Nodulation and dinitrogen fixation of legume trees in a tropical freshwater swamp forest in French Guiana

Abstract

Nodulated legume trees comprised 43% of the stand basal area in the low, most frequently flooded microsites, and 23% in higher, drier microsites in a tropical freshwater swamp forest in French Guiana. Dinitrogen fixation in Pterocarpus officinalis, Hydrochorea corymbosa and Inga pilosula was confirmed by acetylene reduction assay (ARA), presence of leghaemoglobin in nodules and the N-15 natural abundance method. The results for Zygia cataractae were inconclusive but suggested N-2 fixation in drier microsites. Nodulated Inga disticha had a N-15-to-N-14 ratio similar to non-N-2-fixing trees, but ARA indicated nitrogenase activity and leghaemoglobin was present in nodules. All bacterial strains were identified as Bradyrhizobium spp. according to the partial 16S rDNA sequences, and they were infective in vitro in the model species Macroptilium atropurpuretan. About 35-50% of N in the leaves of P. officinalis, H. corymbosa and I. pilosula was fixed from the atmosphere. Dinitrogen fixation was estimated to contribute at least 8-13% and 1728% to whole-canopy N in high and low microsites, respectively. Symbiotic N, fixation appears to provide both a competitive advantage to legume trees under N-limited, flooded conditions and an important N input to neotropical freshwater swamp forests

Natural abundance of 15N in two cacao plantations with legume and non-legume shade trees

“…High foliar d 15 N was also observed in some other, but not all, nodulating Inga spp. (Koponen et al 2003;Roggy et al 1999), which suggests that this characteristic may be associated to some subgroups of the large genus.…”

Facultative nitrogen fixation by canopy legumes in a lowland tropical forest

“…Mature forests are often characterized by low rates of nodulation (Sylvester-Bradley et al 1980;Walter and Bien 1989;Moriera and Franco 1994;Pearson and Vitousek 2001). In addition, secondary and flooded forests often report elevated nodulation (Sylvester-Bradley et al 1980;Moriera and Franco 1994;Saur et al 1998;Koponen et al 2003).…”

Neotropical Legume Tree Inga edulis Forms N2-fixing Symbiosis with Fast-growing Bradyrhizobium Strains

“…ex G. Don in pot experiments and in shade trees in coffee plantations (Roskoski, 1981(Roskoski, , 1982Roskoski and Van Kessel, 1985). Potential N 2 -fixers were identified in a Neotropical lowland rain forest (Roggy et al, 1999) and a freshwater swamp forest (Koponen et al, 2003) by assuming that N 2 -fixing plants should have a low natural deviation from the ratio of 15 N to 14 N in atmospheric N 2 (low d 15 N value) and high foliar N concentration (Martinelli et al, 1999;Yoneyama et al, 1993). Three Inga spp., including I. edulis, in the rain forest and one species in the swamp forest had a high d 15 N value, which suggests no N 2 fixation; however, the trees were nodulated and exhibited nitrogenase activity in the acetylene reduction assay (ARA), which suggests that they do fix N 2 .…”

“…Three Inga spp., including I. edulis, in the rain forest and one species in the swamp forest had a high d 15 N value, which suggests no N 2 fixation; however, the trees were nodulated and exhibited nitrogenase activity in the acetylene reduction assay (ARA), which suggests that they do fix N 2 . Sixteen rain forest (Roggy et al, 1999) and two swamp forest (Koponen et al, 2003) Inga spp. were classified as potential N 2 -fixers by leaf N concentration, ARA, and d 15 N. It seems that there is variability within the genus Inga for either N 2 fixation itself or discrimination against 15 N that affects the reliability of the 15 N natural abundance estimates.…”