ABSTRACT
The science of tropical dendrochronology is now emerging in regions where tree-ring dating had previously not been considered possible. Here, we combine wood anatomical microsectioning techniques and radiocarbon analysis to produce the first tree-ring chronology with verified annual periodicity for a new dendrochronological species, Neltuma alba (commonly known as "algarrobo blanco") in the tropical Andes of Bolivia. First, we generated a preliminary chronology composed of six trees using traditional dendrochronological methods (i.e., cross-dating). We then measured the 14C content on nine selected tree rings from two samples and compared them with the Southern Hemisphere (SH) atmospheric 14C curves, covering the period of the bomb 14C peak. We find consistent offsets of 5 and 12 years, respectively, in the calendar dates initially assigned, indicating that several tree rings were missing in the sequence. In order to identify the tree-ring boundaries of the unidentified rings we investigated further by analyzing stem wood microsections to examine anatomical characteristics. These anatomical microsections revealed the presence of very narrow terminal parenchyma defining several tree-ring boundaries within the sapwood, which was not visible in sanded samples under a stereomicroscope. Such newly identified tree rings were consistent with the offsets shown by the radiocarbon analysis and allowed us to correct the calendar dates of the initial chronology. Additional radiocarbon measurements over a new batch of rings of the corrected dated samples resulted in a perfect match between the dendrochronological calendar years and the 14C dating, which is based on good agreement between the tree-ring 14C content and the SH 14C curves. Correlations with prior season precipitation and temperature reveal a strong legacy effect of climate conditions prior to the current Neltuma alba growing season. Overall, our study highlights much potential to complement traditional dendrochronology in tree species with challenging tree-ring boundaries with wood anatomical methods and 14C analyses. Taken together, these approaches confirm that Neltuma alba can be accurately dated and thereby used in climatic and ecological studies in tropical and subtropical South America.
ABSTRACT
Resumen El origen geográfico de la semilla ejerce un control genético sobre los caracteres de comportamiento de las plantas por lo cual su selección es una herramienta útil para lograr la máxima adaptación de la especie al medio. En este sentido, la caracterización de materiales de diferentes procedencias brinda información para la elección de las fuentes de semilla utilizables en programas de mejora, así como en proyectos de forestación y/o repoblación. El presente trabajo tuvo como objetivo establecer el efecto de la procedencia sobre las variables morfológicas que constituyen parámetros de calidad en plantines de Prosopis alba provenientes de tres áreas geográficas. Se midieron variables morfológicas de las plantas hasta los 150 días posteriores a la siembra. El efecto de la procedencia resultó significativo para la mayoría de las variables medidas: altura de las plantas y diámetro a la altura del cuello (al menos durante los primeros 3 meses de viverización), volumen de raíz, peso foliar específico y área foliar específica. Así mismo algunos de los índices y cocientes morfológicos considerados como variables para determinar la calidad de plantas resultan afectados por el origen geográfico del material: relación longitud parte aérea/parte radical, coeficiente de esbeltez e índice de esbeltez. Los resultados permiten afirmar que en P. alba la procedencia influye sobre la morfología de las plantas y determina la existencia de dos grupos diferentes: por un lado, las procedencias santiagueña y chaqueña y, por otro, la procedencia Salta Norte.
Abstract Seed provenance has a genetic control over the behavioral characteristics of plants, whereby selection is an useful tool to achieve the maximum adaptation of the species to the environment. In this sense, different provenance materials characterization provides information for choosing seed sources used in breeding programs, as well as afforestation and/or reforestation projects. The aim of this work was established provenance´s effect on morphological variables that constitute quality parameters in Prosopis alba seedlings from three geographic areas. Morphological plants´ variables were measured up to 150 days after planting. Provenance effect was significant for most of measured variables: plant´s height, neck diameter (at least during the first 3 months of nursery), root volume, specific leaf weight and specific leaf area. Likewise, some of the morphological indices and quotients considered variables to determine plants´ quality are affected by material´s geographical origin: shoot length/ root length proportion, slenderness coefficient and index. Results allow affirming P. alba´s provenance influences plants´ morphology determining the existence of two different groups: on one hand Santiago del Estero and Chaco provenances, and on the other, Salta Norte origin. Rev. Biol. Trop. 66(2): 593-604. Epub 2018 June 01.
