2 results
Foliar nitrogen and phosphorus resorption and decomposition in the nitrogen-fixing tree Lysiloma microphyllum in primary and secondary seasonally tropical dry forests in Mexico
- Israel Cárdenas, Julio Campo
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- Journal:
- Journal of Tropical Ecology / Volume 23 / Issue 1 / January 2007
- Published online by Cambridge University Press:
- 12 January 2007, pp. 107-113
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The tree Lysiloma microphyllum (Fabaceae) dominates in the seasonally tropical dry forests of central Mexico. In this study foliar N and P concentrations (on leaf mass basis), foliar N and P resorption efficiency and proficiency, as well as the decomposition of senescent leaves of L. microphyllum were studied in primary and in regenerating, secondary seasonally tropical dry forests. Our study included an area of early successional forest (10 y old), with phosphorus-poor soils and comparatively abundant nitrogen, an area of late-successional forest (∼60 y old), in which soil P and N were comparatively abundant, and an area of primary forest, in which soil P was comparatively abundant and N was less abundant than in the secondary counterparts. N and P concentrations in mature leaves varied across forests, reflecting soil nutrient availability. Nitrogen concentration in senescent leaves did not change among sites, which led to very different patterns of N resorption. In contrast, P concentration in senescent leaves was lower in the early than in late-successional and primary forests, which resulted in similar patterns of resorption. Leaf decomposition increased from 70% mass loss in the first year in the early successional to ∼80% in the same period in late-successional and primary forests. The element loss during decomposition change across forests in the following order: for N, early successional = late-successional > primary forest, and for P, primary forest > late-successional > early successional forest. Overall, the pattern of variation in leaf chemistry and nutrient release on the forest floor among sites is consistent with soil nutrient availability along this sequence, while decomposition rate may be related with the P concentration in senescent leaves.
Nutrient cycling and plant–soil feedbacks along a precipitation gradient in lowland Panama
- Louis S. Santiago, Edward A. G. Schuur, Katia Silvera
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- Journal:
- Journal of Tropical Ecology / Volume 21 / Issue 4 / July 2005
- Published online by Cambridge University Press:
- 27 June 2005, pp. 461-470
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This study addresses patterns of nutrient dynamics on a precipitation gradient (1800–3500 mm y−1) in lowland tropical forest with heterogeneous soil parent material, high plant species diversity and large changes in species composition. Mean foliar concentrations of phosphorus, potassium, calcium and magnesium decreased with increasing precipitation, whereas foliar carbon:nitrogen increased with increasing precipitation. Mean foliar nitrogen:phosphorus varied from 16.4–23.8 suggesting that plant productivity at these sites is limited by phosphorus. Total soil nitrogen increased as a function of foliar litter lignin:nitrogen, whereas net nitrogen mineralization rates decreased with increasing lignin:N indicating that as litter quality decreases, more soil nitrogen is held in soil organic matter and the mineralization of that nitrogen is slower. Extractable phosphorus in soil was negatively correlated with foliar litter lignin:phosphorus, illustrating effects of litter quality on soil phosphorus availability. Overall, the results suggest that variation in plant community composition along this precipitation gradient is tightly coupled with soil nutrient cycling. Much of our understanding of effects of precipitation on nutrient cycling in tropical forest is based on precipitation gradients across montane forest in Hawaii, where species composition and soil parent material are constant. Our results suggest that variation in parent material or species composition may confound predictions developed in model island systems.
Resumen: Este estudio trata sobre los patrones de dinámica de nutrientes en un gradiente de precipitación (1800–3500 mm y−1) en un bosque tropical de tierras bajas con material parental heterogéneo, alta diversidad de especies de plantas, y un gran cambio en la composición de especies. Las concentraciones promedio de fósforo, potasio, calcio y magnesio disminuyen con un aumento en la precipitación, mientras que la proporción carbono:nitrógeno aumenta con un aumento en la precipitación. La proporción promedio de nitrógeno foliar:fósforo varía de 16.4 a 23.8, lo cual sugiere que estos sitios tienen limitaciones de fósforo. El nitrógeno total del suelo aumenta como una función de la proporción de lignina foliar de la hojarasca:nitrógeno, mientras que la tasa de mineralización del nitrógeno neto disminuye con un aumento de la proporción de lignina:nitrógeno, lo cual indica que mientras la calidad de la hojarasca disminuye, más nitrógeno del suelo es retenido en la materia orgánica y la mineralización de ese nitrógeno es más lenta. El fósforo extraíble está correlacionado negativamente con la proporción de lignina foliar de la hojarasca:fósforo, lo cual ilustra el efecto de la calidad de hojarasca en la disponibilidad de fósforo del suelo. En resumen, estos resultados sugieren que la variación en la composición de plantas de una comunidad a lo largo de este gradiente de precipitación tiene un efecto considerable en la retroalimentación de los ciclos nutricionales del suelo. Gran parte de nuestros conocimientos sobre el efecto de los gradientes de lluvia en ciclos nutricionales del suelo han sido basados en estudios de gradientes de precipitación de bosques de montaña en Hawaii, en donde tanto la composición de especies y el material parental del suelo son constantes. Nuestros resultados sugieren que la variación del material parental del suelo y la composición de especies pueden confundir las predicciones desarrolladas en sistemas modelos de islas.