THE IMPACT OF THE LAS CONCHAS FIRE ON THE DISSOLVED ORGANIC MATTER OF SURFACE WATERS AS DETERMINED BY ITS OPTICAL PROPERTIES AND BIOMASS MEASUREMENTS

The properties of dissolved organic matter (DOM) are known to vary in both space and time. Some alpine watershed studies have demonstrated a cycle in DOM of surface waters in which concentrations peak in early summer and decrease throughout fall. The cycle is attributable to weather patterns that increase input of soil organic matter (snowmelt, rainstorm events) and an increase in biological activity that, thanks to more favorable conditions, consumes and transforms the DOM. Grab samples were collected in three streams of the Valles Caldera National Preserve in order to measure DOM quantity and its characteristics and determine what effect the surroundings have on the several parameters. Samples were collected on a monthly basis between April 2011 and January 2012 for the observation of temporal patterns. The optical properties of DOM and biomass and molecular weight measurements were used to observe these variations. Results demonstrate two peaks in the DOM cycle of 2011, the first in early summer and the second in early fall. Observed differences are attributed to the drought conditions, the Las Conchas fire and the rainstorm events that followed the fire.