RESUMO
In temperate climates, tree growth dormancy usually ensures the annual nature of tree rings, but in tropical environments, determination of annual periodicity can be more complex. The purposes of the work are as follows: (1) to generate a reliable tree-ring width chronology for Prioria copaifera Griseb. (Leguminoceae), a tropical tree species dwelling in the Atrato River floodplains, Colombia; (2) to assess the climate signal recorded by the tree-ring records; and (3) to validate the annual periodicity of the tree rings using independent methods. We used standard dendrochronological procedures to generate the P. copaifera tree-ring chronology. We used Pearson correlations to evaluate the relationship of the chronology with the meteorological records, climate regional indices, and gridded precipitation/sea surface temperature products. We also evaluated 24 high-precision 14C measurements spread over a range of preselected tree rings, with assigned calendar years by dendrochronological techniques, before and after the bomb spike in order to validate the annual nature of the tree rings. The tree-ring width chronology was statistically reliable, and it correlated significantly with local records of annual and October-December (OND) streamflow and precipitation across the upper river watershed (positive), and OND temperature (negative). It was also significantly related to the Oceanic Niño Index, Pacific Decadal Oscillation, and the Southern Oscillation Index, as well as sea surface temperatures over the Caribbean and the Pacific region. However, 14C high-precision measurements over the tree rings demonstrated offsets of up to 40 years that indicate that P. copaifera can produce more than one ring in certain years. Results derived from the strongest climate-growth relationship during the most recent years of the record suggest that the climatic signal reported may be due to the presence of annual rings in some of those trees in recent years. Our study alerts about the risk of applying dendrochronology in species with challenging anatomical features defining tree rings, commonly found in the tropics, without an independent validation of annual periodicity of tree rings. High-precision 14C measurements in multiple trees are a useful method to validate the identification of annual tree rings.
RESUMO
Resumen Variables oceanográficas en 33 estaciones en el Golfo Dulce, Costa Rica, entre 2009 y 2010 fueron analizadas a través de perfiles con CTD, donde la salinidad, la temperatura, sigma-T y las corrientes se estudiaron en la columna de agua. Disco Secchi y clorofila-a, fueron medidos a nivel superficial.. El objetivo fue estimar el área de dispersión de las plumas estuarinas a través del seguimiento de las variables físicas temperatura, salinidad y sigma-T. En agosto 2009, entre los ríos Coto Colorado y Esquinas disminuyeron la salinidad (<30) en un área de 250km2 aproximadamente, un 37% de la superficie total, creándose frentes termohalinos a lo largo de casi todo el golfo. Se documentó el efecto de El Niño Oscilación del Sur en enero 2010 durante su fase de acentuada intensidad. Las concentraciones de clorofila-a se correlacionaron en un 33.7% (P=0.05) con la transparencia del agua según el disco Secchi en la estación lluviosa. Se caracterizó el agua superficial del Golfo Dulce por tener salinidad <31.5 temperatura >27ºC y ocupar los cinco primeros metros de la columna de agua.
Abstract Oceanographic variables at 33 stations distributed in Golfo Dulce, Costa Rica, during the dry and rainy seasons between 2009 and 2010, were analyzed with CTD profiles, where salinity, temperature, sigma-T and currents were studied in the water column. Secchi depth and chlorophyll_a were measured in surface. The main objective was to estimate the catchment area and estuarine plume dispersion formed with river discharge. Between the rivers Esquinas and Coto Colorado, decreased salinity (<30) in an area of approximately 250km2, creating thermohaline fronts along most of the gulf. The El Niño South Oscillation, which was in the phase of heightened was documented. The chlorophyll concentrations correlated 33.7% with Secchi disc water transparency. The Golfo Dulce surface water was identified with salinity <31.5 and temperature >27°C (April to December). This research contributes to the knowledge of the oceanography of the Golfo Dulce and the feedback we receive from fluvial origin, claiming form providing inputs for the potential creation of a major new marine protected area system covering entire Golfo Dulce area and, ideally, the surrounding river systems that feed it. Rev. Biol. Trop. 63 (2): 161-181. Epub 2015 June 01.
