Please use this identifier to cite or link to this item: http://hdl.handle.net/2445/110624
Title: Impacts of climate and drought on tree radial growth in Neotropical dry forests: Scaling up from short to long time-scales = Impactos del clima y las sequías en el crecimiento radial de los árboles en los bosques secos Neotropicales: Evaluación de sus efectos a diferentes escalas temporales
Author: Chaparro Mendivelso, Hooz Angela
Director: Camarero Martínez, Jesús Julio
Zuidema, Pieter A.
Gutiérrez Merino, Emilia
Keywords: Canvis climàtics
Sequeres
Arbres
Boscos
Climatic changes
Droughts
Trees
Forests
Tropics
Issue Date: 13-Dec-2016
Publisher: Universitat de Barcelona
Abstract: [eng] This thesis analyzed the dynamics of tree radial growth at different time-scales in relation to climate and drought in two tropical dry forests (TDFs) from Colombia (Tuluá) and Bolivia (INPA). The specific objectives were: (i) To assess intra-annual patterns of radial growth (radial- increment dynamics and xylogenesis) in ten coexisting tree species from Tuluá and INPA and determine their relationship with climate and leaf phenology. (ii) To analyze the effects of climate and drought on long-term radial growth at different time-scales using dendrochronology in seven coexisting deciduous tree species from INPA. (iii) To evaluate the long-term radial growth responses to changes in climate water balance and determine their relationship with sapwood density in seven coexisting deciduous tree species from INPA. At intra-annual scales it was found that: (i) cambium reactivation and xylem growth of tree species occurred during the wet season, reflecting the influence of high precipitation and a positive water balance on the development of new xylem cells. (ii) In the semi-deciduous tree species from Tuluá the xylem growth period overlapped with the wet season, whereas, in the deciduous tree species from INPA, the growth period started at the mid wet season, when the tree crowns were fully developed. (iii) Temperature, as a determinant factor in the hourly fluctuations of both the vapor pressure deficit (VPD) and the evapotranspiration rate, could exert a huge influence on tree radial growth dynamics during the growing season. In Tuluá, the growing season was particularly associated with low temperatures and hence low VPD, while in INPA the growing season was related to high temperatures and VPD. Nevertheless, the high temperatures registered throughout the day at both TDFs negatively affected radial increment at hourly scales. Tree species could face the adverse dry conditions by restricting growth to periods of the day when temperatures are low. (iv) Stem shrinkage and swelling occurred at hourly to daily scales in all tree species, and most INPA tree species registered strong reversible shrinkage at monthly scales. Particularly, the climate controls on radial-increment dynamics varied between daily and monthly scales. At daily scales, there was a positive effect of high precipitation and positive water balance and a negative effect of VPD on the increment phase, while at monthly scales the precipitation was the main variable affecting radial increment positively. At inter-annual scales it was found that: (i) The tree radial growth showed a positive relationship with precipitation and climate water balance and a negative association with temperature, indicating that the tree species studied share high common growth variability in response to local climate. Nevertheless, the strongest response of growth to climate was species-specific, indicating that there was a differential sensitivity among tree species to these climate variables. (ii) The radial growth of all tree species responded positively to water balance during the wet season, but such responses differed among species as a function of their stem sapwood density. Specifically, sapwood density was negatively related to growth variability explained by water balance. Tree species with low-density wood and high production of sapwood were the most sensitive to water balance, whereas species with the opposite characteristics were the least sensitive ones. (iii) Tree species tolerated short-term droughts while they were particularly sensitive to long-lasting droughts. This indicates that tree species from the INPA site are predominantly sensitive in terms of growth reduction to long-lasting droughts. The most temperature-sensitive tree species, also showed the highest growth sensitivity to long-lasting droughts. In contrast, growth of the tree species with the lowest sensitivity to water balance, did not respond to long-term drought variability.
[spa] Esta tesis evaluó la dinámica del crecimiento radial a diferentes escalas temporales y determinó su relación con el clima y la sequía en dos bosques secos tropicales de Colombia (Tuluá) y Bolivia (INPA). A escalas intra-anuales se encontró que: (i) la reactivación del cambium y el crecimiento del xilema ocurre durante la época húmeda del año en ambos bosques. Esto refleja la influencia de las altas precipitaciones y los valores positivos del balance hídrico atmosférico en el desarrollo de las nuevas células del xilema. (ii) El período de crecimiento en Tuluá estuvo asociado a temperaturas bajas y, por ende, a un déficit de presión del vapor (DPV) bajo, mientras que en INPA la estación de crecimiento estuvo asociada a valores altos de temperatura y DPV. Sin embargo, en ambos sitios de estudio, las temperaturas altas registradas a lo largo del día afectaron negativamente el incremento radial a escalas horarias. Las especies pueden hacer frente a estas condiciones adversas, por ejemplo, restringiendo el crecimiento a períodos del día que registren temperaturas bajas, ya que la pérdida de agua asociada a la evapotranspiración también sería baja. A escalas inter-anuales se determinó que: (i) el crecimiento radial de todas las especies de INPA presentó una asociación positiva con la precipitación y el balance hídrico atmosférico y una relación negativa con la temperatura. Esto indica que todas las especies comparten una señal común de la variabilidad del crecimiento en respuesta al clima local. No obstante, la fuerza de la respuesta fue especie-específica. Esto indica que existe una sensibilidad diferencial entre las especies al clima. (ii) El crecimiento radial de todas las especies de INPA respondió positivamente al balance hídrico atmosférico durante la estación húmeda, pero esa respuesta fue diferente entre las especies en función de la densidad de la albura. La densidad de la albura fue negativamente relacionada a la variabilidad del crecimiento explicada por el balance hídrico. (iv) Las especies de INPA fueron resilientes a las sequías de corto plazo (estación seca anual), mientras que el crecimiento fue particularmente sensible a las sequías de larga duración (sequías multi-anuales), excepto en las especies con alta densidad de la albura.
URI: http://hdl.handle.net/2445/110624
Appears in Collections:Tesis Doctorals - Facultat - Biologia

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