that lack such ability (Lata et al, 1999;Boudsocq et al, 2009 and.…”

Eficiência de uso de nitrogênio pela cana-de-açúcar: diferenças genotípicas, preferência por amônio e emissão de N2O

“…A grande variação e o baixo aproveitamento podem estar relacionados as perdas do N no sistema solo-planta. Essas perdas são oriundas dos processos de lixiviação do nitrato (NO3 -) que deixa a região de exploração das raízes das plantas (OLIVEIRA et al, 1999), podendo ser perdido para atmosfera através do processo desnitrificação em condições de baixo suprimento de oxigênio (PIERZYNSKI et al, 2000), volatilização da amônia (NH3) , e perdas gasosas de nitrogênio (N2O) pelo solo (CERRI et al, 2011) e pela parte aérea das plantas Algumas plantas são capazes de inibir a nitrificação (LATA et al, 1999; . No Brasil, inúmeros trabalhos têm relacionado o cultivo ou a ocorrência de Brachiaria sp à predominância de N na forma amoniacal (CARMO et al, 2005;FERNANDES et al, 2011).…”