Ecology of Nitrogen Fixing, Nitrifying, and Denitrifying Microorganisms in Tropical Forest Soils

Abstract

Soil microorganisms play important roles in nitrogen cycling within forest ecosystems. Current research has revealed that a wider variety of microorganisms, with unexpected diversity in their functions and phylogenies, are involved in the nitrogen cycle than previously thought, including nitrogen-fixing bacteria, ammonia-oxidizing bacteria and archaea, heterotrophic nitrifying microorganisms, and anammox bacteria, as well as denitrifying bacteria, archaea, and fungi. However, the vast majority of this research has been focused in temperate regions, and relatively little is known regarding the ecology of nitrogen-cycling microorganisms within tropical and subtropical ecosystems. Tropical forests are characterized by relatively high precipitation, low annual temperature fluctuation, high heterogeneity in plant diversity, large amounts of plant litter, and unique soil chemistry. For these reasons, regulation of the nitrogen cycle in tropical forests may be very different from that of temperate ecosystems. This is of great importance because of growing concerns regarding the effect of land use change and chronic-elevated nitrogen deposition on nitrogen-cycling processes in tropical forests. In the context of global change, it is crucial to understand how environmental factors and land use changes in tropical ecosystems influence the composition, abundance and activity of key players in the nitrogen cycle. In this review, we synthesize the limited currently available information regarding the microbial communities involved in nitrogen fixation, nitrification and denitrification, to provide deeper insight into the mechanisms regulating nitrogen cycling in tropical forest ecosystems. We also highlight the large gaps in our understanding of microbially mediated nitrogen processes in tropical forest soils and identify important areas for future research.

Organic carbon availability limiting microbial denitrification in the deep vadose zone

“…Sequencing analysis revealed that relative abundance of Pseudomonas and Bacillus responded quickly to the carbon addition, suggesting their growth were constrained by substrate starvation in soil, especially in deeper layers. A number of species in these genera have been reported as denitrifiers (Verbaendert et al ., ; Salles et al ., ; Pajares and Bohannan, ). The augmentation of the same taxa in AC and OC (Fig.…”

Of mammals and bacteria in a rainforest: Temporal dynamics of soil bacteria in response to simulated N pulse from mammalian urine

“…The limited number of studies on soil microbiology in terra firme forests (e.g. Barberán et al., ; Kim, Sparovek, Longo, De Melo, & Crowley, ; McGuire, Fierer, Bateman, Treseder, & Turner, ; Tripathi et al., ) calls for more basic work, particularly on establishing a link between community composition, taxon abundance and function, and rates and controls of biogeochemical transformations, which is particularly challenging in tropical forest soils (Pajares & Bohannan, ).…”

Remotely sensed canopy nitrogen correlates with nitrous oxide emissions in a lowland tropical rainforest

“…Heterogeneity in plant diversity, soil chemistry and fluctuating soil redox conditions make these associations especially challenging to parse in tropical soils (Pett‐Ridge et al. , Pajares and Bohannan ). Ammonia oxidation, the first step in autotrophic nitrification, is thought be driven largely by archaea (AOA) in the wet tropics, though studies vary in finding correlations between AOA abundance and process rates (Yao et al.…”

“…However, the few studies that have looked for relationships between denitrification gene abundance and gas emission rates within tropical ecosystems have generally not found clear relationships (Liu et al. , Pajares and Bohannan ).…”