Initial nitrogen enrichment conditions determines variations in nitrogen substrate utilization by heterotrophic bacterial isolates

Background The nitrogen (N) cycle consists of complex microbe-mediated transformations driven by a variety of factors, including diversity and concentrations of N compounds. In this study, we examined taxonomic diversity and N substrate utilization by heterotrophic bacteria isolated from streams under complex and simple N-enrichment conditions. Results Diversity estimates differed among isolates from the enrichments, but no significant composition were detected. Substrate utilization and substrate range of bacterial assemblages differed within and among enrichments types, and not simply between simple and complex N-enrichments. Conclusions N substrate use patterns differed between isolates from some complex and simple N-enrichments while others were unexpectedly similar. Taxonomic composition of isolates did not differ among enrichments and was unrelated to N use suggesting strong functional redundancy. Ultimately, our results imply that the available N pool influences physiology and selects for bacteria with various abilities that are unrelated to their taxonomic affiliation. Electronic supplementary material The online version of this article (doi:10.1186/s12866-017-0993-7) contains supplementary material, which is available to authorized users

Toward a Coordinated Understanding of Hydro-Biogeochemical Root Functions in Tropical Forests for Application in Vegetation Models

Tropical forest root characteristics and resource acquisition strategies are underrepresented in vegetation and global models, hampering the prediction of forest–climate feedbacks for these carbon-rich ecosystems. Lowland tropical forests often have globally unique combinations of high taxonomic and functional biodiversity, rainfall seasonality, and strongly weathered infertile soils, giving rise to distinct patterns in root traits and functions compared with higher latitude ecosystems. We provide a roadmap for integrating recent advances in our understanding of tropical forest belowground function into vegetation models, focusing on water and nutrient acquisition. We offer comparisons of recent advances in empirical and model understanding of root characteristics that represent important functional processes in tropical forests. We focus on: (1) fine-root strategies for soil resource exploration, (2) coupling and trade-offs in fine-root water vs nutrient acquisition, and (3) aboveground–belowground linkages in plant resource acquisition and use. We suggest avenues for representing these extremely diverse plant communities in computationally manageable and ecologically meaningful groups in models for linked aboveground–belowground hydro-nutrient functions. Tropical forests are undergoing warming, shifting rainfall regimes, and exacerbation of soil nutrient scarcity caused by elevated atmospheric CO2. The accurate model representation of tropical forest functions is crucial for understanding the interactions of this biome with the climate

Rapid responses of root traits and productivity to phosphorus and cation additions in a tropical lowland forest in Amazonia

• Soil nutrient availability can strongly affect root traits. In tropical forests, phosphorus (P) is often considered the main limiting nutrient for plants. However, support for the P paradigm is limited, and N and cations might also control tropical forests functioning. • We used a large‐scale experiment to determine how the factorial addition of nitrogen (N), P and cations affected root productivity and traits related to nutrient acquisition strategies (morphological traits, phosphatase activity, arbuscular mycorrhizal colonisation and nutrient contents) in a primary rainforest growing on low‐fertility soils in Central Amazonia after one year of fertilisation. • Multiple root traits and productivity were affected. Phosphorus additions increased annual root productivity and root diameter, but decreased root phosphatase activity. Cation additions increased root productivity at certain times of year, also increasing root diameter and mycorrhizal colonisation. P and cation additions increased their element concentrations in root tissues. No responses were detected with N addition. • Here we show that rock‐derived nutrients determine root functioning in low‐fertility Amazonian soils, demonstrating not only the hypothesised importance of P, but also highlighting the role of cations. The changes in fine root traits and productivity indicate that even slow‐growing tropical rainforests can respond rapidly to changes in resource availability

Impacto de la extracción de madera en la estructura florística y la regeneración de un bosque de cativo (Prioria copaifera Griseb.) en la Costa Caribe de Costa Rica

Tesis (magister scientiae en biología)--Universidad de Costa Rica. Sistema de Estudios de Posgrado, 2003.UCR::Vicerrectoría de Investigación::Sistema de Estudios de Posgrado::Ciencias Básicas::Maestría Académica en Biologí

Impactos de la extracción en la estructura y la dinámica de plántulas en un bosque tropical dominado por Prioria copaifera (Fabaceae), (Talamanca, Costa Rica)

The factors that determine the existence of tropical forests dominated by a single species (monodominated forests) have been the subject of debate for a long time. It has been hypothesized that the low frequency of disturbances in monodominated forests and the tolerance to shade of the monodominant species are two important factors explaining the prolonged dominance of a single species. We determined the role of these two factors by examining the effects of logging activities on the floristic composition and seedling dynamics in a Prioria copaifera dominated forest in Southeastern Costa Rica. We determined the floristic composition for trees ≥2.5cm DBH and the associated recruitment, survival and mortality of tree canopy seedlings in two sites logged two (L-02) and 12 years (L-12) prior to sampling and an unlogged forest (ULF). Our results showed that L-02 stands had lower species richness (25 species) than the L-12 and ULF stands (49 and 46 species, respectively). As expected, we found significant logging effects on the canopy structure of the altered forests, particularly when comparing the L-02 and the ULF stands. Seedling density was higher in ULF (0.96 seedlings/m2) than in the L-02and L-12 stands (0.322 and 0.466 seedlings/m2, respectively). However, seedling mortality was higher in the ULF stands (54%) than in the L-02 (26%) and L-12 (15%) stands. P. macroloba in L-02 was the only species with abundant regeneration under P. copaifera in L-02 stand, where it accounted for 35% of the seedlings. Despite the reduction in seedling abundance observed after logging, P. copaifera seems to maintain large seedling populations in these forests, suggesting that this species maintains its dominance after logging disturbances. Our findings challenge the hypothesis that the regeneration of monodominant species is not likely to occur under heavily disturbed canopy conditions.La determinación de los factores responsables de la existencia de bosques tropicales dominados por una sola especie (bosques monodominados) ha sido motivo de debate por largo tiempo. Se ha propuesto que la baja frecuencia de alteraciones en esos bosques y la tolerancia a la sombra de las plántulas de la especie monodominante son dos de los factores que contribuyen a explicar la prolongada dominancia de una sola especie en estos bosques. Se estudió el rol de estos dos factores evaluando el efecto de la extracción de madera sobre la composición florística y la supervivencia y crecimiento de plántulas en un bosque dominado por Prioria copaifera en la región sureste de Costa Rica. Para ello se determinó la composición florística de los árboles con un diámetro a la altura de pecho (DAP) ≥2.5cm y el reclutamiento, supervivencia y mortalidad de las plántulas de especies arbóreas en sitios donde se extrajo madera dos (L-02) y doce años (L-12) antes de este estudio y un sitio del que nunca se ha extraído madera (ULF). Nuestros resultados muestran que los bosques L-02 tienen una riqueza de especies menor (25 especies) que los bosques L-12 y ULF (49 y 46 especies, respectivamente). Como era de esperar, la extracción de madera tuvo efectos significativos en la estructura del dosel del bosque, particularmente al comparar los bosques L-02 y ULF. La densidad de plántulas fue mayor en bosques ULF (0.96 plántulas/m2) que en L-02 y L-12 (0.322 and 0.466 plántulas/m2, respectivamente). Sin embargo, la mortalidad de plántulas fue mayor en ULF (54%) que en L-02 (26%) y L-12 (15%). Pentachletra macroloba fue la única especie que mostró abundante regeneración bajo P. copaifera en parcelas L-02, representando el 35% las plántulas encontradas. A pesar de la reducción de la abundancia de plántulas observada después de la extracción de madera, P. copaifera parece capaz de mantener grandes poblaciones de plántulas en estos bosques. Estos resultados sugieren que P. copaifera puede mantener su dominancia después de las alteraciones causadas por la extracción de madera. Nuestros resultados no apoyan la hipótesis de que la regeneración de las especies monodominates es menos probable cuando el dosel del bosque sufre fuertes alteraciones

Logging impacts on forest structure and seedling dynamics in a Prioria copaifera (Fabaceae) dominated tropical rain forest (Talamanca, Costa Rica)

The factors that determine the existence of tropical forests dominated by a single species (monodominated forests) have been the subject of debate for a long time. It has been hypothesized that the low frequency of disturbances in monodominated forests and the tolerance to shade of the monodominant species are two important factors explaining the prolonged dominance of a single species. We determined the role of these two factors by examining the effects of logging activities on the floristic composition and seedling dynamics in a Prioria copaifera dominated forest in Southeastern Costa Rica. We determined the floristic composition for trees ≥2.5cm DBH and the associated recruitment, survival and mortality of tree canopy seedlings in two sites logged two (L-02) and 12 years (L-12) prior to sampling and an unlogged forest (ULF). Our results showed that L-02 stands had lower species richness (25 species) than the L-12 and ULF stands (49 and 46 species, respectively). As expected, we found significant logging effects on the canopy structure of the altered forests, particularly when comparing the L-02 and the ULF stands. Seedling density was higher in ULF (0.96 seedlings/m²) than in the L-02and L-12 stands (0.322 and 0.466 seedlings/m², respectively). However, seedling mortality was higher in the ULF stands (54%) than in the L-02 (26%) and L-12 (15%) stands. P. macroloba in L-02 was the only species with abundant regeneration under P. copaifera in L-02 stand, where it accounted for 35% of the seedlings. Despite the reduction in seedling abundance observed after logging, P. copaifera seems to maintain large seedling populations in these forests, suggesting that this species maintains its dominance after logging disturbances. Our findings challenge the hypothesis that the regeneration of monodominant species is not likely to occur under heavily disturbed canopy conditions. Rev. Biol. Trop. 62 (1): 347-357. Epub 2014 March 01