Biological nitrogen fixation in secondary regrowth and mature rainforest of central Amazonia

Gehring, Christoph; Vlek, Paul L. G.; Souza, Luiz Augusto Gomes de; Denich, Manfred

doi:10.1016/j.agee.2005.06.009

Cited by 105 publications

(106 citation statements)

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“…Values of nonfixing species in Caatinga ( 7 a 9‰) are high (Freitas et al, 2010a) compared to those of other Brazilian ecosystems: cerrado, <2‰ (Sprent et al, 1996;Bustamante et al, 2004); and Amazon forest, <5,25‰ (Gehring et al, 2005). But they are similar to those found by Schulze et al (1991) in semiarid areas of Namibia (7.38‰).…”

Section: Biological Nitrogen Fixationsupporting

confidence: 54%

Biogeochemical cycling in terrestrial ecosystems of the Caatinga Biome

et al. 2012

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The biogeochemical cycles of C, N, P and water, the impacts of land use in the stocks and flows of these elements and how they can affect the structure and functioning of Caatinga were reviewed. About half of this biome is still covered by native secondary vegetation. Soils are deficient in nutrients, especially N and P. Average concentrations of total soil P and C in the top layer (0-20 cm) and 21 to 26 kg N ha -1 year -1 in mature and secondary Caatinga, respectively. The main processes responsible for nutrient and water losses are fire, soil erosion, runoff and harvest of crops and animal products. Projected climate changes in the future point to higher temperatures and rainfall decreases. In face of the high intrinsic variability, actions to increase sustainability should improve resilience and stability of the ecosystems. Land use systems based on perennial species, as opposed to annual species, may be more stable and resilient, thus more adequate to face future potential increases in climate variability. Long-term studies to investigate the potential of the native biodiversity or adapted exotic species to design sustainable land use systems should be encouraged.Keywords: tropical dry forest, nutrient fluxes, carbon, nitrogen, phosphorus. Ciclagem biogeoquímica em ecossistemas terrestres do Bioma Caatinga ResumoOs ciclos biogeoquímicos de C, N, P e água, os impactos das mudanças do uso da terra nos estoques e fluxos destes elementos e como estas mudanças podem afetar a estrutura e o funcionamento da Caatinga foram revisados. Cerca da metade desse Bioma ainda é coberta por vegetação nativa secundária. Os solos são deficientes em nutrientes, principalmente N e P. A concentração média, na camada superficial (0-20 cm), de P total é 196 mg kg , e a biomassa radicular entre 3 a 12 Mg ha -1 . As produtividades e acumulações anuais de biomassa nos diferentes usos da terra variam de 1 a 7 Mg ha -1 . A fixação biológica de N 2 atmosférico é estimada em 3 a 11 kg N ha -1 ano -1 e 21 a 26 kg N ha -1 ano -1 em Caatinga madura e em regeneração, respectivamente. Os principais processos de perda de nutrientes e água são queimadas, erosão do solo, escoamento e colheita de cultivos e produtos animais. As mudanças climáticas projetadas indicam maiores temperaturas e menores precipitações. Considerando a alta variabilidade intrínseca, ações para aumentar a sustentabilidade deveriam melhorar a resiliência e a estabilidade dos ecossistemas. Sistemas de uso da terra baseados em espécies perenes, em contraposição a anuais, devem ser mais estáveis e resilientes, portanto mais adequados para enfrentar os potenciais aumentos na variabilidade climática. Estudos de longa duração para avaliar o potencial da biodiversidade nativa ou de exóticas adaptadas no delineamento de sistemas de uso sustentáveis deveriam ser encorajados.Palavras-chave: floresta seca tropical, fluxo de nutrientes, carbono, nitrogênio, fósforo.

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Section: Biological Nitrogen Fixationsupporting

confidence: 54%

Biogeochemical cycling in terrestrial ecosystems of the Caatinga Biome

et al. 2012

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“…Second, empirical data describing natural N fixation rates in tropical forests are rare, and large-scale estimates of tropical N fixation are based on a handful of instantaneous, plotscale estimates extrapolated to the biome scale. Third, while N fixation is presumed to be high in tropical rain forests, a number of recent studies have questioned this conclusion (e.g., Gehring et al 2005). Fourth, since the potential for substantial natural N fixation appears high in lowland tropical forests, further constraining N inputs via N fixation is a necessary next step in evaluating how human activities have altered the global N cycle.…”

Section: Introductionmentioning

confidence: 99%

“…High background concentrations of N 2 in the atmosphere make it impossible-at least using current technology-to detect small changes in N 2 concentration resulting from N fixation. As a result, rates are most frequently assessed using indirect approaches (e.g., 15 N and ARA) that may or may not provide accurate estimates (Warembourg 1993, Gehring et al 2005. Second, symbiotic BNF is both spatially and temporally heterogeneous, owing to patchy distributions of potential N-fixers (ter Steege et al 2006) and phylogenetic constraints to nodulation and N fixation (Sprent 2005).…”

Section: Introductionmentioning

confidence: 99%

Using indirect methods to constrain symbiotic nitrogen fixation rates: a case study from an Amazonian rain forest

et al. 2009

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Human activities have profoundly altered the global nitrogen (N) cycle. Increases in anthropogenic N have had multiple effects on the atmosphere, on terrestrial, freshwater and marine ecosystems, and even on human health. Unfortunately, methodological limitations challenge our ability to directly measure natural N inputs via biological N fixation (BNF)-the largest natural source of new N to ecosystems. This confounds efforts to quantify the extent of anthropogenic perturbation to the N cycle. To address this gap, we used a pair of indirect methods-analytical modeling and N balance-to generate independent estimates of BNF in a presumed hotspot of N fixation, a tropical rain forest site in central Rondônia in the Brazilian Amazon Basin. Our objectives were to attempt to constrain symbiotic N fixation rates in this site using indirect methods, and to assess strengths and weaknesses of this approach by looking for areas of convergence and disagreement between the estimates. This approach yielded two remarkably similar estimates of N fixation. However, when compared to a previously published bottom-up estimate, our analysis indicated much lower N inputs via symbiotic BNF in the Rondônia site than has been suggested for the tropics as a whole. This discrepancy may reflect errors associated with extrapolating bottom-up fluxes from plot-scale measures, those resulting from the indirect analyses, and/or the relatively low abundance of legumes at the Rondônia site. While indirect methods have some limitations, we suggest that until the technological challenges of directly measuring N fixation are overcome, integrated approaches that employ a combination of

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“…Cuando el bosque es talado y quemado para instalar pastizales (Uhl & Jordan 1984, Matson et al 1987, Antón 1999, mueren muchos de los microorganismos presentes y parte del nitróge-no se volatiliza durante la quema (Holsher et al 1997, Mackensen et al 1999. En ausencia de fuentes externas importantes de nitrógeno la fijación de nitrógeno se convierte en una de las principales rutas para la recuperación del suelo (Gehring et al 2005), por lo cual bacterias con capacidad para fijar el nitrógeno de la atmós-fera pueden aumentar sus poblaciones al tener una ventaja competitiva y ocupar espacios que antes eran ocupados por otros grupos bacterianos que desaparecen (Peña-Venegas 2004, Cardona 2004). …”

Section: Discussionunclassified