The Controls and Sources of Dissolved Organic Carbon in Intermittent Headwaters Streams in Gibson Jack Creek

Water Extractable organic Carbon (WEOC) accounts for the availability of dissolved organic carbon (DOC) from soil organic matter/carbon (SOM/SOC) that can leach into stream headwater ecosystems. The availability and controls of DOC in the intermittent streams are poorly characterized. Previous studies have shown that DOC concentration vary along in intermittent streams but little research has been performed on the availability and controls of WEOC. To understand controls and availability of DOC in intermittent streams, we examined how soil organic matter and pH affects the availability of WEOC in different habitats link to streams. Specifically, we dug soil pits to 1m or refusal from 4 different habitats within the Gibson Jack watershed in southeastern Idaho and sampled soils to analyze them for availability of DOC and sets of filtrations using a 40mm Whatman filter and 0.45 um AQUA Whatman filter, filtrate was analyzed in Shimadzu TOC analyzer. SOC was measured on a elemental analyzer on the front end of a mass spectrometer. We hypothesized that SOC would decrease with depth and correlated positively with DOC concentration whereas pH would be positively correlated to WEOC and vary with soil depth in different habitats. Moreover, we predicted low pH and higher SOM in the riparian habitat would account for more DOC concentration as WEOC than the sagebrush, deciduous, and conifer habitat. Results showed a large variation of WEOC with vegetation type and depth. Riparian habitat had more WEOC with depth than other habitats. Sagebrush had higher pH and lower SOC with depth compared to other habitats. SOC was highly correlated with WEOC and explained more variation (87%) in WEOC than pH. Understanding the distribution of SOC is important to understand the controls of DOC sources