Paper No. 6
Presentation Time: 10:00 AM


BERGSTROM, Robert M.1, RHOADES, Charles C.2, MELZER-DRINNEN, Suellen1, BORCH, Thomas3, HUBBARD, Robert4, ELDER, Kelly2 and KELLY, E.F.5, (1)Colorado State University, Department of Soil and Crop Sciences, 307 University Ave, Plant Sciences C127, Fort Collins, CO 80523, (2)US Forest Service, Rocky Mountain Research Station, 240 West Prospect, Fort Collins, CO 80526, (3)Dept of Soil and Crop Sciences, Colorado State University, Fort Collins, CO 80523-1170, (4)Rocky Mountain Research Station, US Forest Service, 240 West Prospect, Fort Collins, CO 80526, (5)Soil and Crop Sciences, Colorado State University, Ft Collins, CO 80523,

The ability to ascertain the coupling of hydrological and pedological systems relies on our ability to quantify the distribution of elements and rates of mineral weathering and soil formation at hilllslope and landscape scales. This is a fundamental challenge to understanding the complex nature of biogeochemical cycling in complex terrain and mountainous areas. We utilized detailed pedological investigations and a constituent chemical mass balance approach to evaluate how topography influences the distribution of elements and weathering rates along catenas in high elevation catchments at the Fraser Experimental Forest (FEF), in the Colorado Rockies. The relative elemental gains and/or losses experienced during pedogenesis along catenary sequences were quantified. We assessed the relative importance of atmospheric and weathering inputs in this mountainous ecosystem and identified key landscape elements that act as “biological buffers” in these complex high elevation watersheds.

In general, soils located on mountain ridges gained volume and mass during pedogenesis as compared to the soils original parent material. 75% of all mountain ridge sites gained Ca. These data suggest that atmospheric deposition may play a significant role in the development of soils in these landscape positions. The majority of soils (88%) along side slopes experienced losses with respect to Ca and K. Soils along valley bottoms had gains of major soil nutrients such as Ca, K, and P. Organic matter rich soils, which occupy the lower and wetter portions of catenary sequences, contain a large reservoir of mobilized nutrients and act as biological buffers for nutrient delivery to tributaries and main stream channels. The distribution of elements along soil catenas and mineralogical alterations suggest that soils at FEF are subjected to substantial nutrient inputs from atmospheric deposition and that the coupling of hydrologic and biogeochemical cycles are conditioned by biological and pedological processes in key landscape elements of watersheds.