Primary Succession on a Hawaiian Dryland Chronosequence.

We used measurements from airborne imaging spectroscopy and LiDAR to quantify the biophysical structure and composition of vegetation on a dryland substrate age gradient in Hawaii. Both vertical stature and species composition changed during primary succession, and reveal a progressive increase in vertical stature on younger substrates followed by a collapse on Pleistocene-aged flows. Tall-stature Metrosideros polymorpha woodlands dominated on the youngest substrates (hundreds of years), and were replaced by the tall-stature endemic tree species Myoporum sandwicense and Sophora chrysophylla on intermediate-aged flows (thousands of years). The oldest substrates (tens of thousands of years) were dominated by the short-stature native shrub Dodonaea viscosa and endemic grass Eragrostis atropioides. We excavated 18 macroscopic charcoal fragments from Pleistocene-aged substrates. Mean radiocarbon age was 2,002 years and ranged from < 200 to 7,730. Genus identities from four fragments indicate that Osteomeles spp. or M. polymorpha once occupied the Pleistocene-aged substrates, but neither of these species is found there today. These findings indicate the existence of fires before humans are known to have occupied the Hawaiian archipelago, and demonstrate that a collapse in vertical stature is prevalent on the oldest substrates. This work contributes to our understanding of prehistoric fires in shaping the trajectory of primary succession in Hawaiian drylands.

La modelización de los flujos volcánicos para la evacuación de riesgos y la planificación espacial en Hawai'i

La evacuación de los riesgos causados por el volcán Mauna Loa se ha basado en la modelización de los niveles de riesgo y en el seguimiento de las variables físicas precursoras de una erupción. La aplicación de los estudios a la planificación del territorio no ha sido completa por la falta de un modelo territorial que ingrese el factor riesgo y por la carencia de una perspectiva sobre la relacion entre le origen de los episodios y espacios habilitados, modelización que lleva a cabo analizando la disposición espacial de las coladas por medio de la geometría del terreno (AU)