Plant functioning in response to the environment is an important issue for vegetation reassembly of degraded lands because of both low and excessive sunlight influence the performance of young plants. However, how shade-tolerant tree species deal with excess of light energy remains unclear due to the contrasting results among studies and the subjective classifications of species shade tolerance. From a quantitative classification of shade tolerance of 12 tropical tree species planted in the field under contrasting light conditions, we hypothesized that shade-tolerant species are capable of effective long-term acclimation to high-light conditions. Plant size and survival of species were measured at the beginning and 38 months after planting. We also measured functional traits associated with carbon economy and non-photochemical energy dissipation. Under high-light condition, more light-demanding species showed higher growth rates associated with higher values of functional traits that improve the CO₂ assimilation capacity. By contrast, more shade-tolerant species showed higher survival that was associated with higher values of qN, leaf K contents and leaf thickness. The concomitant increase in these traits, as well as their greater plasticity to light in WUE_i, F_v/F_m and qN, confers on these species strong photoprotection to avoid high-light stress and to persist under open field conditions. The results challenge the common assumption that only fast-growing and light-demanding tree species are suitable for vegetation reassembly in full sunlight conditions and to improve the environmental conditions for other species.

Euterpe oleracea Mart. (Arecaceae) es una palma cespitosa y dominante en bosques de zonas inundablesde la cuenca del río Atrato, Colombia. Es considerada de importancia económica por el palmito que se extrae deella y por los múltiples productos que se derivan de sus frutos. Se estudió la fenología reproductiva de Euterpeoleracea en 2 comunidades vegetales: murrapal mixto, donde E. oleracea ocurre junto a otras especies, y murrapalpuro, dominado casi en su totalidad por E. oleracea. Los registros fenológicos se llevaron a cabo en 2 periodos:entre octubre de 1999 y diciembre de 2001, en ambos tipos de bosque; y entre octubre de 2006 y mayo de 2009,sólo en el murrapal mixto. La fenología reproductiva de Euterpe oleracea respondió a un patrón anual en ambosecosistemas; sin embargo, las épocas de mayor producción de flores y frutos no coincidieron entre ellos. Se encontróuna correlación significativa entre la precipitación y las fenofases, frutos verdes y frutos maduros en el murrapal puro;lo que sugiere un efecto de la inundabilidad sobre la producción temporal de flores y frutos. En el murrapal mixto nose halló relación significativa entre la pluviosidad y las fenofases reproductivas, probablemente debido a que en estaposición topográfica la inundación durante la estación lluviosa no fue tan severa y, por tanto, no alcanzó a cubrir losneumatóforos de las palmas.

Despite the progress to understand drought tolerance worldwide, the response of urban trees to the increased frequency and severity of droughts, particularly in tropical regions, remains unclear. Such an evaluation is essential for predicting future urban forest dynamics. The leaf turgor loss point (π_TLP), leaf safety margins (SMs) and their relationship with functional traits were measured in ten native tree species during wet and dry seasons in a tropical urban environment. We detected interspecific variation in tree responses related to desiccation tolerance and desiccation avoidance as strategies to resist drought. Desiccation avoidance was linked to lower adjustment of midday water potentials and water-conservative traits such as high wood density, low specific leaf area (SLA), and high leaf dry matter content, while species with more negative π_TLP maintained stomatal conductance and growth despite decreasing leaf water potentials. Although the differences between predawn and midday potentials during the dry season suggest that severe drought does not occur, some species showed negative safety margins. This indicates that while some urban trees can tolerate or avoid current dry periods, continued climate change may push certain species beyond their safe operating range, making species selection for urban planning increasingly critical.