Search

Resorption is the active withdrawal of nutrients before leaf abscission. This mechanism represents an important strategy to maintain efficient nutrient cycling; however, resorption is poorly characterized in old‐growth tropical forests growing in nutrient‐poor soils. We investigated nutrient resorption from leaves in 39 tree species in two tropical forests on the Guiana Shield, French Guiana, to investigate whether resorption efficiencies varied with soil nutrient, seasonality, and species traits. The stocks of P in leaves, litter, and soil were low at both sites, indicating potential P limitation of the forests. Accordingly, mean resorption efficiencies were higher for P (35.9%) and potassium (K; 44.6%) than for nitrogen (N; 10.3%). K resorption was higher in the wet (70.2%) than in the dry (41.7%) season. P resorption increased slightly with decreasing total soil P; and N and P resorptions were positively related to their foliar concentrations. We conclude that nutrient resorption is a key plant nutrition strategy in these old‐growth tropical forests, that trees with high foliar nutrient concentration reabsorb more nutrient, and that nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level., Resorption is a key plant nutrition strategy in old‐growth tropical forests. Trees with high foliar nutrient concentration reabsorb more nutrients. Nutrients resorption in leaves, except P, are quite decoupled from nutrients in the soil. Seasonality and biochemical limitation played a role in the resorption of nutrients in leaves, but species‐specific requirements obscured general tendencies at stand and ecosystem level.

Para este estudio se han analizado las variables fenológicas, morfológicas y ecofisiológicas de 4 especies de Quercus sp que se encuentran en el Paisaje Terrestre Protegido Miraflor de Miraflor-Moropotente (Estelí, Nicaragua), en invierno (estación seca) y en verano (estación húmeda). Cada especie presenta un diferente rango altitudinal de distribución, y para cada especie se han elegido dos poblaciones, ubicadas respectivamente en la zona baja y en la zona alta de dicha área. Todos los parámetros analizados varían significativamente entre especies, poblaciones y estaciones, con la especie como principal factor discriminante. En especifico, las especies que ocupan altitudes menores presentan estrategias de adaptación típicas de regímenes hídricos más escasos, como la caída de hojas más prolongada en el tiempo y menores densidades estomáticas; este patrón se observa también entre poblaciones de altitudes diferentes dentro de cada especie, aunque menos marcado. Se puede concluir que los factores climáticos relacionados con la altitud afectan significativamente las respuestas de estos árboles típicos del trópico seco, y que dichas respuestas varían entre especies como resultado de diferentes estrategias de adaptación. Estas estrategias están a la base de la estructura, composición y biodiversidad de los bosques del trópico seco, e influencian los patrones de distribución de las especies. La mejor comprensión de dichas estrategias es una herramienta crucial para la gestión forestal de estos delicados ecosistemas en el marco del cambio climático en curso.

This chapter analyzes the post-fire regeneration of Mediterranean broadleaved forests, the factors that may constrain this process and the best alternatives to improve the structure and dynamics of these forests after fire. Most Mediterranean broadleaved species share in common their ability to resprout from a protected bud bank after disturbances such as fire. Yet, this ability may vary depending on the species considered, the intensity and recurrence of fire events, the quality of the site and some individual characteristics (e.g. plant size). Even though resprouting after fire assures a rapid recovery of the vegetation cover and other crucial processes and ecosystem services, these young and dense forests with multi-stemmed resprouted individuals may not fit the modern socioeconomic demands and may even become very sensitive to the spread of new fires. Therefore, a selective thinning of resprouts, retaining the larger and dominant ones, has been recommended. This management alternative has been shown to increase growth rates of retained resprouts, to raise the forest canopy and to encourage sexual reproduction. Nevertheless, attention must be paid to the new wave of resprouts that may appear after thinning. In this chapter we analyze the main constrains that affect the natural regeneration of Mediterranean broadleaved forests after fire and the best alternatives to manage natural regeneration arisen through resprouting in these areas.