presented by Dr. Cliff Dahm (Department of Biology, University of New Mexico)

Abstract:  Our interdisciplinary research team has deployed continuous measuring in situ sensors throughout the year to study ecosystem production and respiration and nutrient dynamics in a high elevation mountain stream in the Jemez Mountains of New Mexico. Multi-year deployment has facilitated studies of ecosystem production, respiration, and nutrient availability and uptake under 1) variable spring snowmelt conditions, 2) strong and weak summer monsoon precipitation, and 3) before and after a major catastrophic fire in the catchment. Strong snowmelt and monsoon conditions reduce primary production and ecosystem respiration rates. Weak snowmelt conditions and weak or delayed summer monsoons produce higher rates of primary production and ecosystem respiration by well-developed biofilms and aquatic macrophytes within the stream. Strong diurnal fluctuations in nitrate and phosphate accompany high rates of primary production and ecosystem respiration. Catastrophic fire in the catchment in late June and early July of 2011 has dramatically altered both nutrient concentrations and ecosystem processes after precipitation events. Phosphate and nitrate increases, turbidity peaks, dissolved oxygen and pH sags, and conductivity increases have all been byproducts of the major fire (Las Conchas) within the catchment and in the Rio Grande.