Soil Organic Carbons Storage along a Climatic Gradient in Aspen Ecosystems of Northern Utah

Encroachment of aspen (Populus tremuloides) by conifers in the Intermountain West is considered to have a negative impact on soil functions and carbon (C) storage. Little is known about C storage in aspen soils in the Intermountain West. The objective of this study, located at the Deseret Land and Livestock in Northeastern Utah, is to estimate soil C pools under aspen and to evaluate how soil C is influenced by elevation, aspect and soil microclimate. Soil samples were taken to a depth of 40 cm at 10-cm increments at a total of 34 sampling points along N-S, E, and W transects in a subcatchment, and total soil C at each location was calculated from Leco C, bulk density, soil depth and gravel content. ECH20 soil moisture probes and Onset Tidbit temperature data loggers were installed at a subset of sites along the 4 transects. Total C content between 0-40 cm was on average 110.3 Mg/ha, but was spatially very variable, ranging from a low of 96.4 Mg/ha (N-facing) to a high of 140.7 Mg/ha (S-facing). In general, soil C content differed among transects as follows S\u3eE\u3e N~W. There was no consistent pattern with slope position. Soil moisture (SM) and temperature (ST) regime differed among the transects: following snowmelt in early summer, SM was higher in N-facing (546 mV, CV=6%) than in S-facing slopes; by September, SM was not different between transects (400mv, CV=1%). The ST regime on the S-facing transect was more variable (-4.1 min to 35oC max) and generally warmer than in the N, E and W facing transects. We are currently analyzing the role of soil microclimate and vegetation cover as drivers of C storage in the aspen