Soil Hydrology in Lodgepole Pine Ecosystems in Southeastern Wyoming

Abstract

AbstractThe rates and pathways of water movement through the soil were examined in several lodgepole pine (Pinus contorta ssp. latifolia) forests in southeastern Wyoming to improve our understanding of the dynamics of solute flux in forest ecosystems. We employed internal drainage and tracer pulse methods to determine hydraulic conductivity, and we examined snowmelt infiltration and drainage water chemistry on contrasting soils supporting lodgepole pine forests. Saturated hydraulic conductivity (Ko) values were lognormally distributed for 27 plots at each of two sites examined. The median value was significantly higher at a site on a gravelly, loamy‐sand (median Ko = 1.20 cm/h) than on a bouldery, sandy‐loam (Ko = 0.49). At these sites the high range in both Ko values and in the transit time for a Cl‐ pulse were suggestive of highly variable water flow pathways through the soil. Early in the spring snowmelt period much of the infiltrating water circumvented the soil matrix, probably flowing around entrapped air pockets and through macropores. Although large systematic differences in chemistry were not observed between soil solutions collected with tension and tensionless lysimeters, saturated flow (collected as drips from the ceiling of soil tunnels) contained about three times lower cation concentrations than the lysimeter solutions. To obtain more accurate estimates of nutrient leaching from the tree rooting zone better quantification of the chemistry of percolating soil water is needed.